SHIPP, R. CRAIG, Shell Exploration and Production Technology Co.; ROBERT C. SHOUP, Shell Deepwater Development Inc.; and FREDRIC A. DIEGEL, Shell Offshore Inc.

Abstract: High-Resolution Near-Surface Seismic Analogs for Deep Subsurface Canyon/Channel-Margin Slides

Recent improvements in seismic data quality, and the acquisition of high-resolution seismic data enable detailed imaging of pairs of rotational slide systems associated with erosional canyons and channels observed in the near-surface section of the deep-water Gulf of Mexico. Previously interpreted as "chaotic zones", these features are now resolved as paired groups of en echelon detachment faults. These small-scale gravity-slide faults form in response to the failure of the opposing slopes during canyon or channel incision.

Channel-margin slide systems are characterized by 1) base failure, 2) strata-parallel detachments, 3) multiple rotated blocks, and 4) asymmetry across the canyon/channel. For any given canyon/channel system, the detachment surface for the paired slide-faults typically occurs at the same stratigraphic level along the length of the canyon. Strata within the failed section deform as discrete rotational blocks, apparent even in low resolution conventional seismic data, and strata within the blocks frequently have dips up to 25°. The horizontal extent of the detachment zone frequently appears to be assymetric in respect to the canyon.

Study of deepwater channel-margin slides in the near surface facilitates recognition and mapping of similar features in the deep subsurface, where these phenomena result in compartmentalization of the reservoir. In the deeper section, the canyon/channel cut rarely appears as a discrete event, rather, it appears as a series of truncated events.The associated rotational slide faults typically appear as minor discontinuities between two to five parallel seismic events.

AAPG Search and Discovery Article #90923@1999 International Conference and Exhibition, Birmingham, England