Methods and systems for designing and/or selecting drilling equipment using predictions of rotary drill bit walk
First Claim
Patent Images
1. A method for determining bit walk rate of a long gage 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 characteristic of an earth formation;
applying a steer rate to the bit by tilting the bit around a fulcrum point located on a sleeve located above the bit gage, wherein the fulcrum point is defined as a contact point between the sleeve and a wellbore;
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 at least on the steer force and the walk force;
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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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.
170 Citations
32 Claims
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1. A method for determining bit walk rate of a long gage 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 characteristic of an earth formation; applying a steer rate to the bit by tilting the bit around a fulcrum point located on a sleeve located above the bit gage, wherein the fulcrum point is defined as a contact point between the sleeve and a wellbore; 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 at least on the steer force and the walk force; 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. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for determining bit walk rate of a long gage rotary drill bit comprising:
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applying a set of drilling conditions to the bit including at least bit rotational speed, hole size and rate of penetration along a bit rotational axis and at least one characteristic of an earth formation; applying a steer rate to the bit, wherein applying the steer rate includes tilting the bit around a fulcrum point located at a top section of the bit gage; 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, 9, 10, 11)
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12. A method to design a long gage rotary drill bit with a desired bit walk rate comprising:
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(a) determining one or more drilling conditions and one or more formation characteristics of a formation to be drilled by the bit; (b) simulating drilling at least one portion of a wellbore having a wellbore diameter greater than the bit diameter, using the one or more drilling conditions; (c) calculating an average bit walk rate; (d) comparing the calculated bit walk rate to the desired walk rate; (e) if the calculated bit walk rate does not approximately equal the desired walk rate, performing the following steps; (f) dividing the bit body into at least an inner zone, a shoulder zone, a gage zone, an active gage zone and a passive gage zone; (g) calculating the walk rate of each zone; (h) calculating the walk rate of a first combined zone including the inner zone and the shoulder zone; (i) calculating the walk rate of a second combined zone including the active gage zone and the passive gage zone; (j) identifying the zone which has the maximal magnitude of walk rate and the zone which has the minimal magnitude of walk rate; (h) modifying one or more structures within the zone which has the maximal magnitude of walk rate or the zone which has the minimal magnitude of the walk rate; and (k) repeating steps (b) through (j) until the calculated bit walk rate approximately equals the desired bit walk rate. - View Dependent Claims (13, 14, 15, 16, 17)
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18. A method to find and optimize operational parameters to control bit walk of a long gage rotary drill bit during drilling of at least one portion of a wellbore comprising:
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(a) determining a bit path deviation for the at least one portion of the wellbore; (b) determining a desired bit walk rate to compensate for the bit path deviation; (c) determining downhole formation properties at a first location and at a second location ahead of the first location in the at least one portion of the wellbore; (d) simulating drilling with the rotary drill bit between the first location and the second location, wherein simulating drilling includes predicting a hole size greater than the bit size; (e) during the simulation applying to the rotary drill bit a steer rate; (f) calculating a walk rate of the rotary drill bit and comparing the calculated walk rate with the desired walk rate; and (g) changing at least one set of the bit operational parameters and repeating steps (d) through (f) until the calculated walk rate approximately equals the desired walk rate. - View Dependent Claims (19, 20, 21, 22, 23)
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24. A method for designing a long gage rotary drill bit having a gage and corresponding bit size, the method comprising:
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(a) determining one or more formation properties for use in simulating drilling with the bit; (b) determining one or more drilling conditions for use in simulating drilling with the bit; (c) simulating drilling using the one or more formation properties and the one or more drilling conditions, and wherein simulating drilling includes predicting a wellbore diameter greater than the bit size; (d) calculating a walk rate based on the simulated drilling; (e) comparing the calculated walk rate with a desired walk rate; (f) if the calculated walk rate is not approximately equal to the desired walk rate, changing a bit geometry or changing a geometric parameter of the gage; and (g) repeating steps (c) through (f) until the calculated walk rate approximately equals the desired walk rate. - View Dependent Claims (25, 26, 27, 28)
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29. A long gage rotary drill bit with a desired bit walk rate prepared by a process comprising:
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(a) determining one or more drilling conditions and one or more formation characteristics of a formation to be drilled by the bit; (b) simulating drilling at least one portion of a wellbore having a wellbore diameter greater than the bit diameter, using the one or more drilling conditions; (c) calculating an average bit walk rate; (d) comparing the calculated bit walk rate to the desired walk rate; (e) if the calculated bit walk rate does not approximately equal the desired walk rate, performing the following steps; (f) dividing the bit body into at least an inner zone, a shoulder zone, a gage zone, an active gage zone and a passive gage zone; (g) calculating the walk rate of each zone; (h) calculating the walk rate of a first combined zone including the inner zone and the shoulder zone; (i) calculating the walk rate of a second combined zone including the active gage zone and the passive gage zone; (j) identifying the zone which has the maximal magnitude of walk rate and the zone which has the minimal magnitude of walk rate; (h) modifying one or more structures within the zone which has the maximal magnitude of walk rate or the zone which has the minimal magnitude of the walk rate; (k) repeating steps (b) through (j) until the calculated bit walk rate approximately equals the desired bit walk rate; and (l) manufacturing the long gage rotary drill bit having the desired bit walk rate. - View Dependent Claims (30, 31)
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32. A long gage rotary drill bit having a gage and corresponding bit size, prepared by a process comprising:
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(a) determining one or more formation properties for use in simulating drilling with the bit; (b) determining one or more drilling conditions for use in simulating drilling with the bit; (c) simulating drilling using the one or more formation properties and the one or more drilling conditions, and wherein simulating drilling includes predicting a wellbore diameter greater than the bit size; (d) calculating a walk rate based on the simulated drilling; (e) comparing the calculated walk rate with a desired walk rate; (f) if the calculated walk rate is not approximately equal to the desired walk rate, changing a bit geometry or changing a geometric parameter of the gage; (g) repeating steps (c) through (f) until the calculated walk rate approximately equals the desired walk rate; and (h) manufacturing the long gage rotary drill bit having the desired bit walk rate.
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Specification