| 601 | Westland Oil Development Corp. | Conroe, TX 77305 | Oil & Gas Operator | Mar 2008 |
| 602 | Westport Oil & Gas Company LP | The Woodlands, TX 77380 | Oil & Gas Operator | Feb 2007 |
| 603 | White Oak Operating Company LLC | Houston, TX 77077 | Oil & Gas Operator | Oct 2025 |
| 604 | White Stride LLC | Piedmont, OK 73078 | Oil & Gas Operator | Oct 2025 |
| 605 | Whiting Oil And Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Oct 2025 |
| 606 | Whiting Petroleum Corporation | Denver, CO 80290 | Oil & Gas Operator | Jan 2025 |
| 607 | Wilcox Operating Corporation | Shreveport, LA 71115 | Oil & Gas Operator | Oct 2025 |
| 608 | Wild Cat Operating Company | Victoria, TX 77903 | Oil & Gas Operator | Mar 2008 |
| 609 | Williams-Cody, Inc. | Houston, TX 77060 | Oil & Gas Operator | May 1994 |
| 610 | Williamson Oil & Gas, Inc. | Shreveport, LA 71166 | Oil & Gas Operator | Dec 2024 |
| 611 | Wilson Hydrocarbon Inc. | Houston, TX 77066 | Oil & Gas Operator | Oct 2025 |
| 612 | Winn Exploration Co., Inc. | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Oct 2025 |
| 613 | Wofford, C. J. | El Campo, TX 77437 | Oil & Gas Operator | Oct 2025 |
| 614 | Wolfson, I. J. | Wichita Falls, TX 76301 | Oil & Gas Operator | Apr 2002 |
| 615 | Wood Hi Co., Inc. | Victoria, TX 77902 | Oil & Gas Operator | Dec 2004 |
| 616 | Xog Operating LLC | Midland, TX 79702 | Oil & Gas Operator | Oct 2025 |
| 617 | Yuma Petroleum Company | Houston, TX 77027 | Oil & Gas Operator | Aug 2002 |
| 618 | Zachry Exploration, Inc. | San Antonio, TX 78205 | Oil & Gas Operator | Oct 2025 |
| 619 | Zachry Exploration, LLC | San Antonio, TX 78224 | Oil & Gas Operator | Oct 2025 |
| 620 | Zachry Exploration, LTD. | San Antonio, TX 78205 | Oil & Gas Operator | Jan 2009 |