| 301 | Memorial Exploration Company | Saint Louis, MO 63105 | Oil & Gas Operator | Aug 1996 |
| 302 | Meridian Resource & Expl LLC,The | Houston, TX 77094 | Oil & Gas Operator | Nov 2012 |
| 303 | Merrimac Energy Corp. | Dallas, TX 75206 | Oil & Gas Operator | Aug 1999 |
| 304 | Mertz Energy LLC | Houston, TX 77098 | Oil & Gas Operator | Jan 2025 |
| 305 | Mestena, Inc. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Nov 2001 |
| 306 | Michael Petroleum Corporation | Houston, TX 77040 | Oil & Gas Operator | Dec 2001 |
| 307 | Midas Resources, Inc. | Corpus Chrsti, TX 78403 | Oil & Gas Operator | May 2025 |
| 308 | Midpar L.P. | Midland, TX 79702 | Oil & Gas Operator | Feb 1995 |
| 309 | Milagro Exploration, LLC | Houston, TX 77010 | Oil & Gas Operator | Aug 2018 |
| 310 | Miocene Oil & Gas, Inc. | Englewood, CO 80155 | Oil & Gas Operator | Jul 1998 |
| 311 | Miramar Petroleum, Inc. | Corpus Chrsti, TX 78463 | Oil & Gas Operator | Sep 2017 |
| 312 | Mission Resources Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2008 |
| 313 | Mission River Systems, Inc. | Corpus Chrsti, TX 78473 | Oil & Gas Operator | May 2025 |
| 314 | ML Resources, Inc. | Dallas, TX 75240 | Oil & Gas Operator | Mar 2008 |
| 315 | Mo-Jon, Inc. | Edroy, TX 78352 | Oil & Gas Operator | May 1999 |
| 316 | Mobil Oil Corporation | Houston, TX 77210 | Oil & Gas Operator | Jun 2016 |
| 317 | Mobil Producing TX. & N.M. Inc. | Spring, TX 77389 | Oil & Gas Operator | May 2025 |
| 318 | Modern Exploration, Inc. | Sherman, TX 75090 | Oil & Gas Operator | May 2025 |
| 319 | Mogul Energy International, Inc. | Houston, TX 77042 | Oil & Gas Operator | Oct 2017 |
| 320 | Momentum Production Corp. | Baytown, TX 77521 | Oil & Gas Operator | May 2025 |
| 321 | Mortimer Exploration Company | San Antonio, TX 78209 | Oil & Gas Operator | Sep 2003 |
| 322 | Mortimer Production Company | San Antonio, TX 78209 | Oil & Gas Operator | May 2025 |
| 323 | MPG Petroleum, Inc. | San Antonio, TX 78209 | Oil & Gas Operator | May 2025 |
| 324 | Mueller Engineering Corp. | Corpus Chrsti, TX 78476 | Oil & Gas Operator | Feb 2002 |
| 325 | Mueller Exploration, Inc. | Portland, TX 78374 | Oil & Gas Operator | May 2025 |
| 326 | Mugg, John D. Jr. | San Antonio, TX 78216 | Oil & Gas Operator | Nov 1997 |
| 327 | Mustang Oil & Gas Corporation | Wichita Falls, TX 76308 | Oil & Gas Operator | Jul 2021 |
| 328 | Nadcf Recovery Group, Inc. | Chapin, SC 29036 | Oil & Gas Operator | May 2025 |
| 329 | National Energy Group, Inc. | Dallas, TX 75206 | Oil & Gas Operator | Sep 2014 |
| 330 | Navajo Exploration, Inc. | Corpus Chrsti, TX 78410 | Oil & Gas Operator | May 2025 |
| 331 | Neumin Production Company | Point Comfort, TX 77978 | Oil & Gas Operator | May 2025 |
| 332 | New Horizon Investments LTD. | George West, TX 78022 | Oil & Gas Operator | May 2025 |
| 333 | North Central Oil Corp | Houston, TX 77252 | Oil & Gas Operator | Dec 2005 |
| 334 | North Shore Energy, L.L.C. | Austin, TX 78750 | Oil & Gas Operator | May 2025 |
| 335 | Null, W.M. Operations, Inc. | Corpus Chrsti, TX 78475 | Oil & Gas Operator | Jun 2002 |
| 336 | Nye Exploration & Prod, L.L.C. | Corpus Chrsti, TX 78401 | Oil & Gas Operator | May 2025 |
| 337 | O'Connor & Hewitt, LTD. | Victoria, TX 77901 | Oil & Gas Operator | Jun 1998 |
| 338 | Oblaen Resources LLC | Wallis, TX 77485 | Oil & Gas Operator | May 2025 |
| 339 | Occidental Energy Company, Inc. | Houston, TX 77282 | Oil & Gas Operator | Jul 2021 |
| 340 | Odegard Energy, Inc. | Houston, TX 77024 | Oil & Gas Operator | Jul 2020 |
| 341 | Oil Coast Corp. | S Houston, TX 77587 | Oil & Gas Operator | May 2025 |
| 342 | Oklahoma RB Operating Company | Midland, TX 79701 | Oil & Gas Operator | Jan 1998 |
| 343 | Oky Investments, Inc. | Edmond, OK 73013 | Oil & Gas Operator | Sep 2021 |
| 344 | Olsen Energy Inc. | Boerne, TX 78006 | Oil & Gas Operator | May 2025 |
| 345 | Omega Energy Corp. | Graham, TX 76450 | Oil & Gas Operator | May 2025 |
| 346 | Omega Energy, LLC | Corpus Chrsti, TX 78418 | Oil & Gas Operator | May 2025 |
| 347 | Orx Resources, L.L.C. | Houston, TX 77067 | Oil & Gas Operator | May 2025 |
| 348 | Osr Oil & Gas Company | Victoria, TX 77902 | Oil & Gas Operator | Jul 2000 |
| 349 | Outline Oil Corp. | San Antonio, TX 78217 | Oil & Gas Operator | May 2025 |
| 350 | Owl Creek Production Co., Inc. | Houston, TX 77027 | Oil & Gas Operator | Apr 2006 |
| 351 | Oxy USA Inc | Houston, TX 77046 | Oil & Gas Operator | May 2025 |
| 352 | Pace Oil And Gas Company | Austin, TX 78715 | Oil & Gas Operator | May 2025 |
| 353 | Pace Production Co. | San Angelo, TX 76902 | Oil & Gas Operator | May 2025 |
| 354 | Paleo Oil Company LLC | Corpus Chrsti, TX 78411 | Oil & Gas Operator | May 2025 |
| 355 | Pantera Energy Company | Amarillo, TX 79101 | Oil & Gas Operator | May 2025 |
| 356 | Par Minerals Corporation | Shreveport, LA 71101 | Oil & Gas Operator | May 2025 |
| 357 | Parker & Parsley Development L.P | Midland, TX 79702 | Oil & Gas Operator | Oct 2007 |
| 358 | Pearl, Bill H. Productions, Inc. | Corpus Chrsti, TX 78460 | Oil & Gas Operator | May 2025 |
| 359 | Pedeco, Inc. | Casper, WY 82601 | Oil & Gas Operator | Mar 2008 |
| 360 | Penn VIrginia Oil & Gas Corp | Houston, TX 77024 | Oil & Gas Operator | Dec 2023 |
| 361 | Penn VIrginia Oil & Gas, L.P. | Houston, TX 77084 | Oil & Gas Operator | Nov 2022 |
| 362 | Peoples Energy Prod.-TX, L.P. | Houston, TX 77002 | Oil & Gas Operator | Sep 2007 |
| 363 | Petro-Guard Company, Inc. | Houston, TX 77057 | Oil & Gas Operator | Nov 2014 |
| 364 | Petro-Smith Operating LLC | Houston, TX 77010 | Oil & Gas Operator | May 2025 |
| 365 | Petrodome Operating, LLC | Houston, TX 77265 | Oil & Gas Operator | Jan 2025 |
| 366 | Petrohawk Operating Company | Houston, TX 77056 | Oil & Gas Operator | Oct 2021 |
| 367 | Petroleum Management, Inc. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | May 2025 |
| 368 | Petroleum Resource Management Co | Fort Worth, TX 76107 | Oil & Gas Operator | Jan 2024 |
| 369 | PG&E Resources Company | Houston, TX 77042 | Oil & Gas Operator | May 1995 |
| 370 | Phillips Energy, Inc. | Shreveport, LA 71101 | Oil & Gas Operator | Dec 2018 |
| 371 | Pintail Production Co., Inc. | Fort Worth, TX 76132 | Oil & Gas Operator | May 2025 |
| 372 | Pintex Operating Inc. | Corpus Chrsti, TX 78478 | Oil & Gas Operator | Feb 2005 |
| 373 | Placer Oil Co. | Sugar Land, TX 77479 | Oil & Gas Operator | Apr 2008 |
| 374 | Pmo | Garland, TX 75040 | Oil & Gas Operator | Feb 2018 |
| 375 | Poco LLC | Houston, TX 77270 | Oil & Gas Operator | May 2025 |
| 376 | Powerline Energy Corporation | Arlington, TX 76015 | Oil & Gas Operator | May 2025 |
| 377 | Preferred Pipeline Corp. | Victoria, TX 77902 | Oil & Gas Operator | Apr 2025 |
| 378 | Prevail Energy, Inc | Corpus Chrsti, TX 78469 | Oil & Gas Operator | May 2025 |
| 379 | Prime Operating Company | Houston, TX 77024 | Oil & Gas Operator | May 2025 |
| 380 | Proline Energy Resources Inc | Sugar Land, TX 77479 | Oil & Gas Operator | May 2025 |
| 381 | Property Development Group, Inc. | San Antonio, TX 78212 | Oil & Gas Operator | May 2025 |
| 382 | Pullin Lease Service, Inc. | Taft, TX 78390 | Oil & Gas Operator | May 2025 |
| 383 | Puls Operating Company | Boerne, TX 78006 | Oil & Gas Operator | May 2025 |
| 384 | Puls, W. L. | Houston, TX 77084 | Oil & Gas Operator | Sep 2002 |
| 385 | Pyle Petroleum | Corpus Chrsti, TX 78473 | Oil & Gas Operator | Dec 1996 |
| 386 | Pyle Petroleum, Inc. | Tyler, TX 75703 | Oil & Gas Operator | May 2025 |
| 387 | Pyramid Energy Inc | San Antonio, TX 78216 | Oil & Gas Operator | Feb 2012 |
| 388 | Pyramid Exploration | Houston, TX 77241 | Oil & Gas Operator | Sep 1995 |
| 389 | Quintana Pet. Corp. | Refugio, TX 78377 | Oil & Gas Operator | Dec 2000 |
| 390 | Redmon Oil Company, Inc., The | Plano, TX 75023 | Oil & Gas Operator | May 2025 |
| 391 | Reh Energy, Inc. | Corpus Chrsti, TX 78413 | Oil & Gas Operator | May 2025 |
| 392 | Reichmann Petroleum Corp. | Grapevine, TX 76051 | Oil & Gas Operator | May 2025 |
| 393 | Remora Management, LLC | The Woodlands, TX 77382 | Oil & Gas Operator | May 2025 |
| 394 | Republic Resources, LLC. | San Antonio, TX 78212 | Oil & Gas Operator | May 2025 |
| 395 | Reserve Operating Corp. | Houston, TX 77040 | Oil & Gas Operator | May 2025 |
| 396 | Richman Petroleum Corp. | Grapevine, TX 76051 | Oil & Gas Operator | Jul 2006 |
| 397 | Rife Oil Properties Inc | Fort Worth, TX 76107 | Oil & Gas Operator | May 2025 |
| 398 | Riley Exploration, LLC | Blanchard, OK 73010 | Oil & Gas Operator | May 2025 |
| 399 | Rincon Petroleum Corporation | Corpus Chrsti, TX 78427 | Oil & Gas Operator | May 2025 |
| 400 | Rio Exploration Company | San Antonio, TX 78209 | Gas Operator | Dec 2005 |