| 301 | Hamilton Brothers | Plainview, TX 79073 | Oil & Gas Operator | Mar 2008 |
| 302 | Hamilton Brothers Oil Co. | Houston, TX 77057 | Oil & Gas Operator | Mar 2015 |
| 303 | Hamilton Gas Co., Inc. | | Gas Operator | Mar 1999 |
| 304 | Hamilton K M Oil & Gas Co | Ada, OK 74820 | Oil Operator | Jan 2013 |
| 305 | Hamilton Leonard O | Marietta, OH 45750 | Oil & Gas Operator | Dec 2024 |
| 306 | Hamilton, Clay | Carrizo SPGS, TX 78834 | Oil & Gas Operator | Dec 2025 |
| 307 | Hamilton, Eddy R. | Breckenridge, TX 76424 | Oil & Gas Operator | Dec 2025 |
| 308 | Hamilton, J. R. | Carrizo SPGS, TX 78834 | Oil & Gas Operator | Dec 2025 |
| 309 | Hamilton, John M. | Wichita Falls, TX 76301 | Oil & Gas Operator | May 2001 |
| 310 | Hamilton, W. B., Estate | Wichita Falls, TX 76301 | Oil & Gas Operator | Mar 2004 |
| 311 | Hamilton-Tedford Oper. Co., LLC | Wichita Falls, TX 76301 | Oil Operator | May 2007 |
| 312 | Hamlin Jim | Dewey, OK 74029 | Oil & Gas Operator | Aug 1999 |
| 313 | Hamlin Oil Opera | | Oil Operator | May 1988 |
| 314 | Hamm N R Contrac | | Oil & Gas Operator | Jun 1989 |
| 315 | Hamm, Richard | Monahans, TX 79756 | Oil & Gas Operator | Mar 1994 |
| 316 | Hamm, Richard Inc. | Monahans, TX 79756 | Oil & Gas Operator | Dec 2025 |
| 317 | Hamman Oil & Refining Company | Houston, TX 77098 | Oil & Gas Operator | Dec 2025 |
| 318 | Hamman, Blake | Graham, TX 76450 | Oil & Gas Operator | Jul 2020 |
| 319 | Hammer Maclean Etal | Leon, KS 67074 | Oil Operator | Dec 2019 |
| 320 | Hammer Oil Compa | | Oil Operator | Oct 1985 |
| 321 | Hammer Oil Company | Post, TX 79356 | Oil & Gas Operator | Jun 2002 |
| 322 | Hammer Oil Properties Inc | Enid, OK 73706-0144 | Oil & Gas Operator | Oct 2017 |
| 323 | Hammer Ranch | Elmore City, OK 73433 | Oil & Gas Operator | Jan 2023 |
| 324 | Hammerschmidt Wi | | Oil Operator | Sep 1991 |
| 325 | Hammerschmidt, Leo | Plainville, KS 67663 | Oil Operator | Aug 2000 |
| 326 | Hammerschmidt, William E | Plainville, KS 67663 | Oil Operator | Sep 2025 |
| 327 | Hammersmith, Beverly | West Falls, NY 14170 | Gas Operator | Dec 2024 |
| 328 | Hammon Properties | Wichita Falls, TX 76307 | Oil & Gas Operator | Apr 1996 |
| 329 | Hammond Production Company | Bristow, OK 74010 | Oil & Gas Operator | Nov 1998 |
| 330 | Hammond Valley Colony, Inc. | Harlowton, MT 59036 | Gas Operator | Nov 2025 |
| 331 | Hamon Jake L | Dallas, TX 75201-3902 | Oil & Gas Operator | Nov 1997 |
| 332 | Hamon Oil Company | | Oil & Gas Operator | Aug 1985 |
| 333 | Hamon Operating Company | Dallas, TX 75201 | Oil & Gas Operator | Dec 2011 |
| 334 | Hamp Oil | Ponca City, OK 74604 | Oil & Gas Operator | Sep 2002 |
| 335 | Hamp Oil - Pace | | Oil & Gas Operator | Apr 1994 |
| 336 | Hampton Corporation (The) | Norman, OK 73069-5910 | Oil Operator | Jun 2016 |
| 337 | Hampton Oil & Gas | Early, TX 76802 | Gas Operator | Feb 2012 |
| 338 | Hampton Resources Corporation | Houston, TX 77010 | Oil & Gas Operator | Mar 1996 |
| 339 | Hampton, Jno. W. & Son | Wichita Falls, TX 76302 | Oil & Gas Operator | Nov 1998 |
| 340 | Hanaco Operating | Holliday, TX 76366 | Oil Operator | Mar 2008 |
| 341 | Hanaco, LLC | Holliday, TX 76366 | Oil Operator | Dec 2017 |
| 342 | Hanagan Petroleum Corp | Roswell, NM 88201 | Oil & Gas Operator | Sep 1999 |
| 343 | Hancock Leon | Kingston, OK 73439-9618 | Oil Operator | Dec 2014 |
| 344 | Hancock, Burton W | Morrison, CO 80465 | Oil & Gas Operator | Dec 2017 |
| 345 | Hand Oil Co. | Chanute, KS 66720 | Oil Operator | Nov 2000 |
| 346 | Handy, Daniel G. | East Aurora, NY 14052 | Gas Operator | Dec 2024 |
| 347 | Hane Operating, Inc. | Santa Anna, TX 76878 | Oil & Gas Operator | Sep 2005 |
| 348 | Hanger Oil, L.L.C. | Wichita Falls, TX 76308 | Oil & Gas Operator | Dec 2025 |
| 349 | Hank Oil & Gas, Inc. | Houston, TX 77056 | Oil & Gas Operator | Oct 2023 |
| 350 | Hankamer, Curtis Corporation,The | Houston, TX 77024 | Oil & Gas Operator | Dec 2025 |
| 351 | Hankey Oil Company | Houston, TX 77027 | Oil & Gas Operator | Feb 2010 |
| 352 | Hankey Operating, Inc. | Houston, TX 77027 | Oil & Gas Operator | Mar 2016 |
| 353 | Hanks, Christopher Glenn | Gainesville, TX 76240 | Oil & Gas Operator | Dec 2025 |
| 354 | Hanley & Bird Inc | Tulsa, OK 74119 | Oil & Gas Operator | Dec 2011 |
| 355 | Hanley Petroleum Inc. | Midland, TX 79701 | Oil & Gas Operator | Oct 2017 |
| 356 | Hanna M A Co | Cleveland, OH 44114-1824 | Oil & Gas Operator | Dec 1991 |
| 357 | Hanna Oil And Gas Company | Fort Smith, AR 72901 | Oil & Gas Operator | Oct 2025 |
| 358 | Hannathon Petroleum II, LLC | Midland, TX 79705 | Oil & Gas Operator | Dec 2025 |
| 359 | Hannathon Petroleum, LLC | Midland, TX 79705 | Oil & Gas Operator | Dec 2025 |
| 360 | Hannis Operating, LLC | Olney, TX 76374 | Oil & Gas Operator | Dec 2025 |
| 361 | Hannold, Allan & Yolanda | Bloomfield, NY 14469 | Gas Operator | Dec 2024 |
| 362 | Hanoco Inc | Tulsa, OK 74135 | Oil & Gas Operator | Oct 2025 |
| 363 | Hanover Management Company | | Oil Operator | Aug 1979 |
| 364 | Hanover Operating Company | Tulsa, OK 74101 | Oil & Gas Operator | Dec 1998 |
| 365 | Hanselman, Michael D. | Jamestown, NY 14701 | Gas Operator | Dec 2024 |
| 366 | Hansen Dane G TR | | Oil Operator | Feb 1995 |
| 367 | Hansen Noel | Avant, OK 74001 | Oil Operator | Aug 2013 |
| 368 | Hansen Oil Corporation | Shreveport, LA 71106 | Oil Operator | Apr 2003 |
| 369 | Hansen, Dane G. - Trust | Logan, KS 67646 | Oil Operator | Oct 2013 |
| 370 | Hansford, Inc. | Amarillo, TX 79101 | Gas Operator | Dec 2004 |
| 371 | Hanshu Production Company | Darrouzett, TX 79024 | Oil & Gas Operator | Apr 2017 |
| 372 | Hanshu Production Company, LLC | Nashville, TN 37215 | Gas Operator | Dec 2025 |
| 373 | Hanson Corporation | New Braunfels, TX 78132 | Oil & Gas Operator | Mar 2008 |
| 374 | Hanson Energy | Glencoe, NM 88324 | Oil & Gas Operator | Jul 2008 |
| 375 | Hanson Minerals Co. | Houston, TX 77042 | Oil & Gas Operator | Oct 1993 |
| 376 | Hanson Natural Resources Co. | | Oil & Gas Operator | Nov 1991 |
| 377 | Hanson Operating Company Inc | Roswell, NM 88202 | Oil & Gas Operator | Aug 2025 |
| 378 | Hanson Production Company | Cuero, TX 77954 | Oil & Gas Operator | Jul 2009 |
| 379 | Hanvey Production Co., Inc. | Roanoke, TX 76262 | Oil & Gas Operator | Nov 2012 |
| 380 | Hanvey, Don H. Oil Interests Inc | Cisco, TX 76437 | Oil & Gas Operator | Dec 2025 |
| 381 | Happy Hill Operating LLC | Guthrie, OK 73044-7361 | Oil & Gas Operator | Oct 2017 |
| 382 | Har Ken Oil Company | | Oil & Gas Operator | Dec 2021 |
| 383 | Har-Ken Agent Ok, LTD | Owensboro, KY 42302 | Oil & Gas Operator | Dec 2023 |
| 384 | Har-Ken Agent, Ok | Owensboro, KY 42302 | Oil Operator | Sep 2025 |
| 385 | Harbacek Florence | Holyrood, KS 67450 | Oil Operator | Aug 2002 |
| 386 | Harbert Energy Corp | Irving, TX 75015-2510 | Oil & Gas Operator | Feb 1993 |
| 387 | Harbert Energy Corp/Gulf Coast | | Oil & Gas Operator | Dec 1991 |
| 388 | Harbor Operating, LLC | | Oil & Gas Operator | Dec 1999 |
| 389 | Harbor Petroleum, LLC | Granbury, TX 76049 | Oil & Gas Operator | Dec 2025 |
| 390 | Harbor Resources LLC | Oklahoma City, OK 73120 | Oil & Gas Operator | Dec 2025 |
| 391 | Harborcreek SCH Dist | Harborcreek, PA 16421-1606 | Oil & Gas Operator | Dec 2024 |
| 392 | Harburg* Rudolph W | | Oil & Gas Operator | Nov 2022 |
| 393 | Harco Land, Inc. | Dallas, TX 75230 | Oil & Gas Operator | Aug 1996 |
| 394 | Harcon Energy, LLC | Le Roy, KS 66857 | Oil Operator | Dec 2009 |
| 395 | Harcor Energy Inc. | | Gas Operator | Dec 1999 |
| 396 | Harcor Exploration Inc. | | Oil Operator | Aug 1989 |
| 397 | Hard Rock DRLG Co | Falls Of Rough, KY 40119 | Oil Operator | Dec 2023 |
| 398 | Hard Rock Exploration, Inc. | | Oil & Gas Operator | Dec 2008 |
| 399 | Hard Rock Operating LLC | | Oil & Gas Operator | May 2022 |
| 400 | Hardco Inc | Cleveland, OH 44115 | Oil & Gas Operator | Dec 1992 |