| 6601 | Younger Enterprises Inc | Ada, OK 74821-1882 | Oil Operator | Jan 2003 |
| 6602 | Z G Operating LLC | Oklahoma City, OK 73134-5038 | Oil & Gas Operator | Nov 2009 |
| 6603 | Z G Exploration Inc | Oklahoma City, OK 73112 | Oil & Gas Operator | Feb 2005 |
| 6604 | Zafar Oil & Gas, Inc. | Oklahoma City, OK 73132 | Oil Operator | Aug 2013 |
| 6605 | Zap Oil Company | Nowata, OK 74048-2640 | Oil & Gas Operator | Nov 2005 |
| 6606 | Zarvona Energy LLC | Houston, TX 77002 | Oil & Gas Operator | Jul 2026 |
| 6607 | Zca Gas Gathering Co., Inc. | Bartlesville, OK 74003 | Oil & Gas Operator | Apr 2020 |
| 6608 | Zeal Production Company | Sperry, OK 74073-4714 | Oil & Gas Operator | May 2026 |
| 6609 | Zeiders Bros. Oil & Gas Company, L.L.C. | Edmond, OK 73003 | Oil & Gas Operator | Apr 2026 |
| 6610 | Zenergy Inc | Tulsa, OK 74136 | Oil & Gas Operator | May 2026 |
| 6611 | Zenith Oil & Gas, LLC | Kilgore, TX 75663 | Oil & Gas Operator | Apr 2026 |
| 6612 | Zephyr Operating Co LLC | Oklahoma City, OK 73118-6035 | Oil & Gas Operator | Apr 2026 |
| 6613 | Zephyr SWD LLC | Oklahoma City, OK 73118-6035 | Oil Operator | May 2026 |
| 6614 | Zilkha Energy Company | Houston, TX 77046 | Oil & Gas Operator | Oct 2002 |
| 6615 | Zim Energy Corporation | Tulsa, OK 74153 | Oil & Gas Operator | Jan 1998 |
| 6616 | Zimtex Energy LLC | Perryton, TX 79070-5818 | Oil & Gas Operator | Nov 2017 |
| 6617 | Zinke & Trumbo LTD | Tulsa, OK 74105 | Oil & Gas Operator | Sep 2017 |
| 6618 | Zion Energy Corporation | Peru, KS 67360 | Oil Operator | Aug 2000 |
| 6619 | Zollinger Veldon | Cresent, OK 73028 | Oil & Gas Operator | Apr 2009 |
| 6620 | Zollinger Veldon Inc | Crescent, OK 73028-9280 | Oil & Gas Operator | Nov 2018 |
| 6621 | ZP Disposal Systems LLC | Kingfisher, OK 73750 | Oil Operator | May 2026 |
| 6622 | Zuhone William H | Mattoon, IL 61938-4019 | Oil & Gas Operator | Jan 2015 |
| 6623 | Zumyers Inc | Newalla, OK 74857-0259 | Oil Operator | Apr 2003 |
| 6624 | ZZ Energy LLC | Norman, OK 73070 | Gas Operator | Apr 2026 |
| 6625 | Zzron Inc. | Midland, TX 79704 | Oil & Gas Operator | Aug 2003 |