API Calibration Facility for Nuclear Logs

WILLIAMB. BELKNAP,~: JOHNT. DEW AN,^ C. V. KIRKPATRICK,~

WILLIAME. M O T T , A.
~ J. PEARSON,**AND W. R. RABSON***

ABSTRACT

The work of the A P I National Subcommittee on f a c ~ h t y ,and a recommended standard procedure f o r

Revis~onof RP 53 Recom.~ne7~cletl P r c ~ c t ~ f&o r Stccncle~rcl presenting cal~bratlondata. D e t a ~ l e ddes~giiand eiigl-
Cal.lr',rcctzo7~and For?)?.for Nftcleccr Logs IS explained neering d a t a on t h e calibration f a c ~ l i t ya r e presented.
111 tliis papel Accoinplishnieiits of tliis Subcommittee The development of standard nuclear log units of
~ n c l u d ea revlsed recommended standard nuclear log measurement and calibiation of-logs in these units is
lieadilig and form, a defin~tionof standard gamma-ray a s~giiificantforward step in this field. I t \vil1 enable
and neutlon log units fol m e a s u n n g radiatlon, t h e petroleum engineers and g e o l o ~ s t sto compare dliectly
tles~gii and coiist~uctloii of a nuclear log calibration nuclear logs r u n by different l o g g ~ n gcompanles

I. INTRODUCTION hour. completely l a c k ~ n gis a common approach w h ~ c h

can be used by all involved to relate these units t o each
Nuclear logglng methods wele introcluced commei- other a s well a s to the phys~calproperties of the for-
cially to the petroleum industry about 20 years ago. mation being measured. There have been attempts by
Their utilizat~on has steadily increased u n t ~ ltoday a t some of the operating companies to ~ n t e r - r e l a t eunits
least one nuclear log I S run 111 nearly every well d r ~ l l e d . through the use of field data, but a s yet a n uil-to-date
Table 1 is presented to slio\v the number of nuclear logs set of factors f o r converting gamma-I a y readmgs from
l u n d u l ~ n grecent yeais I n splte of this wide use, those one company's log t o t h a t of another company h a s not
pelsons usillg nucleai logs have found it a very com- been publ~shed By and large, the work of developing
phcated - lf not a t t ~ m e simposs~ble- task to make conversion factors has proved to be time-consum~ng,
coniparlsons between logs r u n by the v a n o u s logg~iig expensive, and usually of temporary value
companies l~ecauseof the absence of standardrzation.
T h ~ slack of s t a n d a r d ~ z a t ~ o IS
n demonstrated by t h e A s i m ~ l a rploblem exists with present-day neutron
numelous dlffereiit u n ~ t sused f o r measuring radiation, logs The suivey showed S I X different units being used
d~fferentprocedures f o r checklng and calibrating logging for neutron measurement by seven logglng companles
~ n s t r u m e n t s ,d~fferentlog headrngs, and d ~ f f e r e n tscales These ~ n c l u d ethe following counts/second, inches per
used by the logging companies. The exlstlng differences standard unit, counts per mmute, environmental u n ~ t s ,
In log nieasureinents have severely l ~ m ~ t et hd e use of ~ n c h e sper 100 standard units, and standard counts per
nuclear logs In areal studies and critical correlation second
( The lack of standard~zationand need f o r calibration
The response of t h e present-day gamma-ray logs is of nuclear logs resulted in t h e Steerlng Comm~tteeon
calibrated in a u n ~ twhich, so f a r a s t h e petroleum Product~on Practice of the D ~ v ~ s ~ oofi i Production, '

~ n d u s t r ya s a whole 1s concerned, is ideiit~fiableonly w ~ t h American Petroleum Institute, a p p o ~ n t i n ga national

the l o g g ~ n gcompany making the log A survey of eight subcomm~tteea In June, 1956, to ievle\v RP 35 Rec-
logging companies offerlng nuclear logs showed seven ol,fnlemdetE Prcictfce for Stc~)lclurd Raclior~ct~uityLog
d~fferentunits b e ~ i i gused f o r measuring gamma radia- F o r ~ ,( T e i i t a t ~ v e )I' This Subcommittee was ~iistlucted
t ~ o n .Some of these u n ~ t shave identical names, b u t a r e to accumulate all available suggest~onsf o r revlsion of
not the same unit of measure since t h e logging com- R P 55. and to develop a standard practice t h a t would
panies use d ~ f f e r e n tc a l ~ b r a t l n gtechniques. I n current create unifornnty and allow d ~ r e c tcomparison of radlo-
usage a r e the following diverse units of gamma-ray actlve logs I t w a s selected to provlde representation
rneasurement. counts/mlnute, connts/second, radiatlon from both 011 and logging companies from throughout
units, inicrogralns rad-eq./ton, and ni~croloentgens/ the United States
The Subcommittee investrgated t h e e x ~ s t ~ ncoiid~tions g
*Phllllps Petroleum Company. Bartlesvllle, Okla of s t a n d a r d i z a t ~ o nof log h e a d ~ n g s , forms, u n ~ t sf o r
iSchlumberger WeU Surveying Corp , Houston. Texas
Un~versltyof Houston, Houston, Texas
iGulf Research and Development Co P~ttsburgh,Pa
**The Atlantlc Refinlng C o , Dallas, Texas
aSee Appendlx A for membership
bThe first ed~tlonof R P 33 was adopted and publ~shed In November
***Pan Geo Atlas Corp , Houston, Texas 1948.
290 BELKNAP, DEWAN,KIRKPATRICK,MOTT, P E A R S O N , AND RABSON

Table 1
Total Nuclear Logging Operations'

Total Nuclear
O p e l a t ~ o n sIn Teims of
Wells Drllled Nucleal Logs Run* Wells Dr~lled,Percent
Outs~de Outslde Outslde
Year U S U S. Total U S. U. S. Total U. S. U. S Total

'Reference; are a t the end of the paper

'Comp~led from data supl~liedby the following compames Blrdwell. Inc. Frontler Perforators, Inc . Creat Lakes Petroleum Serv~ces,Inc , Lane-
Wells Company. McCullough Tool Company. Perforating Guns Atlas Corporation. Ram Guns. Inc . Schlumherger Well Surveying Corporat~on.
.
Weles, Inc The Western Conlpany. Worth Well Surveys. Inc

measuling l a c l ~ a t ~ o nand , c a l ~ b i a t ~ oprocedures

n Early F ~ n a l l y ,poss~blef u t u ~ euses of the faclllty a s well a s
In thls study it \\.as agreed t h a t development of con- ~ t value
s t o the Unlverslty a r e discussed
version factors between vailous l o g g ~ n g compan~es'
gamma-ray and neutron logs would not be a s a t ~ s f a c t o l y 11. FACTORS INVOLVED IN GAMMA-RAY
s o l u t ~ o nto the problem I t was recognized t h a t f u t u i e STANDARL)IZATION
developments would greatly Increase the ~nipoltance Gamma-ray L o g g ~ n gPrinciples
of neutron logglng a n d i n t e n s ~ f ythe need fol a solutlon The alrn of gamma-ray logglng a s currently practiced
to the standardization problem. IS to obtaln a measure of the total number of gamma
111 the original RP :'3, gamma-ray and neutron logs l a y s emltted per second by a unit welght of f o l m a t ~ o n
weie classed a s radloactlv~ty logs The Subcomni~ttee lock The gamma l a d ~ a t l o nof natural mateilals 1s due
changed thls tltle to nuclear logs because the term almost e n t ~ l e l yto the decay products of uranium, the
"nuclear" IS more descrlptlve decay products of tlior~uni,and the rad~oactlve soto ope
Leadlng to the objective of standartl~zlngnuclear logs, of potass~uni Hence,- t h e gamma-lay actlvlty, A , of a
t h e Subcommittee acconlpllshed the follownig secl~mentalyrock can be cons~dereda h n e a i function of
1 Designed a standaid log heading and folm the amounts of uranluni, t h o l ~ u m , and potasslum
2. Established a standard A P I Gamma-Ray U n ~ t . piesent, 1.e .
3 Established a standaid A P I Neutron U n ~ t .
4. Des~gnedand promoted construction of a callbra-
+
A = AuWu ATILWTILAKWK + (1)
I.l'he~eu~Au, ATJL,and A,- represellt t h e spec~ficactlvl-
t ~ o nfacllity fol nucleai logs tles (gamma r a y s per second o r ~ g l n a t l n ge ~ t h e rd ~ r e c t l y
5 Developed a standard c a l ~ b r a t l o npiocedure 01 ~ n d l i e c t l yfrom a g r a m of the element) and I,i'u, li'TJ,.
These accompl~shmentsresulted in pubhcat~onIn Sep- and IYK the corresponding fractional abundances of
tember 1959 of the 2nd ed~tlonof RP 3.3 Recom?laended uianlum, thonum, and potass~um,respect~vely.F o r all
Prrictlce for St4~7tda~d Cnl16ri~tz07~ (~71dForm for Nziclecir practical purposes In well logglng, ~t can be assumed
Logs The r e v ~ s e d edltlon contalns t h e lecommended t h a t t h e source mateilals a r e u n ~ f o i n i l y d ~ s t r ~ b u t e d
form f o r nuclear logs and d e t a ~ l s of procedures to throughout t h e and the uranluni and t h o l ~ u m
be followed f o r callbratlng nuclear l o g g ~ n g tools in serles (Tables 2 and 3 ) a r e 111 rad~oactlveeclull~br~um
standard A P I unlts A s defined, A U IS t h e total number of gamma rays
The purpose of thls paper 1s to plesent In detall t h e e m ~ t t e dper second by a gram of ulanluni in e q u l l ~ b r ~ u m
technical aspects of planning, constluct~ng,and operat- wlth ~ t decays ploducts I t s value I S obtalned by sum-
Ing the cal~bratlon f a c ~ l l t y2 The factors involved ~n mlng t h e contr~butlonsfrom each of the radlonucl~des
arrlvlng a t sultable s t a n d a i d ~ z ~ nm g e d ~ af o r nucleal In t h e ulanium serles, t h e presence of t h e membels of
logs, viz , gamma-ray and neutron c a l ~ b i a t ~ oplts, n are the actlnluni serles belng ~ g n o r e dbecause the parent,
outhned. Detalls of the s t u d ~ e si e q u ~ r e dto d e t e l m ~ n e Us" IS only 0 72 pelcent abundant. Uslng the most
t h e slzes of plts needed and materials used t h e i e ~ na r e recent d a t a available and summlng only photons h a v ~ n g
presented Constluct~onof the f a c l l ~ t yIS descr~bedto energles greater than 100 kev,* we find
~ l l u s t r a t e t h e many problems ~nvolved In selecting, A U = 2.8 X 104 pl~otonslsec-grwnU .
measuslng, processing, and placlng m a t e i ~ a l s 111 the
plts The various tests, ~ n c l u d ~ ncore g analyses, spectral I11 11ke manner, s u m m a t ~ o nof the gamma r a y s e ~ n ~ t t e d
analyses, chemlcal analyses, log checks, etc a r e pre- by t h e elements of the thorlum serles ylelds
sented. The operation, financing, callbrat~onprocedure, A,,, = 1.0 x l o 4 pl~oto?zslsec-gra?~Th
conversion from e x l s t ~ n gu n ~ t to s A P I ulnts, and records
'Phohns of energ! lrss than 100 kev are strongly absorbed by the
n ~ a ~ n t a ~ nbye dt h e U n ~ v e r s l t yof Houston a r e described. formal102 and the p..essure houslng of the l o g g ~ n gtool
 A P I CALIBRATION
FACILITY
FOR NUCLEAR
LOGS 291

Table 2.
The Uranium Series3

Mode o f
Nuclide Disintegration Half L l f e Sequence

238 9
UI a 4.51 x 10 y r
9 2'
gOTh234 p 24.1 d
uX1
234m 1 . 1 8 rnin
uX2 91Pa B , IT,
234
uz 9 lPa B 6.66 h r
2 34 5
UII a 2.48 x 10 yr
9 2'
4
I0 Th230 , a 8.0 x 1 0 yr
90
226
Ra a 1620 y r
88Ra
222 d
Rn a 3.82
86Em
218
Ra A 84" a, a 3 . 0 5 min

R~A' 85AL218 a, p -2 sec

218
RaA" a 1.3 sec
86Em
RaB 82Pb214 p 26.8 min

RaC 83Bi214 a,p 1 9 . 7 min

214 a 1.6 x 1 0 - ~ s e c
R~C' 8 4"
RaCgL 81T1210 B 1 . 3 2 min

RaD 82Pb210 B 19.4 y r

210 5.01 d
RaE 83Bi a, I3
210 a 138.4 d
Ra F 84'O
RaE' 81T1206 I3 4 . 2 min

RaG 82Pb206 Stable --

Natural potassium h a s a much lower speclfic actlvlty, to date nearly 80 gamma-ray 11nes have been observed
VIZ , ~n the spectiurn of the former, 60 in t h e latter.*
A , = 3.4 pJz.oto~tslsec-yrrtm K, Although the data on the energles and intensltles of
many of these a r e to some extent uncertain, ~t is
than elther uianiunl or thorium but is of approximately
belleved t h a t the aforementioned values of A , and ATh
equal importance In its contiibution to the gamma-ray
and the general features of the energy dlstrlbution
act~vltiesof most sed~mentaly rocks because ~t is a
curves a s outhned ln Table 5, p 294, a r e sufficiently
much more abundant element.
accurate f o r present-day logging studies.
Some idea of the complex~tyof the emisslon properties 'Theergrgles and l n t e n s ~ t ~ eofs the most Intense lines In the spectra
of the naturally occurring rad~onuclldesare l~stedIn Table 4 , p 293
of the U23Rand Th2" familles follows from the f a c t t h a t Note that the gamma rays ernltted by K4O are monoenergetlc.
 Table 3
The Thorium Series3
a

Mode o f
Nuclide Disintegration Half L i f e Sequence
--
232
Th
goTh a 1.42 x l0l0yr -
MsThl
228
6.7
a
88Ra B yr AL
228 B
MsTh2 B 6.13 hr
8 gAC
RdTh ~h~~~ a! 1.91 yr -
I3
224
3.64 d
a
ThX a! A-SL
88Ra
220 a
Tn a 51.5 sec AL
86Em
216 a
ThA 84"
a 0.16 sec JL

ThB 82Pb212 B 10.6 hr a

JL

ThC 83Bi212 alp 60.5 min V

64.6%
212 35.4%
ThCr a 0.30 psec
8 4 P ~ a
ThC" 81~1208 B 3 . 1 0 min AL a
.ThD 82Pb208 Stable -- B v

The baslc characteristics of the 3 naturally occurring 3. Character~stlcs of the detector and the counting
source m a t e r ~ a l sa r e summar~zedIn Table 6, 11. 294. The system
radium portion of the uranlum series 1s included a s a 4. Posltion of the detector ~n the borehole
separate item f o r reference purposes. 5 Density of the f l u ~ d111 the borehole
It is impoltant to observe t h a t the response of the 6. Dlanletel of the borehole
natural gamma-ray log does not necessarily p r o v ~ d ea 7. Thickness and denslty of the caslng and cement
d ~ r e c measuie
t of formatlon a c t ~ v i t yI n fact, the nature 8 Bulk density of the foirnation
of the problem 1s such that, In some condltlons, the and in some cases 011
q u a n t ~ t i e srecorded on a log cannot even be qual~tatively 9. Relative concentrat~onsof the radioactive mate-
related to gamma-ray emission without the a ~ dof rials ( U , Th, and K ) In the formatlon.
calibration data and departure curves T h ~ shappens, The physical pi lnclples nlvolved here can perhaps best
of course, because the magnitude of the signal produced be understood if the contrlbut~onto the response, d I ,
a t the output of the detection system 1s ~nfluencedby made by the radioactive materlal contamed In a n element
a combination of factors. To elucidate, the response of of volunle dl', havlng denslty p , located a t a dlstance r
a detect01 statlonary In a borehole oppos~tea glven from the center of the sens~tlbevolume of the detector
formation will depend upon: 1s expressed In the general form (for the case of a
1. Specific activity of the formatlon (gamma rays/ pulse-type detector) :
sec-gm) d l = .4~Pfi)O(r)pdIT (2)
2 Speclfic a c t ~ v ~ t i eofs borehole flu~d,caslng, and Wl~ere~n:1 . sA the number of gamma rays emitted per
cement second per gram of rock; O(r), the fraction emltted in
 API CALIBRATION
FACILITY
FOR NUCLEAR
LOGS 233

Table 4
Gamma-ray Lines* in the Spectra of the Important
Naturally Occurring Radionuclides3
--
- -
-- _I___- -- -_..A

greater than 0 05 photons per dls~ntegrat~on

* w ~ t n~ntens~tres and enera~esgreater than 100 kev.

the d ~ r e c t ~ oofn t h e sensitive volume of the detector, Expressed alternat~vely,E 1s the p l o b a b i l ~ t yt h a t a

p(r), a factor to corlect f o r t h e absorption and scat- gamma r a y ~ n c l d e n t on t h e detector w ~ l l produce a
terlng of gamma r a y s In the reglon between the element count The c h a r a c t e r i s t ~ c sof the counting system (e.g ,
dV and the detector, and E, t h e effic~encyof the detector the setting of t h e d ~ s c i ~ m l n a t used
o r wlth a sclntlllation
f o r gamma rays, I.e., the f r a c t ~ o nof those incldent on counter) and t h e characteristics of t h e detector deter-
the detector t h a t actually contributes t o the response. mine ~ t values In a n y glven s l t u a t ~ o nThe three p r ~ n c ~ p a l
The factor P accounts f o r the f a c t t h a t the number classes of gamma-ray detectors currently In use a r e
of gamma rays w h ~ c hreach t h e detector ( A p f l p d V ) lon~zatlonchambers, Ge~ger-Mullertubes, and sclntllla-
IS strongly ~nfluencedby t h e environment In w h ~ c ht h e tlon counters Even w ~ t h n la given class, ~ n d ~ v l d u a l
source and the detector a r e s ~ t u a t e d I t s value v a n e s ~ n s t r u m e n t scan have wldely different energy-response
w ~ t hthe types of mateilals present, the dlstance ,I., and characteristics unless they a r e bullt to exactly t h e same
t h e energy of the gamma r a d ~ a t l o n specifications. T h a t IS, In addltion to b e ~ n gnot equally
294 BELKNAP,DEWAN,KIRKPATKICK,
MOTT,PEARSON,
A N D RABSON

Table 5
Spectral Composition of the Gamma Rays* Emitted by the Uranium Series,
the Thorium Series, and Potassium'
U r a l i ~ u n iS e n e s
Number of
Photons per
I 1 T h o r ~ u n lSeries
Number of
Photons' per
I
-

Energy D ~ s ~ n t e g r a t ~ o n Relative D ~ s i n t e g r a t ~ o n Relatlve Number of Relat~ve

Interval, 111 E q u ~ l l b r ~ u m Intensity, in E q u ~ l ~ b r ~ u mIntensity, Photons per Intensity,
Mev Mixture Percent Mixture Percent Disintegration Percent
0.1 - 0.3
0.3 - 0 5
0 5 - 0.7
0.7 - 0 9
09-11
1 1- 1.3
13-15
1 5 - 1.7
1.7 - 1.9
1.9 - 2.1
2.1 - 2 3
2 3 - 2.5
25-27

'Includ~ng l ~ n e su ~ t henergles greater than 100 kev

Table 6
Characteristics of the Three Naturally Occurring Source Materials'

Number of Number of - Number of

Dls~ntegratonI Sec-Gm Photons/D~s~ntegrat~on Photons1Sec-Gm Mean Photon
Element of Element In E q u ~ l ~ b r l uM
m~xture* of Element* Energy, Mev*
u(+)
Thi+)
1.23 x lo4
4 02 x 103
2.24
2.51
I 28
10
x lo4
x 104
0.80
0 93
-

K 31.3 0 11 1.46
Ra(+) 3.63 X 1010 2.20 80 X loi0 0 81
*Photons w ~ : henergles less than 100 kev not Included
( + )Ser~esIn equ~l~brlum.

s e n s ~ t i v eto gamma r a y s of all energles, the manner In p will now v a r y only w ~ t hItems 4 to 8, E, with Item 3
whlch the efficiency v a n e s with energy can d ~ f f e rfrom
one type of counter t o the next Calibration and Standardization of Gamma-ray Logs
Thus, In p ~ l n c i p l eP IS affected by v a r ~ a t ~ o nins the I t IS apparent from the "Introduct~on" t h a t many of
l a s t six items l ~ s t e dpreviously. The last seven Items w ~ l l the d ~ f f i c u l t ~ emherent
s in gamma-ray logging would be
affect the energy d ~ s t r ~ b u t i oof n gamma rays w h ~ c h , e l ~ m ~ n a t eifd a common u n ~ of t measurement defined In
in t u i n , affects the spec~ficvalue of E . The descript~onIS telnls of a standard source of ganima radiation (which
s ~ m p l ~ f i econsiderably
d however, ~f we assume, In accord- could be used to c a l ~ b r a t eeach type of gamma-ray
ance wlth a common practice whlch may or may not be logging tool) were adopted by t h e servlce companies
well-grounded, t h a t under the c o n d ~ t ~ o n normally s Once the Subcomm~tteeagreed t h a t t111s approach t o
encounterecl In well logging s t a n d a r d i z a t ~ o nwas practicable and would not 11lfr1ng.e
a. t h e energy spectrum of the gamma r a y s e m ~ t t e d upon t h e r ~ g h t sof ~ n d ~ v ~ dcompanies,
ual t h e h a w pioh-
by the formation does not v a r y much from one lems of namlng and defining the standard unit of log
formatlon to another (l.e., w ~ t ht h e r e l a t ~ v econ- response were attacked E x ~ s t ~ nunits g wele first con-
centrations of U, Th, and K ) , and s ~ d e r e d .Some of these had desirable characteristics b u t
h. t h e spectrum ~ n c ~ d e on n t the detector is not shifted none w a s completely d e s c r ~ p t ~ vofe the ganinla-ray enils-
s ~ g n ~ f i c a n tby
l y changes In horehole and formation slon p r o p e r t ~ e sof the formatlon Because of t h ~ and s the
condit~ons. d~fficultyof achlevnlg agreement between the competi-
 FA(:ILITY
APT CALIBR.ATION FOR NUCLEAR
LOGS 295

tive l o g ~ l n gcompanies on a n e s ~ s t ~ nu gn ~ t a, new t e n n nuclear c o l l ~ s ~ o nusn t ~ lthey a r e in thermal e q u ~ l ~ b i i u i n

"API Ganinla-Ray Unit" was apploved by the Sub- w ~ t hthe moderating medluni, and then d ~ f f u s eunt11
conlln~ttee they a r e absorbed by t h e f o r m a t ~ o nnucle~.A steadp-
As ~ n d ~ c a t eeda l l ~ e r ,In gamma-lay l o g g ~ n gone I S state cond~tron is reached when the total number of
only co~icernetlw ~ t hthe gamma l a y s eni~ttetlby K40, n e u t ~ o n sabsorbed per second equals the number e m ~ t t e d
U"s, T h " h n d the decay products of the latter t\vo per second
I t mas reasonable therefore t h a t t h e Subcomm~ttee I n the steady state, neutrons of all energles a r e
defined the A P I u n ~ tm terms of the magnitude of t h e d ~ s t r ~ b u t e111
d space about the source F o r a n y glven
response produced by a n estended m e d ~ u mc o n t a ~ n ~ nag set of bolehole and f o l m a t ~ o nc o n d ~ t ~ o n st ,h ~ sclout1
m ~ s t u r eof the three naturally occurrmg r a d ~ o a c t ~ v e of neutrons will have the follow~nggeneral features:
source materials F o r one thing, w ~ t hlogs calibrated a The total neutron density ( ~ . e ,t h e n~ilnber of
111 such units, effects caused by energy-dependent factors neutrons per unit volume), a s well a s t h e d e n s ~ t yof
(such a s the d ~ f f e r e n energy-iesponse
t characterist~csof neutlons w h ~ c hhave been slowed down to some energy
the various logging systems) w ~ l lbe n ~ ~ n ~ m i z ~f e d in
, E , \\rill be a decleasmg f u n c t ~ o nof the distance from
f a c t they do play a n ~ m p o l t a n tpart. the source.
Although some c o ~ i s i d e r a t ~ o\\,as n glven to the p o s s ~ - h Neutrons of energy E will be distributed, on the
h ~ l ~ tofy u s ~ n ga geolog~cal f o ~ m a t ~ oans a primaly average, closer to the source than those of some lower
standard, the unanimous c h o ~ c eof t h e Subconlm~ttee energy E'.
was a c a l ~ b i a t ~ opit i i because ~t appeared to meet t h e c. The spatial d~stributionof thelmal neutrons will
b a s ~ crequirement of bemg both practical and pelma- always be broader t h a n t h a t of ileutrons of energles
nent The p ~ t(see S e c t ~ o nI V h e r e ~ n ) would he com- just above thermal
p r ~ s e t lof two zones - one of very low r a d ~ o a c t ~ v ~ t y , As f o r the effect of the i n t r ~ n s i cp r o p e r t ~ e s of a
the othei h a v ~ n gessent~allythe same relative concen- f o r m a t ~ o non t h e s ~ a t ~ da ~l s t n b u t i o n .we observe t h a t
t r a t ~ o n s of uranium, t h o r ~ u m , and potasslum a s a n in slo\ving down to a low energy E , neutrons (on t h e
average shale, but a p p r o s ~ n i a t e l ytwice the total a c t ~ v - aveiage) travel f a r t h e r f i o m t h e source when the
~ t y Both
. zones would be used f o r c a h b r a t ~ n gpurposes, hydrogen concentrat~on is low than \vl~en ~t is high
w ~ t hone A P I Gamma-Ray U n ~ defined t a s 11200 of the In other wolds, a s t h e hydrogen content of the rock
d~fference111 t h e lo? deflections produced by the two Increases, the neutrons a r e slowed down more effectively
levels of radiation. and the distribut~onis narrowed. To ~ l l u s t r a t et h ~ swe
Espiessed in terms of equation (2), a f t e r ~ n t e - c o n s ~ d e rtwo formations, one having n, hydrogen atouis
g r a t ~ n g ,the c a l ~ b r a t ~ opn ~ w
t ~ l lglve: per u n ~ tvolume, the other 1t2, where 7 7 1 > ?L?. If t h e
I , - I2 = A l ~ , X-lA 2 ~ , k 2 neutron deiisit~es 111 these f o r m a t ~ o n sa r e q , ( E ) and
= ,000 API Gn?n~nc~-Rny U7tzts (3) q 2 ( E ) , respectively, and all other factors a r e constant,
W l l e r e l ? ~k l and k, a r e constants of p r o p o r t ~ o n a l ~ t y then, a t t h e source p o s ~ t ~ o qn ,l ( E ) > q 2 ( E ) . However,
Therefole, if energy-dependent effects a r e ~ g n o r e d ,the upon movmg away from t h e source a p o ~ n tI S reached
e q u a t ~ o nf o r the iesponse of every c a l ~ h r a t e dtool In a (the crossover p o ~ n t where q , = q 2 ) beyond wh~cli
f o r m a t ~ o nof spec~fica c t i v ~ t y.4 w11l be. q1(E) < rp(E).
I = [ZOO A k I ( k , A , - li2A2)] A generalizat~onof the foregoing 1s that, regardless
( A P I Gamma-Ray U n ~ t s ) (4) of the energy of the neutrons under considerat~on,a
I t IS e v ~ d e n tt h a t the response I 1s independent of tool d ~ s t a n c e can be found a f t e r whrcli neutron density
type and other instrumental factors and thus sat~sfies always dimin~shesw ~ t hhydrogen content. We need to
the cond~tlonsf o r s t a n d a r d ~ z a t ~ o n remember, however, t h a t the exact m a g n ~ t u d eof the
reduct~on IS a f u n c t ~ o nof neutron energy; I e , a t a
111. FACTORS INVOLVED I N NEUTRON LOG glven d ~ s t a n c efrom t h e source, the thermal and epl-
STANDARDIZATION thermal densities, f o r esample, w ~ l lnot change a t the
Neutron L o g g ~ n gPrinciples same r a t e with hydrogen The detectors of all presently
Altliougl~ t h ~ spapel 1s not intended a s a nuclear a v a ~ l a b l e neutron logging devices a r e located In the
logging primer, ~t I S necessary to set forth c e r t a ~ n reglon where the neutron density decreases a s t h e
~ u d ~ m e n t a i py ~ ~ n c ~ p l111
e s order to make clear the hydrogen concentrat~onincreases
reasoning b e h ~ n dsome of the Subcommittee's d e c ~ s ~ o n s . Of course, elements other t h a n hydrogen can influence
Coiisequently, 111 t h ~ ssect~on,only those t o p ~ c sd ~ r e c t l y the manner in w h ~ c hneutrons of a glveil energy a r e
related t o the c a l ~ b l a t l o nand s t a n d a i d i z a t ~ o nof neutron d ~ s t r ~ b u t eabout
d a source. F o r example, a t low hydro-
logs w ~ l lbe d~scussed and then a s br~eflya s poss~ble gen concentrat~ons,where the s l o w ~ n gdown of f a s t
F o r a comprehens~vetreatment of the phvs~cal prin- neutrons IS no longer d o m ~ n a t e dby hydrogen, effects
ciples of neutlon l o g g ~ n g ,the readel IS refelred to the caused by d~fferencesin the nlajor elements present 111
work of T i t t n i a i ~ . ~ t h e rock matrices become significant. F u r t h e r , t h e
I n the sequence of events w h ~ c l i character~zes the diffusion of thermal neutrons can be a p p r e c ~ a h l yaffected
neutlon l o g g ~ n g method, energetic neutrons from a by small concentrations of elements w h ~ c ha r e strong
source 111 the logging sonde enter the f o r m a t ~ o n ,lose neutron absorbers (e.g., chlorine) and, under c e r t a ~ n
energy (slow down) through elastic and i n e l a s t ~ c cond~tions, by t h e major elenients in the formation.
 , MOTT,PEARSON,A N D RABSON

Reference should also he made to the f a c t t h a t t h e s l ~ g h t l ydifferent elemental composlt~on Under some
energy, E,, of t h e source neutrons plays a role In conditions, then, t h e response curves of the neutron-
determlnlng the character~stlcs of the spatial d ~ s t r l - gamma a n d neutron-thermal neutron logs niay be t h e
h u t ~ o n of neutlons All other factors belng equal, same, whereas under others there may he major
changes In E , can alter t h e relationship hetween neutron d~fferences.
d e n s ~ t yand hydiogen content. b. Soztrce-detector S p n c ~ n g .The a h l l ~ t yof a neutron
The niechan~sms u n d e r l y ~ n g the neutron l o g g ~ n g log, regardless of type, to ieflect changes m t h e hydrogen
niethod a r e such t h a t the f u n c t ~ o n a l r e l a t ~ o n s h ~ p content of a formatlon IS dlrectly related to the spaclng
hetween hydrogen concentrat~onand log response can between the source a n d the detect01 As the spaclng is
v a r y from one type of logg~rlgsystem to another. I t is Increased (in t h e reglon above crossover), the fractional
thls c h a r a c t e r ~ s t ~ cmore
, t h a n a n y other, which compll- change i n response f o r a u n ~ change t In hydrogen IS also
cates the s t a n d a r d ~ z a t i o nproblem ~ncreased. However - a s was mentioned prev~ously-
The h a s ~ cd~fferencesIn response vs p o r o s ~ t y~ n d e x neutron density always decreases w ~ t ht h e d ~ s t a n c e
of the various logging systems stem from the use of from the source, so t h a t the larger spaclngs a r e char-
d~fferent types of detectors, source-detector spacings, acterlzed hy lower c o u n t ~ n grates and greatei s t a t ~ s t l c a l
and - probably to a niuch lesser extent - types of fluctuat~ons
sources. Each of these factors is discussed briefly Each sei-vlce company selects source-detector spaclngs
following In accordance w ~ t hits own ideas a s to what constitutes
CL. Detector T y p e . Three generlc types of detector a r e the best comproni~sebetween hydrogen resolut~onand
used In commercially a v a ~ l a b l eneutron loggnlg tools. c o u n t ~ n gr a t e f o r its 1)artlcular cond~tions The result
F o r our purposes, we w ~ l l refer to these s ~ n i p l ya s 1s t h a t even tools of t h e same type ( e . g , neutron-

thermal neutron, eplthernial neutron,* and gamma-ray gamma) a r e operated w ~ t hd ~ f f e r e n tspacings and, a s
detectors, ~th e ~ n gunderstood -hut ~ g n o r e d- t h a t not a consequence, can have d ~ f f e r e n tresponse cuives.
all thermal-neutron detectors a r e completely insensl- c. Nezctron Solirces. The neutrons e m ~ t t e d h y the
tive to e p ~ t h e r m a l neutrons a n d l o r gamma rays and sources In present-day neutron logglng tools a l e pro-
converse1y. duced by a nuclear reaction w h ~ c hmay be described
The responses of the first two detectors a r e propor- symbolically a s follows:
tional to the densities of thermal and epithermal .,Be9 + .He4 -+,nl + ,C1" 5.71 Mev.
neutrons, respect~vely, In t h e ~ r ~ m m e d ~ a tvei c i n ~ t ~ e s .
Hence, from the dlscuss~onIn the prevlous sectloll, we A small p a r t of the r e a c t ~ o nenergy (5 71 Mev) is used
see t h a t for a . given set of horehole a d format1011 up In the r e c o ~ lof the C 1 h n c l e u s , all o r p a i t of the
c o n d ~ t ~ o n sa, neutron-thermal neutron and a neutron- remainder may be carrled off by the neution
e p ~ t h e r m a lneutron log can have q u ~ t ed ~ f f e r e nhydrogen
t Sources of t h ~ stype a r e made by mlxlng - o r com-
response curves h l n ~ n gchemically - a n a l p h a - e m ~ t t ~ nr agd ~ o n u c l ~ dsuch
e
A t fiist s ~ g h ~t t appears a s though a sonde c o n t a l n ~ n g a s Raze, Pox0, Ac227, or PuZSY,w ~ t hberyll~um, the
a gamma-ray detector wlll produce a log w ~ t ha response t a ~ g e tmatella1 The neutron y~eltlof a glverl source
veiy s ~ m ~ l ator t h a t of the thermal neutron log. The prlnclpally depends upon the r e l a t ~ v ep r o p o r t ~ o n sof
reasonlng 1s a s follows When thermal neutrons a r e alpha en11tte1 and target m a t e r ~ a lused, the manner of
absorbed by format1011 n u c l e ~ the , excess r e a c t ~ o nenergy mlxlng or conihln~ng,and on the decay p r o p e r t ~ e sof
1s promptly released In the form of gamma r a y s the alpha e m ~ t t e r A p p r o x ~ m a t e y ~ e l d s o b t a ~ n a h l e In
Inasmuch a s t h e number of neutrons absorhed per p r a c t ~ c efrom some of the commollly used alpha-neutron
u n ~ tvolume a t a n y polnt In the formation IS propor- sources a r e listed in Tahle 7.
t ~ o n a lto t h e thermal neutron d e n s ~ t y a t t h a t polnt, An ( a , ? ~source ) always e x l i ~ h ~ at s wrde spectium of
the g a m m a - r a y - e m ~ t t . ~ nnucl~des
g a r e seen to he d ~ s - neutron energles even when the alpha pal-t~clesall have
t i ~ h u t e dabout the source (of neutrons) 111 exactly t h e the same i m t ~ a lenergy. T h ~ IsS hecause: (I., many alpha
same manner a s the thei-mal neutrons Up011 assuming. p a r t ~ c l e slose p a r t of t h e ~ energ!,
r 11g coll~slonprocesses
t h a t few gamma rags c o n t i ~ h u t eto the courit~rigl a t e hefore they ~ n t e r a c twith a h e r y l l ~ u mnucleus; h , t h e
unless they a r e produced very near the detector, one product nucleus 1s somet~mesleft In a n e s c ~ t e ds t a t e 111
1s led to the conclusion t h a t the response of the gamma-
which case the energy of e s c ~ t a t ~ o1s n not a v a ~ l a h l et o
r a y detector 1s proport~onal to the thermal neutron the emitted neutron, and c, t h e recoll energy of t h e
d e n s ~ t yIn ~ t v~clnity.
s product nucleus varies wlth the angle hetween the Incl-
Of course, the fallacy 111 tins reasonlng IS t h a t In dent alpha p a r t ~ c l eand the o u t g o ~ n gneutron I n general,
the neutron capture process the eneigy ant1 numbei detalls 01.1 the neutron energy spectla of (a.7~)sources
of t h e gamma r a y s e n i ~ t t e ddepend upon the particular must he determined exper~mentally Short of expeil-
rlucle~mvolved. T h a t is, f o r the same thermal neutron merit, one can say wlth c e r t a ~ n t yonly t h a t t h e nlaslmum
density, the number of gamma r a y s e m ~ t t e dper unit energy of t h e neutions w ~ l lhe less t h a n the slim of the
time by a unlt volume of rock can he larger, smaller. alpha-part~cleenergy and the react1011energy D a t a on
o r the same a s t h a t from some other u n ~ volume t havlng the spectrum of neution energles emitted hv R3-Be,
8.4 neutron w h ~ c hhas not completed the slow~ng-downprocess Po-Be, and Pu-Be sources a r e included In Table 7.
 A P I CALIBRATION
FACILITY LOGS
FOR NUCLEAR 297
.-

Table 7
Pract~cal Yields from Alpha-Neutron Sources

-- Source
Ra:Be
Alpha
Em~tt.ei
Ra"26 plus
Alpha E n e r g ~ e s ,
Mev
Yleld,
Neutrons/ Sec-Curte
1 0 - 1.5 x 10'
I Neutron Energy, Mev
Average
38
1 Mas~tnum
12
decay products 5.49, 5 99, 7.68
Po. Be p0~lo 25 x lo6 4.3 . 10 8
Ac :Be Ac"" plus 4 94, 5.86,5.97, 1.7 - 2.0 x lo7 5.0 13
decay prodi~cts 6 03,6.62,6 82,
7 36, 7.43, and

Pu :Be pu?:3s 5.15, 5 13,5.10, 1 4 - 2.0 X lofi 42 10.5

It genelally thought t h a t the energy spectra of

IS The f o r e g o ~ n gobject~onsdo not apply to a properly
((X,7~) so~irces a r e not sufficiently dtfferent t o cause deslgned test plt c o n t a ~ n ~ n"subsurface"
g formations.
pronounced effects In neutron loggtng However, a s f a r Thls w a s therefore adopted a s a standard Because of
a s can be detenntned, there a r e no d a t a a v a ~ l a b l eon t h e the widespread utlhzatlon of neutron logs In Innestone
\7anous types of l o g g ~ n gtools In use w111ch can justify reservoirs and the a v a ~ l a b ~ l l tof y clean Ilnlestone, the
completely thls po111t of mew. "standard f o r m a t ~ o n "w a s chosen to be I n d ~ a n aIlme-
stone of 19 percent average l~orosltysaturated w ~ t h
Calibrat~onand Standardtzatton of Neutron Logs fresh water and drllled wlth a 7%-ln. hole; the hole
The Subcomnltttee cons~dereda t length the cholce of would he uncased and full of fresh water The A P I
a common neutron log u n ~ tNone of t h e eslstlng neutron Neutron U n ~ was t defined a s 1/1,000 of the response of
l o g g ~ n gunlts renewed In the "Introduction" had out- a tool In t h ~ format~on.*
s By d e f i n ~ t ~ othen,
n all neutron
s t a n d ~ n gmerit a s a n Industry standard. I11 p r ~ n c ~ p l e tools scaled In A P I u n ~ t smust show a deflection of
~t would be ]deal to scale neutron logs dlrectly in total 1,000 A P I unlts ~f t h e tool passes through a clean
poroslty unlts (free w a t e r plus eclmvalent bound w a t e r ) , l~nlestone bed where poros~ty, s a t u r a t ~ o n , and hole
slnce thls IS a physical u n l t and IS t h e quantlty ultl- c o n d ~ t ~ o nasl e ~ d e n t ~ c awl ~ t hthe A P I standaid Wlth
mately deslied from t h e log However, t h ~ sIS not t h ~ ssystem n e u t ~ o n logs wlll show deflect~ons fioni
f e a s ~ b l ebecause the response of a neutron tool IS not a few hundred to a few thousand A P I n n ~ t sfol the
llnearly related to poroslty and because ~t IS so affected usual range of borehole and f o r m a t ~ o ncondttlons
hy borehole variables. The Subcotnm~ttee therefore .
In a d d ~ t l o nt o t h e callbratloll formatlon, t h e Suh-
adopted a new unlt, d e s ~ g n a t e da s t h e A P I Neutron
conimlttee consldered ~t advisable t o provlde two add]-
Unlt, t o be defined In terms of a p ~ l n i a r ystandard
ttonal l~mestonef o r n ~ a t ~ oone ~ ~ sof, lower p o r o s ~ t yand
a v a ~ l a b l eto all servlce c o m p a n ~ e s
one of hlghel p o r o s ~ t yt h a n the standard The three
The follow~ngposslbllltles were consldered a s p i ~ m a l y formattons would serve to e s t a b l ~ s hone common depar-
standards f o r neutron tool c a l ~ b r a t ~ o n : t u r e curve and would p e r n ~ t teach servlce company t o
1 An actual well, probably a n abandoned cased hole. normalize ~ t laboratory
s departure curves to the A P I
2. A specla1 sleeve or t a n k slmllar to e x ~ s t l n g standard. T h ~ sprovision appeared necessary because
calibrators. there w a s considerable v a r l a t ~ o n~n porosltles asslgned
3. A test pit wlth predeterm~nedformatlon and bore- by servlce companles to the same type of limestone In
hole condlt~ons. thelr lndlv~dual test p ~ t s ,p a r t ~ c u l a r l y a t the lowest
The first scheme mas rejected on the giouncls t h a t the poros~tles. W ~ t h t h e f a c ~ l ~ t ~a et sthetr d~sposal, the
well mtght not remain usable ~ n d e f i n ~ t e l yt h, a t char-
R P 3.9 Subcomm~tteecould determine extremely accu-
a c t e i ~ s t ~ cofs the formatron would not be known pre- rately the poroslt~esof t h e stone installed ln the test
D I and~ these values would be nlutually acceptable to all.
c~sely,depth measu~etnents might be In error, c a s ~ n g
would corrode, etc. The second scheme was also rejected To sumniarlze, ~t was declded to e s t a b l ~ s h- a s a
on the basls t h a t e s ~ s t l n gc a l ~ b r a t l n g sleeves were , means f o r standardlzmg neutron logs - a standard for-
tallored to particular types of tools, I e , they contamed m a t ~ o na v a ~ l a b l eto all s e ~ v l c ecompanles. The response
a i r spaces, sliding mechanisn~s,neutron absorbers, etc., of any tool m t h ~ sstandard f o r m a t ~ o nwould be deslg-
and t h a t it mould be ~ m p o s s ~ h to l e choose o r even des1g.11 nated 1,000 A P I u n ~ t s Each servlce company woulcl
a u n ~ v e r s a lsleeve w h ~ c hmould appeal the same t o all compaie the response of a tool 1x1 ~ t field s callbrator to
slzes and types of tools I11 other words, a p a r t ~ c u l a r the response In the test formatlon and thereby asslgn
callbrator, des~gned to glve t h e same response a s a to the field callbrator the a p p r o p r ~ a t enumber of A P I
10-percent porosity format1011w ~ t hone tool, m ~ g h tglve 'Although there are several advantages to a cal~hratronhased on two
a 15-percent porostty response to another tool ,and a standard format~ons,the Subcommittee bel~evedthat the two-po~nt
method would Impose practical drficultles on the servlce companles
5-percent response to a t h ~ r d . In scaling thew logs whrch could lead to numerous scaling errors
u r i ~ t s In a c l d ~ t ~ o neach
, servlce company could Issue necessary, to act a s the prlme c o n t ~ a c t o rf o r the A P I
depalture curves In A P I u n ~ t sw ~ t hthese curves nor- In c o n s t r u c t ~ n gthe f a c ~ l ~ t yand
, to p r o v ~ d e f o r t h e
m a l ~ z e dto the response of the tool In the A P I s t a n d a i d subsequent supelvlslon, o p e r a t ~ o n and malntenance of
format~ons the f a c ~ l i t y ,wlth t h e u n d e r s t a n d ~ n g t h a t ~t could be
used f o r educat~onalpurposes. Constluct~onand opera-
IV. DESIGN O F T H E API NUCLEAR LOG t ~ o nof the faclllty w a s placed undel the ~ u r ~ s d ~ c of t~on
CALIBRATION FACILITY the Petroleum E n g l n e e r ~ n gD e p a ~ t m e n tw ~ t hProfessor
Facility 1,ocation and F ~ n a n c i n g C V. K ~ r k p a t r l c k ,head of the D l v ~ s ~ oofn Chenilcal and
As outl~netlin S e c t ~ o n sI1 and 111, t h e Subcomm~ttee Petroleum E n g ~ n e e r l n g ,d ~ r e c t l yIn charge.
on Revtew of A P I R P $3 dec~dedt h a t the best method I n F e b r u a r y 1958, a second panel of S I X memhers?
of a c h ~ e v l n gs t a n d a r d ~ z a t ~ oofn gamma-ray and neutron was a p p o ~ n t e dto coord~natet h e construct~onand opera-
logs was to construct prlmary standards In t h e form of t ~ o nof t h e A P I f a c ~ l ~ twy ~ t hProfessor K ~ r k p a t r ~ c k
c a l ~ b r a t ~ opn~ t s one
, f o r gamma-ray and one f o r neutron T h ~ scomm~ttee worked very closely w ~ t h Profess01
logs These p ~ t swould c o n t a ~ n f o r n ~ a t ~ o nws ~ t hpie- Kirkpatrlck d u r ~ n gthe detatled planning and construc-
c ~ s e l yknown plopel ties, s ~ ~ n u l a t ~snu gb s u ~face condl- t ~ o nstages A s the p l a n n ~ n gprogressed, a numher of
t ~ o n sa s closely a s poss~ble. They would be set u p a t changes were made to lower the cost and Increase the
some central locat1011wheie each servlce company could f l e x ~ b ~ l t tof
y the lnstallat~on,particularly In regard to
l u n ~ t logglng
s tools and lelate the response of each the b u ~ l d l n gand type of h o ~ s tspec~fied Consequently,
tool In the prlmary standard to the field c a l ~ h r a t o r the final d e s ~ g n descr~bed
, follow~ng,embod~esthe work
normally used. of hoth of t h e panels, a s well a s some m o d ~ f i c a t ~ o n s
I n J a n u a r y 1957, a panel' of the Subcomm~tteewas suggested by the Unlverslty of Houston staff supervlslng
appointed to d l a w up a d e s ~ g nf o r the neutron and the construct~on
gamma-ray calihrat~onp ~ t sand to ~ n v e s t ~ g a tposstble e Design of the Garnrna-ray P i t
locat~onsand methods of f i n a n c ~ n g The first f a c ~ l ~ t y
cles~gndlawn up by the panel was plesented to the S p e c ~ f i c a t ~ o nl as d down f o r the gamma-ray p ~ wele t
Suhcotnm~tteeIn May 1957, and a final r e v ~ s e dd e s ~ g n , threefold. F l r s t , the d ~ m e n s ~ o nofs the p ~ had t to be
w ~ t ha firm cost e s t ~ m a t eof $48,000 ( e x c l u d ~ n gl a n d ) , large enough t h a t the s y n t h e t ~ cf o r m a t ~ o n sa p p e a r to be
was approved In October, 1957 ~ n f i n ~ tot e gamma-ray detectors. Second, t h e p ~ had t to
Poss~bles ~ t e sf o r the f a c ~ l ~ t ay s, well a s alterriatlve have a rad~oactivezone c o n t a ~ n ~ nt hg e three naturally
methods of financing, were then ~ n v e s t ~ g a t e by d tlie occurring r a d ~ o a c t ~ v elements e - uranium, t h o r ~ u n i ,
panel A letter r e q u e s t ~ n ga n ~ n d ~ c a t ~ofo n~ n t e r e s tand and potasslum - In apploximately tlie same r e l a t ~ v e
a proposal for c o n s t r u c t ~ n g and operating the call- concentrat~onsa s occui In a n average shale, the total
bratton f a c ~ l i t y w a s sent t o 14 commerctal research a c t ~ v ~ of t y the zone had to be a p p r o x ~ m a t e l ytwtce the
o r g a m z a t ~ o n s and u n ~ v e r s ~ t ~The e s answers recelved a c t ~ v ~ tofy t h e shale. T h ~ r d ,the r a d ~ o a c t ~ velements
e
establ~shedthat ~t would not be f e a s ~ h l ef o r a commerc~al had to be dispersed In a large mass of r e l a t ~ v e l y~ n e r t
organlzat~onto constluct the p ~ t sand a m o r t ~ z ethe cost m a t e r ~ a l . Inasmuch a s such m a t e r ~ a l w ~ l lhave some
on a serv~ce-chargeb a s s The p o s s ~ h ~ l ~ oft ythe servlce s l ~ g h tr a d ~ o a c t i v ~ t ya , second zone of t h ~ ms a t e r ~ a lhad
compames alone h e a r ~ n gthe major p a r t of the cost to be prov~ded.The d~fferenceIn ~ n t e n s ~ between ty the
was d~scussedand rejected f o r several reasons, a major two zones IS used to define the A P I Gamma-Ray U n ~ t
one b e ~ n gt h a t objective and ~ m p a r t ~ acontrol l of the C o n s ~ d e r ~ n first
g the slze, tt IS known t h a t t h e
f a c l l ~ t yhy o p e r a t ~ n gcompanles could not be exerased 95-percent depth of l n v e s t ~ g a t ~ oof n the gamma-ray log
under these condit~ons.I t was concluded t h a t t h e only In a very porous formation IS appl-ox~mately1 5 In.
f e a s ~ b l e f i n a n c ~ n gmethod would he f o r the A P I to (from the borehole wall). Consequently, t h e r a d ~ u sof
u n d e r w r ~ t ethe construct~oncosts of the f a c ~ l ~ t w y ,~ t h the test ptt w a s set a t 2 f t . Even w ~ t hthe longest
m a ~ n t e n a n c eand o p e r a t ~ n gcosts t o he covered by selvlce counter In present-day use, about 3 f t , a good "plateau"
charges f o r t h e ~ ruse Accord~nglythe A P I undertook should be o b t a ~ n e dIn t h e center of the zone durlng
a s o l ~ c ~ t a t ~of o n approx~mately 50 o p e r a t ~ n g and 10 logglng T h ~ s ,coniblned w ~ t ha 1 5 - ~ n depth of pene-
servlce companles, w ~ t hthe suggested c o n t l ~ b u t ~ oof n tration, led to a - c h o ~ c eof 8 f t fol t h e bed thtckness
each company betng loughly proportlonate to the stze D a t a on a n a l y s ~ sof over 200 shales ~ndlcated t h a t
of t h e company By J u n e 1958, tlie necessary $48,000 the aveiage shale contained a p p r o x ~ m a t e l y 6 ppm
had been rece~vecl uranlum, 1 2 ppm t h o r ~ u m ,and 2 percent potasslum
I t was agreed t h a t the f a c l l ~ t yshould be located In S ~ n c e~t w a s desired to o b t a ~ ntwice the average shale
t h e Houston a r e a hecause of the f a c t t h a t a p p l o x ~ m a t e l y levelf In the radioact~vezone of t h e p ~ t concentrat~ons ,
'7.5 percent of t h e servlce compan~es'general offices and f o r t h e l a t t e r were set a t 1 2 ppm uranlum, 21 ppm
shops a r e In t h a t a r e a Accordtngly, the U n ~ v e r s ~ tofy thorlum, and 4 percent potassium F r o m the constants
Houston was approached and lece~ved the proposal .
favorably. The University agreed to d e d ~ c a t ethe land .
TW B Belknap, Chazr71rnn. Phlllrps Petroleum Co W E Mott. Gulf
Research and Development Co J. T Dewan, Schlumberger Well
Surveying Corp .W R Rabson. Pan Geo Atlas C o w . A J Pearson.
Gulf Research and Development Co . J T
*W E Mott. Clrart~~ta:)~. The Atlantrc Refining C o . and A B W ~ n t e r ,Lane-Wells Company
Dewan. Schlumberger Well Surveying Corp. A S McKay. Texaco $This level was chosen as berng h ~ g henough to mrnlmlze statistrcal
. .
Inc G~lbertS w ~ f t ,Well Survevs Inc R H Wlnn, Welex, Inc
and W B Belknap, e x ofic&o,Phrlllps Petroleum Co.
. fluctuatrons but st111 w t h ~ nllnearrty capabrl~t~es
tools.
of exrstrng logglng
 A P I CALIBRATION
FACILITY LOGS
FOR NUCLEAR 299

glven ti Table 6 ~t 1s seen t h a t , w ~ t hthe ielatlve con- T h e n i a x l m u m a m o u n t s of r a d ~ o a c t i v em a t e r ~ a l

centratlolls ~ n d ~ c a t e dnranlum
, contributes approxl- reclu~red f o r a 4-ft clianieter by 8-ft deep racl~oactlve
mately 47 percent, thorlum 34 percent and potasslum zone were e s t ~ m a t e dprlor to construct~onto he approxi-
19 peicent to the effective gamma-ray a c t ~ v ~ tofy thk mately 75 g i a m s of uranlum, 150 grams of t h o r ~ u m ,
forniat~on. and 500 Ib of potasslum, although the actual compo-
Although ~t m ~ g h thave been poss~bleto find a shale s ~ t ~ ou lnt ~ m a t e l yd~fferedf l o m these e s t ~ m a t e s .Sources
wltli the d e s ~ r e dconcentrat~oiiof radloact~veelements, of these l n a t e ~ ~ a in l s s u ~ t a h l eform f p r n i ~ s i m
~ i tlie
~
the prospect of a long search f o r a s u ~ t a b l eshale out- slurry were sought This was not a s ~ m p l etask smce
cropping was riot a t t r a c t ~ v e Consecluently, ~t was con- In each case there were certam c o n s ~ d e r a t ~ o nto s be
sidered t h a t t h e best way of achlev~llg the deslred taken Into account. F o r uranium and t h o r ~ u m ,a knowl-
a c t l v ~ t ywas to obtain accurately assayed amouilts of edge of the rad~oactlvedlslntegrat~onschemes I S iieces-
uranlum, thorium, and potasslum i n concentrated form, s a r y ; these a r e shown In Tables 2 and 3 Both elements
mlx these un~fornily In a slurry w ~ t h low-act~vity decay In a serles of steps, each w ~ t hits characteristic
cement, pour the s l u i r y Into t h e p ~ t ,and allow ~t t o half-11fe and type of emlsslon (gamma, beta, alpha, o r
set u p In the foim of concrete T h ~ h s a s the advantage comhlnat~onthereof), untll a stable lsotope of lead 1s
t h a t ~f the r a d ~ o a c t ~ v~en a t e r ~ IS
a l u m f o r n ~ l yd ~ s t r ~ h u t e d reached The Important polnt 1s t h a t when uranlunl or
to begln w ~ t h ~t , lenialrls so ~ n d e f i n ~ t e l y t h o r ~ u n la r e contamed In a glven volume f o r a suffic~ent
Fig. 1 shows the final d e s ~ g nof the gamma-ray p ~ t length of t ~ m e ,a condlt~on of e q u ~ l r b r ~ u m 1s reached
I t contams 3 sepalate concrete zones each 4 f t In whereln the numbers of atoms of each member of the
d~anietel and 8 f t deep. The top zone, of low-act~vlty serles N , , N2. N3. etc. become constant and a l e cliar-
concrete, 1s prlniallly a cosmlc-ray s h ~ e l d ;the m ~ d d l e a c t e r ~ z e dby t h e relation N , I T I = N21T, = N,?IT,, etc.,
f o r m a t ~ o n - I the
S r a d ~ o a c t ~ vzone
e (see Tables 9 and 10 where TI,T,, T,, etc a r e the correspond~nghalf-l~ves
for final concentrat~onsof r a d ~ o a c t ~ vmaterial) e , and of each. (Thls condltlon of e q u ~ l ~ b r ~ u1smgenerally
the bottom format1011 1s the l o w - a c t ~ v ~ t"background" y assumed t o exlst In subsurface f o l m a t ~ o n s , although
zone. A 5%-in 17-lb caslng extends thlough the three dev~atlonsfrom equ~llbrlumhave been reported, par-

"*,
zones and 15 f t below them. t ~ c u l a r l yf o r outcropplngs or marine s e d ~ m e n t swhere
selective l e a c h ~ n gor d~ssolutionof specific Inemhers of
I' 4 'D l STEEL DECK PLATE the serles has occurred.)
In the case of uranlani, ~t 1s easler to ohtaln a pre-
c ~ s e l yknown quantity of t h e daughter product radlum
than of uranluni Itself I t I S l e g ~ t ~ i n a t ?e use r a d ~ u m
because approxiniatelv 98 pelcent of the gamma l a y s
LOW ACTIVITY CONCRETE
above 100 kev e n i ~ t t e dby uranlum In e q u l l ~ b n u mm ~ t h
~ t sdaughter products come from the products below
r a d ~ u m .The r e q u ~ r e damount of r a d ~ u n iIn equ~llbrlum
w ~ t h75 g r a m s of uranlum I S 25 nilcrograms In order
CORRUGATED P I P E to have some r a d ~ u m available f o r p ~ l o t nllxes, a
cluantity of 40 micrograms of radlum in t h e form of
a n insoluble compound (sulfate) ~ n t ~ m a t e m l y~ x e dw ~ t h
40 I b of 20130 Ottawa s ~ l l c asand w a s obtalned. N a t ~ o n a l
RADIOACTIVE CONCRETE Bureau of Standards cel-t~ficat~on on the amount of
r a d ~ u mw a s prov~ded.
Radlum decays initially to the element radon, whlch
1s a heavy g a s and whlch h a s a 3 8-day half-l~fe. It
was a n t ~ c l p a t e dt h a t some of the ladon, w h ~ c hwould
be 111 equilibrlunl w ~ t hthe r a d ~ u mwhen rece~ved In
LOW ACTIVITY CONCRETE sealed c o n t a ~ n e r s ,would escape to tlie all d u r ~ n gthe
process of mlxlng the cement s l u l r y f o r the test p ~ t .
Thls necessitated waiting sevelal radon half-lives-
about 3 weeks-after pourlng the conclete foi the
activlty of p l o t nllres 01 of the gamma-ray p ~ ltself t
to b u ~ l dup to e q u ~ l ~ b r ~before u n ~ maklng measurements
CASING (5; 0 0.17 : ~ - 5 5 ) One advantage of niaklng the test p ~ concrete t 1s t h a t
~t p o s ~ t ~ v e lInsures
y t h a t radon m ~ l l not escape The
loss In a n unconsol~datedformat1011would, In all proh-
a b l l ~ t ybe
, n e g l ~ g ~ bhut
l e a small element of doubt would
exist.
I n the case of t h o r ~ u m ,a somewliat s ~ m l l a i problem
Fig. I-Gamma-ray Log Calibration Pit of e q u ~ l l b r ~ u marlses The ~ n i n ~ e d ~ adaughter
te of
300 BELKNAP,
L)EWAN, KIRKPATRIC

thorlum is Mesotholiuni I, whlcli has a 6 7-year half-life. Carthage marble, w h ~ c hh a s a p o r o s ~ t y 111 the range
T h ~ snuchde 1s a n lsotope of r a d ~ u m so t h a t when 1 to 3 percent, I n d ~ a n alimestone w ~ t ha porosity of
t h o r ~ u m1s refined and the radlum w h ~ c h1s nornially 17 to 20 percent, and Austln l~mestonew ~ t ha poroslty
present IS lemoved, the Mesothor~umI IS also removed. of 25 to 30 percent. These m a t e r ~ a l s wele o b t a ~ n a b l e
A perlod of 20 to 30 yeais IS r e q u ~ l e df o r t h e Meso- in Houston, 111 the form of closely mach~ned blocks.
thorlum I to agaln approach equillbnum Attenipts were The slze of the f o r m a t ~ o l l s111 t h e neutron p1t 1s
therefore made to locate a supply of t h o r ~ u mrefined determined by the depth of i n v e s t ~ g a t ~ oofn the neutron
20 to 30 years ago; thls proved to be f r u ~ t l e s s I11 l ~ e u log T h ~ sI S strongly dependent upon poros~ty, b e ~ n g
of the refined t h o r ~ u n2~ k ~ l o g r a m s of finely ground greatest In low p o r o s ~ t ~ ewhere
s, t h e 90-percent depth of
~ n o n a z ~ t ore
e assaying 9 70 percent t h o n u m o x ~ d e p e n e t r a t ~ o nwith radium-beryllium neutrons, IS about
( a p p r o x ~ m a t e l y180 g r a m s of t l i o r ~ u m ) and only 0 37 2 f t However, in the f u t u r e t h e use of 14-mev neutrons
percent uranlum oxide w a s obtained from t h e New (from the H"d,n)He4 reaction) may become w ~ d e -
Brunswlck laboratory of t h e Unlted States Atomic spread These neutrons should have a somewhat
Energy C o m n ~ ~ s s ~ A o n check by the AEC laboratory Increased depth of investigation although the exact
showed t h a t the m o n a z ~ t emas w ~ t h l n 2 percent of amount IS difficult to assess. Consequently, a r a d ~ u sof
equlllbr~um. An a d d ~ t ~ o n a2l2 k ~ l o g r a m sof monazite 2 % f t was chosen. The depth of the formation w a s set
ore assaylng 5 5 to 6.0 pelcent T h o 2 and 0.1 peicent a t 6 f t , based on the exper~nlentalf a c t t h a t the vertlcal
U,08 eras donated to the project but not used n ileutron logs is approx~mately
depth of l n v e s t ~ g a t ~ oof
I n the case of p o t a s s ~ u m ,a d ~ f f e r e n ttype of problem 2 f t The 6-ft depth should therefore give a good l o g g ~ n g
arose. Here a relatively large amount of the material "plateau."
is required. However, easily a v a ~ l a b l ep o t a s s ~ u mcom- Fig. 2 shows a-cross-sect~onalvlew of the neutron pit.
pounds, such a s KCL and KISO,, a r e water-soluble I t I S 24 f t deep overall, with a 15-ft rathole e x t e n d ~ n g
Thls posed a d~fficult problem of assuring u n ~ f o r m below the bottom zone. The 3 l ~ m e s t o n efolmations a r e
d ~ s t r ~ b u t i oofn the potassium In the cement s l u r r y slnce each made up of 6 octagonal blocks, each 1 f t t h ~ c k wlth ,
a n y excess water would tend to collect on top a s t h e carefully machined flats. A 7%-ln. hole extends through
cement set up The solutlon adopted was to use mlca, the center of the p ~ tThe porosit~es~ n d ~ c a t e011 d Flg. 2
whlch is insoluble, a s a source of potass~um.Potassium a l e the final values assigned to the formations (see
mlca (muscovite) h a s the theoretical formula H2KA13 S e c t ~ o nV I ) On top of the stone IS a 6-ft layer of w a t e r
(S1O4)3 w h ~ c hi n d ~ c a t e sit contains 9 8 percent potas- w h ~ c hserves the dual purpose of provldlng a 100-percent
sium by weight A quantlty of magcomica assayed 9 poroslty reference p o ~ n tand s h ~ e l d ~ nthe g gamma-ray
percent K, 1 0 8 ppm U and 0 01 ppm Th T h ~ was s used detector In G R N tools from excessive r a d ~ a t l o nfrom
In t h e test p ~ tHowever, slnce the p ~ recluired t a con- the neutron source a s the tools log the upper lrnlestone
centratloll of 4 percent K, it was necessary t o fill about
half of the volume of the r a d ~ o a c t ~ vzone e with mlca.
Slnce mlca h a s a i e l a t ~ v e l ylow bulk d e n s ~ t y ,t h ~ sled
to a n overall bulk denslty in t h e r a d ~ o a c t ~ vzone e con-
siderably less than In t h e other two zones and less than
nornially occurs In subsurface forniat~ons.
Details of the rnlslng procedure, pilot checks, labora-
tory analysis, etc f o r the gamma-ray pit a r e glven
m S e c t ~ o nV.
Design of t h e Neutron Pit
CARTHAGE LIMESTONE
In designing the neutron p ~ t ,there w a s conslderahle (POROSITY=I 9V.AVG)
expellence to draw upon slnce a number of the members
of the afolenient~oned panels had already constructed
somewhat s ~ m i l a r plts f o r thelr p a r t ~ c u l a roperating INDIANA LIMESTONE
(IS%AVG POROSITY)
or service companies.
General spec~ficat~ons f o r the neutron p ~ were
t that AUSTIN LIMESTONE
( 2 6 % AVG POROSITY)
~t hat1 to contaln three clean (shale-flee) l~mestone
folmatlons - one of low poros~ty,one of Internledlate
poros~ty, a n d one of h ~ g hporosity. The formations
hat1 to be "infi~nte" in slze, conipletely saturated w ~ t h
fresh water, and have accurately known poroslt~es.The
~ n t e r m e d ~ aporoslty
te zone would be used a s a standard
f o r c a l ~ b r a t ~ o nwhereas
; t h e other two, in conlunction
w ~ t ht h e mtelmediate zone, would he used to e s t a b l ~ s h
a standard departure curve BLOCK DETAIL
F o r the t h i e e types of stone there w a s little alterna-
t ~ v ebut to choose those already nl common use, v ~ z , Fig. 2-Neutron Log Calibration Pit
 FACI
A P I CALIBRATION

zone A %-In. thlck luclte pipe extends through t h e and approved by the API. Construction of the faclllty
water zone to guide upper decentralizing dev~ces on was begun In September 1958 on a %-acre slte on the
logglng tools Thls pipe h a s no noticeable effect on t h e University of Houston campus, and completed in J u n e
neutlon response In the w a t e r zone. 1959. Genelal layout of the facillty IS shown In F i g 3
The method of saturating hhe blocks w ~ t hfresh w a t e r The Gamma-ray Plt
and of nieasuiing the amount of w a t e r in them a f t e r
Follow~ngexcavation and placement of the walls and
s a t u l a t ~ o nwas given a g r e a t deal of attention. Industry
centered caslng in the gamma-ray pit, the first low-
experience on smaller blocks indicated t h a t vacuum
activlty zone w a s poured using a neat portland-cement
implegnatlon was absolutely necessary to achieve com-
slur1 y. To insure uniforniity of cement used In all zones,
plete s a t u r a t ~ o n .Furthermore, slnce t h e blocks would
a quantity suffic~entf o r all three zones w a s p u ~ c h a s e d
be too heavy f o r a n accurate measurement of d i y weight
from the same source.
and wet welght, t h e only method of measuring directly
the amount of w a t e r held by each block w a s to com-
pletely desaturate ~t first and then to measure t h e Table 8
amount of water whlch ~t took up on saturation To thls Calculations of Material Quantit~esRequired for
end an elaborate s a t u l a t ~ o nsystem w a s deslgnetl, a s Gamma-ray High-activity Zone
descllbetl In the follow~ngs e c t ~ o n
I T/olicme of Portron of P L to~ be F ~ l l e d
V. CONSTRUCTION O F T H E CALIBRATION Volnme = .rrR" depth
=.rr(2 ft)" 8 f t = 100.5 c u f t
FACILITY 11. Spec~ficGravity and Density of 11Izx
Contracts and General Layout A s deteim~netlfrom small pilot mixes
Spec~ficgravlty = 1.47
Upon ieceiving authorization f l o m the API, t h e Denslty = 91.6 lb pel cu f t
University of Houston, acting a s prime contractor, 111. Totc~lTT7eig1rtof Mix Regutred
sol~cltedtulrlkey blds f o r the major constluct~onItems Weight = density x volume
of the f a c ~ l i t y . All blds were considered too high,
= 91 6 x 100.5 = 9,220 lb
01 4 18 x lo6 g m
w h e ~ e u p o nsubcontracts wele let f o r varlous poltlons IV. Q i u ~ n t i t yof IIf~caReqi~rredf o r 4-percet~tK
of the construction a s follows. ( b y weiglit) Concentrcctzo?~r t ~JItx
1 Fol major, slte wolk i n c l u d ~ n g~nstallatlonof the (Mlca analyzed t o contain 9.0 percent K )
two plts, all concrete slab wolk, g l a d ~ n g , and Q u a n t ~ t ymica = ( K concentlat~ondeslredl
K concentration In m ~ c a )
sliell~ngof adjacent areas. ( w e ~ g h of
t mix)
2 . Fol ~nstallationof a 20-ft x 40-ft ~nsulated,heated, = ( 0 04010.090) (9,220)
a l l - c o n d ~ t ~ o n e dmetal
, b u l l d ~ n g ~ n c l u d ~ n gwork = 4,097 lb mica
benches, a small office, lavoratory, and dark room. V. Qluitzt~tyof Wonaztte Sccnd ( T h o n ) Reqiiirecl fot:
3. Fol installat~onof a specla1 jib-type crane wlth a 24-ppn Tli ( b y w e i g h t ) Co?rce>rtrc~tto)~ In Jflx
40-ft boom and electrlc controls (Sand analyzed to contaln 9.7 percent T h o o and
4. Fol qualrying and fabrication of the limestone 0 37 pelcent U308)
blocks f o r the neutron pit Q u a n t ~ t ysand = [ ( T h ppm desired) ( w e ~ g h tof
5 Foi necessaly carpentry, electrical, and plunlblng mix)] / [ ( T h o 2 concentiatlon 111
work sand) (molecular w e ~ g h t T h /
6 F o r ~ n s t a l l a t ~ oof n a steel fence s u r r o u n d ~ n gt h e molecular w e ~ g h tT h o 2 ) ]
facillty. = [(24) (9,220)]1
All contract work w a s performed 111 accordance wlth [ (0.097) (2321264)l
= 2.6 lb o r 1.177
, -Em sand
speclficatlons furnished by t h e Umversity of Houston
V I. Qtic~ntttyof R a d z z ~ nOttmrucc.
~ Sand Regz~z.redf o r
12-ppm U ( b y w e z g l ~ t )Concentrutzo,t~z 7 ~Mzz

Ii GATE
1 , 7
(Sand analyzed to contain 1 bg R a per Ib)
From (Half llfe Rathalf llfe U )
= [(l.620) (lo3) l(4.51) ( l o 9 ) ]
= (0.359) (10-6)
U = 0.359 ppm R a
GAMMA-RAY LOG
U cleslred .x. R a I U
CALIBRATION P I T = R a necessary per gm mix
( E L E C T R I C CONTROLS I
1 2 x 10-6 X 0 359 X 10-6
= 4 31 x 10-'"1 R a per gm n11x
NEUTRON LOG 4 31 X 10-1- 4 18 X lo6 gm
CALIBRATION P I T
= 18 b g m R a required
= 18 Ib sand requlred
VII. Qziat~tttyof Neclt Portlc~ndCement Required
for M Z X
13 percent a s determined from pilot mlx
lz=='"- 108'-0.
Fig. 3-Plan and Layout of API Nuclear Logging
I
VIII
0 13 X 9,220 Ib = 1,200 lb cement
Qriant~tyof W a t e r R e q l ~ i r e d f o r I l f t z
42.33 percent a s determined from pilot nlix
Calibration Facility 0.423 X 9,220 Ib = 3,903 lb o r 468 gal w a t e r
 F o r the hlgh-act~vltyzones the materials selected f o r The upper low-actlvlty sectlon, s l m ~ l a rIn compos~tlon
m ~ x t u r e wlth cement were r a d ~ u m - c o n t a ~ n ~ nsand,
g t o t h e bottom s e c t ~ o n ,w a s poured approx~lnatelyone
t l i o r ~ u m - c o n t a ~ a i i ~monazlte
g ole, and potasslum-con- month a f t e r the h ~ g h - a c t ~ v l tzone
y
t a ~ n l n g mica Three major 011-company laboratories The Neutron P i t
analyzed the cement and mica by gamma-ray spec-
A f t e r selection of stone types to be ~nstalledIn t h e
t ~ o s c o p yto d e t e ~ m l n ethe U, Th, and K content. Content
of the Ottawa sand and m o n a z ~ t eo r e w a s certified by neutron pit, quarrles throughout t h e U n ~ t e dS t a t e s were
the supphers. From this ~ n f o r m a t l o nthe quantities of contacted, a n d a Houston company w a s selected a s best
ecluipped to furnlsh the stone blocks 111 conformance
i n a t e ~ l a l sused 111 the n u s were calculated a s shown In
with the following approved speclficatlons
Table 8
Slx octagonal blocks of each type stone (Carthage
Extensrve pilot nlixung w a s then performed t o confirm marble, Indlana limestone, and A u s t ~ nllniestone)
adequate nilsmg control and to check the calculations. to measure 5 f t across the flats and 1 f t thlck w ~ t h
The samples wele first mlxed 111 % and 1 cu f t batches, a 7%-ln dlameter hole bored through the center
and finally a test barrel of a p p l o x ~ m a t e l y25 cu f t w a s of each, all machlned surfaces to be w ~ t h ~1132-ln.
n
p o u ~ e da ~ o u n da plece of 5%-ln. caslng 011-company tolelance, each type of block to be cut from a slngle
l a b o ~ a t o i l e sr a n spectral analysls on each pllot mlx large piece of stone to provlde nlaxlmunl un1-
a f t e r each lnlx was allowed to set f o r 2 t o 3 weeks f o r formlty of poroslty, n i a t r ~ s character, and geo-
e q u ~ l ~ b r a t l oofn the radon g a s I n a d d ~ t ~ othe
n l a r g e test logical environment.
balrel was "logged" by two servlce compan~es f o r To permlt checking the u n l f o r m ~ t yof poroslty between
p ~ a c t l c a l confilmatlon of over-all r a d ~ o a c t ~ v l t y stones of a glven type, and fol late1 cornpailson wlth
F ~ o mthls wolk ~t was found t h a t considerable d r y final saturation values, ~t was agieed t h a t e x t e n s ~ v e
mlslng was necessaiy to obtain uinform d l s t r ~ b u t i o nof core analysls should be performed on samples of each
the ratlloactlve n i a t e l ~ a lthroughout the mlx F o r actual block To f a c ~ h t a t ethls, the s u p p l ~ e rfirst m a c h ~ n e dthe
poullng of the pit the inaterlal was d r y n ~ ~ s eInd a blocks ~ n t o5-ft squares, 1f t t h ~ c kUnder the supel-vlslon
c o r n m e ~ c ~ mlxel
al for 8 hours, then 2 hours more a f t e r of the student project englneel, the colners were sawed
the a d d ~ t ~ oofn water C o n i p o s ~ t ~ oof
n the mlx wlth off, formlng the fin~shed octagon, and then a 4-111.
s u ~ n n i a t ~ oof n radloactlve components 1s presented In d ~ a n l e t e rcore was taken from t h e center before lathe
Table 9, from mhlch ~t 1s seen t h a t total component turnliig t o the 774-1n finished d ~ a n ~ e t eEach r removed
a c t l v ~ t l e sa r e very close to the spec~fiedd e s ~ g nvalues corner sectlon a n d center core w a s carefully tagged and
A s l u ~ r yvolume a p p ~ o x ~ m a t e l15
y percent In excess of coded to t h e block from whlch ~t w a s taken These
the calculated volume needed was mixed. Durlng t h e sectlons were then cut ~ n t oS I X pleces (each t a g g e d ) ,
pourlng operation a sample w a s taken a s each foot of and samples from all sectlons d l v ~ d e dInto S I X sets, each
the sect1011w a s poured f o r later laboratory analysis by set t h u s h a v ~ n ga sample from every corner and centei
gamma-ray spectroscopy core removed from every block.

Table 9
Composition of Flnal Mix for H~gh-activityZone, Gamma-ray Pit

R a d l a t ~ o nComponent

1 86 x lo6

R a d ~ u mOttawa Sand1' 1 8,180 18 1 I 1 . 1 . 5 0 3 1 0111

Water
3,903 1 1 1 102 49
1( .

0 2256
1 .

54 545
1
I
0 12035
Total -
Conipos~t~on Actual 4.07 percent K 24 4 ppm Th 1 3 1 ppm U
By Weight
Deslred 4 percent K 24 ppm Th 12 ppm U
-

aAEC cert~ficat~onof 9 7 percent Tho, and 0 37 percent U s 0 8

b18 lb Ra sand = 18 ugm Ra = 50 3 g m U equ~valent
cSame type cement poured neat for lower and upper low-act~v~ty zones Concentration determ~ned by gamma-lay spectroscopy
 A P I CALIBRATION
FACILITYFOR NUCLEAR
LOGS 303

I
Arrangements were made with f o u r major oil-company a r e b e ~ n g retamed f o r chem~cal analysls a t a later
laboratories to r u n small core analyslson a complete set date. F o r general information, semi-quant~tative spec-
of these samples The U n i v e l s ~ t yof Houston Petroleum trographlc analysis made by a testlng laboratory In
Engineering Depaitment analyzed the fifth set and the 1951 on samples of slmllar stones I S given In Table 10
slxth set 1s being retamed a t the facihty foi possible F o r processing the blocks, many methods were con-
f u t u r e use Results of this analysis a r e tabulated and s ~ d e r e d and d~scussed with particular regard t o the
discussed In Sectlon V I I Samples of dust obtalned accuracy w ~ t hwhich final saturation could be measured
duling the cuttlng of the blocks were also collected and The method selected prov~dedf o r accomplishment of the
following objectives
Table 10 1 Effective d e h y d r a t ~ o nand satuiation of all blocks
Semi-quantitative Spectrographical Analysis of wlth accurate measuiement of all expelled and
Carthage Marble, Indiana and Austin Limestones absorbed w a t e r
Performed in 1951 2. Means of measuring bulk volumes of the blocks fol
comparison wlth geometi~cally computed values.
(Percent by weight; oxygen omitted)
Carthage Ind~ana Austln Arrangement of t h e e c l u ~ p ~ n e nnecessaiy
t fol the
Marble L~mestone Limestone process selected IS shown in F l g 1. One of the principal
Calc~un~ 37. 35.6 38.07 components 111 t h e system 1s the s a t u r a t ~ o ncham be^
Slllcon 18 0.8 0.39 which w a s leased from a company who had constructed
Ilon 0.1 0.14 0.19 ~t f o r a slmllar purpose I t s dimensions weie sufficient
Magnesium 1.3 24 1.06 to permlt piocesslng three blocks a t a time, and 0 - r l n g
Chl o n ~ ~ u n ~ 0 002 0 0008 0 0001 s e a l ~ n gof the lid piovided foi m a ~ n t a i n m gthe necessaiy
Aluminum 02 0 03 0.03 high vacuum durlng phases of the piocess. To ald in
Copper 0 001 0.0074 0.0034 dehydratlon of the blocks, eight 1,500-watt 220-volt s t r l p
Manganese 0.06 0.0033 0.0016 heaters were Installed withln the chambei uslng spark
T~tan~um 0.009 plugs f o r electrical connect~onsthrough the chamber
Stront~um Trace wall.

3-PIN
TEMPERATURE

SIGHT
GLASS

I VOLUME SOURCE
SATURATION TANK
START CALIBRATION A-A'
CHAMBER 3 ' 30'
~
E N D CALIBRATION 8 - 0 '

Fig. &Flow Schematic for Limestone-block Saturation

304 BELKNAP,
DEWAN,KIRKPATRICK,
MOTT,PEARSON,
A N D RABSON

Connected to t h ~ chamber
s w a s a h~gh-capacityKlnney leak-free connections. Through simulated runs, specific
Model KS-13 vacuum pump which performed very satis- procedural instructions were worked out and hsted t o
factorily In obtaining good vacuum in t h e chamber. avold e r r o r s occurrii~gduring actual processlng. Thls
Installed In the llne com~ectingt h e chamber and pump piocedure is described in Table 11.
was a large spherical-type watei t r a p equlpped wlth a
compiessol-diiven r e f r ~ g e r a t i o nu n i t assembled by t h e Table 11
project engineers Thls vei y effectively removed w a t e r Procedure for Calibrating
vapor befoie r e a c h ~ n gthe pump L~mestone-block Saturation System
Also connected to the s a t u r a t ~ o nchambe] w a s t h e (Refer to Fig 4 for System Layout)
large-volume tank which w a s fabricated a t the faclllty h1(1,rkA' was aibltrarily etched on the s ~ g h tglass of
fioni a 25-ft section of 3-ft dlameter pipe Henilsphencal the volume t a n k near its top and the tank then filled
heads were used to cap t h e plpe ends to form t h e tank, with w a t e r to t h ~ slevel, also f i l l ~ n gthe lower line t o
w h ~ c hwas sand-blasted and painted before using. A valve or illark A.
slght glass was fitted to the s ~ d eof the tank to permlt Illark B w a s a r h ~ t r a r l l yetched on the s ~ g h tglass
water-level measurements necessary d u r ~ n gthe satura- extending above t h e s a t u r a t ~ o nchamber. IJc~lveA w a s
t ~ o nprocess opened allowlng water to flow fioni t h e volume t a n k to
A beam-type scale with a c a p a c ~ t yof 69 5 kilograms, the satuiatlon chamber reachlng Mr~rk B. (No blocks
accurate to 12 5 grams, was purchased to enable accurate In chamber )
measurement of water q u a n t ~ t l e sadded to the volume dlark.B' was etched on the volume chalnbei's glass
tank fol block s a t u l a t ~ o n M~scellaneous equipment a t the level to which water had fallen. (The volume of
included a multl-pen recordei and thermocouples f o r the tank between Mc~rksA' and B' represents t h e total
continuous m o n l t o r ~ n gof watel temperatuies 111 the volume of the saturatlon chamber from filwks A to B.)
system, and a DuBrovln ahsolute pressule gage f o r Using the w e ~ g h i n gscale (installed on t h e supporting
vacuum measurements. scaffold), and w ~ t hValue A closed, exactly 60 cu f t of
In practlce tlie s a t u r a t ~ o nprocedure w a s repeated watei weie welghed and added to the volume t a n k and
s e v e ~ a l tlmes c o n f i l n i ~ ~ i gaccuiate placement of all Illcwk B m etched on the glass a t t h ~ slevel. The volume
marks on the glasses I n addltlon, tempeiatures of the of the cliambe~between IlIc~~ks B' and Bq~tis 60 cu f t
watel In the saturation chamber and volume t a n k were whlch represents the nommal bulk volulne of a group of
cont~nuously iecorded t o provlde means f o r volume three blocks. The volume between Il.lo+ks A' and Bnz
corrections due to denslty changes of the w a t e r from ~ e p r e s e n t sthe volume of the s a t u r a t ~ o nchamber from
temperatule vai latlons The system y a s then drained Illark A to B minus tlie nonilnal bulk volume of three
and made leady f o r dehydiatlon of the first group blocks
of blocks.
The 1 8 blocks were d ~ v l d e dinto 6 i r o u p s , 2 each of Wlth a group of dehydrated hlocks i n t h e saturatlon
similar type, and the geonietrlcal volume of each block chamber under full vacuum, the follow~ng s a t u r a t ~ o n
calefully measured and added w ~ t hothers 111 ~ t group s process was begun.
f o ~asslgnnient of each group's bulk volume. I n all cases 1. Volume tank and line (to valve Illnrk A ) w a s filled
this amounted to shghtly over 60 cu f t wlth w a t e r to Illark A' on the s~gllt-glass.
The fiist gioup of three stones was sealed Into t h e 2. llc~lve A was opened allowing water from t h e
saturatlon chamber and, wlth Valve A closed, a vacuum volume t a n k to be drawn ~ n t ot h e saturatlon
was pulled on the chamber. A f t e r about 200 hours of chambef up to nlr~rk B, completely floodlng t h e
evacuation of the first group, it w a s dec~dedt h a t heaters blocks The water level In the volume t a n k Imme-
should be mstallecl within t h e chamber to accelerate and diately clropped t o Mark Bm, representing t h e
Insure better dehydrat~on.T h ~ sw a s done, enabling a volume of the vold space 111 the saturatlon chamber
chamber temperature of 200 to 220 F. to be m a l n t a ~ n e d However, a s the blocks absorb watei t h e level
during evacuation. W ~ t hthls temperatule, e v a c u a t ~ o i ~ dropped below dlark Bw1 and Vcthre -4 was a d ~ u s t e d
time ranged from 175 hours f o r one group of Austlii to m a l i i t a ~ n t h e watei level 111 the saturation
blocks to 77 hours f o r one group of Indlana blocks chamber a t I\lark B. P e r l o d ~ cadjustment of Vc~ltre
W a t e r collected 111 the t r a p was measured to deterln~ne 4 was necessary to m a ~ n t a i i ithe level a t Ilrlr~rkB
o r ~ g l n a lwater saturatlon of t h e blocks Values v a n e d untd a b s o ~ p t l o lceased
~ (38 hours f o r Carthage
s ~ g n ~ f i c a n t leven
y between s ~ m ~ l agroupsr because of blocks).
some blocks belng exposed to cons~derabler a m whlle 3. Upon l e a c h ~ n gstatlc equlllbr~um,and w ~ t ht h e
a w a ~ t l n gprocesslng water level a t jlln+li B, ( w ~ t hValve A closed), t h e
Satisfactory dehydration of the blocks was deteimlned watel level In the volunie tank was a t some point
with the a ~ dof a DuBrovin ahsolute pressure mercury below Mark BWL.
gage Reacllngs of 2 mm H g f o r Carthage, and 6 to 7 4. A volume of water was carefully welghed ~ n t ot h e
mni H g f o r Indlana and A u s t ~ n were found t o be volume tank t o brlng the level hack u p to filnrk B?n.
acceptable. A f t e r necessary temperature correct~ons,t h ~ svol-
P r ~ o r to commencing s a t u r a t ~ o n of the limestone ume of w a t e r represented the quantlty absorhed by
blocks, the e q u ~ p m e n tw a s carefully checked f o r proper the group of three blocks f o r complete saturatlon.
 Table 12
Neutron Pit - Block Processing Data

Block Numbel sa I16,17,18 113,14,15 1 10,11,12 17,8,9 1 2,4,6 1,2,3

Ind~ana Indlana Carthage Carthage
Type L~mestone Liniestone Limestone Llmestone Marble Marble
Austln
Started Process, Date 4-18-59 1;;;:; 1 5-17-59 5-23-59 5-29-59
Placed ~n Pit, Date 5-7-58 5-17-59 6-6-59
Evacuation Tlme, H r :Mln 121.30 102.10
Refrlgerat~onTlme, H r :Min 154.30 174.10 99 0
Water Removed, Cc 153,995
Computed Saturation Before Processing, Percent 33 0
Tlme Heaters On, H r :Mln 1 176:50 121 :30
Saturation Time. H r :Mln 133:45 139.30
S a t u r a t ~ o nTemperature of Volume Tank, Deg F., S t a r t F i n ~ s h 174178 1-182 176178 180185 177186
Total Water from Pump and Sphere durlng Saturation, Cc 1250 6,702
IWe~eht.
- , Grams = Volume. Cc '
/I 445.430 134.195
Total Water W e ~ g h e dIn
IWater Temperature, Deg k. 1 72 1 79'
Bulk Volume Weight, Grams 32,263
Weight In Temperature, Deg F., TankJWater 66/65
Geometr~cBulk Volume, Cu Ft. 61 137 61.394
Porositv Index. Percent 125 55 1 26 37
Deviation Measured from Geometric Bulk Volume, Cc 10 10 I +500 10 1 +6,800h
aBlocks 1, 3. 6. 4, 7 9, a n d 10 a r e harlrne-cracked
bShould have been 7% hours less due to pulling In water vapor overnight
cIlsed d w Ice a n d acetone. ~ce-creamsalt
d v a l i e should be 8.552 due to oulllne In water vaoor o v e r n ~ c h t
ev%& should be ~ ~ 0 d u e h p ; l l ~ ~ ~ - 1 ~ ~ k a t e ~ ~ v a p ~ ~ ~ o ~ e m ~ ~ 6 t ~
fExcess bulk volume W a t e r weruhed In after saturation d ~ dnot Include the volume above the 60 cu f t mark on volume tank. o r 1 326 cu f t
EExcess bulk volume W a t e r welghed In a f t e r saturation d ~ dnot ~ n c l u d ethe volume above the 60 cu f t mark on volume tank, o r 1 2 5 2 cu f t
hDue to 1.200 cc celotex volume
 111establishing the bulk volume illark Bm, a nominal VI. DETERMINATION O F FINAL
value of 60 cu f t was utilized, whereas actual geomet- STANDARDIZATION VALUES
rlcally computed bulk volumes of the groups of three I11 considering the role of t h e two plts a s industry
blocks varied from 61.1 to 61.4 cu ft. Consequently, the standards, i t 1s ~ m p o r t a n tto understand their dual
level of Ilfark BWLwas adjusted for each group to nature in this capacity. I n one sense the plts a r e
account for thls difference. To check the accuracy of "arbitrary" standards established by A P I assignment
the geometrically calculated bulk volume of t h e blocks, of arbitrarily selected numbers of A P I units to t h e
the following procedure was used. response of logging instruments exposed to certain zones
1. With the blocks completely saturated, the satura- in the pits. As "arbltrary" standards, the pits completely
tion chamber was drained back to Valve A, and satisfy t h e b a s ~ cobjective sought In p r o v ~ d ~ nmeans
g
volume tank filled to Mark A'. of standardizing all log responses 111 common units
2. Valve A was then opened, b r l n g ~ n gthe water level related to a standard environment In another sense, the
to Illark B with the aid of a slight vacuum, and plts may be consiclered "absolute" standards, provid-
then closed. Ing certain basic and useful properties quantitatively
3 The water level in the volume tank should then established 111 absolute u ~ u t s Snch knowledge furthe1
have retuined to Il.lmrk B ~ I Any
.. deviation repre- enhances the value of the plts to the industry by
sented the difference between ge~metricallycalcu- accurately interrelating these properties to A P I u n ~ t s
lated and expe~iineiltallydetern~medbulk volume. and hence to log response.
Deviations were found to be qulte small, t h u s con- The many measurements made durlng construct~onof
firming the accuracy of the computed bulk volumes. the plts provide for deterininat~onof certaln of these
Flnal operation involved transferring the saturated properties 111 absolute units. F o r t h e gamma-ray pit,
blocks from the chamber into t h e n ploper positlon in concentration of each of the three radioactive compo-
the neutron p ~ t .Thls w a s accoinplished through use of nents (U, Th, and li) may be established, a s may be
a specially constiuctecl sling des~gnedto clamp tightly porosity-index* values f o r each of the three zones In
around the octagonal periphery of the blocks. Processing the neutron p ~ tA discussion of the cleteimlnation of
and pit-stacking order f o r the blocks was prearranged these absolute properties from the measured d a t a
(using porosity values from core a n a l y s ~ s ) ,to provlde follows.
maxlmunl unlfo~nlltyof poros~ty near the mlddle of The Gamma-rag Plt
each zone. I n the determination of the U, Th, and K concentra-
Principal data accumulated durlng the processlng of tions in the high-activity zone of t h e gamma-ray pit,
the 6 groups of blocks a r e given in Table 12. Porosity- two sets of measured data were available-one from
index values for each group of blocks were computed the small samples taken during pourlng of the zone
from the measured data a s the ratio of absorbehzuater which were laboratory-analyzed b y gamma-ray spec-
volumelblock bz~lkvolzsnae. Of particular ~ n t e r e s tis the troscopy, and the second from measurement of quantities
very close agreement of these values between groups of of these matenals actually introduced into the mlx. The
s l m ~ l a rstone types. These values also compare favor- latter measurements have been presented 111 Table 9
ably with those obtalnecl from core a n a l y s ~ s of the from which i t is seen that d e s ~ g nvalues a r e closely met
small samples, further confirming the adequacy of f o r each of the three elements. The results of t h e sample
the selected processlng technique ~n fulfill~ngthe com-
*Poroslty ~ n d e xIS defined as the product of fractional water satura-
mlttee's objectives. tlon tlmes poroslty

Table 13
Spectral Analysis of Gamma-ray Pit Samples as Performed by Three Laboratories

Potassium, Percent Uranium, Ppm

--- - Thorium, Ppm

7 a
%
Q)
M bL
A B C 2 A B C 2 A B -C I
$ : <
Depths, Ft
4.27 4.24
-4
426
-
446
-
59
4
5 18 22.4 29.0 25.7
TOP
1 4.31 3 97 4 00 4 09 7.03 7.5 4.5 6 34 24.5 24 3 25 2 24 7
2 3 97 4.27 4.00 4.08 4.83 4.4 36 4.28 22 1 26 6 24 0 24.2
3 4 06 4.28 3 90 4.08 11.80 12.6 11 1 11 83 21 3 25 7 23 8 23 6
4 4 21 3 91 4 00 4.04 10 30 11.8 12 2 11 43 24.0 25.4 21.4 23.6
5 4 06 3.92 3 90 3 96 11 10 13.6 13.2 12.63 21.4 23 7 20 7 21 9
6 370 3.57 4.10 370 886 14.7 95 11.02 19.0 22.9 22.3 21.4
7 3 99 3 99 3.70 3.89 11.85 12 9 15 1 13 28 22.1 27 4 25.8 25.1
7% 446 4.41 4.00 4.29 5.67 9.5 36 626 21.6 28.4 23.4 245
Bottom 4.47 4.51 4 20 4.39 3 79 60 39 4.56 26 6 29.8 27 6 28 0
 FACILITY
A P I CALIBRATION FOR NUCLEARLOGS 307

I
level) was therefore selected a s the officlal calibration
polnt f o r the zone. Shown a s F i g 6 IS a computed curve
of total radloactivlty obtalned by weighting the U, Th,
and K concentrat~onsaccording to t h e ~ rspeclfic activity
a s determined froin Table 6 . Thls approslmates the
ielatlve response expected to be obtained froin a n aver-
age logglng instrument.
After careful consideration of these data, the Sub-
committee felt justified in assigning the offic~alcall-
bratlon point 111 the zone the following absolute values
of concentratlon of the three elements:
U - 13 ppm; Th - 24 ppm; K- 4 percent.
To confirm the adequacy of the zone In fulfilling the
Fig. 5-U, Th, and K Content of Samples Taken baslc objective, three servlce compames logged t h e
well measuring radlatlon levels with their respective
from the Gamma-ray Pit as Determined by
u n ~ t sa s piesently used The results a r e the following:
Gamma-ray Spectroscopy
Average
Low-activity Hlgh-actlvlty Shale from
analysis p e i f o ~ m e dby three oil-company laboratories Company Zone Zone Field Logs
a r e shown In Table 13. These measurements a l e also
plotted ln Flg. 5 Comparison of these measurements a t
1-ft Intervals with antlclpated average measurements
f o r the whole zone (froin Table 9 ) indicates close
agreement f o r I( and Th with u n ~ f o r nconcentratlon
~
of these elements throughout the depth of the zone. This The activity in the callbrat~onzone IS thus approxi-
IS not true for the U component whlch, from the sample
mately twice t h a t designated by the servlce companies
analys~s,IS found to be substantially lower than d e s ~ r e d to be obtained in a n average shale.
In the upper 2 f t and lower 1 ft. This is not well- Slnce, by A P I definition, the response of a logging
understood, but is belleved to be partially caused by a instrument to the h ~ g h - a c t l v ~ tzone
y mlnus the response
mechanical fallure of the cement-mls~ng equlpnlent In the low-actlvlty zone, is assigned the value of 200
which allowed an undetermined amount of escess water A P I Gamma-Ray Units, ~t may be expected t h a t field
to be added durlng the pourlng of the upper few feet logs w ~ l show
l shales, on a n average, to be about one-half
Some of the Ra was probably washed from the sand thls ~ntenslty,o r 100 A P I Gamma-Ray Units
and removed wlth the excess water. Fortunately, a rela- Thus the gamma-ray pit, by vlrtue of determination of
t ~ v e l yumform a c t l v ~ t yf o r each element is indicated In its baslc radiation properties and assignment of stand-
the center region of the sectlon, and was subsequently a r d unlts to the response of instruments to these prop-
verlfied by "loggmg" checks. Thls region (I e., the 4-ft erties, truly just~fiesits classification a s a n "absolute"
a s well a s "arbitrary" Industry standard.
TOP -
The Neutron P i t
I - I n determination of porosity-index values to be
assigned to the three zones In the neutron pit, two
sets of measurements were available to the Subcom-
w 2 -
Z mittee - one from data acqulred during saturat!on of
2 the large blocks and the other from core analysis of
LL 3 -
0
a
the small samples removed from the comers and centers
0
+ 4 -
of the large blocks It had been previously agreed by
I the Subcoinmlttee that, In case of discrepancy between
0
5 .
the two measurements, the large-block data should be
I considered more applicable. The former have been pre-
+
sented 111 Table 12.
6 .
F o r analysis of the small samples submitted to the
7 . varlous 011-company laboratories, each was requested to:
1 Measure poroslty of each of the 90 samples utiliz~ng
8 their best technique.
I I I I I I I I I I I 2. Measure poroslty Index, using t a p water, on a t
4 5 6 7 8 9 10 1.1 12 13 least 40 percent of the samples.
PHOTONS/SEC-GM OF M I X ( W I T H ENERGY >IOOKEV
These measurements a r e glven In Table 14. A description
Fig. 6-Radioactivity of Gamma-ray Pit (Calculated of the analysls techniclue used by each laboratory IS
Using Specific Activities Given in Table 6) inclitdcd In Appendlx B, p 317.
- ---
0
A
03
m
w N
*
0
N
N N

a m
w N
0.1

0
N

40.1
*
m

N *
01 0.1

0 rl
5 4
NO.l 01
C U

0 w
2 0
s
N m

*
m
(3
m
0.1
0.1c

0
w *
m
-7
m 0.1 4
u)

--
?<
0 0
0 3 II
N c , \
0 * w 4
t : - 0
N C \ I
I
m
V
'R
t- 0 C(
C- a
N7-4 II
-CO a
4
m
A N E
2 0.1
0

0.10-
t- c
CO

m
mwoq
hlNA
a s
E
O
w
N $
4

N T
V
A O C - 4
mwC- U
0.1N4, 9
Q
r l N
0.1
m

0 C-

-
:: C-

0
C:
0.1

0 Q,
m m
m
2
0
X
rl

."
* EZW

+
22
m
. m
&
2
 Carthage Marble (continued)
Posltlon 1 2 3 4 5
Porosity P.I. Porosity P.I. Poroslty P.I. Poroslty P.I. Poroslty
Block 5
L R l L I R L I R L I R L R l L l R L I R l L R L I R
T 1.67 1.29 1.71 1.60 1.67 120 1.40 1.72 1 69 1 71
Layer 170 150 1.68 2.54 1845 201 250 205 230 181 160 1 80
1 1 1 1.90 150 1 1.69 1.70 1 1 6 2 1.83 1 1415 1 178 I 2 50 1 1 2 74 190 1 180
Averages 154 1 84 185 1.69 153 1.74 2 08 2.28 196 1 80
Block 5 A v e ~ a g e s Poroszty = 1.774 - P.Z. = 1 849
Block 6
T 170 1.40 3.08 1 50 1 52 2 36 150 175 2.30
Layer 190 2 10 163 1.80 150 1.56 1.735 2 21 1965
5
1.61 162 170 1.66 176 2 09 14 8 5 1.50 125 5 20 1.45 1 7 0 1.83 190
E
Averages
1 g 1 ?1: 1 1.66 1 67
1
2.05
1
1 72
1
1 84 160
1
2.58 1.57
1 1
187
1
2.06 m
P
>
Block 6 Averages: Porosaty = 2.013 -P.Z. = 1.712 2
6 C a r t h g e Marble Blocks, Averages: Porosity = 1.884 -P.Z. = 1.829 o
z
Indiana Limestone '4
*
Block 7 2
E
T 198 200 19.9 18 9 19 42 17 5 18.1 19 3 1 8 2 19 1 19 1 19.9 19 6
Layer 1 1 18 6 18 1 1 18.2 19 0 lo 1 0 19.0 19
". 18 2 1 18 3 19.43 1 8 55 18.4
1 1 1 8 75 2z
18 8 18 85 18.6 19 3 19 2 19.0 18 8 18.9 19 2 :'i 184
z
Averages 19.21 18.70 19.30
Block 7 Averages
19 37 18 96
Porosztg = 19.1-7 --
18.20
P.Z. = 18.75
18 93 18.56 19 24
"118 80
5P
m
*
z
Block 8 t'
0
R
T 18.1 19 93 19 2 19.4 18.9 18 6 18 9 18.6 18.9 18 9 18.45 1 8 9 19 15 cn
Layer 1 19.3 27 0 1 , 1 18 56 18 2 1 17 3 21 19 6 19.4 19 5 19 2 1
18.45 :: 1 ::.:1 23.6 :i:i 1 17 17 18.8 17.55
5 19 0
4 bg 1
Block 9
T 18.43 18.65 19 0, 18.1 1 8 9 18 1 18.7 18.8 18.9 18.65 18 0 18.42 18 2 19.0 18 15
18 15 18.5 18 5
1; 2118,7 1184 1 ::!7188 " 5 1 7 :::I188 179118.7 ::::I94 "'189
Averages 19 21 18.78 18 39 18 45 19.07 18.51 1 8 41 18 26 19.15 18 81
Block 9 Averc~ges P o r o s ~ t y= 18.85 - P.I. = 18.55
 Table 14 (continued) 1E
Indiana Limesto~le(continued)
Position I 1 2 I I 4 I 5 I
Poros~ty P.I. Porosity P.I. Poroslty P.I. Porosity P I. Porosity P.I.
ppppp-
Block 10
L R L R L R L R L R L R L R L R L R L R
- - - - --- - --- - - - - - - - - -
T 196 192 19.1 18 0 17 8 19 52 18 6 19.5 20 6 19 9 20 3 19 6 19.6 19.5
- Layer M 18.45 18 1 18 95 19 8 20.0 19 7 18.5 17.75 1 8 2 7 19 1 18.7 .
B 19.8 20 2 19.0 18.0 20.0 19 2 19 9 19.1 18.5 18.6 19 2 18 8 19.45
Averages 19.44 1 8 79 19.27 18.50 19.31 19.28 19.19 19.07 19.30 19.22
E'
Block 10 A v e r a g e s . Poroszty = 19.31 -P.Z. = 18.98 g
Block 11 2
"d

T 192 18 8 19 1 18 25 17.1 19.1 18 9 18 3 18.3 18.3 S

19.8 20 0 17 15 17.8 17.3
1; 1 9 6 7E'1
9",,,!,,,,,,,),,1~1
-8.8:: :ai8.41;;::5
5
Averages 19.67 18.87 19.18 19.16 1 8 24 18.28 18.87 18.70 . 18.85 18.04'
n
Block 11 Awerages. Poroszty = 18.93 -P.Z. = 18.57 X
2
cj
Block 12
T 20 5 19 ti 19.5 l8.6 19.8 18 7 19 0 19 85 19.4 19.4
E
194 5
Layer 18 3 20.1 21.3 19.9 19 2 20.8 19 2 19 57 a
19.1 19 18.7 19'" 19 1 l9 "9.1 1 8 25 17 35 18.1 19.1 19.1 19 4 19.1 19 2
cj
Averages
( 1: 19.36
1 1
19.23 19.33 18.85 19 66
1 1
18.45
::::1
19.29
(
19.28
1
19.63
1
19.39
j
M

Block 12 A v e r a g e s . P o r o s ~ t y= 19.45 -P.I. = 19.0.5 FAl

6 Indiana h m e s t o n e Blocks, Averccges: Porostty = 19.23 -P.Z. = 18.78 v1
0
2
Aust~nLimestone
>
Block 1 3
5
T 23 8 24.3 24 1 26 7 28 2 26 G 27.3 27 6 24.0 27.6 24 0 26 5 27.4 272
21.7 26.7 25 0 24.1 24 9 23 8 23 9 22.1 1 26'0
28.9 . 31.2, 30.9 30.1 29 6 24 9 :if 24.3 24.6 2:7
":'
1 b: 1 1 1 1 1 :I 1 1 1 1 '2
Averages 27.49 25 93 26.68 27.10 26.20 26 38 25 26 24.40 26 58 25 25
Block 13 A v e r a g e s . Porostty = 26.49 - P.I. = 25.81
Block 1 4
T 27 8 26.9 25.6 25 9 28 4 26.8 26.8 28 4 28.3 29.2 26.6 27.9
y e 1: 1 26 2 27 3 31 2 28 29 2- 25.9 1 27 27.7 27 4 1 29 1 27.2 1
34.8 2: 1 29 0
27.3 29 3 1 28 8 30 0
29.4 L11 1 33.2 30 8 32 0 32.3
Averages 29.03 28.90 28 75 27 73 29 40
Block 14 Averages . P o r o s ~ t y= 88.82 - P.Z. = 28.73
28.13 28 8 3
" 29.70 28.08 29.13
API CALIBRATION
FACILITY
FOR NUCLEAR
LOGS 311
 CARTRACE WRlLE AUSTIN LIULSmNE
I t IS ~ n t e r e s t i n gto compare these carefully determined
values f o r the three types of stones with values cur-
rently assigned similar type stones 111 servlce-company
test plts F o r ~nstance,Carthage marble, here deter-
mined to be 1.9 pelcent has carried values from 1
percent to 3.5 percent in such privately owned plts,
wlth s i m ~ l a r differences for the other stone types
Now, through use of logglng ~ n s t r u m e n t scallhrated in
t h e A P I pit, ~t wlll he possible f o r servlce compames
to more accurately establish porosity-nldex values f o r
slmllar zones in their own pits. This w ~ l l serve the
whole industry In providing means f o r clerlv~ngmore
accurate charts relat!ng log response to format1011
POROSITY - PERCENT -
P W O S 1 T I PERCENT POROSITY-PERCENT
5
poroslty index o r porosity.
Fig. 7-Porosity Distributions from Analyses of VII. OPERATION O F T H E FACILITY
Small Samples Taken from the Corners and
Operating Agreement
Centers of Large Blocks
Operation of the callhrat~onf a c ~ l ~ was t y begun Imme-
I t I S interesting to note the geneially good agreement dlately following formal opening on J u n e 24, 1950, under
of measured poroslty values a s submitted by the d~ffer- contractual agreement mlth the University of Houston
ent laboratories using varlous techniques, and t h e very Under tlils agreement, the U n l v e r s ~ t yprovides personnel
unlform poroslty character~sticsof the I n d ~ a n alime- and servlces as necessary to the operation of t h e faclhty.
stone w h ~ c h was chosen a s the offic~al cahbratlon This Includes techn~cal consultation and d~rectlon, a
environment Close agreement between measured poros- quahfied observer to witness and certlfy calihrat~ons,
i t y a n d p o r o s ~ t y - i n d e x v a l u e s indicates n e a r l y maintenance to assure full serviceability of f a c ~ l ~ tand g,
100-percent water s a t u r a t ~ o n of the small samples secretarlal and account~ngservlces
I n F i g 7, these porosity data a r e plotted In graphical I n ~ t i a lfees for use of the c a l ~ b r a t ~ ofna c i l ~ t ywere
form vs. the number of samples f o r determinat~onof set at $15 per hour o r major p o r t ~ o nthereof, and $7.50
mean poroslty values f o r each stone type. per minor port1011 The fee is u n ~ f o r ~f no r all callbra-
F o r easy comparison of porosity-index values deter- t ~ o n sbut
, is subject to period~cadlustment by agreement
mined from the small samples and the large blocks, between the U n i v e ~ s l t yand Institute.
Table 16 IS presented Blocks a r e listed in Col. 1, 111 Subject to prior approval 1)y the A P I Suhcomm~ttee,
the order 111 which they a r e stacked in the pit. Of the University is autl~orlzed to p e r m ~ tusage of t h e
particular importance to the Subcomm~tteeIn assign- f a c i l ~ t yf o r purposes other than those whlch a r e pur-
ment of poros~ty-indexvalues to the zones were the suant to APZ RP 35, and to charge such fees a s a r e
values determined from s a t u r a t ~ o nmeasurements of agreed upon by the Unlverslty and the Subcommittee.
the groups of large blocks, a s tabulated following. The University is further authorized to use t h e f a c l l ~ t y
Poroslty Index, Percent for purposes of ~nstruction, experimentation, o r re-
search. All such usage IS subord~nateto requirements
Group 1 Gronn 2
Carthage marble 1.829 1881 of ind~vidualso r companies desiring service pursuant
Indiana l~mestone 19.10 19 07 to APZ R P 33.
Austin limestone 26 37 25 55 Llmitatlons a r e placed on usage of the callbration prts
The very small d~fferencesbetween measurements of t h e to prevent a n y posslble damage or dev~atlon of t h e
Carthage and I n d ~ a n ablocks, respect~vely,confirms the standard calibration No mod~ficat~on of the plts wlll
adequacy of t h e s a t u r a t ~ o ntechmque used, and further be allowed t h a t I S not completely and ~mmedlately
Indicates good unlfoimity of porosity-~ndex values , removable
between individual blocks of a type The sllghtly h ~ g h e r The University I S guaranteed a mlnlnium compensa-
d~fferencebetween measurements of the A u s t ~ nblocks tlon for o p e r a t ~ n gthe cal~hratlon facllltp durlng the
1s believed caused 1)y v a r ~ a t i o n sIn porosity character- first year of o p e r a t ~ o n The guarantee is $6,780. The
l s t ~ c sof the ~ndividualblocks. T h ~ sis substantlatea by A P I oligmally made the guarant.ee; ~twas subsequentlv
"sample" measurements of the ~ndlvldual blocks in underwritten by the l o g g ~ n gcompanies usmg the call-
which values of porosity lndes vary from 2.5.08 to 28.73. h r a t ~ o nfacll~ty.
From these measurements and with cons~deration An A P I Subcommittee of five members and a repre-
to their llmits of accuracy, the three zones mere s e n t a t ~ v efrom the Univers~tyof Houston was estah-
ass~gnedthe following values of poroslty Index by the llshed to admlnlster the operation of the f a c ~ l ~ t The y
Subcommittee: contractual agreement w ~ t hthe U n ~ v e r s l t yIS suhlect to
Carthage marble - 1.9 percent revlew semi-annually or a t any t ~ m eon request of
Indlana limestone - 19 percent = 1,000 API
Neutron Units
, either party. P n o r t o each revlew, the U n ~ v e i s l t y I S
required t o submit a financ~alreport to serve a s a hasls
Austin limestone - 26 percent 1 for revlslon of c a h b r a t ~ o nfees and alteratioll of such
 FACILITYFOR NUCLEARLOGS
A P l CALIBRATION 313

Table 15
Final Tabulated Data Neutron Pit -
C M = Carthage Marble; IL Indiana Limestone, AL = Austin Limestone
I
Block No., Type, Core A;al y sis, Core Analysis, Final Graphical Mean,
and Relat~ve Numerical Average Numerlcal Average for Saturation Each 6-block Group,
Poslt~onin f o r Each Block, Each 3 Blocks a s Results of Results of 5 Laboratories
Neutron Plt Results of 5 Saturated, Results Large Plt Plotted on D l s t r ~ b u t ~ o n
Surface Down Laboratories of 5 Laboratories Blocks Graph
P.I., P.I., P.I.,
Percent Percent Percent Percent Percent Percent Percent

Average All
6 Bloclts

Average All
6 Blocks
NOTE
1 I 1
P I = poros~tyIndex defined as the product of the water saturation and the poros~ty.
25 96 1 26 196

& = poroelty
Average Graln Density. Carthage Marble (CM) = 2 694 g m per cc:
Indlana Llrnestone (IL) = 2 688 g m per cc; Austrn Llrnestone (AL) = 2 707 g m per cc

other telms, cond~tions, and procedures a s heco111e after cahbrator reading, and a final instrument zero.
necessary After calibration on the surface, two decentralized runs
Procedure for Logging Calibration Pits of the gamma-ray logging tool- a r e made 111 the gamma-
The purpose of the A P I c a l ~ b r a t ~ o1ns to assign to r a y callbration pit from the bottom to the top of the
a logging company's field calibrator a specific number plt. Each r u n ~ncludesa continuous recording of the
of A P I units a s determined by t h e relative responses of instrument zero, log deflect~onfor the low-rad~oactiv~ty
the company's l o g g ~ n gtool in t h a t cahbrator and In the concrete, the radioactive concrete, the upper section of
c a l ~ b r a t ~ oplts
n low-rad~oactivityconcrete, and a final instrument zero.
Before lowering the loggmg tool i n either c a l ~ b r a t ~ o n The logging tool 1s stopped for a readlng oppos~tethe
p ~ t the
, tool should be cahbrated using the logglng com- center of the radioactive-concrete section If deslred, the
pany's field cahhrator. The c a h b r a t ~ o nw ~ t hthe field reading made while the tool is stopped a t the center of
callbrator f o r a gamma-ray tool includes a n i n ~ t i a l t h e radioactive-concrete sect~onmay be made a f t e r the
nlstrument zero, gamma-ray background 111 alr, gamma- continuous and repeat runs, thus allow~ngthe two logs
r a y callbrator reading, gamma-ray background in a i r of the plt to be continuous Follow~ngthe logging runs
314 BELKNAP,DEWAN,KIRKPATRICK,
MOTT,PEARSON,
A N D RABSON

in the plt, the gamma-ray tool response with the field

callbrator is again recorded. Fig. 8 shows a portion of a
typical gamma-ray log callbration.
A P I callbratlon of neutron logging tools includes a
recording of tool response using the logging company's
field calibrator before and after logging. This consists
of initla1 ~ n s t r u m e n tzero, neutron background 111 air,
neutron calibrator deflection, and final ~ n s t r u m e n tzero.
Some calibrators have been designed for two callbration
readings. I n this case, both callbration readlngs may be
recorded instead of the one. Two runs a r e made In the
neutron log calibration pit with the logging tool decen-
tralized. Both runs a r e made from the bottom to top of
the plt and ~ncludea recording of lnstrunlent zero, the
three llmestone zones, the water shield, and a final
instrument zero. The logglng tool is stopped opposlte
the center of the Indiana llmestone f o r the calibration
reading. Thls r e a d ~ n gmay be made a f t e r the logging
runs, thus allowing the callbration runs to be contunuous
Fig. 9 shows a portion of a typlcal neutron log
calibratlon.
Llmitatlons a r e placed on the speed for running tools
in o r out of the neutron pit. It 1s preferred t h a t the
crane be used Instead of loggng-truck wlnches. A
maximum speed of 1 6 f t per min is specified No logging
tool o r other device is allowed in either the gamma-ray
o r neutron callbration p ~ w t h ~ c hwould impair their
usefulness a s a prnnary calibrat~onstandard.
Relating of Field Calibrations t o API Units
The foregoing procedure calibrates both gamma-ray
and neutron field callbrators in A P I unlts f o r speclfic
tool types Experience Indicates t h a t gamma-ray cali-
bratois in present use may readily be converted to A P I
Gamma-Ray Unlts. Conversion f o r neutron callbrators
is also straight-forward Once the values In A P I units
for the respective gamma-ray and neutron field call-
, brators have been determined, each callbrator can be
used to calibrate the logging tools directly In A P I
Gamma-Ray o r Neutron Units. I n the changeover period
from existing log units of measure to A P I units, some
l o g g ~ n gcompanies may use conversion factors to convert
their old units to A P I units. However, most companies
have indicated they will swltch directly to calibratlon In
A P I units, because they anticipate fewer errors in
callbration by doing so
No serious problems should be encountered if ~t I S
desired to convert a n old log to A P I unlts, provided
the old log was reliably cal~bratedto some other u n ~ t s
and the equivalent A P I units a r e known.
Maintenance of Calibration Records
R P 33 provides t h a t the U n i v e r s ~ t yof Houston shall
keep records of all callbrations on a prescr~bedfoinm
I n order for a calibration to be considered official, the
form must be complete and t h e calibration log attached.
Logglng companies a r e privileged to withhold record-
ings w h ~ c hthey d e s ~ r eto designate a s unofficial and
confidential.
The University is required to maintaln a file of all
Fig. 8-Typical API Gamma-ray Log Calibration logs designated a s official calibrations. This file is not
 First Six Months of Operation
Durlng the first six months of operation of the call-
bratlon facility - from July 1, 1959 to J a n u a r y 1, 1960
- 10 l o g g ~ n gcoml~aniescompleted and filed official A P I
callbrations of nuclear logglng tools a t the University.
It is anticipated these companies wlll convert thew
nuclear logs to A P I standards by mld-1960.
The financlng of operat1011 of the f a c ~ l l t yh a s worked
out a s est~matedby the Subcommittee. I t appears t h a t
the o p e r a t ~ o nwlll break even f o r the first year a t the
rates estabhshed.
VIII. CONCLUDING REMARKS
The A P I Nuclear Calibrat~onFacihty was des~gned
and b u ~ l tf o r one purpose: To p r o v ~ d et h e petroleum
Industry wlth a means for obtalnlng standardized
gamma-ray and neutron logs.
The first and one of the most Important benefits of
standardization will be the d ~ r e c tcomparison of logs
r u n by various logglng companies. The engineer *or
geologist (working on the well slte) can quantitatively
compare the log on his well with the log on a n offset
well. W ~ t hproper c o n s ~ d e r a t ~ oofn well-bore cond~tions
and tool response, h e will be able to tell from the nuclear
logs if and how formation cond~tionshave changed
between wells.
A standard u n ~ IS t essential before nuclear logging
can truly progress from a qualitative to a quantitative
a r t Its use should promote many s t u d ~ e s t h a t w ~ l l
Increase the.knowledge and quantitative use of nuclear
logs. F o r example, only prehminary work has been done
to determine porosity of a shaly forlnatlon from a
combination of the gamma-ray and neutron curves. A
standard unit wlll provlde a b a s s for such studles
Wlth standardized nuclear logs, research s t u d ~ e s of
depositional changes in a f o ~ m a t l o nover a geoloac
basin may be possible.
One by-product of standard~zationwill be improved
quality in nuclear logs. Because of the varlation in
u n ~ t s logs
, have been compared by appearance - a s a t ~ s -
factory log w a s one' t h a t "looked" all rlght Wlth a
standard unit those logs t h a t have not been properly
cahbrated, scaled, etc wlll be r e a d ~ l yapparent and they
will not be accepted by the well operator I n addition,
standardizat~onwlll p e r m ~ tquantitat~vecomparison of
various types and models of gamma-ray and neutron
Instruments.
Although the Calibrat~onFacllity was not primarily
designed to provide departure curves, the neutron pit
provldes some data for one response curve f o r each
tool calibrated. This curve will provide the logging
companies with a means of v e r ~ f y i n gthe values assigned
to their own test formations. F o r those companies t h a t
Fig. 9-Typical API Neutron Log Calibration do not have test pits, t h e Calibration Facihty will pro-
vide valuable response curves Also, wlth certain restric-
tions, the pits may be used for research and development.
open f o r ~nspection.Requests for callbration data should I n summary, the A P I Nuclear Callbration Facjllty
be made d~rectlyto the logglng company involved, not should lead to better nuclear logs and increased knowl-
to the Unlverslty. The University wlll verify calibration edge of nuclear l o g g ~ n gMost ~rnpol-tant,~tw ~ l provide
l
logs, but will not f u r n ~ s hcoples of logs the basis f o r truly q u a n t i t a t ~ v enuclear logs
 A t present t h e Callbration F a c ~ l i t ydoes not provide The Umverslty has the r ~ g h tto use the pits f o r t h ~ s
the range of conditions t h a t a r e needed to prepare a purpose when they a r e not in use f o r calibrat~on.Use
complete set of neutron response curves. F o r example, of the F a c ~ l i t yf o r Unlvers~tyresearch 1s expected t o be
~t u~oulcl be desirable to have pits: 1, saturated with of value In the coming years.
salt water, 2 , with d~fferenthole sizes; 5,t h a t could be
cased; 4, t h a t could be filled with mud of varying ACKNOWLEDGMENT
density, etc Many logging companies have already bulk
such p ~ t sThe A P I h a s no present plans t o hulld addl- So many have contrlbuted to the A P I Nucleai Log
t ~ o n a lp ~ t s but
, they could be added to the Facility qulte Callbration Facillty t h a t a n y acknowledgment must be
econonucally Perhalis, through the cooperation of sev- ~ncomplete.The men (and t h e ~ r1-espect~vecompanies)
eral companles, ~t w ~ l l be poss~ble to work out a n who served on the Subcommittee to R e v ~ e wAPZ R P 33,
agreement whereby additional p ~ t scan be built. I t is the compantes which contr~butedfunds to bulld t h e pits,
not d~fficultto v~suallzea complete set of plts a t the plus many others who freely f u r n ~ s h e dexpert a d v ~ c eon
Facillty a t some f u t u r e date. Complete response curves c e r t a ~ n phases of the project have all contributed
based on common test plts w ~ t hcarefully determined ~mmeasurably.
properties would be valuable to all Those organizat~onswhich contrlbuted special services
I11 addttion, t h e Callbratlon Facility may be used 111 were Gulf 011Corporation, Shell 011 Company, Humble
the future for calibration of other types of logs The 011 & Refining Company, The Atlantic Refin~ngCom-
present pits may be adequate for some aclclit~onaltypes pany, Schlumberger Well S u r v e y ~ n gCorporation, P a n
of logs - In other cases, new test plts may be needed Geo Atlas Corporation, Lane-Wells Company, and The
F o r example, the present neutron p ~ appears t appl~cable Univers~tyof Houston
f o r evaluation of acoust~cveloc~tylogs and density logs
The gamma-ray pit can conce~vably be used f o r a REFERENCES
gamma-ray spectroscopy standard 'Matt, W. E and E d ~ g e rN , M: Nuclear Well Logg~ilg
Nuclear logging IS stiil a relatively new sclence. Many In Petroleum Exploration and Production, Proc Fifth
improvements in present logs and many new ,types of World Petroleum Congress, X, 195 (1959).
logs a r e anticipated. I t is hoped t h a t the F a c i l ~ t ywlll ZBelknap, W. B: A P I Calibration and Standardizat~oii
a ~ din the developme~ltof such logs. of Nuclear Logs, presentecl a t the sprlng meetings of
The Callbratioil Facllity h a s already p1.ovecI its value the Mlcl-Continent and Rocky Mountain Districts, April
to the University of Houston a s a t e a c h ~ n gaid Student 22-24, 1959, and May 6-8, 1959, respectively. P e t ~ o l e l ~ , ) ~
help was used wherever poss~bleIn construction of the E n y z ~ t e w (adaptation, t ~ t l e . New A P I Factlity foi
Facllity. Soine phases required research and wlll be the Standardization and Callbration of Nuclear Logs) 31
subject of theses prepared for graduate degrees. Student [I31 B-24, Dec. (1959).
work on the Facihty during construct~onand operat~on 3Strominger, D ; Hollander, J. M ; and Seaborg, G. T
has had a n addlttonal benefit. Several students have Table of Isotopes, Rev. mod en^ PILYs., 30, 585 (1958)
been provided the financ~almeans for c o n t m u ~ n gt h e ~ r Yhttman, J a y : Neutron Logglng, Proc. U n i v e ~ s t t yof
eclucat~onand for obtalnlng advanced degrees There Kunsus Petrolezcm Engzneering Conference, A p r ~ l2-3,
a r e many ~)ossibilit~es for research using the F a c i l ~ t y 1956.

APPENDIX A
L ~ s t e d follow~ng IS the membership of the A P I H E. Schaller, McCullough Tool Co.
N a t ~ o n a l Subcommittee on Rev~ew of R P 73 a t the J. A Stinson, P a n Amencan Petroleum Corp
t ~ m eof puhl~cationof the revls~on. G11 Swift, Well Surveys, Inc
W. B Belknap, C ~ / L ~ / I ) I I * L ) I , Tei r y Walker, Welex, Inc.
W. 0 Winsauer, Humble 011& Refin~ngCo.
Phllllps Petroleum Company
A. B. Winters, Lane-Wells Company
J. M Bird, Seismograph S e r v ~ c eCol p.
The representation from spec~ficcompanles changed
J T Dewan, Schlumberger Well S u r v e y ~ n gCol p d u l ~ n gthe progress of the Subcommittee's work because
T. A. Johnson, Jr , Southern C a l ~ f o r n ~Gas
a Co of chahges In indlvldual assignments w ~ t h ~those
n com-
A. S McKay, Texaco, Inc. panles Recognition is also made of the contr~butionsof
W E Mott, Gulf Resealch & Development Co. the following persons to the work of the Subcommittee.
A J Pearson, The A t l a n t ~ cRefining Co. C L Doyle, General Petroleum Corp ; Thomas G11-
A A Pereb~nossoff,Mob11 011Company martin, P a n American Petroleum Corp.; Ben H Goocle,
W R. Rabson, P a n Geo Atlas Corp Lane-Wells Company; and R H Wlnn, Halliburton 011
G. T. N. Roberts, Shell 011 Company Well Cen~entlngCompany.
 FACILITY
A P I CALIBRATION FOR NUCLEAR
LOGS 317

APPENDIX B
LABORATORY CORE-ANALYSIS TECHNIQUES USED FOR
CORE ANALYSIS OF LIMESTONE BLOCKS IN NELTTRON
PIT AS SUBMITTED BY COMPANY LABORATORIES
COMPANY A submerged in de-aerated t a p water a t atmospheric
Core plugs (l-ln. long by %-in diameter) were drilled PleSsure f o r a t least 14 hours. The ~nduced welght
flom the limestone blocks, with t a p w a t e r used a s changes also were measured on the torslon balance
coolant The plugs were oven-drled f o r 24 hours a t All allalysls of the Houston city t a p watel 1s not
100 deg C. Aftei coollng, grain volumes weie d e t e r m ~ n e d available, ho\vever, the specific gravity was 10026
w1t.11 a pressure-type Boyles' Law a i r poroslmeter Fol- COMPANY C
l o w ~ n ga d r y welglit, the plugs were evacuated a t less
than 1 nlin mercury f o r 30 mln and then saturated with The porosity Index f o r each of the 90 samples w a s
determined 111 t h e following manner
t a p water The plugs were we~ghedw h ~ l esaturatecl wlth
1. Cyllndrlcal core plugs, 1 in. In diameter and 2 t o 4
t a p water and a g a m while suspended in t a p water. In. In length, were clnllecl from the p a r e n t core
The bulk volume w a s obtained by subtracting the samples using t a p water a s the circulating fluid.
susl)eiided weight from t h e saturated weight and cllvld- 2. The core plugs were drled 111 a n oven a t 120 cleg C.
Ing the difference by the tap-water d e n s ~ t y The. reported f o r 14 l ~ o u r s This temperature was above the
p3ioslty was calculated by subtractlng the grain volume specified maslmum of 105 deg C. Therefore, t h e
f ~ o n ibulk volume and d i v ~ d i n gthe diffe~enceby bulk cores were saturated w ~ t ht a p water and then
drled again a t 90 deg C.
v o l ~ ~ mThe e volume of water In the coie plug was found
3 The dried core plugs weie cooled to room teinpera-
by subtractlrig d r y weight from saturated welght and t u r e and the d r y weight of each sample w a s
g difference by t h e density of t a p w a t e r The
t l ~ v ~ d l nthe measured
1 atlo of this volume to bulk volume 1s the p o r o s ~ t yindex 4. The core plugs were then saturated with t a p w a t e r
A measuremint of porosity index is p a r t of our by flushing de-aerated t a p water mto the cores and
nnimal plocedure so t h a t we will know how well t h e c o n t i n u ~ n gto maintain a vacuum f o r 1 2 hours
before restoring atmospherlc pressure.
coles a r e saturatecl. We l ~ a v etherefole llsted thls value
5 The w e ~ g l l tof each sample when water-saturated
f o ~all of the core plugs ~ n s t e a dof only those ~ n d ~ c a t e d was then measured.
on the list Because of experimental error, the porosity G The pore volume f o r each core plug w a s calculated
~ n t l e s1s hlgher than the p o r o s ~ t y in some cases. We by d i v i d ~ n g t h e difference between t h e water-
belleve our pore-volume measurements a r e wlthin saturated and d r y weights by t h e d e n s ~ t yof the
tap water
k0.02 cc of the t r u e value. The maxlmum e r r o r f o r 7 The bulk volume f o r each core plug w a s calculated
either of the reported values i s therefore about 0.2 from measurements of the ~. h"v s l c a ldlrnens~onsof
p o i o s ~ t ypercent f o r core plugs of the size used. . the samples.
8 The poroslty nldex w a s calculated by dividlng t h e
COMPANY B pore volume by t h e bulk volume
The large triangular blocks s u p p l ~ e dwere cut into COMPANY D
iectangular blocks, using a tap-water lubr~cated,dia- Three cyhndrlcal core samples were drllled from each
mond cutting wheel; the smaller, split cyhndrlcal of the 90 large samples whlch were prov~ded The
samples were used 111 t h e condition furnlslied. P n o r t o samples w e i e c111lled with t a p water and dried a t
porosity measurement, all specimens were a ~ r - d r l e d 100 deg C.
a t 100-105 deg C The core plugs representing those samples on which
The best method of poroslty measurement conslsts of a porosity analysls with t a p w a t e r was requested were
the use of whole core equipment f o r g r a m - o r solids- evacuated to 20 microns mercury pressure and saturated
volume determlnatlon, followed by a water-d~splacement with de-aerated t a p water. The g r a i n volumes were
test to ascertain bulk volume A mod~ficatlon of t h e determined by the buoyant-force method. A mercury-
gas-expansion technique described by Coberly a n d
dlsplacement bulk-volume meter w a s used f o r t h e bulk-
Stevens was employed to measure g r a m volume. The volume deternilnatlons.
m o d ~ f i c a t ~ oconslsts
n p r ~ m a r ~ lofy t h e respectlve use of These samples were again d n e d a t 100 (leg C. and
d r y a l r and mercury manometers 111 lieu of hydrogen included with t h e remaining core plugs f o r grain-
arid pressure gages. Following solids measurement, t h e volume determinations uslng toluene a s the s a t u r a t ~ n g
samples were allowed to ~ m b ~ bfully e In t a p w a t e r and fluid. The same buoyant-force method was used f o r
subsequently were immersed while suspended ~ n t oa these determinations.
counterbalanced, water-filled' vessel resting on a t o r s ~ o n
balance. The volumetric d~splaceinentand bulk volume UNIVERSITY O F HOUSTON
of the core w a s then calculated from the resulting The University of Houston laboratory used the gas-
welght changes The t o r s ~ o nbalance used h a s a sensl- expansion method uslng the RUSKA mercury pump
tlvlty of 0 1 gram. f o r poroslty determ~natlons.Bulk-volun~emeasurements
F o r porosity-index pore-volume determinations, speci- were made by mercury dlsplacement. Checks by g r a m
mens were evacuated f o r approximately 6 hours a n d density were made period~cally.