| 20401 | O & G Energy, Inc. | Abilene, TX 79608 | Oil & Gas Operator | Oct 1996 |
| 20402 | O & O Operators, LLC. | Fate, TX 75132 | Oil & Gas Operator | Sep 2026 |
| 20403 | O G & E | Oklahoma City, OK 73124 | Oil & Gas Operator | Feb 2014 |
| 20404 | O H Berry | Midland, TX 79702 | Oil & Gas Operator | Feb 2003 |
| 20405 | O Hill Enterprises, Inc. | La Grange, TX 78945 | Oil & Gas Operator | Jan 2014 |
| 20406 | O I L Energy Corp | | Oil & Gas Operator | Oct 2017 |
| 20407 | O I L Niagaran LLC | | Oil & Gas Operator | May 2017 |
| 20408 | O K Swabbing Inc | Hennessey, OK 73742 | Oil & Gas Operator | May 2026 |
| 20409 | O S & J Operatin | | Oil Operator | Nov 1984 |
| 20410 | O S & S Oil Company | Electra, TX 76360 | Oil & Gas Operator | Jan 2018 |
| 20411 | O&G Investments Inc. | Runge, TX 78151 | Oil & Gas Operator | Feb 2003 |
| 20412 | O'Bar Operating Co., Inc. | Longview, TX 75604 | Oil & Gas Operator | Sep 2026 |
| 20413 | O'Benco, Inc. | Shreveport, LA 71136 | Oil & Gas Operator | Sep 2026 |
| 20414 | O'Blue Corp. | Kerrville, TX 78028 | Oil & Gas Operator | Mar 1998 |
| 20415 | O'Boyle Energy Corporation | | Oil Operator | Feb 1991 |
| 20416 | O'Brien Energy Company | Shreveport, LA 71136 | Oil & Gas Operator | Sep 2019 |
| 20417 | O'Brien Energy Resources Corp | Portsmouth, NH 03801 | Oil & Gas Operator | Sep 2026 |
| 20418 | O'Brien Oil Corporation | Guthrie, OK 73044-3154 | Oil & Gas Operator | May 2026 |
| 20419 | O'Brien Oil LLC | Guthrie, OK 73044-3154 | Oil & Gas Operator | Apr 2020 |
| 20420 | O'Brien Operating Company | Shreveport, LA 71164 | Oil & Gas Operator | Dec 2004 |
| 20421 | O'Brien Resources LLC | Shreveport, LA 71136 | Oil Operator | Nov 2017 |
| 20422 | O'Brien, George H. Jr. | Midland, TX 79701 | Oil & Gas Operator | Jun 1994 |
| 20423 | O'Brien-Sill | | Oil & Gas Operator | Jul 2026 |
| 20424 | O'Connell, James P. | Vacaville, CA 95687 | Oil Operator | Nov 2009 |
| 20425 | O'Connor & Hewitt, LTD. | Victoria, TX 77901 | Oil & Gas Operator | Jun 1998 |
| 20426 | O'Connor Energy Management, LLC | Victoria, TX 77902 | Oil Operator | Sep 2026 |
| 20427 | O'Connor, Emma | Hamburg, NY 14075 | Gas Operator | Dec 2025 |
| 20428 | O'Dell, Mitchell | Cross Plains, TX 76443 | Oil & Gas Operator | Sep 2026 |
| 20429 | O'Donnell Bill C | Tulsa, OK 74135-4241 | Oil & Gas Operator | Oct 2014 |
| 20430 | O'Donnell Oil LLC | | Oil & Gas Operator | Jul 2026 |
| 20431 | O'Donohoe, Jack | Wichita Falls, TX 76301 | Oil & Gas Operator | May 2002 |
| 20432 | O'Gorman, Brendan & Wheeler, Anne | North Collins, NY 14111 | Gas Operator | Dec 2025 |
| 20433 | O'Gorman, Kevin | Eden, NY 14057 | Gas Operator | Dec 2025 |
| 20434 | O'Hare Energy Co | | Oil Operator | Dec 1983 |
| 20435 | O'Hern Morris D | Mounds, OK 74047-5163 | Oil & Gas Operator | Sep 2016 |
| 20436 | O'Leary'S Oil & Gas Inc. | Arcadia, FL 34266 | Oil & Gas Operator | May 2008 |
| 20437 | O'Malley Production Co Inc. | | Oil & Gas Operator | Mar 1988 |
| 20438 | O'Meara LLC | | Oil & Gas Operator | Oct 2022 |
| 20439 | O'Meara, Inc. | | Oil & Gas Operator | Dec 2006 |
| 20440 | O'Neal Cattle Co. | Pampa, TX 79066 | Gas Operator | Sep 2026 |
| 20441 | O'Neal Oil & Gas Co | Fort Worth, TX 76107-1479 | Oil & Gas Operator | Jun 2026 |
| 20442 | O'Neal Oil Company | Nocona, TX 76255 | Oil & Gas Operator | Sep 2026 |
| 20443 | O'Neal Operating Company | Wichita Falls, TX 76307 | Oil & Gas Operator | Dec 1999 |
| 20444 | O'Neal, Lindell | Nocona, TX 76255 | Oil & Gas Operator | May 2026 |
| 20445 | O'Neil Properties LTD | Midland, TX 79702 | Oil & Gas Operator | Jun 2015 |
| 20446 | O'Neil, Pat | Wichita Falls, TX 76308 | Oil & Gas Operator | Nov 2005 |
| 20447 | O'Neill Properties, LTD. | Midland, TX 79702 | Oil & Gas Operator | Sep 2026 |
| 20448 | O'Ryan Oil And Gas | Odessa, TX 79768 | Oil & Gas Operator | Sep 2026 |
| 20449 | O'Sand Production, Inc. | Tomball, TX 77377 | Oil & Gas Operator | Aug 2003 |
| 20450 | O'Sullivan & Scully, Inc. | | Oil & Gas Operator | Oct 1994 |
| 20451 | O'Sullivan Oil & Gas Co., Inc. | Houston, TX 77002 | Oil & Gas Operator | Oct 2000 |
| 20452 | O'Tool Oil & Gas, LLC | Dallas, TX 75205 | Oil & Gas Operator | Sep 2026 |
| 20453 | O. B. And Keith Whatley | | Oil Operator | Jul 1993 |
| 20454 | O. B. Beck | | Oil Operator | Feb 1991 |
| 20455 | O. B. Mobley | | Oil & Gas Operator | Jul 1989 |
| 20456 | O. B. Mobley, Et Al | | Oil Operator | Jul 1989 |
| 20457 | O. B. Whatley | | Oil Operator | Jul 1993 |
| 20458 | O. D. Maybrier | | Oil Operator | Dec 2011 |
| 20459 | O. F. H., Inc. | | Oil Operator | May 1990 |
| 20460 | O. G., Inc. | | Oil & Gas Operator | Nov 1992 |
| 20461 | O. H. B. Inc. | San Angelo, TX 76902 | Oil & Gas Operator | Sep 2019 |
| 20462 | O. H. M. Operating | Pampa, TX 79065 | Oil & Gas Operator | Sep 2026 |
| 20463 | O. O. Cummings | | Gas Operator | Jan 1999 |
| 20464 | O.B. Whatley Oil Company, Inc. | | Oil Operator | Feb 2013 |
| 20465 | O.B., Keith & Owen B. Whatley | | Oil Operator | Jul 1989 |
| 20466 | O.G.O. Refining | Luling, TX 78648 | Oil & Gas Operator | Jun 2013 |
| 20467 | O.G.P. Operating, Inc. | Dallas, TX 75231 | Oil & Gas Operator | Sep 2026 |
| 20468 | O.I.L. Energy, Inc. | | Oil & Gas Operator | Dec 1984 |
| 20469 | O.T. Oil | Kilgore, TX 75663 | Oil Operator | Sep 2026 |
| 20470 | Oahe Oil Company | Texline, TX 79087 | Oil & Gas Operator | May 2004 |
| 20471 | Oak Dale Drilling Co | Logan, OH 43138-1851 | Oil & Gas Operator | Dec 2015 |
| 20472 | Oak Energy, LLC | Houston, TX 77027 | Oil & Gas Operator | Sep 2026 |
| 20473 | Oak Grove Resources, LLC | | Gas Operator | Aug 2025 |
| 20474 | Oak Hill Petroleum Corporation | Oklahoma City, OK 73116-5627 | Oil & Gas Operator | May 2026 |
| 20475 | Oak Hills Drilling & Oper., LLC | Holdenville, OK 74848 | Oil & Gas Operator | May 2013 |
| 20476 | Oak Hills Energy Inc | Holdenville, OK 74848-0470 | Oil & Gas Operator | Sep 2014 |
| 20477 | Oak Prairie Operations, LLC | The Woodlands, TX 77381 | Oil & Gas Operator | Sep 2026 |
| 20478 | Oak Resources Inc | Tulsa, OK 74153 | Oil & Gas Operator | Aug 2013 |
| 20479 | Oak Ridge LLC | Wellsville, KS 66092 | Oil Operator | Dec 2019 |
| 20480 | Oak Tree Natural Res LLC | Oklahoma City, OK 73120-5065 | Oil & Gas Operator | Mar 2015 |
| 20481 | Oak Valley Operating, LLC | The Woodlands, TX 77380 | Oil & Gas Operator | Jun 2015 |
| 20482 | Oak Valley SWD LLC | Enid, OK 73703-4637 | Oil Operator | Aug 2022 |
| 20483 | Oakes Gas Co Inc | Kane, PA 16735-3905 | Gas Operator | Dec 2023 |
| 20484 | Oakfield Energy LLC | | Oil Operator | Jun 2019 |
| 20485 | Oakland Corporation | | Oil & Gas Operator | Dec 1981 |
| 20486 | Oakland Petroleum Oper Co., Inc. | Kilgore, TX 75663 | Oil & Gas Operator | Sep 2026 |
| 20487 | Oakley Oil & Gas, L.L.C. | | Oil & Gas Operator | Mar 2012 |
| 20488 | Oakmont CC | Oakmont, PA 15139-1135 | Gas Operator | Dec 2024 |
| 20489 | Oakmont Oil And Gas | Graham, TX 76450 | Oil & Gas Operator | Sep 2026 |
| 20490 | Oakridge Energy, Inc. | Wichita Falls, TX 76302 | Oil & Gas Operator | Sep 2026 |
| 20491 | Oakridge Oil And Gas, LP | Jacksboro, TX 76458 | Oil & Gas Operator | Sep 2026 |
| 20492 | Oaks Petroleum I | | Oil Operator | Jul 1987 |
| 20493 | Oaktree Oil Company | Albany, TX 76430 | Oil & Gas Operator | Sep 2026 |
| 20494 | Oakwood Resources Inc | Dallas, TX 75374 | Oil & Gas Operator | May 1998 |
| 20495 | Oasis Energy Resources LLC | Norman, OK 73072-9668 | Oil & Gas Operator | Jun 2025 |
| 20496 | Oasis Operating, Inc. | Lubbock, TX 79404 | Oil & Gas Operator | Nov 2020 |
| 20497 | Oasis Petroleum North America LLC | Houston, TX 77002 | Oil & Gas Operator | Jun 2026 |
| 20498 | Oasis Petroleum Permian LLC | Houston, TX 77002 | Oil & Gas Operator | Sep 2026 |
| 20499 | Oasis Production Co., Inc. | | Oil & Gas Operator | Jun 1988 |
| 20500 | Oast, Thomas H. | Greenville, NC 27835 | Oil Operator | Nov 1985 |