Fault and Seal Analysis in the DeSoto Canyon Salt Basin: Implications for Offshore CO₂ Storage

Abstract

Subsurface geologic storage of CO₂ can play a major role in offsetting greenhouse gas emissions, and offshore storage may be a viable solution due to legal advantages and large storage capacity >20 Gt in Cretaceous sandstone. Reservoirs are overlain by thick sections of tight mudrock, limestone, and chalk, which form regionally extensive seals. Understanding the structural styles and sealing properties of the associated reservoir rocks and seals is therefore essential for safe and effective CO₂ storage.

The structural framework in the Mississippi-Alabama-Florida shelf of the Gulf of Mexico includes the DeSoto Canyon Salt Basin, the Middle Ground Arch, and the Tampa Embayment. The Central DeSoto Canyon Salt Basin is structurally complex due to the presence of peripheral faults, salt pillows, salt rollers, and salt diapirs. Multiple faults associated with the peripheral faults and salt pillows displace the potential Cretaceous reservoirs and seal intervals. Reactivation tendency and seal analysis of the major faults shows that while the slip tendency is small, whereas the dilation tendency and potential for cross-formational flow is relatively high, particularly where reservoir strata in the footwalls are juxtaposed with sealing strata in the hanging walls. Geomechanical analysis of reservoir and seal strata indicates that prospective reservoirs and associated seals are stable if injection pressure does not exceed fracture pressure.

Favorable CO₂ injection sites are available throughout the stable shelf areas of the DeSoto Canyon Salt Basin where faults with high dilation tendency are absent above the Jurassic section. Future research should focus on further geomechanical, pressure, and flow simulation of the potential reservoirs and associated seals.

AAPG Datapages/Search and Discovery Article #90350 © 2019 AAPG Annual Convention and Exhibition, San Antonio, Texas, May 19-22, 2019