| 601 | Slack Oil & Gas | Refugio, TX 78377 | Oil & Gas Operator | Dec 2012 |
| 602 | SM Operating Company LLC | Houston, TX 77056 | Oil & Gas Operator | Mar 2026 |
| 603 | Smith Operating And MGMT Co. | Shreveport, LA 71161 | Oil & Gas Operator | Jun 2023 |
| 604 | Smith Production Inc. | The Woodlands, TX 77381 | Oil & Gas Operator | Mar 2026 |
| 605 | Snyder Oil Corporation | Houston, TX 77024 | Oil & Gas Operator | Mar 2008 |
| 606 | Soco Gas Properties | Goliad, TX 77963 | Oil & Gas Operator | Mar 2026 |
| 607 | South Texas Injection Company | Mineral, TX 78125 | Oil & Gas Operator | Dec 2016 |
| 608 | Southern Resource Company | Corpus Chrsti, TX 78404 | Oil & Gas Operator | Mar 2022 |
| 609 | Southwest Investment Fund, Inc. | Dallas, TX 75229 | Oil & Gas Operator | Aug 2003 |
| 610 | Southwest Land & Minerals, Inc. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Aug 2003 |
| 611 | Southwest Royalties, Inc. | Midland, TX 79710 | Oil & Gas Operator | Mar 2026 |
| 612 | Spiller Operating Co., Inc. | Round Rock, TX 78665 | Oil & Gas Operator | May 2015 |
| 613 | Spiller, Robert S. | San Antonio, TX 78213 | Oil & Gas Operator | Oct 1995 |
| 614 | Spri Oil & Gas, LLC | Houston, TX 77090 | Oil & Gas Operator | Mar 2020 |
| 615 | Staples, James W. | Tuleta, TX 78162 | Oil & Gas Operator | Sep 2014 |
| 616 | Staples, Tommy Oil Co. | Pettus, TX 78146 | Oil & Gas Operator | Mar 2008 |
| 617 | Star Of Texas Energy SRVS, Inc. | Austin, TX 78702 | Oil & Gas Operator | Mar 2026 |
| 618 | Star Production, Inc. | Dallas, TX 75360 | Oil & Gas Operator | Mar 2026 |
| 619 | Starco Exploration, Inc. | Dallas, TX 75360 | Oil & Gas Operator | Mar 2026 |
| 620 | Stark Petroleum | Tuleta, TX 78162 | Oil & Gas Operator | Mar 2026 |
| 621 | Stephens Production Company | The Woodlands, TX 77381 | Oil & Gas Operator | Jan 2026 |
| 622 | Strago Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Aug 1994 |
| 623 | Stratco Operating Co Inc | Austin, TX 78701 | Oil & Gas Operator | Mar 2026 |
| 624 | Stroud Petroleum, Inc. | Shreveport, LA 71162 | Oil & Gas Operator | Mar 2026 |
| 625 | Sue-Ann Operating, L.C. | Victoria, TX 77903 | Oil & Gas Operator | Mar 2026 |
| 626 | Sue-Ann Production Company | Victoria, TX 77903 | Oil & Gas Operator | Mar 2008 |
| 627 | Suemaur Exploration, Inc. | Corpus Chrsti, TX 78470 | Oil & Gas Operator | Mar 2008 |
| 628 | Sun Exploration, Inc. | Alice, TX 78333 | Oil & Gas Operator | Mar 2026 |
| 629 | Sunburst, Inc. | Wheat Ridge, CO 80033 | Oil & Gas Operator | Dec 2025 |
| 630 | Superior Oil & Gas Invt, L.L.C. | Conroe, TX 77305 | Gas Operator | Jul 2018 |
| 631 | Sure Flow Oil & Gas Company | Victoria, TX 77902 | Oil & Gas Operator | Mar 2008 |
| 632 | Sure Flow Oil & Gas, Inc. | Victoria, TX 77902 | Oil & Gas Operator | Mar 2026 |
| 633 | Swift Energy Company | Houston, TX 77060 | Oil & Gas Operator | Mar 2021 |
| 634 | Swift Energy Operating, LLC | Houston, TX 77079 | Oil & Gas Operator | Jun 2017 |
| 635 | T - C Oil Company | Refugio, TX 78377 | Oil & Gas Operator | Jan 2012 |
| 636 | T-C Oil Company, LLC | Refugio, TX 78377 | Oil & Gas Operator | Mar 2026 |
| 637 | T.D. Operating Company, Inc. | New Braunfels, TX 78130 | Oil & Gas Operator | Nov 1999 |
| 638 | Talon Development Company | Boerne, TX 78006 | Oil & Gas Operator | Sep 2007 |
| 639 | Tamarack Petroleum Company, Inc. | Midland, TX 79701 | Oil & Gas Operator | Mar 2026 |
| 640 | Tana Oil And Gas Corporation | Irving, TX 75062 | Oil & Gas Operator | Mar 2000 |
| 641 | Taos Resources Operating Co LLC | Houston, TX 77037 | Oil & Gas Operator | Dec 2019 |
| 642 | Tare Resources, LLC | Corpus Chrsti, TX 78426 | Oil & Gas Operator | Mar 2026 |
| 643 | Tasca Exploration Company | Houston, TX 77257 | Oil & Gas Operator | Jun 2002 |
| 644 | Teco Oil & Gas, Inc. | Tampa, FL 33601 | Oil & Gas Operator | Nov 1997 |
| 645 | Teco Operating Company | Athens, TX 75751 | Oil & Gas Operator | Jun 2001 |
| 646 | Tecpetrol Operating LLC | Houston, TX 77027 | Oil & Gas Operator | Dec 2015 |
| 647 | Tema Oil And Gas Company | Houston, TX 77084 | Oil & Gas Operator | Mar 2026 |
| 648 | Tema Oil And Gas, LLC | Houston, TX 77040 | Oil & Gas Operator | Apr 2000 |
| 649 | Tempest Energy Resources, LP | Houston, TX 77251 | Oil & Gas Operator | Jun 2013 |
| 650 | Tepco, Inc. | Houston, TX 77002 | Oil & Gas Operator | Oct 1999 |
| 651 | Tepee Petroleum Company, Inc. | Houston, TX 77098 | Oil & Gas Operator | Feb 2014 |
| 652 | Terrafina Energy, LLC | San Antonio, TX 78280 | Oil & Gas Operator | Mar 2026 |
| 653 | Tesoro E&P Company, L.P. | San Antonio, TX 78216 | Oil & Gas Operator | Jan 2000 |
| 654 | Tesoro Expl. & Prod. Company | San Antonio, TX 78216 | Gas Operator | Sep 2010 |
| 655 | Texacal, Inc. | Newport Beach, CA 92660 | Oil & Gas Operator | Mar 2026 |
| 656 | Texaco E & P Inc. | Houston, TX 77099 | Oil & Gas Operator | Mar 2026 |
| 657 | Texakoma E & P, LLC | Plano, TX 75024 | Oil & Gas Operator | Mar 2026 |
| 658 | Texakoma Oil & Gas Corp | Dallas, TX 75240 | Oil & Gas Operator | Sep 2014 |
| 659 | Texakoma Operating, L.P. | Plano, TX 75024 | Oil & Gas Operator | Mar 2025 |
| 660 | Texana Operating Company | Houston, TX 77090 | Oil & Gas Operator | Mar 2026 |
| 661 | Texcal Energy (GP) LLC | Denver, CO 80202 | Oil & Gas Operator | Mar 2016 |
| 662 | Tharp Operating Company | Houston, TX 77070 | Oil & Gas Operator | Nov 2014 |
| 663 | Third Coast Energy, Inc. | Corpus Chrsti, TX 78427 | Oil & Gas Operator | Mar 2026 |
| 664 | Thunderbird Energy, Inc. | Norman, OK 73069 | Oil & Gas Operator | Mar 2026 |
| 665 | Tidal Petroleum, Inc. | Schertz, TX 78154 | Oil & Gas Operator | Mar 2026 |
| 666 | Tidewater Minerals Corporation | Orange Grove, TX 78372 | Oil & Gas Operator | Mar 2026 |
| 667 | Tiki Oil & Gas, LLC | Cisco, TX 76437 | Oil & Gas Operator | Mar 2026 |
| 668 | Top Op, L.L.C. | Houston, TX 77077 | Oil & Gas Operator | May 2020 |
| 669 | Total E&P USA, Inc. | Houston, TX 77210 | Oil & Gas Operator | May 2025 |
| 670 | Totalfinaelf E&P USA Inc | Houston, TX 77024 | Oil & Gas Operator | Jul 2007 |
| 671 | Tpet, Inc. | Dallas, TX 75204 | Oil & Gas Operator | Mar 2008 |
| 672 | Transamerican Natural Gas Corp. | Houston, TX 77032 | Oil & Gas Operator | Aug 2000 |
| 673 | Transcontinental Minerals Corp. | The Woodlands, TX 77380 | Oil & Gas Operator | Dec 2008 |
| 674 | Transpacific Energy, LLC | Katy, TX 77450 | Oil & Gas Operator | Mar 2026 |
| 675 | Transtexas Gas Corporation | Houston, TX 77265 | Oil & Gas Operator | Aug 2005 |
| 676 | Trek Oil & Gas, Inc | Houston, TX 77002 | Oil Operator | Mar 1998 |
| 677 | Tres Operating Co., LLC | Katy, TX 77494 | Oil Operator | Mar 2026 |
| 678 | Tri-C Resources, Inc. | Houston, TX 77024 | Oil & Gas Operator | Aug 2009 |
| 679 | Tri-C Resources, LLC | Houston, TX 77024 | Oil & Gas Operator | Mar 2026 |
| 680 | Tri-Union Development Corp. | Houston, TX 77002 | Oil & Gas Operator | Mar 2026 |
| 681 | Triad Energy Corporation | Houston, TX 77057 | Oil & Gas Operator | Oct 2011 |
| 682 | Trident Corporation | Woodsboro, TX 78393 | Oil & Gas Operator | Mar 2026 |
| 683 | Trinity River Energy Oper, LLC | Houston, TX 77008 | Oil & Gas Operator | May 2018 |
| 684 | Trio Consulting & Management,LLC | Wichita Falls, TX 76307 | Oil & Gas Operator | Mar 2026 |
| 685 | Tristar Exploration, Inc | Pflugerville, TX 78660 | Oil & Gas Operator | Mar 2026 |
| 686 | Tsoco | Tuleta, TX 78162 | Oil & Gas Operator | Apr 2017 |
| 687 | Tucker Operating Co., Inc. | Victoria, TX 77903 | Oil & Gas Operator | Mar 2026 |
| 688 | Turner, M. O. | San Antonio, TX 78278 | Oil & Gas Operator | Apr 2003 |
| 689 | TX Lone Star Operating Co, LLC | Sulphur SPGS, TX 75483 | Oil & Gas Operator | Mar 2026 |
| 690 | U.S. Enercorp, LLC | San Antonio, TX 78217 | Oil & Gas Operator | Jul 2004 |
| 691 | U.S. Enercorp, LTD. | San Antonio, TX 78209 | Oil & Gas Operator | Sep 2019 |
| 692 | U.S. Exploration Company | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 693 | U1 Ranch Oil | Houston, TX 77269 | Oil & Gas Operator | Mar 2026 |
| 694 | Union Gas Operating Company | Spring, TX 77391 | Oil & Gas Operator | Mar 2026 |
| 695 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Jan 2001 |
| 696 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Mar 2026 |
| 697 | United Resources LP | Austin, TX 78746 | Oil & Gas Operator | Oct 2011 |
| 698 | United Texas Oil LLC | Houston, TX 77027 | Oil & Gas Operator | Mar 2026 |
| 699 | Universal Geopower LLC | Houston, TX 77057 | Oil & Gas Operator | May 2016 |
| 700 | Unoco, Inc. | Kerrville, TX 78029 | Oil & Gas Operator | Jan 1999 |