Bi-center and bit method for enhancing stability
AssigneeDiamond Products International, Inc.
InventorCoy Fielder
Life of this patent
Estimating the term…
Abstract
An improved bi-center with improved directional stability and wear resistance is disclosed, said bit optimally utilizing a plurality of shaped PDC cutting elements selectively situated about the cutting surfaces of the pilot and the reamer to produce a minimal force imbalance, where further said pilot bit and the reamer are force balanced to further reduce imbalance in the operation of the tool.
Claims27
A bi-center bit having enhanced stability comprising:
- a body defining a proximal end adapted for connection to a drill string and a distal end, where said distal end defines a pilot and an intermediate reamer section and where both the pilot and the reamer section define cutting surfaces, said body having a varying radius "r" as measured along the length of the bit as measured from its axis, where further both said pilot and said reamer section are provided with a plurality of upsets to receive cutter assemblies;
- a plurality of shaped PDC cutter assemblies disposed on the cutting surfaces of the pilot bit and the reamer, where each assembly includes a PDC portion and a body portion, where each PDC portion includes a volume V of polycrystalline diamond, said PDC assemblies being mounted along each of the upsets such that the shaped PDC portion of each assembly extends outwardly a respective engagement distance from said upsets to act as a penetration limiter;
- said shaped PDC cutters being radially situated about the cutting surfaces of the pilot and reamer section in accordance with an abrasive wear analysis of the bit as dictated by the quotient of the product of a constant K and the volume V as divided by the square of the radius of the bit at any given point along the axis;
- said shaped PDC cutters being angularly situated about the cutting surfaces of the pilot and the reamer section in accordance with the vertorial sum of the forces normal to the bit F.sub.N, the vertical forces acting on the bit F.sub.V and the bit torque F.sub.X ;
- and
- said reamer section then being positioned relative to said pilot so as to minimize the cutting force imbalance as measured between said pilot and the reamer section.
A method for enhancing the stability of a bi-center bit assembly when drilling in a borehole through a formation, where said bit comprises a body having a proximal end which is operatively engageable to the drill string and a distal end which defines a pilot, where further one side of said body intermediate the distal end and the proximal end defined a reamer section, where both said pilot and reamer section define a cutting surface, said method comprising the steps of:
- providing a plurality of shaped PDC cutter assemblies about the cutting surfaces on both the pilot and reamer section, where each assembly includes a PDC portion and a body portion;
- providing a plurality of upsets extending along the cutting surfaces of both the pilot and the reamer section;
- radially mounting said shaped PDC cutter about the cutting surfaces of the pilot and reamer section in accordance with an abrasive wear analysis of the bit as dictated by the quotient of the product of a constant K and the volume V as divided by the square of the radius of the bit at any given point along the axis;
- angularly situating the PDC cutter about the cutting surfaces of the pilot and reamer section in accordance with the vectorial sum of the forces normal to the bit F.sub.N, the vertical forces acting on the bit F.sub.V and the bit torque F.sub.X ;
- and
- positioning said reamer section relative to said pilot on said body to minimize the cutting force imbalance between the pilot and the reamer section.
A bi-center bit having enhanced stability comprising:
- a body defining a proximal end adapted for connection to a drill string and a distal end, where said distal end defines a pilot bit and an intermediate reamer section, where both the pilot bit and the reamer section possess cutting surfaces, said reamer section defining a leading cutting surface and one or more trailing surfaces;
- a plurality of cutter assemblies being radially disposed about the cutting surfaces of the pilot bit and the reamer section;
- said cutter assemblies angularly situated about the cutting surfaces of the pilot and the reamer section to minimize the resultant of the vectorial sum of the forces normal to the bit F.sub.N, the vertical forces acting on the bit F.sub.V and the bit torque F.sub.X, said reamer section being positioned relative to said pilot bit so as to further minimize the cutting force imbalance as measured between said pilot bit and said reamer section;
- and
- positioning shaped cutting assemblies about the leading cutting surface of the reamer along the line defined by the resultant force of the pilot bit and the reamer section to further minimize the force imbalance.
A method for enhancing the stability of a drill bit assembly when drilling in a borehole through a formation, where said bit comprises a body having a proximal end which is operatively engageable to the drill string and a distal end which defines a pilot bit, where further one side of said body intermediate the distal and the proximal ends defines a reamer section, where both said pilot and reamer sections defined a series of cutting surfaces, said method comprising the steps of:
- radially mounting a plurality of cutter assemblies about the cutting surfaces of the pilot bit and reamer section;
- angularly situating said cutter assemblies about said cutting surfaces so as to minimize the resultant of the vectorial sum of the forces normal to the bit F.sub.N, the vertical forces acting on the bit F.sub.V and the bit torque F.sub.X.
Dependencies are inferred from the claim text.