1- MC Acquisition and MC Processing

Question 1

Multicomponent Acq

Homogenous

Answer 1

measured property is constant with respect to X,Y and Z in any given medium

consistent variable

Question 2

Multicomponent Acq

Inhomogenous

Answer 2

inconsistent variable

Question 3

Multicomponent Acq

Isotropy

Answer 3

uniformity in all orientations

Question 4

Multicomponent Acq

Anisotropy

Answer 4

Having properties that differ according to the direction of measurement

Question 5

Multicomponent Acq

Azimuth

Answer 5

angle between a line (shot and receiver group) and true north, measured in a horizontal plane

Question 6

Multicomponent Acq

Azimuth Anisotropy

Answer 6

Anisotropy associated with regional stress orientation. A wave travelling E-W travels faster than N-S

Question 7

Multicomponent Acq

P wave

Answer 7

particle motion is PARALLEL to the direction of wave propogation

compressional >—< and
dilatational

Question 8

Multicomponent Acq

S wave

Answer 8

particle motion is PERPENDICULAR to the direction of wave propogation.

2 kinds —- shear and transverse.

Question 9

Multicomponent Acq

what are the direction of motion for S waves ?

Answer 9

SV shear vertical
SH1 shear horizontal 1
SH2 shear horizontal 2

Question 10

Multicomponent Acq

mode conversion

Answer 10

P waves to S waves (P -> Sv)
S waves to P waves (Sv->P)

S waves CANNOT propogate in liquids !

Question 11

Multicomponent Acq

What is OBC (Ocean Bottom Cable) ?

Answer 11

Dual sensor
(Hydrophone and Geophone = sum of acquisition data)
Source/Receiver “Ghosts” and WB Multiples are attenuated by summation process,
WB multiples are cancelled out.

Question 12

Multicomponent Acq

What is 4C seismic method?

Answer 12

MARINE 
1 hydrophone (P wave)
3 geophones (S wave - 1 vertical and 2 horiz)

Question 13

Multicomponent Acq

Advantages of 4C seismic method ?

Answer 13

• imaging beneath gas plumes, salt domes, basalts
• detection of fluid-phase change from oil bearing to water bearing
• detection of vertical fracture orientation
• mapping HC saturation and
• mapping oil-water contact

Question 14

Multicomponent Acq

What is node positioning?

Answer 14

cable deployment
drop cable
water tensions
separate nodes in seabed

Question 15

Multicomponent Acq

What is node system?

Answer 15

node - individual unit with 1H and 3G

pressed into the seabed by a remote vehicle

Question 16

Multicomponent Acq

What is 4C seismic method MARINE ?

Answer 16

marine 4C
P -> P (PP data)
P -> S (PP data ) mode conversaion

Question 17

Multicomponent Acq

What is 4C seismic method LAND ?

Answer 17

land 3C
S -> S (SS data)
S -> P (SS data) mode conversion

Question 18

MC Data Processing

MC Shot Gather

Answer 18

Shot gather picture.
(from left to right)
Hydrophone
IL
XL
Vertical Geophone

Question 19

MC Data Processing

4C Shot Gather

Answer 19

Hydrophone
IL,XL
Vertical geophone

Question 20

MC Data Processing

What is AGC?

Answer 20

Automatic Gain Control

(kind of scaling)
Shot gather with scaling
Improved S/N ration appearance.

HYDROPHONE and VERTICAL geophone data contain P-wave data —> similar events
2 horizontal component data (IL, XL) contain S-wave data

Question 21

MC Data Processing

MC Shot Gather w- AGC
What does it look like ?

Answer 21

From left to right

Pv — Vertical P wave
SH1
SH2
Sv —- Vertical S-wave

Question 22

MC Data Processing

Differences between P/S wave data

Answer 22

P wave velocity is 1.7 x s-wave velocity

S wave events will appear later than P wave events

Question 23

MC Data Processing

Shot to Receiver Gather

Answer 23

Events on the 2 types of gather have different ampliture strengths

Question 24

MC Data Processing

Geophone coupling

Answer 24

If you’re going to do geophone couling, ensure it is surface consistent.

Question 25

MC Data Processing

coupling experiment

Answer 25

IL
XL
GEOPHONE VERTICAL 
corrected Xl
What it should look like.

Question 26

MC Data Processing

correction scalars ?

Answer 26

used to compensate for pour coupling.

shows what scalars were applied. A value gets added to everything.

Question 27

MC Data Processing

what is dual sensor summation ?

Answer 27

way to calibrate the geophone data

sum hydrophone and geophone data

Question 28

MC Data Processing

Processing Sequence

Answer 28

Geometric spreading correction
Deconvolution
Refraction and residual statics (KEY to LAND PROCESSING)
Velocity Analysis
NMO, DMO, Stack
Post Stack (Deconvolution, Filtering, Migration)

Question 29

MC Data Processing

Rotation of Horizontal Geophone Components

Answer 29

v geophones OK
h geophones need to be rearranged so that
acquisition coordinate system – IL/XL
coordinates
processing coordinate system- Radial-Transverse coordinats.
RADIAL – S-R plane
TRANSVERSE 90 degrees to RADIAL

Question 30

MC Data Processing

Rotation of Horizontal Geophone Components
Drawing

Answer 30

2 different images
Left Hand Image is Field Data, Right is Process Data
Of each left side is RADIAL and right side is TRANSVERS
Left side is not rotatesd and right side is rotated.
The one with the process data shows the radial side (left) is more clear) and the right side is almost erased.

Question 31

MC Data Processing

Energy Polarization

Answer 31

ASSUMPTION
Signal components (reflections, diffractions and C-waves are polarized in S-R direction
R component contains most fo the data
T component has the neglible data

Question 32

MC Data Processing

CCP Binning

Answer 32

Common Conversion Point Binning

PP wave
P wave scenario
incident angle = ref angle points MEET UP

PS wave
S wave scenario
incident angle > ref angle points DON’T MEET UP