SEISMIC DATA ACQUISITION

BY
ASEP SAMSUL ARIFIN
SEISMIC DATA ACQUISITION
POSITION
PLANNING A 3D SEISMIC SURVEY
CONCEPT
A New Survey Starts with a Geological Target
Survey planning is Everything you have to do before going into the
field and acquiring the data
Survey Planning includes;

1. Budgeting and financing

2. Survey Design

3. Organising Equipment and manpower

4. Dealing with Access Permits and other Legal Issues

SEISMIC DATA ACQUISITION PARAMETERS
Data Preparation and Analysis

ANALISA DISTRIBUSI OFFSET

ANALISA KANDUNGAN FREKUENSI

ANALISA UNTUK MENDAPATKAN KECEPATAN WELL DATA
DAN POSISI LAPISAN TARGET
SEISMIC DATA ACQUISITION PARAMETERS
Recording System

Earth’s surface Filter

R
S
A/D Amplifier
Converter

Trace
display

Subsurface reflector
Recording

TODAY’S MAIN
Tape
TOPIC DISCUSSION storage
DESIGNING A 3D SEISMIC SURVEY
Aim of Survey Design:

To fix all parameters of the survey to get good seismic data

(especially at the target), within budget and within time limits.

Good Seismic Data ?

1. High Signal/Noise (S/N) Ratio
CMP Fold, Offset Distribution, Source & Receiver Types
2. High Resolution
CMP Bin size, Source & Receiver Types

3. Adequate Spatial Coverage

Survey Extent (km2), CMP Bin size

4. Accurate Imaging
Need good Velocity Information Offset Distribution
Migration Effects CRP Distribution
3D SURVEY DESIGN
FLOW CHART
Geological Target Budget & Time Constraints

Set Basic Survey Parameters

Shot & Receiver Layout
Line & Station Spacing
Live Receivers for Each Shot

Computer Survey Design

Set Shot & Receiver Location Accurately
Use Background Map for Access Restrictions
Define CMP Bin Grid

Generate CMP Attribute Maps

CMP Fold, All Offsets
CMP Fold, Limited Offsets
Minimum Offset Plot
Offset Histogram Plots

YES
NO Finish
Attributes
OK?
SEISMIC DATA ACQUISITION
Geometry and terms used on 2D Survey Seismic

Receiver Points Far Offset

nnt Receiver
Source Points Spread Length (RL)

1st Receiver
Near Offset
Mid Points
Distance between
Distance between
shot points
Receiver points
2nd shot
1st shot

1st shot
Common Shot Points
2nd shot

3rd shot

4th shot
Fold Coverage 1 1 2 2 3 3 4 4 4 4 4 4 4 4 4 4 3 3 2 2 1 1
For four times shots Full Fold Coverage
Common Receiver
Common Mid Points
 3D SURVEY DESIGN
SURVEY PARAMETER - Geometry and terms used on 3D Survey Seismic
SL2

RL1

B A
RLI

RL2

SLI SL1

RL : RECEIVER LINE PERBANDINGAN ANTARA

SL : SHOT LINE INTERVAL UKURAN SURVEY AREA DI PERMUKAAN (B)
RLI : RECEIVER LINE INTERVAL DENGAN UKURAN SUB SURFACE ( A)
SLI : SHOT LINE INTERVAL BIASANYA ADALAH B=2A
DESIGNING A 3D SEISMIC SURVEY

Two Main Elements of Survey Design:

1. Choose Shot & Receiver Geometry to get Desired CMP Attributes
(mainly CMP fold and Offset Distribution)

2. Choose Suitable Sources and Receivers to Match Surface Conditions and

to Penetrate to Target Depth

Experience
Previous Data in Same or Similar Areas
Field Trips to Determine Access Restrictions
3D SURVEY DESIGN
CMP ATTRIBUTES
The CMP is a Key Feature of Reflection Seismology
Survey Designs are Evaluated from the Calculated CMP Attributes
1. CMP FOLD
Rough Rule: CMP Fold should be ~ 1/3Fold of Good 2D Data
2. Offset Distribution
Near Offsets Needed to Image Shallow Data, and to get
Good Shallow Velocities for Time to Depth Conversion
Far Offsets Needed to get Good Velocity information on
Deeper Structures
Rough Rule: Maximum Offset ~ Depth of Deepest Target
Need a good distribution of Offsets between the Near and Far
Offsets (otherwise velocity analysis is poor and coherent noise not very well
suppressed in CMP stack)
SEISMIC DATA ACQUISITION PARAMETERS
Bin Size & Receiver Interval
The bin size used for a 3-D survey is a trade off between physical and financial concerns.
On the physical side, the goal is to avoid spatial aliasing, which argues for a smaller bin size.
Financial concerns, however, argue for larger bin size.
(Liner,L.C., and Underwood,W.D., 3-D Seismic Survey Design for Linear V(z) media, Geophysics, Vol 64 NO.2, p.486-493,1999)

x=bin size Bin Size merupakan suatu ukuran spatial sampling

m1 m2 dalam survey seismik 3-D

 Dari gambar disamping :
Vt/2
vt (1)
sin =
2x
T
Agar aliasing tidak terjadi maka : t< (2)
2

Dimana : =
1 (3)
f
x : bin size (m)
V : Kecepatan lapisan target /reflektor Dengan mengeliminasikan pers. 2 &3 ke pers. 1, maka
: kemiringan reflektor Besaranya Ukuran Bin (BIN SIZE) adalah :
t : Perbedaan waktu tempuh (delay time)
vt v
dua titik eflektor ke posisi midpoint m1 & m2 x<  (4)
T : Perioda gelombang 4 sin 4 f sin
f : frekuensi gelombang Receiver interval biasanya x (5)
SEISMIC DATA ACQUISITION PARAMETERS
Bin Size
Choosing CMP Bin Size Choosing the Spatial Resolution of the Data
Two Considerations:
1. Aliasing of Dipping Events 2 Fresnel Zone (No Dip)
.Horizontal Resolution of Events Limited by Size of Fresnel Zone
dx
dz
Z 0 min V T
RF   .
 2 2 f max

Bin Size, V Bin Size, dx, should be smaller than RF

dx 
4. f max . sin 
Example
V = 1500 m/sec
Example: V = 2000 m/sec
fmax = 100 Hz
fmax = 70 Hz
 = 15º T = 1 sec
dx < 27.5 m dx < 75 m
 SEISMIC DATA ACQUISITION PARAMETERS
TARGET DEPTH  OFFSET DISTRIBUTION

THE REQUIERED OFFSET IS A FUNCTION OF THE DEPTH MODIFIED BY THE

VELOCITY FIELD ( STONE, ,D.G., 1994)

Three horizons should be considerd with beginning survey:

1. Shallow layer needed for minimum offset
2. Target Layer
3. Deepest layer needed for maximum offset
Each horizon should have informattion at least:
1. Depth of horizon ( Time and Depth)
2. Dip of horizon
3. Frequency content and thickness of horizon, especially target horizon
ALL OF THESE INFORMATION COULD BE OBTAINED FROM PREVIOUS SEISMIC DATA,
WELL LOGS, NOISE TEST, GEOLOGICAL THEORY AND EXPERIENCE
SEISMIC DATA ACQUISITION PARAMETERS
TARGET DEPTH  OFFSET DISTRIBUTION
OFFSET DEFINES AS DISTANCE ON THE SURFACE BETWEEN SOURCE POSITION
AND RECEIVER POSITION, WHICH RELATED TO THE CMP POSITION

NEAR OFFSET
The smallest distance between receiver position and source position
It related to shallow depth and considered to near surface layer
The length of near surfce is defined as

H min  (1  1.2) * Zsh

1
Z sh  Vavr * TWTsh
2
H min : mimimum offset (m)
Z sh : depth of shallow layer (m)
V avr : velocity of shallow layer (m)
TWTsh : two way time of of shallow layer (s)
At 3D Survey H min is called as X min, the largest minimum offset
SEISMIC DATA ACQUISITION PARAMETERS
TARGET DEPTH  OFFSET DISTRIBUTION
Far Offset

nnt Receiver
Spread Length (RL)

1st Receiver
Near Offset

Distance between
Receiver points

FAR OFFSET /MAXIMUM OFFSET

The longest distance between receiver position and source position
It related to deep target depth and considered to near surface layer
The length of longest surfce is defined as

V  Vsh 1 H max  Vavr (T 2  2Tx ( 0)  T )

H max  0.5 * Z * ( ) OR H max  Vavr * TWTobj OR
V  Vsh 2
H : maximum offset (m) V avr : velocity of deep layer (m)
max

Z : depth of deep layer (m) TWTobj : two way time of of deep layer (s)

V : velocity of deep layer (m/s)

V sh : velocity of near surface layer (m/s)

At 3D Survey H max is called as X max, the maximum offset

SEISMIC DATA ACQUISITION PARAMETERS
RECEIVER GROUP INTERVAL, OFFSET AND NUMBER OF CHANNEL
THE RELATIONSHIP AMONG GROUP INTERVAL, OFFSETS AND NUMBER OF CHANNEL
ARE FORMULATED AS :

( H max  H min )
( NC  1) 
GI

NC : number of channel used

GI : receiver group interval (m)
H min : mimimum offset (m)
H max : maximum offset (m)
SEISMIC DATA ACQUISITION PARAMETERS
MIGRATION APERTURE & FOLD TAPER

“The distance that added to the survey that required in the migration process”

Migration Aperture is affected by :

1. Fresnel Zone (RF)
2. Diffracted Energy (XDE)
3. Migration Lateral Displacement (DX)
Migration Aperture is choosed as the largest of RF, XDE, and DX

The common formula for Migration Aperture (MA) is :

MA  Z * tan 
Z : Depth of main target (m)
: Dip of main target
Another distance which added to the survey is Fold Taper, FT, which formulated as
FT  0.2 * X max
SEISMIC DATA ACQUISITION PARAMETERS
SURVEY SIZE
“The survey size includes length of the line survey (2D) or area of the survey (3D)
which usually have full fold coverage plus a distance for compensate these full fold“

Length of the line survey (2D) = Length of sub surface target + MA + FT + Tail

Length of 2D line survey

Length of sub surface target

Migration aperture length

Fold Taper Length
Tail

Area of 3D seismic survey

SEISMIC DATA ACQUISITION PARAMETERS
CMP 2-D Fold Coverage

REC =6
SP = REC

Rata-Rata
Nominal FOLD ~ 3

1 1 2 2 3 3 3 3 2 2 1 1
F
3
O2
Full Fold
L1
Area
D0
Tail Area (Partial Fold)
SEISMIC DATA ACQUISITION PARAMETERS
CMP 2-D Fold Coverage

REC =6
SP = 2 * REC

Rata-Rata
Nominal FOLD ~ 1.5


FOLD ~
SP

FOLD BERKURANG 1 1 1 1 2 2 1 1 2 2 1 1 2 2 1 1 1 1
SEIRING DENGAN F3
BERTAMBAHNYA O2
L
JARAK ANTAR SP D1 Full Fold Area
0

Tail Area (Partial Fold)

SEISMIC DATA ACQUISITION PARAMETERS
CMP 2-D Fold Coverage

REC =6
REC = 2 * SP

Rata-Rata
Nominal FOLD ~4

FOLD ~ REC

1 2 3 4 4 4 3 2 1
FOLD BERTAMBAH
F 4
SEIRING DENGAN 3 Full
BERTAMBAHNYA O 2 Fold
JARAK ANTAR L 1 Area
D 0
RECEIVER
Tail Area (Partial Fold)
SEISMIC DATA ACQUISITION PARAMETERS
CMP 2-D Fold Coverage

REC =8
SP = REC

Rata-Rata
Nominal FOLD ~4

REC
FOLD ~
2

1 1 2 2 3 3 4 4 3 3 2 2 1 1
FOLD BERTAMBAH
F 4
SEIRING DENGAN 3 Full
BERTAMBAHNYA O 2
L Fold
JUMLAH RECEIVER 1 Area
D 0
Tail Area (Partial Fold)
SEISMIC DATA ACQUISITION PARAMETERS
CMP 2-D Fold Coverage

REC= 8
SP = REC
Nominal FOLD = 4

REC = 8
SP = 2 * REC
Nominal FOLD = 2
SEISMIC DATA ACQUISITION PARAMETERS
CMP 2-D Fold Coverage- Conclusion

REC =6 REC =6 REC =6 REC =8

SP = REC SP = 2 * REC REC = 2 * SP SP = REC

Rata-Rata Rata-Rata Rata-Rata Rata-Rata

Nominal FOLD ~ 3 Nominal FOLD ~ 1.5 Nominal FOLD ~4 Nominal FOLD ~4

 REC
FOLD ~  FOLD ~ FOLD ~ REC FOLD ~
SP 2

HARGA FOLD BERKURANG SEIRING DENGAN BERTAMBAHNYA JARAK ANTAR SP

HARGA FOLD BERTAMBAH SEIRING DENGAN BERTAMBAHNYA JARAK ANTAR RECEIVER

HARGA FOLD BERTAMBAH SEIRING DENGAN BERTAMBAHNYA JUMLAH RECEIVER

SECARA MATEMATIS HUBUNGAN-HUBUNGAN TERSEBUT DAPAT DITULISKAN SEBAGAIBERIKUT :

FOLD 2-D ~ REC * REC

2 *SP
SEISMIC DATA ACQUISITION PARAMETERS
CMP Fold Coverage- Conclusion
Fold Coverage dapat didefinisikan sebagai banyaknya midpoint yang akan di-stack
dalam suatu CMP/ Bin

Nilai Fold dalam survey seismic 2D dihitung sebagai berikut :

Jarak antar Receiver X Jumlah Channel per shot point
2-D Fold =
2 X Jarak antar Shot points

Rumus Umum Nominal CMP Fold untuk setiap survey 2D maupun 3D :

Number of Channels per Shot

CMP Fold = Number of CMP’s per Shot

For Economical and Fast 3D Shooting,

Maximise the Number of Channels Per Shot ?
SEISMIC DATA ACQUISITION PARAMETERS
SOURCE POINT INTERVAL

FOLD 2-D ~ REC * REC

2 *SP
DARI PERSAMAAN TERSEBUT
1. UMUMNYA NILAI FOLD UNTUK SEBUAH SURVEY DITENTUKAN TERLEBIH DAHULU
2. UMUMNYA JARAK RECEIVER ADALAH DUA KALI SPATIAL SAMPLING
3. JUMLAH RECEIVER YANG DIGUNAKAN BERGANTUNG PADA KETERSEDIAAN ALAT
DAN KEDALAMAN TARGET (OFFSET MAKSIMUM)
SEHINGGA, DENGAN KONDISI TERSEBUT, JARAK ANTAR SHOT POINT
DAPAT DITENTUKAN SEBGAI BERIKUT:

REC * REC
SP =
2 * FOLD 2-D
SEISMIC DATA ACQUISITION PARAMETERS
BASIC PARAMETERS-SUMMARY
PARAMETERS INFORMATION NEEDED

1. CMP INTERVAL/ BIN SIZE 1. VELOCITY OF MAIN OBJECTIVE (V)

2. DIP STRUCTURE OF MAIN OBJECTIFE (q)
3. DESIRED FREQUENCY (F)

2. RECEIVER GROUP INTERVAL 1. VELOCITY OF MAIN OBJECTIVE (V)

2. DIP STRUCTURE OF MAIN OBJECTIFE (q)
3. DESIRED FREQUENCY (F)

3. OFFSET DISTRIBUTION 1. DEPTH OF NEAR SURFACE

2. DEPTH OF SHALLOW LAYER
3. DEPTH OF MAIN TARGET
4. DEPTH OF DEEP TARGET

4. NUBER OF CHANNEL 1. MAXIMUM AND MINIMUM OFFSET THAT REQUIRED

5. DESIRED FOLD
6. SOURCE INTERVAL 1. DESIRED FOLD
2. NUMBER OF CHANNEL
 3-D SEISMIC ACQUISITION
PARAMETERS
3-D FOLD SL2 MIGRATION
BIN SIZE APERTURE

IN LINE FOLD RL1 AZIMUTH

X - LINE FOLD SOURCE LINE

INTERVAL
RLI
RECEIVER LINE
INTERVAL SWATH

X-MIN
RL2 SALVO

TEMPLATE SIZE
X-MAX SLI SL1
SEISMIC DATA ACQUISITION PARAMETERS
3-D FOLD
SL1
3D FOLD usually 1/3 – ½ of 2-D FOLD In-Line Fold
RL1
Another equations for calculated FOLD Partial Fold Area

X-Line Fold

Partial Fold Area

Partial Fold Area

1. 3-D FOLD = NS *NC * B*B 3-D FOLD
Full Fold Area
2. 3-D FOLD = In-Line Fold * X-Line Fold

NS = NUMBER OF SHOT POINTS PER SQ. KM

NC = NUMBER OF LIVE CHANNEL USED
B = BIN SIZE

Fold
Symmetric Sampling: Receiver Line Spacing = Shot Line Spacing
2
 NumLiveCH 
3D _ Fold   
 2 . LineSpacing 

 NumLiveCH R  NumLiveCH S 
No Symmetric 3D _ Fold    
 2.ShotLineSpacing  2.RcvLineSpacing 
SEISMIC DATA ACQUISITION PARAMETERS
3-D FOLD

Number of Channels per Shot

CMP Fold = Number of CMP’s per Shot

16 Bins per Shot Line

2 Bins per Shot Station
32 CMP Bins per Shot Point

720
CMP Fold = = 22.5
32
SEISMIC DATA ACQUISITION PARAMETERS
3-D FOLD- IN LINE FOLD ( ROLL ALONG ACQUISITON)

1st trace in CMP gather is near

Roll-Along offset
last trace is the far offset reached after the
shot and spread
have moved half a spread length

Every shot between these points

contributes to the CMP

So, CMP fold = Number of shots in 1/2

spread
Nch

2. SPinc
SEISMIC DATA ACQUISITION PARAMETERS
3-D FOLD- X- LINE FOLD ( SWATH SHOOTING)

1 2 3 4 5 6

4 5 6 7 8 9

Fold is always 3
SEISMIC DATA ACQUISITION PARAMETERS
3-D FOLD- FROM SINGLE SHOT
SEISMIC DATA ACQUISITION PARAMETERS
3-D FOLD- FROM TWO SHOTS
SEISMIC DATA ACQUISITION PARAMETERS
3-D FOLD- FROM ONE TRAVERSE (18 shots)

Next Swath
Starts Here
SEISMIC DATA ACQUISITION PARAMETERS
CMP SKID (CMP GRID ADJUSTMENT)

Shift the CMP Bin Grid

Poor Bin Alignment

CMP Scatter is at Bin Boundaries

Irregular CMP Attributes

SEISMIC DATA ACQUISITION PARAMETERS
CMP SKID (CMP GRID ADJUSTMENT)

Much Better Bin Alignment

SEISMIC DATA ACQUISITION PARAMETERS
CMP FOLD (55’ x 110’ bins)
SEISMIC DATA ACQUISITION PARAMETERS
CMP FOLD (80’ x 80’ bins)

You Cannot Choose Bin Size Freely

SEISMIC DATA ACQUISITION PARAMETERS
RECEIVER LINE INTERVAL (RLI)
A DISTANCE BETWEEN RECEIVER LINE IN 3D SURVEY SEISMIC
THE MUTE FUNCTION is paramount of importance for the determination of LINE INTERVAL
and MAXIMUM OFFSET. It determines the range of offsets that can potentially contribute to
each time level (Vermeer, G.J.O., 1998)
Xsh means
Xmin Xsh Xdp offset
SLI Largest Minimum Offset (LMOS)
tmin atau MINIMUM OFFSET TERBESAR
RL2
tsh IF SLI = RLI THEN
RLI
SLI=RLI= LMOS / 2 3/2
RL1
Desired Fold (M)at shallowest target,
Xsh/2
Maximum Offset, RLI and SLI are
tdp
related as

time SL1 SL2 M = ( Xmax/SLI)*(Xmax/RLI)

H max  Vavr (T 2  2Tx ( 0)  T )

SEISMIC DATA ACQUISITION PARAMETERS
SOURCE LINE INTERVAL (RLI)
A DISTANCE BETWEEN SOURCE LINE IN 3D SURVEY SEISMIC

THE FIRST WAY (STONE,D.G.,1994)

NS = (F * 106)/ (NC * Bx * By) THE SECOND WAY (CORDSEN, 1995)
SLI = 106/ (NS *B)
3-D FOLD = In-Line Fold * X-Line Fold
SLI = (SREC * DREC) /In-line Fold
SL2 LMOS2 = RLI2 + SLI2
RL1
OS
NS = NUMBER OF SHOT POINTS PER SQ. KM
F = 3-D FOLD
LM RLI NC = NUMBER OF LIVE CHANNEL USED
B = BIN SIZE
SLI = SHOT LINE INTERVAL
RL2 LMOS = LARGEST MINIMUM OFFSET

SLI
SL1
SEISMIC DATA ACQUISITION PARAMETERS
TEMPLATE SIZE
A SMALL UNIT RELATES BETWEEN ONE SHOT AND LIVE CHANNEL (SUM OF
RECEIVER AT ALL LINE) INVOLVED
A Template size will use forSHOOTING A WHOLE SURFACE AREA OF ONE SURVEY
TEMPLATE SIZE =RL * REC
RL1
RL2
RL3
RL4
RL5
RL6
RL7
RL8

WIDE “AZIMUTH” TEMPLATE SIZE

RL1
RL2
RL3
RL4
RL5
RL6

NARROW “AZIMUTH” TEMPLATE SIZE

A Template size usually considers from available recording tools

 SEISMIC DATA ACQUISITION PARAMETERS
Swath Acquisition Template
Ch 720 Ch 601

Ch 600 Ch 481

Ch 480 Ch 361

Ch 360 Ch 241

Ch 240 Ch 121

60 Channels 60 Channels
Ch 120 Ch 1

6 Receiver Lines. 120 Channels per Line

18 SP’s Between Receiver Lines 2 & 5 60 Live Channels (Maximum) on Each Side of the Shots
Receiver Spread is Fixed for All 18 Channel #1 is at the South-East Corner of the
SP’s Template
SEISMIC DATA ACQUISITION PARAMETERS
Swath Roll-Along Acquisition

When 18 shots have been Fired, Roll Along to Next Shot Line
(880’ or 8 Receiver Stations)
SEISMIC DATA ACQUISITION PARAMETERS
Edge of Survey

At Edge of Survey the the Channels are Dead

Survey
Survey Edge
Edge

Dead
Channels
SEISMIC DATA ACQUISITION PARAMETERS
SEISMIK RESOLUTION

All photographers understand the

importance of resolution

Geophysicists are learning this too.

SEISMIC DATA ACQUISITION PARAMETERS
ATTRIBUTE ANALYSIS

THE STANDARD ATTRIBUTES ANALYZED FOR EACH BINS ARE

(Stone, D.G., 1994)
• DEPTH POINT COVERAGE
• FOLD
• OFFSET RANGE
• AZIMUTHAL DISTRIBUTION
• COSTS
BIN
REC1
RL1

X- RL2 SL2
MA
X
RL3 RL1
IN
RL4 M
X-
RL5
SP1
RL6
RL2
RL7

RL8 SL1