--> Abstract: Geophysical Reservoir Analysis, Eugene Island 384, by S. M. Murray and D. A. Gilbert; #91012 (1992).

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ABSTRACT: Geophysical Reservoir Analysis, Eugene Island 384

MURRAY, STEVEN M., and DEAN A. GILBERT, Nerco Oil & Gas, Inc., Houston, TX

Detailed predevelopment geophysical reservoir analysis has yielded success in the delineation and development of offshore Gulf of Mexico Pleistocene reservoirs. Both 2-D and 3-D seismic data were incorporated in structural interpretation, amplitude analysis, AVO evaluations, and inverse modeling. Amplitude anomalies depicted two styles of potential hydrocarbon traps. One group was trapped up against the western flank of a piercement salt diapir and conformed to structure downdip. A second group of amplitude anomalies was located in the basin and did not conform to structure.

Amplitude vs. offset (AVO) analysis in the first group was inconclusive because of the depth (8000 ft) and steeply dipping beds (25 degrees). The decision to drill was made based on the amplitude strength, continuity, structural conformance, and wedge models predictive of significant hydrocarbons. The first well drilled encountered 168 gross ft of gas pay, the second well, located at the edge of the amplitude,

encountered 50 ft of gas on water, and a subsequent updip sidetrack logged 195 ft of gross sand gas.

To evaluate the off-structure amplitude anomalies, models were generated with various thicknesses and velocities in an attempt to predict gas reservoir thickness and the potential for an associated oil rim. Inverse modeling, routine amplitude analysis, time slices, and wedge models were combined to predict 160 gross ft of gas separated by 50 ft of higher velocity material. The well encountered 142 ft of gas separated by a 40 ft shale. Wedge modeling and seismic amplitude evaluations also supported the potential of an oil rim. A planned sidetrack tested this hypothesis and encountered wet sands.

Both the strengths and weaknesses of these methods will be shown by the 14 well penetrations.

 

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)