East Texas Basin

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Introduction

The East Texas Basin is a petroleum-rich field located in five counties of East Texas. It is the second-largest oil field in the United States as it covers approximately 140,000 acres. Over 5 billion wells of oil have been produced since Columbus Marion Joiner discovered it in 1930.[1]

History

Since its discovery, there have been many conventional plays on the Woodbine Formation of the Cretaceous, which was deposited when East Texas was a shallow sea by the Sabine Uplift. The area then eroded and was covered unconformably by an impermeable Austin Chalk. This created a stratigraphic trap that allowed for hydrocarbons to be stored in the area. The primary drive mechanism for this basin is by water drive. [1][2]

Petroleum Elements [2]

Source Rocks

The source rocks of the East Texas Basin consist of Tertiary, Crestaceous, Jurassic rocks. The majority of crude oil is found in Cretaceous (Gulfian Series) rocks. Natural gas is predominantly in Crestaceous (Coahulian Series) rocks. Natural gas liquids are spread out roughly evenly throughout the different source rocks. The source rocks for the oil are the Eagle Ford and Haynesville/Bossier shale formations. Gas is predominantly found in the Haynesville/Bossier shale formation.

Reservoirs

Oil and natural gas liquids are found predominantly in the Woodbine formation, which is made out of sandstone. There is gas found in this formation as well, but there is also a significant amount found in the Haynesville/Bossier shale formation, which is made out of mudstone. There are a good number of limestone reservoirs present that hold gas and natural gas liquids, but there are few limestone reservoirs that hold oil. Dolomite, Chalk, and Anhydrite reservoirs are present but rare compared to the sandstone and limestone reservoirs.

Traps

Figure 1
Stratigraphic Traps

The most productive petroleum unit is the Woodbine Formation from the Cretaceous Period. A stratigraphic trap was formed by the overlying Austin Chalk. Facies changes and pinchouts are also common in the area. The majority of oil is found in these traps. Figure 1 is a cross-sectional map of the basin. The map shows how the Woodbine Formation is covered by Austin Chalk, and there is a pinchout on the right side.

Structural Traps

There are many salt domes, salt pillows, and anticlinal formations that store hydrocarbons. The Mexia-Talco Fault Zone created fault-dependent traps. In figure 1, the fault zone has shifted the formations to create these traps. Figure 1 also shows how there are anticlinal structures throughout the basin.

Combination Traps

There are also traps that are a combination of stratigraphic and structural traps. The majority of natural gas is trapped by combination traps. There are also a significant amount of combination traps that store oil.

Future Petroleum Potential

Figure 2

Throughout the last decade, producers have been increasingly focused on the gas-rich Haynesville Shale formation as it has been productive for horizontal hydraulic fracturing operations. Companies have been Some companies have re-fracked to re-stimulate petroleum production in old Haynesville wells. There are still drilled and uncompleted wells that still have potential to tap into the basin, as seen in figure 2, which is a map of permitted and completed wells in the area. [3] Dry gas production in Haynesville Shale is at record-high levels, producing over 13 Bcf/d. This makes it the highest ranking North American gas basin. [4] One limitation to this formation is that is is over-pressurized. This leads to high initial production rates followed by high first year decline rates. [5]

Further Readings

Geology and Geohydrology of the East Texas Basin

East Texas Oilfield Discovery

Haynesville/Bossier Shale

References

  1. 1.0 1.1 Smith, Julia Cauble. “TSHA | East Texas Oilfield.” Handbook of Texas Online, 2019, https://www.tshaonline.org/handbook/entries/east-texas-oilfield.
  2. 2.0 2.1 Foote, R. Q., et al. Petroleum Geology and the Distribution of Conventional Crude Oil, Natural Gas, and Natural Gas Liquids, East Texas Basin. Open-File Report, Department of the Interior, 1988.
  3. Drillinginfo. "The East Texas Basin: Activity Update.” Forbes, 9 May 2016, https://www.forbes.com/sites/drillinginfo/2016/05/09/the-east-texas-basin-activity-update/.
  4. Robinson, J. “Analysis: Hanyesville Gas Production Hits Record High Spurred by Strong Returns, Bullish Outlook.” SP Global, 2021, https://www.spglobal.com/platts/en/market-insights/latest-news/natural-gas/040621-haynesville-gas-production-hits-record-high-spurred-by-strong-returns-bullish-outlook.
  5. NGI, “Information about the Haynesville Shale.” Natural Gas Intel, 2021, https://www.naturalgasintel.com/information-about-the-haynesville-shale/.