EVALUATION OF THE SUNNILAND FORMATION OF THE SOUTH FLORIDA BASIN FOR CARBON DIOXIDE CAPTURE AND SEQUESTRATION AND ENHANCED OIL RECOVERY

Concerns about the effects of elevated atmospheric carbon dioxide (CO₂) levels on global climates have led to the creation of a Federal cap-and-trade program to control and reduce CO₂ emissions. Power plants have been identified as the biggest anthropogenic contributors. Carbon dioxide capture and sequestration (CCS) in geologic formations is a proposed solution for reducing atmospheric CO₂ and is currently being considered by Florida electric-power utility companies. Carbon dioxide-enhanced oil recovery (CO₂-EOR) is a type of CCS where CO₂ is injected for the purpose of increased oil recovery from reservoirs; however, the technology also serves to sequester a large portion of the CO₂ that is injected for oil recovery. The Sunniland Trend commercial oil fields of the South Florida Basin have been identified as potential sites for CCS and CO₂-EOR using the Sunniland Formation as the sequestration reservoir. The Sunniland Trend is a slightly arcuate band in southwest Florida that is about 145 miles long and 20 miles wide, and contains oil plays at depths around 11,200 feet, located within the carbonate Sunniland Formation and confined to mound-like structures made of coarse fossil fragments, mostly rudistid reefs. The Sunniland Formation is ‘sealed’ by the overlying Lake Trafford Formation, a sequence of limestone, dolomite, and anhydrite, and the underlying Punta Gorda Anhydrite, which, together with lateral decreases in permeability, form the stratigraphic traps that hold the oil of the Sunniland Formation in place. Average porosity values are 10-20% for porous zones within the Sunniland Formation along the Sunniland Trend, and are as high as 30% in some areas. The Sunniland Formation was identified as potentially suitable for CCS operations, including CO₂-EOR, due to factors such as its geographic location in relation to power plants, appropriate depth, high porosity and available storage capacity, and adequate caprock. Commercial/pilot projects for geologic CCS are being conducted within the United States, but no CCS projects have been planned or conducted in Florida; therefore, CCS in saline carbonate aquifers of Florida represents a new and as-yet unproven sequestration technology for reducing CO₂ that is potentially applicable around the world.