More Than 12 Years of Experience with a Successful Conformance-Control Polymer Gel Technology

SYDANSK, ROBERT, Marathon Oil

The Cr(III)-carboxylate/acrylamide-polymer oilfield gel technology was conceived in our laboratories in 1985. This polymer gel technology, where chromic triacetate is often the preferred crosslinking agent, has been widely applied successfully as conformance-control, sweep-improvement, water-shutoff, and gas-shutoff treatments. Over 1400 of these oilfield gel treatments have been pumped worldwide as of May 1998. Marathon has pumped internally over 500 of these Cr(III)-carboxylate/acrylamide-polymer gel treatments. Thus, over 900 of these gel treatments were pumped by non-Marathon oil operators. Two formulation versions of the Cr(III)-carboxylate gel technology have been developed. The first version involves the use of high-molecular-weight polymers and is used to treat fractures and other high permeability (multi-darcy) anomalies within petroleum reservoirs. The second version of this polymer gel technology involves the use of low-molecular-weight polymers and is applied as near-wellbore treatments in matrix rock (unfractured) reservoirs for the purpose of imparting total permeability shutoff.The Cr(III)-carboxylate/acrylamide-polymer gel technology and its pertinent features will be briefly described, along with a brief history of its development. Highlights of illustrative field results of this polymer gel conformance-control technology, both within and outside our company, will be presented. This will include, but not necessarily be limited to, the following field examples. As a result of applying the first 17 sweep-improvement injection-well Cr(III)-carboxylate/acrylamide-polymer gel treatments to a combination of naturally fractured carbonate and sandstone reservoirs in the Big Horn Basin of Wyoming, Marathon has recovered 3,650,000 BBL of incremental oil production at an average cost of $0.21/BBL. Our company has applied 108 of these gel treatments to roduction wells as water-shutoff treatments. These water-shutoff gel treatments have shut off a total of 236,000 BWPD, while generating a gross initial 3,000 BOPD of incremental oil production. The paper will reference and briefly review SPE papers that have reported on the successful application of this gel technology as: 1) 37 gas shutoff treatments in the Prudhoe Bay reservoir, and 2) ten injection-well sweep-improvement treatments applied during the CO2 tertiary WAG flood in the naturally fractured Tensleep sandstone formation of the Wertz field in Wyoming.This applied technology paper will provide an overview of what a decade-plus of experience with our successful and widely applied conformance-control polymer gel technology has taught us. We will begin by discussing important considerations in classifying and evaluating conformance problems--including geological considerations. The attributes of good candidate wells will be reviewed. Also, requirements of wells and well patterns to be successfully treated with polymer gels will be discussed. Guidelines will be presented, based on our experience, as to where the various types of oilfield polymer gel treatments are best and most successfully applied. We will list and discuss treatment aspects that must be successfully implemented in order to assure success when applying fluid-shutoff and sweep-improvement gel treatments. Discussed also will be what properties one should look for in an ideal conformance-control polymer gel technology. High temperature polymer gel treatments and temperature limitations will be briefly reviewed. Risks and potential pitfalls of conformance-control polymer gel treatments, along with the paramount importance of conducting a sound quality-control and quality-assurance program during these treatments, will be discussed.

AAPG Search and Discovery Article #90911©2000 AAPG Pacific Section and Western Region Society of Petroleum Engineers, Long Beach, California