The Fallacy of Simple Geology: a Case for Depth Imaging All 3-D Data

Young, John A.^1
1 Data Processing, WesternGeco, Denver, CO.

Prestack time migration been accepted by the industry as standard 3-D seismic processing practice. This has lead to improved imaging in many areas and the ability to use 3-D seismic data for AVO, prestack inversion, and other advanced prospecting methods. Refinements such as ray tracing, and the incorporation of anisotropic parameters have provided further improvements in time imaging. Despite these in-novations, time migration is inherently unable to properly handle lateral velocity variations, limiting its effectiveness for accurate imaging. Prestack depth migration addresses these shortcomings.

Prestack depth migration has been used extensively to resolve imaging problems in areas where strong lateral velocity contrasts are caused by salt bodies or complex structural geology. However, the method has been under-utilized in areas of lower structural relief, and “simple” velocity regimes where the limita-tions of time imaging can be less obvious. The combination of high-resolution gridded tomography and prestack depth migration can resolve the local velocity contrasts that distort the subtle structural re-sponse and compromise seismic attributes. Various examples illustrate the uplift provided by depth im-aging. Case studies include data from the Rocky Mountains, the Eastern U.S., South Texas, and a do-mestic resource play where fracture detection and fault avoidance are critical.

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009