Field Trial of Simultaneous Injection of CO2 and Water, Rangely Weber Sand Unit, Colorado

Abstract

Field Trial of Simultaneous Injection of CO2 and Water, Rangely Weber Sand Unit, Colorado. D.R. Robie, Jr, J.W. Roedell, R.K Wackowski* Abstract The Water Alternating Gas (WAG) process is commonly applied in CO2 floods to reduce the mobility, to improve the stability of the flood front, and subsequently to improve recovery. There have been many modifications in the process over time to improve retention and operating conditions. Examples include tapering of the WAG ratio (an increase in the WAG ratio) and reduction of the half cycle slug sizes (the pattern hydrocarbon pore volumes of CO2 or water injected before switching to the alternate fluid.). At the Rangely Weber Sand Unit, WAG's at injection wells must be performed manually. Simultaneous injection of CO2 and water (SI) is essentially the reduction of the half cycle slug size to the limit. Simulation suggested that improved recovery could be realized from the application of this technique. In addition, reduced half cycles were being applied at injectors in increasing numbers due to the reductions in the wide fluctuations in produced gas rates. This required additional time to manually switch the injection wells from one fluid to the other. Based upon potential improvements in recovery and work force utilization, a field trial was implemented to verity that the process could be successfully performed. This paper reviews the testing of various processes to perform SI, as well as the implementation of a larger scale trial. Introduction The Rangely Weber Sand Unit is in Rio Blanco County in northwestern Colorado, U.S.A, about 5 miles east of the Utah-Colorado border (Figure 1). It is the largest field in the Rocky Mountains in daily and cumulative oil production. Currently, there are 372 active producers and 300 active injectors, 259 of which are injecting CO2. Weber sandstone production was discovered at Rangely in 1933 by the California Company. Development of the field began in 1944 spurred by World War II oil demand, Initial 40-acre spacing development was completed in 1949. Infill drilling in the 1970's and 1980's reduced the spacing to 20-acre throughout nearly the entire field. P. 719