general presentation july2012
TRANSCRIPT
MultiFocusing© TechnologyMarianne Rauch-Davies, Ph.D.David Schwartz
Contents
• MultiFocusing© theory• MultiFocusing© vs. conventional processing• Diffraction
Conventional PSTM MultiFocusing© Post-STM
The Image is the message……
MultiFocusing imaging NMO/time and depth migration imaging
Wave front parameters analysis
Stacking Velocity analysis
Pre-stack seismic data
MultiFocusing© CMP
Real geology is not simple
MultiFocusing© theory
Common Reflection / Depth Point Stacking
SHOTS RECEIVERS
REFLECTOR
COMMON REFLECTING POINT
2
220 V
xtt
Conventional stack
v+
+
+
vv
vv
v
vv
+
+
+
Shot coordinate
Rec
eive
r coo
rdin
ate
++ +
+++
++
Normal move out equation is valid when only traces with equal distance to shot and receiver are stacked within a CDP gather (red)
CMP positionCMP tracesMF traces
++
Conventional stack
MultiFocusing time correction formula is valid for arbitrary subsurface structure and for arbitrary source-receiver configurations
0
22 sin2)(V
RXXRR ss
0
22 sin2)(V
RXXRR rr
source and receiver positions
are the radii of curvature of the wavefronts
rs XandX
is the emergence angle of the normal ray
),,( CEECRE RRR
),,,,( 0 rsCRE XXXR focusing parameter
MultiFocusing move-out correction
CRE Radius & CEE Radius and emergence angle X0
βО
D
Rcee
О
X0
β
Rcre
Rcre – radius of curvature of common reflection elementRcee – radius of curvature of reflected surface
2D MultiFocusing – 3 parameters
3D MultiFocusing - 8 parameters
The MF sums the data along the MF stacking surface
MF stacking surface
MultiFocusing stack
v
+
+ ++
v+
vv
vv
v
vv
++
Shot coordinate
Rec
eive
r coo
rdin
ate
++ +
+++
++
+ CMP tracesMF traces+
CMP position
+
+
++
+
+++++
+ + + ++
+
++
+++
Normal move out equation is valid when only traces with equal distance to shot and receiver are stacked within a CDP gather.Nearby traces (green) can not be used but are utilized by our MultiFocusing™ methodology.
MultiFocusing stack
X0 Xi
t0-Δt
t0
t0+Δt
TIM
E
Rcre β
Wavefront
z0
z0-Δz
z0+ΔzX0
Reflector
Xi
X
DE
PTH
Velocity corridor picking
Conventional stacksp1 sp2 sp3 sp4 sp5
sp1 sp2 sp3 sp4 sp5
Geomage MultiFocusing stacksp1 sp2 sp3 sp4 sp5
sp1 sp2 sp3 sp4 sp5
Synthetic horizontal reflector
Rugged Topography – synthetic example
Conventional
MultiFocusing©
Rugged Topography – real data
Anisotropy study begins with scanning for 5 parameters
MultiFocusing anisotropy
V Slow V Fast V Azimuth
Anisotropy attributes
Anisotropy cubes
Enhanced Pre-Stack Gathers
The MF sums the data along the green surface. The partial MF sums the data around the specified point (point A). The partial MF is shown in red coincides locally with the MF stacking surface.
MF stacking surface
A
Enhanced MultiFocusing gathers
Original Gather MF Enhanced Gather
Enhanced MultiFocusing gathers
MF Enhanced Gather after MF-MoveOutMF Enhanced Gather
MultiFocusing – enhanced pre-stack gathers
Original gathers
MultiFocusing enhanced gathers
MultiFocusing© vs. conventional processing
Examples around the globe
• Increases poor signal/noise ratio• Resolves signal over rugged topography• Resolves curved reflectors/ dipping events• Resolves variable velocity• Azimuth preservation• Use diffraction to detect natural fracturing
The MultiFocusing method - advantages
Conventional processing MultiFocusing processing
Reprocessing of vintage seismic data
Reprocessing of seismic data in foothills
Conventional processing MultiFocusing processing
Increasing vertical Resolution (~ 25% in frequency bandwidth)
Conventional processing MultiFocusing processing
Salt body
Salt dome body contouring
Better multiple attenuation
PSDM Post stack depth migrated MF
PSDM Post stack depth migrated MF
PSDM Post stack depth migrated MF
Depth 3D processing
Conventional processing MultiFocusing processing
Eastern Europe (fold 32) – 1920 ms
500 msConventional processing MultiFocusing processing
600 msConventional processing MultiFocusing processing
Diffraction
A diffraction occurs when a wave encounters an obstacle.
In classical physics, the diffraction phenomenon is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings.
Research suggests that this can be used to map fractures in the sub-surface from seismic.
Wave front
Obstacle
Diffraction - definition
How do we identify discontinuities?
X0
О
D
Rcee
О
X0
β
Rcre
β
Reflection interface
MultiFocusing ray scheme
О
X0
β
Rcre=Rcee
0
22 sin2V
RXRXR ss 0
22 sin2V
RXRXR RR
MultiFocusing scheme for diffractions
Fractures
Numerical model
Size of fracture: 1 x 0.3 meter
Fracture intensity
GMF Stack
GMF Post-STM
GMF Diffraction Stack
GMF Diffraction Post-STM
Offshore 2D – Mediterranean Basin
Geomage MultiFocusing – structure stack
Offshore 2D - Mediterranean Basin
Geomage MultiFocusing – Diffraction stack
Offshore 2D - Mediterranean Basin
MultiFocusing – migrated diffraction stack
Offshore 2D - Mediterranean Basin
MultiFocusing – migrated diffraction stack
Colored on migrated MF stack
Example – 3D diffraction volume
Thank You