Gulf Oil Exploration and Production Company in conjunction with the Department of Energy is conducting a field test of the CO/sub 2/ miscible displacement process. The project is being conducted in the Mission Canyon Formation (lower Mississippian), a dolomitized carbonate reservoir which is currently in the middle stage of primary depletion. Location of the field is in west-central North Dakota at the approximate center of the Williston Basin. Four wells were drilled in an inverted four-spot configuration within the five-acre minitest. The central well is the injection well surrounded by three non-producing observation wells. Oriented cores were obtained from each well for detailed reservoir characterization and laboratory testing. In addition, pulse and injectivity tests were obtained. Results from these tests were used to upgrade two reservoir simulation models. Various parameters within the models were modified to determine the most efficient injection plan. A WAG-type injection sequence involving alternate slugs of water and CO/sub 2/ will be employed. The test is designed to establish the incremental recovery, over waterflooding, by a miscible CO/sub 2/ flood in an oil reservoir.