Method and system of trajectory prediction and control using PDC bits
First Claim
1. A method of trajectory control of a PDC (Polycrystalline Diamond Compact) drill bit attached at the bottom of a drill string used for drilling a borehole through an earth strata formation and thereby achieve a predetermined intended path of PDC bit controlled trajectory comprising the steps of:
- determining a drill bit path or trajectory deviation tendency for the PDC drill bit;
determining side forces and bending moments of the PDC drill bit;
estimating response characteristics of the PDC drill bit for a given bit advance in the downward axial direction based upon the determined side forces and bending moments and on the determined bit deviation tendency; and
controlling a simultaneous and/or subsequent lateral movement of the PDC drill bit relative to the estimated response for said PDC drill bit undergoing a given bit advance so as to compensate for drill bit path or trajectory deviation.
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Abstract
A method of forming a PDC drilling bit including the steps of imposing a side drilling direction on the bit, determining a total bit side force acting on the bit, computing a walk angle between the total side force and the side drilling direction, and modifying a configuration of cutters on the profile of the bit so as to change the walk angle to a desired angle. The step of determining a total side force includes the steps of determining a normal side force of the bit, computing a total cutter friction force, and combining the normal side force and the total cutter friction force so as to produce a total side force. The total cutter friction force is obtained by summing single cutter forces perpendicular to a direction of cut of the bit. The step of imposing a side drilling direction includes measuring a normal side force applied to the bit. The modification of the bit can be carried out by increasing or reducing the aggressiveness of the cutters facing outwardly on an outer surface of the bit or by replacing cutters on the bit with low friction pads.
86 Citations
10 Claims
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1. A method of trajectory control of a PDC (Polycrystalline Diamond Compact) drill bit attached at the bottom of a drill string used for drilling a borehole through an earth strata formation and thereby achieve a predetermined intended path of PDC bit controlled trajectory comprising the steps of:
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determining a drill bit path or trajectory deviation tendency for the PDC drill bit; determining side forces and bending moments of the PDC drill bit; estimating response characteristics of the PDC drill bit for a given bit advance in the downward axial direction based upon the determined side forces and bending moments and on the determined bit deviation tendency; and controlling a simultaneous and/or subsequent lateral movement of the PDC drill bit relative to the estimated response for said PDC drill bit undergoing a given bit advance so as to compensate for drill bit path or trajectory deviation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification