| 摘要 |
A directional casing drilling system comprises a casing string 411 and a casing latch 421, wherein the casing latch 421 is disposed inside the casing string 411 proximate a lower end of the casing string 411. The casing latch 421 couples a pipe section 423 to the casing string 411 so that the casing string 411 transfers rotary motion to a drill bit 405 to form a pilot hole 408. The drill bit 405 is operatively coupled to a rotary steerable system 415 to allow the drill bit 405 to change direction by pushing the rotary steerable system 415 against the inside of the casing string 411. In one embodiment, an underreamer 413 is used to form a larger bore, whilst in another embodiment, a casing cutter (512, figure 5) is used to form another larger bore. |
