| 601 | Del Amo Energy Co. | | Oil & Gas Operator | Dec 1987 |
| 602 | Del Energy, Inc | | Oil Operator | Dec 2014 |
| 603 | Del Mar | Holliday, TX 76366 | Oil & Gas Operator | Apr 2026 |
| 604 | Del Mar Energy, Inc. | Van Alstyne, TX 75495 | Oil & Gas Operator | Apr 2026 |
| 605 | Del Mar Exploration Company | Houston, TX 77006 | Oil & Gas Operator | Jan 2014 |
| 606 | Del Oil & Gas Corp | | Oil Operator | Jul 1981 |
| 607 | Del Petroleum Corporation | Dallas, TX 75219 | Oil & Gas Operator | Jan 2012 |
| 608 | Del Rio Production Co. | Gainesville, TX 76240 | Oil Operator | Mar 2019 |
| 609 | Del-Rio Resources Inc | Vernal, UT 84079 | Oil & Gas Operator | Jan 2018 |
| 610 | Delaware Davis Petroleum Corp. | Houston, TX 77056 | Oil & Gas Operator | Jan 2000 |
| 611 | Delaware Dyche Corp. | Hutchinson, KS 67501 | Oil Operator | Jan 2010 |
| 612 | Delaware Ecco Petroleum Inc. | Rockwall, TX 75087 | Oil & Gas Operator | Jul 2001 |
| 613 | Delbert A. Dodson | | Oil Operator | Aug 2002 |
| 614 | Delcar, Inc. | San Antonio, TX 78209 | Oil & Gas Operator | Oct 1995 |
| 615 | Delco Operating Company LP | Houston, TX 77056 | Oil & Gas Operator | May 2020 |
| 616 | Delek Energy Systems Us, Inc. | Denver, CO 80202 | Oil & Gas Operator | Oct 2011 |
| 617 | Delfin Operating, LLC | Dallas, TX 75243 | Oil & Gas Operator | Apr 2026 |
| 618 | Delgado, Emil A | San Antonio, TX 78223 | Oil & Gas Operator | Sep 2016 |
| 619 | Delhi Gas Pipeli | | Gas Operator | Aug 1998 |
| 620 | Delhi Gas Pipeline Corporation | Palestine, TX 75802 | Oil & Gas Operator | Feb 1998 |
| 621 | Delhi Pipeline | | Oil & Gas Operator | Sep 1999 |
| 622 | Delhi-Taylor Oil Corp | | Oil & Gas Operator | Dec 1974 |
| 623 | Delhi-Trading LLC | Durango, CO 81301 | Oil & Gas Operator | Mar 2026 |
| 624 | Dell Charles E | Cleveland, OK 74020-0090 | Oil & Gas Operator | Feb 2015 |
| 625 | Dell-Ray Investments, Inc. | Nickerson, KS 67561 | Oil Operator | Dec 2019 |
| 626 | Delmar Operating, Inc. | Houston, TX 77010 | Oil & Gas Operator | Oct 1996 |
| 627 | Delone, M S | El Dorado, AR 71730 | Oil & Gas Operator | Jan 2025 |
| 628 | Delong Oil & Gas Services, Inc. | Cushing, OK 74023 | Oil & Gas Operator | Jan 2026 |
| 629 | Delong Ralph J | Sapulpa, OK 74066 | Oil & Gas Operator | Nov 2005 |
| 630 | Delong, Horace | Graham, TX 76450 | Oil & Gas Operator | Apr 2026 |
| 631 | Delong, Ralph S | | Oil & Gas Operator | Jun 2025 |
| 632 | Delozier, Orval & Stevens, Floyd, A General Partnership | Dewey, OK 74029 | Oil Operator | Nov 2009 |
| 633 | Delphi International, Inc. | Tulsa, OK 74104 | Oil Operator | Feb 2026 |
| 634 | Delphi Oil And Gas LLC | Macomb, OK 74852 | Oil Operator | Nov 2025 |
| 635 | Delphi Oil Inc. | | Oil & Gas Operator | Jan 2026 |
| 636 | Delray Oil, Inc. | San Antonio, TX 78209 | Oil & Gas Operator | Apr 2026 |
| 637 | Delta C02, LLC | Breckenridge, TX 76424 | Oil & Gas Operator | Jul 2021 |
| 638 | Delta D Operations | Wilson, OK 73463 | Oil & Gas Operator | Jul 2014 |
| 639 | Delta D Operations Inc | Ardmore, OK 73401-8678 | Oil & Gas Operator | Apr 2014 |
| 640 | Delta Development Co. Inc. | | Oil & Gas Operator | Dec 1988 |
| 641 | Delta Energy Resources, Inc. | | Oil & Gas Operator | Jun 1990 |
| 642 | Delta Expl.& Development Corp. | | Oil & Gas Operator | Jan 2025 |
| 643 | Delta Exploration Company Inc | Denver, CO 80202 | Oil & Gas Operator | Apr 2026 |
| 644 | Delta Oil | Holliday, TX 76366 | Oil & Gas Operator | Sep 2005 |
| 645 | Delta Oil & Gas Company | Breckenridge, TX 76424 | Oil & Gas Operator | Apr 2003 |
| 646 | Delta Oil & Gas LTD. | Breckenridge, TX 76424 | Oil & Gas Operator | Apr 2026 |
| 647 | Delta Oil Co Inc | | Oil & Gas Operator | Oct 2023 |
| 648 | Delta Oil Co Inc And Great Lakes Niagaran | | Oil & Gas Operator | Dec 1987 |
| 649 | Delta Operating Company | | Oil Operator | Mar 1987 |
| 650 | Delta Operating Corporation | | Oil & Gas Operator | Feb 2024 |
| 651 | Delta Petro Corp Of Colorado | Houston, TX 77010-3089 | Gas Operator | Dec 2003 |
| 652 | Delta Petroleum Company | Houston, TX 77267 | Oil Operator | Aug 1996 |
| 653 | Delta Petroleum Corp | Denver, CO 80202 | Oil & Gas Operator | Dec 2025 |
| 654 | Delta Petroleum Corp Of Co | | Oil & Gas Operator | Oct 2010 |
| 655 | Delta Petroleum Inc | Houston, TX 77269-1007 | Oil & Gas Operator | May 2009 |
| 656 | Delta Producers, Inc | Greenville, MS 38703 | Oil & Gas Operator | Dec 2023 |
| 657 | Delta Production Services, LLC | | Oil & Gas Operator | Aug 2002 |
| 658 | Delta Royalties LLC | | Oil & Gas Operator | Dec 2024 |
| 659 | Delta Sierra Oil & Gas LLC | | Gas Operator | Jan 2018 |
| 660 | Deltaus Corporation | | Oil & Gas Operator | Oct 1985 |
| 661 | Deltex Minerals Inc. | Peachtree Cty, GA 30269 | Oil & Gas Operator | Apr 2026 |
| 662 | Deltex Petroleum | | Oil Operator | Nov 1994 |
| 663 | Delwintex Oil & Gas Prop., Inc. | Lubbock, TX 79423 | Oil & Gas Operator | Aug 2003 |
| 664 | Dem Operations Inc | Lamont, OK 74643-5010 | Oil & Gas Operator | Feb 2026 |
| 665 | Demambro, Gene Brian | Mayville, NY 14757 | Gas Operator | Dec 2024 |
| 666 | Demand Energy, Inc. | Abilene, TX 79601 | Oil & Gas Operator | Jul 1999 |
| 667 | Demco Oil & Gas Company | Blackwell, OK 74631-4203 | Oil & Gas Operator | Jan 2026 |
| 668 | Demers - Fleming | Wichita Falls, TX 76305 | Oil & Gas Operator | Mar 2008 |
| 669 | Demers Oil Production | Byers, TX 76357 | Oil & Gas Operator | Apr 2002 |
| 670 | Demier Oil Company | Tulsa, OK 74105-2128 | Oil & Gas Operator | Nov 2008 |
| 671 | Deminex U S Oil Company | | Oil & Gas Operator | Jan 1998 |
| 672 | Demiran Production, Inc. | | Oil Operator | Mar 2008 |
| 673 | Demo Oil Co | | Oil Operator | Jan 2020 |
| 674 | Demoss, L. V. | Graham, TX 76450 | Oil & Gas Operator | May 2004 |
| 675 | Dempsey & Rowe | | Oil Operator | Aug 1986 |
| 676 | Dempsey, Wayne L | | Oil & Gas Operator | Mar 2011 |
| 677 | Den Cal, Inc. | Borger, TX 79007 | Oil & Gas Operator | Apr 2026 |
| 678 | Den-Kay Corp. | Plano, TX 75074 | Oil Operator | Aug 2009 |
| 679 | Denali Exploration, Inc. | Amarillo, TX 79109 | Oil & Gas Operator | Nov 2018 |
| 680 | Denali Oil & Gas Management LLC | Houston, TX 77060 | Oil & Gas Operator | Dec 2012 |
| 681 | Denali Petroleum, LLC | Arlington, TX 76006 | Oil Operator | Mar 2021 |
| 682 | Denbury Management, Inc. | Dallas, TX 75252 | Oil & Gas Operator | Dec 1999 |
| 683 | Denbury Offshore, Inc. | | Oil & Gas Operator | Nov 2004 |
| 684 | Denbury Onshore, LLC | Plano, TX 75024 | Oil & Gas Operator | Apr 2026 |
| 685 | Denbury Resources Inc. | Plano, TX 75024 | Oil & Gas Operator | Dec 2003 |
| 686 | Denchfield, Fred | Neal, KS 66863 | Oil Operator | Dec 1997 |
| 687 | Denex Petroleum Corp. | Buckhannon, WV 26201 | Oil & Gas Operator | Dec 2021 |
| 688 | Denex, Inc. | | Oil & Gas Operator | Jul 1983 |
| 689 | Denham Danny D | Kellyville, OK 74039 | Oil & Gas Operator | Jan 2026 |
| 690 | Denham Operating Company | Tulsa, OK 74101-3627 | Oil & Gas Operator | Aug 2022 |
| 691 | Denhart & Denhart | Brownwood, TX 76804 | Oil & Gas Operator | Dec 2001 |
| 692 | Deni Frank R | | Oil Operator | Dec 2022 |
| 693 | Denis Roberts Oil | | Oil Operator | Nov 2025 |
| 694 | Denman J M Oil C | | Oil Operator | Mar 1994 |
| 695 | Denman-Friesen Co. | Lufkin, TX 75901 | Oil & Gas Operator | Nov 2006 |
| 696 | Denmark Oil | Wichita, KS 67212 | Oil & Gas Operator | May 2000 |
| 697 | Dennett'S Inc | Enid, OK 73701-1851 | Oil & Gas Operator | Apr 2014 |
| 698 | Denney Don | Citrus Heights, CA 95611-2473 | Oil Operator | Aug 2023 |
| 699 | Dennis & Broun | Bullard, TX 75757 | Oil & Gas Operator | Sep 2003 |
| 700 | Dennis & Davis Oil Co. | Nocona, TX 76255 | Oil & Gas Operator | Apr 2026 |