Addressing Key Uncertainties During Production Analog Identification Process in a Heavy Oil Pool of the Upper Miocene Potter Sandstone, Midway-Sunset Field, Kern County, California

Omur Orhan and Sean O'Connor
Aera Energy LLC, 10000 Ming Avenue, Bakersfield, CA 93311

Distribution of Conglomerates in a Submarine Canyon System, Upper Miocene Potter Sandstone, Midway-Sunset Field, Kern County, California” by Sean O’Connor identifies zones of poor productivity that are located in the lower portion of the Potter sands. Excluding these lower quality sands, structural geology and SoPhiH map indicate that a good analog for the study area (Bolivar Lease) is the north adjacent lease (Anderson). However, other uncertainties such as remaining oil in Bolivar, impact of shale continuity on performance and steam-to-surface concerns had to be addressed. The Anderson-Goodwin(A-G) lease located down dip of Bolivar has over 25 years of cyclic steam operations. The concern was that oil in Bolivar may be heated and drained to A-G. Temperature logs were taken in existing Bolivar wells to determine potential oil drainage and remaining oil. Shale layers exhibit more aerial continuity in Anderson than in Bolivar. Lack of shale barriers could mean less efficient heating because injected steam may migrate vertically instead of moving along the reservoir beds. We compared well performance in Anderson – where shale layers seem to be more continuous- to well performance in a portion of Anderson-Goodwin where shale discontinuity is similar to Bolivar. The air sands of Potter reservoir outcrop to surface in Bolivar and therefore lead to steam-to-surface concerns. We studied steam movement in air sands and pressure and temperature gradient between air and oil sands. In addition, material balance between injected and produced volumes were compared. Although steam-to-surface did not pose a significant risk, we have identified areas of no-drilling zones near the outcrops and proposed temperature observation wells to monitor steam and heat migration to outcrops.

AAPG Search and Discovery Article #90076©2008 AAPG Pacific Section, Bakersfield, California