Paper: Success Of A High Friction Diverting Gel In Acid Stimulation Of A Carbonate Reservoir, Cornell Unit, Wasson San Andres Field, West Texas

The Cornell Unit is a 778.2 m2 (1,923 acre) waterflood project in the Permian, San Andres, dolomite reservoir located in the Wasson Field, Yoakum County, Texas. The Unit currently consists of 66 producing wells and 26 injection wells. Production is approximately 1430.9 m3 (9,000 barrels) of oil per day, 1367.3 m3 (8,600 barrels) of water per day and 240,693.2 m3 (8,500,OOO cubic feet) of gas per day. Daily injection averages 4133.7 m3 (26,000 barrels) of water. Early in 1979, it was recognized that a substantial reconditioning and infill drilling program was needed to prepare the Unit for a tertiary recovery project. Casing of open hole injectors and selected producers began in mid-1979 followed by infill drilling in early 1980. Well stimulation by acid treatment is a routine completion procedure for these wells and, initially, the means to positively distribute the acid to the perforations was through the use of closely spaced straddle packers. Frequently, it was found that most of the perforations communicated while being acidized. Because of this communication, not only would other mechanical means of diversion within the well bore be unsatisfactory but diverting agents, which rely upon differential pressure temporarily sealing over the perforations, also would fail when the pressure across the perforation equalized. The need for a diverting agent which actually would enter the formation taking the acid and temporarily block it led to useage of a gelled and complexed guar gum material, commonly called High Friction Gel*. The success of High Friction Gel in achieving better overall distribution of the acid treatment is presented in this paper.