Black Warrior Basin

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This page is currently being authored by a student at the University of Oklahoma. This page will be complete by Dec 13, 2020.


Introduction

The Black Warrior Basin is a small triangular sedimentary basin located in Northeast Mississippi and Northwest Alabama. The basin covers around 35,000 square miles, oriented northeast to southwest with a length of 220 miles and a width of 190 miles [1]. It is contained by the Appalachian compressional tectonic belt to the southeast, the Nashville Dome to the north, the Ouachita Mountain thrust belt to the south and extends into the Reelfoot Rift out west [2]. As time went on and the industry began to gain more knowledge of basins it was quickly realized that the Black Warrior Basin is not a separate structure but the eastern extension of the Arkoma Basin which is primarily in Arkansas and Oklahoma. This discovery lead to numerous attempts to connect the two basins by drilling holes but none have been successful so far. The Basin is the oldest coal-bed methane producer in the United States and primarily focuses on the Pottsville Formation for coal-bed methane production, while also producing oil and natural gas.

Map of the Black Warrior Basin including the counties that make up the land above.

History

The Basin got its name from the Black Warrior River which runs through Central Alabama where the basin is located. The Geology of the Black Warrior Basin dates back to the Pennsylvanian period where many non-marine areas near the equator became coal swamps. Over time the vegetation and animal remains from this area were squeezed together to create the coal-beds that populate the basin today. The basin mostly consists of carbonates with thin sandstone and shale layers and was formed by a downward development over a passive margin sometime during the early Paleozoic age. Production in the Black Warrior Basin did not begin until 1909 in Fayette County, Alabama where gas was found in Pennsylvanian Sandstone at a depth of 1400 feet [1]. In 1951 the Union Producing Company found small gas fields and oil accumulations around Monroe county which lead to the widespread exploration of the Basin throughout the 1950s and 1960s. Since the discovery, the basin has produced over 10.6 million barrels of oil and 1.15 trillion cubic feet of natural gas through 1991 making it one of the more dependable reservoirs in the United States throughout the 20th century. The Corinne field is the largest natural gas field in the basin while most of the oil comes from North Blowhorn Creek. The basin also contains over 5,537 Coal-bed methane wells . [3] which make it the largest basin for coal-bed gas in the United States. During the 1980s drillers began “fracking” from depths ranging from 300-2500 feet to get the natural gas from the coal-beds. This method proved useful as it allowed for the accumulation of more petroleum from the Black Warrior Basin. This gas production became a huge part of the basin’s success accounting for 75 percent of the 92.6 BCF produced in 1991. [4]

Geological Structure

The Black Warrior Basin is defined as a foreland basin located in between the Appalachian orogenic belt and the Ouachita Orogenic belt with the Nashville dome to the north. Sedimentary rocks from the Paleozoic, Mesozoic, and Cenozoic age make up the basin with thickness ranging from 7,000 feet to 31,000 feet with the thickest portion residing in eastern Mississippi. The Basin is covered by cretaceous strata from the Mississippi Embayment which was caused by uplift and down warping to the southwest which forced strata on top of the Paleozoic rocks. The framework of the basin is homoclinie that dips towards the Ouachita belt as you move to the southwest and contains overlapping folds and faults.[1]

Tectonic History

The tectonic history of the Black warrior basin begins with the deposition of coarse clastic sediments during the late Precambrian and early Cambrian era. Next, the Mississippian passive continental margin occurs, and shallow water carbonates are deposited. During the late Mississippian period, the continental collision caused marine sediments to be deposited and regressive-transgressive cycles to occur. During the Pennsylvanian era basin subsidence associated with the Appalachian-Ouachita orogeny and deposition of sediments developed barrier bars which were followed by the creation of thick clastic wedges from source areas and deposition of coal forming material. This was followed by uplift which resulted in erosion and non-deposition. Lastly the Mesozoic rifting caused the basin to become down warped to the southwest and covered in marine sediment from the Mississippi embayment.

Petroleum Elements

There are two major petroleum systems that make up the black warrior. One is the Pottsville Coal TPS which primarily consists of coal and produces natural gas, with the Chattanooga Shale/Floyd Shale–Paleozoic TPS producing oil. The Parkwood formation stretches the entire length of the basin and is one of the primary production points for petroleum in the basin.

Traps

Image of the anticline structural trap that is in the Upper Mississippian Sandstone Portion of the Black Warrior Basin.

The Black Warrior has a large number of faults scattered throughout the basin consisting of both stratigraphic and structural faults, with a large majority of the oil being trapped by basement-involved fault blocks. Looking at the Parkwood formation, which is made up of Upper Mississippian sandstone, we can see that it is trapped by a combination of stratigraphic and structural traps as well as basement fault blocks and combination traps. Over 75 percent of the oil and gas are trapped by combination and structural traps. The majority of the combination traps are characterized by facies change and anticlinal noses against a normal fault while the structural traps are influenced by anticlines controlled by basement fault blocks.[1]

Seals

Shale and argillaceous siltstone are the seals to the Parkwood formation. This specific shale is a good seal due to its low permeability of about 10 mb [5] while also containing organic matter that makes up the hydrocarbons. Other seals in different formations of the basin are micrite, dolamicrite, limestone, and different types of traps.

Source Rock

There are many different source rocks for the black warrior depending on the formation that is being explored. The Cambrian carbonate play has different types of shales as its source rocks, but the exact source rock is still unknown. The Parkwood formation on the other hand contains dark grey to black shale and type 2 and 3 kerogen which produce waxy oil or gas. However, as we move to the Pottsville formation the source rock changes to coal beds and dark-gray carbonaceous shale consisting of type 3 kerogens. This formation is known to produce dry gas due to the 0-50 feet thick coal beds acting as the source rock for the formation. Lastly looking at the Devonian chert and carbonate play, which produces the majority of the oil, we can see that limestone reservoirs are the source rocks and contain type 1 and 2 kerogens which are consistent with oil production.

Reservoir

The reservoir of the black warrior basins upper Mississippian play can grow to about 150 ft thick and continue for up to 5 miles along a depositional strike while stretching up to 15 miles beside depositional dips. The source is a controversial topic with some believing it came from a cratonic source northwest of the Ozark uplift with others believing it is southwest towards the Ouachita fold and thrust belt. The porosity values of the play range from 5-20 percent and indicate a decrease in reservoir quality as you move south. Tectonic fractures improve the quality of the reservoir and were created by limited strike-slip motion in between fault blocks.

Migration

The migration of resources in the basin begins in the southernmost part and moves north along fractures and carrier beds [6]. These resources are then deposited into anticlines and trap beds which expand northward into the rest of the basin. This process is true for all of the resources in the basin as the majority of the resources are in the southern part of the basin.

Geological Risks

Shows the step by step process of how hydraulic fracking extracts natural gas from the reservoirs.

One geological risk of the basin is the thin nature of some of the formations. With the hydraulic fracking that has been implemented in the basin, the stone needs to be able to hold a large number of sediments. The sandstone reservoir in the Mississippian plate is thin and of lower quality so can break if too much is packed in. This would no doubt cause the reservoir to be less efficient and limit the amount of petroleum that can be extracted from the well. This would cause a major loss on the project and hurt the future production of petroleum in the basin. Another major environmental concern is the contamination of the water reservoirs nearby. The constant fracking could cause the reservoir to become unusable and the regulations to become tighter which would no doubt hurt the future production of the reservoir. This could also cause sickness for the people drinking and using the water which could result in death.

Future Potential

The Black Warrior basin has been one of the most reliable oil and gas reservoirs over the past 50 years, however; production is declining as more petroleum is extracted from the basin. The Basin hit its peak production in the 1950s and then slowly declined until the implementation of fracking allowed for the extraction of more resources. Marshall Petroleum is a driller in the basin and estimates up to 90,000 barrels of oil and 2MMCF gas recoverable [4]. This basin is a proven, low-cost, and low-risk project that produces proven returns through fracking. The basin may not be increasing in oil and gas production but is still a major producer in the united states and will be for years to come due to the use of water flooding chemical injection and other innovative methods used to avoid abandoning the wells [7].

Petroleum Engineering

With Reservoirs ranging from 2100 feet to 5000 feet [1], the black warrior basin is a great basin for easy drilling. Due to the decline in production engineers have had to turn to new methods to get the oil. This can be strategic good placement, infill drilling, horizontal drilling, and other tactics to get the most out of the reservoir. In the Pottsville Formation they have implemented hydraulic fracking at depths ranging from 300-2500 feet [3] in order to continue production. Marshall Petroleum believes that this new technology will allow for the basin to remain productive over the years and remain the low-cost high reward operation that it has been in the past.

References

  1. 1.0 1.1 1.2 1.3 1.4 Hatch, Joseph, and Mark Pawlewicz. Geologic Assessment of Undiscovered Oil and Gas Resources of the Black Warrior Basin Province, Alabama and Mississippi. Data Series, 69, 2007.(Crossref), https://pubs.usgs.gov/dds/dds-069/dds-069-i/
  2. Vision Exploration, L.L.C. - Black Warrior Basin Geology. https://www.visionexploration.com/bwb.htm. Accessed 12 Dec. 2020.
  3. 3.0 3.1 Black Warrior Riverkeeper - Coalbed Methane & Fracking. https://blackwarriorriver.org/coalbed-methane-fracking/. Accessed 12 Dec. 2020.
  4. 4.0 4.1 Marshal Petroleum - Areas of Operation - Black Warrior Basin and Gulf Coast Region of Alabama & Mississippi. https://marshalpetroleum.com/areas-of-operation. Accessed 12 Dec. 2020.
  5. Bearden, L., et al. North Blowhorn Creek Oil Field - a Stratigraphic Trap in Black Warrior Basin of Alabama. Conference, CONF-8405216-, 1 Apr. 1984, https://www.osti.gov/biblio/6648186-north-blowhorn-creek-oil-field-stratigraphic-trap-black-warrior-basin-alabama.
  6. Ryder, R. T. BLACK WARRIOR BASIN PROVINCE (065) . https://certmapper.cr.usgs.gov/data/noga95/prov65/text/prov65.pdf.
  7. Kugler, R. L., et al. “Reservoir Heterogeneity in Carboniferous Sandstone of the Black Warrior Basin. Final Report.” Other Information: PBD: Jun 1994, 1 June 1994, doi:10.2172/10159645.