Classifications

• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B7/00—Special methods or apparatus for drilling
  • E21B7/04—Directional drilling
  • E21B7/06—Deflecting the direction of boreholes
  • E21B7/064—Deflecting the direction of boreholes specially adapted drill bits therefor
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B10/00—Drill bits
  • E21B10/62—Drill bits characterised by parts, e.g. cutting elements, which are detachable or adjustable
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B17/00—Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Cables; Casings; Tubings
  • E21B17/10—Wear protectors; Centralising devices, e.g. stabilisers
  • E21B17/1092—Gauge section of drill bits
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B7/00—Special methods or apparatus for drilling
  • E21B7/04—Directional drilling
  • E21B7/06—Deflecting the direction of boreholes
  • E21B7/068—Deflecting the direction of boreholes drilled by a down-hole drilling motor

Definitions

• This invention relates to a drilling system for use in the formation of boreholes, for example for the subsequent extraction of oil or natural gas.
• the invention relates, in particular, to a system which is capable of being steered so as to allow the path followed, during formation of the borehole, to be controlled.
• a number of steerable drilling systems are known.
• One such system comprises a bias unit connected to a drill bit.
• the bias unit includes a number of movable pads, the pads each being movable, in use, between a retracted position and an extended position. Each pad, when in its extended position, bears against the wall of the borehole, applying a laterally acting foice to part of the bias unit and to the drill bit carried thereby.
• the pads are typically arranged to be moved by associated pistons to which fluid under pressure, typically drilling fluid or mud, is supplied through a control valve arrangement.
• fluid under pressure typically drilling fluid or mud
• the bias unit and drill bit are rotated, for example by a downhole motor or by rotation of the associated drill string.
• the pads are moved from their retracted positions to their extended positions in turn in synchronism with the rotation of the bias unit, and this is achieved through appropriate control of the control valve.
• Other systems operate by pointing the bit in the desired drilling direction instead of pushing the bit to form a curve oriented in the desired direction. These systems all make use of devices located behind the bit which are generally relatively complex and costly.
• Another system makes use of the weight-on-bit applied to the bit to achieve a degree of steering.
• a stabiliser is located close to the bit.
• a change in the applied weight-on-bit causes the bit to tilt about the stabiliser, causing a change in the inclination thereof.
• a steerable drilling system comprising a drill bit comprising a bit body having at least one first movable member and- a control arrangement to allow the position occupied by the first movable member to be adjusted to control the drilling direction of the bit, in use.
• the control arrangement is preferably arranged to adjust the position of the first movable member in a phased relationship with the rotation of the bit with respect to the formation.
• the bit body may further include at least one second movable member, movable independently of the or each first movable member.
• the first and second movable members may comprise movable gauge pads of the drill bit movable between radially retracted and extended positions.
• the first and second movable members may comprise movable cutting blades of the bit. In either case, adjustment of the positions occupied by the movable members may be used to apply a laterally acting load to the bit body and thereby adjust the drilling direction.
• the bit may be designed such that adjustment of the position of the first movable member results in an alteration in the out-of -balance forces at the bit, this alteration arising due to the cutting structure changing as the movable member is moved.
• the drilling direction can be altered.
• One or rn ⁇ ie further m ⁇ veable members may also be provided.
• a further possibility is to control the position of the first movable member to control the walk angle of the bit, and to control the applied weight-on-bit to control the inclination of the bit.
• Such an arrangement is advantageous in that it does not require the bit cutting structure to be modified in a phased relationship with the rotation of the bit, and so allows a much simpler control arrangement to be used.
• a steerable drilling system for drilling a hole in a formation in a desired direction, the system comprising a drill bit having a bit body, the bit body including at least one cyclically movable member arranged to interact, in use, directly or indirectly, with the formation, a measurement system operable to determine the actual direction of propagation of the hole, and a control system operable to adjust the phase of cyclic movement of the movable member to bring the actual direction of propagation into agreement with the desired direction.
• the invention also relates to a method of drilling a hole in a formation in a desired direction using a drill bit having a bit body including at least one cyclically
• movable member arranged to interact, directly or indirectly, with the formation, the method comprising sensing the actual direction of propagation of the hole and adjusting the phase of cyclic movement of the movable member to bring She actual direction of propagation into agreement with the desired direction.
• Figure 1 is a diagrammatic view illustrating part of a steerable drilling system in accordance with one embodiment of the invention, in use;
• Figure 2 illustrates, diagrammatic ally the drill bit of the embodiment of Figure
• FIGS 3 and 4 illustrate alternative designs of drill bit
• FIG. 8 illustrates another embodiment
• FIG. 9a and 9b illustrate another embodiment
• FIGS. 10a, 10b and IOc illustrate further embodiments r ⁇
• FIGS. 1 1-3. and 1 Ib illustrate another embodiment
• Figure 12 illustrates a further embodiment.
• the steerable drilling system illustrated, in part, in Figure 1 comprises a drill bit 10 forming part of a bottom hole assembly arranged to be rotated from the drilling rig's top drive or rotary table.
• the assembly 12 is carried by a drill string 14 incorporating a number of other downhole components, for example downhole stabilisers, sensors and the like.
• the drill bit 10 comprises a bit body 16 from which a plurality of upstanding blades 18 extend.
• Each blade 18 is provided with a series of cutting elements 20 arranged such that, in use, upon rotation of the drill bit whilst an axially directed load is applied thereto, the cutters 20 serve to gouge, abrade, or scrape material from the formation in which the borehole is being formed.
• Drilling fluid is supplied to the drill bit 10 and discharged through nozzles (not shown) arranged to direct drilling fluid so as to flow over and around the cutting elements 20 for the purposes of cooling and cleaning the cutting elements 20.
• the drilling fluid is supplied to the drill bit 10 under pressure, and after serving to clean and cool the cutters 20, the fluid returns to the surface, or to another location, carrying the removed formation material with it.
• the bit body 10 is provided with at least one radially movable member in the form of a movable blade 22, the movable blade 22 being movable -between- a radially retracted position as indicated by the full- lines in Figure 1 ' and a radially extended position as illustrated by the dotted line in Figure 2.
• the movable blade 22 is movable between these positions by me-,a:is of a piston 24 movable within a cylinder 26. Drilling fluid under pressure is supplied, in use, to the cylinder 26 through supply lines 28 and a control valve 30, the control valve 30 controlling the timing of such supply.
• a restricted flow passage (not shown) is provided to allow fluid to escape from the cylinder 26, and thereby allow the blade 22 to return to its retracted position.
• control valve 30 In use, when it is desired to effect a change in direction in which drilling is occurring, the control valve 30 is operated, repeatedly, so as to supply drilling fluid under pressure to the cylinder 26 and thereby urge the blade 22 to its radially extended position, and allow the fluid to escape allowing the blade 22 to return to its retracted position, in synchronism with the rotation of the drill bit 10 such that the blade 22 always occupies its extended position when the drill bit 10 is in the same angular position relative to the surrounding formation and occupies its retracted position at other times.
• the blade 22 may be devoid, at its outer radial part, of cutters, or alternatively cutters may be provided at the outer radial part thereof. Where the outer radial part of the blade 22' is- provided with cutters 1 ; then the' 'borehole- being formed will partially propagate in the direction in which the blade 22 is displaced. Where the outer radial part of th ⁇ - -blade 22 is not provided with cutters and is essentially blunt, then the movement of the blade 22 will- serve to urge the remainder of the bit, and the direction of propagation of the borehole, in the opposite direction.
• sensors 34 are associated with the bit, or are located elsewhere, which are sensitive to the direction in which the borehole is propagating.
• the output of the sensors 34 may be used by a control unit 36 which serves to control the operation of the control valve arrangement 30.
• the control unit 36 can vary the phase at which the control valve arrangement 30 causes movement of the blade 22 to steer the bit, and hence the direction of propagation, in the desired direction. This can be achieved without full apriori knowledge of the complex motion of the bit described above.
• the control valve arrangement 30 could take a range of forms. For example, it could comprise a rotary valve, a control shaft of which is connected to a suitable roll stabilised platform or component or to the output of a suitably controlled motor. Another possibility is to use an appropriate bi-siable actuator/valve arrangement. " For * example, a low-power, electrically operated actuator could be used to control a suitable mud-valve which, in turn, controls the supply of fluid 'I ' uder pressure to the cylinder 26 and associated piston 24. The actuator and/or the valve may be designed to be of bistable form. However, a range of other arrangements are possible.
• FIG. 2 only illustrates the provision of a single movable blade 22, it will be appreciated that a plurality of such blades may be provided, each movable blade being independently movable between its retracted and extended position under the control of, for example, the control valve 30.
• Alternative techniques for moving the movable blade may be employed, including bi-stable arrangements, for example as outlined above, designed so that, once the blade is moved to its extended position it will remain in that position, without requiring the continued application of energy thereto, until it is desired to retract the blade.
• Other possibilities include using shape memory alloys, piezzo electric devices and magneto restrictive or rheological materials to cause the blade to move and/or to hold the blade against movement in both its extended and retracted positions.
• the techniques used to move the moveable members may be bi-stable in operation, but this need not always be the case.
• the movable blade 22 is shown as being translatable, radially, between its extended and retracted positions, it could be designed so as to be pivotally, or otherwise, movable.
• the blades may also be movable in other directions. For example ⁇ they could be movable -side-to-sider - Figures 1 Ia and 1 Ib illustrate • an arrangement in which the movable blade 22 is pivotally mounted upon the bit body 10, the blade. 22 being pivotally movable about an axis 22a to move the blade between a retracted position (illustrated in the full lines in Figure lla) and an extended position
• the axis 22a lies substantially parallel to the axis of the bit body 10.
• Figure 2 the blade 22 is moved using a piston 24 slidable within a cylinder 26, fluid under pressure being supplied to the cylinder 26, in use, through a suitable valve arrangement, allowing the operation of the bit to be controlled in a manner similar to that described hereinbefore.
• Figure 12 illustrates another, similar, possibility in which the blade 22 in pivotally mounted to the bit body 10, the pivot axis 22a being substantially perpendicular to the axis of the bit body 10, in this arrangement.
• Figure 3 illustrates an alternative embodiment in which rather than provide the bit 10 with one or more movable blades 22, the bit 10 is provided with one or more movable members in the form of movable gauge pads .32 movable between radially retracted and radially extended positions in a manner similar to the manner in which the movement of the blades 22 is triggered. Control over the steering direction achievable using such a bit is achieved in a manner very similar to that described hereinbefore and with reference to Figures 1 and 2. It will be appreciated that any of the techniques outlined hereinbefore may be employed to move the movable gauge pads.
• the cutters When using a drill bit having no moving parts, the cutters are typically arranged on the bit in an asymmetric pattern, and thus the bit is out-of-balance.
• the result of this is-thatj-when drilling straight-ahead, the- overall motion of the' bit is straighrahead but with a small scale helical motion superimposed on to the straight ahead movement. If the symmetry of the bit can be changed, in use-; in phased relation to the rotation of the bit, then the out-of-balance forces can be used to urge the bit -in a- constant, chosen direction and thereby to achieve steering thereof.
• FIG. 4 illustrates a drill bit designed to operate ill this manner and comprising a bit body 42 having a plurality of blades 44 provided thereon. Each blade 44 carries a series of cutting elements 46. One or more of the blades 44 includes a movable member in the form of a movable component 48 upon which some of the cutting elements 46 are mounted.
• the movable component 48 is movable by means of a piston arrangement to which drilling fluid under pressure can be supplied by a suitable control valve arrangement, but could alternatively be moved using any of the other techniques outlined hereinbefore.
• the design of the drill bit is such that when the movable component 48 occupies its extended position, and so the cutters mounted thereon engage the formation in which the borehole is being formed, the out-of-balance forces are different to when the movable component 48 occupies its retracted position.
• the bit may be substantially balanced when the movable component 48 occupies its extended position, and out-of-balance when the movable component is retracted. When out-of-balance, a laterally acting force is applied to the bit, in use. It will be appreciated that by moving the movable component 48 between its extended and retracted position in synchronism
• the design of the bit could be such that retraction of the component 48 results in the bit becoming more, rather than less, balanced.
• Figure 4 only illustrates the provision of one movable component, more such components may be provided.
• the position(s) need not be as illustrated, and may be chosen to suit the bit design.
• the manner in which the component is moved need also not be as illustrated, and systems other than hydraulically powered systems may be used.
• the number of cutters on the movable components could be changed, and even whole blades or sets of blades could be moved, if desired. Where two or more blades are movable, movement thereof could be controlled independently to allow very good control over the out-of-balance forces.
• FIGS 5 to 7 illustrate a drill bit in accordance with another embodiment of the invention.
• a drill bit is provided which includes a plurality of fixed blades 50 on which cutters 52 are mounted.
• the bit further includes, on the blades 50, a series of gauge pad regions 54.
• At least one movable member is provided in the form of a movable gauge pad region 54a which is radially movable between a retracted position as shown in Figure 6 and an extended position as shown in Figure 7. In the retracted position, the cutters 52 provided on the blades 50 adjacent the gauge pad region 54a are exposed to the formation being drilled, these cutters 52 becoming
• gauge pad region 54a can be moved in synchronism with the rotation of the bti such that the out-of-balance force is varied in synchronism with the rotation of the bit, thereby enabling control over the drilling direction.
• the movable gauge pad region 54a may be adapted to bear against the formation being drilled and thereby apply a sideway acting load to the bit, the gauge pad region 54a again being moved in synchronism with the rotation of the drill bit.
• one or more of the blades 50 may be movable to control the exposure of at least some of the cutters 52 to control out-of-balance forces and consequently drilling direction.
• the movable gauge pad or blade (or part thereof) need not be in the position or location illustrated, for example a part of a blade located at the face of the bit may be movable.
• the movable gauge pad or blade may be designed to be replaceable and/or disposable- whilst utlierpails of the bit'aie re-used. They could be "constructed using superhard materials such as PDC, TSP, tungsten carbide or provided " with a diamond coating.
• the bit is provided with a cavity 60 supplied, in use, with drilling fluid or mud.
• the pressure at which the drilling fluid or mud is supplied can be controlled by controlling, for example, the operation of the pumps used to deliver the fluid or using, for example, appropriately located and controlled valves.
• the bit wall thickness is non-uniform around the cavity 60, the bit including regions 62 of relatively great wall thickness and at least one region 64 of relatively low wall thickness.
• the wall thicknesses are chosen such that the regions 62 deflect or deform very little when the pressure within the cavity 60 varies, such pressure variations causing relatively large deflections to occur in the region or regions 64.
• the solid lines show the bit when the cavity 60 is at low pressure, the broken lines illustrating the bit when the cavity 60 is at an increased pressure. For clarity, the deflection is exaggerated in Figure 8.
• the bit carries cutters 66. It will be appreciated that some of the cutters 66 are moved upon deflection of the region 64, varying the out-of-balance forces on the bit and thereby enabling control over steering, or cutting into the formation at varying depths to achieve steering of the bit, the deflection being controlled to occur in synchronism with the rotation of the bit.
• deflection of the region 64 is "used- to move-some of the c ⁇ tters 66, it could alternatively be used "to move a. gaugepad region to vary the exposure of nearby cutters.
• Figures 9a and 9b illustrate an alternative ⁇ way of varying the exposure of cutters, comprising providing a bit with an inflatable cutter cover 68.
• Figure 9a illusLrates the cover 68 in a deflated condition in which the adjacent cutters- 70 are exposed
• Figure 9b illustrating the cover -68 in an inflated condition in which the adjacent cutters 70 are rendered inactive thereby avoiding cutting by those cutters.
• Figures 10a, 10b and 10c illustrate arrangements in which individual cutters 72 are movable between extended and retracted positions, the cutters 72 being mounted in bores or sockets 74 formed in a rigid bit body. Drilling fluid is applied to an inner end of each cutter 72 urging the cutter towards its extended position.
• Figure 10b illustrates the use of springs 76 urging the cutters 72 towards their retracted positions, the cutters 72 moving to their extended positions when the fluid pressure exceeds a predetermined level. When extended, the cutters cut more deeply into the formation, and by moving the cutters in time with the rotation of the bit, steering control over the hole being formed can be achieved.
• Figure 10c illustrates an arrangement in which, when the pressure drops below a predetermined threshold, the cutters 72 retract to a position in which they are not exposed.
• a range of other steering techniques may be used with drill bits having components movable in a phased relationship with the rotation of the drill bit.
• the cutting structure could be controlled, in use, so as to produce a drill bit having a phased controlled asymmetry of hole propagation.
• One way in which this may be achieved is to provide the bit with one or more movable components in the form of snubbers, movable to limit the depth of cut of the bit.
• Another way is to move the cutters instead of, or in conjunction, with the moveable snubbers.
• the movable components are movable, as with the other embodiments, in a phased relationship with the rotation of the drill bit so as to vary the depth of cut across the face of the bit in phase with the rotation of the drill bit causing the bit to be laterally disturbed due to the imbalance of rock removal and imbalance forces.
• the control system is arranged to determine the relationship of hole propagation to the phase of cutter/snubber variation and to adjust the phase accordingly to achieve the desired steering objectives. As a result, a preferred off axis drilling direction can be achieved.
• Other techniques of controlling the direction of hole propagation by phase control of aspec ⁇ s ⁇ ⁇ f rock or formation removal by the" bit are also" possible "within the scope of the invention.
• Another possibility is to use a bit with a fixed cutting structure and arrange for it to be dynamically pointed about a pivot point set within the bit in a phase controlled relationship to the formation.
• the pivot point is a 2 degree, of freedom universal joint allowing the bit axis to be tilted (typically less than 10 degrees) with respect to the local drill string central axis and capable of transmitting the drilling load and torques to the bit.
• This is different from conventional point the bit directional drilling systems in that the centre point of the bit experiences negligible lateral offset from the drill string central axis as the bit drilling axis is tilted.
• An alternative to using a complex system of this type is to control a bit, for example bits of the general type illustrated in Figures 3 and 4, in such a way that a change in the fluid pressure drop across the bit causes movement of adjustment of at least part of the cutting structure of the bit, causing a change in the bits profile , and as a result changing the bit's walk angle.
• the bit is connected to a downhole stabiliser arranged such that a change in the weight-on-bit applied to the system causes the bottom hole ⁇ assembly, Or at least part thereof; TO "pivot or tilT ' about ' the stabilis ' er arid ' thereby changes the inclination of the bit.
• the bit or cutting structure is only changed when a new walk angle is required, rather than being modified in phase with the rotation of the bit, thus it can be used with a much simpler control system.
• the description hereinbefore describes one way of achieving movement of the movable components of the drill bits described, it will be appreciated that a range of other techniques for causing movement of the movable components may be used without departing from the scope of the invention.
• the bit is rotated for example using power derived from the drilling rig's top drive or rotary table, it could alternatively be connected to the output of a downhole motor, for example a fluid driven motor, turbine, electrical motor or the like.

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• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Geology (AREA)
• Mining & Mineral Resources (AREA)
• Physics & Mathematics (AREA)
• Environmental & Geological Engineering (AREA)
• Fluid Mechanics (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Mechanical Engineering (AREA)
• Earth Drilling (AREA)
• Drilling And Boring (AREA)

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Cited By (17)

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Citations (10)

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• 2005
  • 2005-07-27 GB GBGB0515394.5A patent/GB0515394D0/en not_active Ceased
• 2006
  • 2006-07-24 GB GB0614641A patent/GB2428713A/en not_active Withdrawn
  • 2006-07-26 EP EP06765124A patent/EP1977073B1/de active Active
  • 2006-07-26 WO PCT/GB2006/002803 patent/WO2007012858A1/en active Application Filing
  • 2006-07-26 AT AT06765124T patent/ATE513977T1/de not_active IP Right Cessation
  • 2006-07-26 CN CN200680027465.XA patent/CN101268246B/zh active Active

Patent Citations (10)

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