| 401 | Killam Oil Company | Laredo, TX 78042 | Oil & Gas Operator | Mar 1994 |
| 402 | Kinder Morgan Production Co LP | Midland, TX 79701 | Oil & Gas Operator | Jul 2007 |
| 403 | Kinder Morgan Tejas Pipeline LLC | Houston, TX 77002 | Oil & Gas Operator | Feb 2026 |
| 404 | King Operating Corporation | Fort Worth, TX 76147 | Oil & Gas Operator | Feb 2026 |
| 405 | Kosarek, Charlie | San Antonio, TX 78213 | Oil & Gas Operator | Oct 2006 |
| 406 | KP Exploration, Inc. | Houston, TX 77002 | Oil & Gas Operator | Apr 1997 |
| 407 | Kriken Oil & Gas | Corpus Chrsti, TX 78426 | Oil & Gas Operator | Jul 2005 |
| 408 | L & F Drilling Co., Inc. (1) | Corpus Chrsti, TX 78479 | Oil & Gas Operator | Feb 2026 |
| 409 | L.L. Oil Company | Freer, TX 78357 | Oil & Gas Operator | Feb 2026 |
| 410 | L.T.D. Explorations Inc. | Alice, TX 78333 | Oil & Gas Operator | Feb 2026 |
| 411 | Lakeshore Operating, LLC | Wichita, KS 67203 | Oil & Gas Operator | Feb 2026 |
| 412 | Lance Exploration Company | Fort Worth, TX 76102 | Oil & Gas Operator | Jul 1994 |
| 413 | Lario Oil & Gas Company | Odessa, TX 79762 | Oil & Gas Operator | Feb 2026 |
| 414 | Laroca Resources, LTD | Austin, TX 78709 | Oil & Gas Operator | Feb 2026 |
| 415 | Laughlin, W. M. Estate | Premont, TX 78375 | Oil & Gas Operator | Jun 2003 |
| 416 | Layton Energy Inc. | Houston, TX 77027 | Oil & Gas Operator | Feb 2026 |
| 417 | Legacy Reserves Operating LP | Denver, CO 80201 | Oil & Gas Operator | Feb 2026 |
| 418 | Legend Natural Gas III, LP | Houston, TX 77094 | Oil & Gas Operator | Feb 2015 |
| 419 | LGDC Corporation | Shreveport, LA 71101 | Oil & Gas Operator | Feb 2026 |
| 420 | Lighthouse Exploration, Inc. | Corpus Chrsti, TX 78473 | Oil & Gas Operator | Jul 2007 |
| 421 | Lighthouse Operating, Inc. | Corpus Chrsti, TX 78410 | Oil & Gas Operator | Jun 2021 |
| 422 | Linn Operating, Inc. | Houston, TX 77002 | Oil & Gas Operator | May 2017 |
| 423 | Linn Operating, LLC | Houston, TX 77002 | Oil & Gas Operator | Jan 2019 |
| 424 | Live Oak Gas Company | Dallas, TX 75251 | Oil & Gas Operator | Feb 2026 |
| 425 | Live Oak Op & Production, L.L.C. | Austin, TX 78759 | Oil & Gas Operator | Nov 2011 |
| 426 | Live Oak Reserves, Inc. | Houston, TX 77019 | Oil & Gas Operator | Feb 2026 |
| 427 | Live Oak/Operations, Inc. | Houston, TX 77019 | Gas Operator | Jul 2011 |
| 428 | LMP Exploration Operating, LLC | Corpus Chrsti, TX 78477 | Oil & Gas Operator | Feb 2008 |
| 429 | LMP Petroleum, Inc. | Corpus Chrsti, TX 78477 | Oil & Gas Operator | Jan 2010 |
| 430 | Lobo Energy, Inc. | Laredo, TX 78044 | Oil & Gas Operator | Nov 1996 |
| 431 | Lobo Operating, Inc. | Houston, TX 77077 | Oil & Gas Operator | Dec 2024 |
| 432 | Lobo Resources, LTD. | Houston, TX 77077 | Oil & Gas Operator | Apr 1994 |
| 433 | Loin Energy Corporation | La Grange, TX 78945 | Oil & Gas Operator | Feb 2026 |
| 434 | Lomak Production Company | Fort Worth, TX 76102 | Oil & Gas Operator | Aug 1998 |
| 435 | Lorac, Inc. | Dallas, TX 75252 | Oil & Gas Operator | Feb 2026 |
| 436 | Los Hijos De Sanchez J LLC | Beeville, TX 78102 | Oil Operator | Feb 2026 |
| 437 | Louisiana Land & Exploration Co. | Houston, TX 77210 | Oil & Gas Operator | Sep 2013 |
| 438 | LTS Oil & Gas | Lubbock, TX 79424 | Oil & Gas Operator | Feb 2026 |
| 439 | LTS Oil & Gas A | Lubbock, TX 79424 | Oil & Gas Operator | Feb 2026 |
| 440 | Luca Resources Group, LLC | Houston, TX 77002 | Oil & Gas Operator | Feb 2026 |
| 441 | Lucros International Corporation | Van Buren, AR 72956 | Oil & Gas Operator | Feb 2026 |
| 442 | Luling O&G LLC | Cibolo, TX 78108 | Oil & Gas Operator | Feb 2026 |
| 443 | Lundells, Inc. | Freer, TX 78357 | Oil & Gas Operator | Jan 1995 |
| 444 | Luttrell, T. Bruce Oil & Gas Opr | Freer, TX 78357 | Oil & Gas Operator | Mar 2008 |
| 445 | Lyco Energy Corporation | Dallas, TX 75206 | Oil & Gas Operator | Jun 2015 |
| 446 | Lynd, J. L., Inc. | Austin, TX 78716 | Oil & Gas Operator | Sep 2009 |
| 447 | Lynx Energy Company, Inc. | Dallas, TX 75201 | Oil & Gas Operator | Mar 2008 |
| 448 | Lynx Operating Co., Inc. | Dallas, TX 75206 | Oil & Gas Operator | Feb 2026 |
| 449 | M IV Ops., Inc. | San Antonio, TX 78217 | Oil & Gas Operator | Mar 1998 |
| 450 | M. J. G., Inc. | Alice, TX 78333 | Oil & Gas Operator | Jul 2010 |
| 451 | M. M. Miller & Sons, LTD. | Alice, TX 78333 | Oil & Gas Operator | Jan 2023 |
| 452 | Maggert Energy Corp. | Spring, TX 77387 | Gas Operator | Jun 1998 |
| 453 | Magna Oil & Gas Corporation | Irving, TX 75017 | Oil & Gas Operator | Feb 2016 |
| 454 | Magnum Engineering Company | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Feb 2026 |
| 455 | Magnum Producing, LP | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Feb 2026 |
| 456 | Manley, John D. III, Oper., Inc | Corpus Chrsti, TX 78404 | Oil & Gas Operator | Feb 2016 |
| 457 | Manti Exploration Operating LLC | Corpus Chrsti, TX 78403 | Oil & Gas Operator | Feb 2015 |
| 458 | Manti Operating Company | Covington, LA 70435 | Oil & Gas Operator | Feb 2026 |
| 459 | Mantle Oil & Gas, LLC | Friendswood, TX 77546 | Oil & Gas Operator | Feb 2026 |
| 460 | Marathon Oil Company | Houston, TX 77252 | Oil & Gas Operator | Dec 2025 |
| 461 | Marco Polo Exploration, Inc. | Rosenberg, TX 77471 | Oil & Gas Operator | Dec 1993 |
| 462 | Mariner Energy, Inc. | Houston, TX 77042 | Oil & Gas Operator | Nov 2010 |
| 463 | Mark IV Energy | San Antonio, TX 78213 | Oil & Gas Operator | Apr 1993 |
| 464 | Marquee Corporation | Houston, TX 77024 | Oil & Gas Operator | Feb 2026 |
| 465 | Marshall Energy, Inc. | Dallas, TX 75243 | Oil & Gas Operator | May 1997 |
| 466 | Martin Oil & Gas | Freer, TX 78357 | Oil & Gas Operator | Oct 2025 |
| 467 | Martin Oil & Gas Inc. | Freer, TX 78357 | Oil & Gas Operator | Feb 2026 |
| 468 | Martineau Petroleum, Inc. | Dallas, TX 75206 | Oil & Gas Operator | Jan 2025 |
| 469 | Marwell Petroleum LTD Partnrship | Houston, TX 77027 | Oil & Gas Operator | Feb 2026 |
| 470 | Marwell Petroleum, Inc. | Houston, TX 77057 | Oil & Gas Operator | Apr 2006 |
| 471 | Mayfield Engineering Service | Tulsa, OK 74104 | Oil & Gas Operator | Feb 2026 |
| 472 | Maynard Oil Co. | Denver, CO 80202 | Oil & Gas Operator | Sep 2004 |
| 473 | Mayo Oil Co. | San Antonio, TX 78209 | Oil & Gas Operator | Feb 2019 |
| 474 | McAnear Oil & Gas | Freer, TX 78357 | Oil & Gas Operator | Dec 2002 |
| 475 | McBee Company, The | Dallas, TX 75219 | Oil & Gas Operator | Dec 1997 |
| 476 | McCutchin, Jerry | Dallas, TX 75380 | Oil & Gas Operator | Mar 2008 |
| 477 | McDonald & Johnson Resources,LLC | Cypress, TX 77429 | Oil & Gas Operator | Dec 2010 |
| 478 | McGowan Working Partners | Jackson, MS 39296 | Oil & Gas Operator | Dec 2000 |
| 479 | McGowan Working Partners, Inc. | Jackson, MS 39296 | Oil & Gas Operator | Feb 2026 |
| 480 | McGuffin, Joe Jr. | Christoval, TX 76935 | Oil & Gas Operator | Feb 2026 |
| 481 | McGuffin, Joe S. Inc. | Mathis, TX 78368 | Gas Operator | Feb 2026 |
| 482 | McQueen Ed & Company Inc | Lindsey, OK 73052 | Oil & Gas Operator | Apr 2014 |
| 483 | McRae & Henry LTD | Golden, CO 80401 | Oil & Gas Operator | May 2022 |
| 484 | McRae Exploration & Prod., Inc. | Houston, TX 77064 | Oil & Gas Operator | Feb 2017 |
| 485 | McRae, Nathan Rathburn | Hebbronville, TX 78361 | Oil & Gas Operator | Apr 1994 |
| 486 | Memorial Exploration Company | Saint Louis, MO 63105 | Oil & Gas Operator | Aug 1996 |
| 487 | Merit Energy Company | Dallas, TX 75240 | Oil & Gas Operator | Feb 2026 |
| 488 | Metano Energy, LP | San Antonio, TX 78216 | Oil & Gas Operator | Aug 2008 |
| 489 | MHM Pipeline Co., Inc. | Dallas, TX 75252 | Oil & Gas Operator | Feb 2026 |
| 490 | Michael Petroleum Corporation | Houston, TX 77040 | Oil & Gas Operator | Dec 2001 |
| 491 | Micro Operating, Inc. | Tomball, TX 77375 | Oil & Gas Operator | Feb 2026 |
| 492 | Midstates Corporation | San Antonio, TX 78217 | Oil & Gas Operator | Feb 2026 |
| 493 | Midway Drilling Co. | Richmond, TX 77469 | Oil & Gas Operator | Feb 2026 |
| 494 | Milagro Exploration, LLC | Houston, TX 77010 | Oil & Gas Operator | Aug 2018 |
| 495 | Miller, M. M. & Sons | Alice, TX 78333 | Oil & Gas Operator | Apr 2007 |
| 496 | Miller, W. C. Operating Company | San Antonio, TX 78209 | Oil & Gas Operator | Feb 2026 |
| 497 | Miramar Petroleum, Inc. | Corpus Chrsti, TX 78463 | Oil & Gas Operator | Sep 2017 |
| 498 | Mirando Crude Oil Co. | Luling, TX 78648 | Oil & Gas Operator | Jul 1994 |
| 499 | Mirando Resource, L.L.C. | Freer, TX 78357 | Oil & Gas Operator | Feb 2026 |
| 500 | Mitchell Energy Corp | Houston, TX 77002 | Oil & Gas Operator | Aug 2013 |