Haynesville Formation Oil and Gas: The 2016 USGS Assessment of the U.S. Gulf Coast

Using a method based on geology, the U.S. Geological Survey estimates that the Upper Jurassic Haynesville Formation holds, on average, 1.1 billion barrels of undiscovered conventional oil and 195.8 trillion cubic feet of undiscovered gas that could be recovered with current technology. The estimate covers onshore lands and State waters of the U.S. Gulf Coast.

The assessment took in the Haynesville Formation and rock units of the same age along the Gulf Coast, from south Texas to the Florida Panhandle — Alabama, Arkansas, Florida, Louisiana, Mississippi and Texas. The formation is part of the Upper Jurassic–Cretaceous–Tertiary Composite Total Petroleum System. Within such a system, the rocks of each assessment unit share a similar history of layering, structure and oil and gas charge.

The approximate boundaries of the four assessment units along the Gulf Coast. USGS map, on a National Park Service base.

The geology

Mudstones in the Upper Jurassic Smackover and Haynesville Formations are the source of oil and gas across much of the area, feeding both conventional reservoirs and continuous (shale) ones.

• In the western Gulf, the conventional reservoirs are carbonates laid down on a shallow marine shelf, including grainstone shoals and bars and local pinnacle reefs.
• In the eastern Gulf, the conventional reservoirs are sandstones deposited by rivers and deltas, along the sea's margin, and on the marine shelf, slope and basin floor.
• The continuous reservoirs are mudstones interbedded with, or lying basinward of, the Haynesville carbonates, which include the Gilmer Limestone and Cotton Valley lime of the same age.

Four assessment units

Two units are conventional and two continuous; in places they overlap.

• Western Shelf Carbonate Gas and Oil: bounded to the north and west by fault systems, with shallow-marine carbonates and reefs reaching basinward to the edge of the depositional shelf.
• Eastern Shelf Sandstone and Carbonate Oil and Gas: bounded to the east and north by fault systems, with rocks reaching basinward to the continental shelf edge and beyond. Its reservoirs grade from river-delta and coastal deposits in the northeast to marine deposits on the shelf, slope and basin floor.
• Haynesville Shale Continuous Gas: defined by the mudstone around the greater Sabine uplift, where restricted marine circulation let organic-rich mud build up and be preserved. Its southern edge is the continental shelf edge.
• Haynesville Shale Peripheral Continuous Gas: in two separate parts of the area, defined by the rocks surrounding the main shale unit; its southern limit is the break between continental shelf and slope.

Key inputs for the shale units: the main unit's potential production area was put at 4,017,000 to 10,779,000 acres, with 70 percent of wells expected to succeed and each successful well expected to yield about 3.093 billion cubic feet of gas on average. For the peripheral unit, those figures were 50 percent and 1.562 billion cubic feet.

The results

Mean estimates, with the range between a 95 percent and a 5 percent chance (F95–F5):

Nearly all the oil is in the Eastern Shelf unit (1,098 million barrels). Most of the gas is in the shale: 129,663 billion cubic feet in the main shale unit and 44,943 billion in the peripheral one, against 21,191 billion in the two conventional units together.

Sources

• Haynesville Formation Assessment Team (Stanley T. Paxton, Janet K. Pitman, Scott A. Kinney, Nicholas J. Gianoutsos, Ofori N. Pearson, Katherine J. Whidden, Russell F. Dubiel, Christopher J. Schenk, Lauri A. Burke, Timothy R. Klett, Heidi M. Leathers-Miller, Tracey J. Mercier, Seth S. Haines, Brian A. Varela, Phuong A. Le, Thomas M. Finn, Stephanie B. Gaswirth, Sarah J. Hawkins, Kristen R. Marra and Marilyn E. Tennyson), Assessment of Undiscovered Oil and Gas Resources in the Haynesville Formation, U.S. Gulf Coast, 2016, USGS Fact Sheet 2017–3016, April 2017. https://doi.org/10.3133/fs20173016
• Results: USGS Energy Resources Program, https://energy.usgs.gov