| 501 | Sabco Operating Company | Houston, TX 77056 | Oil & Gas Operator | Oct 2011 |
| 502 | Sabco Operating Company, LLC | Houston, TX 77056 | Oil & Gas Operator | Jun 2018 |
| 503 | Safari Production Company, Inc. | McAllen, TX 78501 | Oil & Gas Operator | Apr 2026 |
| 504 | Samedan Oil Corporation | Houston, TX 77067 | Oil & Gas Operator | Dec 2019 |
| 505 | Samson Hydrocarbons Company | Tulsa, OK 74103 | Oil & Gas Operator | Nov 2016 |
| 506 | Samson Lone Star LP | Tulsa, OK 74103 | Oil & Gas Operator | Jun 2007 |
| 507 | Samson Lone Star, LLC | Tulsa, OK 74103 | Oil & Gas Operator | Apr 2026 |
| 508 | San Antonio Gas & Oil, Inc. | San Antonio, TX 78209 | Oil & Gas Operator | Feb 2000 |
| 509 | San Isidro Development Co, L. C. | Sandia, TX 78383 | Oil & Gas Operator | Apr 2026 |
| 510 | Sanchez Oil & Gas Corporation | Houston, TX 77056 | Oil & Gas Operator | Apr 2026 |
| 511 | Sanchez-O'Brien Oil & Gas Corp | Houston, TX 77057 | Oil & Gas Operator | May 1998 |
| 512 | Sandalwood Exploration, L.P. | Houston, TX 77056 | Oil & Gas Operator | Apr 2026 |
| 513 | Sandalwood Oil & Gas, Inc. | Houston, TX 77057 | Oil & Gas Operator | Apr 2026 |
| 514 | Sandel Operating Company | Huntsville, TX 77340 | Oil & Gas Operator | Apr 2026 |
| 515 | Santa Fe Energy Oper. Part., LP | Houston, TX 77057 | Oil & Gas Operator | Dec 1994 |
| 516 | Santos USA Corp. | Houston, TX 77042 | Oil & Gas Operator | Dec 2008 |
| 517 | Saratoga Resources, Inc. | Houston, TX 77077 | Oil & Gas Operator | Jul 1994 |
| 518 | Sarita Oil & Gas | Boerne, TX 78006 | Oil & Gas Operator | Jul 2024 |
| 519 | Satex Energy, Inc. | San Antonio, TX 78216 | Oil & Gas Operator | Aug 2003 |
| 520 | Saxet Energy, LTD. | Houston, TX 77057 | Oil & Gas Operator | Mar 2004 |
| 521 | Saxet Petroleum, Inc. | Houston, TX 77057 | Oil & Gas Operator | Apr 2026 |
| 522 | Saxum Oil & Gas, LLC | Beeville, TX 78104 | Oil & Gas Operator | Apr 2026 |
| 523 | Scythian, LTD. | Midland, TX 79701 | Oil & Gas Operator | Dec 2020 |
| 524 | Se USA Operating, Inc. | Houston, TX 77002 | Oil & Gas Operator | Dec 2009 |
| 525 | Shell Western E&P | Houston, TX 77001 | Oil & Gas Operator | Apr 2026 |
| 526 | Shell Western E&P Inc. | Houston, TX 77001 | Oil & Gas Operator | May 2011 |
| 527 | Sheridan Energy,Inc. | Houston, TX 77002 | Oil & Gas Operator | Feb 2000 |
| 528 | Silver Hill Energy Operating, LLC | Dallas, TX 75201 | Oil & Gas Operator | Apr 2026 |
| 529 | Silverbow Resources Oper, LLC | Houston, TX 77002 | Oil & Gas Operator | Apr 2026 |
| 530 | Sklar Exploration Company LLC | Shreveport, LA 71101 | Oil & Gas Operator | Apr 2026 |
| 531 | SM Energy Company | Midland, TX 79707 | Oil & Gas Operator | Apr 2026 |
| 532 | Smith Production Inc. | The Woodlands, TX 77381 | Oil & Gas Operator | Apr 2026 |
| 533 | SN Ef Maverick, LLC | Houston, TX 77002 | Oil & Gas Operator | Aug 2023 |
| 534 | SN Operating, LLC | Houston, TX 77002 | Oil & Gas Operator | May 2023 |
| 535 | Sonat Exploration Co. - Houston | Houston, TX 77251 | Oil & Gas Operator | Dec 1999 |
| 536 | Sonat Exploration Company -Tyler | Houston, TX 77251 | Oil & Gas Operator | Dec 1999 |
| 537 | South Texas Operating Company | San Antonio, TX 78217 | Oil & Gas Operator | Apr 2026 |
| 538 | Southern Resource Company | Corpus Christ, TX 78404 | Oil & Gas Operator | Mar 2022 |
| 539 | Southern Royalty Inc. | Corpus Christ, TX 78411 | Oil & Gas Operator | Feb 1997 |
| 540 | Southland Royalty Company | Houston, TX 77210 | Oil & Gas Operator | Sep 2011 |
| 541 | Southwest Oil & Land, Inc. | Corpus Chrsti, TX 78460 | Oil & Gas Operator | Dec 1999 |
| 542 | Special Energy Corp. | Stillwater, OK 74076 | Oil & Gas Operator | Apr 2026 |
| 543 | Spiller Operating Co., Inc. | Round Rock, TX 78665 | Oil & Gas Operator | May 2015 |
| 544 | Spiller, Robert S. | San Antonio, TX 78213 | Oil & Gas Operator | Oct 1995 |
| 545 | Spri Oil & Gas, LLC | Houston, TX 77090 | Oil & Gas Operator | Mar 2020 |
| 546 | St. Mary Land & Exploration Co | Denver, CO 80201 | Oil & Gas Operator | Jun 2010 |
| 547 | Stampede Energy Corp. | Canada, 00100 | Oil & Gas Operator | Mar 2000 |
| 548 | Starr Operating, LLC | San Antonio, TX 78209 | Oil & Gas Operator | Apr 2026 |
| 549 | Starrak Operating Company, Inc. | Midland, TX 79706 | Oil & Gas Operator | Jun 1999 |
| 550 | STB Energy Inc. | Tulsa, OK 74105 | Oil & Gas Operator | Jul 2008 |
| 551 | Stinger Oil & Gas Inc. | Sherman Oaks, CA 91403 | Oil & Gas Operator | Oct 2013 |
| 552 | Strand Energy, L.C. | Houston, TX 77002 | Oil & Gas Operator | Apr 2026 |
| 553 | Stroube Energy Corporation | Dallas, TX 75248 | Oil & Gas Operator | Jan 2012 |
| 554 | Sue-Ann Operating, L.C. | Victoria, TX 77903 | Oil & Gas Operator | Apr 2026 |
| 555 | Sunwest Oklahoma, Inc | Dallas, TX 75231 | Oil & Gas Operator | May 2023 |
| 556 | Sutton Producing Corp. | San Antonio, TX 78270 | Oil & Gas Operator | Apr 2026 |
| 557 | SV Energy Company, LLC | Corpus Christ, TX 78401 | Oil & Gas Operator | Mar 2017 |
| 558 | Swift Energy Company | Houston, TX 77060 | Oil & Gas Operator | Mar 2021 |
| 559 | Swift Energy Operating, LLC | Houston, TX 77079 | Oil & Gas Operator | Jun 2017 |
| 560 | Tana Oil And Gas Corporation | Irving, TX 75062 | Oil & Gas Operator | Mar 2000 |
| 561 | Tare Resources, LLC | Corpus Chrsti, TX 78426 | Oil & Gas Operator | Apr 2026 |
| 562 | Tasca Exploration Company | Houston, TX 77257 | Oil & Gas Operator | Jun 2002 |
| 563 | TBM Catarina, LLC | Fort Worth, TX 76102 | Oil & Gas Operator | Apr 2026 |
| 564 | TD Natural Resources LLC | Cuero, TX 77954 | Oil & Gas Operator | Apr 2026 |
| 565 | TDC Engineering, Inc. | Abilene, TX 79604 | Oil & Gas Operator | Apr 2026 |
| 566 | Teal Energy USA, Inc. | Houston, TX 77057 | Oil & Gas Operator | Apr 2026 |
| 567 | Tejas Gas Pipeline, L.P. | Houston, TX 77002 | Oil & Gas Operator | Feb 2002 |
| 568 | Tepee Petroleum Company, Inc. | Houston, TX 77098 | Oil & Gas Operator | Feb 2014 |
| 569 | Tesoro E&P Company, L.P. | San Antonio, TX 78216 | Oil & Gas Operator | Jan 2000 |
| 570 | Tesoro Expl. & Prod. Company | San Antonio, TX 78216 | Gas Operator | Sep 2010 |
| 571 | Texaco E & P Inc. | Houston, TX 77099 | Oil & Gas Operator | Apr 2026 |
| 572 | Texan Production | Pearsall, TX 78061 | Oil & Gas Operator | Aug 2003 |
| 573 | Texan Production Company, Inc. | Canyon Lake, TX 78133 | Oil & Gas Operator | Apr 2026 |
| 574 | Texas Crude Energy, Inc. | Houston, TX 77256 | Oil & Gas Operator | Oct 2012 |
| 575 | Texas Independent Explor LTD. | Houston, TX 77024 | Oil & Gas Operator | Apr 2026 |
| 576 | Texas, Les & Co. | Brenham, TX 77833 | Oil & Gas Operator | Apr 2026 |
| 577 | Texron Operating, LLC | Bulverde, TX 78163 | Oil & Gas Operator | Apr 2026 |
| 578 | Thorp Petroleum Corporation | Houston, TX 77002 | Oil & Gas Operator | Feb 2014 |
| 579 | Three C Exploration, LLC | Hebbronville, TX 78361 | Oil & Gas Operator | Apr 2026 |
| 580 | Three-C Oil And Gas | Hebbronville, TX 78361 | Oil & Gas Operator | Apr 2026 |
| 581 | Tidal Petroleum, Inc. | Schertz, TX 78154 | Oil & Gas Operator | Apr 2026 |
| 582 | Titan Resources I, Inc. | Midland, TX 79701 | Oil & Gas Operator | Jun 2000 |
| 583 | TNR Petroleum, Inc. | Austin, TX 78747 | Oil & Gas Operator | Sep 1999 |
| 584 | Tola Production Company | Dallas, TX 75367 | Oil & Gas Operator | Apr 2026 |
| 585 | Torch Operating Company | Houston, TX 77010 | Oil & Gas Operator | Mar 2015 |
| 586 | Tradition Resources Oper, LLC | Houston, TX 77002 | Oil & Gas Operator | Jul 2017 |
| 587 | Trans-Pecos Resources, Inc. | Houston, TX 77056 | Oil & Gas Operator | Apr 2026 |
| 588 | Transamerican Natural Gas Corp. | Houston, TX 77032 | Oil & Gas Operator | Aug 2000 |
| 589 | Transtexas Gas Corporation | Houston, TX 77265 | Oil & Gas Operator | Aug 2005 |
| 590 | Tri-C Resources, Inc. | Houston, TX 77024 | Oil & Gas Operator | Aug 2009 |
| 591 | Trinity Operating (Usg), LLC | Houston, TX 77002 | Oil & Gas Operator | Apr 2026 |
| 592 | Trinity River Energy Oper, LLC | Houston, TX 77008 | Oil & Gas Operator | May 2018 |
| 593 | Tristar Oil & Gas | Freer, TX 78357 | Oil & Gas Operator | Apr 2026 |
| 594 | Trium, LTD. | Laredo, TX 78041 | Oil Operator | Apr 2026 |
| 595 | Troubadour Operating, LLC | Houston, TX 77019 | Oil & Gas Operator | Apr 2026 |
| 596 | TX Petroleum Company | Corpus Christ, TX 78412 | Oil & Gas Operator | Apr 1996 |
| 597 | Txco Resources Inc. | San Antonio, TX 78280 | Oil & Gas Operator | Apr 2026 |
| 598 | U. S. Operating, Inc. | Dallas, TX 75252 | Oil & Gas Operator | Jul 2025 |
| 599 | U.S. Enercorp, LTD. | San Antonio, TX 78209 | Oil & Gas Operator | Sep 2019 |
| 600 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |