| 601 | Degroot, Garry | South Dayton, NY 14138 | Gas Operator | Dec 2024 |
| 602 | Deguello Operating LLC | Kilgore, TX 75663 | Oil & Gas Operator | Oct 2025 |
| 603 | Dehart Company (The) | Ardmore, OK 73402 | Oil & Gas Operator | Jul 2025 |
| 604 | Deisenroth M Craig | Tulsa, OK 74104-6511 | Oil & Gas Operator | Jun 2025 |
| 605 | Deitz Edith | Clarion, PA 16214-9416 | Oil & Gas Operator | Dec 2009 |
| 606 | Deitz Gas & Oil Inc | Clarion, PA 16214-3215 | Oil & Gas Operator | Dec 2024 |
| 607 | Dejong John B | | Oil Operator | Dec 2024 |
| 608 | Dejour Energy (USA) Corporation | | Oil & Gas Operator | Jun 2014 |
| 609 | Deka Exploration Inc | Oklahoma City, OK 73113-0057 | Oil & Gas Operator | Nov 2019 |
| 610 | Dekalb Energy Company | Oklahoma City, OK 73134 | Oil & Gas Operator | Oct 1996 |
| 611 | Dekasco, Inc. | | Oil & Gas Operator | May 1990 |
| 612 | Del Amo Energy Co. | | Oil & Gas Operator | Dec 1987 |
| 613 | Del Energy, Inc | | Oil Operator | Dec 2014 |
| 614 | Del Mar | Holliday, TX 76366 | Oil & Gas Operator | Oct 2025 |
| 615 | Del Mar Energy, Inc. | Van Alstyne, TX 75495 | Oil & Gas Operator | Oct 2025 |
| 616 | Del Mar Exploration Company | Houston, TX 77006 | Oil & Gas Operator | Jan 2014 |
| 617 | Del Oil & Gas Corp | | Oil Operator | Jul 1981 |
| 618 | Del Petroleum Corporation | Dallas, TX 75219 | Oil & Gas Operator | Jan 2012 |
| 619 | Del Rio Production Co. | Gainesville, TX 76240 | Oil Operator | Mar 2019 |
| 620 | Del-Rio Resources Inc | Vernal, UT 84079 | Oil & Gas Operator | Jan 2018 |
| 621 | Delaware Davis Petroleum Corp. | Houston, TX 77056 | Oil & Gas Operator | Jan 2000 |
| 622 | Delaware Dyche Corp. | Hutchinson, KS 67501 | Oil Operator | Jan 2010 |
| 623 | Delaware Ecco Petroleum Inc. | Rockwall, TX 75087 | Oil & Gas Operator | Jul 2001 |
| 624 | Delbert A. Dodson | | Oil Operator | Aug 2002 |
| 625 | Delcar, Inc. | San Antonio, TX 78209 | Oil & Gas Operator | Oct 1995 |
| 626 | Delco Operating Company LP | Houston, TX 77056 | Oil & Gas Operator | May 2020 |
| 627 | Delek Energy Systems Us Inc | Denver, CO 80202 | Oil & Gas Operator | Oct 2011 |
| 628 | Delfin Operating, LLC | Dallas, TX 75243 | Oil & Gas Operator | Oct 2025 |
| 629 | Delgado, Emil A | San Antonio, TX 78223 | Oil & Gas Operator | Sep 2016 |
| 630 | Delhi Gas Pipeli | | Gas Operator | Aug 1998 |
| 631 | Delhi Gas Pipeline Corporation | Palestine, TX 75802 | Oil & Gas Operator | Feb 1998 |
| 632 | Delhi Pipeline | | Oil & Gas Operator | Sep 1999 |
| 633 | Delhi-Taylor Oil Corp | | Oil & Gas Operator | Dec 1974 |
| 634 | Delhi-Trading LLC | Durango, CO 81301 | Oil & Gas Operator | Aug 2025 |
| 635 | Dell Charles E | Cleveland, OK 74020-0090 | Oil & Gas Operator | Feb 2015 |
| 636 | Dell-Ray Investments, Inc. | Nickerson, KS 67561 | Oil Operator | Dec 2019 |
| 637 | Delmar Operating, Inc. | Houston, TX 77010 | Oil & Gas Operator | Oct 1996 |
| 638 | Delone, M S | El Dorado, AR 71730 | Oil & Gas Operator | Dec 2024 |
| 639 | Delong Oil & Gas Services, Inc. | Cushing, OK 74023 | Oil & Gas Operator | Dec 2024 |
| 640 | Delong Ralph J | Sapulpa, OK 74066 | Oil & Gas Operator | Nov 2005 |
| 641 | Delong, Horace | Pleasanton, TX 78064 | Oil & Gas Operator | Oct 2025 |
| 642 | Delong, Ralph S | | Oil & Gas Operator | Jun 2025 |
| 643 | Delozier, Orval & Stevens, Floyd, A General Partnership | Dewey, OK 74029 | Oil Operator | Nov 2009 |
| 644 | Delphi International, Inc. | Tulsa, OK 74104 | Oil Operator | Jul 2025 |
| 645 | Delphi Oil And Gas LLC | Macomb, OK 74852 | Oil Operator | May 2025 |
| 646 | Delphi Oil, Inc. | | Oil & Gas Operator | Jul 2025 |
| 647 | Delray Oil, Inc. | San Antonio, TX 78209 | Oil & Gas Operator | Oct 2025 |
| 648 | Delta C02, LLC | Breckenridge, TX 76424 | Oil & Gas Operator | Jul 2021 |
| 649 | Delta D Operations | Wilson, OK 73463 | Oil & Gas Operator | Jul 2014 |
| 650 | Delta D Operations Inc | Ardmore, OK 73401-8678 | Oil & Gas Operator | Apr 2014 |
| 651 | Delta Development Co. Inc. | | Oil & Gas Operator | Dec 1988 |
| 652 | Delta Energy Resources, Inc. | | Oil & Gas Operator | Jun 1990 |
| 653 | Delta Expl.& Development Corp. | | Oil & Gas Operator | Jan 2025 |
| 654 | Delta Exploration Company Inc | Denver, CO 80202 | Oil & Gas Operator | Oct 2025 |
| 655 | Delta Exploration, LLC | Fredericksbrg, TX 78624 | Oil Operator | Oct 2025 |
| 656 | Delta Natural Gas Co, Inc | Winchester, KY 40391 | Oil Operator | Dec 2023 |
| 657 | Delta Oil | Holliday, TX 76366 | Oil & Gas Operator | Sep 2005 |
| 658 | Delta Oil & Gas Company | Breckenridge, TX 76424 | Oil & Gas Operator | Apr 2003 |
| 659 | Delta Oil & Gas LTD. | Breckenridge, TX 76424 | Oil & Gas Operator | Oct 2025 |
| 660 | Delta Oil Co Inc | | Oil & Gas Operator | Oct 2023 |
| 661 | Delta Oil Co Inc And Great Lakes Niagaran | | Oil & Gas Operator | Dec 1987 |
| 662 | Delta Oil Corp | | Oil & Gas Operator | Dec 2005 |
| 663 | Delta Operating Company | | Oil Operator | Mar 1987 |
| 664 | Delta Operating Corporation | | Oil & Gas Operator | Feb 2024 |
| 665 | Delta Petro Corp Of Colorado | Houston, TX 77010-3089 | Gas Operator | Dec 2003 |
| 666 | Delta Petroleum Company | Houston, TX 77267 | Oil Operator | Aug 1996 |
| 667 | Delta Petroleum Corp | Denver, CO 80202 | Oil & Gas Operator | Dec 2024 |
| 668 | Delta Petroleum Corp Of Co | | Oil & Gas Operator | Oct 2010 |
| 669 | Delta Petroleum Inc | Houston, TX 77269-1007 | Oil & Gas Operator | May 2009 |
| 670 | Delta Producers, Inc | Greenville, MS 38703 | Oil & Gas Operator | Dec 2023 |
| 671 | Delta Producing Corporation | | Oil & Gas Operator | Dec 1996 |
| 672 | Delta Production Services, LLC | | Oil & Gas Operator | Aug 2002 |
| 673 | Delta Royalties LLC | | Oil & Gas Operator | Dec 2024 |
| 674 | Delta Sierra Oil & Gas LLC | | Gas Operator | Jan 2018 |
| 675 | Deltaus Corporation | | Oil & Gas Operator | Oct 1985 |
| 676 | Deltex Minerals Inc. | Peachtree Cty, GA 30269 | Oil & Gas Operator | Oct 2025 |
| 677 | Deltex Petroleum | | Oil Operator | Nov 1994 |
| 678 | Delwintex Oil & Gas Prop., Inc. | Lubbock, TX 79423 | Oil & Gas Operator | Aug 2003 |
| 679 | Dem Operations Inc | Lamont, OK 74643-5010 | Oil & Gas Operator | Jul 2025 |
| 680 | Demambro, Gene Brian | Mayville, NY 14757 | Gas Operator | Dec 2024 |
| 681 | Demand Energy, Inc. | Abilene, TX 79601 | Oil & Gas Operator | Jul 1999 |
| 682 | Demco Oil & Gas Company | Blackwell, OK 74631-4203 | Oil & Gas Operator | Jun 2025 |
| 683 | Demers - Fleming | Wichita Falls, TX 76305 | Oil & Gas Operator | Mar 2008 |
| 684 | Demers Oil Production | Byers, TX 76357 | Oil & Gas Operator | Apr 2002 |
| 685 | Demier Oil Company | Tulsa, OK 74105-2128 | Oil & Gas Operator | Nov 2008 |
| 686 | Deminex U.S. Oil Company | | Oil & Gas Operator | Jan 1998 |
| 687 | Demiran Production, Inc. | | Oil Operator | Mar 2008 |
| 688 | Demo Oil Co | | Oil Operator | Jan 2020 |
| 689 | Demoss, L. V. | Graham, TX 76450 | Oil & Gas Operator | May 2004 |
| 690 | Dempsey & Rowe | | Oil Operator | Aug 1986 |
| 691 | Dempsey, Wayne L | | Oil & Gas Operator | Mar 2011 |
| 692 | Den Cal, Inc. | Borger, TX 79007 | Oil & Gas Operator | Oct 2025 |
| 693 | Den-Kay Corp. | Plano, TX 75074 | Oil Operator | Aug 2009 |
| 694 | Denali Exploration, Inc. | Amarillo, TX 79109 | Oil & Gas Operator | Nov 2018 |
| 695 | Denali Oil & Gas Management, LLC | Houston, TX 77060 | Oil & Gas Operator | Dec 2012 |
| 696 | Denali Petroleum, LLC | Arlington, TX 76006 | Oil Operator | Mar 2021 |
| 697 | Denbury Management, Inc. | Dallas, TX 75252 | Oil & Gas Operator | Dec 1999 |
| 698 | Denbury Offshore, Inc. | | Oil & Gas Operator | Nov 2004 |
| 699 | Denbury Onshore, LLC | Plano, TX 75024 | Oil & Gas Operator | Oct 2025 |
| 700 | Denbury Resources Inc. | Plano, TX 75024 | Oil & Gas Operator | Dec 2003 |