ABSTRACT: Three-Dimensional Mapping Techniques in the Analysis of a Mature Steam Drive
R. A. Barrett
The use of interactive volumetric modeling (IVM), a three-dimensional mapping software package that employs a three-dimensional gridding algorithm, greatly assisted in evaluating the efficiency of a mature steam drive in the South Belridge field, Kern County, California. The productive horizon consists of Pleistocene-aged unconsolidated oil sands interbedded with impermeable shales. The sand-shale architecture is controlled by a prograding of fluvio-deltaic depositional system. For mapping convenience, the Tulare reservoir has been divided into five zones, the lowermost "E" zone to the uppermost "A" zone. In ascending order the reservoir can be characterized by the following description: Lowest in the section are isolated to coalescing mouth bars, followed by fairly conti uous lower delta plain interdistributary channels, isolated meandering stream channels of the upper delta plain, and uppermost, a braided stream complex of amalgamated channel sands. A drilling program consisting of 68 wells evenly distributed over 100 acres supplied ample log and core information and in effect presented a "snap-shot" of the reservoir in its maturity. Drilling revealed zones with excellent sweep and, conversely, zones that had been bypassed by the steam drive. By using well-log data tied to core data three-dimensional maps of individual sands incorporating structure, sand thicknesses in a multicolored format were generated to show the changing oil saturation values throughout the reservoir. The graphic presentation of these data on the CRT allows the user to rotate and c t through the sand body of interest revealing virtually an infinite number of perspectives. A hard copy option gives the user a printed map of any perspective of interest. The software is also capable of precise volumetric calculations of the oil remaining in the reservoir. Combining these data with three-dimensional temperature and sand-shale geometry maps, it was possible to understand how varying sand-shale geometries controlled past steam distribution and to optimize future steam distribution with a resultant increase in the ultimate recovery.
AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990