Illinois basin

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The Illinois Basin is a structural basin located under most of Illinois and spans to Kentucky and Indiana. Consisting predominantly of structures from the Paleozoic era, this basin spans approximately 53,000 square miles and ranges in depth from 900 to 7000 meters.[1] The Basin mainly includes reservoirs of the Chesterian, Valmeyeran, Pennsylvanian, Silurian, and Devonian Epochs. Since its discovery in the mid 1800’s, the Illinois Basin has produced approximately 4.2 billion barrels of oil. 99% of all petroleum found in this basin was derived from the New Albany Shale formation.[2]

History

Oil and gas production of the basin began in 1853 when drillers in Illinois first extracted drift gas from the wells. Since there was limited technology and information at the time, wildcatters did not know how to search for or drill for oil. In 1860 many attempts were made to reach oil, but the drilling facilities were not good enough for effective extraction. By the early 1880’s, significant reserves of natural gas had been discovered in the basin and were piped to local areas for domestic use. For roughly 50 years following the initial discovery of the oil and gas reserves, small scale efforts were taken to extract oil. The peak production under these methods peaked in 1902 at 6,500 barrels per well. Improvements in technology during the 1900’s led to new methods of extraction and high levels of production in the basin.[3]

Petroleum Elements

Source Rocks

Figure 1. Generalized column of the Illinois Basin showing sequences with their cumulative production.[4]

The primary source rock of the Illinois Basin is various types of Shale rich with organic marine matter. The highest producing of the shales is the New Albany shale. Underlying the southern part of the Illinois Basin, the New Albany Shale has a pressure-temperature point called the hydrocarbon kitchen. At this point the organic matter in the source rock is converted into hydrocarbons. [5]

Reservoir

The reservoir of the Illinois Basin consists of a wide variety of rock composition. Five major geological ages represent the diverse makeup of reservoirs throughout the basin. The makeup of the Chestrian, Valmeyeran, Pennsylvanian, Silurian and Devonian age reservoirs all consist of a limestone or sandstone that is high in Permeability and Porosity. These rocks allow the hydrocarbons to migrate and be stored within the reservoirs. Of the five major reservoir ages, the Chesterian reservoirs produce an estimated 60% of all oil extracted from the basin. The Valmeyeran reservoirs account for 20%, the Pennslyvanian for 13% and the Silurian and Devonian each for 5%.[2]

Figure 2. Fault systems of the Illinois Basin.[6]

Traps, Seals and Migration

Trapping occurs when a structural or stratigraphic feature prevents the vertical migration of hydrocarbons and accumulates them. Excessive Folds and Faults provide the major structural traps found in this basin. Multiple layers of impermeable shale found throughout the basin also provide a sealing mechanism to prevent the passing of hydrocarbons. Approximately 66% of the produced oil is found in the New Albany Shale, suggesting that vertical migration is the primary direction of hydrocarbons. This also suggests that lateral flow plays a secondary role in migration.

Migration is also dictated by faults and belts that surround the major generative areas. Illustrated in figure 2, the basin consist of numerous faults, fractures, anticlines, synclines, and other structures that affect migration. The Rough Creek-Shawneetown fault system is an east-west running fault system that lies along the south of the Illinois Basin and is a probable barrier to migration from the eastern side of the basin. The Cottage Grove fault system is another southern fault in the Illinois Basin that prevents migration to the west. The La Salle anticlinal belt is a major system that runs north-south along the eastern side of Illinois and prevents migration to the east. Just south of the La Salle anticlinal belt is the Wabash valley fault system. This fault system acts as a migration corridor that vertically migrates hydrocarbons from adjacent reservoir rocks. [2]

Petroleum and Facility Engineering

Since early on in the production timeline of the Illinois Basin, technology has played an important role in the extraction of oil. As shown in Figure 3, improvements in technologies and methods led a major role in the "Booms" seen throughout the history of the oil production in the basin.

Anticlines and Well Casing

Figure 3. Annual oil production of the Illinois Basin[7]

The first major problem that wildcatters came across when extracting oil was the flooding of wells with water. Improper well casing led to water from upper-layer drilling would leak down into the wells and prevent oil from coming out of the rocks. At the beginning of the 1900’s, improvements in well casing technology allowed oil to be drilled without water flowing into the wells. In 1904 geologists began to discover shallow anticlinal reservoirs of oil and gas throughout the basin. By locating and drilling these new sites with proper technology and information, production skyrocketed. By 1910, the yearly oil production of the basin was 33 million barrels.[3]

Seismic Exploration

By the end of the 1930’s geologist implemented a new technology called Seismic Exploration. This method, also called Reflection seismology, was achieved by sending seismic blast down into the basin and having microphones on the surface to record the reflection and refraction of the blast waves as they bounce off the formations below. This led to the discovery of anticlines that were either hidden or too deep to be found. With the new discovery of countless anticlines and other traps, oil production in the basin hit another boom. Production levels hit their highest in state history by 1940 at 148 million barrels per year.[3]

Hydraulic Fracturing and Waterflooding

Another groundbreaking method in oil production is called Hydraulic fracturing. First developed in the 1950’s, hydraulic fracturing, or fracking, involves the blasting of fluid into reservoir rocks with enough force to fracture them. The fractures are then filled with sand to keep the holes from closing and allow the oil to flow out.

Another similar technique developed in this time is called Waterflooding. Waterflooding is also referred to as Secondary Recovery and involves drilling water injection wells around the oil well and injecting the reservoir rock with water. The injection of water pushes the oil into the well at high pressure and allows for extraction of more petroleum. Both of these techniques led to a third boom in the Illinois Basin. In 1956, the basin produced 82 million barrels, a peak that has never been met again.[3]

Geologic Risks and Uncertainties

Petroleum loss of potential well sites plays a major role in the uncertainty of drilling in the Illinois Basin. Petroleum loss can occur along leaky carrier beds, faults, or factures. More than 90% of hydrocarbons found in this basin travel over 350 meters before reaching reservoirs where they are extracted at. In addition to this migration distance, the vast number of fractures and faults in the basin lead to leakage and loss of potential hydrocarbon reserves. If oil leaks all the way up to the surface, it transforms into a form of tar called Oil sands. The weathering of oil-sands on the surface can result in a loss over 90% of its original hydrocarbons. The leftover oil-sands on the surface remain behind as an indication of a petroleum leak. The only notable oil-sand deposit in the Illinois Basin overlies Western Kentucky.[8] This deposit comprises a total 3.4 billion barrels of oil-sand, which equates to 30.4 billion barrels of petroleum at subsurface depths less than 200 meters.

Another risk faced by wildcatters is the high possibility of drilling a dry well or a well that underproduces. As of 1996, Nearly 90,000 wells have been drilled in the Illinois Basin, and only 42% are still producing oil or gas.[2] 96% of wells in the Illinois Basin produce less than 10 barrels daily. Based on the historical uncertainty of actually hitting a well, and the low probability of actually making a profit on it, wildcatters are not willing to risk a new well.[9]

Future Potential of Petroleum

While it has seem that production of the Illinois Basin is declining towards stagnation, there is still potential for its future. It is estimated that the total potential amount of recoverable oil remaining in the Illinois Basin is 4.1 billion barrels. With low potential costs for small-scale operations, the Illinois Basin is primed to boom again. Improvements in technology and methodology such as Refracking have opened up the possibility greater production output with reduced environmental impact.

References

Akar, C. (2014). MATURITY AND HYDROCARBON POTENTIAL OF THE NEW ALBANY SHALE AND MAQUOKETA SHALE IN THE ILLINOIS BASIN. Retrieved November 16, 2020, from https://search.proquest.com/docview/1651235218[1]

General Geology of the Illinois Basin. (n.d.). Retrieved November 17, 2020, from https://www.sharpeoilandgas.com/ILBstats.html[5]

Higley, D. (2013). THE NEW ALBANY SHALE PETROLEUM SYSTEM, ILLINOIS BASIN. Retrieved November 17, 2020, from https://pubs.usgs.gov/of/2003/ofr-03-037/htmltext/introduc.htm[2]

History of Oil and Gas Production in Illinois. (n.d.). Retrieved November 17, 2020, from https://isgs.illinois.edu/outreach/geology-resources/history-oil-and-gas-production-illinois[3]

Howard, R. (1990). Hydrocarbon Reservior Distrubuiton in the Illinois Basin. In Interior Cratonic Basins (pp. 299-327).[10]

Huels, M. (2018). NEW OPPORTUNITIES IN THE MATURE FIELDS OF THE CENTRAL ILLINOIS BASIN (Unpublished master's thesis). Colorado School of Mines.[9]

Lewman, M., Comer, J., & Hamilton-Smith, T. (1995). Feasibility Study of Material-Balance Assessment of Petroleum from the New Albany Shale in the Illinois Basin. Retrieved November 16, 2020, from https://pubs.usgs.gov/bul/2137/report.pdf[8]

Mast, R., & Howard, R. (n.d.). Recovery Estimates in the Illinois Basin. In Interior Cratonic Basins (pp. 295-298). doi:https://doi.org/10.1306/M51530[11]

Swezey, C. (2009). Regional Stratigraphy and Petroleum Systems of the Illinois Basin. Retrieved November 16, 2020, from https://pubs.usgs.gov/sim/3068/illinoisbasin.pdf[12]

[Illinois Basin Cross Section]. (n.d.). Retrieved November 16, 2020, from https://isgs.illinois.edu/sites/default/files/images/rocks-min/fig-3.jpg[13]

External links

  1. 1.0 1.1 Akar, C. (2014). MATURITY AND HYDROCARBON POTENTIAL OF THE NEW ALBANY SHALE AND MAQUOKETA SHALE IN THE ILLINOIS BASIN. Retrieved November 16, 2020, from https://search.proquest.com/docview/1651235218
  2. 2.0 2.1 2.2 2.3 2.4 Higley, D. (2013). THE NEW ALBANY SHALE PETROLEUM SYSTEM, ILLINOIS BASIN. Retrieved November 17, 2020, from https://pubs.usgs.gov/of/2003/ofr-03-037/htmltext/introduc.htm
  3. 3.0 3.1 3.2 3.3 3.4 History of Oil and Gas Production in Illinois. (n.d.). Retrieved November 17, 2020, from https://isgs.illinois.edu/outreach/geology-resources/history-oil-and-gas-production-illinois
  4. Howard, R. (1990). Hydrocarbon Reservior Distrubuiton in the Illinois Basin. In Interior Cratonic Basins (pp. 299-327).
  5. 5.0 5.1 General Geology of the Illinois Basin. (n.d.). Retrieved November 17, 2020, from https://www.sharpeoilandgas.com/ILBstats.html
  6. Mast, R., & Howard, R. (n.d.). Recovery Estimates in the Illinois Basin. In Interior Cratonic Basins (pp. 295-298). doi:https://doi.org/10.1306/M51530
  7. Mast, R., & Howard, R. (n.d.). Recovery Estimates in the Illinois Basin. In Interior Cratonic Basins (pp. 295-298). doi:https://doi.org/10.1306/M51530
  8. 8.0 8.1 Lewman, M., Comer, J., & Hamilton-Smith, T. (1995). Feasibility Study of Material-Balance Assessment of Petroleum from the New Albany Shale in the Illinois Basin. Retrieved November 16, 2020, from https://pubs.usgs.gov/bul/2137/report.pdf
  9. 9.0 9.1 Huels, M. (2018). NEW OPPORTUNITIES IN THE MATURE FIELDS OF THE CENTRAL ILLINOIS BASIN (Unpublished master's thesis). Colorado School of Mines.
  10. Howard, R. (1990). Hydrocarbon Reservior Distrubuiton in the Illinois Basin. In Interior Cratonic Basins (pp. 299-327).
  11. Mast, R., & Howard, R. (n.d.). Recovery Estimates in the Illinois Basin. In Interior Cratonic Basins (pp. 295-298). doi:https://doi.org/10.1306/M51530
  12. Swezey, C. (2009). Regional Stratigraphy and Petroleum Systems of the Illinois Basin. Retrieved November 16, 2020, from https://pubs.usgs.gov/sim/3068/illinoisbasin.pdf
  13. [Illinois Basin Cross Section]. (n.d.). Retrieved November 16, 2020, from https://isgs.illinois.edu/sites/default/files/images/rocks-min/fig-3.jpg