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General presentation july2012


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  • 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.
  • Transcript

    • 1. MultiFocusing© TechnologyMarianne Rauch-Davies, Ph.D.David Schwartz
    • 2. Contents• MultiFocusing© theory• MultiFocusing© vs. conventional processing• Diffraction
    • 3. The Image is the message……Conventional PSTM MultiFocusing© Post-STM
    • 4. Pre-stack seismic data MultiFocusing© CMPWave front parameters Stacking Velocity analysis analysis NMO/time and depthMultiFocusing imaging migration imaging
    • 5. Real geology is not simple
    • 6. MultiFocusing© theory
    • 7. Conventional stackCommon Reflection / Depth Point Stacking SHOTS RECEIVERS 2 x2 t t 0 REFLECTOR V2 COMMON REFLECTING POINT
    • 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 correctionMultiFocusing time correction formula is valid for arbitrarysubsurface structure and for arbitrary source-receiverconfigurations 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 parametersCRE Radius & CEE Radius and emergence angle X0 X0 β β О Rcee Rcre ОRcre – radius of curvature of common reflection elementRcee – radius of curvature of reflected surface D
    • 11. 3D MultiFocusing - 8 parameters
    • 12. MultiFocusing stack The MF sums the data along the MF stacking surface
    • 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
    • 15. Conventional stack sp1 sp2 sp3 sp4 sp5sp1 sp2 sp3 sp4 sp5
    • 16. Geomage MultiFocusing stack sp1 sp2 sp3 sp4 sp5sp1 sp2 sp3 sp4 sp5
    • 17. Rugged Topography – synthetic example Synthetic horizontal reflector
    • 18. Rugged Topography – real data Conventional MultiFocusing©
    • 19. MultiFocusing anisotropy Anisotropy study begins with scanning for 5 parameters
    • 20. Anisotropy attributes V Slow V Fast V Azimuth
    • 21. Anisotropy cubes
    • 22. Enhanced Pre-Stack Gathers
    • 23. Enhanced MultiFocusing gathers MF stacking surface AThe MF sums the data along the green surface. The partial MF sums the dataaround the specified point (point A). The partial MF is shown in red coincideslocally with the MF stacking surface.
    • 24. Enhanced MultiFocusing gathersOriginal Gather MF Enhanced Gather
    • 25. MultiFocusing – enhanced pre-stack gathersMF Enhanced Gather MF Enhanced Gather after MF-MoveOut
    • 26. Original gathers
    • 27. MultiFocusing enhanced gathers
    • 28. MultiFocusing© vs. conventional processingExamples around the globe
    • 29. The MultiFocusing method - advantages• 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
    • 30. Reprocessing of vintage seismic dataConventional processing MultiFocusing processing
    • 31. Reprocessing of seismic data in foothillsConventional processing MultiFocusing processing
    • 32. Increasing vertical Resolution (~ 25% in frequency bandwidth)Conventional processing MultiFocusing processing
    • 33. Salt dome body contouring Salt body
    • 34. Better multiple attenuation
    • 35. PSDM Post stack depth migrated MF
    • 36. PSDM Post stack depth migrated MF
    • 37. Depth 3D processingPSDM Post stack depth migrated MF
    • 38. Eastern Europe (fold 32) – 1920 msConventional processing MultiFocusing processing
    • 39. 500 msConventional processing MultiFocusing processing
    • 40. 600 msConventional processing MultiFocusing processing
    • 41. Diffraction
    • 42. Diffraction - definition Obstacle Wave frontA diffraction occurs when a wave encounters an obstacle.In classical physics, the diffraction phenomenon is described as the apparent bending of wavesaround 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 fromseismic.
    • 43. How do we identify discontinuities?
    • 44. MultiFocusing ray scheme X0 X0 β β Rcre Rcee О О Reflection interface D
    • 45. MultiFocusing scheme for diffractions X0 β Rcre=Rcee О 2 R2 2 RX s sin Xs R R2 2 RX R sin XR 2 R V0 V0
    • 46. Numerical model Fractures
    • 47. Fracture intensity Size of fracture: 1 x 0.3 meter
    • 48. GMF Stack
    • 49. GMF Post-STM
    • 50. GMF Diffraction Stack
    • 51. GMF Diffraction Post-STM
    • 52. Geomage MultiFocusing – structure stack Offshore 2D – Mediterranean Basin
    • 53. Geomage MultiFocusing – Diffraction stack Offshore 2D - Mediterranean Basin
    • 54. MultiFocusing – migrated diffraction stack Offshore 2D - Mediterranean Basin
    • 55. MultiFocusing – migrated diffraction stack Colored on migrated MF stack Offshore 2D - Mediterranean Basin
    • 56. Example – 3D diffraction volume
    • 57. Thank You