METHOD FOR WELL CONSTRUCTION Russian patent published in 1994 - IPC

FIELD: gas and oil producing industry. SUBSTANCE: method for well construction includes drilling of shaft, making upper and lower working platforms in it, vessel hydraulically communicated with drill string-casing annulus and bypass line with ground surface air-tight circulating system. Wellhead is equipped with sealing units arranged between lower and upper working platforms at distance ensuring location of members mounted in drill string and having outer diameter exceeding diameter of drill string itself. During further deepening of wellbore by drilling to design elevation, round-trip operations are effected through sealing units with maintenance of offset formation pressure. Before the last drilling, connected to drill string is first drill pipe from drill bit provided with cementing valve with inner diameter equalling diameter of designed flow string. Then, casing string is run into well and cemented. EFFECT: higher efficiency. 5 dwg