ABSTRACT: Reservoir Delineation with Cross-Hole Tomography in Midway Sunset Field, California

Tien-When Lo, Philip Inderwiesen, Danny Melton, Don Howlett

The petroleum in the Midway Sunset field, California, is a heavy, tarlike substance that requires the enhanced oil recovery (EOR) method of steam flooding for production. The production engineer is interested in what inhomogeneities in the reservoir may adversely affect the steam flood operation. Also, because steamflooding is expensive, the production engineer needs to know when the reservoir has been sufficiently steamed in order to shut down the operation in a timely manner.

In April 1989, Texaco conducted a cross-hole tomography survey in the Midway Sunset field with the intent of aiding the production engineer in making decisions on the steamflood operation. Specifically, we had two objectives in mind: (1) to tomographically image inhomogeneities between two boreholes before steam flooding, and (2) to monitor the temporal changes in the reservoir after steam flooding with a second set of cross-hole seismic data collected approximately 9 mo later.

Texaco contracted the downhole source and receiver to collect the data and processed the data in-house. A velocity tomogram and a porosity tomogram were constructed, delineating the following features of this reservoir: (1) the irregular boundaries between several tar sand layers, and (2) the porosity value at every point within the producing formation between these two wells. The spatial resolution is about 20 ft. Tomography results were checked with log information in both wells and found to agree satisfactorily.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990