199,361 wells across 13,021 recorded operators, with 468 drilling permits filed in the 24-month window at summary refresh.
Buckhead Energy analysis of public oil and gas data. Formation summary date: 2026-11-01.
Quick answer: The Illinois Basin formation in Illinois has 199,361 wells on record across 13,021 recorded operators, with 468 drilling permits filed in the 24-month window at source refresh. Its operators with the most wells on record are The Ohio Oil, Marathon Oil Company, The Texas Company, Pure Oil Company and Texaco. Source: Buckhead Energy analysis of public oil and gas data. Formation summary date: 2026-11-01.
The operators with the most well counts targeting the Illinois Basin formation in Illinois:
| # | Operator | Wells in Illinois Basin |
|---|---|---|
| 1 | The Ohio Oil | 10,768 |
| 2 | Marathon Oil Company | 4,511 |
| 3 | The Texas Company | 4,094 |
| 4 | Pure Oil Company | 3,226 |
| 5 | Texaco | 2,426 |
| 6 | Ohio Oil Company | 2,180 |
| 7 | The Pure Oil Company | 1,931 |
| 8 | The Carter Oil | 1,811 |
| 9 | Forest Oil | 1,671 |
| 10 | Magnolia Petroleum Company | 1,602 |
The Illinois counties with the most Illinois Basin activity:
Crawford, White, Lawrence, Wayne, Peoria
Drilling permits in Illinois each year, the Illinois Basin count and share of them, and the median lateral length of those Illinois Basin permits.
| Year | State permits | This formation | Share | Median lateral |
|---|---|---|---|---|
| 2026 | 190 | 190 | 100% | n<5 |
| 2025 | 247 | 241 | 97.6% | n<5 |
| 2024 | 309 | 301 | 97.4% | n<5 |
| 2023 | 238 | 238 | 100% | n<5 |
| 2022 | 325 | 325 | 100% | n<5 |
| 2021 | 262 | 262 | 100% | n<5 |
| 2020 | 207 | 202 | 97.6% | n<5 |
| 2019 | 405 | 405 | 100% | n<5 |
Share of each year’s Illinois drilling permits by target formation, for the formations with the most permits.
| Year | Illinois Basin | Wisconsin Arch |
|---|---|---|
| 2026 | 100% | — |
| 2025 | 97.6% | 2.4% |
| 2024 | 97.4% | 2.6% |
| 2023 | 100% | — |
| 2022 | 100% | — |
| 2021 | 100% | — |
| 2020 | 97.6% | 2.4% |
| 2019 | 100% | — |
Buckhead Energy computes every figure on this page from grouped records in public oil and gas data. The page shows counts, sums, percentiles and indexes only; it does not list individual wells, leases or permits.
Counts under 3 wells and percentiles under 5 wells are withheld; totals are floors.
Share is the formation’s permits as a percent of the state’s permits that year. Median lateral length is published only when at least 5 permits stand behind it.
Last computed: 2026-11-01. These figures are informational only and are not a valuation of any mineral or royalty interest.
The Illinois Basin is a formation/play group recorded in Illinois, with 199,361 wells on file across 13,021 distinct operators of record. Operators have filed 468 drilling permits targeting the Illinois Basin in the 24-month window at summary refresh. These are stored records, not a live measure of drilling.
Recorded formation activity provides regional context. It does not establish ownership, future production, royalty payments or a value for an individual tract. Consult qualified professionals about your specific interest.
199,361 wells target the Illinois Basin in Illinois, worked by 13,021 recorded operators, per Buckhead Energy analysis of public oil and gas data. Formation summary date: 2026-11-01.
The Illinois Basin operators with the most wells on record in Illinois are The Ohio Oil, Marathon Oil Company, The Texas Company, Pure Oil Company and Texaco. The full ranking is in the table on this page. Formation summary date: 2026-11-01.
Operators filed 468 drilling permits targeting the Illinois Basin in the 24-month window at source refresh, per Buckhead Energy analysis of public oil and gas data. Formation summary date: 2026-11-01.
Operators filed 468 new drilling permits targeting the Illinois Basin in Illinois in the 24-month window at source refresh. New permits and spuds record reported activity stages; they do not establish ongoing drilling, per Buckhead Energy analysis of public oil and gas data. Formation summary date: 2026-11-01.
Illinois Basin activity in Illinois includes 199,361 wells on record and 13,021 recorded operators, with 468 drilling permits filed in the 24-month window at source refresh — from Buckhead Energy analysis of public oil and gas data. Formation summary date: 2026-11-01.
The primary counties recorded for Illinois Basin in Illinois are Crawford, White, Lawrence, Wayne, Peoria. Formation summary date: 2026-11-01.
Value depends on your net mineral acres or royalty decimal, the operator, the remaining drilling locations, and current oil and gas prices. This page is informational only, not a valuation. Formation summary date: 2026-11-01.
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Get Your Free Written OfferFormation: Illinois Basin
State: Illinois
Total wells: 199,361
Recorded operators: 13,021
Permits 24mo: 468
Summary date: 2026-11-01
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