The largest oil and gas operators active in Illinois — ranked by total well count, with producing-well counts for each. Click any operator to see their full profile.
Buckhead Energy analysis of public oil and gas data. Refreshed daily. Data current as of 2026-11-01.
Researching an operator or well activity is one part of understanding a mineral or royalty interest.
Quick answer: By wells operated, The Ohio Oil is the largest oil and gas operator in Illinois with 10,782 wells on record, followed by Marathon Oil Company (4,529) and The Texas Company (4,094). Ranked from Buckhead Energy analysis of public oil and gas data (as of 2026-11-01). This is an operated-well-count ranking, not a revenue or market-cap ranking.
As of 2026-11-01, the largest operator by wells on record in Illinois is The Ohio Oil with 10,782 wells on record, across the top 100 ranked operators, per Buckhead Energy analysis of public oil and gas data.
| # | Operator | Wells | Producing | Top Formation | Top County |
|---|---|---|---|---|---|
| 1 | The Ohio Oil | 10,782 | 0 | Illinois Basin | Crawford |
| 2 | Marathon Oil Company | 4,529 | 0 | Illinois Basin | Lawrence |
| 3 | The Texas Company | 4,094 | 0 | Illinois Basin | Marion |
| 4 | Pure Oil Company | 3,231 | 0 | Illinois Basin | Richland |
| 5 | Texaco | 2,427 | 0 | Illinois Basin | Marion |
| 6 | Ohio Oil Company | 2,181 | 0 | Illinois Basin | Crawford |
| 7 | The Pure Oil Company | 1,935 | 0 | Illinois Basin | Wayne |
| 8 | The Carter Oil | 1,812 | 0 | Illinois Basin | Fayette |
| 9 | Forest Oil | 1,678 | 0 | Illinois Basin | Cumberland |
| 10 | Magnolia Petroleum Company | 1,605 | 0 | Illinois Basin | Marion |
| 11 | Il State Geological Survey | 1,557 | 0 | Illinois Basin | Will |
| 12 | National Associated Petroleum Company | 1,556 | 0 | Illinois Basin | White |
| 13 | Shell Oil Company | 1,483 | 0 | Illinois Basin | Hamilton |
| 14 | Tide Water Associated Oil Company | 1,419 | 0 | Illinois Basin | Crawford |
| 15 | Exxon Mobil | 1,299 | 0 | Illinois Basin | Fayette |
| 16 | Superior Oil Company | 1,278 | 0 | Illinois Basin | White |
| 17 | Union Oil Company Of California | 1,223 | 0 | Illinois Basin | Clay |
| 18 | Carter Oil Company | 1,206 | 0 | Illinois Basin | Fayette |
| 19 | Brehm C E Drilling & Producing | 1,167 | 0 | Illinois Basin | White |
| 20 | Northern Illinois Gas Company | 1,116 | 0 | Illinois Basin | Livingston |
| 21 | Gulf Refining Company | 1,010 | 0 | Illinois Basin | Clinton |
| 22 | Sun Production CO Sun Oil | 987 | 0 | Illinois Basin | White |
| 23 | Phillips Petroleum Company | 964 | 0 | Illinois Basin | White |
| 24 | Associated Oil Production Company | 845 | 0 | Illinois Basin | Crawford |
| 25 | Campbell Energy | 810 | 0 | Illinois Basin | White |
| 26 | Mahutska Oil Company | 780 | 0 | Illinois Basin | Crawford |
| 27 | The Texas | 774 | 0 | Illinois Basin | Marion |
| 28 | Petco Petroleum | 764 | 0 | Illinois Basin | Fayette |
| 29 | Natural Gas Pipeline CO Of America | 738 | 0 | Wisconsin Arch | Kankakee |
| 30 | Mcbride W C | 719 | 0 | Illinois Basin | Lawrence |
| 31 | Zanetisjohn Mestate Of | 706 | 0 | Illinois Basin | Jasper |
| 32 | Citation Oil & Gas | 686 | 0 | Illinois Basin | Marion |
| 33 | Alco Oil & Gas | 686 | 0 | Illinois Basin | Henderson |
| 34 | Calvert Drilling | 675 | 0 | Illinois Basin | Richland |
| 35 | Ashland Oil & Refining | 672 | 0 | Illinois Basin | Crawford |
| 36 | Bipetro | 648 | 0 | Illinois Basin | Mc Donough |
| 37 | C E Brehm Drilling & Production | 619 | 0 | Illinois Basin | Hamilton |
| 38 | Southern Community | 586 | 0 | Illinois Basin | Wabash |
| 39 | Vickery Drilling | 579 | 0 | Wisconsin Arch | La Salle |
| 40 | Kingwood Oil Company | 578 | 0 | Illinois Basin | Hamilton |
| 41 | R K Petroleum | 565 | 0 | Illinois Basin | White |
| 42 | George & Wrather Oil | 547 | 0 | Illinois Basin | Wabash |
| 43 | Collins Brothers Oil Company | 545 | 0 | Illinois Basin | Hamilton |
| 44 | Duncan Walter | 542 | 0 | Illinois Basin | Coles |
| 45 | Granholm & Assoc | 540 | 0 | Illinois Basin | Montgomery |
| 46 | Illinois State Geological Survey | 536 | 0 | Illinois Basin | Cook |
| 47 | Christa Oil Company | 527 | 0 | Illinois Basin | Crawford |
| 48 | Oelze Elmer Jr | 519 | 0 | Illinois Basin | Washington |
| 49 | Shakespeare Oil | 516 | 0 | Illinois Basin | Wayne |
| 50 | Illinois Power Company | 511 | 0 | Illinois Basin | St Clair |
| 51 | Skiles Oil | 510 | 0 | Illinois Basin | Crawford |
| 52 | Crete Oil Investments | 506 | 0 | Illinois Basin | Crawford |
| 53 | Fulk Perry | 504 | 0 | Illinois Basin | Richland |
| 54 | Hydrocarbon Survey | 504 | 0 | Illinois Basin | Henry |
| 55 | Sohio Petroleum Company | 499 | 0 | Illinois Basin | Marion |
| 56 | Elysium Energy | 477 | 0 | Illinois Basin | White |
| 57 | Hf Sinclair Corporation | 477 | 0 | Illinois Basin | White |
| 58 | Gallagher Victor R | 436 | 0 | Illinois Basin | Franklin |
| 59 | Pioneer Oil | 428 | 0 | Illinois Basin | Crawford |
| 60 | Farrar Oil | 423 | 0 | Illinois Basin | Franklin |
| 61 | Gulf Oil | 422 | 0 | Illinois Basin | White |
| 62 | Coy Oil | 418 | 0 | Illinois Basin | White |
| 63 | The Nation Oil Company | 417 | 0 | Illinois Basin | Wayne |
| 64 | Red Bank Oil Company | 401 | 0 | Illinois Basin | Crawford |
| 65 | Jet Oil Company | 384 | 0 | Illinois Basin | Clinton |
| 66 | Plains Illinois | 380 | 0 | Illinois Basin | Lawrence |
| 67 | Dee Drilling | 371 | 0 | Illinois Basin | Gallatin |
| 68 | Republic Oil Company | 370 | 0 | Illinois Basin | Wayne |
| 69 | Peoples Gas Light & Companyke Company | 356 | 0 | Illinois Basin | Champaign |
| 70 | Richardson M H | 355 | 0 | Illinois Basin | Douglas |
| 71 | Western Oil & Gas Dev Company | 355 | 0 | Illinois Basin | Crawford |
| 72 | Van Fossan Oil | 343 | 0 | Illinois Basin | Wayne |
| 73 | Texas Company | 338 | 0 | Illinois Basin | Marion |
| 74 | Skiles C E | 336 | 0 | Illinois Basin | Wabash |
| 75 | Zink Earnest | 334 | 0 | Illinois Basin | Edgar |
| 76 | Owner | 333 | 0 | Illinois Basin | Fayette |
| 77 | Central Il Light Company | 333 | 0 | Illinois Basin | Peoria |
| 78 | Penntex Resources Illinois | 331 | 0 | Illinois Basin | Lawrence |
| 79 | Shulman Bros | 326 | 0 | Illinois Basin | Clay |
| 80 | Continental Oil Company | 320 | 0 | Illinois Basin | Wabash |
| 81 | Assoc Pet Production | 319 | 0 | Illinois Basin | Crawford |
| 82 | Illinois Midcontinent Company | 315 | 0 | Illinois Basin | Wayne |
| 83 | Constantin E Jr | 302 | 0 | Illinois Basin | Crawford |
| 84 | Black & Black Oil Company | 302 | 0 | Illinois Basin | Crawford |
| 85 | Podolsky Bernard | 301 | 0 | Illinois Basin | Wayne |
| 86 | Vickery Drlg | 300 | 0 | Illinois Basin | Mc Lean |
| 87 | Slagter Arthur J Jr | 292 | 0 | Illinois Basin | White |
| 88 | Indiana Farm Bureau Coop Assn | 290 | 0 | Illinois Basin | Crawford |
| 89 | Bradley Producing | 285 | 0 | Illinois Basin | Lawrence |
| 90 | Energy Resource Technology Gom | 283 | 0 | Illinois Basin | Crawford |
| 91 | Humble Oil And Refining Company | 280 | 0 | Illinois Basin | Fayette |
| 92 | Robinson & Puckett | 275 | 0 | Illinois Basin | Wayne |
| 93 | Snowden Bros & Company | 274 | 0 | Illinois Basin | Lawrence |
| 94 | Obering Earnest | 273 | 0 | Illinois Basin | Madison |
| 95 | Beeson Richard W | 269 | 0 | Illinois Basin | Saline |
| 96 | Carey John Oil | 268 | 0 | Illinois Basin | Sangamon |
| 97 | Ouabache Oil & Gas Company | 265 | 0 | Illinois Basin | Crawford |
| 98 | Equinox Oil Company | 264 | 0 | Illinois Basin | White |
| 99 | Peoples Gas & Companyke Company | 263 | 0 | Illinois Basin | Will |
| 100 | Parrish Oil Production | 259 | 0 | Illinois Basin | Jasper |
Source: Buckhead Energy analysis of public oil and gas data.
Ranking: Operators ranked by total well count under their current operator-of-record. Producing-well count is wells with a first-production date on file. Drilling activity (permits, spuds, DUCs) is published only as state and county counts, never attributed to an operator.
Why it matters: Knowing who operates the most wells in Illinois helps mineral owners understand who they're dealing with at the lease level.
Refresh cadence: Daily. Data current as of 2026-11-01.
By wells operated, The Ohio Oil is the largest oil and gas operator in Illinois, with 10,782 wells on record per Buckhead Energy analysis of public oil and gas data. Note that "biggest" by revenue or market capitalization can rank differently — this measures operated well count.
The top 10 operators by operated well count are: The Ohio Oil, Marathon Oil Company, The Texas Company, Pure Oil Company, Texaco, Ohio Oil Company, The Pure Oil Company, The Carter Oil, Forest Oil, Magnolia Petroleum Company. The full top-100 ranking with well and producing-well counts is in the leaderboard below.
The Ohio Oil operates the most wells in Illinois at 10,782, per Buckhead Energy analysis of public oil and gas data.
This leaderboard ranks the top 100 operators active in Illinois by total well count. Many more file with the regulator; these are the largest by operated wells.
By wells operated — the count of wells under each company's current operator-of-record designation in the public oil and gas data Buckhead Energy analyzes. It is not a revenue, production-volume, or market-capitalization ranking.
Whether your operator is on this list or not, your Illinois mineral interest may be more valuable than you think. Get a free, no-obligation written offer.
Get Your Free Written OfferState: Illinois
Operators ranked: 100
Total wells: 85,418
Last refresh: 2026-11-01
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