U.S. Geological Survey, U.S. Gulf Coast Petroleum Systems Project. Fact Sheet 2018–3043, August 2018.
The result: a mean of 1.5 billion barrels of oil and 4.6 trillion cubic feet of gas — undiscovered and technically recoverable — in the Tuscaloosa marine shale, onshore and in State waters of Louisiana, Mississippi, Alabama and Florida.
The rock
- What: an organic-rich, siliceous mudstone from the late Cenomanian to Turonian (Late Cretaceous). It is a continuous, self-sourced reservoir — the oil and gas formed in the same rock that holds them.
- Thickness: up to 495 feet.
- Depth: producing horizontal wells reach it at 11,000 to 14,000 feet.
- System: part of the Upper Jurassic–Cretaceous–Tertiary Composite Total Petroleum System of the U.S. Gulf Coast.
Figure 1: the Tuscaloosa Marine Shale Continuous Oil Assessment Unit (red) and parts of the USGS Louisiana-Mississippi Salt Basins and Western Gulf provinces. Base map from the National Park Service. USGS.
Drawing the boundaries
The assessment unit (AU) covers central Louisiana, southern Mississippi, southern Alabama and Florida State waters. Its edges are set mainly by thermal maturity, measured as vitrinite reflectance (Ro): between 0.6 and 1.3 percent Ro, the rock is mature for oil across the broad paleoshelf and for wet gas and condensate on the paleoslope.
| Edge | Where and why |
|---|---|
| North | generally the 9,000-foot contour on the base of the shale, where Ro reaches 0.6 percent; shallower where measurements show maturity higher up — as in southeastern Mississippi, where heat flow is higher than in southern Louisiana and Alabama (Blackwell and others, 2011) |
| South | where Ro reaches about 1.3 percent: the 19,000-foot contour from near Pine Prairie, La., through central Louisiana; about 15,000 feet in western Louisiana, from burial-history models projected from Texas (Pitman and Rowan, 2012) |
| Southeast Louisiana | pulled back from the 19,000-foot line: in the Mississippi Bird's Foot delta (St. Bernard, Balize and Plaquemine lobes), a thick load of recent, cold sediment keeps the rock immature — confirmed in a well about 14 miles east of Hopedale, La., and one in Mississippi Canyon Block 84 (Wagner and others, 1994) |
| Northwest | near Clare, La., where the Upper Cretaceous thins onto the Sabine Uplift, on which Cenomanian sediments were never deposited |
| West | the Louisiana–Texas line, where the names change: the same strata are the Eagle Ford Group in Texas (Adams and Carr, 2010) |
| Offshore | the State–Federal water boundary |
Where measured data are thin, in western Louisiana, maturity models from east Texas and Louisiana guided the lines.
What is in the rock
| Area | Vitrinite reflectance | Fluid |
|---|---|---|
| Shallower paleoshelf | under 1.1% Ro | black and volatile oils, 35–48° API gravity |
| Deeper paleoslope | 1.1% to about 1.3% Ro | wet gas and condensate, over 45° API |
How the estimate was built
Table 1: key inputs. Drainage area, success ratio and estimated ultimate recovery (EUR) partly follow other U.S. shale-oil plays.
| Input | Minimum | Mode | Maximum | Mean |
|---|---|---|---|---|
| Potential production area (acres) | 1,500 | 1,500,000 | 20,411,000 | 7,304,167 |
| Average drainage area of wells (acres) | 75 | 150 | 185 | 136.7 |
| Untested area (%) | 90 | 94 | 99 | 94.3 |
| Success ratio (%) | 5 | 25 | 75 | 35.0 |
| Average EUR per well (million barrels of oil) | 0.04 | 0.08 | 0.2 | 0.086 |
The AU probability is 1.0.
Results
Table 2: undiscovered, technically recoverable resources, fully risked. F95 means a 95-percent chance of at least that amount; F5, a 5-percent chance.
| Resource | F95 | F50 | F5 | Mean |
|---|---|---|---|---|
| Oil (million barrels) | 181 | 1,151 | 4,215 | 1,537 |
| Gas (billion cubic feet) | 529 | 3,406 | 12,742 | 4,614 |
| Natural gas liquids (million barrels) | 15 | 99 | 393 | 138 |
Sources
Based on Assessment of Undiscovered Continuous Oil and Gas Resources in the Upper Cretaceous Tuscaloosa Marine Shale of the U.S. Gulf Coast, 2018, USGS Fact Sheet 2018–3043, by the Tuscaloosa Marine Shale Assessment Team: Paul C. Hackley, Catherine B. Enomoto, Brett J. Valentine, William A. Rouse, Celeste D. Lohr, Frank T. Dulong, Javin J. Hatcherian, Sean T. Brennan, William H. Craddock, Thomas M. Finn, Stephanie B. Gaswirth, Phuong A. Le, Heidi M. Leathers-Miller, Kristen R. Marra, Tracey J. Mercier, Stanley T. Paxton, Katherine J. Whidden, Cheryl A. Woodall and Christopher J. Schenk, U.S. Geological Survey; a work of the United States government in the public domain. The map and both tables are taken from the fact sheet's PDF, which the import had left out; results are also at the USGS Energy Resources Program.
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