South Florida Basin

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Introduction

Fig 1 Location of South Florida Basin[1]

[2] The South Florida Basin is located in the southern half of Florida. [3]The basin was discovered in 1940 and covers around 50,000 square miles, this includes the southernmost one third of the Florida peninsula including the Florida Keys and eastern part of the Gulf of Mexico. Fig. 1 should give the general idea of what this basin covers. Onshore the basin contains only subtle structures with no faults or vertical features. But for the offshore portion it is almost the complete opposite, offshore the basin seems to contain complex structures that have potential to have contain an excellent source of hydrocarbons. The basin is also home to the Sunniland Shale Formation.

Sunniland Shale Formation

[4]The Sunniland Shale Formation is located within the South Florida Basin near the Gulf Coast and has depths well over 3000 feet below the surface as seen on Fig. 2. The formation was discovered in 1943, the formation is confined by a series of low permeability geological units that protect the groundwater from contaminations. This formation is rich in resources making it a prime target for horizontal drilling by oil companies. The formation has and will continue to supply with millions of barrels of oil.[5]The geologic risks associated with the formation can be caused from hydraulic fracturing itself. With continued drilling there is a chance that the water supply could be contaminated causing environmental hazards for organisms inhabited near the formation. Although damages in the formation is very minimal and doesn’t look to cause future concern.

Drainage Basins

Fig 2 Sunniland Formation[6]

[7]Within the South Florida Basin there are many areas that are considered drainage basins or water sheds. A drainage basin is an area of land that all the water that enters its area drains into a common body of water. There are a total of 29 watersheds located within the South Florida Basin. Within the basin these areas include the Gulf of Mexico, Atlantic Ocean, or other larger bodies of water located in the basin. The common separator of these basins are either hills or ridges.

Petroleum Geology

Seals and Traps

[8] In the South Florida Basin most of its hydrocarbon traps found within its formations are considered stratigraphic but there are a few structural traps that have been found within the area. The primary reservoir rocks limestone and dolomite and cycling evaporites found throughout the basin provide excellent seals. In the basin there are 2 petroleum systems found within it, the systems are separated stratigraphically by a regional evaporite seal and a regional anhydrate seal.

Migration

[8]There are indicators within the basin that show the presence of major fault systems and large structural features. Meaning that there is a good chance for pathways for hydrocarbon migration in the off shore parts of the basin. On shore there are a few structural features with potential to have the pathways needed for migration but for the most part there are little structural features and no noticeable fault lines.

Source Rock and Reservoir

[2]Due to the rich organic content and having the ability to store and deliver hydrocarbons, the rocks found within the South Florida Basin and formations like the Sunniland Shale are considered both a source rock and reservoir rock. The source rocks found in the lower part of the Sunniland shale are dark in color and referred to as dark carbonate interval. These rocks have a total organic carbon rating ranging from <0.4 to 3.0 weight percent. The reservoir rocks found within the formation consist of sucrosis dolomite that exhibit porosity levels ranging from "pinpoint to vuggy" in their beds. The primary reservoir rock are limestone and dolomite.

Current State and Future

[3]The South Florida Basin is still considered active today, this is due to the large amounts of reserves still being found both on shore and offshore. As of 2018 reserves have been drilled at Big Cypress National Preserve an area within the basin. But due to recent environmental hazards and other oil disasters there have not been a new well fields established since 1988. Offshore drilling in particular has been targeted by Florida politicians causing operations to slowly reduce over the years. For example in 2006, a moratorium was passed that prohibited drilling 125 miles within the coast of Florida. Also, the Deepwater Horizon Spill of 2010 is still a dark stain that we are still recovering from. But all is not lost for drilling within the basin. There are no on shore incidents reported within the basin and the moratorium is set to be lifted in 2022. With the development of technology and new safety precautions drilling in the South Florida basin should go back to being a powerhouse of a basin.

Additional Readings

Exploration of the Sunniland Formation of Southern Florida

The Geologic History of Florida

Watershed of Florida

References

  1. Lohr, C. D. (2015). Geologic Map of the South Florida Basin. Research Gate. https://www.researchgate.netfigure/Geologic-map-of-the-South-Florida-Basin-study-area-within-the-southeastern-United-States_fig1_304674232.
  2. 2.0 2.1 Pollastro, R. M., & Viger, R. J. (1998). Maps showing hydrocarbon plays of the Florida peninsula, USGS Petroleum Province 50. MAPS SHOWING HYDROCARBON PLAYS OF THE FLORIDA PENINSULA, USGS PETROLEUM PROVINCE 50. https://doi.org/10.3133/om226
  3. 3.0 3.1 Salisbury, S. (2018, January 15). Florida's onshore oil drilling industry began 75 years ago. The Palm Beach Post. https://www.palmbeachpost.com/news/florida-onshore-oil-drilling-industry-began-years-ago/rt8Zk5lpntjMv83DBidDOM/#:~:text=%E2%80%9CBreitburn%20also%20produces%20from%20the,was%20discovered%20in%20the%201940s
  4. Temple, B. (2012). Sunniland shale -An emerging South Florida basin liquids play. Oil and Gas Journal, 110, 56–58.
  5. Missimer, T. M., & Maliva, R. G. (2020, February 11). Hydraulic Fracturing in Southern Florida: A Critical Analysis of Potential Environmental Impacts. Natural Resources Research. https://link.springer.com/article/10.1007/s11053-020-09619-1.
  6. Sears, Stephen O. (1974) Facies Interpretations and Diagenetic Modifications of the Sunniland Limestone, South Florida. Southeastern Geology, Vol. 15, No. 4, p. 177-192. Published by Duke University Press.
  7. 8. Florida Drainage Basins Watershed Map. The Mitigation Banking Group. (2020, June 30). https://mitigationbankinginc.com/florida-drainage-basins-watershed-map/.
  8. 8.0 8.1 Pollastro, R. M., Schneck, C. J., & Charpentier, R. R. (2001). Assessment of Undiscovered Oil and Gas in the Onshore and State Waters Portion of the South Florida Basin, Florida— USGS Province 50.