| 1401 | Cincris Energy C | | Oil & Gas Operator | Jun 1991 |
| 1402 | Cinder Production Company | | Oil & Gas Operator | Apr 2014 |
| 1403 | Cinnabar Energy, LTD. | Fort Worth, TX 76107 | Oil & Gas Operator | May 2018 |
| 1404 | Cinnabar Operating, LLC | Fort Worth, TX 76121 | Oil & Gas Operator | Sep 2025 |
| 1405 | Cinnamon Creek Oil & Gas Inc | | Oil Operator | Jul 2025 |
| 1406 | Cinron Energy, LLC | Arp, TX 75750 | Oil & Gas Operator | Sep 2025 |
| 1407 | Cippele Resources Co. | Longview, TX 75608 | Oil & Gas Operator | May 1994 |
| 1408 | Circle "M" Energy Inc. | Kilgore, TX 75662 | Oil & Gas Operator | Aug 2003 |
| 1409 | Circle 9 Resources LLC | Oklahoma City, OK 73104 | Oil & Gas Operator | Jun 2025 |
| 1410 | Circle B Oil & Gas | Bowie, TX 76230 | Oil & Gas Operator | Dec 2021 |
| 1411 | Circle C Oilfield Supply Inc | Wetumka, OK 74883-0068 | Oil & Gas Operator | Apr 2017 |
| 1412 | Circle C Operations | Winnsboro, TX 75494 | Oil Operator | Sep 2025 |
| 1413 | Circle D Oil & Gas, Inc. | Brownwood, TX 76801 | Oil & Gas Operator | Sep 2025 |
| 1414 | Circle E Oil - E | | Oil Operator | May 1990 |
| 1415 | Circle H Oil Company | Big Spring, TX 79721 | Oil & Gas Operator | Apr 2020 |
| 1416 | Circle K Enterprises | | Oil & Gas Operator | Jun 2024 |
| 1417 | Circle K Oil & Gas Inc | Sand Springs, OK 74063 | Oil & Gas Operator | May 2025 |
| 1418 | Circle Ridge Production, Inc. | Graham, TX 76450 | Oil & Gas Operator | Sep 2025 |
| 1419 | Circle T Oil | | Oil Operator | Nov 2024 |
| 1420 | Circle W Oil & Gas Company | Pampa, TX 79066 | Oil & Gas Operator | Sep 2025 |
| 1421 | Circle-S Energy, LLC | McKinney, TX 75071 | Oil & Gas Operator | Sep 2025 |
| 1422 | Circleville Gas Co | Westerville, OH 43081 | Oil & Gas Operator | Dec 2004 |
| 1423 | Ciri Production Company | | Gas Operator | Mar 1994 |
| 1424 | Ciris Energy Inc | Centennial, CO 80112 | Gas Operator | Dec 2016 |
| 1425 | Cirque Resources LP | Denver, CO 80202 | Oil & Gas Operator | Aug 2016 |
| 1426 | Cirrus Exploration Company | Prosper, TX 75078 | Oil & Gas Operator | Sep 2025 |
| 1427 | Cirrus Production Company | Enid, OK 73702 | Oil & Gas Operator | May 2025 |
| 1428 | Cisco Operating LLC | Plano, TX 75024 | Oil & Gas Operator | Jun 2025 |
| 1429 | Cisco Petroleum, Inc. | | Oil & Gas Operator | Oct 2010 |
| 1430 | Cisco Production Company, LLC | Victoria, TX 77902 | Oil & Gas Operator | May 2012 |
| 1431 | Citadel Exploration Inc. | | Oil Operator | Jun 2025 |
| 1432 | Citadel Oil LLC | Edmond, OK 73083 | Oil Operator | Apr 2025 |
| 1433 | Citadel Production Company, Inc. | Denver, CO 80201 | Oil Operator | Sep 1996 |
| 1434 | Citation Energy | | Oil & Gas Operator | Jul 1993 |
| 1435 | Citation Energy Company | Marietta, OH 45750 | Oil & Gas Operator | Dec 2024 |
| 1436 | Citation Oil & G | | Oil & Gas Operator | Dec 1996 |
| 1437 | Citation Oil & Gas Corp. | Houston, TX 77269 | Oil & Gas Operator | Sep 2025 |
| 1438 | Cities Serv Oil & Gas Corp | Oklahoma City, OK 73112 | Oil & Gas Operator | Sep 1964 |
| 1439 | Cities Service Company | | Oil & Gas Operator | Mar 1983 |
| 1440 | Cities Service Oil & Gas Corp | | Oil & Gas Operator | Mar 1988 |
| 1441 | Cities Service Oil Co. | | Oil & Gas Operator | Dec 1986 |
| 1442 | Cities Services Company | | Oil & Gas Operator | Mar 2008 |
| 1443 | Citizen Energy II LLC | Tulsa, OK 74103-3729 | Oil & Gas Operator | Apr 2025 |
| 1444 | Citizen Energy III LLC | Devner, CO 80202 | Oil & Gas Operator | May 2025 |
| 1445 | Citmoco Services, Inc. | | Oil Operator | Jan 1971 |
| 1446 | Citori Oil Company | Wichita Falls, TX 76301 | Oil & Gas Operator | Nov 2004 |
| 1447 | Citori Oil Company, LLC | Wichita Falls, TX 76308 | Oil & Gas Operator | May 2014 |
| 1448 | Citronelle Operating Co., LLC | | Oil & Gas Operator | Sep 1997 |
| 1449 | Citrus Energy Corporation | Castle Rock, CO 80104 | Oil & Gas Operator | Mar 2020 |
| 1450 | Cits BK & Trust Of Springhill | | Oil & Gas Operator | Jun 1990 |
| 1451 | City & County Of Denver | | Oil & Gas Operator | Sep 2023 |
| 1452 | City Of Akron | Akron, OH 44308 | Oil & Gas Operator | Dec 2024 |
| 1453 | City Of Baker | Baker, MT 59313 | Gas Operator | Jun 2025 |
| 1454 | City Of Brady | Brady, TX 76825 | Gas Operator | Feb 1998 |
| 1455 | City Of Chanute | Chanute, KS 66720 | Oil Operator | Feb 1994 |
| 1456 | City Of Cuyahoga Falls | Cuyahoga Falls, OH 44221 | Oil & Gas Operator | Dec 2024 |
| 1457 | City Of Dumas | Dumas, TX 79029 | Gas Operator | Sep 2025 |
| 1458 | City Of Garden City, Kansas | Garden City, KS 67846 | Gas Operator | Apr 2025 |
| 1459 | City Of Hermosa Beach | | Oil & Gas Operator | Dec 2005 |
| 1460 | City Of Hugoton, Kansas | Hugoton, KS 67951 | Gas Operator | Apr 2025 |
| 1461 | City Of Huntington Beach (Fire Dept.) | | Oil & Gas Operator | Jul 2025 |
| 1462 | City Of McLean | McLean, TX 79057 | Gas Operator | Sep 2025 |
| 1463 | City Of Newport Beach | | Oil & Gas Operator | Jul 2025 |
| 1464 | City Of Santa Fe Springs | | Oil Operator | Dec 2007 |
| 1465 | City Of Satanta | Satanta, KS 67870 | Gas Operator | Apr 2025 |
| 1466 | City Of Sunray Utilities | Sunray, TX 79086 | Oil & Gas Operator | Sep 2025 |
| 1467 | City Of White Deer | White Deer, TX 79097 | Gas Operator | May 2017 |
| 1468 | City Oil Corp. Oper. For | | Oil & Gas Operator | Dec 1989 |
| 1469 | Civego, Inc. | | Oil & Gas Operator | Jul 1994 |
| 1470 | Civic Energy Corporation | Colony, OK 73021 | Oil & Gas Operator | Jun 2025 |
| 1471 | Civiletto, George & Wendy | Fredonia, NY 14063 | Gas Operator | Dec 2024 |
| 1472 | Civitas North LLC | | Oil & Gas Operator | Jun 2025 |
| 1473 | Civitas Permian Operating, LLC | The Woodlands, TX 77380 | Oil & Gas Operator | Sep 2025 |
| 1474 | Civron Petroleum Res., LLC | San Antonio, TX 78229 | Oil & Gas Operator | Sep 2025 |
| 1475 | CJ Oil Inc | Madison, KS 66860 | Oil Operator | Apr 2025 |
| 1476 | CJ Tejas Energy, LLC | Pearland, TX 77581 | Oil Operator | Sep 2025 |
| 1477 | CJR Operating LLC | Wister, OK 74966 | Gas Operator | May 2025 |
| 1478 | CJRW Oil & Gas | MC Camey, TX 79752 | Oil Operator | Sep 2025 |
| 1479 | CK Oil | | Oil Operator | Aug 2024 |
| 1480 | CK Oil & Gas LLC | Herington, KS 67449 | Oil & Gas Operator | Mar 2025 |
| 1481 | CK Operating Company, LLC | Wichita Falls, TX 76308 | Oil Operator | Sep 2025 |
| 1482 | CK Resources | Cleveland, OK 74020-0772 | Oil Operator | Aug 2013 |
| 1483 | CK5 Services LLC | Zephyr, TX 76890 | Oil & Gas Operator | Sep 2025 |
| 1484 | CKB Corporation | Borger, TX 79008 | Oil & Gas Operator | Aug 1997 |
| 1485 | CKT Energy LLC | Dallas, TX 75379 | Oil & Gas Operator | Sep 2020 |
| 1486 | CL&F Operating LLC | Spring, TX 77389 | Oil & Gas Operator | Dec 2022 |
| 1487 | Cla-Mar Oil Company, LLC | Hays, KS 67601 | Oil Operator | Dec 2019 |
| 1488 | Claassen Oil And Gas, Inc. | Estes Park, CO 80517 | Oil & Gas Operator | Apr 2025 |
| 1489 | Claborn Julia | Okmulgee, OK 74447-9781 | Oil & Gas Operator | Mar 2022 |
| 1490 | Claco Oil Co | Artesia, NM 88210 | Oil & Gas Operator | Dec 2014 |
| 1491 | Claiborne-McDonald Inc | Chickasha, OK 73018 | Oil Operator | Jul 2007 |
| 1492 | Claibourn, Darrel R. | Neodesha, KS 66757 | Oil Operator | Oct 2011 |
| 1493 | Clair Oil, Inc. | Russell, KS 67665 | Oil Operator | Nov 2019 |
| 1494 | Clamp Operating | San Antonio, TX 78264 | Oil & Gas Operator | Apr 2002 |
| 1495 | Clamp Operating Incorporated | San Antonio, TX 78264 | Oil & Gas Operator | Mar 2011 |
| 1496 | Clapp Carl O | Cedar Vale, KS 67024 | Oil Operator | Aug 2013 |
| 1497 | Clapp Oil LLC | | Oil Operator | Apr 2025 |
| 1498 | Clarco Gas Co., Inc. | Westmont, IL 60559 | Oil Operator | Dec 2011 |
| 1499 | Claremont Corporation | Tulsa, OK 74114 | Oil & Gas Operator | Feb 2017 |
| 1500 | Claremont Energy | | Gas Operator | Dec 1993 |