Reservoir Description of Luling Field, Caldwell and Guadalupe Counties, Texas

Marcia D. Hicks

The Cretaceous upper Edwards Formation of Luling field has been producing oil since the 1920's. The field was perceived to have remaining reserves, so a reservoir description was undertaken to: (1) describe the reservoir rock and subdivide it into unique zones, (2) determine remaining oil in place for each zone, and (3) prepare geological grids for reservoir simulation.

The three-phase project illustrates the procedure of a multidisciplinary analysis of a reservoir. Phase one included assembling all relevant data; preparing an accurate computer base map; correlating zones and developing a stratigraphic model based upon relating whole-core analyses, petrography, core description, and sweep efficiency to logs; and constructing structural and gross thickness maps using computer-generated grids. During this phase, drilling programs were initiated and mapping was updated as wells were drilled.

Phase two included calculating porosity from nonquantitative radioactivity and modern logs; determining petrophysical parameters from field salt water, modern logs, and cores; calculating oil saturation and net pay; and mapping porosity, net pay, and oil saturation using computer-generated grids. Near the end of this phase, booked reserves were redetermined and a lease was chosen for a reservoir simulation study.

Phase three included mapping porosity feet and hydrocarbon-pore feet using computer-generated grids, calculating remaining oil in place, archiving the maps and grids onto digital tape, and compiling the results into a report.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.