| 1 | Rainbow Oil Company | | Oil & Gas Operator | Aug 1999 |
| 2 | Rainbow Resources, Inc. | Kilgore, TX 75663 | Oil & Gas Operator | Aug 2007 |
| 3 | Ranch Oil Company | West Linn, OR 97068 | Oil & Gas Operator | Aug 2025 |
| 4 | Ranger Holdings Co | | Oil & Gas Operator | Jul 1993 |
| 5 | RB Operating Company | Shawnee, OK 74802-1488 | Oil & Gas Operator | Apr 2015 |
| 6 | Reading & Bates Petroleum | | Oil & Gas Operator | Apr 1989 |
| 7 | Red Tiger Oil & Gas LLC | Gillette, WY 82718 | Oil & Gas Operator | Jul 2025 |
| 8 | Redbud E & P, Inc. | Giddings, TX 78942 | Oil & Gas Operator | Oct 2025 |
| 9 | Redstone Resources Inc | Newcastle, WY 82701 | Gas Operator | Dec 2010 |
| 10 | Reef Exploration Inc | Denver, CO 80202 | Oil & Gas Operator | Feb 2007 |
| 11 | Reliance Resources Inc | Houston, TX 77007 | Gas Operator | Jun 2012 |
| 12 | Renor Exploration | Englewood, CO 80111 | Oil Operator | Feb 2001 |
| 13 | Reserve Oil & Gas Company | | Oil & Gas Operator | Jul 1981 |
| 14 | Resolute Wyoming Inc | Denver, CO 80203 | Oil & Gas Operator | May 2018 |
| 15 | Resource Enterprises Inc | Salt Lake City, UT 84108 | Gas Operator | Dec 1990 |
| 16 | Resources Investment Corp | Denver, CO 80202 | Oil & Gas Operator | Sep 2018 |
| 17 | Reunion Energy Company | Houston, TX 77056 | Oil & Gas Operator | May 1996 |
| 18 | Richardson Operating Company | Denver, CO 80237 | Oil & Gas Operator | Jul 2025 |
| 19 | Ridge Energy Partners LLC | Casper, WY 82601 | Oil Operator | Dec 2018 |
| 20 | Rim Operating, Inc. | Englewood, CO 80112 | Oil & Gas Operator | Oct 2025 |
| 21 | Rme Petroleum Company | Houston, TX 77251 | Oil & Gas Operator | Nov 2016 |
| 22 | Rochelle Oil & Gas | Gillette, WY 82717 | Oil & Gas Operator | Mar 2024 |
| 23 | Rock Creek Resources LLC | Englewood, CO 80112 | Oil & Gas Operator | Dec 2021 |
| 24 | Rock Oil Corporation | Lawrence, KS 66046 | Oil Operator | Oct 2004 |
| 25 | Rockies Resources Holdings LLC | Lakewood, CO 80228 | Oil & Gas Operator | Jul 2025 |
| 26 | Rocky Mountain Gas Inc | Sheridan, WY 82801 | Gas Operator | Nov 2009 |
| 27 | Roemer Oil Company | Denver, CO 80202 | Oil & Gas Operator | Nov 1998 |
| 28 | Roff Operating Company LLC | Houston, TX 77002 | Oil & Gas Operator | Oct 2025 |
| 29 | Royal Resources Exploration | | Oil & Gas Operator | Mar 1984 |
| 30 | Ruby Drilling Company Inc | Gillette, WY 82718 | Oil Operator | Oct 2007 |