| 501 | Pioneer Natural Res. USA, Inc. | Spring, TX 77389 | Oil & Gas Operator | Sep 2026 |
| 502 | Pioneer Resources Producing, L.P | Irving, TX 75039 | Oil & Gas Operator | Feb 2001 |
| 503 | Pitco Investments, LTD. | Scottsdale, AZ 85261 | Oil & Gas Operator | Jan 2013 |
| 504 | Plains Production Inc | Wichita Falls, TX 76308 | Oil & Gas Operator | Dec 1995 |
| 505 | Pogo Producing Company | Houston, TX 77002 | Oil & Gas Operator | Jan 2008 |
| 506 | Poynor Corporation | Beaumont, TX 77706 | Oil & Gas Operator | Sep 2026 |
| 507 | Pride Energy Company | Tulsa, OK 74170 | Oil & Gas Operator | Sep 2026 |
| 508 | Pringle Resources, Inc. | Houston, TX 77019 | Oil & Gas Operator | Sep 2026 |
| 509 | Prize Operating Company | Grapevine, TX 76051 | Oil & Gas Operator | Aug 2016 |
| 510 | Producers Well Service, Inc. | Boling, TX 77420 | Oil & Gas Operator | Sep 2026 |
| 511 | Proline Energy Resources Inc | Sugar Land, TX 77479 | Oil & Gas Operator | Sep 2026 |
| 512 | Property Development Group, Inc. | San Antonio, TX 78212 | Oil & Gas Operator | Sep 2026 |
| 513 | Pure Resources, L.P. | Midland, TX 79701 | Oil & Gas Operator | Mar 2006 |
| 514 | Questar Expl. And Prod. Co. | Salt Lake Cty, UT 84145 | Oil & Gas Operator | Jul 2011 |
| 515 | Quintana Pet. Corp. | Refugio, TX 78377 | Oil & Gas Operator | Dec 2000 |
| 516 | R & S Energy Company | Luling, TX 78648 | Oil & Gas Operator | Dec 2010 |
| 517 | R&R Resources Corporation | Houston, TX 77056 | Oil & Gas Operator | Dec 2015 |
| 518 | Radley Children Trust | El Campo, TX 77437 | Gas Operator | Jul 2007 |
| 519 | Ram Operating Company, Inc. | Houston, TX 77002 | Oil & Gas Operator | Sep 2012 |
| 520 | Ramsey Production Company, LLC | Austin, TX 78766 | Oil & Gas Operator | Jan 2017 |
| 521 | Range Production Company | Fort Worth, TX 76102 | Oil & Gas Operator | Sep 2021 |
| 522 | Rayalto Oil & Gas, Inc. | MC Queeney, TX 78123 | Oil & Gas Operator | Mar 2004 |
| 523 | Rcy Mineral Group, Inc. | El Campo, TX 77437 | Oil Operator | Jul 2010 |
| 524 | Reef Exploration, Inc. (A-1) | Richardson, TX 75080 | Oil & Gas Operator | Oct 2006 |
| 525 | Remora Management, LLC | The Woodlands, TX 77382 | Oil & Gas Operator | Sep 2026 |
| 526 | Renaissance Petroleum Co LLC | Houston, TX 77058 | Oil & Gas Operator | Nov 2011 |
| 527 | Reo Operating LLC | Austin, TX 78747 | Oil & Gas Operator | Sep 2026 |
| 528 | Resaca Resources, L.L.C. | Austin, TX 78746 | Oil & Gas Operator | Sep 2026 |
| 529 | Resource Expl & Prod, Inc. | Salado, TX 76571 | Oil & Gas Operator | Sep 2026 |
| 530 | Richardson, Marshall T. | Midfield, TX 77458 | Oil & Gas Operator | Sep 2026 |
| 531 | Ricochet Energy, Inc. | San Antonio, TX 78258 | Oil & Gas Operator | Sep 2026 |
| 532 | Rincon Petroleum Corporation | Corpus Chrsti, TX 78427 | Oil & Gas Operator | Sep 2026 |
| 533 | Rio-Tex, Inc. | San Antonio, TX 78258 | Oil & Gas Operator | Sep 2026 |
| 534 | Riptide Energy LLC | Austin, TX 78701 | Oil & Gas Operator | Sep 2026 |
| 535 | Roc Operating, Inc. | Plano, TX 75093 | Oil & Gas Operator | Oct 2008 |
| 536 | Rock Resources, Inc. | Corpus Chrsti, TX 78414 | Oil & Gas Operator | Sep 2026 |
| 537 | Rodeo Resources, L.L.C. | Houston, TX 77079 | Oil & Gas Operator | Dec 2024 |
| 538 | Rodessa Operating Company | Corpus Chrsti, TX 78426 | Oil & Gas Operator | Sep 2026 |
| 539 | Roome Exploration Company | Bartlett, TX 76511 | Oil & Gas Operator | Mar 2008 |
| 540 | Roome Oil Co. | Bartlett, TX 76511 | Oil & Gas Operator | Sep 2026 |
| 541 | Ross Production Co. | Shreveport, LA 71101 | Oil & Gas Operator | Mar 2000 |
| 542 | Rowan-Ungerecht, Inc. | Van, TX 75790 | Oil & Gas Operator | Sep 1993 |
| 543 | Royal Oil & Gas Corp. | Indiana, PA 15701 | Oil & Gas Operator | Apr 2014 |
| 544 | Royko Oil Company | Horseshoe Bay, TX 78657 | Oil & Gas Operator | Sep 2026 |
| 545 | RPM Operating Company | New Braunfels, TX 78131 | Oil & Gas Operator | Mar 2008 |
| 546 | S & P Energy, Inc. | Benbrook, TX 76126 | Oil & Gas Operator | Aug 2003 |
| 547 | S & S Operating Company, Inc. | Winnie, TX 77665 | Oil & Gas Operator | Sep 2026 |
| 548 | S N D Energy Company, Inc. | Kilgore, TX 75662 | Oil & Gas Operator | Sep 2026 |
| 549 | Sable Energy Corp. | Houston, TX 77057 | Oil & Gas Operator | Nov 1999 |
| 550 | Samson Exploration LLC | Tulsa, OK 74101 | Oil & Gas Operator | Jul 2026 |
| 551 | Samson Hydrocarbons Company | Tulsa, OK 74103 | Oil & Gas Operator | Nov 2016 |
| 552 | Samson Lone Star LP | Tulsa, OK 74103 | Oil & Gas Operator | Jun 2007 |
| 553 | Samson Lone Star, LLC | Tulsa, OK 74103 | Oil & Gas Operator | Sep 2026 |
| 554 | Samson Resources Company | Tulsa, OK 74103 | Oil & Gas Operator | Jul 2026 |
| 555 | Sanchez Exploration Company LLC | Houston, TX 77056 | Oil & Gas Operator | Oct 2024 |
| 556 | Sanchez Oil & Gas Corporation | Houston, TX 77056 | Oil & Gas Operator | Sep 2026 |
| 557 | Sandel Energy, Inc. | Huntsville, TX 77342 | Oil & Gas Operator | Apr 2004 |
| 558 | Sandel Operating Company | Huntsville, TX 77340 | Oil & Gas Operator | Sep 2026 |
| 559 | Sandridge Onshore, LLC | Houston, TX 77010 | Oil & Gas Operator | Jun 2014 |
| 560 | Sanhall Corporation | Huntsville, TX 77340 | Oil & Gas Operator | Oct 1993 |
| 561 | Santa Fe Energy Oper. Part., LP | Houston, TX 77057 | Oil & Gas Operator | Dec 1994 |
| 562 | Scoggins Oil & Gas Co. | Seabrook, TX 77586 | Oil & Gas Operator | Jun 2000 |
| 563 | Scully And Smith Oil Corporation | Salado, TX 76571 | Oil & Gas Operator | Feb 1995 |
| 564 | Seagull Energy E & P Inc | Houston, TX 77002 | Oil & Gas Operator | Jan 2015 |
| 565 | Seagull Operating Co., Inc. | Shreveport, LA 71101 | Oil & Gas Operator | Jan 2025 |
| 566 | Sedona Oil & Gas Corporation | Dallas, TX 75231 | Oil & Gas Operator | Sep 2026 |
| 567 | Setex Oil And Gas Company | Houston, TX 77002 | Oil & Gas Operator | Feb 2012 |
| 568 | Sev Texas Operating, LLC | Long Beach, CA 90755 | Oil & Gas Operator | Sep 2026 |
| 569 | Shana Petroleum Company | Dallas, TX 75206 | Oil & Gas Operator | Aug 2002 |
| 570 | Shanghai Energy Corporation | Houston, TX 77027 | Oil & Gas Operator | Apr 2003 |
| 571 | Sharon Resources, Inc. | Houston, TX 77056 | Oil & Gas Operator | Aug 2010 |
| 572 | Sheridan Energy,Inc. | Houston, TX 77002 | Oil & Gas Operator | Feb 2000 |
| 573 | Shidler, Mark L., Inc. | Houston, TX 77055 | Oil & Gas Operator | Sep 2026 |
| 574 | Shoco Production LLC | Kilgore, TX 75663 | Oil & Gas Operator | Sep 2026 |
| 575 | Shoco Production, L.P. | Kilgore, TX 75663 | Oil & Gas Operator | May 2020 |
| 576 | Silver Pines Energy Corp. | Houston, TX 77005 | Oil & Gas Operator | Jun 2026 |
| 577 | Smith Petroleum Company | Spring, TX 77389 | Oil & Gas Operator | Sep 2026 |
| 578 | Smith Production Inc. | The Woodlands, TX 77381 | Oil & Gas Operator | Sep 2026 |
| 579 | SMR Natural Gas Ventures Inc | Oklahoma City, OK 73112 | Oil & Gas Operator | Jan 1999 |
| 580 | Sonat Exploration Co. - Houston | Houston, TX 77251 | Oil & Gas Operator | Dec 1999 |
| 581 | South Texas Operating Company | San Antonio, TX 78217 | Oil & Gas Operator | Sep 2026 |
| 582 | Southeastern Pipe Line Company | Tyler, TX 75711 | Oil & Gas Operator | Dec 2020 |
| 583 | Southern G Holdings, LLC | Houston, TX 77002 | Oil & Gas Operator | Dec 2007 |
| 584 | Southwest Resources, Inc. | Brenham, TX 77834 | Oil & Gas Operator | Sep 2026 |
| 585 | Southwest Royalties, Inc. | Midland, TX 79710 | Oil & Gas Operator | Sep 2026 |
| 586 | Special Energy Corp. | Stillwater, OK 74076 | Oil & Gas Operator | Sep 2026 |
| 587 | Spicewood Operating Company, LLC | Austin, TX 78746 | Oil & Gas Operator | Sep 2026 |
| 588 | Square Mile Energy, L.L.C. | Houston, TX 77057 | Oil & Gas Operator | Sep 2026 |
| 589 | Stephens Production Company | The Woodlands, TX 77381 | Oil & Gas Operator | Jul 2026 |
| 590 | Stinger Oil & Gas Inc. | Sherman Oaks, CA 91403 | Oil & Gas Operator | Oct 2013 |
| 591 | Stone & Webster Oil Company, Inc | Houston, TX 77002 | Oil & Gas Operator | Dec 1995 |
| 592 | Stratco Operating Co., Inc. | Austin, TX 78701 | Oil & Gas Operator | Sep 2026 |
| 593 | Sue-Ann Operating, L.C. | Victoria, TX 77903 | Oil & Gas Operator | Sep 2026 |
| 594 | Sue-Ann Production Company | Victoria, TX 77903 | Oil & Gas Operator | Mar 2008 |
| 595 | Sundown Energy LP | Dallas, TX 75248 | Oil & Gas Operator | Sep 2026 |
| 596 | Sundown Energy, Inc. | Dallas, TX 75240 | Oil & Gas Operator | May 2025 |
| 597 | Swift Energy Company | Houston, TX 77060 | Oil & Gas Operator | Mar 2021 |
| 598 | Sydri Operating, LLC | Dallas, TX 75231 | Oil & Gas Operator | Sep 2026 |
| 599 | Synergy Oil & Gas, Inc. (A) | Houston, TX 77024 | Oil & Gas Operator | Aug 2001 |
| 600 | Synergy Production Company | Houston, TX 77024 | Oil & Gas Operator | Jan 1996 |