Drilling direction correction of a steerable subterranean drill in view of a detected formation tendency

A method for detecting a formation tendency force acting on a drill bit of a drill string having a rotary steerable subterranean drill and contemporaneously reconfiguring a direction of the rotary steerable subterranean drill, the method comprising:

• deflecting a drilling shaft of a drilling shaft deflection device so that the drilling shaft extends from a deflection housing of the drilling shaft deflection device at an angle, the deflecting being driven by an electrically commutated drive motor;
• rotating, by the drilling shaft deflection device, the deflected drilling shaft through a substantially 360 degree sweep in which the toolface of the drill bit is pressed against the circumferential periphery of the borehole wall during the sweep and wherein a formation tendency force vector is determined based on the direction of peak magnitude, an amount of current supplied to the electrically commutated motor, the formation tendency force vector being generated by a shape of a plurality of layers making up a formation and resulting from a vertical force vector component and a side force vector component of the plurality of layers, wherein the drill string, the drilling shaft and the drill bit have a first rotational direction during drilling, and wherein the full rotational sweep of the deflected drilling shaft by the drilling shaft deflection device is in a direction opposite the first rotational direction;
• determining the formation tendency normal force vector based on a full rotational sweep of a drill bit and determining a peak maximum torque during the full rotational sweep, wherein the peak maximum torque is an elevated torque above an average torque of the full rotational sweep of the drill bit, detected at a point about the full rotational sweep other than the predetermined desired drilling direction vector;
• calculating a corrected drilling direction vector sufficient to counteract the formation tendency normal force vector so as to drill in a predetermined desired drilling direction vector;
• and
• configuring the steering direction setting device contemporaneously to cause the drill bit of the steerable subterranean drill to drill in the desired drilling direction based on the corrected drilling direction vector, thereby counteracting the formation tendency normal force acting on the drill bit.

A drilling apparatus comprising:

• a drill string having a steerable subterranean drill with a drill bit and a steering direction setting device, the steering direction setting device comprising drilling shaft deflection device which comprises an electrically commutated drive motor, and the detecting the magnitude of the formation tendency normal force vector based on the amount of current supplied to the electrically commutated motor in the steering direction setting device;
• a controller;
• wherein the controller, in dependence upon a detected peak magnitude of the formation tendency normal force vector acting on the drill bit, the peak magnitude of the formation force determined based on a full rotational sweep of a drill bit, wherein the peak magnitude torque is an elevated torque above an average torque of the full rotational sweep of the drill bit, detected at a point about the full rotational sweep other than a predetermined desired drilling direction vector, wherein the drill string, the drilling shaft and the drill bit having a first rotational direction during drilling, and wherein the full rotational sweep of the deflected drilling shaft by the steering direction setting is in a direction opposite the first rotational direction,
• calculates a corrected drilling direction vector sufficient to counteract the formation tendency normal force vector so as to drill in a predetermined desired drilling direction vector, and
• transmits an instruction configuring the steering direction setting device contemporaneously to cause the drill bit of the steerable subterranean drill to drill in a direction counteracting the formation tendency force vector based on the corrected drilling direction vector.