Improved Oil Recovery Using Horizontal Wells at Elk Hills, California

Abstract

Abstract Eight horizontal wells have been drilled and completed in a steeply dipping Stevens sand reservoir in the Elk Hills field, Kern County, California. The subject reservoir, called the Stevens 26R, is a turbidite channel sand deposit one mile wide, three miles long, and one mile deep. Formation beds have a gross thickness up to 1,500 feet and dips as high as 60 degrees on the flanks. The original oil column of 1,810 feet has been pulled down to 200 feet by continual production since 1976. The reservoir management operating strategy has been full pressure maintenance by crestal gas injection since 1976. The steep dip of the formation makes gravity drainage the dominant drive mechanism. Additionally, improved recovery is coming from cycling dry gas through the large secondary gas cap region. The prudent placement of the horizontal wells above the oil/water contact promises to improve oil recovery and extend the operating life of the reservoir. Field results are given to compare the performance of the horizontal wells with the conventional wells. The horizontal wells produce at higher rates, lower draw downs, and lower gas/oil ratio which will extend the life of the project and result in higher recovery.