Abstract: Reservoir Description and Interpretation Utilizing Whole Core Analysis from the Cole Sandstone (Jackson), Orlee Field, Duval County, Texas

BILLINGSLEY, LEE T.
Sandia Oil & Gas Corp., San Antonio, TX

Thirty ft of full-diameter core was recovered from a development well in a shallow (1700 ft) oil field in Duval County, Texas. The field produces 20 gravity oil from the Cole Sandstone in a stratigraphic trap. The cored well is located near the downdip edge of the reservoir. A lowinvasion, hydro-lift core recovery system was utilized due to the unconsolidated nature of the reservoir. Core recovery was 100%. Standard petrographic and core analysis techniques were applied. In addition, special core analysis techniques were employed to determine relative permeability, capillary pressure, formation factor (m), resistivity index (n), and watercut.

Analysis and description of the core indicates the reservoir is a non-burrowed, massive to faintly subhorizontally laminated, calcareously cemented, sublithic, subarkosic arenite. The reservoir sandstone contains minor amounts of smectite and chlorite clay-sized particles. Reservoir porosity is 30-34% with permeability of 1200 - 5300 md. In contrast, over- and underlying nonreservoir sandstone is highly burrowed. Resulting porosity is lowered to 27-29% and permeability is 200-700 md. The "m" and "n" factors are 1.60, based on core analysis.

The special core analysis indicates the reservoir will produce oil with a high water cut. For example the part of the reservoir with 5000 md permeability will produce about 95% water at a water saturation of 50% and 80% water at 35% water saturation.

AAPG Search and Discovery Article #90932©1998 GCAGS/GCS-SEPM Meeting, Corpus Christi, Texas