J. R. J. Studlick, R. D. Shew, G. L. Basye, J. R. Ray
A pilot conducted at Little Creek field, Mississippi, in the 1970s indicated that the injection of carbon dioxide (CO2) could lead to the successful recovery of additional oil reserves even after waterflood operations. It was realized early that a large volume of CO2 would be required for enhanced oil recovery operations in Little Creek and other prospective fields.
Shell's search for CO2 in the area began in the early 1970s. Exploratory drilling for hydrocarbons as early as 1950 had indicated high concentrations of CO2 present in central Mississippi. These occur in salt-generated structures north and east of the intrusive Jackson igneous dome; the area is therefore termed the N. E. Jackson Dome Source Area. CO2 generation is believed to have occurred by the thermal metamorphism associated with the intrusion of Jurassic-age carbonates. The CO2 migrated updip and is concentrated in the Buckner, Smackover, and Norphlet Formations at depths of 14,000 to 17,000 ft. The objectives are sandstones and dolomites that are interpreted as dune and sabkha deposits. Reservoir quality is variable (abundant illite loc lly in the Norphlet and highly compacted sandstones in the Buckner) but generally good. Rates of 20 MMCFGD have been tested from these wells.
Many salt-related structures have been defined in the source area by seismic data. Leasing began in 1973 and drilling in 1977. Eight structures have been tested, with all but one encountering commercial CO2 accumulations. Shell has drilled 15 wells (13 successful, 1 junked and abandoned, and 1 dry hole) on 640- and 1,280-ac spacing. Gas compositions vary: Smackover CO2 is sour and will require treatment, whereas the Buckner and Norphlet sands contain sweet and semisweet CO2, respectively. Industry reserves in N. E. Jackson Dome exceed 6 tcf of gas.
Three fields are currently being flooded in southwestern Mississippi, and additional fields are under consideration. The pipeline is being extended from southwest Mississippi to southern Louisiana to supply CO2 for additional enhanced oil recovery candidate fields.
AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.