1- MC Acquisition and MC Processing Flashcards by V R Marr

Multicomponent Acq

Homogenous

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

consistent variable

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Multicomponent Acq

Inhomogenous

inconsistent variable

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Multicomponent Acq

Isotropy

uniformity in all orientations

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Multicomponent Acq

Anisotropy

Having properties that differ according to the direction of measurement

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Multicomponent Acq

Azimuth

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

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Multicomponent Acq

Azimuth Anisotropy

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

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Multicomponent Acq

P wave

particle motion is PARALLEL to the direction of wave propogation

compressional >—< and
dilatational

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Multicomponent Acq

S wave

particle motion is PERPENDICULAR to the direction of wave propogation.

2 kinds —- shear and transverse.

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Multicomponent Acq

what are the direction of motion for S waves ?

SV shear vertical
SH1 shear horizontal 1
SH2 shear horizontal 2

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Multicomponent Acq

mode conversion

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

S waves CANNOT propogate in liquids !

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Multicomponent Acq

What is OBC (Ocean Bottom Cable) ?

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.

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Multicomponent Acq

What is 4C seismic method?

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

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Multicomponent Acq

Advantages of 4C seismic method ?

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

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Multicomponent Acq

What is node positioning?

cable deployment
drop cable
water tensions
separate nodes in seabed

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Multicomponent Acq

What is node system?

node - individual unit with 1H and 3G

pressed into the seabed by a remote vehicle

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Multicomponent Acq

What is 4C seismic method MARINE ?

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

Multicomponent Acq

What is 4C seismic method LAND ?

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

MC Data Processing

MC Shot Gather

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

MC Data Processing

4C Shot Gather

Hydrophone
IL,XL
Vertical geophone

MC Data Processing

What is AGC?

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

MC Data Processing

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

From left to right

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

MC Data Processing

Differences between P/S wave data

P wave velocity is 1.7 x s-wave velocity

S wave events will appear later than P wave events

MC Data Processing

Shot to Receiver Gather

Events on the 2 types of gather have different ampliture strengths

MC Data Processing

Geophone coupling

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

MC Data Processing coupling experiment

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

MC Data Processing correction scalars ?

used to compensate for pour coupling. | shows what scalars were applied. A value gets added to everything.

MC Data Processing what is dual sensor summation ?

way to calibrate the geophone data | sum hydrophone and geophone data

MC Data Processing Processing Sequence

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

MC Data Processing Rotation of Horizontal Geophone Components

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

MC Data Processing Rotation of Horizontal Geophone Components Drawing

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.

MC Data Processing Energy Polarization

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

MC Data Processing CCP Binning

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