Evaluation of the Coalinga Polymer Demonstration Project

The Coalinga Polymer Demonstration Project was designed by the Shell Oil Company to show the relative merits of water and polymer flooding in a reservoir with medium-viscosity oil. Located in the East Coalinga Field, Fresno County, California, the 149-acre project area contained four +-22-acre inverted five-spot injection patterns. The target reservoir was a 350-foot-thick, unconsolidated sandstone formation at about 2000 feet. Following nearly two years of water injection and an extensive field polymer injectivity and filtration study, polymer injection into four injection wells began in May 1978. The production response to polymer injection was less than expected and the project was terminated early. Two major contributing factors that resulted in the poor performance were: (1) a loss of polymer injectivity; and (2) a lack of movable oil in the project area. The loss of polymer injectivity was thought to be caused by near wellbore plugging by unhydrated biopolymer and bacterial debris. After polymer injection had begun, a subsequent petrophysical study indicated that little movable oil remained in the project area after primary production. The project was designed and operated in an expert manner. However, recommendations are made on how the project could have been improved if initiated today. These include:more » (1) Appropriate petrophysical studies, conducted prior to project initiation, should be conducted to guide the selection of the most suitable area within the feld. (2) Polymer injectivity could be improved by completing wells in unconsolidated formations with a screen and liner/gravel pack and by using currently available biopolymers which contain less bacterial debris. These practices will minimize the amount of filtration that is required on location. 7 figures, 2 tables.« less