| 1401 | Cirque Resources LP | Denver, CO 80202 | Oil & Gas Operator | Aug 2016 |
| 1402 | Cirrus Exploration Company | Prosper, TX 75078 | Oil & Gas Operator | Apr 2026 |
| 1403 | Cirrus Production Company | Enid, OK 73702 | Oil & Gas Operator | Jan 2026 |
| 1404 | Cisco Operating LLC | Plano, TX 75024 | Oil & Gas Operator | Feb 2026 |
| 1405 | Cisco Petroleum, Inc. | | Oil & Gas Operator | Oct 2010 |
| 1406 | Cisco Production Company, LLC | Victoria, TX 77902 | Oil & Gas Operator | May 2012 |
| 1407 | Citadel Exploration Inc. | | Oil Operator | Dec 2025 |
| 1408 | Citadel Oil LLC | Edmond, OK 73083 | Oil Operator | Dec 2025 |
| 1409 | Citadel Prod Company Inc | Denver, CO 80201 | Oil Operator | Sep 1996 |
| 1410 | Citation Energy | | Oil & Gas Operator | Jul 1993 |
| 1411 | Citation Energy Company | Marietta, OH 45750 | Oil & Gas Operator | Dec 2025 |
| 1412 | Citation Oil & G | | Oil & Gas Operator | Dec 1996 |
| 1413 | Citation Oil & Gas Corp | Houston, TX 77269 | Oil & Gas Operator | Apr 2026 |
| 1414 | Cities Serv Oil & Gas Corp | Oklahoma City, OK 73112 | Oil & Gas Operator | Sep 1964 |
| 1415 | Cities Service Company | | Oil & Gas Operator | Mar 1983 |
| 1416 | Cities Service Oil & Gas Corp | | Oil & Gas Operator | Mar 1988 |
| 1417 | Cities Service Oil Co. | | Oil & Gas Operator | Dec 1986 |
| 1418 | Cities Services Company | | Oil & Gas Operator | Mar 2008 |
| 1419 | Citizen Energy II LLC | Tulsa, OK 74103-3729 | Oil & Gas Operator | Apr 2025 |
| 1420 | Citizen Energy III LLC | Devner, CO 80202 | Oil & Gas Operator | Jan 2026 |
| 1421 | Citizen Energy Ventures LLC | Tulsa, OK 74103 | Oil & Gas Operator | Jan 2026 |
| 1422 | Citmoco Services, Inc. | | Oil Operator | Jan 1971 |
| 1423 | Citori Oil Company | Wichita Falls, TX 76301 | Oil & Gas Operator | Nov 2004 |
| 1424 | Citori Oil Company, LLC | Wichita Falls, TX 76308 | Oil & Gas Operator | May 2014 |
| 1425 | Citronelle Operating Co., LLC | | Oil & Gas Operator | Sep 1997 |
| 1426 | Citrus Energy Corporation | Castle Rock, CO 80104 | Oil & Gas Operator | Dec 2025 |
| 1427 | Cits BK & Trust Of Springhill | | Oil & Gas Operator | Jun 1990 |
| 1428 | City & County Of Denver | | Oil & Gas Operator | Sep 2023 |
| 1429 | City Of Akron | Akron, OH 44308 | Oil & Gas Operator | Dec 2025 |
| 1430 | City Of Baker | Baker, MT 59313 | Oil & Gas Operator | Feb 2026 |
| 1431 | City Of Brady | Brady, TX 76825 | Gas Operator | Feb 1998 |
| 1432 | City Of Chanute | Chanute, KS 66720 | Oil Operator | Feb 1994 |
| 1433 | City Of Dumas | Dumas, TX 79029 | Gas Operator | Apr 2026 |
| 1434 | City Of Garden City, Kansas | Garden City, KS 67846 | Gas Operator | Dec 2025 |
| 1435 | City Of Hermosa Beach | | Oil & Gas Operator | Dec 2005 |
| 1436 | City Of Hugoton, Kansas | Hugoton, KS 67951 | Gas Operator | Dec 2025 |
| 1437 | City Of Huntington Beach (Fire Dept.) | | Oil & Gas Operator | Dec 2025 |
| 1438 | City Of McLean | McLean, TX 79057 | Gas Operator | Aug 2025 |
| 1439 | City Of Newport Beach | | Oil & Gas Operator | Dec 2025 |
| 1440 | City Of Santa Fe Springs | | Oil Operator | Dec 2007 |
| 1441 | City Of Satanta | Satanta, KS 67870 | Gas Operator | Dec 2025 |
| 1442 | City Of Sunray Utilities | Sunray, TX 79086 | Oil & Gas Operator | Apr 2026 |
| 1443 | City Of White Deer | White Deer, TX 79097 | Gas Operator | May 2017 |
| 1444 | City Oil Corp. Oper. For | | Oil & Gas Operator | Dec 1989 |
| 1445 | Civego, Inc. | | Oil & Gas Operator | Jul 1994 |
| 1446 | Civic Energy Corporation | Colony, OK 73021 | Oil & Gas Operator | Jan 2026 |
| 1447 | Civiletto, George & Wendy | Fredonia, NY 14063 | Gas Operator | Dec 2024 |
| 1448 | Civitas North LLC | | Oil & Gas Operator | Jan 2026 |
| 1449 | Civitas Permian Operating, LLC | Midland, TX 79707 | Oil & Gas Operator | Apr 2026 |
| 1450 | Civron Petroleum Res., LLC | San Antonio, TX 78229 | Oil & Gas Operator | Apr 2026 |
| 1451 | CJ Oil Inc | Madison, KS 66860 | Oil Operator | Dec 2025 |
| 1452 | CJR Operating LLC | Wister, OK 74966 | Gas Operator | Feb 2026 |
| 1453 | CJRW Oil & Gas | MC Camey, TX 79752 | Oil Operator | Apr 2026 |
| 1454 | CK Oil | | Oil Operator | Aug 2025 |
| 1455 | CK Oil & Gas LLC | Herington, KS 67449 | Oil & Gas Operator | Mar 2025 |
| 1456 | CK Operating Company, LLC | Wichita Falls, TX 76308 | Oil Operator | Dec 2025 |
| 1457 | CK Resources | Cleveland, OK 74020-0772 | Oil Operator | Aug 2013 |
| 1458 | CK5 Services LLC | Zephyr, TX 76890 | Oil & Gas Operator | Sep 2025 |
| 1459 | CKB Corporation | Borger, TX 79008 | Oil & Gas Operator | Aug 1997 |
| 1460 | CKT Energy LLC | Dallas, TX 75379 | Oil & Gas Operator | Sep 2020 |
| 1461 | CL&F Operating LLC | Spring, TX 77389 | Oil & Gas Operator | Dec 2022 |
| 1462 | Cla-Mar Oil Company, LLC | Hays, KS 67601 | Oil Operator | Dec 2019 |
| 1463 | Claassen Oil And Gas Inc | Estes Park, CO 80517 | Oil & Gas Operator | Jan 2026 |
| 1464 | Claborn Julia | Okmulgee, OK 74447-9781 | Oil & Gas Operator | Mar 2022 |
| 1465 | Claco Oil Co | Artesia, NM 88210 | Oil & Gas Operator | Dec 2014 |
| 1466 | Claiborne-McDonald Inc | Chickasha, OK 73018 | Oil Operator | Jul 2007 |
| 1467 | Claibourn, Darrel R. | Neodesha, KS 66757 | Oil Operator | Oct 2011 |
| 1468 | Clair Oil, Inc. | Russell, KS 67665 | Oil Operator | Nov 2019 |
| 1469 | Clamp Operating | San Antonio, TX 78264 | Oil & Gas Operator | Apr 2002 |
| 1470 | Clamp Operating Incorporated | San Antonio, TX 78264 | Oil & Gas Operator | Mar 2011 |
| 1471 | Clapp Carl O | Cedar Vale, KS 67024 | Oil Operator | Aug 2013 |
| 1472 | Clapp Oil LLC | | Oil Operator | Dec 2025 |
| 1473 | Clarco Gas Co., Inc. | Westmont, IL 60559 | Oil Operator | Dec 2011 |
| 1474 | Claremont Corporation | Tulsa, OK 74114 | Oil & Gas Operator | Jan 2026 |
| 1475 | Claremont Energy | | Gas Operator | Dec 1993 |
| 1476 | Claremont Exploration Inc | Tulsa, OK 74103-4107 | Oil & Gas Operator | Jun 1997 |
| 1477 | Clarence F. Routon, Jr. | | Oil Operator | Apr 1990 |
| 1478 | Clarence K Tussel Jr LTD | Jefferson, OH 44047 | Oil & Gas Operator | Dec 2025 |
| 1479 | Clarence R. Barnett Inc. | | Oil & Gas Operator | Jul 2025 |
| 1480 | Clarita Operating LLC | Ada, OK 74821 | Oil Operator | Jun 2022 |
| 1481 | Clark And Clark | Princeton, NJ 08540-1930 | Oil & Gas Operator | Jul 2013 |
| 1482 | Clark B & Cahoj | | Oil Operator | Apr 1995 |
| 1483 | Clark Blake | | Gas Operator | Sep 2023 |
| 1484 | Clark Energy, LLC | Chanute, KS 66720 | Oil & Gas Operator | Jun 2022 |
| 1485 | Clark Exploratio | | Oil & Gas Operator | Jun 1991 |
| 1486 | Clark Exploration Company | Highlands Ranch, CO 80126-7645 | Oil & Gas Operator | Nov 2024 |
| 1487 | Clark Krista | Ada, OK 74820-8595 | Oil Operator | Sep 2001 |
| 1488 | Clark Oil & Gas Inc | | Oil & Gas Operator | Dec 1990 |
| 1489 | Clark Oil Co. | Dallas, TX 75360 | Oil & Gas Operator | Apr 2026 |
| 1490 | Clark Oil Producing Company | | Oil & Gas Operator | Oct 1979 |
| 1491 | Clark Oil, LLC | Wellsville, KS 66092 | Oil Operator | Apr 2022 |
| 1492 | Clark Operating | Wichita Falls, TX 76308 | Oil & Gas Operator | Aug 2003 |
| 1493 | Clark Operating Inc. | Wichita Falls, TX 76308 | Oil & Gas Operator | Apr 2026 |
| 1494 | Clark Operating Services Inc | Okmulgee, OK 74447 | Oil & Gas Operator | May 2013 |
| 1495 | Clark Well Service | Depew, OK 74028-0296 | Oil & Gas Operator | Aug 2013 |
| 1496 | Clark, B. C. | Cross Plains, TX 76443 | Oil Operator | Dec 2007 |
| 1497 | Clark, Daniel J. | Auburn, NY 13021 | Gas Operator | Dec 2024 |
| 1498 | Clark, Daryl | Phillipsburg, KS 67661 | Oil Operator | Oct 2025 |
| 1499 | Clark, Donald E. | | Gas Operator | Dec 2003 |
| 1500 | Clark, Donald-Roger Young | | Oil & Gas Operator | Jan 1988 |