Shell, in conjunction with the Department of Energy, is conducting a gravity stable displacement field test of the miscible CO/sub 2/ process. The test is being conducted in a 12,800-foot deep Gulf Coast reservoir. Injection of the CO/sub 2/ slug at the producing gas-oil contact commenced in October 1978. The slug of CO/sub 2/ is being moved downward by production of downdip water. Injection of the 50,000-ton slug was completed in February of 1980, and production is projected to start in the third quarter of 1980. Conventional cores and the log-inject-log technique were used to determine residual oil saturation in a well drilled as the pilot producer. The new well is being used to monitor the downdip displacement. Pulsed neutron logging devices have been used to monitor the downdip displacement. Pulsed neutron logging devices have been used to monitor the CO/sub 2/ movement in the vicinity of the observation well. The logs have been successful in detecting the CO/sub 2/ slug and its subsequent movement. Production tests of the log-inject-log perforations, located in a previously watered-out portion of the sand, 48 feet below the point of CO/sub 2/ injection in the offset well, have indicated an oil column has passed the observation perforations. Further tests and logs indicated CO/sub 2/ had reached the observation perforations in November 1979. These perforations were then squeezed off and new production perforations were placed at the final completion depth 130 feet below the level of CO/sub 2/ injection.