Assessment of Continuous Oil and Gas Resources in the Upper Jurassic Smackover Formation of the Onshore U.S. Gulf Coast, 2022

Fact Sheet 2023-3021
National and Global Petroleum Assessment
By: , and 

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Abstract

Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean continuous resources of 0.8 billion barrels of oil and 16 trillion cubic feet of gas in the Upper Jurassic Smackover Formation of the onshore U.S. Gulf Coast region.

Introduction

The U.S. Geological Survey (USGS) assessed undiscovered, technically recoverable, continuous (unconventional) oil and gas resources in the Smackover Formation, which extends across the Gulf Coast region from the United States-Mexican border in Texas eastward to the Florida panhandle. Mudstones of the Smackover Formation are interpreted as a major petroleum source rock for the Upper Jurassic–Cretaceous–Tertiary Composite Total Petroleum System defined by the USGS in the Gulf Coast region (Warwick and others, 2007; Dubiel and others, 2010) (fig. 1).

Smackover Formation covers Gulf coast states and Arkansas.
Figure 1.

Map showing seven continuous assessment units (AUs) in the Smackover Formation within the Upper Jurassic–Cretaceous–Tertiary Total Petroleum System of the onshore Gulf Coast region.

The Smackover Formation is interpreted to have been deposited within a carbonate ramp setting, in which the ramp was a low-angle inclined carbonate surface extending from the Oxfordian shoreline to the deep basin (Mancini and others, 2019). In general, deposits of the outer ramp are mainly subtidal mudstones. Laminated mudstones within the condensed stratigraphic section of the outer ramp are commonly organic rich (Mancini and others, 2019), yet exploration of these mudstones as a self-sourced, continuous (unconventional) shale-oil or shale-gas reservoir has been limited (Yang and others, 2015). The inner-ramp facies range from similar subtidal mudstones to high-energy intertidal to supratidal carbonate facies. Most conventional oil and gas fields in the Smackover Formation are in carbonate facies of the inner-ramp environment.

The USGS defined seven continuous assessment units (AUs), five gas and two oil, within the Smackover Formation (fig. 1). Criteria used to define these AUs include the following: (1) spatial and temporal lithologic variability within the inner- and outer-ramp deposits, which affected thickness of the potential source interval; (2) presence of peripheral faults or salt basins, which may have affected petroleum migration compared to retention; (3) thermal maturity, which determined areas of oil compared to gas generation; (4) the distribution of Smackover Formation sandstones sourced from the ancestral Mississippi River (Shew and Garner, 1990), which may have provided the potential for conventional sandstone reservoirs or enhanced migration pathways through the sandstones, as well as affecting source-rock quality by dilution; and (5) maximum depth to the top of the Smackover Formation, which was 46,000 feet for this assessment. Potential gas resources at this depth are not technically recoverable using drilling and completion technologies because of high pressure and temperature conditions. Maximum temperature and pressure values used in this assessment were determined from current drilling and well-completion technologies (Wang and others, 2013; Chaplin and others, 2014; Song and Yang, 2016; Cameron, 2017), which limit the downdip extent of USGS conventional and continuous AU boundaries. This depth cutoff honors the requirement that the USGS assess only technically recoverable oil and gas resources as defined at the time of the assessment.

Total Petroleum System and Assessment Units

The USGS defined seven continuous assessment units within the Smackover Formation (table 1). In addition to the criteria described in the “Introduction” section of this report, the five continuous gas AUs were partly defined by the modeled greater than 1.3 percent equivalent vitrinite reflectance (Roe) thermal maturity contour and either the modeled 230 degrees Celsius temperature contour for technically recoverable resources or the 25,000 pound per square inch cutoff for technically recoverable resources (whichever is furthest inboard from the current coastline). More specifically, the Smackover Outer Ramp Continuous Gas AU was also defined by the extent of the outer-ramp depositional environment (Snedden and Galloway, 2019) and the areas outside of salt basins (Salvador, 1991). The Smackover Outer Ramp Salt Basins Continuous Gas AU was also defined by the extent of the outer-ramp depositional environment (Snedden and Galloway, 2019) and the extent of salt basins (Salvador, 1991). The Smackover Inner Ramp Continuous Gas AU was constrained by the extent of the inner-ramp depositional environment (Snedden and Galloway, 2019) and ramp areas outside of salt basins (Salvador, 1991). The Smackover Inner Ramp Salt Basins and Peripheral Fault Zone Continuous Gas AU was defined by the United States-Mexican border, the extent of the inner-ramp depositional environment (Snedden and Galloway, 2019), and the locations of salt basins (Salvador, 1991). The Smackover Inner Ramp Interbedded Sandstone Continuous Gas AU was constrained by the extent of the inner-ramp depositional environment (Snedden and Galloway, 2019) and the area of sandstone deposition in parts of northern Louisiana, central Mississippi, southern Alabama, and the westernmost part of the Florida panhandle.

Table 1.    

Key input data for seven continuous oil and gas assessment units in the Smackover Formation.

[The average estimated ultimate recovery (EUR) input is the minimum, median, maximum, and calculated mean. Gray shading indicates not applicable. AU, assessment unit; %, percent; MMBO, million barrels of oil; BCFG, billion cubic feet of gas]

Assessment input data–Continuous AUs Smackover Inner Ramp Salt Basins and Peripheral Fault
Zone Continuous Oil
Smackover Inner Ramp Salt Basins and Peripheral Fault
Zone Continuous Gas
  Minimum Mode Maximum Calculated mean   Minimum       Mode    Maximum Calculated mean
Potential production area of AU (acres) 1,000 5,887,500 11,775,000 5,887,833 1,000 8,297,000 16,594,000 8,297,333
Average drainage area of wells (acres) 80       140      180      133.3   80      120 160        120
Success ratio (%)   10        50       90        50   10        50 90         50
Untested area (%)   100      100 100      100   100        100 100        100
Average EUR (MMBO, oil; BCFG, gas) 0.01 0.03         0.08 0.032     0.05 0.2 2          0.298
AU probability 1.0 1.0
Assessment input data–Continuous AUs Smackover Outer Ramp Salt Basins Continuous Gas Smackover Inner Ramp Continuous Gas
  Minimum Mode Maximum Calculated mean   Minimum       Mode    Maximum Calculated mean
Potential production area of AU (acres) 1,000 1,487,000 2,974,000 1,487,333 1,000 6,722,500 13,445,000 6,722,833
Average drainage area of wells (acres) 80 120 160       120 80 120 160 120
Success ratio (%) 10 40 70       40 10 40 70 40
Untested area (%) 100 100 100      100 100 100 100 100
Average EUR (MMBO, oil; BCFG, gas) 0.05 0.1 1 0.146 0.05 0.1 1 0.146
AU probability 1.0 1.0
Assessment input data–Continuous AUs Smackover Outer Ramp Continuous Gas Smackover Inner Ramp Interbedded Sandstone Continuous Oil
Minimum Mode Maximum Calculated mean   Minimum       Mode     Maximum Calculated mean
Potential production area of AU (acres) 1,000 2,374,000 4,748,000 2,374,333 1,000 2,273,000 4,546,000 2,273,333
Average drainage area of wells (acres) 80 120 160 120 80 140 180 133.3
Success ratio (%) 10 40 70 40 5 30 55 30
Untested area (%) 100 100 100 100 100 100 100 100.0
Average EUR (MMBO, oil; BCFG, gas) 0.05 0.1 1 0.146 0.005 0.015 0.04 0.016
AU probability 1.0 1.0
Assessment input data–Continuous AUs Smackover Inner Ramp Interbedded Sandstone Continuous Gas
Minimum Mode Maximum Calculated mean
Potential production area of AU (acres) 1,000 702,000 1,404,000 702,333
Average drainage area of wells (acres) 80 120 160 120
Success ratio (%) 5 30 55 30
Untested area (%) 100 100 100 100
Average EUR (MMBO, oil; BCFG, gas) 0.025 0.05 0.5 0.073
AU probability 1.0
Table 1.    Key input data for seven continuous oil and gas assessment units in the Smackover Formation.

The two continuous oil AUs were partly defined by the area between the 0.6 and 1.3 percent Roe thermal maturity boundaries for oil and gas, respectively. In addition, the Smackover Inner Ramp Salt Basins and Peripheral Fault Zone Continuous Oil AU was defined by the United States-Mexican border, the extent of the inner-ramp depositional environment (Snedden and Galloway, 2019), and the locations of salt basins and the peripheral fault zone (Salvador, 1991). The Smackover Inner Ramp Interbedded Sandstone Continuous Oil AU was constrained by the extent of the inner-ramp depositional environment (Snedden and Galloway, 2019) and the area of sandstone deposition within the Smackover Formation in parts of northern Louisiana, central Mississippi, southern Alabama, and the westernmost part of the Florida panhandle.

Assessment input data are summarized in table 1 and in Schenk and Whidden (2023). Across the U.S. Gulf Coast, 41 wells have targeted the lower part of the Smackover Formation (S&P Global Commodity Insights, 2023), and of these, only 3 wells have sufficient production data to calculate estimated ultimate recoveries (EURs). For this reason, input data from USGS continuous oil and gas resource assessments of Upper Jurassic strata in northeast Mexico (Schenk and others, 2014) were used as guides for potential EUR distributions in the Smackover Formation.

Undiscovered Resources Summary

The USGS quantitatively assessed oil and gas resources in seven continuous AUs in the Smackover Formation (table 2). For undiscovered, technically recoverable continuous oil and gas resources, the mean totals are 799 million barrels of oil (MMBO), or 0.8 billion barrels of oil, with an F95 to F5 fractile range from 177 to 1,789 MMBO; 15,958 billion cubic feet of gas (BCFG), or 16 trillion cubic feet of gas, with an F95 to F5 fractile range from 2,456 to 47,809 BCFG; and 1,122 million barrels of natural gas liquids (MMBNGL), or 1.1 billion barrels, with an F95 to F5 fractile range from 172 to 3,360 MMBNGL.

Table 2.    

Results for seven continuous assessment units in the Smackover Formation.

[Results shown are fully risked estimates. F95 represents a 95-percent chance of at least the amount tabulated; other fractiles are defined similarly. Gray shading indicates not applicable. MMBO, million barrels of oil; BCFG, billion cubic feet of gas; NGL, natural gas liquids; MMBNGL, million barrels of natural gas liquids]

Assessment units (AUs) AU prob-ability Accum-ulation type Total undiscovered resources
Oil (MMBO) Gas (BCFG) NGL (MMBNGL)
F95 F50 F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean
Upper Jurassic–Cretaceous–Tertiary Composite Total Petroleum System
Smackover Inner Ramp Salt Basins and Peripheral Fault Zone Continuous Oil AU 1.0 Oil 159 621 1,602 716 191 745 1,931 859 14 56 145 64
Smackover Inner Ramp Salt Basins and Peripheral Fault Zone Continuous Gas AU 1.0 Gas 1,355 6,315 30,726 9,867 94 442 2,158 691
Smackover Outer Ramp Salt Basins Continuous Gas AU 1.0 Gas 122 489 2,025 703 9 34 141 49
Smackover Inner Ramp Continuous Gas AU 1.0 Gas 551 2,215 9,314 3,182 38 155 649 223
Smackover Outer Ramp Continuous Gas AU 1.0 Gas 196 785 3,221 1,122 14 55 225 79
Smackover Inner Ramp Interbedded Sandstone Continuous Oil AU 1.0 Oil 18 72 187 83 21 86 225 100 2 6 16 7
Smackover Inner Ramp Interbedded Sandstone Continuous Gas AU 1.0 Gas 20 87 367 125 1 6 26 9
Total Smackover undiscovered continuous resources 177 693 1,789 799 2,456 10,722 47,809 15,958 172 754 3,360 1,122
Table 2.    Results for seven continuous assessment units in the Smackover Formation.

Acknowledgment

We thank John W. Snedden (University of Texas at Austin) for providing the mapped extent of sandstones from the ancestral Mississippi River used in the definition of continuous assessment units in the Upper Jurassic Smackover Formation.

References Cited

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Suggested Citation

Whidden, K.J., Birdwell, J.E., Gardner, R.D. Kinney, S.A., Paxton, S.T., Pitman, J.K., and Schenk, C.J., 2023, Assessment of continuous oil and gas resources in the Upper Jurassic Smackover Formation of the onshore U.S. Gulf Coast, 2022: U.S. Geological Survey Fact Sheet, 2023–3021, 4 p., https://doi.org/10.3133/fs20233021.

ISSN: 2327-6932 (online)

Study Area

Publication type Report
Publication Subtype USGS Numbered Series
Title Assessment of continuous oil and gas resources in the Upper Jurassic Smackover Formation of the onshore U.S. Gulf Coast, 2022
Series title Fact Sheet
Series number 2023-3021
DOI 10.3133/fs20233021
Year Published 2023
Language English
Publisher U.S. Geological Survey
Publisher location Reston VA
Contributing office(s) Central Energy Resources Science Center
Description Report: 4 p.; Data Release
Country United States
State Alabama, Arkansas, Florida, Louisiana, Mississippi, Texas
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
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