X0101 EFFECT 33 LIVE 2016-03-25 0001193125-16-506687 POS AM 0000798949 UNIT CORP 333-202956 0001517153 Superior Pipeline Company, L.L.C. 333-202956-12 0001517367 Unit Drilling USA Columbia, L.L.C. 333-202956-10 0001517369 Preston County Gas Gathering, L.L.C. 333-202956-09 0001517371 Unit Texas Co 333-202956-08 0001517174 Superior Pipeline Texas, L.L.C. 333-202956-07 0001517173 Superior Appalachian Pipeline, L.L.C. 333-202956-06 0000310405 UNIT DRILLING & EXPLORATION CO 333-202956-05 0001517370 Petroleum Supply Co 333-202956-04 0001517368 Unit Drilling Columbia, L.L.C. 333-202956-03 0001517151 Unit Drilling Co 333-202956-02 0001517152 Unit Petroleum Co 333-202956-01