Weeks Island "S" Sand Reservoir B Gravity Stable Miscible CO2 Displacement, Iberia Parish, Louisiana

Abstract

Abstract Shell, in conjunction with the United States of America Department of Energy, is conducting a gravity stable displacement field test of the miscible CO2 process. The test is being conducted in the portion of a fault sealed reservoir lying below a subsea depth of -12,750 feet. Injection of the CO2 slug at the producing gas-oil contact commenced-in October 1978. Injection of the 860 MM cubic foot slug was completed in February of 1980. The slug of CO2 was moved downward through the watered out sand by production of downdip water. The leading edge of the displacement has reached the producing perforations and production of the oil column commenced on January 26, 1981. Conventional cores and the log-inject-log technique were used to determine residual oil saturation in a well drilled as the pilot producer. Pulsed neutron logging devices have producer. Pulsed neutron logging devices have been used to detect the CO2 slug and monitor its subsequent movements in the vicinity of the production well. The monitor logs indicate the production well. The monitor logs indicate the thickness of the oil column had increased during the displacement to the production perforations located 130 feet below the level of CO2 injection. The 23 foot oil column remaining at initiation of the project had apparently grown to 57 feet. PVT samples and production data indicate CO2 has penetrated the oil column and free gas is being produced with the oil. However, the qualitative measurements of the logs do not indicate a large gas or CO2 content in the oil column. Introduction The "S" Sand Reservoir B CO2 pilot is designed to field test a downward CO2 displacement in a steeply dipping, high temperature, high pressure Gulf Coast reservoir. Reservoirs of this pressure Gulf Coast reservoir. Reservoirs of this type typically are produced by natural water drives which leave a significant residual oil volume. Other major watered-out reservoirs in the Weeks Island Field have an estimated tertiary potential of 26 million barrels of oil which could potential of 26 million barrels of oil which could be recovered by CO2 displacement. Reservoirs of this type are not suitable for surfactant flooding as the temperature and water salinities are too high for currently available chemical systems, while the depth and usually good oil mobilities preclude any additional recovery by thermal stimulation. The downward CO2 displacement is designed to utilize gravity forces to stabilize the displacement and increase the sweep of the injected CO2. Following an evaluation of the residual oil saturation, injection of the CO2 slug commenced on October 4, 1978. Injection averaged 106 tons of CO2 per day and injection of the 50,000-ton slug was completed on February 27, 1980. Neutron devices have been used to monitor the CO2 in the vicinity of the new downdip observation ana production well. The CO2 which was initially detected in the top of the sand has been found to be invading the watered-out sand. Appearance of oil at the production perforations in the new well indicates the oil column had increased in thickness. Flowing production was initiated from the oil column on January 26, 1981. PROJECT SETTING PROJECT SETTING The Weeks Island Field is located on a Gulf Coast piercement type salt dome. Hydrocarbon shows have been found in sands of the Pleistocene to Lower Miocene age at depths from 1,000 to 17,000 feet. Commercial production has been established in 37 Lower Miocene sands, predominately below a depth of 9,500 feet. predominately below a depth of 9,500 feet. P. 309