| 501 | T. K. Stanley, Inc. | | Oil & Gas Operator | Jul 1982 |
| 502 | T. O. Kimbrell, LLC | | Oil & Gas Operator | Jul 2025 |
| 503 | Taza Energy, Inc. | | Oil & Gas Operator | Nov 2009 |
| 504 | Team Operating, L.L.C. | Pinehurst, TX 77362 | Oil & Gas Operator | Oct 2025 |
| 505 | Tellus Operating Group, LLC | | Oil & Gas Operator | Jun 2025 |
| 506 | Temple Oil Co | | Oil & Gas Operator | Oct 1992 |
| 507 | Terry Sims & Associates, Inc. | | Oil Operator | Sep 2009 |
| 508 | Tesoro Petroleum Corporation | | Oil & Gas Operator | May 1982 |
| 509 | Texaco E & P Inc | Houston, TX 77099 | Oil & Gas Operator | Oct 2025 |
| 510 | Texaco Inc | Kingfisher, OK 73750 | Oil & Gas Operator | Dec 2017 |
| 511 | Texaco Seaboard, Inc. | | Gas Operator | Sep 1980 |
| 512 | Texas Petroleum Investment Company | Houston, TX 77057 | Oil & Gas Operator | Oct 2025 |
| 513 | Thaxton Operating | | Oil Operator | Jan 1994 |
| 514 | The Petroleum Corp Of Delaware | | Oil & Gas Operator | May 1991 |
| 515 | Thomas A. Blanton | | Oil Operator | Jun 2025 |
| 516 | Thunder Oil, LLC | | Oil & Gas Operator | Oct 1998 |
| 517 | Tiger Production Company, LLC | | Oil & Gas Operator | Aug 2021 |
| 518 | Tigrett, Terry A. Jr. | | Oil & Gas Operator | Oct 1980 |
| 519 | Tilghman Operating, LLC. | | Oil & Gas Operator | Jul 2025 |
| 520 | TNT Operating LLC | | Oil & Gas Operator | Aug 2016 |
| 521 | Tomlinson Interests | | Oil & Gas Operator | Jan 1983 |
| 522 | Tops Operating Co.,Inc. | | Oil Operator | Dec 1985 |
| 523 | Transcontinental Oil Corp. | | Oil & Gas Operator | Sep 1985 |
| 524 | Trendsetter Production Co, Inc | | Oil & Gas Operator | Jul 2008 |
| 525 | Tri-Quest Resources | | Oil & Gas Operator | Feb 1995 |
| 526 | Triad Oil & Gas Co Inc | | Oil & Gas Operator | Jun 1994 |
| 527 | Triangle Oil Producers, Inc. | | Oil & Gas Operator | Jun 1998 |
| 528 | Trident Oil And Gas Corp. | | Oil & Gas Operator | Sep 2000 |
| 529 | Trinity Oil & Gas Dev Inc | | Oil & Gas Operator | Jun 1994 |
| 530 | Trio Operating Company, Inc. | Wichita Falls, TX 76307 | Oil & Gas Operator | Apr 2006 |
| 531 | Tuway Oil, Inc | | Oil & Gas Operator | Jun 2006 |
| 532 | Txo Production Corp. | Ganado, TX 77962 | Oil & Gas Operator | Aug 2022 |
| 533 | Ultramar Oil & Gas LTD | Houston, TX 77060 | Oil & Gas Operator | Jul 1995 |
| 534 | Umc Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2015 |
| 535 | Union Producing Co. | | Gas Operator | Dec 1992 |
| 536 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Oct 2025 |
| 537 | Unocal Explor. Corp. | | Oil & Gas Operator | Nov 1990 |
| 538 | Ventex Operating Corp. | Addison, TX 75001 | Oil & Gas Operator | Oct 2025 |
| 539 | Venture Oil & Gas, Inc. | Laurel, MS 39440 | Oil & Gas Operator | Jul 2025 |
| 540 | Vernon E. Faulconer, Inc. | Tyler, TX 75711 | Oil & Gas Operator | Dec 2024 |
| 541 | Veron E.Faulconer Inc | | Oil & Gas Operator | Nov 1989 |
| 542 | Vicksburg Refining, Inc. -Jackson | | Oil Operator | Apr 1984 |
| 543 | Vicksburg Refining, Inc. -Vicksburg | | Oil Operator | Apr 1984 |
| 544 | Victor Producers , LLC. | | Oil & Gas Operator | Jun 2025 |
| 545 | Vines Operating, LLC | | Oil Operator | Jun 2017 |
| 546 | Vintage Petroleum | | Oil & Gas Operator | Feb 2003 |
| 547 | Vonco Of Mississippi, Inc. | | Oil Operator | Jul 2025 |
| 548 | W. E. O'Malley, Inc. | | Oil & Gas Operator | Jun 1991 |
| 549 | W.I.F.T. Operating, LLC | | Oil & Gas Operator | Jul 2025 |
| 550 | W.S. Red Hancock, Inc. | | Oil Operator | Dec 1986 |
| 551 | Waco Corp | | Oil Operator | Jun 1983 |
| 552 | Wagner Oil Company | Fort Worth, TX 76102 | Oil & Gas Operator | Oct 2025 |
| 553 | Waller Brothers, Inc. | | Oil & Gas Operator | Jul 2004 |
| 554 | Watchtower Petroleum, LLC | | Oil & Gas Operator | Jun 2025 |
| 555 | Weeks Exploration Company | Houston, TX 77063 | Oil & Gas Operator | Aug 1995 |
| 556 | Weiser-Brown Operating Company | Magnolia, AR 71754 | Oil & Gas Operator | Oct 2025 |
| 557 | Westfield Energy Corp. | | Oil & Gas Operator | Mar 1991 |
| 558 | White River Operating LLC | Gilmer, TX 75644 | Oil & Gas Operator | Jul 2025 |
| 559 | White, Charles R | | Oil Operator | Mar 1987 |
| 560 | Whitehead, Cecil | | Oil Operator | May 1997 |
| 561 | Wickham, R. R. | | Oil Operator | Jan 1980 |
| 562 | Wilcox Energy Company | | Oil & Gas Operator | Jul 2025 |
| 563 | Wilcox Operating Corporation | Shreveport, LA 71115 | Oil & Gas Operator | Oct 2025 |
| 564 | Wilcox Ventures, LLC | | Oil & Gas Operator | Jul 2025 |
| 565 | Will-Drill Production Co., Inc. | Shreveport, LA 71105 | Oil & Gas Operator | Oct 2025 |
| 566 | Williams Producing Co | | Oil & Gas Operator | May 2025 |
| 567 | Williams, Kenneth O. Jr | | Oil Operator | Nov 2006 |
| 568 | WLS, Inc | | Oil & Gas Operator | Jul 2025 |
| 569 | Womack Energy, Inc. | Houston, TX 77057 | Oil & Gas Operator | Jul 2025 |
| 570 | Wyble L. Ollie | | Oil & Gas Operator | Dec 1988 |
| 571 | Xmco Inc | | Oil & Gas Operator | Sep 1986 |
| 572 | Yellow Creek Operating, LLC | | Oil & Gas Operator | Jun 2025 |