1- MC Acquisition and MC Processing Flashcards
Multicomponent Acq
Homogenous
measured property is constant with respect to X,Y and Z in any given medium
consistent variable
Multicomponent Acq
Inhomogenous
inconsistent variable
Multicomponent Acq
Isotropy
uniformity in all orientations
Multicomponent Acq
Anisotropy
Having properties that differ according to the direction of measurement
Multicomponent Acq
Azimuth
angle between a line (shot and receiver group) and true north, measured in a horizontal plane
Multicomponent Acq
Azimuth Anisotropy
Anisotropy associated with regional stress orientation. A wave travelling E-W travels faster than N-S
Multicomponent Acq
P wave
particle motion is PARALLEL to the direction of wave propogation
compressional >—< and
dilatational
Multicomponent Acq
S wave
particle motion is PERPENDICULAR to the direction of wave propogation.
2 kinds —- shear and transverse.
Multicomponent Acq
what are the direction of motion for S waves ?
SV shear vertical
SH1 shear horizontal 1
SH2 shear horizontal 2
Multicomponent Acq
mode conversion
P waves to S waves (P -> Sv)
S waves to P waves (Sv->P)
S waves CANNOT propogate in liquids !
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.
Multicomponent Acq
What is 4C seismic method?
MARINE 1 hydrophone (P wave) 3 geophones (S wave - 1 vertical and 2 horiz)
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
Multicomponent Acq
What is node positioning?
cable deployment
drop cable
water tensions
separate nodes in seabed
Multicomponent Acq
What is node system?
node - individual unit with 1H and 3G
pressed into the seabed by a remote vehicle
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
