Sequence Stratigraphy of the Tuscaloosa from Cranfield Field, Mississippi—a Carbon Sequestration Study in from Enhanced Oil Recovery Operation
The Southeast Regional Carbon Sequestration Partnership (SECARB) field project conducted by the Gulf Coast Carbon Center with support from the National Energy Technology Laboratory (NETL) and the U.S. Department of Energy (DOE) and managed by the Southern States Energy Board (SSEB) at Denbury Resources’ Cranfield Field in southwest Mississippi was chosen to test monitoring strategies for CO2 storage. Cranfield field, Mississippi, was discovered in 1946 and abandoned in 1965 at the end of primary oil and gas production. Denbury Resources, Inc. currently owns the field and is in the first year of a CO2 EOR flood. Design of a monitoring strategy to assess the performance of this EOR flood in sequestering CO2 requires a good understanding of the reservoir framework.
The Lower Tuscaloosa injection zone comprises medium to coarse sandstone and granule to pebble conglomerate with abundant chert fragments. Core and well log facies indicate the Tuscaloosa at Cranfield has a sharp basal contact. Limited available core and wireline-log data indicate much finer grained sandstone, siltstone, and mudstone below the basal Tuscaloosa contact. High-frequency correlations within the lower Tuscaloosa indicate multiple incision events within an overall upward-fining succession from the basal contact upward to a thick marine mudstone section, informally known as the marine Tuscaloosa. According to sequence stratigraphic principles, the sharp basal contact and coarse-grained nature of the basal units (a braided-stream-braid-plain depositional system) indicate a lowstand systems tract that grades upward into a fine-grained marine succession (a transgressive systems tract, TST). The lowstand incises into an underlying (Washita Formation) highstand systems tract, HST. The sharp basal contact is a sequence boundary. A maximum flooding surface constitutes the top of the TST within the marine Tuscaloosa. An overall upward-coarsening succession above the maximum flooding surface constitutes an overlying Tuscaloosa HST. Assessment of the pressure and fluid flow in the injection zone is limited by complexity in lowstand sand body geometry that creates uncertainty in interpretation of flow system continuity. A more continuous sandstone in the Tuscaloosa HST is used as a pressure monitoring zone.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009