| 摘要 |
A drill rod for reverse circulation drilling, the drill rod comprising a first outer tube having an first end adapted to receive a rotational force to transfer the rotational force to the first drill bit and a second end adapted to receive a first drill bit, and a first inner tube adapted to be inserted in the outer tube to define an annulus to allow fluid flow from the first end of the outer tube to the second end of the outer tube, the inner tube having a first end and a second end, the second end being adapted to receive a second drill bit, wherein the inner tube is releasably inserted within the outer tube. Also provided an inner string including at least one inner tube and a method for casing a bore hole. Fig 1 |
