EP0467642A2 - Erdbohrsystem und Verfahren zum Steuern einer Bohrlochrichtung - Google Patents

Erdbohrsystem und Verfahren zum Steuern einer Bohrlochrichtung Download PDF

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Publication number
EP0467642A2
EP0467642A2 EP91306436A EP91306436A EP0467642A2 EP 0467642 A2 EP0467642 A2 EP 0467642A2 EP 91306436 A EP91306436 A EP 91306436A EP 91306436 A EP91306436 A EP 91306436A EP 0467642 A2 EP0467642 A2 EP 0467642A2
Authority
EP
European Patent Office
Prior art keywords
drill bit
bit
rotation
cutting structures
cutting
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP91306436A
Other languages
English (en)
French (fr)
Other versions
EP0467642A3 (en
Inventor
John Denzil Barr
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Camco Drilling Group Ltd
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Camco Drilling Group Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB909015704A external-priority patent/GB9015704D0/en
Priority claimed from GB919100874A external-priority patent/GB9100874D0/en
Application filed by Camco Drilling Group Ltd filed Critical Camco Drilling Group Ltd
Publication of EP0467642A2 publication Critical patent/EP0467642A2/de
Publication of EP0467642A3 publication Critical patent/EP0467642A3/en
Withdrawn legal-status Critical Current

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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
    • E21B10/42—Rotary drag type drill bits with teeth, blades or like cutting elements, e.g. fork-type bits, fish tail bits
    • E21B10/43—Rotary drag type drill bits with teeth, blades or like cutting elements, e.g. fork-type bits, fish tail bits characterised by the arrangement of teeth or other cutting elements
    • 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
    • E21B4/00—Drives for drilling, used in the borehole
    • E21B4/20—Drives for drilling, used in the borehole combined with surface drive
    • 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

  • the downhole assembly includes an asymmetrical unit which rotates with the drill string and not with the drill bit.
  • the asymmetrical unit may comprise a motor having a "bent" housing, a "bent" sub-assembly above the motor, or an offset stabiliser on the outside of the motor casing.
  • the rotational orientation of the motor casing is sensed by survey instruments carried adjacent the motor and the required rotational orientation of the motor casing (known as the tool face angle) for drilling in the appropriate direction is set by rotational positioning of the drill string, from the drilling platform, in response to the information received in signals from the downhole survey instruments.
  • British Patent Specifications Nos. 2172324 A, 2172325 A and 2177738 A disclose arrangements in which lateral forces are applied to a drilling tube above the drill bit so as to impart a curvature to the drilling tube and thereby control the drilling direction. Such arrangements are complex and require large downhole assemblies.
  • U.S. Specification No. 4995465 J. L. Beck and L. D. Taylor describes a rotary drilling system in which a bent-sub is connected behind the drill bit so that the bit extends angularly with respect to the drill rod.
  • An actuator such as an hydraulic ram, is provided at the surface for exerting thrust on the end of the drill rod which is transmitted along the rod to the drill bit.
  • the thrust applied along the drill rod is pulsed to effect the desired trajectory of the drilling.
  • the pulsing of the drill rod is based upon signals received from a downhole monitor.
  • the system is primarily contemplated for use in horizontal coal mine drilling where the length of the drill string, and hence the wind-up and reaction delay, are in practice considerably less than in oil well drilling. Since the bit is connected to the drill string through a bent sub, the bit does not rotate about the axis about which it was designed to rotate and does not therefore drill efficiently. When the bit is drilling normally, i.e. in a straight line, the bit dynamics are likely to be poor and only a part of the bit is likely to be cutting the formation.
  • U.S. Specification No. 4637479 (L. J. Leising) describes a roller-cone bit carried on a drilling tool in which a rotating flow-obstructing member controls the flow of drilling fluid to discharge passages in the drill bit. By varying the rate of rotation of the flow obstructing member, drilling fluid may be sequentially discharged from the bit passages into only a single peripheral sector of the borehole, and thereby divert the drill bit into a different path.
  • the present invention provides a novel system and method for directional drilling which is applicable to rotary drilling.
  • a drilling system for drilling or coring holes in subsurface formations comprising:
  • the operation of substantially all the cutting structures of the drill bit are preferably modified simultaneously by said modifying means.
  • the means for modifying the operation of the cutting structures may comprise means for cyclically varying an axial force applied to the bit body.
  • Said modifying means may comprise a hammer which applies repeated axial impulses to the bit at a frequency greater than the frequency of rotation thereof, means being provided for periodically varying the intensity of operation of the hammer in synchronism with the rotation of the drill bit.
  • the hammer may be switched on and off periodically in synchronism with the rotation of the drill bit.
  • the hammer may be a mud hammer including means for periodically restricting the flow of drilling fluid to the bit structure to create pulsations in said flow and thereby impart said repeated axial impulses to the bit structure.
  • the required phase relation between rotation of the drill bit and periodic operation of the modifying means may be selected by determining the instantaneous rotational orientation of the drill bit and setting the phase angle to provide operation, or maximum operation, of the modifying means at the appropriate rotational position of the drill bit to achieve displacement in the required direction.
  • the means for determining the instantaneous rotational orientation of the bit body may include downhole sensing means responsive to the instantaneous rotational orientation of the bit body, which sensing means sends signals, indicative of said instantaneous rotational position, to control means, also located downhole, for controlling said modifying means.
  • the instantaneous rotational orientation of the bit structure may be determined from the rotational position of the rotary table on the drilling platform, suitable allowance being made for wind-up of the drill string.
  • selection of the particular phase relation between rotation of the drill bit and periodic variation of the modifying means, and hence selection of the direction of deviation of the borehole may be effected automatically by a predetermined program responsive to information received from downhole surveying instruments supplying signals indicative of the direction of the borehole, the program being executed by processing means located downhole.
  • the aforesaid means for controlling the phase relation between rotation of the drill bit and periodic variation of the modifying means may include a downhole clock controlling the periodic operation of the modifying means, and a substantially synchronised clock at the surface, means being provided for varying the rotation of the drill bit in relation to said surface clock in a manner to achieve a desired phase angle.
  • the system may include a signal processor to which are supplied signals from said surface clock, as well as signals indicative of rotation of the drill bit and of the desired phase angle, said signal processor processing said signals and delivering to means controlling rotation of the bit a resultant signal to cause said means to vary rotation of the bit until said desired phase angle is achieved.
  • the processor being adapted to modify said resultant signal in accordance therewith, so as to compensate for said wind-up in controlling said phase angle.
  • the invention includes within its scope a method of controlling the direction of a hole being drilled or cored in a subsurface formation by a drill bit structure which is asymmetrically arranged, and which includes a bit body carrying a plurality of cutting structures, the method comprising:
  • the invention further provides a drilling system for drilling or coring holes in subsurface formations including:
  • the asymmetrical arrangement of the cutting structures may comprise an asymmetrical distribution of the cutting structures over the bit body.
  • the asymmetrical distribution of the cutting structures may be such that at least the major part of the cutting action of the drill bit is effected by outwardly facing cutting structures located in a region of the bit body which is offset to one side of a diametral axis thereof.
  • the profile of the surface generated by the cutting structures may be generally convex or conically shaped.
  • the asymmetrical distribution of the cutting structures may be such that at least the major part of the cutting action of the drill bit is effected by cutting structures which face generally in the same lateral direction.
  • the asymmetrical arrangement of the cutting structures may be provided by the cutting structures being of different cutting characteristics in different regions of the bit body, so as to achieve an asymmetrical cutting pattern.
  • cutting structures in some regions of the bit body may comprise polycrystalline diamond cutting elements designed to effect comparatively rapid cutting and penetration of the formation, while on other regions of the bit body the cutting structures are in the form of abrasive elements comprising studs which project from the bit body and have embedded in the exposed end thereof natural or synthetic diamonds.
  • the asymmetrical arrangement of the cutting elements may be provided by cutting elements in some regions of the bit body being disposed at different angular orientations with respect to their normal forward direction of movement during drilling than cutting elements in other regions of the bit body.
  • the invention is particularly applicable to drilling systems where the cutting structures comprise preform cutting elements formed, at least in part, from polycrystalline diamond.
  • the invention is also applicable to other forms of cutting elements.
  • the invention is applicable to roller cone bits.
  • the invention is also applicable to arrangements where the cutting structures are in the form of jets of high pressure fluid.
  • the modification of operation of the cutting structures may be achieved by increasing or reducing the fluid pressure in all the jets in synchronism with rotation of the bit.
  • the modification might also be achieved by pulsing the jet, or by varying a normal rate of pulsation.
  • FIG. 1 there is shown, down a borehole 10, a drilling system in which the bottom hole assembly 11 is connected to the lower end of a rotatable drill string, the first collar being indicated at 12.
  • the bottom hole assembly 11 comprises an asymmetrical drill bit 13 connected to a mud hammer 14 there being mounted above the mud hammer a surveying instrument package indicated diagrammatically at 15.
  • the drill bit 13 may be of any kind having a bit body carrying a plurality of cutting structures, where the cutting structures are asymmetrically distributed over the cutting face, or otherwise asymmetrically arranged, in accordance with the present invention.
  • the cutting structures comprise polycrystalline diamond preform cutting elements 16 mounted along substantially radially extending blades, one of which is shown at 17 in Figure 1.
  • the mud hammer 14 to which the bit 13 is connected is of known form and is so designed that as drilling mud is pumped through it at high pressure the mud hammer repeatedly applies axial hammer blows or impulses to the bit. Use of such a mud hammer will normally increase the rate of penetration of the bit.
  • the mud hammer may be of any suitable construction.
  • it may be of the kind in which the hammer blows are created by periodically restricting the flow of drilling fluid, or mud, through a passage in a part of the downhole assembly, for example a housing mounted in the drill string above the drill bit.
  • the periodic restriction creates a cyclical water-hammer effect.
  • the means for periodically interrupting the flow comprise a venturi body within which a flap valve is freely pivoted at its downstream end, the arrangement being such that, as drilling fluid flows downwardly through the housing, the flap valve vibrates so as alternately to open and close the venturi and thus create shock waves in the drilling fluid above the flap, the resulting impulses being transmitted to the drill bit.
  • the pivoted flap might be replaced by some other form of movable element responsive to the differential pressures acting on the element as a result of the venturi effect.
  • Alternative arrangements may be employed for periodically restricting the flow of the fluid, and those skilled in the art will also be aware of other forms of mud hammer which could be employed.
  • the present invention also includes within its scope the use of other devices, apart from mud hammers, for imparting impulses to the drill bit.
  • the drill bit may be coupled to a downhole actuator such as an hydraulic actuator.
  • impulses may be imparted to the bottom hole assembly by means of a percussion hammer or an axially oscillating mass carried in the bottom hole assembly.
  • the instrument package 15 includes sensors, such as magnetometers and/or accelerometers, for sensing the rotation and instantaneous rotational orientation of the drill bit and providing signals indicative of such instantaneous rotational orientation.
  • the instrument package 15 may also include other known forms of surveying equipment for enabling the position and direction of the borehole to be determined. Suitable forms of sensor are well known and may include accelerometers, magnetic fluxgates, gyroscopes, magnetic coils or pendulums. The specific details of the sensors and the instrumentation do not form part of the present invention and they will not therefore be described in detail.
  • Means are provided for selectively switching the mud hammer on and off periodically.
  • control means may be under the direct control of information from the sensing instruments.
  • the downhole instrument package 15 includes analogue and/or digital processing means for processing information concerning the position and direction of the borehole and passes instructions to the means controlling the mud hammer in accordance with a predetermined program.
  • operation of the mud hammer may be controlled from the drilling platform to control the direction of drilling in accordance with said information as to the position and direction of the borehole.
  • the sinusoidal curve 18 indicates the output from a magnetometer or other device for indicating the rotational orientation of the drill bit.
  • Each cycle 19 indicates a single complete revolution of the drill bit through 360° from a datum.
  • Superimposed is a graphical representation of the periods 20 when the mud hammer is operating. It will be seen that the mud hammer is switched on and off cyclically in phase relation to rotation of the drill bit.
  • FIG. 3 this is a view looking axially down a borehole with the cardinal points being indicated at N, E, S and W. If it is required, for example, to cause the borehole to be deviated to the south east, the control means for the mud hammer may be instructed to switch the hammer on and off in such phase relation to rotation of the drill bit that the hammer is switched on each time the cutter blade 17 reaches the position indicated at 21 in Figure 3, that is to say after the bit has rotated 45° from the datum position represented by north. The hammer remains switched on and operative while the drill bit rotates through 180° (clockwise in Figure 3) to the position indicated at 22 in Figure 3 and Figure 2 whereupon the hammer is switched off. This is repeated for each rotational cycle of the drill bit for as long as the deviation is required.
  • the mud hammer is shown in Figure 3 as being switched on through 180° of rotation of the drill bit, other pulse widths may be employed.
  • the pulse width may be pre-set and constant, or may be varied in accordance with signals delivered to the signal processor.
  • the mud hammer can be activated or de-activated in any portion of the rotation of the bit and the borehole thereby deviated in any required direction.
  • Figure 4 shows diagrammatically an arrangement for controlling a drilling system in accordance with the invention as described with reference to Figures 1-3.
  • the shaft 101 is driven relatively to the drill collar by a torquer 102 at such a rotational velocity in relation to the drill collar that it remains essentially stationary at an angular position dependent on the direction of the deviation required.
  • the sensors mounted on the stationary, or roll stabilised, component comprises a three-axis accelerometer 103, a three-axis magnetometer 104 and an angular accelerometer 105.
  • the accelerometer 103 outputs three signals G x , G y and G z indicative of mutually orthogonal components of the earth's gravitational field
  • the magnetometer 104 outputs three signals H x , H y and H z indicative of three mutually orthogonal components of the earth's magnetic field.
  • a processor 106 for example a digital processor which produces an output signal A indicative of the azimuth of the portion of the borehole in which the instrument package is located, a signal I indicative of the angle of inclination of the portion of the borehole, and a signal R indicative of the spatial roll angle (or tool face angle).
  • the desired azimuth A o and inclination I o for a given well depth are subtracted from the signals A, I respectively, indicative of the actual azimuth and inclination, to give signals (A - A o ) and (I - I o ) indicative of the changes in azimuth and inclination required to bring the borehole to the required direction.
  • the signals A o and I o may be preset, or derived from a predetermined program defining the required path of the borehole, or they may be signals passed downhole from an operator-controlled transmitter located at the surface.
  • the signals (A - A o ) and (I - I o ) are fed to a processor 107 which outputs a signal 108 indicative of the desired modulation phase angle of the mud hammer relative to the tool face angle. This is compared with the actual tool face angle R to produce a signal 109 indicative of the roll angle error of the sensor package. This signal passes through a filter 110 to attenuate noise and is fed to the torquer 102 to control the rotational position of the roll stabilised shaft 101.
  • the output from the roll stabilised system is provided by the rotational position (or shaft angle) of the shaft 101 itself and the shaft can therefore simply be mechanically connected to the modulation system for the mud hammer as indicated diagrammatically at 112.
  • the shaft 101 may be connected to a control valve for controlling the flow of drilling fluid through the mud hammer.
  • a control valve for controlling the flow of drilling fluid through the mud hammer.
  • power source or electromechanical devices may be required to modulate the mud hammer, thus simplifying the control system.
  • the pulse width of the modulation of the mud hammer may be preset and constant, but alternatively further control may be provided by allowing the pulse width to be varied.
  • the processor 107 may be arranged to produce a signal, as indicated at 113, indicative of the modulation pulse width and adapted to control the pulse width, i.e. the proportion of each rotation of the drill bit during which the mud hammer is in operation.
  • the signal 113 may be a control signal dependent on (A - A o ) and (I - I o ).
  • the control signal 113 is arranged to switch off the modulation of the mud hammer, for example by switching off the torquer 102.
  • the arrangement is such that the torquer is switched off in a position where the mud hammer is on, so that the mud hammer continues to operate, but is unmodulated.
  • the torquer is then switched on at periodic intervals, for example under the control of a clock, to allow the system to check whether the signals are still below the predetermined level or whether further correction of the direction of drilling is necessary.
  • the required phase relation between operation of the mud hammer and rotation of the drill bit may be selected by a trial and error method. That is to say, the mud hammer is first operated in an initial phase relation to rotation of the bit, the resultant deviation of the borehole is determined by the surveying instrumentation, and the phase relation is then adjusted through the angle necessary to bring the deviation to the required direction. Such feedback and adjustment may be handled by the digital processor.
  • the mud hammer is described as being cyclically switched on and off it may instead be continuously in operation, its intensity of operation being continuously varied cyclically to vary the rate of penetration of the cutting elements in synchronism with rotation of the drill bit.
  • any such variable may be periodically modified in synchronism with rotation of the drill bit to achieve a greater or lesser rate of penetration during only a portion of each revolution of the bit.
  • Figure 5 shows an arrangement where the rate of penetration of the cutting structures is varied cyclically by cyclically varying the weight-on-bit.
  • the bottom hole assembly includes, above the drill bit 30 an hydraulic actuator 31 of a kind generally similar to the type of assembly known as a "shock sub".
  • An actuator of this type normally comprises a piston and cylinder arrangement pressurised by the drilling mud to apply a downward load to the drill bit.
  • the normal purpose of the conventional shock sub is to absorb axial vibrations of the drill bit and prevent such vibrations being transmitted to the rest of the drill string.
  • the mud pressure applied to the hydraulic actuator contributes to the weight-on-bit, i.e. the axial load pressing the drill bit downwardly against the bottom of the borehole.
  • the downward load applied by the hydraulic actuator is cyclically varied in synchronism with rotation of the drill bit, and the drill bit is asymmetrically arranged, for example as previously described, so as to become displaced from the longitudinal axis of the existing borehole as drilling continues with cyclic operation of the hydraulic actuator.
  • a surveying instrument package 32 is included in the bottom hole assembly. It is shown above the hydraulic actuator 31 but might equally be below the hydraulic actuator.
  • drilling mud is delivered from a mud pit 33 by a mud pump 34 through a stand pipe 35 and hose 36 to the upper end of the kelly 37 through which the mud is delivered to the drill pipe.
  • the mud pumped down the drill string emerges through the hydraulic system of the drill bit 30 and passes back up the annulus between the drill string and the borehole to be returned to the mud pit 33 through a pipe 38, via a shale shaker, hydrocyclones etc., as indicated diagrammatically at 38 a .
  • a substantially constant mud pressure is applied to the hydraulic actuator 31 which in turn applies a downward load on to the drill bit.
  • the hydraulic pressure of the mud is cyclically varied in synchronism with rotation of the drill bit so that the hydraulic actuator 31 applies a cyclically varying downward load on the drill bit.
  • a bypass conduit 39 is connected between the standpipe 35 and the mud pit 33 and is controlled by a main valve 40.
  • a further valve 41 which is coupled to the rotary table 42, through a differential gearbox 43.
  • the connection may be of any suitable form, e.g. mechanical, electrical or hydraulic, and is such that the valve 41 opens and closes once for each revolution of the kelly 37.
  • the differential 43 enables the phase angle to be adjusted, i.e. enables the valve 41 to be opened and closed during any selected portion of each revolution of the kelly.
  • the valve 41 may be continuously cyclically operated but has no effect so long as the main valve 40 is closed. In this case the drilling assembly operates normally. When it is required to effect deviation of the drilling direction, the valve 40 is opened so that during a portion of each revolution of the drill bit the mud flow is bypassed directly to the mud pit 33. The resultant cyclical drop in hydraulic pressure is transmitted to the hydraulic actuator 31 so that the axial load applied by the actuator to the drill bit 30 also varies cyclically.
  • the pulses in the drilling mud at the drilling platform will be in phase relation to the rotation of the drill bit 30 and the actual phase angle will depend both on the wind-up in the drill string and on the time taken for each pulse to be transmitted down the borehole.
  • the necessary phase angle to achieve deviation of the borehole in a required direction may be determined from signals provided by the surveying instrument package 32 regarding the instantaneous rotational orientation of the drill bit, as in the previously described arrangement. Such information may therefore be used to control adjustment of the differential 43, to give the required direction of deviation of the drill bit.
  • the phase angle may be determined from a calculation of the wind up of the drill string and of the phase lag due to the transmission of the pulse to the hydraulic actuator.
  • the differential 43 for adjusting the phase angle may have an automatic input from the rotary table torque multiplied by a setting for the estimated effective drill string compliance.
  • the adjustment for phase lag will depend on the depth of the borehole and of the speed of sound in the drilling mud.
  • the required phase angle may be determined by the trial and error method previously described.
  • means may be provided to interrupt the link between the valve 41 and the rotary table 42 so that the valve 41 is only operated cyclically when a deviation in drilling direction is required.
  • Mud pulses originating at the surface will become substantially attenuated in the course of transmission down the borehole to the hydraulic actuator 31 and this must be allowed for in the design of the system.
  • Figure 1 shows diagrammatically a suitable form of drill bit where the surface generated by the profile of the cutting elements is generally convex so that the cutters face laterally outwardly as well as axially of the bit body.
  • the elements 16 are provided in a region which is offset to one side of a diametral axis of the cutting face.
  • Figure 6 shows a drill bit having a generally conical cutting face 25 where the cutting structures are similarly offset.
  • Figure 7 shows diagrammatically a drill bit, of a common "double cone” type, where the cutting structures are asymmetrically distributed to provide the effect of the present invention.
  • the profile of the bit body is in the form of two convex portions 27 and 28 on opposite sides of the central axis of the bit.
  • the cutting structures are asymmetrically distributed, partly over the radially outwardly facing surface of the left hand convex portion 27 and partly over the radially inwardly facing surface of the right hand convex portion 28.
  • inwardly and “outwardly” refer to the direction with respect to the central longitudinal axis of the drill bit).
  • the cutting structures are mounted on regions of such surfaces which face generally in the same lateral direction, i.e. to the left in Figure 7. Such arrangement ensures that the variation in rate of penetration of the two regions has a similar effect on the drill bit, i.e. causes it to become displaced in the same direction (to the left in Figure 7).
  • Figure 8 is a vertical section through a drill bit, shown downhole, of the double-cone type similar to that shown in Figure 7.
  • Figure 8 shows the drill bit in a part of the revolution thereof during which the rate of penetration is increased.
  • the cutting elements 50 are substantially all facing in the same lateral direction, i.e. to the left in Figure 8, so that the increased penetration will always occur on the left facing side of the bottom of the borehole, as indicated diagrammatically in dotted lines at 51 in Figure 8.
  • the bit will become increasingly displaced to the left of the central axis 52 of the existing borehole.
  • FIG 8A is a diagrammatic end view of the bit shown in Figure 8 and it will be seen that the end face of the bit comprises six blades 53, on which the cutting elements 50 are mounted, separated by waterways 54 leading to junk slots 55.
  • drilling mud is delivered to the waterways 54 through nozzles 56.
  • Wear pads 57 are provided on the gauge portion of the bit body and, as best seen in Figure 8, due to the asymmetry of the drill bit, wear pads 57 are only required on the portion of the gauge opposite to the direction in which the cutting elements face.
  • the wear pads 57 are shown on the cylindrical part of the gauge, but it may be preferable for the wear pads to be on the conical part of the bit face, as indicated at 58. In this case the wear pads 57 on the gauge portion may be omitted, as shown in the modified bit of Figures 9 and 9A.
  • the provision of asymmetrical wear pads, as shown, may serve to stabilise the bit in the borehole.
  • Figure 10 is a diagrammatic representation of the end view of the drill bit of Figures 8 and 8A, to show the asymmetrical distribution of the cutters.
  • the end face of the drill bit comprises three annular zones A, B and C.
  • the outer zone A faces radially outwardly away from the axis 52 of the drill bit.
  • the intermediate zone B faces generally axially of the drill bit and the inner zone c faces radially inwardly towards the axis 52.
  • Cutters are distributed generally symmetrically around the intermediate zone B since such cutters, facing axially, have little effect on the asymmetry of the drill bit.
  • cutters are mounted only on that portion of the outer zone A which is to the left of the diametral axis 59, and cutters are only mounted on that portion of the inner zone C which is to the right of the diametral axis 59. This has the result that all of the cutters in the zones A and C face in the same lateral direction with respect to the drill bit, that is to say to the left in Figure 10.
  • each cutting structure may include a cutting element of superhard material.
  • each cutting element may be in the form of a circular or part-circular tablet including a cutting table of superhard material, such as polycrystalline diamond or cubic boron nitride, bonded to a substrate of less hard material, such as cemented tungsten carbide.
  • the preform cutting element may be directly mounted on the bit body or may be bonded to a stud or other carrier, for example of cemented tungsten carbide, which is received in a socket in the bit body.
  • the bit body may be machined from metal, usually steel, or may be formed from an infiltrated tungsten carbide matrix by a powder metallurgy process.
  • the required asymmetry is provided by omitting cutting structures from some parts of the bit body.
  • some of the cutting structures may comprise so-called "impregs", which are studs of cemented tungsten carbide or other hard material which are mounted in sockets in the bit body and have embedded in their exposed outer ends natural diamonds or small elements of polycrystalline diamond.
  • impregs are studs of cemented tungsten carbide or other hard material which are mounted in sockets in the bit body and have embedded in their exposed outer ends natural diamonds or small elements of polycrystalline diamond.
  • the different cutting characteristics of the cutting structures in different regions of the bit body may be achieved by varying the angular orientation of the cutting faces of the cutting structures.
  • a polycrystalline diamond preform cutting element of the kind described above normally has a flat cutting face and this cutting face will be disposed at a negative back rake angle with respect to the normal forward direction of movement of the cutting element during drilling, and also a side rake angle.
  • the cutting effectiveness of such a preform cutting element will depend to a certain extent on its angular orientation, i.e.
  • the magnitude of the negative back rake angle and of the side rake angle, and the asymmetric arrangement of cutting characteristics required by the present invention may therefore be achieved by disposing preform cutters in different regions of the bit body so as to have different negative back rake angles and/or different side rake angles.
  • FIG. 11 there is shown an arrangement where a conventional drill bit 60, which may have cutting structures substantially symmetrically distributed about its own axis, is connected to the mud hammer or hydraulic actuator 61 by a bent sub assembly 62.
  • the angle of inclination of the drill bit 60 provided by the bent sub 62 is exaggerated in the drawing.
  • a bent sub is normally used in conjunction with a motor and the effect of the tilt of the drill bit is nullified during normal drilling by rotating the motor casing.
  • the tilt effect of the bent sub 62 is also normally nullified during drilling by the rotation of the drill string and hence of the bent sub with the drill bit.
  • the mud hammer is set in cyclical operation in synchronism with rotation of the drill bit this will have the effect, as previously explained, of increasing the rate of penetration during a portion of each revolution of the bit.
  • Such arrangement has the disadvantage, referred to earlier, that the tilted drill bit is unlikely to drill efficiently since it is not rotating about the axis about which it was designed to rotate.
  • the drill bit may be of virtually any type, symmetrical or unsymmetrical, and there may be advantage in being able to use a standard bit when steering.
  • any other suitable sensing method may be employed.
  • the instantaneous rotational orientation of the drill bit might be determined at the drilling platform from the instantaneous rotational orientation of the upper end of the drill string, and instructing signals sent to the mud hammer or other modifying device accordingly.
  • the hammer or other modifying device could be directly controlled by a mechanical rotational orientation sensing device, such as a pendulum, a series of pendulums or a gyroscope, rotatable with the drill bit and arranged to switch the device on and off automatically at predetermined points in each rotation of the drill bit.
  • a mechanical rotational orientation sensing device such as a pendulum, a series of pendulums or a gyroscope, rotatable with the drill bit and arranged to switch the device on and off automatically at predetermined points in each rotation of the drill bit.
  • the hammer or other modifying device be continuously controlled by signals from the drilling platform or from downhole computing means, the invention does not exclude arrangements where a control device for the modifying means requires to be preset for a particular required deviation of the hole, before the drilling system is introduced into the hole.
  • Figure 12 shows a further arrangement for controlling a mud hammer to vary the rate of penetration during only a portion of each revolution of the bit.
  • the bottom hole assembly includes an asymmetrical drill bit 70 connected to a mud hammer 71, there being mounted above the mud hammer a control module 72.
  • the drill bit 70 may be of any kind having a bit body carrying a plurality of cutting structures, where the bit structure is asymmetrically arranged in accordance with the present invention.
  • the mud hammer 71 to which the bit 70 is connected is also of any known form, and the particular construction of the mud hammer does not form part of the present invention.
  • this embodiment of the invention will be described in relation to the use of a mud hammer, it will be apparent that the system may be modified by replacing the mud hammer by an hydraulic actuator, or "shock sub", of the kind described in the embodiment of Figure 5.
  • Figure 12 depends on the provision of two synchronised clocks in the downhole assembly and at the surface respectively.
  • the downhole clock is indicated diagrammatically at 73
  • the control module 72 in the control module 72
  • the synchronised surface clock is indicated diagrammatically at 74.
  • Cyclical operation of the mud hammer 71 is arranged to be under the control of the downhole clock 73, as indicated diagrammatically by a control link 75. Since the surface clock 74 is synchronised to the downhole clock 73, it is also in synchronism with operation of the mud hammer and may therefore be used as a reference to permit adjustment of the phase angle between rotation of the bit 70 and the cyclical operation of the mud hammer. The means for achieving this will be described in relation to the block diagram included in Figure 12.
  • Signals from the surface clock 74 are fed to a signal processor 76 which also receives signals indicative of other parameters affecting the phase angle, as will be described.
  • the processor 76 may be a digital computer or an appropriate analogue device.
  • a rotation sensor 81 which supplies to the signal processor a signal 82 indicative of the rotation and rotational orientation of the rotary table 80.
  • This signal 82 is processed, together with the signal from the surface clock 74, to indicate the actual phase angle between the rotation of the rotary table 80 and the operation of the mud hammer 71, since the latter is generally in synchronism with the surface clock 74.
  • This actual phase angle is then compared by the signal processor 76 with a desired phase angle which is input to the signal processor, by an operator, as indicated diagrammatically at 83.
  • the input 83 will be in the form of a desired direction of deviation of the bore hole, since such deviation is dependent on the phase angle, as previously explained.
  • This comparison carried out by the processor 76 results in a phase error signal and a corresponding output signal 77 is sent to a speed controller 78 which, in response to such signal, controls the motor 79 driving the rotary table 80 in such manner as to reduce this phase error to zero and thereby achieve the desired phase angle.
  • the actual phase angle between the cyclical operation of the mud hammer and the rotation of the drill bit 70 will partly depend on the wind-up in the drill string. Accordingly, it is also necessary to supply the signal processor 76 with signals from which the wind-up can be determined and allowed for in determining the actual phase angle.
  • the wind-up of the drill string is dependent on the rotary table torque and on the angular compliance of the drill string.
  • a signal 84 which is indicative of the motor current, and hence of the rotary table torque.
  • the angular compliance of the drill string is dependent on the section and the length of the drill string and signals 85 and 86, indicative of these parameters respectively, are therefore also supplied to the signal processor 76.
  • the signal processor is arranged to process these signals in a manner to compensate for wind-up of the drill string in calculating the actual phase angle.
  • the clocks 73 and 74 will initially be in synchronism, it is possible that they will drift out of synchronisation during operation.
  • the downhole clock 73 is likely to be subject to elevated temperatures which may affect its time-keeping.
  • the clock 73 may be temperature controlled and a signal, indicated diagrammatically at 87, may be supplied to the signal processor 76 to provide an empirically determined correction for drift of the clocks out of synchronism due, for example, to temperature or other factors.
  • the arrangement of Figure 12 has the advantage, when compared for example with the arrangement of Figure 5, that adjustment of the phase angle does not depend on the transfer of data to the surface from downhole instrumentation.
  • Figure 13 illustrates a further embodiment of the invention in which the phase angle between the operation of the mud hammer and rotation of the drill bit is dependent on the rotational frequency of the bit, so that the phase angle, and hence the direction of deviation, may be adjusted to a required value simply by varying the speed of rotation of the bit.
  • the bottom hole assembly again includes an asymmetrical drill bit 90 connected to a mud hammer 91, there being mounted above the mud hammer a control module 92.
  • the drill bit 90 may be of any kind having a bit body carrying a plurality of cutting structures where bit structure is asymmetrically arranged in accordance with the present invention.
  • an hydraulic actuator, or "shock sub” may be employed instead of a mud hammer.
  • the control module 92 includes a sensor 93 of a kind which detects the rate of rotation of the drill bit and supplies to a signal processor 94 a signal, indicated at 95, indicative of the frequency of rotation.
  • the sensor 93 may be of any known kind which can provide a signal which fluctuates for each revolution of the drill bit, for example it may comprise an accelerometer and/or a magnetometer.
  • the signal processor controls the mud hammer 91 through a control link indicated diagrammatically at 96 in such manner as to control and vary the phase angle between cyclical operation of the mud hammer and rotation of the drill bit in accordance with the rate of rotation detected by the sensor 93.
  • the rate of rotation of the drill bit (averaged over a long enough period of time to cancel out the effect of any torsional oscillations of the drill string), is equal to the rate of rotation of the rotary table 97, which is controlled from the surface.
  • the rate of rotation of a drill bit is not normally particularly critical and may be varied by up to, say, 10 rpm without any significant effect on performance.
  • the signal processor 94 is arranged to adjust the phase angle between operation of the mud hammer and rotation of the drill bit in dependence on the rate of rotation, within a predetermined range.
  • the desired phase angle may be selected from the surface by increasing or decreasing the rate of rotation of the rotary table 97, and hence of the drill bit 90, by a predetermined amount. Since, as previously described, the direction of deviation of the asymmetrical drill bit is determined by such phase angle, the direction of deviation may be selected by selecting an appropriate rate of revolution of the rotary table 97, within a predetermined range.
  • Means may be provided to switch the mud hammer (or the modulation thereof) on or off in response to signals from the surface.
  • the signal processor 94 may be adapted to switch the mud hammer (or its modulation) on and off in response to a predetermined sequence of operations detectable by the sensor 93.
  • the signal processor 94 may be of any suitable kind for controlling the phase angle of the mud hammer in response to variation in rotational frequency as detected by the sensor 93.
  • it could include a frequency meter which compares with a clock the frequency of signals from the sensor 93 and delivers a corresponding adjusting signal to a time lag device which controls the phase angle between the operation of the mud hammer and rotation of the drill bit, in response to signals from the rotation sensor 93.
  • the signal processor may incorporate a resonant component, for example electronic or mechanical, which is tuned to a frequency close to that of the datum frequency of rotation of the drill bit whereby the phase angle varies steeply in response to deviations from that datum frequency.
  • a resonant component for example electronic or mechanical, which is tuned to a frequency close to that of the datum frequency of rotation of the drill bit whereby the phase angle varies steeply in response to deviations from that datum frequency.
  • the arrangement of Figure 13 has the advantage that, since the phase angle is dependent solely on the frequency of rotation of the drill bit, no allowance requires to be made for a wind-up in the drill string, and it provides a convenient way of transmitting signals from the surface to the downhole assembly.

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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)
EP19910306436 1990-07-17 1991-07-16 Earth drilling system and method for controlling the direction of a borehole Withdrawn EP0467642A3 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB909015704A GB9015704D0 (en) 1990-07-17 1990-07-17 A drilling system and method for controlling the direction of holes being drilled or cored in subsurface formations
GB9015704 1990-07-17
GB919100874A GB9100874D0 (en) 1991-01-15 1991-01-15 A drilling system and method for controlling the direction of holes being drilled or cored in subsurface formations
GB9100874 1991-01-15

Publications (2)

Publication Number Publication Date
EP0467642A2 true EP0467642A2 (de) 1992-01-22
EP0467642A3 EP0467642A3 (en) 1993-03-10

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EP19910306436 Withdrawn EP0467642A3 (en) 1990-07-17 1991-07-16 Earth drilling system and method for controlling the direction of a borehole

Country Status (5)

Country Link
EP (1) EP0467642A3 (de)
AU (1) AU8044091A (de)
CA (1) CA2047316A1 (de)
GB (1) GB2246151A (de)
NO (1) NO912794L (de)

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EP0686752A1 (de) * 1994-06-07 1995-12-13 Anadrill International SA Verfahren und Vorrichtung zum Richtungsbohren
WO1997033065A1 (en) * 1996-03-04 1997-09-12 Vermeer Manufacturing Company Directional boring
US6357537B1 (en) 2000-03-15 2002-03-19 Vermeer Manufacturing Company Directional drilling machine and method of directional drilling
WO2001066900A3 (en) * 2000-03-03 2002-05-23 Vermeer Mfg Co Method and apparatus for directional boring under mixed conditions
US6454025B1 (en) 1999-03-03 2002-09-24 Vermeer Manufacturing Company Apparatus for directional boring under mixed conditions
US6491115B2 (en) 2000-03-15 2002-12-10 Vermeer Manufacturing Company Directional drilling machine and method of directional drilling
EP1627985A1 (de) * 2004-08-18 2006-02-22 ReedHycalog UK Limited Drehbohrmeissel
US20110155467A1 (en) * 2009-12-28 2011-06-30 Halliburton Energy Services, Inc. Timed impact drill bit steering
WO2011081621A1 (en) * 2009-12-28 2011-07-07 Halliburton Energy Services, Inc. Timed impact drill bit steering
US8196677B2 (en) 2009-08-04 2012-06-12 Pioneer One, Inc. Horizontal drilling system
DE202011109928U1 (de) 2011-02-24 2012-07-12 Igor D. Shaposhnikov Kegelbohrstange
US9206649B1 (en) 2014-06-24 2015-12-08 Pine Tree Gas, Llc Systems and methods for drilling wellbores having a short radius of curvature
US9453410B2 (en) 2013-06-21 2016-09-27 Evolution Engineering Inc. Mud hammer
EP3091171A1 (de) * 2015-01-27 2016-11-09 Nabors Lux Finance 2 S.a.r.l. Verfahren und vorrichtung zur ausrichtung eines bohrlochwerkzeugs
US9617791B2 (en) 2013-03-14 2017-04-11 Smith International, Inc. Sidetracking system and related methods
US10472955B2 (en) 2015-01-27 2019-11-12 Nabors Lux 2 Sarl Method of providing continuous survey data while drilling

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US5553678A (en) * 1991-08-30 1996-09-10 Camco International Inc. Modulated bias units for steerable rotary drilling systems
GB2282614A (en) * 1993-10-05 1995-04-12 Anadrill Int Sa Bottom hole assembly for directional drilling
GB2284837B (en) * 1993-12-17 1997-11-12 Anadrill Int Sa Directional drilling method and apparatus
US5617926A (en) * 1994-08-05 1997-04-08 Schlumberger Technology Corporation Steerable drilling tool and system
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US5727641A (en) * 1994-11-01 1998-03-17 Schlumberger Technology Corporation Articulated directional drilling motor assembly
US5542482A (en) * 1994-11-01 1996-08-06 Schlumberger Technology Corporation Articulated directional drilling motor assembly
US5520256A (en) * 1994-11-01 1996-05-28 Schlumberger Technology Corporation Articulated directional drilling motor assembly
GB9517378D0 (en) * 1995-08-24 1995-10-25 Sofitech Nv Hydraulic jetting system
US5937958A (en) * 1997-02-19 1999-08-17 Smith International, Inc. Drill bits with predictable walk tendencies
US6607044B1 (en) 1997-10-27 2003-08-19 Halliburton Energy Services, Inc. Three dimensional steerable system and method for steering bit to drill borehole
US6092610A (en) * 1998-02-05 2000-07-25 Schlumberger Technology Corporation Actively controlled rotary steerable system and method for drilling wells
US6158529A (en) 1998-12-11 2000-12-12 Schlumberger Technology Corporation Rotary steerable well drilling system utilizing sliding sleeve
US6109372A (en) * 1999-03-15 2000-08-29 Schlumberger Technology Corporation Rotary steerable well drilling system utilizing hydraulic servo-loop
WO2001034935A1 (en) 1999-11-10 2001-05-17 Schlumberger Holdings Limited Control method for use with a steerable drilling system
GB2398091B (en) * 2001-05-14 2005-06-29 Baker Hughes Inc Method and apparatus for monitoring and recording of the operating condition of a downhole drill bit during drilling operations
WO2003031763A1 (en) * 2001-10-03 2003-04-17 Shell Internationale Research Maatschappij B.V. System for rotary-percussion drilling in an earth formation
US6585061B2 (en) * 2001-10-15 2003-07-01 Precision Drilling Technology Services Group, Inc. Calculating directional drilling tool face offsets
AU2009340368B2 (en) * 2009-02-19 2015-04-09 Commonwealth Scientific And Industrial Research Organisation Drilling method and assembly

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EP0686752A1 (de) * 1994-06-07 1995-12-13 Anadrill International SA Verfahren und Vorrichtung zum Richtungsbohren
WO1997033065A1 (en) * 1996-03-04 1997-09-12 Vermeer Manufacturing Company Directional boring
US5778991A (en) * 1996-03-04 1998-07-14 Vermeer Manufacturing Company Directional boring
CN1080361C (zh) * 1996-03-04 2002-03-06 弗米尔制造公司 控制钻孔设备钻透介质形成钻孔的方法和设备
US6454025B1 (en) 1999-03-03 2002-09-24 Vermeer Manufacturing Company Apparatus for directional boring under mixed conditions
USRE44427E1 (en) 1999-03-03 2013-08-13 Vermeer Manufacturing Company Apparatus for directional boring under mixed conditions
US6588516B2 (en) 1999-03-03 2003-07-08 Vermeer Manufacturing Company Method and apparatus for directional boring under mixed conditions
WO2001066900A3 (en) * 2000-03-03 2002-05-23 Vermeer Mfg Co Method and apparatus for directional boring under mixed conditions
US6491115B2 (en) 2000-03-15 2002-12-10 Vermeer Manufacturing Company Directional drilling machine and method of directional drilling
US6357537B1 (en) 2000-03-15 2002-03-19 Vermeer Manufacturing Company Directional drilling machine and method of directional drilling
EP1627985A1 (de) * 2004-08-18 2006-02-22 ReedHycalog UK Limited Drehbohrmeissel
US7318492B2 (en) 2004-08-18 2008-01-15 Reedhycalog Uk Ltd Rotary drill bit
US8746370B2 (en) 2009-08-04 2014-06-10 Pioneer One, Inc. Horizontal drilling system
US8196677B2 (en) 2009-08-04 2012-06-12 Pioneer One, Inc. Horizontal drilling system
WO2011081621A1 (en) * 2009-12-28 2011-07-07 Halliburton Energy Services, Inc. Timed impact drill bit steering
US20110155467A1 (en) * 2009-12-28 2011-06-30 Halliburton Energy Services, Inc. Timed impact drill bit steering
US9562394B2 (en) 2009-12-28 2017-02-07 Halliburton Energy Services, Inc. Timed impact drill bit steering
DE102011012362A1 (de) * 2011-02-24 2012-08-30 Igor D. Shaposhnikov Kegelbohrstange
DE202011109928U1 (de) 2011-02-24 2012-07-12 Igor D. Shaposhnikov Kegelbohrstange
US9617791B2 (en) 2013-03-14 2017-04-11 Smith International, Inc. Sidetracking system and related methods
US9453410B2 (en) 2013-06-21 2016-09-27 Evolution Engineering Inc. Mud hammer
US9206649B1 (en) 2014-06-24 2015-12-08 Pine Tree Gas, Llc Systems and methods for drilling wellbores having a short radius of curvature
WO2015200390A1 (en) * 2014-06-24 2015-12-30 Pine Tree Gas, Llc Systems and methods for drilling wellbores having a short radius of curvature
US10161189B2 (en) 2014-06-24 2018-12-25 Pine Tree Gas, Llc Systems and methods for drilling wellbores having a short radius of curvature
EP3091171A1 (de) * 2015-01-27 2016-11-09 Nabors Lux Finance 2 S.a.r.l. Verfahren und vorrichtung zur ausrichtung eines bohrlochwerkzeugs
US9951562B2 (en) 2015-01-27 2018-04-24 Nabors Lux 2 Method and apparatus for orienting a downhole tool
US10472955B2 (en) 2015-01-27 2019-11-12 Nabors Lux 2 Sarl Method of providing continuous survey data while drilling

Also Published As

Publication number Publication date
NO912794D0 (no) 1991-07-17
NO912794L (no) 1992-01-20
EP0467642A3 (en) 1993-03-10
GB2246151A (en) 1992-01-22
AU8044091A (en) 1992-01-23
GB9115488D0 (en) 1991-09-04
CA2047316A1 (en) 1992-01-18

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