| 1 | O S & J Operatin | | Oil Operator | Nov 1984 |
| 2 | O'Brien Energy Company | Shreveport, LA 71136 | Oil & Gas Operator | Sep 2019 |
| 3 | O'Brien Energy Resources Corp | Portsmouth, NH 03801 | Oil & Gas Operator | Oct 2025 |
| 4 | O'Brien Resources LLC | Shreveport, LA 71136 | Oil Operator | Nov 2017 |
| 5 | O'Connell, James P. | Vacaville, CA 95687 | Oil Operator | Nov 2009 |
| 6 | O'Hare Energy Co | | Oil Operator | Dec 1983 |
| 7 | Oak Ridge LLC | Wellsville, KS 66092 | Oil Operator | Dec 2019 |
| 8 | Oaks Petroleum I | | Oil Operator | Jul 1987 |
| 9 | Oakwood Resources, Inc. | Dallas, TX 75374 | Oil & Gas Operator | May 1998 |
| 10 | Oast, Thomas H. | Greenville, NC 27835 | Oil Operator | Nov 1985 |
| 11 | Occidental Energy Marketing, Inc. | Houston, TX 77227 | Gas Operator | Sep 2015 |
| 12 | Ocean Energy Resources Inc. | Houston, TX 77002 | Oil & Gas Operator | Mar 2025 |
| 13 | Ocfiw Oil Company, Inc. | Hartington, NE 68739 | Oil & Gas Operator | Dec 2009 |
| 14 | Ogh Oil Company | | Oil Operator | Sep 1995 |
| 15 | Ohio Kentucky Oil Corporation | Lexington, KY 40503 | Oil & Gas Operator | Dec 2023 |
| 16 | Oil & Gas Producers, Inc. | Topeka, KS 66604 | Oil Operator | Jun 2004 |
| 17 | Oil & Gas Servic | | Oil Operator | Jun 1983 |
| 18 | Oil Capital Corporation | Littleton, CO 80122 | Gas Operator | May 2009 |
| 19 | Oil Company Of America, Inc. | Hays, KS 67601 | Oil Operator | Dec 2009 |
| 20 | Oil Drillers & D | | Oil & Gas Operator | Feb 1992 |
| 21 | Oil Equipment As | | Gas Operator | Jun 1989 |
| 22 | Oil Field Manage | | Oil Operator | Jun 1991 |
| 23 | Oil Gas Management, Inc. | Kansas City, MO 64106 | Oil Operator | Apr 2011 |
| 24 | Oil Internationa | | Oil Operator | Jun 1986 |
| 25 | Oil Lift, Incorporated | Metairie, LA 70002 | Oil & Gas Operator | Apr 2020 |
| 26 | Oil Partners | Salina, KS 67401 | Oil Operator | Jun 2001 |
| 27 | Oil Partners, LLC | Salina, KS 67401 | Oil Operator | Jun 2025 |
| 28 | Oil Producers In | | Oil & Gas Operator | Dec 1996 |
| 29 | Oil Producers, Inc. Of Kansas | Wichita, KS 67206 | Oil & Gas Operator | Oct 2025 |
| 30 | Oil Production S | | Oil Operator | Sep 1993 |
| 31 | Oil Prop Company | | Oil & Gas Operator | Sep 1995 |
| 32 | Oil Prop Investm | | Oil Operator | Dec 1995 |
| 33 | Oil Properties Co., Inc. | Wichita, KS 67208 | Gas Operator | Dec 2009 |
| 34 | Oil Property Man | | Oil & Gas Operator | Jun 1995 |
| 35 | Oil Property Management, Inc. | Attica, KS 67009 | Oil & Gas Operator | Feb 2021 |
| 36 | Oil Tech Producers Corporation | Moundridge, KS 67107 | Gas Operator | Jun 2025 |
| 37 | Oil-Tech Prod Co | | Oil & Gas Operator | Oct 1992 |
| 38 | Oilfield Search | | Oil Operator | Mar 1990 |
| 39 | Oilfield Services, LLC | Winfield, KS 67156 | Oil Operator | Nov 2017 |
| 40 | Oilfield Truck Service | | Oil Operator | Jun 2014 |
| 41 | Oilwell Operator | | Gas Operator | Dec 1994 |
| 42 | Oklahoma Energy & Exploration, Inc. | Tulsa, OK 74114 | Oil Operator | Jan 1996 |
| 43 | Oklahoma Rig & Salvage, Inc. | Oklahoma City, OK 73114 | Oil & Gas Operator | Mar 2015 |
| 44 | Okmar Oil Compan | | Oil & Gas Operator | Feb 1995 |
| 45 | Okmar Oil Company | Marietta, OH 45750 | Oil & Gas Operator | Jun 2005 |
| 46 | Okt Resources, LLC | Edmond, OK 73013 | Oil & Gas Operator | Oct 2025 |
| 47 | Ol' Oily LLC | | Oil Operator | Jun 2025 |
| 48 | Oleum Incorporat | | Gas Operator | Dec 1990 |
| 49 | Olson D Producti | | Oil Operator | Jul 1994 |
| 50 | Olson-Anderson Lease | | Oil Operator | Mar 2018 |
| 51 | Olympic Oil, Inc. | Hutchinson, KS 67502 | Oil & Gas Operator | May 2025 |
| 52 | Olympic Petroleu | | Oil & Gas Operator | Jul 1993 |
| 53 | Omega Enterprise | | Oil Operator | Sep 1990 |
| 54 | One Source Financial Services Inc. | McAllen, TX 78501 | Gas Operator | Dec 2019 |
| 55 | Oneok Bushton Proces | | Gas Operator | Mar 2007 |
| 56 | Oneok Energy Service | | Gas Operator | Dec 2008 |
| 57 | Oneok Exploratio | | Oil & Gas Operator | Mar 1995 |
| 58 | Oneok Field Services Company | Tulsa, OK 74103 | Oil & Gas Operator | Jul 2022 |
| 59 | Oneok Gas Processing LLC | Tulsa, OK 74103 | Oil & Gas Operator | May 2018 |
| 60 | Oneok Resources Company | Tulsa, OK 74102 | Oil & Gas Operator | Feb 2017 |
| 61 | Onnen, Gerhard E. | Yates Center, KS 66783 | Oil Operator | Feb 2002 |
| 62 | Onshore, L.L.C. | Wichita, KS 67205 | Oil & Gas Operator | Dec 2009 |
| 63 | Onyxx Oil Corpor | | Oil Operator | Jul 1992 |
| 64 | Oolite Energy Corp | Amarillo, TX 79105 | Oil & Gas Operator | Apr 2022 |
| 65 | Opco LLC | Chase, KS 67524 | Oil Operator | Dec 2019 |
| 66 | Opdycke Lease Partners, A General Partnership | Russell, KS 67665 | Oil Operator | Jun 2025 |
| 67 | Opef Partnership, A General Partnership | Overland Park, KS 66221 | Oil Operator | Dec 2011 |
| 68 | Orca Operating Company LLC | Houston, TX 77056 | Oil & Gas Operator | Jul 2025 |
| 69 | Oryx Energy Comp | | Oil & Gas Operator | Apr 1991 |
| 70 | Oryx Energy Company | Dallas, TX 75221 | Oil & Gas Operator | May 2002 |
| 71 | Osage Energy, LLC | Colony, KS 66015 | Oil Operator | Nov 2023 |
| 72 | Osage Resources, LLC | Wichita, KS 67202 | Oil & Gas Operator | May 2025 |
| 73 | Osborn Energy, L.L.C. | Bucyrus, KS 66013 | Oil & Gas Operator | Jul 2017 |
| 74 | Osborn Heirs Com | | Oil & Gas Operator | May 1995 |
| 75 | Osborn Heirs Company LTD | San Antonio, TX 78217 | Oil & Gas Operator | Jun 2025 |
| 76 | Osborn Oil & Gas | | Oil & Gas Operator | Jun 1991 |
| 77 | Osci Oil And Gas, Inc. | Parker, KS 66072 | Oil Operator | Jun 1998 |
| 78 | Oswego Oil & Gas | | Oil & Gas Operator | Jun 1984 |
| 79 | Outback Oil, Inc. | Pratt, KS 67124 | Gas Operator | Sep 2019 |
| 80 | Outlaw Well Service LLC | Hays, KS 67601 | Oil Operator | Jun 2025 |
| 81 | Overland Exploration Company | | Oil Operator | May 2025 |
| 82 | Owen'S Pumping Service | | Oil Operator | Jun 2025 |
| 83 | Owen, Matthew | Hamilton, KS 66853 | Oil Operator | Sep 2016 |
| 84 | Owens Oil | | Oil Operator | Dec 2000 |
| 85 | Owens Oil Company | Iowa Park, TX 76367 | Oil & Gas Operator | Sep 2008 |
| 86 | Owens Oil Company, LLC | Yates Center, KS 66783 | Oil Operator | Jun 2025 |
| 87 | Owens Petroleum | | Oil Operator | May 2006 |
| 88 | Owens Petroleum LLC | Yates Center, KS 66783 | Oil & Gas Operator | Jun 2025 |
| 89 | Owi Operating Co. LC | Ottawa, KS 66067 | Oil & Gas Operator | Dec 2009 |
| 90 | Own Resources Operating LLC | The Woodlands, TX 77381 | Oil & Gas Operator | Jul 2025 |
| 91 | Oxbow Oil Company,A Kansas General Partnership | Grenola, KS 67346 | Oil Operator | Apr 2015 |
| 92 | Oxford Explorati | | Oil & Gas Operator | Mar 1993 |
| 93 | Oxford Exploration | | Oil Operator | Apr 1988 |
| 94 | Oxy USA | | Oil Operator | Apr 1992 |
| 95 | Oxy USA Inc | Houston, TX 77046 | Oil & Gas Operator | Oct 2025 |
| 96 | Ozark Enterprise | | Oil Operator | Nov 1990 |