Identification of an Undersaturated Zone and its Effect on Steamflood Performance/Development at Lost Hills, California

KIRST, TIMOTHY L., and JEFFREY R. KERNS, Mobil Exploration and Production, Bakersfield, CA

The Pliocene Etchegoin B Sand at the Lost Hills Two property possesses excellent steamflood EOR potential with approximately 75% of OOIP remaining. Analysis of recently obtained crestal and flank core revealed that low primary oil saturations and permeabilities existed in the upper one-third of the reservoir resulting from high amounts of volcanic debris, diatomaceous material, and smectite. This condition resides in sediments deposited within a delta plain/lagoonal facies which is correlative property wide. When desaturated by production

from gravity drainage, residual oil saturations are as low as 10% along crestal areas. The positioning of this severely desaturated zone in the upper third of the reservoir was viewed as potentially harmful to steamflood effectiveness because it could act as a steam thief. To ascertain the viability of steamflooding this reservoir, a pilot was designed and implemented.

Steam injection began in mid-March 1990. Performance to date exceeds numerical model predictions. Systematically gathered temperature data indicates successful steam containment within the lower two-thirds of the reservoir. In addition, there are no indications of significant steam lost to the water leg. Consequently, the pilot will soon be expanded to a full-scale steamflood.

Steamflooding is capital intensive in both initial equipment investment and steam generation over project life. Any design or expense improvement gained from pilot monitoring will translate to improved full-scale project economics. Careful monitoring of the pilot should result in design improvements that will reduce the capital requirements and substantially improve full-scale economics.

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