| 801 | O'Brien Energy Resources Corp | Portsmouth, NH 03801 | Oil & Gas Operator | Jul 2026 |
| 802 | Ocean Energy Inc | Houston, TX 77002 | Oil & Gas Operator | Aug 2003 |
| 803 | Oci LLC | Thermopolis, WY 82443 | Oil Operator | Jan 2024 |
| 804 | Oedekoven Amerifields Resources LLC | Sugar Land, TX 77478 | Oil Operator | Apr 2026 |
| 805 | Oedekoven Water & Hot Oil | Recluse, WY 82725 | Oil & Gas Operator | Jun 2026 |
| 806 | Oil & Gas Acquisition Group Inc | Austin, TX 78716 | Oil & Gas Operator | May 2003 |
| 807 | Oil Mountain Energy Inc | Casper, WY 82609 | Oil Operator | Jun 2026 |
| 808 | Oildigger Resources Fund L LLLP | Billings, MT 59101 | Oil & Gas Operator | Jun 2026 |
| 809 | Oilfield Consultants | | Oil & Gas Operator | Dec 1987 |
| 810 | Oilfield Salvage & Service Company | Littleton, CO 80120 | Oil & Gas Operator | May 2026 |
| 811 | Okie Crude Company | Tulsa, OK 74103 | Oil & Gas Operator | Apr 2026 |
| 812 | Oklahoma Oil Company | Dallas, TX 75206 | Oil & Gas Operator | Aug 2013 |
| 813 | Okmar Oil Company | Marietta, OH 45750 | Oil & Gas Operator | Jun 2005 |
| 814 | Okt Petroleum Company Inc | Oklahoma City, OK 73118-7425 | Oil & Gas Operator | Oct 2013 |
| 815 | Olds Oil Company | Casper, WY 82604 | Oil Operator | Jun 1988 |
| 816 | Olympic Exploration Inc | Denver, CO 80202 | Oil & Gas Operator | Jul 2004 |
| 817 | Omimex Petroleum Inc (Co) | Newcastle, WY 82701 | Oil & Gas Operator | May 2001 |
| 818 | Omimex Petroleum Inc (De) | Fort Worth, TX 76120 | Oil & Gas Operator | Aug 2020 |
| 819 | Omni Operating Company | Osage, WY 82723 | Oil & Gas Operator | Sep 2001 |
| 820 | Oneida Energy Corporation | Tulsa, OK 74137 | Oil & Gas Operator | Jul 2003 |
| 821 | Open Range Energy LLC | Jones, OK 73049-8744 | Oil & Gas Operator | Dec 2024 |
| 822 | Opes Production Inc | Buffalo, WY 82834 | Gas Operator | Mar 2015 |
| 823 | Orion Energy Partners LP | Denver, CO 80202 | Oil & Gas Operator | Nov 2010 |
| 824 | Oryx Energy Company | Dallas, TX 75221 | Oil & Gas Operator | May 2002 |
| 825 | Osage Hot Oil Service | Newcastle, WY 82701 | Oil & Gas Operator | Jul 1997 |
| 826 | Osage Operating Company LLC | Seattle, WA 98133 | Oil Operator | May 2006 |
| 827 | Osage Partners LLC | | Oil & Gas Operator | Jun 2026 |
| 828 | Osborn Heirs Company LTD | San Antonio, TX 78217 | Oil & Gas Operator | Mar 2026 |
| 829 | Ott Inc | Casper, WY 82602 | Oil Operator | Oct 2025 |
| 830 | Overland Resources LLC | Greenwood VIllage, CO 80111 | Oil & Gas Operator | Feb 2019 |
| 831 | Ovintiv USA Inc. | Denver, CO 80202 | Oil & Gas Operator | Jul 2026 |
| 832 | Oxbow Properties Inc | Centennial, CO 80122-1422 | Oil & Gas Operator | Jan 2025 |
| 833 | Oxford Exploration Company | Denver, CO 80237 | Oil & Gas Operator | Aug 1995 |
| 834 | Oxtex Inc | | Oil & Gas Operator | Oct 1989 |
| 835 | Oxy Petroleum Inc | | Oil & Gas Operator | Jan 1986 |
| 836 | Oxy USA Inc | Houston, TX 77046 | Oil & Gas Operator | Jul 2026 |
| 837 | P & M Petroleum Management LLC | Denver, CO 80202 | Oil & Gas Operator | Oct 2021 |
| 838 | P & P Producing Inc | Midland, TX 79702 | Oil & Gas Operator | Feb 2015 |
| 839 | P.O.&G. Operating, LLC | Houston, TX 77057 | Oil & Gas Operator | Jul 2026 |
| 840 | Pacific Enterprises Oil Co USA | Dallas, TX 75201 | Oil & Gas Operator | Feb 2001 |
| 841 | Pacific Transmission Supply | | Oil & Gas Operator | Dec 1987 |
| 842 | Pajaro Energy LLC | Santa Fe, NM 87501 | Oil & Gas Operator | Dec 2023 |
| 843 | Pal LLC | Gillette, WY 82718 | Oil Operator | Dec 2019 |
| 844 | Paladin Energy Partner LLC | Denver, CO 80201 | Oil & Gas Operator | Aug 2006 |
| 845 | Palo Petroleum, Inc. | Dallas, TX 75360 | Oil & Gas Operator | Jul 2026 |
| 846 | Pancanadian Petroleum Company | | Oil & Gas Operator | Oct 1989 |
| 847 | Panther Energy Company III LLC | Tulsa, OK 74136 | Oil & Gas Operator | Jul 2020 |
| 848 | Paoli Investors LTD | | Oil & Gas Operator | Aug 1985 |
| 849 | Par Oil Company Inc | Denver, CO 80201 | Oil & Gas Operator | Jun 2003 |
| 850 | Park Oil Properties LLC | Plano, TX 75025 | Oil Operator | Oct 2019 |
| 851 | Park Robert E | | Oil Operator | May 1983 |
| 852 | Parker & Parsley Producing LP | Midland, TX 79702 | Oil & Gas Operator | Oct 1997 |
| 853 | Pathfinder Energy Inc | Casper, WY 82605 | Oil & Gas Operator | May 2024 |
| 854 | Patina Oil & Gas Corporation | Denver, CO 80202 | Oil & Gas Operator | May 2016 |
| 855 | Patrick Petroleum Co. | Jackson, MI 49201 | Oil & Gas Operator | Nov 1993 |
| 856 | Patriot Energy Resources LLC | Golden, CO 80401 | Gas Operator | Aug 2014 |
| 857 | Patriot Production LLC | Southlake, TX 76092 | Oil & Gas Operator | Apr 2023 |
| 858 | PDS Resources LLC | | Oil & Gas Operator | May 2026 |
| 859 | Peabody Natural Gas LLC | Gillette, WY 82718 | Oil & Gas Operator | Apr 2026 |
| 860 | Peak Powder River Resources LLC | Durango, CO 81301 | Oil & Gas Operator | May 2026 |
| 861 | Peakview Oil Company LLC | Denver, CO 80202 | Gas Operator | May 2026 |
| 862 | Pearce Leonard | Manderson, WY 82432 | Oil Operator | Dec 1999 |
| 863 | Pearce Mary | | Oil Operator | Dec 1999 |
| 864 | Pearce Oil Company | Manderson, WY 82432 | Oil Operator | Jun 1999 |
| 865 | Pease Oil & Gas Company | Grand Junction, CO 81506 | Oil & Gas Operator | May 2000 |
| 866 | Pecos Development Corporation | San Antonio, TX 78209 | Oil Operator | Aug 1988 |
| 867 | Pedco Resources Company | Tulsa, OK 74170 | Oil & Gas Operator | Mar 2008 |
| 868 | Pedry J J | | Oil Operator | Sep 1989 |
| 869 | Pelican Dome Exploration | Harahan, LA 70123 | Oil & Gas Operator | Jun 1997 |
| 870 | Pendragon Energy Partners Inc | Midland, TX 79701 | Oil & Gas Operator | Nov 2009 |
| 871 | Pennaco Energy Incorporated | Gillette, WY 82718 | Oil & Gas Operator | Feb 2021 |
| 872 | Penneco Exploration Company Of Wyo LLC | Delmont, PA 15626 | Oil Operator | Aug 2021 |
| 873 | Pennzoil Company | Midland, TX 79710-0090 | Oil & Gas Operator | Mar 2000 |
| 874 | Petcon Associates LTD | Denver, CO 80202 | Oil & Gas Operator | Sep 2018 |
| 875 | Peters Walter J | | Oil & Gas Operator | Jul 1991 |
| 876 | Peterson Energy Management Inc | | Oil Operator | Aug 2010 |
| 877 | Peterson Energy Operating Inc | Loveland, CO 80537 | Oil & Gas Operator | May 2026 |
| 878 | Petra Petroleum Inc | Littleton, CO 80160-0319 | Oil & Gas Operator | Jun 2005 |
| 879 | Petral Exploration Inc LLC | Denver, CO 80217 | Oil & Gas Operator | May 2007 |
| 880 | Petro Energy Inc | Farmington, NM 87499 | Oil & Gas Operator | Sep 2025 |
| 881 | Petro Search Exploration Corp | | Oil & Gas Operator | May 1993 |
| 882 | Petro-Canada Resources (USA) Inc | Denver, CO 80202-472 | Oil & Gas Operator | Feb 2010 |
| 883 | Petro-Hunt Corporation | Dallas, TX 75201 | Oil & Gas Operator | Jun 2003 |
| 884 | Petro-Hunt, L.L.C. | Dallas, TX 75201 | Oil & Gas Operator | Jul 2026 |
| 885 | Petro-Lewis Corp. | | Oil & Gas Operator | Feb 1994 |
| 886 | Petrocarbon Energy Corporation | | Oil Operator | Sep 1996 |
| 887 | Petrocarbon Energy Trust | | Oil Operator | Sep 1996 |
| 888 | Petrocorp Incorporated | Tulsa, OK 74170 | Oil & Gas Operator | Nov 2021 |
| 889 | Petrogulf Corporation | Denver, CO 80202 | Oil & Gas Operator | Jul 2026 |
| 890 | Petrohawk Operating Company | Houston, TX 77056 | Oil & Gas Operator | Oct 2021 |
| 891 | Petrolero Corp. | San Antonio, TX 78205 | Oil & Gas Operator | Feb 1998 |
| 892 | Petroleum Corp Of Delaware The | | Oil & Gas Operator | May 1991 |
| 893 | Petroleum Inc | Wichita, KS 67202 | Oil & Gas Operator | Oct 2021 |
| 894 | Petroleum Management LLC | Platteville, CO 80651 | Oil & Gas Operator | Mar 2011 |
| 895 | Petroleum Products Inc | | Oil Operator | Jun 1996 |
| 896 | Petroleum Resource Management Corp | Denver, CO 80203 | Oil & Gas Operator | May 2026 |
| 897 | Petrorep Inc | | Oil Operator | Oct 1998 |
| 898 | Petrox Resources Inc | Meeker, CO 81641 | Oil & Gas Operator | Jun 2026 |
| 899 | PGC LLC | Newcastle, WY 92701 | Oil Operator | Oct 2023 |
| 900 | Phillips Petroleum Company | Houston, TX 77251 | Oil & Gas Operator | Mar 2013 |