METHODS AND SYSTEMS FOR DESIGNING AND/OR SELECTING DRILLING EQUIPMENT USING PREDICTIONS OF ROTARY DRILL BIT WALK
First Claim
1. A method for determining bit walk rate of a rotary drill bit comprising:
- applying a set of drilling conditions to the bit including at least bit rotational speed, rate of penetration along a bit rotational axis, and at least one characteristics of an earth formation;
applying a steer rate to the bit;
simulating, for a time interval, drilling of the earth formation by the bit under the set of drilling conditions, including calculating a steer force applied to the bit and an associated walk force;
calculating a walk rate based on the bit steer rate, the steer force, and the walk force;
repeating simulating drilling the earth formation for another time interval, and recalculating the steer force, the walk force and walk rate;
repeating the simulating successively for a predefined number of time intervals; and
calculating an average walk rate of the bit using an average steer force and an average walk force over the simulated time interval.
1 Assignment
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Accused Products
Abstract
Methods and systems may be provided simulating forming a wide variety of directional wellbores including wellbores with variable tilt rates and/or relatively constant tilt rates. The methods and systems may also be used to simulate forming a wellbore in subterranean formations having a combination of soft, medium and hard formation materials, multiple layers of formation materials and relatively hard stringers disposed throughout one or more layers of formation material. Values of bit walk rate from such simulations may be used to design and/or select drilling equipment for use in forming a directional wellbore.
96 Citations
42 Claims
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1. A method for determining bit walk rate of a rotary drill bit comprising:
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applying a set of drilling conditions to the bit including at least bit rotational speed, rate of penetration along a bit rotational axis, and at least one characteristics of an earth formation; applying a steer rate to the bit; simulating, for a time interval, drilling of the earth formation by the bit under the set of drilling conditions, including calculating a steer force applied to the bit and an associated walk force; calculating a walk rate based on the bit steer rate, the steer force, and the walk force; repeating simulating drilling the earth formation for another time interval, and recalculating the steer force, the walk force and walk rate; repeating the simulating successively for a predefined number of time intervals; and calculating an average walk rate of the bit using an average steer force and an average walk force over the simulated time interval.
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2-6. -6. (canceled)
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7. A method for determining bit walk rate of a rotary drill bit comprising:
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applying a set of drilling conditions to the bit including at least bit rotational speed, rate of penetration along a bit rotational axis, and at least one characteristics of an earth formation; applying a steer rate to the bit; simulating, for a time interval, drilling of the earth formation by the bit under the set of drilling conditions, including calculating a steer moment applied to the bit and an associated walk moment; calculating a walk rate based on the bit steer rate, the steer moment, and the walk moment; repeating simulating drilling the earth formation for another time interval, and recalculating the steer moment, the walk moment and walk rate; repeating the simulating successively for a predefined number of time intervals; and calculating an average walk rate of the bit using an average steer moment and an average walk moment over the simulated time interval. - View Dependent Claims (8)
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9-11. -11. (canceled)
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12. A method to design a rotary drill bit with a desired bit walk rate comprising:
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(a) determining the drilling conditions and the formation characteristics to be drilled by the bit; (b) simulating drilling at least one portion of a wellbore using the drilling conditions; (c) calculating the average bit walk rate; (d) comparing the calculated bit walk rate to the desired walk rate; (e) if the calculated walk rate does not approximately equal the desired walk rate, modifying at least one bit geometry of the rotary drill bit selected from the group consisting of bit profile, cutter location, cutter orientation, cutter density, gauge length, gage diameter; and (f) repeating steps (a) through (e) until the calculated walk rate approximately equals the desired walk rate. - View Dependent Claims (13, 14, 15)
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16-27. -27. (canceled)
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28. A method to select a rotary drill bit to drill at least one portion of a wellbore having at least one desired trajectory comprising:
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(a) determining a desired walk rate to compensate for the desired trajectory of the at least one portion of the wellbore; (b) determining at least one formation property of the at least one portion of the wellbore; (c) determining a first set of bit operational parameters according to capability of an associated drilling system and experience gained by drilling other wellbores with similar formation properties; (d) choosing a first rotary drill bit; (e) calculating a walk rate for the first rotary drill bit under the first set of bit operational parameters and comparing the calculated walk rate with the desired walk rate; (f) choosing a second rotary drill bit; and (g) repeating steps (e) and (f) until the calculated walk angle for at least one rotary drill bit is approximately equal to the desired walk rate under the first set of bit operational parameters. - View Dependent Claims (29, 30)
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31. A method for designing a rotary drill bit having a gauge comprising:
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(a) determining formation properties such as transition layer strength and inclination angle for use in simulating drilling with the rotary drill bit; (b) determining drilling conditions for use in simulating drilling with the rotary drill bit; (c) determining if the rotary drill bit will be used with a point-the-bit or push-the-bit drilling system; (d) simulating applying a steering motion, a relative shorter bent length, axial penetration and rotation forces to the rotary drill bit when used with a point-the-bit drilling system; (e) simulating applying steering motion, a relative longer bent length, axial penetration and rotation forces to the rotary drill bit when used with a push-the-bit drilling system; (f) calculating a walk rate based on the simulated drilling; (g) comparing the calculated walk rate with a desired walk rate; (h) if the calculated walk rate is not approximately equal to the desired walk rate, changing a bit geometry such as bit profile, cutter locations and orientations, cutter density or changing a geometric parameter of the gauge such as gauge length, gauge radius, gauge taper angle and gauge blade spiral angle; and (i) repeating steps (c) to (h) until the calculated walk rate approximately equals the desired walk rate. - View Dependent Claims (32, 33, 34, 35)
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36. A rotary drill bit with desired walk characteristics comprising:
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a bit face profile designed for use in a directional drilling system; the bit face profile defined in part by a plurality of blades with a plurality of cutters disposed on each blade; the bit face profile further defined by a recessed portion disposed on one end of the rotary drill bit; a nose disposed adjacent to the recessed portion with a shoulder portion extending outward from the nose portion; a plurality of inner cutters disposed within the recessed portion and a plurality of cutters disposed on the shoulder portion of the rotary drill bit; and the ratio between the number of inner cutters and the number of outer cutters based upon calculation and comparison of various walk rates for the rotary drill bit corresponding with respective ratios of inner cutters and shoulder cutters. - View Dependent Claims (37, 38, 39, 40)
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41. A rotary drill bit with a walk rate comprising:
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a bit body having a plurality of blades extending therefrom; each blade having a plurality of cutters disposed thereon; and the location, number, size and type of cutter disposed on each blade providing means for optimizing the walk rate of the rotary drill bit while forming a directional wellbore. - View Dependent Claims (42)
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Specification