| 1 | O'Brien Energy Resources Corp | Portsmouth, NH 03801 | Oil & Gas Operator | Oct 2025 |
| 2 | Ocean Energy Inc Ndba Devon Louisiana Corp | | Oil & Gas Operator | Jul 2001 |
| 3 | Ogris Operating, LLC | Midland, TX 79710 | Oil & Gas Operator | Oct 2025 |
| 4 | Oilfield Operating Company | Cushing, OK 74023-1347 | Oil & Gas Operator | Jan 2018 |
| 5 | Oilfield Salvage & Service Company | Littleton, CO 80120 | Oil & Gas Operator | Aug 2025 |
| 6 | Omimex Petroleum Inc | Fort Worth, TX 76120 | Oil & Gas Operator | Aug 2022 |
| 7 | Oneok Resources Company | Tulsa, OK 74102 | Oil & Gas Operator | Feb 2017 |
| 8 | Organic Energy Company LLC | | Oil & Gas Operator | Sep 2025 |
| 9 | Orion Energy Partners LP | Denver, CO 80202 | Oil & Gas Operator | Nov 2010 |
| 10 | Orr Energy LLC | | Oil & Gas Operator | Nov 2012 |
| 11 | Overland Resources LLC | Greenwood VIllage, CO 80111 | Oil & Gas Operator | Jul 2019 |
| 12 | Own Resources Operating LLC | The Woodlands, TX 77381 | Oil & Gas Operator | Jul 2025 |
| 13 | Oxbow Properties Inc | Centennial, CO 80122-1422 | Oil & Gas Operator | Jan 2025 |
| 14 | Oxy USA Inc | Houston, TX 77046 | Oil & Gas Operator | Oct 2025 |
| 15 | Oxy USA WTP LP | Houston, TX 77046 | Oil & Gas Operator | Oct 2025 |