Abstract

Sandstones of the Delaware Mountain Group in West Texas are the focus of a DOE Class III field demonstration project. Reservoir characterization of the Ramsey sandstone interval of the Bell Canyon Formation is being conducted in Ford Geraldine unit, Culberson and Reeves Counties, Texas, using 3-D seismic data, subsurface log and core analysis, and data collected from outcrop exposures. The objective of the project is to demonstrate that detailed reservoir characterization is a cost-effective way to recover more of the original oil in place.

Ramsey sandstones occur in the uppermost cycle of the Bell Canyon Formation and represent progradation, then retrogradation, of an elongate channel-levee and lobe complex deposited by turbidity currents on the basin floor. On the basis of core description and field mapping of Bell Canyon sandstones exposed in outcrop 24 mi from Ford Geraldine unit, the reservoir sandstones are interpreted to consist of lobe deposits overlain and incised by lenticular 1,200-ft-wide channels. Adjacent levee and overbank deposits vertically and laterally separate channel sandstone bodies. Ramsey sandstones are bounded by laterally continuous, organic-rich siltstones.

Additional heterogeneity was caused during burial diagenesis by nonuniform precipitation of authigenic calcite and chlorite in very fine grained reservoir sandstones. Porosity ranges from 2 to 30% and averages 24%. Permeability ranges from <0.1 to 408 md and averages 28 md. Special techniques were used to maximize the information that could be derived from the old geophysical logs at Ford Geraldine unit. Log and core data were used to establish net-pay cutoffs of 15% porosity (for permeability of 1 md), 60% water saturation, and 15% volume of clay.