PreStack Depth Migration

Over the years, Bulwark/GX Technology (GXT) has become a recognized leader in the area of prestack depth imaging, a capability that extends throughout the company's Image-Driven™ seismic solutions. Pre stack depth migration (PreSDM) is a processing technique that moves seismic reflections to their correct locations in space. Although not universally applied in every seismic program, PreSDM is critical in areas where there are significant and rapid lateral or vertical changes in velocity that distort images acquired in the time domain. The Gulf of Mexico is one such area, and it was here, in the complex world of subsalt imaging, that Bulwark/GXT rose to prominence as a leader in advanced PreSDM.

To successfully apply PreSDM techniques, a seismic imaging provider must have advanced capabilities in data conditioning and, especially, in Velocity Modelling. Bulwark/GXT has developed recognized leadership in both of these areas.
 

Since every imaging situation is unique, and hybrid solutions that combine more than one PreSDM approach sometimes yield the best result, Bulwark/ GXT offers a comprehensive toolkit of technologies, including:

Reverse time migration (RTM). RTM works by running the wave equation forward in time for the source and backwards in time for the receiver. RTM properly propagates the wavefields through the most complex velocity regimes, including subsalt, for structures having dips in excess of 70 degrees, and in the presence of reflection boundaries that may generate internal multiples.

Shot-based wave equation depth migration, to provide the best imaging results for complex geological environments, such as those produced by a rugose top of salt. Bulwark's/GXT's wave equation PreSDM solution does not suffer from problems typically associated with conventional wave equation implementations, such as numerical dispersion, azimuthal anisotropy, or limited dips. Bulwark's/GXT's shot-based wave equation migration can also be applied to extract true 3D reflection angle gathers.

Kirchhoff depth migration algorithms that have been customized by Bulwark's/GXT to be amplitude preserving -- therefore a premier choice for amplitude variation with offset (AVO ) studies, capable of accommodating turning rays (for imaging very steep dips and overhangs), and able to account for anisotropic conditions. A key benefit is that Bulwark's/GXT's Kirchhoff solutions are significantly faster than most other Kirchhoff-based tools employed by the industry.

Beam Migration techniques have the advantages of dealing with multiple arrivals and keeping costs down by computing operators only in the vicinity of a narrow trajectory. Depending on the beam scheme employed, this dip representation may be comprehensive or it may be sparse designed to characterize only the significant features of the data.

Bulwark/GXT is committed to maintaining its technological and operational leadership in the area of PreSDM. The company's Image-Driven approach produces the highest quality seismic images under the most extreme imaging conditions. These detailed, less ambiguous images improve subsurface interpretation even in geologically complex areas, reducing drilling risk for oil & gas companies. Bulwark's/GXT is constantly improving the run-time performance of our sophisticated migration methods without sacrificing the quality of our results. With a full suite of imaging algorithms, we deliver "no compromises" images efficiently, on time, and within budget.