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.

Abstract: A pair of stabilizers are placed in a string of drill pipe having a drill bit or a coring bit at its lower end, the placement of the stabilizers being such that the distance (d1) between the midpoint (mean transverse section) of the gauge surface of the bit and the midpoint (mean transverse section) of such first stabilizer bears a relationship to the distance (d2) between the midpoints of the two stabilizers. The ratio of d1 to d2 (d1/d2) should be between 1/1.5 to 1/5, and preferably between 1/2 and 1/3, with d1 being maintained less than five feet, preferably less than three feet. In one embodiment, the drill bit and the two stabilizers are formed in a monoblock.

Abstract: A method determining a tool face angle of a downhole drilling assembly in a well bore including the steps of determining an apparent tool face angle, measuring torque at least at one downhole axial location along the drillstring in the well bore, correlating a change in the apparent tool face angle relative to a change in the torque so as to produce a graphical curve of the correlation, and identifying a slope discontinuity along the graphical curve. The slope discontinuity is indicative of a contact resistance between the drillstring and the well bore. This method further includes the steps of determining a differential twist angle from the graphical curve and inferring a true tool face angle by subtracting the differential twist angle from the apparent tool face angle. The step of determining the apparent tool face angle includes measuring the inclination angle and azimuth angle of the well bore. The torque is measured at substantially the same axial location as the apparent tool face angle.

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.

Abstract: A drilling torque and drag monitoring method for a drillstring in a well bore including the steps of measuring hook load and axial displacement of the drillstring, measuring surface torque and angular position of the drillstring, correlating the hook load with the axial displacement of the drillstring so as to produce a first graphical relationship, correlating the surface torque and the angular position measurements of the drillstring so as to produce a second graphical relationship, and comparing the first and second graphical relationships so as to determine a contact resistance between the drillstring and the well bore. These relationships can be used independently or jointly so as to determine the condition of contact resistance. The method includes the step of identifying a slope discontinuity along the graphical curve. This slope discontinuity is indicative of a contact resistance.

Abstract: An apparatus and method for use in determining drilling conditions in a borehole in the earth having a drill string, a drill bit connected to an end of the drill string, sensors positioned in a cross-section of the drill string axially spaced from the drill bit, and a processor interactive with the sensors so as to produce a humanly perceivable indication of a rotating and whirling motion of the drill string. The sensors serve to carry out kinematic measurements and force resultant measurements of the drill string. The sensors are a plurality of accelerometers positioned at the cross-section. The sensors can also includes a plurality of orthogonally-oriented triplets of magnetometers. A second group of sensors is positioned in spaced relationship to the first group of sensors along the drill string. The second group of sensors is interactive with the first group of sensors so as to infer a tilting of an axis of the drill string.

Abstract: A method is provided for generating an improved torque-drag model for at least the collar portion of the drill string in a directional oil or gas well. The techniques of the present invention determine the stiffness of incremental portions of the drill string, and uses this information, the borehole clearance, and the borehole trajectory to determine the contact locations between the drill string and the sidewalls of the well. The contact force at these determined locations can be calculated, taking into consideration all significant kinematic, external, and internal forces acting on that incremental portion of the drill string. More acurate torque-drag analysis provided by the improved model of the present invention assists in well planning, prediction, and control, assists in avoiding drilling problems, and reduces total costs for the well.

Abstract: A method is provided for generating an improved torque-drag model for at least the collar portion of the drill string in a directional oil or gas well. The techniques of the present invention determine the stiffness of incremental portions of the drill string, and uses this information, the borehole clearance, and the borehole trajectory to determine the contact locations between the drill string and the sidewalls of the well. The contact force at these determined locations can be calculated, taking into consideration all significant kinemataic, esternal, and internal forces acting on that incremental portion of the drill string. More acurate torque-drag analysis provided by the improved model of the present invention assists in well planning, prediction, and control, assists in avoiding drilling problems, and reduces total costs for the well.

Abstract: A method is provided for generating an improved torque-drag model for at least the collar portion of the drill string in a directional oil or gas well. The technique of the present invention determine the stiffness of incremental portions of the drill string, and uses this information, the borehole clearance, and the borehole trajectory to determine the contact locations between the drill string and the sidewalls of the well. The contact force at these determined locations can be calculated, taking into consideration all significant kinematic, external, and internal forces acting on that incremental portion of the drill string. More acurate torque-drag analysis provided by the improved model of the present invention assists in well planning, prediction, and control, assists in avoiding drilling problems, and reduces total costs for the well.

Abstract: The methods disclosed herein incorporate the basic concepts and methodologies of a new general rock-bit interaction model useful in predicting and controlling drilling trajectories in directional (and deep vertical) wells. It accounts for the anisotropic drilling characteristics of both the formation and the bit. The model is developed in a 3-D geometry. Therefore, it is capable of predicting the walk tendency and the build-drop tendency of a given BHA (bottomhole assembly) under any drilling condition. The model can be used in the forward mode to predict the drilling direction; in the inverse mode to generate the rock and bit anisotrophy indices; and in the log-generation mode to generate drilling logs, such as a drilling dip log.

Abstract: A method and apparatus for obtaining complete loading on a drill bit at the end of a drill string in a borehole employ at least three rosette strain gauges uniformly disposed on an instrument sub to measure torque and axial force on the sub, two bending moments in mutually perpendicular directions, and two shear forces in mutually perpendicular directions. These measurements are used to obtain torque on bit, weight on bit, two side forces on the bit normal to each other, and two bending moments on the bit normal to each other which, in turn, can be used to control the bit movement.