| 401 | Rig Iron, Inc. | | Oil & Gas Operator | Mar 1991 |
| 402 | Rio Bravo Expl. & Prod. Co. | Houston, TX 77055 | Oil & Gas Operator | Apr 2020 |
| 403 | Rio Bravo Oil Company | The Woodlands, TX 77381 | Oil & Gas Operator | Feb 2002 |
| 404 | Riseden, LTD | | Oil & Gas Operator | Nov 1989 |
| 405 | RLM Energy Company Inc. | Monroe, LA 71201 | Oil & Gas Operator | Mar 2008 |
| 406 | Robert P. Artzberger | | Oil & Gas Operator | Dec 1979 |
| 407 | Rockleigh K. Thurman | | Oil & Gas Operator | Jul 2024 |
| 408 | Rosewood Resources, Inc. | Dallas, TX 75201 | Oil & Gas Operator | Dec 2024 |
| 409 | Rutherford Oil Corporation | Houston, TX 77046 | Oil & Gas Operator | Jun 2019 |
| 410 | S & J Operating Company | Wichita Falls, TX 76301 | Oil & Gas Operator | Mar 2015 |
| 411 | S & S Oil Company | Electra, TX 76360 | Oil & Gas Operator | Dec 2024 |
| 412 | S&B Petroleum Corporation | | Oil & Gas Operator | Jun 1994 |
| 413 | S2 Energy Operating LLC | | Oil & Gas Operator | May 2023 |
| 414 | Sackett Oil Company | | Oil & Gas Operator | Sep 1995 |
| 415 | Samedan Oil Corporation | Houston, TX 77067 | Oil & Gas Operator | Dec 2019 |
| 416 | Samson Contour Energy E&P, LLC | Tulsa, OK 74103 | Oil & Gas Operator | Sep 2017 |
| 417 | Samson Exploration LLC | Tulsa, OK 74101 | Oil & Gas Operator | Oct 2024 |
| 418 | Samson Resources Company | Tulsa, OK 74103 | Oil & Gas Operator | Aug 2024 |
| 419 | Sandpoint Energy Partners LLC | | Oil Operator | Jul 2024 |
| 420 | Sandridge Exploration And Production LLC | Oklahoma City, OK 73104 | Oil & Gas Operator | Dec 2024 |
| 421 | Secondary Recovery, Inc. | | Oil & Gas Operator | Dec 1991 |
| 422 | Semo, Inc. | | Oil & Gas Operator | Feb 2002 |
| 423 | Senior Drilling & Expl Co Inc. | | Oil & Gas Operator | Apr 1993 |
| 424 | Setex Oil And Gas Company | Houston, TX 77002 | Oil & Gas Operator | Feb 2012 |
| 425 | Shelf Energy, LLC | | Oil & Gas Operator | Jun 2024 |
| 426 | Shell Oil Company | Houston, TX 77210 | Oil & Gas Operator | Apr 2015 |
| 427 | Shell Western E&P Inc. | Houston, TX 77001 | Oil & Gas Operator | May 2011 |
| 428 | Shocker Energy, Inc. | | Oil & Gas Operator | Oct 1992 |
| 429 | Shoreline Southeast LLC | | Oil & Gas Operator | Jun 2017 |
| 430 | Sierra Production Company | | Oil & Gas Operator | May 1986 |
| 431 | Singer Fleischaker Oil Op. Co. | Oklahoma City, OK 73102 | Oil & Gas Operator | Apr 2002 |
| 432 | Singer-Fleischaker,Dillon | | Oil & Gas Operator | Aug 1979 |
| 433 | Sklar & Phillips Oil Co. | Shreveport, LA 71101 | Oil & Gas Operator | Dec 2000 |
| 434 | Smith Production Co. | Wichita Falls, TX 76308 | Oil & Gas Operator | Dec 2024 |
| 435 | Sohio Petroleum Co. | Casper, WY 82602 | Oil & Gas Operator | Apr 1986 |
| 436 | Source Petroleum Inc. | San Antonio, TX 78265 | Oil & Gas Operator | Dec 2024 |
| 437 | Southern G Holdings, LLC | Houston, TX 77002 | Oil & Gas Operator | Dec 2007 |
| 438 | Southern Operating, Inc. | | Oil Operator | Dec 2000 |
| 439 | Spartan Petroleum Corporation | Houston, TX 77079 | Oil & Gas Operator | Oct 1987 |
| 440 | St. Mary Operating Company | Denver, CO 80203 | Oil & Gas Operator | Mar 2019 |
| 441 | Stratco Operating Co Inc | Austin, TX 78701 | Oil & Gas Operator | Dec 2024 |
| 442 | Striper Oil, Inc. | Dallas, TX 75379 | Oil & Gas Operator | Apr 2002 |
| 443 | Subsurface Resources Inc | Logan, UT 84321 | Oil & Gas Operator | Aug 1990 |
| 444 | Summit Energy, Inc. | Littleton, CO 80127 | Oil & Gas Operator | Aug 2013 |
| 445 | Sun Exploration-Production Co. | | Oil & Gas Operator | Jan 1990 |
| 446 | Sun Texas Company | | Oil & Gas Operator | Jun 1981 |
| 447 | Sunland Production Company, Inc. | Shreveport, LA 71101 | Oil & Gas Operator | Sep 2024 |
| 448 | Superior Oil Co. | Denver, CO 80217-5444 | Oil & Gas Operator | Feb 2001 |
| 449 | Sutton Joint Account | | Oil Operator | Mar 1988 |
| 450 | Swift Energy Company | Houston, TX 77060 | Oil & Gas Operator | Mar 2021 |
| 451 | Synergy Oil & Gas, Inc. | Houston, TX 77024 | Oil & Gas Operator | Nov 2019 |
| 452 | T & B Resources | | Oil & Gas Operator | Jul 1990 |
| 453 | Tabco Exploration Inc. | New Orleans, LA 70131 | Oil & Gas Operator | Dec 1998 |
| 454 | Tabco Producing Co. | | Oil & Gas Operator | Jan 1998 |
| 455 | Tadlock Properites | | Oil & Gas Operator | Jan 1994 |
| 456 | Targa Midstream Services LLC | Houston, TX 77002 | Oil Operator | Mar 2023 |
| 457 | Teal Petroleum Co. | | Oil & Gas Operator | Sep 1978 |
| 458 | Tee Operating Company | | Oil & Gas Operator | Jun 1989 |
| 459 | Telico Minerals, L.L.C. | | Oil & Gas Operator | Oct 2019 |
| 460 | Tenneco Oil Company | Oklahoma City, OK 73125 | Oil & Gas Operator | Aug 2024 |
| 461 | Tennessee Gas Pipeline Company | Houston, TX 77252 | Oil & Gas Operator | Dec 2011 |
| 462 | Tennessee Gas Pipeline Company, LLC | Houston, TX 77252 | Oil Operator | May 2024 |
| 463 | Tepee Petroleum Company, Inc. | Houston, TX 77098 | Oil & Gas Operator | Feb 2014 |
| 464 | Terra Resources, Inc. | Casper, WY 82601 | Oil & Gas Operator | Jun 1990 |
| 465 | Terrier Oil Company | | Oil & Gas Operator | Feb 2015 |
| 466 | Texaco Inc | Kingfisher, OK 73750 | Oil & Gas Operator | Dec 2017 |
| 467 | Texas Meridian Res. Expl., Inc. | Houston, TX 77079 | Oil & Gas Operator | Jun 1998 |
| 468 | Texas Pacific Oil Company Inc. | | Oil & Gas Operator | Dec 1980 |
| 469 | Texas Petroleum Investment Company | Houston, TX 77057 | Oil & Gas Operator | Dec 2024 |
| 470 | The Exploration Co. Of La, Inc | | Oil & Gas Operator | Nov 1987 |
| 471 | The Meridian Res. & Exp. LLC | | Oil & Gas Operator | Sep 2010 |
| 472 | Three S & T Oil Co., Inc. | | Oil & Gas Operator | May 1985 |
| 473 | Three Sisters Investments, LTD | | Oil & Gas Operator | Oct 1989 |
| 474 | Toce Energy, L.L.C. | | Oil & Gas Operator | Dec 2017 |
| 475 | Toce Oil Company | | Oil & Gas Operator | Dec 2014 |
| 476 | Tom West | | Oil & Gas Operator | Nov 1989 |
| 477 | Torrid Energy Company | | Oil & Gas Operator | Jun 1988 |
| 478 | Total Minatome Corporation | Houston, TX 77210 | Oil & Gas Operator | Dec 1998 |
| 479 | Traillour Oil Co. | | Oil & Gas Operator | Mar 1990 |
| 480 | Transcontinental Gas P/L Corp. | | Oil & Gas Operator | Dec 2009 |
| 481 | Transcontinental Gas Pipeline Co LLC | | Oil Operator | Jul 2024 |
| 482 | Transtexas Gas Corporation | Houston, TX 77265 | Oil & Gas Operator | Aug 2005 |
| 483 | Transworld Expl. & Prod., Inc. | | Oil & Gas Operator | Mar 2004 |
| 484 | Trek Resources, Inc. | Dallas, TX 75207 | Oil & Gas Operator | Dec 2024 |
| 485 | Tri Investment Company | | Oil Operator | Mar 1980 |
| 486 | Tri-Production Company | | Oil Operator | Apr 1994 |
| 487 | Tribal Oil Company | | Oil & Gas Operator | Dec 1981 |
| 488 | Trunkline Gas Company | | Oil Operator | Mar 2008 |
| 489 | Tryvest, Inc. | | Oil & Gas Operator | Sep 1991 |
| 490 | Tucker Operating Co., Inc. | Victoria, TX 77903 | Oil & Gas Operator | Dec 2024 |
| 491 | Tundra Energy | | Oil Operator | Jul 2024 |
| 492 | Txo Production Corp. | Ganado, TX 77962 | Oil & Gas Operator | Aug 2022 |
| 493 | TXP Operating Company | | Oil & Gas Operator | Jul 1992 |
| 494 | U. D. Man, Inc. | San Antonio, TX 78212 | Oil & Gas Operator | Dec 2024 |
| 495 | U.S. Exploration Company | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 496 | Union Exploration Partners, LTD. | | Oil & Gas Operator | Aug 1990 |
| 497 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 498 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Sep 2002 |
| 499 | Union Texas Petroleum Corp. | Houston, TX 77252-2120 | Oil & Gas Operator | Dec 2014 |
| 500 | United Gas Pipe Line Co. | | Oil Operator | Aug 1993 |