DETAILED CHARACTERIZATION OF A SALINE FORMATION FOR CARBON SEQUESTRATION: PALUXY FORMATION, CITRONELLE OIL FIELD, SOUTHWEST ALABAMA

The purpose of this study is to characterize the Paluxy Formation, which is a Lower Cretaceous saline formation that is actively being used to store CO₂ as part of the SECARB III Anthropogenic test in Alabama. This study is designed to understand the potential of the Paluxy to store commercial quantities of anthropogenic CO₂ through the analysis of cores and geophysical logs from three recently drilled wells in the Southeast Citronelle Oil Unit. Citronelle Dome is a simple salt-cored anticline that lacks faults and contains abundant reservoir sandstone bodies and mudstone, evaporite, and carbonate seals.

The Paluxy has an average thickness of about 1,100 feet in Citronelle Dome. The Paluxy Formation is a coarsening-upward succession composed of numerous stacked, aggradational sandstone-mudstone packages. Individual sandstone bodies have sharp bases, typically fine upward, and range in thickness from less than 10 feet to over 40 feet. Sedimentologic and paleontologic analysis indicates that the Paluxy Formation was deposited in a fluvial environment that included bedload-dominated fluvial systems and interfluvial paleosols.

Integration of petrologic data with geophysical logs was performed to analyze framework sandstone composition, sandstone diagenesis, and reservoir architecture. Results show that the sandstone units are predominantly arkosic. Porosity and permeability are well-developed in the sandstone especially in the Upper Paluxy, where average porosity and permeability values are 19 percent and 200 mD, respectively. Intergranular pores predominate, and intragranular pores are common in feldspar. Quartz is the most abundant authigenic cement and is expressed primarily as overgrowths; pore-filling calcite and ferroan dolomite also are common. Authigenic clay includes grain-coating illite and pore-filling kaolinite. An understanding of facies architecture, coupled with the associated depositional and diagenetic processes, provides a predictive framework for the management of commercial-scale CO₂ injection in the Paluxy Formation.