| 501 | Mortimer Exploration Company | San Antonio, TX 78209 | Oil & Gas Operator | Sep 2003 |
| 502 | Mountain V Texas, LLC | | Oil & Gas Operator | Dec 2025 |
| 503 | MPG Petroleum | San Antonio, TX 78217 | Oil & Gas Operator | Aug 2003 |
| 504 | Mueller Engineering Corp. | Corpus Chrsti, TX 78476 | Oil & Gas Operator | Feb 2002 |
| 505 | Mueller Exploration, Inc. | Portland, TX 78374 | Oil & Gas Operator | Dec 2025 |
| 506 | Munson, Charles C. | Dallas, TX 75201 | Oil & Gas Operator | Apr 2002 |
| 507 | Mustang Energy Inc. | Porter, TX 77365 | Oil & Gas Operator | Mar 2008 |
| 508 | Mustang Oil & Gas Corporation | Wichita Falls, TX 76308 | Oil & Gas Operator | Jul 2021 |
| 509 | Nadcf Recovery Group, Inc. | Chapin, SC 29036 | Oil & Gas Operator | Dec 2025 |
| 510 | Nance Engineering Inc. | Houston, TX 77058 | Oil & Gas Operator | Mar 2002 |
| 511 | National Energy Group Inc | Dallas, TX 75206 | Oil & Gas Operator | Sep 2014 |
| 512 | National Investors Group | Warren, OH 44481 | Oil & Gas Operator | Nov 1996 |
| 513 | NBL Permian LLC | Houston, TX 77070 | Oil & Gas Operator | Aug 2018 |
| 514 | Nelson, James L. | Pettus, TX 78146 | Oil & Gas Operator | Dec 2025 |
| 515 | Neuhaus, V. F. Properties, Inc. | Palmhurst, TX 78573 | Oil & Gas Operator | Dec 2022 |
| 516 | New Horizon Investments LTD. | George West, TX 78022 | Oil & Gas Operator | Dec 2025 |
| 517 | New Voyage Enterprises LLC | San Antonio, TX 78278 | Oil Operator | Dec 2025 |
| 518 | Newfield Exploration Company | The Woodlands, TX 77380 | Oil & Gas Operator | Jun 2017 |
| 519 | Newman Operating Company | Freer, TX 78357 | Oil & Gas Operator | Jun 2021 |
| 520 | Noble Energy Inc | Midland, TX 79706 | Oil & Gas Operator | Dec 2025 |
| 521 | Nordan Trust, The | San Antonio, TX 78205 | Oil & Gas Operator | Nov 2003 |
| 522 | Nordstrand Engineering Inc | Houston, TX 77019 | Oil & Gas Operator | Dec 2025 |
| 523 | Norgas Energy | Lakehills, TX 78063 | Oil & Gas Operator | Dec 2025 |
| 524 | Nueces Reserves, Inc. | Houston, TX 77019 | Oil & Gas Operator | Oct 2002 |
| 525 | Nye Exploration & Prod, L.L.C. | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Dec 2025 |
| 526 | Ocean Energy Inc | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 527 | Oil Management Corporation | Dallas, TX 75206 | Oil & Gas Operator | Apr 2022 |
| 528 | Oilton Resources, Inc. | Laredo, TX 78041 | Oil & Gas Operator | Dec 2025 |
| 529 | Olsen Energy Inc. | Boerne, TX 78006 | Oil & Gas Operator | Dec 2025 |
| 530 | Origin Production Company, Inc. | New Braunfels, TX 78132 | Oil & Gas Operator | Dec 2025 |
| 531 | Origin Production Group LLC | Luling, TX 78648 | Oil Operator | Dec 2025 |
| 532 | Orion Oil & Gas, LLC | Houston, TX 77042 | Oil & Gas Operator | Oct 2007 |
| 533 | Orx Resources, L.L.C. | Houston, TX 77067 | Oil & Gas Operator | Dec 2025 |
| 534 | Oso Exploration Co. | San Antonio, TX 78217 | Oil & Gas Operator | Jul 2011 |
| 535 | Osr Oil & Gas Company | Victoria, TX 77902 | Oil & Gas Operator | Jul 2000 |
| 536 | Osyka Oil & Gas, Inc. | Metairie, LA 70004 | Oil & Gas Operator | Dec 2025 |
| 537 | Ozzo Corporation, The | Bedford, TX 76021 | Oil Operator | Dec 2025 |
| 538 | Pace Oil And Gas Company | Austin, TX 78715 | Oil & Gas Operator | Dec 2025 |
| 539 | Paladin-Hayes, L.L.C. | Austin, TX 78746 | Oil & Gas Operator | Dec 1999 |
| 540 | Paleo Oil Company LLC | Corpus Chrsti, TX 78411 | Oil & Gas Operator | Dec 2025 |
| 541 | Paloma Operating, LLC | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Dec 2025 |
| 542 | Panola Corporation, The | Dallas, TX 75252 | Oil & Gas Operator | Sep 2002 |
| 543 | Parker & Parsley Development Co. | Midland, TX 79702 | Oil & Gas Operator | May 1995 |
| 544 | Parker & Parsley Development L.P | Midland, TX 79702 | Oil & Gas Operator | Oct 2007 |
| 545 | Parker & Parsley Producing LP | Midland, TX 79702 | Oil & Gas Operator | Oct 1997 |
| 546 | Patriot Operating Company, Inc. | Houston, TX 77008 | Oil & Gas Operator | Sep 2003 |
| 547 | Patterson Energy Corporation | Dallas, TX 75367 | Oil & Gas Operator | Dec 2025 |
| 548 | Pearl, Bill H. Productions, Inc. | Corpus Chrsti, TX 78460 | Oil & Gas Operator | Dec 2025 |
| 549 | Pedeco, Inc. | Casper, WY 82601 | Oil & Gas Operator | Mar 2008 |
| 550 | Pegasus Operating, Inc. | Coldspring, TX 77331 | Oil & Gas Operator | Dec 2025 |
| 551 | Pennzoil Exploration & Production Co. | Carthage, TX 75633 | Oil & Gas Operator | Mar 2008 |
| 552 | Peoples Energy Prod.-TX, L.P. | Houston, TX 77002 | Oil & Gas Operator | Sep 2007 |
| 553 | Perez, H. F. | Alice, TX 78332 | Oil & Gas Operator | May 2023 |
| 554 | Perlman,I.H.Oil & Gas Properties | Houston, TX 77056 | Oil & Gas Operator | Mar 2008 |
| 555 | Petra Oleum Corp. | Midland, TX 79702 | Oil & Gas Operator | Dec 2025 |
| 556 | Petrogas Operating Corporation | Garland, TX 75043 | Oil Operator | Feb 2010 |
| 557 | Petrohawk Operating Company | Houston, TX 77056 | Oil & Gas Operator | Oct 2021 |
| 558 | Petroleum Capital, L.C. | Dallas, TX 75367 | Oil & Gas Operator | Dec 2025 |
| 559 | Petroleum Management, Inc. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Dec 2025 |
| 560 | Petromining, Inc. | Plano, TX 75026 | Oil & Gas Operator | Dec 2025 |
| 561 | PG&E Resources Company | Houston, TX 77042 | Oil & Gas Operator | May 1995 |
| 562 | PH Exploration, Inc. | Houston, TX 77008 | Oil & Gas Operator | Nov 2001 |
| 563 | Phillips Energy, Inc. | Shreveport, LA 71101 | Oil & Gas Operator | Dec 2018 |
| 564 | Phillips Petroleum Company | Houston, TX 77251 | Oil & Gas Operator | Mar 2013 |
| 565 | Pickens Company, Inc., The | Dallas, TX 75225 | Oil & Gas Operator | Jan 2025 |
| 566 | Pierco Energy Corp. | Dallas, TX 75231 | Oil & Gas Operator | Dec 2025 |
| 567 | Pintex Operating Inc. | Corpus Chrsti, TX 78478 | Oil & Gas Operator | Feb 2005 |
| 568 | Pioneer Natural Res. USA, Inc. | Spring, TX 77389 | Oil & Gas Operator | Dec 2025 |
| 569 | Pioneer Resources Producing, L.P | Irving, TX 75039 | Oil & Gas Operator | Feb 2001 |
| 570 | Plains Marketing, LP | Cushing, OK 74023 | Oil Operator | Jan 2012 |
| 571 | Plantation Operating Co., Inc. | Holliday, TX 76366 | Oil & Gas Operator | Dec 2025 |
| 572 | Poff, H. Bryan | Fort Worth, TX 76103 | Oil & Gas Operator | Mar 2008 |
| 573 | Pogo Producing Company | Houston, TX 77002 | Oil & Gas Operator | Jan 2008 |
| 574 | Precio Energy, LLC | Beaumont, TX 77726 | Oil & Gas Operator | Dec 2025 |
| 575 | Presidio Exploration, Inc. | Englewood, CO 80155 | Oil & Gas Operator | May 1999 |
| 576 | Price Drilling & Exploration Co. | Benavides, TX 78341 | Oil & Gas Operator | Jul 2013 |
| 577 | Pride Exploration, Inc. | Shreveport, LA 71101 | Oil & Gas Operator | Jul 2015 |
| 578 | Prime Operating Company | Houston, TX 77024 | Oil & Gas Operator | Dec 2025 |
| 579 | Prize Operating Company | Grapevine, TX 76051 | Oil & Gas Operator | Aug 2016 |
| 580 | Production Resources, Inc. | Castroville, TX 78009 | Oil & Gas Operator | Dec 2025 |
| 581 | Progas Operating, Inc | Red Rock, TX 78662 | Oil & Gas Operator | Dec 2025 |
| 582 | Progas Properties, Inc. | New Braunfels, TX 78132 | Oil & Gas Operator | Dec 2025 |
| 583 | Proline Energy Resources Inc | Sugar Land, TX 77479 | Oil & Gas Operator | Dec 2025 |
| 584 | Proton Energy, L.L.C. | Houston, TX 77002 | Oil & Gas Operator | Jun 2005 |
| 585 | Providence Oil Prod. | Freer, TX 78357 | Oil & Gas Operator | Dec 2025 |
| 586 | Pyramid Energy Inc | San Antonio, TX 78216 | Oil & Gas Operator | Feb 2012 |
| 587 | QNK Energy,Inc. | Alice, TX 78333 | Oil & Gas Operator | Aug 2016 |
| 588 | Quinn, Karen | Round Rock, TX 78681 | Oil Operator | Sep 2018 |
| 589 | Quintana Pet. Corp. | Refugio, TX 78377 | Oil & Gas Operator | Dec 2000 |
| 590 | R-A-R Interests | San Antonio, TX 78209 | Oil & Gas Operator | Feb 2003 |
| 591 | R.C.I. Energy | Alice, TX 78333 | Oil & Gas Operator | Dec 2025 |
| 592 | Ragars Oil & Gas Co. | Austin, TX 78746 | Oil & Gas Operator | Dec 2025 |
| 593 | Ram Operating Company, Inc. | Houston, TX 77002 | Oil & Gas Operator | Sep 2012 |
| 594 | Range Production Company | Fort Worth, TX 76102 | Oil & Gas Operator | Sep 2021 |
| 595 | Ranger Oil Company | Canada, 00100 | Oil & Gas Operator | Sep 2001 |
| 596 | Rattlesnake Operating Co, LLC | Plntersville, TX 77363 | Oil & Gas Operator | Dec 2025 |
| 597 | Redman Operating Company | Houston, TX 77042 | Oil & Gas Operator | May 2008 |
| 598 | Redwood Operating, Inc. | Houston, TX 77058 | Oil & Gas Operator | Dec 2025 |
| 599 | Regal Petroleum Services | Euless, TX 76039 | Oil & Gas Operator | Aug 2002 |
| 600 | Reichmann Petroleum Corp. | Grapevine, TX 76051 | Oil & Gas Operator | Dec 2025 |