California's San Joaquin Basin is the state's most productive oil region, home to giant heavy-oil and diatomite fields across Kern County.
The San Joaquin Basin has approximately 172,566 wells operated by 3,180 companies. Below are the largest operators by well count. Data as of 2026-09-03.
| # | Operator | Wells | Have produced |
|---|---|---|---|
| 1 | Aera Energy | 53,549 | 36,495 |
| 2 | Chevron | 50,707 | 34,056 |
| 3 | California Resources Production | 10,880 | 6,204 |
| 4 | Sentinel Peak Resources Ca | 8,463 | 6,112 |
| 5 | Berry Petroleum Company | 8,379 | 6,280 |
| 6 | California Resources Elk Hills LLC | 7,567 | 6,767 |
| 7 | E & B Natural Resources Management | 3,213 | 2,037 |
| 8 | Crimson Resource Management | 2,198 | 1,434 |
| 9 | Holmes Western Oil | 1,406 | 979 |
| 10 | Macpherson Oil Company | 1,238 | 873 |
| 11 | Shell Oil Company | 1,141 | 73 |
| 12 | Mobil Oil | 793 | 69 |
| 13 | Arco Western Energy | 594 | 68 |
| 14 | San Joaquin Facilities Management | 586 | 445 |
| 15 | Bellaire Oil Company | 536 | 474 |
| 16 | Hunter Edison Oil Development Ltd. | 525 | 509 |
| 17 | Naftex Operating Company | 440 | 334 |
| 18 | Hathaway | 431 | 311 |
| 19 | Kern River Holdings Ii LLC | 410 | 322 |
| 20 | TRC Operating Company Inc. | 312 | 295 |
| 21 | Union Oil Company Of California | 298 | 11 |
| 22 | Petrolud | 291 | 207 |
| 23 | Texaco Producing | 287 | — |
| 24 | Sequoia Exploration | 273 | 231 |
| 25 | Phillips Petroleum Company | 252 | 15 |
The largest operators in the San Joaquin Basin by well count in this snapshot are Aera Energy (53,549 wells), Chevron (50,707 wells), California Resources Production (10,880 wells), Sentinel Peak Resources Ca (8,463 wells), Berry Petroleum Company (8,379 wells). The snapshot includes 3,180 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.
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Well counts come from Buckhead Energy analysis of public oil and gas data (data as of 2026-09-03); reflect wells where each company is the current operator of record in the San Joaquin Basin. Informational only.
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