Abstracts: Development of Marginal Fractured Siliceous Shale Reservoirs with Horizontal Wells in Lost Hills Field, California

BOWERSOX J. RICHARD

Bakersfield Energy Resources has successfully drilled and completed two medium-radius horizontal wells in Lost Hills oil field, California. These wells, Truman Fee #363H-26 and Ellis Two #48H-10, were drilled to test development of the marginal areas of reservoirs in the naturally fractured siliceous shales of the Reef Ridge and Monterey Formations. These areas lie downdip where porosity and hydrocarbon saturations are relatively lower as found by vertical wells drilled, cored, and logged to test reservoir and mechanical rock properties of the target reservoirs. Vertical wells drilled on the reservoir margins are marginally economic producers. So, the issue was simple economics. Would a horizontal well be a cost-effective alternative to several vertical wells? Our experience says maybe.

The first, Truman Fee #363H-26, Section 26, T27S, R21E, MDB&M, was drilled in July 1992 to a total depth of 8370 ft KB (7375 ft TBD KB) to develop the quartz diagenetic facies of the upper McClure Shale member of the Monterey Shale. Horizontal reach of this well was 1000 ft as an alternative to drilling three vertical wells. It was drilled down true formation dip, perpendicular to the natural fracture orientation, at an average angle of 80 degrees from vertical. Truman Fee #363H-26 was treated with five point-source massive hydraulic fracture stimulations in the upper McClure Shale and two stages of about 150 ft each in the lower Reef Ridge Shale. Initial production was 250 BOPD of 37 degrees API gravity oil and 520 Mcfgpd compared to an average of 75 BOPD and 500 Mcfgpd for surrounding wells. With its completed cost comparable to only two vertical wells, this appeared to be a commercial success. Unfortunately a shallow casing part, with a submersible pump stuck below the part, ended the life of Truman Fee #363H-26 after only about two months of production.

The second, Ellis two #48-10, Section 10, T27S, R21E, MDB&M, was drilled in May 1996 to a total depth of 5743 ft KB (3062 ft TVD KB) to develop the opal-A/opal-CT transition diagenetic facies of the upper Reef Ridge Shale. Horizontal reach of this well was 2000 ft drilled updip from the reservoir margin towards its center, perpendicular to the natural fracture orientation, at an average angle of 100 degrees from vertical. Ellis Two #48H-10 was treated with 13 point-source massive hydraulic fracture stimulations spaced about 125 ft apart. Initial production was 295 BOPD of 38 degrees API gravity oil and 845 Mcfgpd and declined to 110 BOPD and 817 Mcfgpd after 30 days of production. This well is probably not economic due to higher then anticipated well costs and lower then anticipated production.

Search and Discovery Article #90945©1997 AAPG Pacific Section Meeting, Bakersfield, California