Evaluation of a Complex Sandstone Reservoir for EOR

PATHAK, P., ARCO International, Jakarta, Indonesia, K. D. KUCH, and T. P. MOOREFIELD, ARCO Oil and Gas Company, Bakersfield, CA, B. G. KRIEL, E. S. PASTERNACK, and J. H. LIGON, ARCO Oil and Gas Company, Plano, TX, and S. J. SALTER, ARCO Oil and Gas Company, Midland, TX

The South Cuyama reservoir is a mature field in California that has both complex geology and a complex operational history. Two factors were considered to be critical in determining the viability of a proposed micellar-polymer flooding process in South Cuyama. First, the faulted nature of the field emphasized the importance of sand continuity between injectors and producers. Second, in order to make the estimated oil recovery (EOR) process profitable, the remaining oil had to be large enough to justify the added expense of process implementation.

A multidisciplinary study of the South Cuyama field was undertaken by engineers, geologists, and geophysicists from research, engineering, and operations organizations. An initial review of reservoir and production data indicated an expected remaining oil saturation of 35-40% based on an OOIP estimate of 450-510 MMSTB. A geological/geophysical study, including a high-resolution three-dimensional seismic survey, indicated that reasonably good sand continuity was hampered by the occurrence of numerous small faults previously unrecognized by mapping with well data alone. Log-Inject-Log and Single Well Tracer tests were undertaken in several existing wells to determine the remaining oil saturation. A new well was drilled and extensively cored indicating remaining oil saturation in the 9-2 % range. Using the new data, an OOIP was recalculated to be 390 MMSTB, 24% less than the original estimate.

The results of the study indicated that South Cuyama was not a good candidate for micellar-polymer flooding. The methodology presented here resulted in the determination of this fact without actually running a pilot test, thereby saving considerable expense.

AAPG Search and Discovery Article #91009©1991 AAPG-SEPM-SEG-SPWLA Pacific Section Annual Meeting, Bakersfield, California, March 6-8, 1991 (2009)