Print this pageReservoir Characterization of Permian Deep-Water Ramsey Sandstones, Bell Canyon Formation, Ford Geraldine Unit, West Texas (Delaware Basin)
DUTTON, SHIRLEY R, MARK D. BARTON, SUSAN D. HOVORKA, ANDREW G. COLE, and GEORGE B. ASQUITH
Low-producing deep-water sandstones of the Delaware Mountain Group in West Texas (average recovery <14% OOIP) are the focus of a DOE Class III field demonstration project designed to improve oil recovery by strategic infill-well placement and geologically based field development. Reservoir characterization of one of the most prolific zones, 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 outcrop characterization.
Ramsey sandstones occur in the uppermost cycle of the Bell Canyon Formation and represent progradation, then retrogradation, of an elongate submarine channel and lobe complex formed by sediment-gravity flows 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 sheetlike lobe deposits overlain and incised by lenticular 1,000-ft-wide channels. Adjacent levee and overbank deposits vertically and laterally separate channel sandstone bodies. Ramsey sandstones are bounded by laterally continuous, organic-rich distal-fan siltstones deposited by settling from suspension.
Additional heterogeneity was caused during burial diagenesis by nonuniform precipitation of authigenic calcite and clays in fine and 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. Log and core data were used to establish net-pay cutoffs of greater than or equal to 15% porosity (for permeability of 1 md), less than or equal to 60% water saturation, and less than or equal to 15% volume of clay. During Phase II of the project, knowledge gained from reservoir characterization and simulation will be applied to increase recovery from a pilot area.