Overcoming Formation Damage in Heavy Oil Fields - A Comprehensive Approach

TAGUE, JAMES, Chevron Corp.

Most heavy oil production occurs from shallow, unconsolidated sandstone reservoirs. Unfortunately, these reservoirs are prone to multiple forms of formation damage including sand and fines migration, clay swelling, organic precipitation, scale, and formation alteration caused by thermal EOR. In many cases, standard industry practices fail to remove or prevent this formation damage from occurring for a variety of reasons including improper identification of the damage mechanism and selection of inappropriate remedial or prevention techniques.Recently, Chevron initiated a program designed to overcome formation damage in the West Coalinga field - a heavy oil field known for its susceptibility to formation damage. A comprehensive approach was used that began by accurately identifying and quantifying the causes and impact of formation damage. Once the causes of formation damage were identified, remedial and preventative methods were designed and tested. The results were tracked and analyzed using multi-variate statistics which quickly identified optimal treatments and assisted in developing candidate selection criteria. Finally, a set of standardized field procedures were designed and implemented in order to prevent further damage from occurring. This paper will present the comprehensive approach used in West Coalinga. It will discuss the analytical methods used to identify the multiple formation damage mechanisms, describe the spreadsheet and multi-variate statistical analysis used to determine optimal remedial treatments, and present the decision tree designed for use in the field. Overall, this paper should provide a useful methodology for improving production in any heavy oil field with multiple formation damage mechanisms.

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