GB2272525A - Determining pore pressure while drilling a borehole - Google Patents
Determining pore pressure while drilling a borehole Download PDFInfo
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- GB2272525A GB2272525A GB9223917A GB9223917A GB2272525A GB 2272525 A GB2272525 A GB 2272525A GB 9223917 A GB9223917 A GB 9223917A GB 9223917 A GB9223917 A GB 9223917A GB 2272525 A GB2272525 A GB 2272525A
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- clay
- porosity
- shale
- formation
- volume
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- 239000011148 porous material Substances 0.000 title claims abstract description 32
- 238000005553 drilling Methods 0.000 title claims abstract description 12
- 239000004927 clay Substances 0.000 claims abstract description 48
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 47
- 239000012530 fluid Substances 0.000 claims abstract description 29
- 239000002734 clay mineral Substances 0.000 claims abstract description 20
- 238000005259 measurement Methods 0.000 claims abstract description 20
- 230000005251 gamma ray Effects 0.000 claims abstract description 10
- 230000000694 effects Effects 0.000 claims abstract description 5
- 238000005056 compaction Methods 0.000 claims abstract description 4
- 230000001133 acceleration Effects 0.000 claims abstract description 3
- 238000009933 burial Methods 0.000 claims abstract description 3
- 238000000034 method Methods 0.000 claims description 29
- 230000004044 response Effects 0.000 claims description 15
- 229910052500 inorganic mineral Inorganic materials 0.000 claims description 7
- 239000011707 mineral Substances 0.000 claims description 7
- 239000011435 rock Substances 0.000 claims description 4
- 230000004913 activation Effects 0.000 claims description 3
- 230000006698 induction Effects 0.000 claims 1
- 230000035515 penetration Effects 0.000 claims 1
- 238000005755 formation reaction Methods 0.000 description 35
- 238000011156 evaluation Methods 0.000 description 5
- 230000002706 hydrostatic effect Effects 0.000 description 4
- 229930195733 hydrocarbon Natural products 0.000 description 3
- 150000002430 hydrocarbons Chemical class 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- 239000004215 Carbon black (E152) Substances 0.000 description 2
- 150000001768 cations Chemical class 0.000 description 2
- 230000004941 influx Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000004576 sand Substances 0.000 description 2
- 230000003595 spectral effect Effects 0.000 description 2
- 102100027611 Rho-related GTP-binding protein RhoB Human genes 0.000 description 1
- 101150054980 Rhob gene Proteins 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000005341 cation exchange Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- VAOCPAMSLUNLGC-UHFFFAOYSA-N metronidazole Chemical compound CC1=NC=C([N+]([O-])=O)N1CCO VAOCPAMSLUNLGC-UHFFFAOYSA-N 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- 238000005192 partition Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 230000000246 remedial effect Effects 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 239000012798 spherical particle Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000004448 titration Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/24—Earth materials
- G01N33/241—Earth materials for hydrocarbon content
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
- E21B47/06—Measuring temperature or pressure
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
- E21B49/003—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells by analysing drilling variables or conditions
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Geology (AREA)
- Mining & Mineral Resources (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Fluid Mechanics (AREA)
- Health & Medical Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Analytical Chemistry (AREA)
- Remote Sensing (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Geophysics (AREA)
- Biochemistry (AREA)
- Medicinal Chemistry (AREA)
- Food Science & Technology (AREA)
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
Abstract
Pore pressure Ppore of a subsurface formation is determined, while drilling a borehole, by measuring formation strength FS, resistivity RES and natural gamma ray activity GR. The measurement FS includes contributions of clay volume Vcl, non-clay mineral strength, and a porosity, the measurement RES includes contributions from a porosity, non-clay mineral volume Vsilt and pore fluid conductivity and the measurement GR includes contributions from clay and non-clay mineral, and the sum of Vcl, Vsilt and PHI eff ist 1. The contribution to the measurement of clay volume Vcl, non-clay mineral volume Vsilt, clay porosity PHI clay and effective porosity PHI eff are derived for the formation being drilled, the clay porosity PHI clay and effective porosity PHI eff being related by PHI eff = PHI clay(1 - Vsilt). The pore pressure Ppore is derived from the relationship PHI eff = PHI clay(0)[1-Vsilt(Z)]exp[-aPpore(Z)], wherein a=b DIVIDED (Pb-Pw)g and b = compaction coefficient at depth of interest Pb = density of shale Pw = density of pore fluid g = gravitational acceleration, 9.81 ms<-2> PHI eff = effective porosity PHI clay = clay porosity at zero depth of burial Vsilt = volume of non-clay mineral (silt) at depth of interest.
Description
PORE PRESSURE EVALUATION
The present invention relates to a method of formation evaluation for use in drilling hydrocarbon wells or the like in underground formations. in particular, the method provides a means for evaluating formation pore pressure from volumetric properties such as porosity in shale formations.
In the rotary drilling of hydrocarbon wells, drilling fluid or "mud" is circulated into the well through the drill string and returns to the surface via the annulus between the drill string and the borehole wall, bringing any rock cuttings with it. The mud also serves to exert a hydrostatic pressure on the formation to provide physical stability to the borehole and to balance any pressurised fluids in the formation being drilled so as to prevent their influx into the borehole. This latter function is important for well safety since if the formation fluid is a gas, the effect of an influx into the mud will be to reduce its density and hence the hydrostatic pressure exerted on the formation. This in turn will allow more fluid to flow into the well further reducing the density of the mud and if remedial action is not taken sufficiently quickly a blowout can occur.
However, it is also undesirable to exert too high a hydrostatic pressure on the formation since this can cause fracturing and formation damage due to fluid loss into the formation which is detrimental to the ability to produce hydrocarbons such as oil.
As will be appreciated from above, it is generally desirable to maintain the mud density such that the hydrostatic pressure balances the pressure of the fluids in the formation. Consequently, it is desirable to be able to evaluate this pressure, known as "pore pressure" while drilling is being conducted such that the density of the mud can be controlled continuously in an appropriate manner. Previously proposed methods of evaluating pore pressure, such as those described in US 4,833,914 and US 4,949,575 (incorporated herein by reference) rely on measurements made during drilling using
MWD technology and formation properties from formation evaluation while drilling or wireline logs.The measurements are interpreted to obtain a volumetric evaluation of the formation in the manner known as "GLOBAL" and described in US 4,338,664 which includes the porosity of the formation of interest since this is required to derive the pore pressure. The basic relationship used in this prior method to derive the effective porosity Q)I of the formation is:
clnul (1) where Q, is the porosity of sand with no clay present and V is the volume fraction of wet clay in the formation.
This interpretation relies on a model of a shaley sand to interpret the measurements. It is an object of the present invention to provide a method based on an alternative model so as to allow evaluation in cases where the prior technique is less appropriate. In the present invention, the model underlying the method is one of a shale having a proportion of silt (non-clay) material and the effective porosity is given by the relationship:
,ff = de,(l V,s,) (2) where #clay is the effective porosity of 100% clay at the depth or effective pressure of interest and V" is the volume fraction of non-clay materials.
In its broadest aspect, the present invention provides a method for determining the volumetric composition of a shale from its measured resistivity, wherein the measured resistivity RES is integrated according to the relationship:
1 Cshu dOeky (1Vnlt ) Psx wherein #skale is the shale resistivity, s-, is shale conductivity, #fluid is the pore fluid conductivity, m is the power law exponent, V,i" is the volume fraction of nonclay mineral, #clay is the effective porosity of 100% clay at the effective pressure of interest and is related to the effective porosity of the shale by the relationship::
4|ff OeZ Vnlt)
In accordance with an embodiment of the present invention, there is provided a method of determining the pore pressure PpO", of a subsurface formation while drilling a borehole, comprising measuring the formation strength FS, the resistivity
RES, and the natural gamma ray radioactivity GR so as to derive the contribution to the measurements of clay volume Vd, non-clay mineral volume V", clay porosity and and effective porosity #eff for the formation being drilled, wherein the clay porosity #clay and the effective porosity 4 > F are related according to the relationship = o(1 - Vat::) and wherein the measurement FS includes contributions of clay volume Ve" non-clay mineral strength, and a porosity, the measurement RES includes contributions from a porosity, non-clay mineral volume Vat: and pore fluid conductivity and the measurement GR includes contributions from clay and non-clay mineral, and the sum of Vcl, Vat:: and #eff being 1, the pore pressure P being derived from the relationship
o > d~( )[l - Vat'(Z)]expa?por(Z)], wherein
and b = compaction coefficient at depth of interest
Pb = density of shale
Pw = density of pore fluid g = gravitational acceleration, 9.81 ms-2 D,0 = effective porosity beg = clay porosity at zero depth of burial Vat: = volume of non-clay mineral (silt) at depth of interest.
The method according to the present invention is applicable to cases where the pore pressure or overpressure is related to the porosity of the formation being drilled.
Porosity is typically obtained from a nuclear log interpretation or optionally a resistivity log interpretation. Other suitable measurements typically include neutron porosity and total density.
In the present method, each measurement made of the formation is related to the constitution of the formation by an equation, often known as a tool response equation, which expresses the measurement obtained in terms of the volumetric components of the formation. The tool response equations, in combination with an equation which states that the sum of the volumes of all of the components is equal to one, are solved simultaneously by an incoherence minimisation technique to produce a volumetric analysis of the formation. The measured parameters are combined with other information which is known for the formation of interest eg compaction coefficient, typically obtained from tabulated data so as to enable the pore pressure to be determined.
The revised interpretation of shale resistivity provided by the present invention is related to the volumetric composition of the shale. The equation is based on a model of shale as a matrix of compacted clay, whose porosity is #clay, containing isolated spherical particles of silt:
1 = = CFJz eL y (3) Ps:':t: at: where p5 is shale resistivity, asklk is shale conductivity, #fluid is the pore fluid conductivity and m is the power-law exponent
The conductivity of the pore fluid is determined by first calculating its molarity which is then interpreted using tabulated ionic conductivity data and corrected for downhole temperature.
The simple method for calculation of total molarity is just to add the exchange ion molarity, calculated from CEC (cation exchange capacity for clay minerals) and porosity, to the deposition/equilibrium fluid molarity, and calculate conductivity on this basis. Using this route, the pore fluid molarity M,,,, is given by:
M =M Meiy + > (CECj-mj)-P,- rp '4 (4) pora aqM where Ms is the depositional or equilibrium fluid molarity, CECj and mj are respectively the CEC (equivalents/unit mass) and mass fraction of the i'th mineral in the clay matrix, and p, the mean density of the solid material in the clay matrix.In practice, Maqia is likely to be a free parameter which must be determined from appropriate cross plots. Its effect is, in many cases, small compared to that of the CEC term.
A more complex but more correct route is to use the Donnan theory of equilibrium of membranes to calculate pore fluid molarity. In relatively fresh fluids, the simpler route is adequate. Either way, the conductivity of the pore fluid will be dominated by the motion of cations (since the clay contains a large number of fixed macro-anions) and the appropriate tabulated ionic conductivities which can be obtained from tests on representative samples are preferred rather than simple molar conductivities. ff this data is limited, assumptions must be made about the partition of conductivity between cation and anion to obtain an estimated value.
The tabulated values are quoted for a temperature of, say, T,, and the value for a downhole temperature T can be approximated using an activation energy term Ea, ie,
= (T)=crs (To)-exp (S) The activation energy term Ea can be obtained from observing the variation in conductivity of fluid at differing temperatures and is known not to vary to any great degree over the scale of interest in this application. Consequently, a single representative value of Era can be obtained by experiment and applied generally in a region of investigation. The downhole temperature T is often difficult to measure directly but can be inferred from a determination of the geothermal gradient obtained from wells in the same region.Since the temperature T can have a significant effect, the best estimation of T is desirable.
The only remaining unknown in the resistivity equation is the power-law exponent m. This is known to vary with clay mineralogy, but can be estimated over an interval from a cross-plot of
log apujd-(l - Vagi, )1.5 against log (6) Any other depth-varying data, log-derived or otherwise, can be incorporated into the 'GLOBAL' processing method. For example, in addition to gamma-ray, formation strength and resistivity required for the method of the present invention and the pore pressure determination described in U.S. patent 4,949,575 the response equations for neutron porosity and gamma density can also be used and can be applied usefully to the method of the present invention.The basic response equations are respectively:
where GR is total gamma-ray response, Vi is the volume fraction of mineral i in the rock, and GRi is the gamma-ray response of that mineral in the absence of the others (if spectral gamma-ray data is available, then a similar set of mineral based response equations can be written for each energy window recorded by the tool, e.g.K, U and
Th decay, which give a more detailed set of inputs to the optimization procedure);
FS=FSlVd clnyrrm where FS is formation strength (derived from MWD drilling parameters and normalized for variations in mud and pore pressures), FS",g is the formation strength of the non-clay mineral, V is the volume of wet clay in the formation, Oetay is the clay porosity, and the quantities with 'zero' subscripts are the values of these parameters, picked from cross-plots, at which the formation strength falls to zero;
where NPHI is the total neutron porosity response, and PN;; and Vi are respectively the neutron porosity response and the volume fraction in the formation of the i'th component of the formation (these components are pore fluid, the various silts and clays making up the shale, and organic matter);
where RHOB is the total density response, and RHOMB, is the density response of the itth component as above.
The GLOBAL method allows these and other available logs or similar data to be combined in the volumetrics determination, provided a suitable response equation exists. Logs which provide mineralogical discrimination such as spectral garnma-ray and photoelectric cross-section are particularly useful for the present method; for example, resolution of total clay into distinct clay minerals can give a better value for
CEC of the rock, and hence make the resistivity equation, which is sensitive to this parameter, a more effective input in the volumetrics process. By placing a volumetric constraint on the formation responses, violation of the constraint causes the incoherence determined by GLOBAL to increase which in turn causes the minimisation to bring the volumetrical values back into the constrained levels. A continuity constraint can also be included to prevent wild fluctuations in calculated values in adjacent depths which can further improve the calculated results.
Claims (10)
1 A method of determining the pore pressure Ppore of a subsurface formation
while drilling a borehole, comprising deriving the contribution to the
measurements of clay volume Vcl, non-clay mineral volume V, clay porosity #clay and effective porosity ,.T for the formation being drilled, wherein the
clay porosity #clay and the effective porosity , are related according to the
relationship #eff = #clay (1 - V silt) by measuring the formation strength FS, the resistivity RES, and the natural
gamma ray radioactivity GR and wherein the measurement FS includes
contributions of clay volume V01, non-clay mineral strength, and a porosity, the
measurement RES includes contributions from a porosity, non-clay mineral
volume v and pore fluid conductivity and the measurement GR includes contributions from clay and non-clay mineral, and the sum of Vcl, Vsilt and #eff being 1, the pore pressure PpO" being derived from the relationship
= = < > dqy crrry(O)l-Vna(z)lexF aP,,(z) wherein
and
b = compaction coefficient at depth of interest
Pb = density of shale
Pw = density of pore fluid
g = gravitational acceleration, 9.81 ms-2 = effective porosity
= = clay porosity at zero depth of burial V1iit = volume of non-clay mineral (silt) at depth of interest.
2 A method as claimed in claim 1, wherein the formation strength (FS) is derived
from measurements of downhole bit torque (TOR) and downhole weight on bit
(WOB) and where said formation strength is corrected for the effects of bit
wear.
3 A method as claimed in claim 1 or 2, wherein
FS = FSstl V S) eAro elvero where FS is formation strength, FS"", is the formation strength of the non-clay
mineral, V is the volume of wet clay in the formation, ?e~ is the clay
porosity, and the quantities with 'zero' subscripts are the values of the
parameters at which the formation strength falls to zero.
4 A method as claimed in any preceding claim, wherein
where GR is total gamma-ray response, Vi is the volume fraction of mineral i in
the rock, and GRi is the gamma-ray response of that mineral in the absence of
any others.
5 A method as claimed in any preceding claim, wherein
1 =c=acM(lV )1.5 1 (T56 filadáW (1 V5i" ) P5aJ where p= is shale resistivity, vS is shale conductivity, #fluid is the pore fluid conductivity and m is the power-law exponent.
6 A method as claimed in claim 5, wherein, for a temperature (T),
= (T)= < Twxd(To)expR where ar} (TO) is the pore fluid conductivity at a temperature To, Ea is an
activation energy term and R is the gas constant.
7 A method as claimed in claim 5 or 6, wherein the power law exponent n is
obtained from a cross-plot of
log (;^^V log - v11)L5 against
8 A method as claimed in any preceding claim further including measurement of
one or more of neutron porosity, gamma ray density, sonic travel time deep
induction resistivity and resistivity at bit
9 A method as claimed in any preceding claim, wherein FS is derived as a
function of rate of bit rotation, bit efficiency, gouging component of bit torque,
rate of penetration, bit diameter and drilling mud weight.
10 A method of determining the volumetric composition of a shale comprising
relating the effective prorosity , of the shale to the porosity of 100% clay at
the pressure of interest #clay according to the relationship:
ff = oC,~ (1V5", ) wherein Vat: is the volume fraction of non-clay mineral and measuring the resistivity RES of the shale which is interpreted according to the relationship:
= = idew a Vnlt) P5hak wherein #shale is the shale resistivity, #shale is shale conductivity, #fluid is the pore fluid conductivity and m is the power law exponent.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9223917A GB2272525A (en) | 1992-11-14 | 1992-11-14 | Determining pore pressure while drilling a borehole |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9223917A GB2272525A (en) | 1992-11-14 | 1992-11-14 | Determining pore pressure while drilling a borehole |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9223917D0 GB9223917D0 (en) | 1993-01-06 |
| GB2272525A true GB2272525A (en) | 1994-05-18 |
Family
ID=10725103
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9223917A Withdrawn GB2272525A (en) | 1992-11-14 | 1992-11-14 | Determining pore pressure while drilling a borehole |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2272525A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2380802A (en) * | 2001-10-12 | 2003-04-16 | Schlumberger Holdings | Pore pressure monitoring |
| CN102748016A (en) * | 2012-07-10 | 2012-10-24 | 中国石油大学(华东) | Geologic history period sandstone reservoir porosity evolution recovery method |
| CN103806855A (en) * | 2014-02-07 | 2014-05-21 | 中国海洋石油总公司 | Method for determining density of drilling fluid of extremely-thick rock salt stratum |
| US8995224B2 (en) | 2003-08-22 | 2015-03-31 | Schlumberger Technology Corporation | Real-time velocity and pore-pressure prediction ahead of drill bit |
| US11828169B2 (en) | 2020-11-12 | 2023-11-28 | Saudi Arabian Oil Company | Method of determining in-situ pore pressure in chemically active formations |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107515957A (en) * | 2016-06-17 | 2017-12-26 | 中国石油化工股份有限公司 | Mud shale SEQUENCE STRATIGRAPHIC DIVISION method |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0339752A1 (en) * | 1988-04-29 | 1989-11-02 | Anadrill International SA | Pore pressure formation evaluation while drilling |
| US4949575A (en) * | 1988-04-29 | 1990-08-21 | Anadrill, Inc. | Formation volumetric evaluation while drilling |
-
1992
- 1992-11-14 GB GB9223917A patent/GB2272525A/en not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0339752A1 (en) * | 1988-04-29 | 1989-11-02 | Anadrill International SA | Pore pressure formation evaluation while drilling |
| US4949575A (en) * | 1988-04-29 | 1990-08-21 | Anadrill, Inc. | Formation volumetric evaluation while drilling |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2380802A (en) * | 2001-10-12 | 2003-04-16 | Schlumberger Holdings | Pore pressure monitoring |
| GB2380802B (en) * | 2001-10-12 | 2003-09-24 | Schlumberger Holdings | Method and apparatus for pore pressure monitoring |
| US6871532B2 (en) | 2001-10-12 | 2005-03-29 | Schlumberger Technology Corporation | Method and apparatus for pore pressure monitoring |
| US8995224B2 (en) | 2003-08-22 | 2015-03-31 | Schlumberger Technology Corporation | Real-time velocity and pore-pressure prediction ahead of drill bit |
| CN102748016A (en) * | 2012-07-10 | 2012-10-24 | 中国石油大学(华东) | Geologic history period sandstone reservoir porosity evolution recovery method |
| CN102748016B (en) * | 2012-07-10 | 2014-10-08 | 中国石油大学(华东) | Geologic history period sandstone reservoir porosity evolution recovery method |
| CN103806855A (en) * | 2014-02-07 | 2014-05-21 | 中国海洋石油总公司 | Method for determining density of drilling fluid of extremely-thick rock salt stratum |
| CN103806855B (en) * | 2014-02-07 | 2016-03-23 | 中国海洋石油总公司 | The defining method of the liquid-tight degree of a kind of huge thick rock salt strata drilling |
| US11828169B2 (en) | 2020-11-12 | 2023-11-28 | Saudi Arabian Oil Company | Method of determining in-situ pore pressure in chemically active formations |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9223917D0 (en) | 1993-01-06 |
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| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |