A remote controlled actuation device in combination with a body in which the device is positioned, a stabilizer which is actuated by the device, a drill string to which the body is secured and a monitoring device, the stabilizer being operatively connected to both the body and the actuation device, the drill string having a bore of a substantially constant internal diameter that has an incompressible fluid circulating therein in an axial direction, the drill string bore comprising a first end through which the incompressible fluid is introduced by a pumping means at an adjustable flow rate and a second end which is distant from the first end and wherein the incompressible fluid is used as a working fluid, the actuation device being positioned within a bore in the body, the body bore being substantially coaxial with the drill string bore, comprising:
- a differential piston mounted so as to be movable in the axial direction within the body bore, said piston having a tubular shape and a central bore which is substantially coaxial with the body bore and which piston bore comprises successively, in the direction of circulation of the incompressible fluid:
- a first profiled throttling portion the minimum internal diameter of which is smaller than an internal diameter of the body bore, and
- a second profiled portion having an internal surface of a diameter which widens in the direction of circulation of the incompressible fluid;
- a protruding profiled element secured to the body and disposed coaxially with the differential piston and having a profiled external surface matching the internal surface of the second profiled portion of the piston and facing said second profiled portion wherein a maximum outer diameter of the protruding profiled element is sufficiently smaller than an internal diameter of said first and second piston portions so as to leave an annular space through which working fluid continues to flow at all positions of said piston;
- a spring arranged between a part of the piston and a part of the body for biasing the piston in a direction of movement opposite the direction of circulation of the incompressible fluid;
- a means for measuring the pressure of the incompressible fluid at the first end of the drill string bore, said means being operatively connected to the drill string;
- at least one bearing blade mounted on an outer periphery of the body so as to be radially movable in relation to the body, wherein the differential piston is mounted in the body bore so as to be movable not only axially, but also rotationally about an axis of the body;
- longitudinal grooves having bottom surfaces inclined in a radial direction relative to the axis of the drill string, said grooves being provided on an outer surface of the differential piston and arranged in a spaced manner thereon and connected to one another by connecting grooves to form a continuous actuating surface for a step-by-step rotary movement of the piston and for its return into an initial position;
- and,
- at least one actuating finger mounted in the body so as to be radially movable in relation to the body, and interacting both with the piston actuating surface and the at least one bearing blade, to actuate the at least one bearing blade radially outwardly during a movement of the piston, wherein the actuation device allows for the circulation of the fluid in the drill string bore at a first, operating, flow rate without any movement of the piston, wherein a movement of the piston in the direction of circulation of the fluid occurs when the fluid circulates at a second, actuation, flow rate greater than said first operating flow rate and wherein an increasing loss of head is caused when the piston moves in the direction of circulation of the fluid by a cooperation of the second profiled portion of the piston bore and the profiled external surface of the protruding profiled element, the movement of the piston allowing an actuation of the stabilizer, the movement being stopped after the actuation has been carried out at which point a loss of head and a pressure of the working fluid are at a maximum, but working fluid still flows through said central bore, and wherein the pressure of the fluid is continuously measured thereby allowing a remote monitoring of the movement of the piston.