| 501 | Union Oil Co Of California | Midland, TX 79706 | Oil & Gas Operator | Jan 2022 |
| 502 | Union Pacific Resources Co. | Fort Worth, TX 76101 | Oil & Gas Operator | Jan 2001 |
| 503 | Unit Petroleum Company | Tulsa, OK 74170 | Oil & Gas Operator | Feb 2026 |
| 504 | United Oil & Shale LLC | Woodward, OK 73801 | Oil & Gas Operator | Feb 2026 |
| 505 | Universal Resources Corp. | Salt Lake Cty, UT 84145 | Oil & Gas Operator | Jan 2000 |
| 506 | Upland Resources LLC | Canadian, TX 79014 | Oil & Gas Operator | Feb 2026 |
| 507 | Upland Resources, Inc. | Canadian, TX 79014 | Oil & Gas Operator | Dec 2009 |
| 508 | Us Petro LP | Amarillo, TX 79106 | Oil & Gas Operator | Apr 2020 |
| 509 | Vanguard Operating, LLC | Houston, TX 77057 | Oil & Gas Operator | Aug 2019 |
| 510 | Vantage Point Operating Co. | Houston, TX 77057 | Oil & Gas Operator | Dec 2014 |
| 511 | Veritas Energy LLC | San Antonio, TX 78231 | Oil & Gas Operator | Feb 2026 |
| 512 | Vintage Petroleum, Inc. | Houston, TX 77046 | Oil & Gas Operator | Oct 2025 |
| 513 | Vista Oil & Gas, Inc. | The Woodlands, TX 77382 | Oil & Gas Operator | Feb 2000 |
| 514 | Vistatex Energy LLC | Houston, TX 77057 | Oil & Gas Operator | Nov 2025 |
| 515 | VT VIstatex Energy LLC | Houston, TX 77056 | Oil & Gas Operator | Feb 2026 |
| 516 | Walsh & Watts Inc | Aledo, TX 76008 | Oil & Gas Operator | Feb 2026 |
| 517 | Warren Petroleum/Danc Operating | Wichita Falls, TX 76301 | Oil & Gas Operator | Sep 1998 |
| 518 | Washita Oil And Gas, L.L.C. | Tulsa, OK 74136 | Oil & Gas Operator | Mar 2015 |
| 519 | Watson Operating Company | Pampa, TX 79066 | Oil & Gas Operator | Dec 2003 |
| 520 | Weinkauf Petroleum, Inc. | Tulsa, OK 74136 | Oil & Gas Operator | Dec 2025 |
| 521 | Western Chief Operating, L.L.C. | Graham, TX 76450 | Oil & Gas Operator | Feb 2026 |
| 522 | Weststar Oil & Gas Inc | Edmond, OK 73013 | Oil & Gas Operator | Dec 2025 |
| 523 | Wheeler Energy Co. | Tulsa, OK 74101 | Oil & Gas Operator | Nov 2025 |
| 524 | White Stride LLC | Piedmont, OK 73078 | Oil & Gas Operator | Feb 2026 |
| 525 | Wilbanks Exploration Inc | Denver, CO 80202 | Oil & Gas Operator | May 2002 |
| 526 | Wildhorse Oil & Gas Corporation | Ardmore, OK 73402 | Oil & Gas Operator | May 2019 |
| 527 | Wildhorse Operating Company | Ardmore, OK 73402 | Oil & Gas Operator | Feb 2026 |
| 528 | Wilham Investments, Inc. | Pampa, TX 79065 | Oil & Gas Operator | Jan 2020 |
| 529 | Will Energy Corporation | Dallas, TX 75201 | Oil & Gas Operator | Nov 2025 |
| 530 | Williford Energy Company | Tulsa, OK 74135 | Oil & Gas Operator | Feb 2026 |
| 531 | Williford Petroleum, L.L.C. | Green CV SPGS, FL 32043 | Oil & Gas Operator | Feb 2026 |
| 532 | Willow Creek Resources, Inc. | Midland, TX 79702 | Oil & Gas Operator | Feb 2009 |
| 533 | Wilson Energy LLC | Marietta, OH 45750 | Oil & Gas Operator | Dec 2024 |
| 534 | Wilson Operating Company LLC | Tulsa, OK 74105 | Oil & Gas Operator | Feb 2026 |
| 535 | Winchester Energy, LLC | Houston, TX 77056 | Oil & Gas Operator | Feb 2026 |
| 536 | Winright Resources Operating,LLC | Houston, TX 77007 | Oil & Gas Operator | Feb 2026 |
| 537 | Wischkaemper, Kenneth | Shamrock, TX 79079 | Oil & Gas Operator | Feb 2026 |
| 538 | Wolf Creek Exploration Company | Amarillo, TX 79159 | Oil & Gas Operator | Aug 2000 |
| 539 | WPH Operating Company | Amarillo, TX 79105 | Oil & Gas Operator | Mar 2017 |
| 540 | Wright Trucking, Inc. | Weatherford, OK 73096 | Oil & Gas Operator | Feb 2019 |
| 541 | Wynn-Crosby Energy, Inc. | Houston, TX 77002 | Oil & Gas Operator | May 2005 |
| 542 | Wynn-Crosby Operating, LTD. | Dallas, TX 75201 | Oil & Gas Operator | Feb 2026 |
| 543 | XTO Energy Inc. | Spring, TX 77389 | Oil & Gas Operator | Feb 2026 |