Abstract: The invention concerns a method which includes the steps of: introducing into a pre-drilled portion of a well (16) a drilling system containing a drilling bit (11) assembled with tubular lining elements (15), an element for measuring the inclination and azimuth direction of the pre-drilled part of the well, an element for rotary friction (26, 27) against the wall of the pre-drilled part and an element capable of modifying the friction coefficient of the friction element against the wall; measuring the azimuth direction of the pre-drilled part of the well (16); and varying the friction coefficient of the friction element (26, 27) sufficiently to influence the azimuth direction of the next well portion to be drilled.

Abstract: The invention concerns a method which consists in: introducing into a pre-drilled portion of a well (16) a drilling system comprising a drilling bit (11) assembled with tubular lining elements (15), means for measuring the inclination and azimuth direction of said pre-drilled part of the well, means for rotary friction (26, 27) against the wall of said pre-drilled part and controlled means capable of modifying the friction coefficient of said friction means against the wall; measuring the azimuth direction of the pre-drilled part of the well (16); and varying the friction coefficient of said friction means (26, 27) sufficiently to influence the azimuth direction of the next well portion to be drilled.

Abstract: The invention relates to a deviation calculation rule of the circular type for the monitoring of a two-dimensional deviated well path. The rule consists of a support plate (10) on which is marked a circular dial with two semi-circular scales (G1, G2) graduated in degrees for locating the inclination angle at the entry point and the exit point of a section of path, at least two rotary disks (12, 121) each marked with a plurality of concentric circles (C1 through Cn; C1 through C′n that each correspond to an inclination gradient for a specific drilled length (Gbu), at least one bi-sectoral disk (14) with, on its edges, scales (E1 through E4) used to locate the various Gbu circles on the disk being used (12), a first sliding system (16h) allowing for a direct reading of the horizontal deflections and a second sliding system (16v) allowing for a direct reading of the vertical depth deviations.