| 401 | Oblaen Resources LLC | Wallis, TX 77485 | Oil & Gas Operator | Oct 2025 |
| 402 | Ocean Energy, Inc. | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 403 | Okie Crude Company | Tulsa, OK 74103 | Oil & Gas Operator | Jun 2025 |
| 404 | Okie Operating Company, LTD. | Tulsa, OK 74103 | Oil & Gas Operator | Oct 2025 |
| 405 | Omega Energy Corp. | Graham, TX 76450 | Oil & Gas Operator | Oct 2025 |
| 406 | Omega Energy, LLC | Corpus Chrsti, TX 78418 | Oil & Gas Operator | Oct 2025 |
| 407 | Omni Oil & Gas, Inc. | San Antonio, TX 78229 | Oil & Gas Operator | Oct 2017 |
| 408 | Omni Operating Company(A) | Dallas, TX 75370 | Oil & Gas Operator | Oct 2025 |
| 409 | Opex Energy, LLC | Houston, TX 77042 | Oil & Gas Operator | Mar 2008 |
| 410 | Orr Production Company | Austin, TX 78746 | Oil & Gas Operator | Dec 2000 |
| 411 | Outline Oil Company LLC | Beeville, TX 78104 | Oil Operator | Oct 2025 |
| 412 | Overly Operating Co. | San Antonio, TX 78209 | Oil & Gas Operator | Jul 2013 |
| 413 | Oxy USA Inc | Houston, TX 77046 | Oil & Gas Operator | Oct 2025 |
| 414 | Pacific Operators, Inc. | San Antonio, TX 78205 | Oil & Gas Operator | Mar 1999 |
| 415 | Panhandle Producing Company | San Antonio, TX 78205 | Oil & Gas Operator | Oct 1993 |
| 416 | Panther Creek Resources, LLC | Denver, CO 80202 | Oil & Gas Operator | May 2012 |
| 417 | Parker & Parsley Development L.P | Midland, TX 79702 | Oil & Gas Operator | Oct 2007 |
| 418 | Parker & Parsley Producing L.P. | Midland, TX 79702 | Oil & Gas Operator | Oct 1997 |
| 419 | Pathfinder Exploration LLC | Norman, OK 73069-8516 | Gas Operator | Aug 2003 |
| 420 | Peak Energy Corporation | Plano, TX 75093 | Oil & Gas Operator | Oct 2018 |
| 421 | Pearl, Bill H. Productions, Inc. | Corpus Chrsti, TX 78460 | Oil & Gas Operator | Oct 2025 |
| 422 | Pedeco, Inc. | Casper, WY 82601 | Oil & Gas Operator | Mar 2008 |
| 423 | Pennzenergy Exp. & Prod., L.L.C. | Houston, TX 77210 | Oil & Gas Operator | Mar 2000 |
| 424 | Pennzoil Exploration & Production Co. | Carthage, TX 75633 | Oil & Gas Operator | Mar 2008 |
| 425 | Peoples Energy Prod.-TX, L.P. | Houston, TX 77002 | Oil & Gas Operator | Sep 2007 |
| 426 | Perdido Energy, LLC | Houston, TX 77251 | Oil & Gas Operator | Oct 2025 |
| 427 | Petro-Hunt Corporation | Dallas, TX 75201 | Oil & Gas Operator | Jun 2003 |
| 428 | Petro-Hunt, L.L.C. | Dallas, TX 75201 | Oil & Gas Operator | Oct 2025 |
| 429 | Petro-Smith Operating LLC | Houston, TX 77010 | Oil & Gas Operator | Oct 2025 |
| 430 | Petrohawk Operating Company | Houston, TX 77056 | Oil & Gas Operator | Oct 2021 |
| 431 | Petroleum Management, Inc. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Oct 2025 |
| 432 | Petropoint Energy Operating, LLC | Houston, TX 77098 | Oil & Gas Operator | Oct 2025 |
| 433 | Phillips Petroleum Company | Houston, TX 77251 | Oil & Gas Operator | Mar 2013 |
| 434 | Phoenix Fund, Inc. | San Antonio, TX 78217 | Oil & Gas Operator | Jun 2000 |
| 435 | Phoenix Operating Company Of TX. | Dallas, TX 75206 | Oil & Gas Operator | Jun 1995 |
| 436 | Pierce Junction Petroleum Inc. | Houston, TX 77002 | Oil & Gas Operator | May 2010 |
| 437 | Pierco Energy Corp. | Dallas, TX 75231 | Oil & Gas Operator | Oct 2025 |
| 438 | Pinon Corporation | San Antonio, TX 78266 | Oil & Gas Operator | Jul 2001 |
| 439 | Pintail Production Co., Inc. | Fort Worth, TX 76132 | Oil & Gas Operator | Oct 2025 |
| 440 | Pioneer Natural Res. USA, Inc. | Spring, TX 77389 | Oil & Gas Operator | Oct 2025 |
| 441 | Pioneer Resources Producing, L.P | Irving, TX 75039 | Oil & Gas Operator | Feb 2001 |
| 442 | Plains Exploration & Prod. Co. | Houston, TX 77002 | Oil & Gas Operator | Jul 2013 |
| 443 | Plains Marketing, LP | Cushing, OK 74023 | Oil Operator | Jan 2012 |
| 444 | Pogo Producing Company | Houston, TX 77002 | Oil & Gas Operator | Jan 2008 |
| 445 | Pogo Producing Company LLC | Houston, TX 77002 | Oil & Gas Operator | Jul 2025 |
| 446 | Precio Energy, LLC | Beaumont, TX 77726 | Oil & Gas Operator | Oct 2025 |
| 447 | Premier Natural Resources, L.P. | Tulsa, OK 74105 | Oil & Gas Operator | Feb 2007 |
| 448 | Premier Natural Resources, LLC | Tulsa, OK 74136 | Oil & Gas Operator | Oct 2025 |
| 449 | Prevail Energy, Inc | Corpus Chrsti, TX 78469 | Oil & Gas Operator | Oct 2025 |
| 450 | Price Drilling & Exploration Co. | Benavides, TX 78341 | Oil & Gas Operator | Jul 2013 |
| 451 | Pride Energy Company | Tulsa, OK 74170 | Oil & Gas Operator | Oct 2025 |
| 452 | Prime Operating Company | Houston, TX 77024 | Oil & Gas Operator | Oct 2025 |
| 453 | Proex Energy Management, L.L.C. | Spring, TX 77386 | Oil & Gas Operator | Oct 2025 |
| 454 | Proline Energy Resources Inc | Sugar Land, TX 77479 | Oil & Gas Operator | Oct 2025 |
| 455 | Proton Energy, L.L.C. | Houston, TX 77002 | Oil & Gas Operator | Jun 2005 |
| 456 | Pursuit Oil & Gas STX, LLC | Houston, TX 77024 | Oil & Gas Operator | Oct 2025 |
| 457 | Pursuit Oil & Gas, LLC | Houston, TX 77024 | Gas Operator | Sep 2019 |
| 458 | PXP Gulf Coast Inc. | Houston, TX 77002 | Oil & Gas Operator | Mar 2015 |
| 459 | Quest Research & Dev. Corp. | Weatherford, TX 76086 | Oil & Gas Operator | Oct 2025 |
| 460 | R. K. G. Engineering, Inc. | Odessa, TX 79760 | Oil & Gas Operator | Oct 2025 |
| 461 | R.C.I. Energy | Alice, TX 78333 | Oil & Gas Operator | Oct 2025 |
| 462 | Radius Operating, LLC | Round Rock, TX 78664 | Oil & Gas Operator | Oct 2025 |
| 463 | Raker Resources LLC | Houston, TX 77042 | Oil & Gas Operator | Oct 2025 |
| 464 | Ramtex Energy LLC | Tulsa, OK 74114 | Oil & Gas Operator | Oct 2025 |
| 465 | Rancho Blanco Corporation | San Antonio, TX 78205 | Oil & Gas Operator | Apr 1995 |
| 466 | Red Water Resources, Inc. | Tulsa, OK 74159 | Oil & Gas Operator | Oct 2025 |
| 467 | Reddy Disposals, LLC | Beeville, TX 78104 | Oil Operator | Oct 2025 |
| 468 | Redwood Operating, Inc. | Houston, TX 77058 | Oil & Gas Operator | Oct 2025 |
| 469 | Reef Exploration, L.P. | Richardson, TX 75080 | Oil & Gas Operator | Oct 2025 |
| 470 | Rego Development Company, Inc. | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Apr 2002 |
| 471 | Reh Energy, Inc. | Corpus Chrsti, TX 78413 | Oil & Gas Operator | Oct 2025 |
| 472 | Reichmann Petroleum Corp. | Grapevine, TX 76051 | Oil & Gas Operator | Oct 2025 |
| 473 | Remora Operating LLC | Houston, TX 77056 | Oil & Gas Operator | Oct 2025 |
| 474 | Reo Operating LLC | Austin, TX 78747 | Oil & Gas Operator | Oct 2025 |
| 475 | Resource Management Company | Fredericksbrg, TX 78624 | Oil & Gas Operator | Feb 2015 |
| 476 | Richman Petroleum Corp. | Grapevine, TX 76051 | Oil & Gas Operator | Jul 2006 |
| 477 | Ricochet Energy, Inc. | San Antonio, TX 78258 | Oil & Gas Operator | Oct 2025 |
| 478 | Riddle Engineering Corp. | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Jul 2011 |
| 479 | Rim Operating, Inc. | Englewood, CO 80112 | Oil & Gas Operator | Oct 2025 |
| 480 | Rincon Petroleum Corporation | Corpus Chrsti, TX 78427 | Oil & Gas Operator | Oct 2025 |
| 481 | Rio Exploration Company | San Antonio, TX 78209 | Gas Operator | Dec 2005 |
| 482 | Rio Grand Exploration, LLC | San Antonio, TX 78216 | Oil & Gas Operator | Oct 2025 |
| 483 | Rio Grande E&P II, LLC | Houston, TX 77092 | Gas Operator | Oct 2025 |
| 484 | Rio Grande Energy | Laredo, TX 78041 | Oil & Gas Operator | May 2004 |
| 485 | Ritter Properties, LTD. | Fredericksbrg, TX 78624 | Oil & Gas Operator | Oct 2025 |
| 486 | Rme Petroleum Company | Houston, TX 77251 | Oil & Gas Operator | Nov 2016 |
| 487 | RNG Resources, LLC | Corpus Chrsti, TX 78413 | Gas Operator | Oct 2025 |
| 488 | Robertson Resources, Inc. | Horseshoe Bay, TX 78657 | Oil & Gas Operator | Oct 2025 |
| 489 | Robison, J. H. & Assoc. LTD. | Corpus Chrsti, TX 78413 | Oil & Gas Operator | Apr 1996 |
| 490 | Rockdale Energy, LLC | Houston, TX 77024 | Oil & Gas Operator | Dec 2020 |
| 491 | Rockford Energy Partners II, LLC | Tulsa, OK 74103 | Oil & Gas Operator | Sep 2007 |
| 492 | Rollert Co., Inc., The | Luling, TX 78648 | Oil & Gas Operator | Nov 2000 |
| 493 | Ronde Operating, LLC | Houston, TX 77006 | Oil & Gas Operator | Mar 2021 |
| 494 | Rosetta Resources Operating LP | San Antonio, TX 78216 | Oil & Gas Operator | Oct 2025 |
| 495 | Rosewood Resources, Inc. | Dallas, TX 75201 | Oil & Gas Operator | Oct 2025 |
| 496 | Rowden Oil & Gas, Inc. | San Antonio, TX 78209 | Oil & Gas Operator | Jun 2023 |
| 497 | Royal Oil & Gas Corp. | Indiana, PA 15701 | Oil & Gas Operator | Apr 2014 |
| 498 | Royal Production Company, Inc. | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Oct 2025 |
| 499 | RWJ Operating LLC | Dallas, TX 75201 | Oil & Gas Operator | Oct 2025 |
| 500 | Rystin Oil & Gas | Sugar Land, TX 77487 | Oil & Gas Operator | Oct 2025 |