The Illinois Basin spans Illinois, Indiana, and western Kentucky — a mature, shallow oil province with thousands of long-lived stripper wells and the New Albany shale.
The Illinois Basin has approximately 248,815 wells operated by 18,328 companies. Below are the largest operators by well count. Data as of 2026-09-03.
| # | Operator | Wells | Have produced |
|---|---|---|---|
| 1 | The Ohio Oil | 10,782 | 0 |
| 2 | Marathon Oil Company | 4,529 | 0 |
| 3 | The Texas Company | 4,176 | 4 |
| 4 | Pure Oil Company | 3,303 | 9 |
| 5 | Texaco | 2,657 | 45 |
| 6 | Ohio Oil Company | 2,302 | 0 |
| 7 | The Pure Oil Company | 1,935 | 0 |
| 8 | The Carter Oil | 1,812 | 0 |
| 9 | Forest Oil | 1,684 | 0 |
| 10 | Carter Oil Company | 1,673 | 52 |
| 11 | Magnolia Petroleum Company | 1,672 | 3 |
| 12 | National Associated Petroleum Company | 1,620 | 0 |
| 13 | Shell Oil Company | 1,527 | 0 |
| 14 | Ashland Oil & Refining | 1,427 | 125 |
| 15 | Tide Water Associated Oil Company | 1,419 | 0 |
| 16 | Exxon Mobil | 1,308 | 3 |
| 17 | Hercules Petroleum | 1,305 | 156 |
| 18 | Superior Oil Company | 1,294 | 2 |
| 19 | Union Oil Company Of California | 1,218 | 0 |
| 20 | Brehm C E Drilling & Producing | 1,167 | 0 |
| 21 | Gulf Refining Company | 1,055 | 7 |
| 22 | Phillips Petroleum Company | 1,003 | 2 |
| 23 | Sun Production Co. Sun Oil | 987 | 0 |
| 24 | Il State Geological Survey | 928 | 0 |
| 25 | Associated Oil Production Company | 845 | 0 |
The largest operators in the Illinois Basin by well count in this snapshot are The Ohio Oil (10,782 wells), Marathon Oil Company (4,529 wells), The Texas Company (4,176 wells), Pure Oil Company (3,303 wells), Texaco (2,657 wells). The snapshot includes 18,328 operators and is dated 2026-09-03.
No. “Have produced” counts wells with a recorded first-production date. It does not confirm current production or current royalty payments. The “Wells” column counts well records associated with each operator in this basin snapshot.
Use the linked operator profiles and basin mineral-rights guide for related information. The inquiry link below provides a way to contact Buckhead about your interest.
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Well counts compiled by Buckhead Energy from state oil & gas regulator records (data as of 2026-09-03); reflect wells where each company is the current operator of record in the Illinois Basin. Informational only.
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