Seismic Time Processing
SIGMA³ is a leading provider of seismic processing services for the oil and gas industry from field tapes through final migration. With global experience in all environments, including complex topography, mountainous regions, permafrost, desert, swamp, shallow- and deep-water marine, SIGMA³ solutions include workflows for overthrusts, fault shadows, salt bodies, complex geology and stratigraphic targets.
With our Time and Depth imaging solutions, we offer a continuous solution from field tape through to accurate focusing and positioning of the subsurface reflection information, providing a sound basis for accurate interpretation and reducing the risk for optimum well placement.
Geometry/Navigation Merge & Quality Control
For both onshore and offshore surveys, the first critical step in any processing sequence is to ensure that geometry or navigation data are correctly merged. The key here is to ensure that the workflow is methodically followed and adhered to
Typical techniques for quality control purposes of geometry and navigation data include interactive offset vs. first breaks analysis, fold plot maps, azimuth plot maps, water velocity vs. first breaks correction, comparison of P90 files vs. ob's, near trace stack. Verification and correction of accurate navigation merge is performed by comparing predicted first breaks vs. actuals. Near trace stacks and raw stacks are used for QC purpose.
SIGMA³ offers the world-class geometry and statics services using the Seismic Studio™ package. Seismic Studio is the premier solution for challenging land and marine data sets where shallow subsurface velocity and geometry problems degrade the quality of seismic data. Seismic Studio includes the following capabilities.
- 2D & 3D Geometry Correction
- Refraction Statics
- Tomographic and Hybrid Tomographic Statics
NoisePRO™ has been used and is a standard process used in most 3D processing workflows either as a standalone application or as a complementary process with SRME or Radon noise suppression. It is typically used throughout the processing sequence in the pre-stack, time or depth domain, and also in the stacked domain. The methodology is also used for removal of residual multiple remaining on the near offsets after SRME/Radon applications. A Zoepprittz based modeling approach is used, followed by an adaptive subtraction of the model and the data preserving the primary amplitudes. A key component of the methodology is QC of the output against the input by differencing.
NoisePRO is a custom methodology whereby a domain (eg f-k, t-p etc.) is identified where controlled separation of signal and noise may be obtained for noise rejection in the relevant space before re-transformation to the original x-t (or z) domain. The noise component is processed for any residual signal, which is added back to the signal component. Gather, Common Offset and Post-Stack domain applications are available dependent on the noise type, geologic environment, and separation characteristics of the signal and noise.
SIGMA³ offers the following multiple attenuation schemes:
- Vw Radon
- 2D & 3D SRME
- Hi-Res Radon
- NoisePRO custom flows
- Deconvolution-based methods
- Inner Trace Mute
Typical Wavelet shaping approaches include:
- Raw signature provided by acquisition contractor (produced from modelling software)
- Add source and receiver ghosts (source at 7m, receivers at 9 m)
- Create desired wavelet as the zero phase equivalent of the ghosted wavelet
- Use a two-sided Wiener least-squared-error algorithm to create an optimum filter
- In absence of measured wavelet, estimation possible from WB reflector
- Spacing based on geology
- Super-binning as required
- Pre-processing for resolution
- Well Checkshot Vavg for trends
- Post-PSTM AutoRMO for final tuning
- Final Model as Input to PSDM
SIGMA³ uses proprietary migration tools. Kirchhoff PSTM has a DIP limit of 90 Degrees and can use Eikonal or Curved Ray Travel time with an option for curved ray starting at the water bottom. Dips may be limited by offset/ Data (or NMO) Stretch (depending on the time) and anti-alias. The aperture is parameterized in half aperture (or radius). Migration algorithms can use ETA for anisotropic imaging.