| 301 | K-B Oil Company | Dallas, TX 75243 | Oil & Gas Operator | Dec 2020 |
| 302 | Kaiser-Francis Oil Company | Tulsa, OK 74121 | Oil & Gas Operator | May 2025 |
| 303 | Kaler Energy Corp. | Boerne, TX 78006 | Oil & Gas Operator | May 2025 |
| 304 | KCS Medallion Resources, Inc. | Tulsa, OK 74136 | Oil & Gas Operator | Nov 2018 |
| 305 | KCS Resources, Inc. | Houston, TX 77002 | Oil & Gas Operator | Feb 2009 |
| 306 | KD Energy, LLC | Houston, TX 77056 | Oil & Gas Operator | May 2025 |
| 307 | Kebo Oil & Gas, Inc. | Portland, TX 78374 | Oil & Gas Operator | May 2025 |
| 308 | Kelley Oil Corporation | Houston, TX 77002 | Oil & Gas Operator | Jan 2002 |
| 309 | Ken Petroleum Corporation | Dallas, TX 75206 | Oil & Gas Operator | Feb 2019 |
| 310 | Kerr-McGee Oil & Gas Onshore LP | Houston, TX 77046 | Oil & Gas Operator | May 2025 |
| 311 | Killam Oil Co., LTD. | Laredo, TX 78042 | Oil & Gas Operator | May 2025 |
| 312 | Killam Oil Company | Laredo, TX 78042 | Oil & Gas Operator | Mar 1994 |
| 313 | Kling, Inc. | Corpus Chrsti, TX 78473 | Oil & Gas Operator | Dec 2000 |
| 314 | Klotzman, M. S. Exploration Co. | Victoria, TX 77903 | Oil & Gas Operator | May 2025 |
| 315 | Kram Energy | Corpus Chrsti, TX 78404 | Oil & Gas Operator | May 2025 |
| 316 | Kriken Oil & Gas | Corpus Chrsti, TX 78426 | Oil & Gas Operator | Jul 2005 |
| 317 | Kriken Oil & Gas, Inc. | Corpus Chrsti, TX 78426 | Oil & Gas Operator | May 2025 |
| 318 | Kristen Oil And Gas, Inc. | Edna, TX 77957 | Oil & Gas Operator | May 2025 |
| 319 | KWS Oil & Gas, LLC | El Campo, TX 77437 | Oil & Gas Operator | May 2025 |
| 320 | L & F Drilling Co., Inc. (1) | Corpus Chrsti, TX 78479 | Oil & Gas Operator | May 2025 |
| 321 | L.T.D. Explorations Inc. | Alice, TX 78333 | Oil & Gas Operator | May 2025 |
| 322 | Lagarto Company, The | Fredericksbrg, TX 78624 | Oil & Gas Operator | Apr 1995 |
| 323 | Langham Petroleum Expl. Corp. | Houston, TX 77056 | Oil & Gas Operator | Dec 2009 |
| 324 | Layton Energy Inc. | Houston, TX 77027 | Oil & Gas Operator | May 2025 |
| 325 | Leach, D.L.,Jr. | Edna, TX 77957 | Gas Operator | Oct 2007 |
| 326 | Legado Gulf Coast, LLC | The Woodlands, TX 77380 | Oil & Gas Operator | Apr 2010 |
| 327 | Liberty Production Co | Houston, TX 77002 | Oil & Gas Operator | Nov 1994 |
| 328 | Lindenmuth & Associates Inc | Austin, TX 78703 | Oil & Gas Operator | Aug 2024 |
| 329 | LNR Energy Corp | Houston, TX 77002 | Oil & Gas Operator | Mar 2008 |
| 330 | Lodi Drilling & Service Co. | Corpus Chrsti, TX 78426 | Oil & Gas Operator | May 2025 |
| 331 | Lodi Operating Company LLC | Corpus Chrsti, TX 78426 | Oil & Gas Operator | May 2025 |
| 332 | Lower Colorado River Authority | Bastrop, TX 78602 | Oil & Gas Operator | May 2025 |
| 333 | LTX Productions, Inc. | Houston, TX 77095 | Oil & Gas Operator | Jul 2008 |
| 334 | Lundberg Operating Corporation | Dallas, TX 75225 | Oil & Gas Operator | Oct 2002 |
| 335 | Lynbrook Oil Company | Houston, TX 77057 | Oil & Gas Operator | Dec 2008 |
| 336 | Lytle Creek Operating, Inc. | Abilene, TX 79606 | Oil & Gas Operator | May 2025 |
| 337 | M-B Operating Co., Inc. | Rowlett, TX 75030 | Oil & Gas Operator | May 2025 |
| 338 | M. J. G., Inc. | Alice, TX 78333 | Oil & Gas Operator | Jul 2010 |
| 339 | Magnum Engineering Company | Corpus Chrsti, TX 78401 | Oil & Gas Operator | May 2025 |
| 340 | Magnum Producing & Operating Co. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Jan 2004 |
| 341 | Magnum Producing, LP | Corpus Chrsti, TX 78401 | Oil & Gas Operator | May 2025 |
| 342 | Mamerow Energy Corp | Ganado, TX 77962 | Oil & Gas Operator | May 2025 |
| 343 | Manti Operating Company | Covington, LA 70435 | Oil & Gas Operator | May 2025 |
| 344 | Maralo, Inc. | Midland, TX 79702 | Oil & Gas Operator | Dec 1998 |
| 345 | Marquee Corporation | Houston, TX 77024 | Oil & Gas Operator | May 2025 |
| 346 | Marwell Petroleum, Inc. | Houston, TX 77057 | Oil & Gas Operator | Apr 2006 |
| 347 | Mass Energy, Inc | Houston, TX 77056 | Oil & Gas Operator | Mar 2008 |
| 348 | Mayne & Mertz, Inc. | Midland, TX 79702 | Oil & Gas Operator | Mar 2013 |
| 349 | McGhee Exploration And Prod. Co. | Houston, TX 77019 | Oil & Gas Operator | Feb 2003 |
| 350 | McGowan Working Partners | Jackson, MS 39296 | Oil & Gas Operator | Dec 2000 |
| 351 | McGowan Working Partners, Inc. | Jackson, MS 39296 | Oil & Gas Operator | May 2025 |
| 352 | McLeod, George L. Inc. | Houston, TX 77079 | Oil & Gas Operator | Sep 2002 |
| 353 | Medallion Oil Company | Houston, TX 77251 | Oil & Gas Operator | Jan 2012 |
| 354 | Meridian Oil Inc. | Houston, TX 77210 | Oil & Gas Operator | Aug 1996 |
| 355 | Meridian Oil Production Inc. | Houston, TX 77210 | Oil & Gas Operator | Aug 2024 |
| 356 | Mexco Energy Corporation | Midland, TX 79702 | Oil & Gas Operator | Feb 2020 |
| 357 | Midstates Corporation | San Antonio, TX 78217 | Oil & Gas Operator | May 2025 |
| 358 | Milagro Exploration, LLC | Houston, TX 77010 | Oil & Gas Operator | Aug 2018 |
| 359 | Miller, W. C. Operating Company | San Antonio, TX 78209 | Oil & Gas Operator | May 2025 |
| 360 | Miner, R. C. Inc. | Corpus Chrsti, TX 78413 | Oil & Gas Operator | Apr 2002 |
| 361 | Miner, R. C. Oil, Inc. | MC Queeney, TX 78123 | Oil & Gas Operator | May 2025 |
| 362 | Miramar Petroleum, Inc. | Corpus Chrsti, TX 78463 | Oil & Gas Operator | Sep 2017 |
| 363 | Mission River Systems, Inc. | Corpus Chrsti, TX 78473 | Oil & Gas Operator | May 2025 |
| 364 | Mitchell Energy Corp | Houston, TX 77002 | Oil & Gas Operator | Aug 2013 |
| 365 | Mobil Oil Corporation | Houston, TX 77210 | Oil & Gas Operator | Jun 2016 |
| 366 | Mobil Producing TX. & N.M. Inc. | Spring, TX 77389 | Oil & Gas Operator | May 2025 |
| 367 | Modern Exploration, Inc. | Sherman, TX 75090 | Oil & Gas Operator | May 2025 |
| 368 | Mogul Energy International, Inc. | Houston, TX 77042 | Oil & Gas Operator | Oct 2017 |
| 369 | Moose Oil & Gas Co. | Houston, TX 77002 | Oil & Gas Operator | Feb 2000 |
| 370 | Mortimer Exploration Company | San Antonio, TX 78209 | Oil & Gas Operator | Sep 2003 |
| 371 | Mortimer Production Company | San Antonio, TX 78209 | Oil & Gas Operator | May 2025 |
| 372 | Mowata Oil Company | Victoria, TX 77903 | Oil & Gas Operator | Oct 1996 |
| 373 | N S P Operating Group LLC | El Campo, TX 77437 | Oil & Gas Operator | Aug 2021 |
| 374 | Nadsoilco LLC | Chicago, IL 60606 | Oil & Gas Operator | May 2025 |
| 375 | Neumin Production Company | Point Comfort, TX 77978 | Oil & Gas Operator | May 2025 |
| 376 | New Century Exploration, Inc. | Spring, TX 77379 | Oil & Gas Operator | May 2025 |
| 377 | New Horizon Investments LTD. | George West, TX 78022 | Oil & Gas Operator | May 2025 |
| 378 | New London Oil Inc. | Houston, TX 77253 | Oil & Gas Operator | Aug 2002 |
| 379 | New Source Oil & Gas, LLC | Victoria, TX 77903 | Oil & Gas Operator | May 2025 |
| 380 | Nordstrand Engineering Inc | Houston, TX 77019 | Oil & Gas Operator | May 2025 |
| 381 | North Central Oil Corp | Houston, TX 77252 | Oil & Gas Operator | Dec 2005 |
| 382 | North Lake Resources LLC | Oklahoma City, OK 73132 | Oil & Gas Operator | May 2025 |
| 383 | North Shore Energy, L.L.C. | Austin, TX 78750 | Oil & Gas Operator | May 2025 |
| 384 | Nueces Petroleum Corporation | Sugar Land, TX 77496 | Oil Operator | May 2025 |
| 385 | O'Connor & Hewitt, LTD. | Victoria, TX 77901 | Oil & Gas Operator | Jun 1998 |
| 386 | O'Tool Oil & Gas, LLC | Dallas, TX 75219 | Oil & Gas Operator | May 2025 |
| 387 | Oblaen Resources LLC | Wallis, TX 77485 | Oil & Gas Operator | May 2025 |
| 388 | Occidental Energy Company, Inc. | Houston, TX 77282 | Oil & Gas Operator | Jul 2021 |
| 389 | Odegard Energy, Inc. | Houston, TX 77024 | Oil & Gas Operator | Jul 2020 |
| 390 | Oil Coast Corp. | S Houston, TX 77587 | Oil & Gas Operator | May 2025 |
| 391 | Oil Well Buyers Corp. | Houston, TX 77056 | Oil & Gas Operator | Dec 2024 |
| 392 | Okie Operating Company, LTD. | Tulsa, OK 74103 | Oil & Gas Operator | May 2025 |
| 393 | Oklahoma Oil Company | Dallas, TX 75206 | Oil & Gas Operator | Aug 2013 |
| 394 | Olipdp II, LLC | Lafayette, LA 70503 | Oil & Gas Operator | May 2025 |
| 395 | Olsen Energy Inc. | Boerne, TX 78006 | Oil & Gas Operator | May 2025 |
| 396 | Opal Energy, Inc. | Katy, TX 77494 | Oil & Gas Operator | Jun 2009 |
| 397 | Opex Energy, LLC | Houston, TX 77042 | Oil & Gas Operator | Mar 2008 |
| 398 | Osyka Permian, LLC | Houston, TX 77079 | Oil & Gas Operator | May 2025 |
| 399 | Outline Oil Corp. | San Antonio, TX 78217 | Oil & Gas Operator | May 2025 |
| 400 | P&B Petroleum LLC | Miami, FL 33166 | Oil & Gas Operator | May 2025 |