| 401 | Walter Oil & Gas Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2025 |
| 402 | Waters Eng. & Operating, Inc. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Sep 2013 |
| 403 | Westech Energy Corporation | Denver, CO 80237 | Oil & Gas Operator | Mar 2011 |
| 404 | Western Gas Resources Storage | Denver, CO 80234 | Oil & Gas Operator | Jun 1999 |
| 405 | Western Gulf Oil & Gas Inc. | Dallas, TX 75360 | Oil & Gas Operator | Jul 2000 |
| 406 | Western Oil Producers Inc | Roswell, NM 88202 | Oil & Gas Operator | Jul 2005 |
| 407 | Westland Oil Development Corp. | Conroe, TX 77305 | Oil & Gas Operator | Mar 2008 |
| 408 | Will-Drill Production Co., Inc. | Shreveport, LA 71105 | Oil & Gas Operator | Mar 2025 |
| 409 | Wing Corporation | Houston, TX 77002 | Oil & Gas Operator | Jun 2000 |
| 410 | Wood Energy Corporation | Baytown, TX 77520 | Oil & Gas Operator | Jun 1999 |
| 411 | XTO Energy Inc. | Spring, TX 77389 | Oil & Gas Operator | Mar 2025 |
| 412 | Yentzen Investments, Inc. | Sugar Land, TX 77478 | Oil Operator | May 1993 |
| 413 | Yuma E & P Company, Inc. | Houston, TX 77027 | Oil & Gas Operator | Mar 2025 |
| 414 | Yuma Petroleum Company | Houston, TX 77027 | Oil & Gas Operator | Aug 2002 |
| 415 | Zachry Exploration, Inc. | San Antonio, TX 78205 | Oil & Gas Operator | Mar 2025 |
| 416 | Zachry Exploration, LLC | San Antonio, TX 78224 | Oil & Gas Operator | Mar 2025 |
| 417 | Zachry Exploration, LTD. | San Antonio, TX 78205 | Oil & Gas Operator | Jan 2009 |
| 418 | Zinke & Trumbo, Inc. | Tulsa, OK 74136 | Oil & Gas Operator | Mar 2007 |
| 419 | Zinn Petroleum Co. | Houston, TX 77024 | Oil & Gas Operator | Nov 2021 |
| 420 | ZK Petroleum Co., L.L.C. | Houston, TX 77057 | Oil Operator | Mar 2025 |