ABSTRACT

A major problem of thermal maturity exists in the South Florida Sub-basin as the bottom hole temperatures (BHT) of deep wells in the sub-basin are below the published minimum temperature required for hydrocarbon generation. This temperature has been calculated as 221°F, based on 5,358 oil reservoirs in the Gulf Coast, ranging from 221°F and 260°R Unfortunately, South Florida oil-producing wells have a BHT average of 114.5°F, indicating that the Sunniland interval is non-mature. The quantity of organic carbon is a basic property for assessment of the petroleum potential, especially with regard to rocks deficient in organic matter. Regardless of favorable thermal maturity, type, or organic matter, if the rock contains relatively small amounts of TOC it is unlikely to yield commercial amounts of petroleum. Based on previous South Florida studies, 0.4% TOC has been judged as the minimum requirement for source rocks in the sub-basin. The quantity, type, and thermal maturity in the Dollar Bay Formation are better than in the oil-producing Sunniland Formation lower in the stratigraphic column. The Triassic and Jurassic rocks have reported TOC values ranging from 0.07% to 0.90%; however the lower Pumpkin Bay carbonates in the Humble #1-Lehigh Acres range from 0.42% to 0.47%; while there is a 10-ft-thick 0.82% carbonate bed in the Dollar Bay Formation in the well Coastal Petroleum #1-Tiedtke in Glades County. This study advocates a revision of the accepted standards for maturity.