8. Conventional stack
Normal move out equation is valid when only traces with equal
distance to shot and receiver are stacked within a CDP gather (red)
v
Receiver coordinate
v +
v
+ + +
v + +
v + ++ +
v +
v +
v +
+
Shot coordinate
CMP position
+ CMP traces
+ MF traces
9. MultiFocusing move-out correction
MultiFocusing time correction formula is valid for arbitrary
subsurface structure and for arbitrary source-receiver
configurations
2
(R )2 2 R X s sin Xs R (R )2 2 R X r sin Xr
2
R
V0 V0
X s and X r source and receiver positions
R ( RCRE , RCEE , ) are the radii of curvature of the wavefronts
( RCRE , X 0 , X s , X r , ) focusing parameter
is the emergence angle of the normal ray
10. 2D MultiFocusing – 3 parameters
CRE Radius & CEE Radius and emergence angle
X0 X0
β
β
О Rcee
Rcre
О
Rcre – radius of curvature of common reflection element
Rcee – radius of curvature of reflected surface
D
13. MultiFocusing stack
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.
Receiver coordinate
v
v +
v + + +
v + + + + +
v + ++ + + + +
v ++ + + + + +
v + + + + ++ +
v + + + + + +
v
Shot coordinate
CMP position
+ CMP traces
+ MF traces
14. Velocity corridor picking
z0-Δz Wavefront X0 t0+Δt
Xi
z0
z0+Δz t0
X0 Xi
X t0-Δt
β
TIME
Rcre
DEPTH
Reflector
23. Enhanced MultiFocusing gathers
MF stacking surface
A
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.
42. Diffraction - definition
Obstacle
Wave front
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.
Real geological surfaces are not smooth and continuous. Looking at that image just emphasize that declaration. You can see faults, movements of interfaces, fractures of different scale, size and direction. It varies from 1 mm to several hundred meters. All of that have huge implication on the interpretation that we are doing during the exploration and production process. For example, knowing the direction of the fault or fractures play crucial role on the decision where to put a rig and how to do that.At the same time most of modern imaging methods including PSDM and PSTM are looking for smooth and continuous interfaces as part of its QC routine. Normally, small scale heterogeneities in the subsurface are detected by visual interpretation of the imaging(manual or automatic) which is indirect procedure. On other hand seismic wavefield contain direct information about those small scale objects. This information encrypted in Diffraction energy. So, in case we would find a way to detect and image that energy, we found the key for that code. This presentation presents a way how to do that using MultiFocusing method.So the motivation is pretty simple – the industry would like to know where the fractures, faults and salt flanks are.
reflector
Target orientedOptimization was done in order to be in reasonable timeframesDiffractivity clouds might indicate directly fractured and faulted zones.
