Abstract: 3-D Acquisition Realities and Processing Strategies in Mountainous Thrust Areas

Scott Mackay, Stuart Wright, James Gaiser, Alex Jackson, Craig Beasley, R. Daniel Wisecup

The inherent structural complexity of thrust plays makes them ideal candidates for 3-D seismic imaging. However, there are many practical constraints placed on the acquisition of 3-D data in the mountainous terrains typically associated with thrust regimes. For example, financial considerations can result in tradeoffs between a desired acquisition geometry and that which is practical. Topographic relief can also impose irregular geometries and shortened receiver arrays. Such factors create challenges to the formation of a valid 3-D seismic image. Therefore, the realities of acquiring data in mountainous areas must be coupled with the appropriate processing strategies to yield an optimal result.

In practice there are processing techniques available to solve many of the problems related to 3-D land acquisition geometries. F-x coherent noise suppression, a method that relies on a least-squares estimate of coherent noise within a specified dip range, is effective for shot records with irregular offset sampling and azimuthally-varying noise. Amplitude and phase errors, introduced by the application of conventional DMO, may be reduced by properly equalizing dip components during DMO. The velocity/statics loop, complicated by a varying dip effect on velocity in the presence of a wide-azimuth geometry, may be simplified by using a data-derived dip field to correct for apparent dip. Prior to DMO or migration, application of an appropriate datuming methodology can avoid compromising t e data. Finally, although processing solutions exist that can couple the residual-statics solution, it is apparent that decoupling is merely symptomatic of the underlying long-wavelength statics problem. Therefore, a practical approach in survey design is to ensure proper sampling for 3-D refraction statics.

AAPG Search and Discovery Article #90958©1995 AAPG Pacific Section Meeting, San Francisco, California