Stabiliser in drilling tube string to vary inclination of bore hole - has tubular member contg. elements radially extendable to hole dia. against springs by mud pressure and retractable by dropping sealing bush

摘要

The stabiliser for interposing between two adjoining tube sections of a drilling tube string comprises a cylindrical tubular member at its ends provided with coupling means for tube sections and having outward projections of which the outer ends define an imaginary envelope cylinder with diameter equal to that of the bore hole. The projections are formed by a number of plunger-like elements which are radially outwardly movable (in lining bushes; against springs into their active positions, means being provided to actuate these elements from ground level (actuation being by drilling mud pressure in the tubular member admitted via bores closable by dropping a bush down the tube string).