ABSTRACT: Application of Horizontal Drilling in the Development of a Complex Turbidite Sandstone Reservoir, Elk Hills Field, Kern County, California

Stephen A. Reid, George S. McJannet, Orville D. Hart

Horizontal drilling techniques have been used at the Elk Hills field to more effectively produce the complex 26R reservoir. This Stevens zone reservoir of the Miocene Monterey Formation contains turbidite sediments deposited in a deep-sea fan setting and consists of several distinct sandstone layers averaging 150 ft thick and usually separated by mudstone beds. Layers in the reservoir dip as much as 50° southwest. An expanding gas cap makes many vertical wells less favorable to operate. Horizontal completions were thought ideal for the pool because (1) the original oil-water contact is level and believed stable, (2) water production is low, (3) a horizontal well provides for a long production life; and (4) several sandstone layers can be produced through one well.

For the first well, the plan was to redrill an idle well to horizontal along an arc with a radius of 350 ft. The horizontal section was to be up to 1000 ft long and extend northeast slightly oblique to dip just above the average oil-water contact. The well was drilled in September 1988, reached horizontal nearly as planned, was completed after perforating 210 ft of oil sand, and produced a daily average of 1000 bbl oil and 8 bbl of water. However, structural influence was stronger than expected, causing the horizontal drill path to turn directly updip away from the bottom-hole target area. The well also encountered variable oil-water contacts, with more than half the horizontal section possibly water productive.

Geologic and drilling data from the first well were used for planning another well. This well was drilled in October 1989, and was highly successful with over 1000 ft of productive interval.

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