Cherokee basin

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The Cherokee Basin is a hydrocarbon bearing formation with vast amounts of coal located in northeast Oklahoma and Southeast Kansas with depths ranging from surface level to about 4,000ft [1]. It is bounded to the North by the Bourbon Arch, to the East by the Ozark Uplift, to the South by the Ardmore and Arkoma basins, and to the West by the Nemaha Uplift.

Production History

The first well was drilled in the basin in 1873 in Allen County, Kansas. From the late 1800s to the early 1900s the region was heavily produced resulting in rapid depletion of viable prospects and reservoir mismanagement. The Cherokee Basin was overlooked for decades until the discovery of coal bed gas in the basin in the 1980s. Currently, there are 48,000 active wells in the basin. The majority of these wells are stripper wells resulting in just a few barrels of oil produced per day. Cumulative production for the basin is currently at 3.4 Gbbl of oil and 3.8 Tcf of gas.

OK oil and gas

Infrastructure

Most of the wells are very shallow and low producing, so a majority of the wells are pumped with very small pumpjacks and oil is typically transported by truck. There are also multiple gas pipelines throughout the area, so transportation of natural gas to sales lines is very simple and cheap.

Deposition

By the end of the late Devonian (380-400 mya), an erosional surface of Ordovician and Silurian age rocks were exposed at the surface. During this time the Chautauqua Arch formed in the basin[2]. By the early Mississippian (340-380 mya) the Chattanooga Shale deposited on top of this erosional surface[2]. The Chattanooga Shale is the equivalent of the Woodford Shale located in basins throughout Oklahoma. Next, the Osagian and Mississippian limestones were deposited along with the Chester Group[2]. By the late Mississippian (310-330 mya), uplift and erosion of the Mississippian sediments allowed for subaerial exposure of the surface[2]. By the late Desmoinesian (300-310 mya) the deposition of the Atokan sediments occured in a coastal environment[2]. This series is very important because it resulted in the deposition of large amounts of organic material and alternating sequences of limestone and shale known as cyclotherms[1]. During the late Permian, the Ouchita-Marathon Orogeny to the South resulted in compression in the basin. The compression caused various amounts of faulting and folding in the basin. The orogeny also allowed low temperature hydrothermal fluids to migrate North and assist in hydrocarbon heating and migration[3].

Kerogen

The kerogen in the basin is predominantly Type II-III. The majority of the source shales range from 1-3% TOC. The maximum burial depth of the basin is estimated to be around 6,700ft and is currently only around 4,000ft. This resulted in immature to slightly mature source rocks that were never exposed to higher Tmax values[4]. The introduction of low temperature hydrothermal fluids and high sulfur content in the shales are believed to have aided in maturation of the source rocks in the basin[3].

Plays

Pre-Woodford Paleozoic Play

The reservoirs in the Pre-Woodford Paleozoic Play consist of karsted dolomite, sandstones, limestones, and carbonates with net pay ranging from 25-75ft. The source rocks include the Simpson Group shales and the Woodford Shale from long distance migration. The traps are primarily structural with depths ranging from 1,200-6,300ft. 85 oil and 5 gas accumulations larger than 1MMBOE have been discovered in this play[1].

Mississippian Play

The reservoirs in the Mississippian Play are made of limestone and chert with an average net pay of 38ft. The source rocks include the Simpson Group shales and the Woodford Shale from long distance migration. Most traps are combination traps with depths from 800-5300ft. 24 oil accumulations larger than 1MMBOE have been discovered in this play[1].

Pennsylvanian Structural Play

The reservoirs are mainly Desmoinesian fluvial-deltaic sandstone with an average net pay of 73ft. The sources include the Woodford Shale and Pennsylvanian shales. Structural and combination traps are dominant in this play with depths ranging from 150-5000ft. 163 oil and 11 gas accumulations larger than 1MMBOE have been discovered in this play[1].

Pennsylvanian Stratigraphic Play

The reservoirs are mainly Desmoinesian fluvial-deltaic sandstone with an average net pay of 31ft. The sources include the Woodford Shale and Pennsylvanian shales. The traps are primarily stratigraphic with depths ranging from 400-4900ft. 90 oil and 5 gas accumulations larger than 1MMBOE have been discovered in this play[1].

Coal

Coal Bed Gas Play

The coal bed gas play is the only unconventional play in the basin. The target is 300-500ft thick Cherokee Group coals at depths ranging from 600-1,200ft[5]. The coals are mostly high-volatile A-B bituminous coals (medium rank). It is estimated that this play had an OGIP of 6.6 Tcf of natural gas[5].

Future Development

The conventional plays in the Cherokee Basin do not have a lot of potential for future development due to mass production and reservoir mismanagement. The coal bed gas play in the basin has been produced since the 1980s, and offers a unique opportunity for small companies. Production out of the coal beds has been on the decline since 2008 but with increasing natural gas prices could see more production.

  1. 1.0 1.1 1.2 1.3 1.4 1.5 Drake, R. M., & Hatch, J. R. (2021). Geologic assessment of Undiscovered Oil and gas resources in the Cherokee platform area of Kansas, Oklahoma, and Missouri. Scientific Investigations Report. https://doi.org/10.3133/sir20205110
  2. 2.0 2.1 2.2 2.3 2.4 Stratigraphy, depositional environments and coalbed methane resources ... (n.d.). Retrieved May 12, 2022, from https://magellan.kgs.ku.edu/PRS/publication/ofr2003-82/Chapter1.pdf
  3. 3.0 3.1 •Tedesco, S. (2016). Utilizing aeromagnetics and micromagnetics to define petroleum reservoirs in the Denver, Forest City and Cherokee basins. International Conference and Exhibition, Barcelona, Spain, 3-6 April 2016. https://doi.org/10.1190/ice2016-6492540.1
  4. The relationship between specific reservoir characteristics and the gas ... (n.d.). Retrieved May 12, 2022, from https://www.searchanddiscovery.com/documents/2015/10789tedesco/ndx_tedesco.pdf
  5. 5.0 5.1 Kansas coal, CBM, and Unconventionals Production Report. KGS OFR 2017-31--Kansas Coal, CBM, and Unconventionals Production Report. (n.d.). Retrieved May 11, 2022, from https://www.kgs.ku.edu/Publications/OFR/2017/OFR17_31/index.html