3D Prestack Finite Difference Wave Equation Migration


State of the art downward continued operators are constructed based on the one-way acoustic wave equation, and used to migrate shot records. The use of a novel, patent-pending Imaging Condition, as well as an ingenious treatment of pseudo-evanescent energy, has extended the accuracy of the amplitude reconstruction to a very high level and the dip response to 90 degrees. This technology has been successful in imaging complex structures on a commercial basis for nearly 2 years. 
 

3D Common Image Depth Angle of Incidence Gathers


Utilizing the Wave Equation Migration described above, TGS Imaging has implemented a patented technique for generating Common Image Angle of Incident Gathers in the depth domain.  These gathers are then used to perform depth domain Velocity Analysis and Modeling, AVO in Depth and high-resolution Pore Pressure Predictions.

 

3D Wave Equation Illumination


TGS Imaging has developed a proprietary (patent-pending) illumination technology that is a product of the wave equation migration.  This allows the study and analysis of energy propagation and penetration through complex velocity depth models.  This tool allows analysis of imaging illumination on full 3D volumes and target (horizon) basis wave propagation instead of ray propagation.  The illumination values are used for amplitude balance and compensation and for shadow zone prediction.

 

Complex (Multi-Valued Horizon) Velocity Model Building


TGS Imaging has developed tools to accommodate complex salt and fault block structures.  Software has been developed for picking complex Velocity Blocks, including faults and Multi-valued Salt Structures in 3D.  This allows interpreters to pick a complete complex structure at one time, without the restriction of conventional horizon interpretation.  These tools, using techniques from Medical Cat-Scan Image Reconstruction, let interpreters pick multi-value, recumbent, and disjoint surfaces.

 

Velocity Updating Techniques in Depth


Vertical Velocity Updating: In areas with well-defined supra-salt and salt models, or gentle dips and velocity gradients, Focusing Panels and Depth Semblance calculations are used to estimate depth errors on Depth Image Gathers utilizing a modified form of the Deregowski Loop, where the depth errors at different offsets are attributed to the vertical overburden.

 

Tomographic Velocity Updating 


In complex areas where rays are not straight or severe dips are present, a layer based Tomographic updating is utilized.  Horizons are picked and travel times are calculated to the surface.  The depth error in migrated gathers is utilized to estimate a time delay, and through ray tracing and inversion a velocity/depth correction is determined.

 

Depth Gather Conditioning and Anisotropic Corrections


By utilizing complex analysis computed on depth image gathers, a high-resolution velocity analysis tool has been developed.  This tool is used in conjunction with massively parallel computing to calculate a high-resolution (every CDP) time variant and spatially variant residual velocity.  The tool is also extended to long offset data (4th order) to compute an anisotropy field and anisotropic correction.  The resulting gather data generate optimized final volumes and AvO attributes.  The resulting high-resolution velocity field provides the input to Vertical Effective Stress and Pore Pressure predictions.

 

2D/3D Acoustic/Elastic Modeling


TGS Imaging has implemented a sophisticated finite difference 3D acoustic/elastic modeling algorithm and a massively parallel computing platform.  This provides an accurate and robust tool for realistic modeling of complex structures.  This technology provides a unique and extraordinary leveraging service to our customers by allowing quick simulation of multiple velocity-depth scenarios for both P and S wavefields.  This allows cost effective study of a variety of interpretation scenarios and the imaging consequences.  This tool is used as part of depth imaging workflows to evaluate alternative models, the impact of multiples on final images, if a subsalt reflector is a multiple or a converted wave, or questions concerning acquisition geometry.

Preprocessing:
  • Navigation Merge
  • Shot & Receiver Geometry Database & Statistical Analysis
  • Statistical Noise Analysis & Attenuation
  • Surface Consistent Amplitude/Shot Balance
  • Swell Noise Attenuation
  • Adaptive P-Z Summation
  • Multi-Boat Dynamic Correction
  • Q Estimation & Correction
  • Hyperbolic Radon Demultiple
  • High Resolution Radon – (Adaptive High Frequency) 
  • Surface Related Multiple Attenuation (SRME)
3D Enhanced Kirchhoff Prestack Time Migration:
  • Enhanced Kirchhoff Prestack Time Migration
    - 6th Order Accuracy
    - 90 degrees Dip Response
    - Curved Ray & Turning Ray Capable
    - Exact Anti-Aliasing
    - 8x Input Oversampling
Post Migration Gather Conditioning & Volume Generation:
  • Continuous Residual Hyperbolic Velocity Analysis (every gather)
  • Residual Hyperbolic Radon De-Multiple
  • High Resolution-Long Offset Analysis (3 Term - 6th order, anisotropic)
  • Three Term (6th Order) Velocity Correction (Full Offset)
  • Target Oriented Angle Analysis & Angle Stack Generation
Prestack-AvO Attribute Generation:
  • Offset Dependant Amplitude Analysis & Correction
  • High Resolution AvO Based Velocity Analysis
  • Wavelet and Offset Dependant Analysis & Correction
  • Statistical Overburden/Background Analysis & Correction
  • AvO & Deviation Attribute Generation
High Resolution Pore Pressure Estimation & Calibration:
  • High Resolution Velocity Estimation & Correction
  • Density/Overburden Analysis & Calculation
  • Pore Pressure-Effective Stress Analysis & Calibration
  • Effective Stress & Fracture Gradient Estimation
3D Prestack Finite Difference Wave Equation Migration:
  • Finite Difference Shot Domain Downward Continuation
    - Full Wavefield/Multi-Path Downward Propagation
    - 90 degrees Dip Response
    - True Amplitude
    - Exact-Unsmoothed Velocity Model Representation
    - Common Angle of Incident  Image Gathers with Optional Non-Linear Offset Binning
Velocity-Depth Modeling:
  • 3D/2D Acoustic-Elastic Forward Modeling (Finite Difference)
    - Interpretation & Velocity-Depth Model Sensitivity Analysis
  • 3D Wave Equation Velocity Analysis
    - Image Gather Output
    - Focusing Panel – Depth Semblance
  • 3D Velocity Modeling & Updating
    - 3D Tomographic Updating
    - Vertical Updating
    - Recumbent/Multi-valued Salt Structure Volume Construction
3D Wave Equation Illumination:
  • 3D Illumination Based Energy Penetration & Imaging QC
  • Illumination Based Amplitude Compensation
  • 3D Volume & Target Horizon Based Illumination Analysis
Support Services & Technologies:
  • PRIMA
    - Multi-volume prestack analysis and visualization
    - Integrated multi-dimensional crossplot analysis
    - Gather interpretation & quantitative analysis
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