SIBLEY, DAVID, Chevron U.S.A. Inc., Lafayette, LA; and SUSAN MASTORIS, Landmark Graphics Corporation, Houston, TX

ABSTRACT: Rethinking Conventional Field Development: 3-D Shows Direct Detection of New Reserves

Accurate well to seismic ties of several producing sands and analyses of reservoir characters have revealed hidden reserves in an aging field that was previously determined to be uneconomic. The combination of a recent three-dimensional survey shot over Eugene Island Blocks 338 and 339, Gulf of Mexico, and new interactive workstation technology were instrumental in identifying swept and unswept portions of different oil reservoirs and allowed new infill wells to pinpoint key targets.

Amplitudes were extracted along mapped horizons, which showed lateral variations in the reservoir properties, identifying zones where the waterfront had passed through (deterioration in amplitudes) and areas it had missed (strong amplitudes). For one of the successful wells, overlaying structural contours on the amplitude map showed that much of the oil could be recovered by drilling west and up to 30 m downdip from the current tilted oil/water contact--counterintuitive to traditional field development.

Net pay (detuned, composite isopach) maps were constructed by calibrating amplitudes to pay thicknesses. The top and base of these net pay surfaces were displayed in geologic cross sections to direct the horizontal paths of subsequent wells.

The result was a 100% success rate in five out of five development wells, to date. The wells are producing between 5740-9250 bbl/day, for Chevron and its operating partner, Texaco. This economic scenario directly resulted in a "turnaround" decision to keep what was once thought to be a B-rated property.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.