The Application of Slim-Hole Completions to Secondary Recovery

Abstract

Introduction Oil men are probably as tired of hearing about rising costs as they are of experiencing them. It goes without saying that we are vitally concerned with discovering less expensive methods of developing production, both primary and secondary. Slim-hole completions are believed to be a partial solution to this problem. Contrary to what many people think, slim-hole completions are not new. One operator, the Stekoll Petroleum Corp., has been completing wells with 2 7/8-in., or smaller, casing for 18 years. The purpose of this paper is to review this development and discuss its application to secondary recovery. Slim-hole completions should not be confused with slim-hole drilling. The primary purpose of a slim-hole completion is to save money. Quite often, the cost of drilling a small-diameter hole is more than that of a slightly larger one. In such cases, it is defeating the purpose of slim-hole completions to insist on the drilling of a smaller hole. History of Development In 1942, Stekoll initiated a water flood in the Bolton field of Montgomery County, Kans. The Bartlesville sand in this area lies at a depth of approximately 1,000 ft, and the property was developed as a flowing-type water flood. The completion cost of wells with 4-in. casing, which size was customary for the area, was compared with the cost of completions using 2-in. casing. This study indicated that the additional capital investment resulting from completing with the larger casing would be very substantial when applied to the entire property. Because of this and because of the shallow depth of the wells, it was decided that 2-in. line pipe would be used for casing in both producing and injection wells. As a result, total development costs were reduced by 33 1/3 per cent. A short time later, another Kansas water flood was developed on wider spacing, and producing wells were pumped instead of being flowed. It was here that the company first attempted to pump inside 2-in. casing using a reciprocating string of 1-in. line pipe as tubing and rods. An insert-type bottom-hole pump was adapted successfully. Operating costs over the past 15 years have been equivalent to those of conventional wells.