| 501 | Apex Royalties, Inc. | Midland, TX 79702 | Oil & Gas Operator | May 1997 |
| 502 | Apexco, Inc. | Sand Springs, OK 74063 | Oil & Gas Operator | Oct 2024 |
| 503 | API Operating Co. | Houston, TX 77036 | Oil & Gas Operator | Apr 2025 |
| 504 | Apollo Energy Operating Co, LP | Lake Charles, LA 70601 | Oil & Gas Operator | Dec 2024 |
| 505 | Appling, J. B. | Midland, TX 79702 | Oil & Gas Operator | Jul 1997 |
| 506 | Approach Operating LLC | Fort Worth, TX 76116 | Oil & Gas Operator | Sep 2020 |
| 507 | Apr Operating LLC | Midland, TX 79701 | Oil & Gas Operator | Jun 2022 |
| 508 | Apv McCamey LLC | MC Camey, TX 79752 | Oil & Gas Operator | Apr 2025 |
| 509 | Apx & Assoc. | FT Stockton, TX 79735 | Oil & Gas Operator | Sep 1998 |
| 510 | Aquila Energy Resources Corp. | Houston, TX 77042 | Oil & Gas Operator | Nov 2013 |
| 511 | Aquinas Oil & Gas, LLC | Muenster, TX 76252 | Oil Operator | Apr 2025 |
| 512 | Arabella Operating, LLC | Fort Worth, TX 76102 | Oil & Gas Operator | Apr 2025 |
| 513 | Arabella Petroleum Company, LLC | Austin, TX 78701 | Oil & Gas Operator | Apr 2025 |
| 514 | Arabie, Inc. | Lake Charles, LA 70605 | Oil & Gas Operator | Apr 2025 |
| 515 | Araluen Energy, Inc. | Houston, TX 77094 | Oil Operator | Jun 2022 |
| 516 | Aramco Petroleum LLC | Burkburnett, TX 76354 | Oil Operator | Apr 2025 |
| 517 | Aransas DRLG & Workover Co Inc | Corpus Chrsti, TX 78409 | Oil & Gas Operator | Jul 2019 |
| 518 | Aransas Oil Company, Inc. | San Antonio, TX 78253 | Oil & Gas Operator | Jan 1999 |
| 519 | Aransas Resources, Inc | Houston, TX 77083 | Oil & Gas Operator | Dec 2005 |
| 520 | Aransas Resources, LP | Houston, TX 77006 | Oil & Gas Operator | Oct 2006 |
| 521 | Arapahoe Prod. Co. | Borger, TX 79008 | Oil & Gas Operator | May 2012 |
| 522 | Arapahoe Resources LLC | Oklahoma City, OK 73118 | Oil & Gas Operator | Jan 2025 |
| 523 | Aratex Production Company | Denver, CO 80202 | Oil & Gas Operator | Jun 2003 |
| 524 | Araxas Exploration, Inc. | The Woodlands, TX 77380 | Oil & Gas Operator | Apr 1998 |
| 525 | Arben Oil, Inc. | Coleman, TX 76834 | Oil & Gas Operator | Apr 2025 |
| 526 | Arbol Resources, Inc. | Houston, TX 77079 | Oil & Gas Operator | Apr 2025 |
| 527 | Arcadia Energy Resources, LLC | Oklahoma City, OK 73102 | Oil & Gas Operator | Apr 2025 |
| 528 | Arcadia Expl. & Prod. Company | Kilgore, TX 75663 | Oil & Gas Operator | Dec 2011 |
| 529 | Arcadia Operating, LLC | Dallas, TX 75219 | Oil & Gas Operator | Apr 2025 |
| 530 | Arcadian Mineral Development | Brownwood, TX 76801 | Oil & Gas Operator | Dec 2013 |
| 531 | Arcadian Mineral Development,LLC | Brownwood, TX 76801 | Oil & Gas Operator | Apr 2025 |
| 532 | Arcadian Resources LLC | Glen Elder, KS 67446 | Oil & Gas Operator | Apr 2025 |
| 533 | Arch Oil & Gas, LLC | Dallas, TX 75254 | Oil & Gas Operator | Apr 2025 |
| 534 | Arch Operating, LLC | Wichita Falls, TX 76308 | Oil Operator | Apr 2025 |
| 535 | Arch Petroleum Inc. | Houston, TX 77252 | Oil & Gas Operator | Mar 2008 |
| 536 | Archer Drilling & Prod. Co. | Archer City, TX 76351 | Oil & Gas Operator | Nov 2002 |
| 537 | Archer Petroleum | Frisco, TX 75034 | Oil & Gas Operator | Aug 2021 |
| 538 | Archer Reef Oil Co. | Bellevue, TX 76228 | Oil & Gas Operator | Apr 2025 |
| 539 | Archer, Carl M. | Spearman, TX 79081 | Oil & Gas Operator | Feb 2005 |
| 540 | Archer, Carl M. Farms, Inc. | Gruver, TX 79040 | Gas Operator | Mar 2024 |
| 541 | Archer,Carl M Estate Partnership | Gruver, TX 79040 | Oil & Gas Operator | Sep 2022 |
| 542 | Archon Resources LLC | Houston, TX 77074 | Oil & Gas Operator | Jan 2015 |
| 543 | Arco Oil & Gas Co.-Silsbee | Lafayette, LA 70505 | Oil & Gas Operator | Jul 1993 |
| 544 | Arco Oil & Gas Company | Plano, TX 75086 | Oil & Gas Operator | Mar 2006 |
| 545 | Arco Permian | Houston, TX 77079 | Oil & Gas Operator | Dec 2001 |
| 546 | Arco Pipe Line Company | Independence, KS 67301 | Oil & Gas Operator | Jun 1996 |
| 547 | Arcooil Corp | San Antonio, TX 78205 | Oil & Gas Operator | Apr 2025 |
| 548 | Arcotex Oil & Gas Inc | Gainesville, TX 76241-1357 | Oil & Gas Operator | Feb 2025 |
| 549 | Arcturus Operating Company | Addison, TX 75001 | Oil & Gas Operator | Apr 2025 |
| 550 | Ard Drilling Company Inc. | Abilene, TX 79604 | Oil & Gas Operator | Jun 2000 |
| 551 | Ard, Julian | Fort Worth, TX 76102 | Oil & Gas Operator | Jun 2002 |
| 552 | Arden Energy Partners, Inc. | San Angelo, TX 76906 | Oil & Gas Operator | Feb 2013 |
| 553 | Ardent Energy LLC | Edmond, OK 73083 | Oil & Gas Operator | Apr 2025 |
| 554 | Area Pipe And Equipment | Midland, TX 79702 | Oil & Gas Operator | Apr 2003 |
| 555 | Arena Offshore, LLC | The Woodlands, TX 77381 | Oil & Gas Operator | Mar 2009 |
| 556 | Arena Production Company | Midland, TX 79710 | Oil & Gas Operator | Apr 2025 |
| 557 | Arena Resources LLC | Longview, TX 75608 | Oil & Gas Operator | Jan 2025 |
| 558 | Ares Energy, LTD. | Midland, TX 79701 | Oil & Gas Operator | Apr 2025 |
| 559 | Arete Operating Company II, LLC | San Antonio, TX 78260 | Oil & Gas Operator | Apr 2025 |
| 560 | Arete Operating Company III, LLC | San Antonio, TX 78260 | Oil & Gas Operator | Apr 2025 |
| 561 | Arete Operating Company, LLC | San Antonio, TX 78260 | Oil & Gas Operator | Apr 2025 |
| 562 | Argali Resources | Dallas, TX 75206 | Oil & Gas Operator | Apr 2003 |
| 563 | Argent Energy (Us) Holdings Inc | Sugar Land, TX 77479 | Oil & Gas Operator | Sep 2021 |
| 564 | Argent Petroleum Corporation | Center, TX 75935 | Oil & Gas Operator | Apr 2025 |
| 565 | Argosy | Carrollton, TX 75010 | Oil & Gas Operator | Aug 2003 |
| 566 | Argus Drilling, LLC | Midland, TX 79702 | Oil & Gas Operator | Mar 2008 |
| 567 | Argus Production Company | Dallas, TX 75382 | Oil & Gas Operator | Nov 2023 |
| 568 | Ariel Resources, Inc. | Dallas, TX 75287 | Oil & Gas Operator | May 1997 |
| 569 | Aries Operating LP | Houston, TX 77042 | Oil & Gas Operator | Apr 2025 |
| 570 | Aries Operating, LLC | Houston, TX 77010 | Oil & Gas Operator | Feb 2010 |
| 571 | Arista Novelty, Inc. | Houston, TX 77256 | Oil & Gas Operator | Feb 1995 |
| 572 | Ark Petroleum Inc. | Clyde, TX 79510 | Oil & Gas Operator | Nov 1997 |
| 573 | Ark-La-Tex Energy Partners, LLC | Shreveport, LA 71101 | Oil & Gas Operator | Jan 2013 |
| 574 | Ark-La-Tex Energy, L.L.C. | Shreveport, LA 71101 | Oil & Gas Operator | Apr 2025 |
| 575 | Ark-La-Tex Production, LLC | Doddridge, AR 71834 | Oil Operator | Jan 2025 |
| 576 | Arkla Exploration Co. | Shreveport, LA 71151 | Oil & Gas Operator | Jan 1993 |
| 577 | Arkland Producing Co Inc | Midland, TX 79701 | Oil & Gas Operator | Nov 2023 |
| 578 | Arkland, Inc. | Midland, TX 79701 | Oil & Gas Operator | Jul 1994 |
| 579 | Arkoma Prod Co Of Texas, Inc. | Dallas, TX 75225 | Oil Operator | May 2004 |
| 580 | Arkoma, Sandra | Pampa, TX 79066 | Oil & Gas Operator | May 1995 |
| 581 | Arleand Resources | Overton, TX 75684 | Oil & Gas Operator | Apr 2025 |
| 582 | Arledge & Young, Inc. | Weatherford, TX 76086 | Oil & Gas Operator | Feb 1999 |
| 583 | Arledge, Terry | Rockdale, TX 76567 | Oil & Gas Operator | Sep 2019 |
| 584 | Arlen Corporation | Houston, TX 77077 | Oil & Gas Operator | Mar 2008 |
| 585 | Arlian, Inc. | Denver, CO 80202 | Oil Operator | Feb 1998 |
| 586 | Arm Energy Management LLC | Houston, TX 77070 | Oil & Gas Operator | Jan 2025 |
| 587 | Armidillo Oil Company | Luling, TX 78648 | Oil & Gas Operator | Apr 2025 |
| 588 | Armor Energy LLC | Tulsa, OK 74146 | Oil & Gas Operator | Jun 2022 |
| 589 | Armor Petroleum, Inc. | Wichita Falls, TX 76308 | Oil & Gas Operator | Apr 2025 |
| 590 | Armor Resources LLC | Longview, TX 75604 | Oil & Gas Operator | Apr 2025 |
| 591 | Armour Properties | Houston, TX 77056 | Oil & Gas Operator | May 1994 |
| 592 | Armour Resource Holdings, LTD. | Houston, TX 77046 | Oil & Gas Operator | Nov 1994 |
| 593 | Armour, Widd | Graham, TX 76450 | Oil & Gas Operator | Apr 2025 |
| 594 | Arnold Oil Properties, Inc. | Oklahoma City, OK 73112 | Oil & Gas Operator | May 2019 |
| 595 | Arnold Oil Properties, L.L.C. | Nichols Hill, OK 73116 | Oil & Gas Operator | Apr 2025 |
| 596 | Arnot Oil Company, LLC | Breckenridge, TX 76424 | Oil & Gas Operator | Apr 2025 |
| 597 | Arnot, W. G., Jr. | Breckenridge, TX 76424 | Oil & Gas Operator | Jan 2017 |
| 598 | Aroc (Texas) Inc | Houston, TX 77090 | Oil & Gas Operator | Dec 2014 |
| 599 | Arp Barnett, LLC | Fort Worth, TX 76102 | Oil & Gas Operator | Nov 2018 |
| 600 | Arpel, Inc. | Oklahoma City, OK 73102 | Oil & Gas Operator | Apr 2014 |