METHOD AND APPARATUS FOR SELECTIVELY STRAIGHT OR DIRECTIONAL DRILLING IN SUBSURFACE ROCK FORMATIONS

摘要

METHOD AND APPARATUS FOR SELECTIVELY STRAIGHT-OR DIRECTIONAL DRILLING IN SUBSURFACE ROCK-FORMATION A device for use in underground drilling comprising: a tubular housing, a down-hole motor mounted within the housing and having an output shaft, means for connecting said output shaft to a drill bit, means for connecting said housing to a drill string, first and second stabilisers mounted on said housing, said first stabiliser being mounted nearer than the second stabiliser to the output shaft connecting means, at least one of said stabilisers being an eccentric stabiliser, and at least one stress relieving means between the first stabiliser and the means for connecting the housing to the drill string.