Field of the invention

The present invention relates to methods and apparatus for drilling.

The invention has been devised particularly, although not necessarily solely, in relation to a directional drilling tool.

Background Art

The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge in Australia or elsewhere as at the priority date of the application.

Current directional drilling apparatus include drilling assemblies that have a fixed tool face. A fixed tool face drilling assembly is an assembly wherein the direction at which the drill bit is pointing cannot be changed. The fact that the drilling assembly has a fixed tool face implies that the drill bit must be orientated towards the desired drilling direction in order for the drilling to occur towards the desired drilling direction. Typically, orientation of the drilling apparatus for changing the direction of drilling is conducted by reorienting the drilling apparatus by personnel located at the surface. Conducting the orientation of the drilling assembly from the surface is typically a time consuming exercise.

Further, directing a drill bit to a particular direction for drilling of for example along a curved path typically is conducted via pressure pads. The pressure pads apply pressure to a specific location of the borehole wall that is being drilled by the drilling apparatus incorporating the pressure pads.

Several options for activating the pressure pads have been developed. For example, the pressure pads may be activated through the drilling fluids used during drilling of the borehole. In this case, the drilling apparatus comprise means for activating the pressure pads which are responsive to the pressure of the drilling fluid. The means for activating the pressure pads may be activated from the surface by controlling the pressure of the drilling fluid.

Systems based on drilling fluids for activating the pressure pads require a relatively great number of conduits and valves in order to transfer the drilling fluids to the pressure pads as well as to control the drilling fluid pressure for activation of the pressure pads. This increases the costs for developing the directional drilling tools. Also, because of the relatively large number of conduits and valves required to activate the pressure pads, these systems for activating the pressure pads require considerable maintenance and control in order to operate properly.

The current use of drilling fluid based systems has depth limitations related to the increase in hydrostatic pressure incurred as the bore progresses deeper or through pressurised geological formation.

It is against this background that the present invention has been developed. Summary of the Invention

According to a first arrangement of a first aspect of the invention there is provided a pad assembly for mounting on a drill barrel having a drill bit to which a force is applied for drilling of a borehole, the pad assembly comprising at least one pad, means for expanding the at least one pad, and means for receiving the force applied to the drill barrel for activating the means for expanding the at least one pad. Preferably, the means for receiving the force comprises a proximal ring member slideably mounted on the drill barrel having the at least one pad attached thereto.

Preferably, the means for expanding the at least one pad comprises a distal ring member adapted to apply a force to the at least one pad for expansion thereof.

Preferably, the distal ring member comprises a body for applying a force to the at least one pad for expansion thereof. Preferably, the distal ring member is slideably mounted on the drill barrel for displacement towards the second ring member for expansion of the at least one pad.

Preferably, the at least one pad is pivotally attached to the distal ring member. Preferably, the body for applying a force to the at least one pad comprises a wedged body having a slanted face on which the at least one pad slides.

Preferably, the at last one pad is biased towards a contracted condition.

Preferably, the at least one pad comprises a distal end having a wheel attached thereto, the wheel being adapted to rotate against the borehole. Preferably, the body for applying a force to the at least one pad comprises a slot extending longitudinally along the slanted surface of the body, the slot being adapted to receive the wheel.

Preferably, the means for expanding the at least one pad comprises at least one wedged body.

Preferably, the pad assembly further comprises a plurality of pads and a plurality of wedged bodies, for each pad there is a counterpart wedged body to allow simultaneous expansion of. the pads. In this particular arrangement, the plurality of pads when in the expanded condition prevent rotation of the outer drilling Alternatively, the pad assembly further comprises a plurality of pads, the pads being adapted to be expanded independently from each other. In this particular arrangement, the pad assembly is adapted to guide the drill bit towards a desired direction.

Preferably, at least one pad of the plurality of pads is expanded by presenting the at least one pad to at least one respective wedged body. Preferably, the distal ring member is adapted to rotate around drill barrel to allow the at least one wedged body to be presented to the at least one pad.

In a second arrangement of the first aspect of the invention, the means for receiving the force which is applied to the drill barrel comprises an inner cylinder slideably mounted on the drill barrel, the inner cylinder having the means for expanding the at least one pad.

Preferably, the means for expanding the at least one pad comprises at least one wedge section having a slanted face on which the at least one pad slides.

Preferably, the pad assembly further comprising an outer cylinder adapted to receive the inner cylinder for expansion of the at least one pad.

Preferably, the outer cylinder comprises along the circumference of the outer cylinder at least one opening incorporating the at least one pad, the pad hingedly attached within the opening.

Preferably, the pad assembly further comprising spring means adapted to join the inner and outer cylinders.

Preferably, the spring means are adapted to keep the inner cylinder out of the outer cylinder unless a force is applied to the drill barrel.

Preferably, the spring means comprise an helical spring having an end attached to the outer cylinder and an opposite end attached to the inner cylinder at a location such that the inner cylinder is surrounded by the helical ring.

Preferably, the outer cylinder comprises a plurality of pads arranged along the circumference of the outer cylinder.

Preferably, the inner cylinder comprises a plurality of wedged sections arranged along the circumference of the inner cylinder, the wedged section being adapted to expand simultaneously the plurality of pads as the inner cylinder is received by the outer cylinder. In this particular arrangement, the plurality of pads when in the expanded condition prevent rotation of the outer drilling

Alternatively, the inner cylinder comprises at least one wedged section located at a specific angular section of the inner cylinder, the wedged section being adapted to rotate so as to be presented to at least one pad for expansion of the at least one pad as the inner cylinder is received by the outer cylinder. In this particular arrangement, the pad assembly is adapted to guide the drill bit towards a desired direction.

According to a second aspect of the invention there is provided a steering unit for mounting on a drill barrel having a drill bit onto which a force is applied for drilling of a borehole, the steering unit comprising a pad assembly comprising at least one pad, means for expanding the at least one pad, and means for receiving the force applied to the drill barrel for activating the means for expanding the at least one pad.

Preferably, the steering unit further comprises orientation means for determining orientation of the pad assembly.

Preferably, the steering unit comprises at least on pad assembly according to the first arrangement of the first aspect of the invention. Preferably, the steering unit further comprises means for rotating the distal ring member of the pad assembly in order to present the at least one wedged body to the pad to be expanded for applying pressure to the borehole wall.

Preferably, the steering unit further comprises an outer barrel rotatably mounted on the drill barrel. Preferably, the drill barrel comprises the orientation means. Preferably, the steering unit comprises at least on pad assembly according to the second arrangement of the first aspect of the invention.

Preferably, the pad assembly further comprises a double shear pin system for controlling, activation of the pad assembly. Preferably, the steering unit further comprises a pad activation system comprising an inner cylinder and an distal outer cylinder, the distal outer cylinder being slideably mounted on the inner cylinder, the outer cylinder being adapted to be selectively displaced between a contracted condition and an extended condition by sliding the outer cylinder to a distal end of the inner cylinder and locking the outer cylinder at the distal end of the inner cylinder for activation of the pad assembly.

Preferably, the steering unit further comprises means for rotating the outer distal cylinder.

Preferably, the activation system further comprises an outer proximal cylinder being adapted to push the outer distal cylinder to the distal end of the inner cylinder for locking of the outer distal cylinder at the distal end of the inner cylinder for activation of the pad assembly and for unlocking of the outer distal cylinder to deactivate the pad assembly.

Preferably, the outer distal and the outer proximal cylinder comprises extending outwardly from the inner surface each at least one protrusion and the inner cylinder comprises at least one channel adapted to receive the at least one protrusions of each of the outer distal and outer proximal cylinder.

Preferably, the inner cylinder comprises a plurality of protrusions defining the at least one channel, the plurality of protrusions extending axially along the inner cylinder from the proximal to the distal end of the inner cylinder.

Preferably, at least one of the plurality of protrusions of the inner cylinder is adapted to receive the proximal end of the at least one protrusion of the outer distal cylinder while the distal outer cylinder is in extended condition for locking of the outer cylinder in extended condition.

Preferably, the outer distal cylinder is adapted to rotate in the extended condition to allow engagement of the proximal end of the at least one protrusion of the outer distal cylinder with the distal end of the at least one of the plurality of protrusions of the inner cylinder for locking of the outer cylinder in extended condition.

Preferably, the pad activation system is actuated by the force applied to the drill barrel.

In an arrangement, spring means are provided to assist the pads to actuate.

According to a third aspect of the invention there is provided an apparatus for drilling a bore comprising a drill string; a drill barrel having a drill bit, the drill barrel being attached to the drill string for receiving a force applied to the drill string for drilling the bore; a pad assembly mounted on the drill barrel, the pad assembly comprising at least one pad, means for expanding the at least one pad, and means for receiving the force applied to the drill barrel for activating the means for expanding the at least one pad.

Preferably, the apparatus for drilling comprises at least on pad assembly according to the first arrangement of the first aspect of the invention.

Preferably, the apparatus comprises a first pad assembly comprising a plurality of pads being adapted to simultaneously expand; and a second pad assembly comprising a plurality of pads, the pads being adapted to be expanded independently from each other. In this particular arrangement, the first pad assembly comprises locking pad assembly to prevent rotation of the outer barrel and the second pad assembly comprises a steering pad assembly adapted to guide the drill bit towards a desired direction.

Preferably, the drill string comprises a tube assembly having a distal end adapted to receive the drill barrel. Preferably, the tube assembly comprises means for applying the force to the drill barrel for drilling of the borehole.

Preferably, the means for applying the force comprises an inner flange extending radially from the inner surface of the tube assembly of the drill string for applying the force onto the drill barrel.

Preferably, the inner flange is spaced apart from the distal end of the tube assembly.

Preferably, the drill string comprises means for applying a force to the pad assembly. Preferably, the means for applying a force comprise a outer flange extending radially outward from the outer surface of the drill string for applying the force on the pad assembly for expansion of the at least one pad.

In an alternative arrangement, the apparatus for drilling comprises at least on pad assembly according to the second arrangement of the first aspect of the invention. Preferably, the apparatus comprises a first pad assembly comprising a plurality of pads being adapted to simultaneously expand; and a second pad assembly comprising a plurality of pads, the pads being adapted to be expanded independently from each other. In this particular arrangement, the first pad assembly comprises locking pad assembly to prevent rotation of the outer barrel and the second pad assembly comprises a steering pad assembly adapted to guide the drill bit towards a desired direction.

Preferably, the activation system is actuated by the force applied to the drill barrel.

According to a fourth aspect of the invention there is a pad comprising a body having an indentation and at least one wheel rotatably attached within the indentation. Preferably, the pad comprises a joint for hingedly attaching the body of the pad allowing the pad to pivot during application of a force to the pad.

Preferably, the at least one wheel comprises at least one teethed ring.

According to a fifth aspect of the invention there is provided a pad assembly for mounting on a drill barrel, the pad assembly comprising a plurality of pads arranged around the drill barrel and means for selective displacing at least one pad of the plurality of pads between an expanded condition and a contracted condition, wherein the pads are adapted to be selectively displaced between the expanded condition and the contracted condition independently from each other. Preferably, the means for selective displacing at least one pad comprises a body for applying a force to the at least one pad for displacing the at least one pad to the expanded condition.

Preferably, the body for applying a force comprises at least one wedged section slideably mounted on the drill barrel, the wedged section comprising a slanted face adapted to receive the at least one pad for expansion of the at least one pad.

Preferably, the wedged section is rotatably mounted on the drill barrel to allow rotating of the wedged section in order for the wedged section to be presented to the at least one pad, wherein the at least one pad is displaced in the expanded condition by sliding the wedged section towards the at least one pad to allow the pad to slide over the slanted face for expansion of the at least one pad.

According to a sixth aspect of the invention there is provided a steering unit for mounting on a drill barrel having a drill bit, the steering unit comprising a pad assembly in accordance with the fifth aspect of the invention.

Preferably, the steering unit further comprises orientation means for determining orientation of the pad assembly. According to a seventh aspect of the invention there is provided an apparatus for drilling a bore comprising a steering unit in accordance with the sixth aspect of the invention.

According to an eighth aspect of the invention there is provided a method of drilling a borehole comprising using a drilling apparatus according to the third or seventh aspect of the invention.

Brief Description of the Drawings

The present invention will be better understood by reference to the following description of specific embodiments thereof as shown in the accompanying drawings, in which:

Figure 1 is a perspective view of an apparatus for drilling according to a first embodiment of the invention.

Figure 2 is a perspective view of a steering pad assembly in contracted condition mounted on the apparatus for drilling shown in figure 1. Figure 3 is a perspective view of the steering pad assembly in expanded condition mounted on the apparatus for drilling shown in figure 1.

Figure 4 is a perspective view of a locking pad assembly in contracted condition mounted on the apparatus for drilling shown in figure 1.

Figure 5 is a perspective view of the locking pad assembly in contracted condition.

Figure 6 is a perspective view of the locking pad assembly in extended condition.

Figure 7 is a sectional view of the apparatus for drilling shown in figure 1. Figure 8 is a sectional view of an outer barrel mounted on the apparatus for drilling shown in figure 1.

Figure 9 is a perspective sectional view of means for applying force on the locking and steering unit mounted on the apparatus for drilling shown in figure 1.

Figure 10 is a perspective sectional view of the means for applying force on the locking and steering unit.

Figure is a perspective view of an apparatus for drilling according to a second embodiment of the invention.

Figure 12 is a perspective view of the drilling bit and a steering pad assembly in contracted condition mounted on the apparatus for drilling shown in figure 11.

Figure 13 is a perspective view of the steering pad assembly in contracted condition mounted on the apparatus for drilling shown in figure 11.

Figure 14 is a perspective view of a locking pad assembly in contracted condition mounted on the apparatus for drilling shown in figure 11.

Figure 15 is a perspective view of a pressure pad assembly included in the locking and steering pad assembly mounted on the apparatus for drilling shown in figure 11.

Figures 16 to 22 shows the apparatus for drilling shown in figure 11 during the process for activating and deactivating the pad assembly.

Figure 23 is a perspective view of a alternative arrangement of the steering pad assembly in accordance with the second embodiment of the invention. Figure 24 is a schematic view of an apparatus for drilling according to a second embodiment of the invention showing the driving unit for activation of the steering assembly.

Detailed Description of Specific Embodiment(s) Figure 1 shows an apparatus for drilling 10 in accordance to a first embodiment of the invention. The apparatus for drilling 10 comprises a drill string 12 and a drill barrel 14. A drill bit 16 is attached to the drill barrel 14. The drill barrel 14 is connected to the drill string 12 such that a force applied to the drill string is transferred to the drill bit 16 for drilling of the borehole (see figure 10).

The apparatus for drilling 10 may be used for drilling of boreholes including directional drilling of boreholes.

The apparatus for drilling 10 may also be used during core drilling operations. For core drilling operations the drill barrel comprises outer and inner tube assemblies. A cutting head is attached to the outer assembly defining the drill bit. During the drilling operation, a core is generated which progressively extends along the inner tube assembly. The apparatus for drilling 10 further comprises a locking and steering unit 20. The locking and steering unit 20 comprises a locking pad assembly 22, a steering pad assembly 24 and an outer barrel 26. The locking and steering pad assemblies 22 and 24, and the outer barrel 26 are mounted on the drill barrel 14 between the drill bit 16 and the distal end of the drill string 12.

Each of the locking and steering pad assemblies 22 and 24 comprises pads 30 adapted to be expanded from a contracted condition to an expanded condition. In the expanded condition, the pads 30 acts as pressure pads 30 which apply pressure to the walls of the borehole that is being drilled. The pressure pads 30 of the locking pad assembly 22 apply pressure to the borehole wall to stop rotation of the locking and steering unit 20 and the outer barrel 26. The pads 30 of the steering pad assembly 24 apply pressure at specific locations of the borehole wall for guiding the drill bit 16 towards a desired direction.

Bearing housings 32 are mounted on the drill barrel 14 at each end of the locking and steering unit 20. The bearing housings 32 allow the locking and steering unit 20 to rotate independently with respect to the drill barrel 14.

Further, the apparatus for drilling 10 also comprises means for activating the locking and steering unit 20 (see figures 9 and 10). The locking and steering unit 20 may be activated and/or operated by transferring the force that is being applied to the drill bit 16 for drilling of the borehole. For this, the apparatus for drilling 10 comprises means for transferring the force of the drill string 12 towards the locking and steering unit 20. Figures 2 to 4 shows the steering pad assembly 24. As said before, the steering pad assembly 24 guides the drill bit 16 to a desired direction during directional drilling.

The steering pad assembly 24 comprises distal and proximal ring members 42 and 44 located opposite to each other. The proximal ring member 44 is slideably mounted on the drill string 12. The distal ring member 42 is attached to the outer barrel 26. This allows the distal and proximal ring members 42 and 44 to be drawn together or to be separated from each other as the proximal ring member 44 slide longitudinally along the. drill barrel 14.

Pressure pads 30 are attached to the proximal ring member 44. The pressure pads 30 include an end attached to the proximal ring member 44. The opposite end of the pressure pad 30 comprises a wheel 50. The wheel 50 is rotatably mounted on the pressure pad 30. The wheel 50 facilitates sliding of the pad 30 along the wall of the borehole during drilling of the borehole.

The pressure pads 30 are attached along the circumference of the proximal ring member 42 and spaced apart with respect to each other. The pressure pads 30 are pivotically attached to the proximal ring member 44 such that each pressure pad 30 can pivot between a contracted condition and an expanded condition.

The pressure pads 30 are biased towards the contracted position. For this, spring sheets 52 are attached to the ring member and each of the pressure pads 30.

A plurality of wedged bodies 56 are attached to the distal ring member 42 of the steering pad assembly 24. The wedged bodies 56 are attached along the circumference of the ring member at spaced apart locations with respect to each other. The wedged bodies 56 comprise a slanted surface 60. The wedged bodies 56 are supported on the distal ring member 42 such that the slanted surface 60 faces outward opposite to the drill barrel 14. The lowest portion 62 of the slanted surface 60 is presented to the pressure pads 30. The highest portion 64 of the slanted surface 60 is attached to the distal ring member. In this way, the pressure pads 30 can slide over the slanted surface 60 and are progressively expanded as the pressure pads 30 slide over the slanted surface 60. The slanted surface 60 comprises at the highest portion 64 a resting area 66 for receiving the wheel 50 of the pressure pad 30. Slots 70 extend longitudinally along the slanted surface 60 of each of the wedged bodies 56. The slots 70 are adapted to receive the wheel 50 of the pressure pad 30 assembly as the pressure pad 30 assembly slides over the slanted surface 60. In this way, the wheel 50 of each pressure pad 30 does not rotate as the pressure pads 30 slide over the slanted surface 60. Instead, the wheels 50 are free to rotate against the borehole wall as the drilling apparatus 10 moves along the borehole.

The steering pad assembly 24 expands as the proximal and the distal ring members 42 and 44 come together. As the ring members 42 and 44 approach each other, the pressure pads 30 slide over the slanted surfaces 60 of the wedged members. This allows displacing the pressure pads 30 from the contracted condition to the expanded condition. ln the arrangement shown in figure 2, there are three wedged bodies 56. Each of the wedged bodies 56 will expand three pressure pads 30 which are located opposite to the three wedged bodies 56. The remaining pressure pads 30 are maintained in the contracted condition. In this manner, only the three pressure pads 30 will apply pressure to the borehole wall.

As will be described with reference to the method of operation of the drilling apparatus 10, the fact that only a group of pressure pads 30 apply pressure to the borehole wall allows guiding the drilling operation towards a desired direction.

It is possible to select which group of pressure pads 30 will be expanded. This is accomplished by rotating the distal ring member 42 around the drill barrel 14. Rotating the distal ring member 42 presents the wedged bodies 56 to the pressure pads 30 to be expanded. As said before, the pressure pads 30 are expanded bringing the distal and proximal ring members 42 and 44 together.

The second ring member is rotated through a driving unit located in the outer barrel 26. The driving unit comprises a motor 34 having a shaft drivingly engaged to the distal ring member 42. This allows locating the wedge bodies 56 opposite to the pressure pads 30 to be expanded.

The fact that it is possible to select the pads 30 that will be displaced is particularly advantageous because it permits directing the drill bit 16 to a desired direction. The drill bit 16 can be directed to specific direction by presenting the three wedged bodies 56 to the three pressure pads 30 which when expanded will guide the drilling operation to the desired location.

Figures 4 to 6 show the locking pad assembly 22. The locking pad assembly 22 is similar to the steering pad assembly 24 and similar reference numerals are used to identify similar parts.

The locking pad assembly 22 comprises a proximal ring member 44 having pressure pads 30 attached thereto. A distal ring member 42 comprises slanted rails 102. The slanted rails 102 are adapted to receive the pressure pads 30 as the distal and proximal ring members 42 and 44 approach each other. As explained with reference to the steering pad assembly 24, sliding of the pad 30 members on the slanted rails 102 allows expansion of the pressure pads 30 in order that a pressure be applied to the borehole wall via the pressure pads 30.

Referring to figure 5, the locking pad assembly 22 comprises for each pressure pad 30 a counterpart slanted rail 102. This allows expanding all of the pressure pads 30 of the locking pad assembly 22. In this manner, the entire circumference of the borehole wall is being contacted by the pressure pads 30. This facilitates stopping and maintaining the locking and steering unit 20 at a specific location around the drill barrel 14.

Slots 70 extend longitudinally along the slanted rails 102. The slots 70 are adapted to receive the wheel 50 of the pressure pads 30 as the pressure pads 30 slide over the slanted rails 102. In this way, the wheel 50 of each pressure pad 30 is free to rotate against the borehole wall as the pressure pads 30 slide over the slanted rails 102. As mentioned before, the pad assemblies 22 and 24 may be activated and operated by applying a force to the locking and steering unit 20. In particular, the force is the force that is being applied to the drill string 12 for drilling of the borehole. The drill string 12 comprises means 103 for applying the force to the drill barrel 14 (see figure 10). The means 103 for applying the force to the drill barrel 14 comprises an inner flange 104 extending radially from the inner surface of the drill string 12. In this way, the force is applied onto the drill barrel 14 while the drill barrel 14 is attached to the drill string 12.

The inner flange 104 is spaced apart from the distal end of the drill string 12. This allows the drill barrel 12 to slide longitudinally along the drill string 12 as the drill barrel 14 enters the drill string 12 (see figure 10). The drill string 12 also comprises means 106 for applying the force to the locking and steering unit 20. The means 106 for applying the force to the locking and steering unit 20 comprise an outer flange 108 extending radially outward from the outer surface of the drill string 12. The outer flange 108 applies pressure on the locking and steering unit 20 for expansion of the at least one pad 30.

The force is applied to the pad assemblies 22 and 24 during sliding of the drill barrel 14 within the drill string 12. As said before, the drill barrel 14 slides within the drill string 12 until it contacts the inner flange 104. During sliding of the drill barrel 14 within the drill string 12 the outer flange 108 applies the force to the locking and steering unit 20. As explained before, applying the force to the locking and steering unit 20 draws the ring members 42 and 44 of the locking and steering pad assemblies 22 and 24 together. In this way, the pressure pads 30 of the pad assemblies 22 and 24 are displaced from the contracted condition to the extended condition.

The means 106 for transferring the force also comprises spring means 110. The spring means 110 are located between the outer flange 108 and the bearing housing 32 adjacent the proximal end of the locking and steering unit 20. The spring means 110 comprises a helical spring 112 surrounding the drill barrel 14. The helical spring 112 is included in a housing 114.

The spring means 110 biases the locking and steering unit 20 in the contracted condition. In this manner it is possible to maintain the pad assemblies 22 and 24 in contacted condition when no force is applied to the drill string 12. This is particularly useful for manipulating the apparatus 10 prior to drilling of the borehole and during transport of the drilling apparatus 10. Also, it facilitates driving the drilling apparatus 10 into pre-d rilled boreholes.

Further, the distal end 120 of the drill string 12 comprises also an inner flange 122 which extends radially from the inner surface 124 of the drill string 12. Also, the proximal end 126 of the drill barrel 14 comprises an outer flange 128 extending from the exterior surface 130 of the drill barrel 14. As shown in figure 10, the inner flange 122 of the distal end 120 of the drill string 12 together with the outer flange located at the proximal end 126 of the drill barrel 14 avoids that the drill barrel 14 exits the drill string 12.

The apparatus 10 comprises orientation means 140 to determine the orientation of the drilling apparatus 10 as well of the rotational orientation of the steering pad assembly 24. The orientation means 140 generate signals representative of the orientation of the drill bit 16 and the steering pad assembly 24. Processing means 142 are also provided for processing the signals so as to provide data from which a measure of the orientation of the drilling apparatus 10 as well as of the rotational orientation of the steering assembly 24 can be obtained. In particular, the measure is associated with the physical orientation of the drill bit 16 and the physical location of the wedged bodies 56 of the steering assembly 24 around the drill barrel 14 at a particular moment in time. Figures 23 and 24 show a particular arrangement of the orientation means 140 incorporated in the drilling apparatus 10 in accordance with the second embodiment of the invention.

The measure of the physical orientation of the drill bit 16 at a particular moment of time allows determining the direction at which the borehole is being drilled. Having the measure of the physical orientation of the wedged bodies 56 at a particular moment of time is of particular importance for directing, for example, the drill bit 16 to a desired location during commencement of the directional drilling process or for changing the direction of drilling of the drill bit 16. As will be explained in relation to the method of operation of the pad assemblies 22 and 24, knowing the rotational orientations of the wedged bodies 56 with respect to the outer barrel 26 allows determining in which direction the distal ring member 42 of the steering assembly 24 must be rotated. As explained before, rotation of the distal ring member 42 allows presenting the wedged bodies 56 to the pressure pads 30 to be expanded so as to direct the drilling towards a desired location.

The orientation means 140, the processing means 142 as well as the motor 34 may be activated and operated from the surface. This can be accomplished through fluids such as drilling fluids as well as by lowering a probe into the well. Activation from the surface includes transmitting data from the surface to the orientation means 40. This data is representative of commands that indicates the motor 34 at which angle should the wedged bodies 56 be rotated in order to direct the drill bit 16 to a desired location. For this, the orientation means 140 are adapted to provide instructions to the motor 34 for rotation of the wedged bodies 56.

Also, data representative of the orientation of the drill bit 16 and the rotational orientation of the wedged bodies 56 may be transmitted to the surface to be analysed by the surface personnel in order to transmit commands to the outer barrel 26 for changing the drilling direction or for correcting the drilling path. The data transmission may be done via mud pulse telemetry. Alternatively, the data transmission may be done via radio frequency, electromagnetic and acoustic signals.

Also, the orientations means 140 may be pre-programmed prior to commencement of the drilling operation. For this, the orientations means comprises computer means for activation of the locking and steering unit 20. Programming the orientations means 140 allows prior commencement of the drilling operation to set a pre-determined drilling path for the drilling apparatus 10:

For example, prior to drilling of the borehole the drilling apparatus 34 may be programmed to direct the drill bit 16 to a specific location. Once an pre- established time or the drill bit 16 has reached a pre-established location the locking and steering unit 20 may be activated in order to commence directional drilling or to change the direction of drilling.

As mentioned before, the orientation means 140 generate signals representative of the orientation of the drill bit 16 and the steering pad assembly 24. For this the orientation means 140 comprises sensors such as accelerometers and gyroscopes to determine the orientation of the drilling apparatus 10 as well of the rotational orientation of the steering pad assembly 24. Processing means are also incorporated for processing of the signals received by the sensors. ln operation, after pre-d rilling a borehole with conventional drilling apparatus, the drilling apparatus 10 in accordance with the first embodiment of the invention, is inserted in the borehole. Prior to initiating the directional drilling process, the drilling apparatus 10 is locked within the borehole. This is accomplished by activating the locking pad assembly 22. The activation of the locking pad assembly 22 at this stage may be conducted via activation means driven by fluids such as water or drilling fluids. Electrical or physical mechanical activation may also be possible.

After locking of the drilling apparatus 10 within the borehole, the rotational orientation of the wedged bodies 56 is determined using the processing means 142. Once the rotational orientation of the wedged bodies 56 is known the distal ring 42 of the locking pad assembly 24 is rotated so as to present the three wedged bodies 56 to the three pad assemblies 30 required for expansion in order to direct the drill bit 16 to the desired drilling direction. Generally, the pad assemblies 30 required for expansion are the three pad assemblies located opposite to the direction of drilling. After placing the wedged bodies 56 in the desired position around the drill barrel 14, drilling of the borehole may proceed. Drilling is accomplished by applying a force to the drill string 12. As explained before, this force is also applied to the locking pad assembly 24 for expansion of the three pressure pads 30. The expanded pressures pads 30 apply pressure to the location of the borehole wall which is opposite to the desired drilling direction. This guides the drill bit 16 towards the desired drilling direction.

In accordance with the first embodiment of the invention, the expansion of the steering pad assemblies 24 occur when the drill bit 16 enters in contact with the bottom of the borehole. As the drill bit 16 reaches the bottom of the borehole the force applied by the drill string 12 overcomes the force of the spring means 110. At this stage, the force is applied to the locking and steering unit 20 for expansion of the pressure pads 30. As previously explained, this causes the drilling towards a curved drilling path.

During drilling the force applied to the drill barrel 14 is not only applied to the steering pad assembly 24 for guiding the drill bit 16. The force is also applied to the locking pad assembly 22. Applying the force to the pressure pads 30 of the locking pad assembly 22 further expands the locking pad assembly 22. The further expansion of the pressure pads 30 increases the pressure that is applied by the pressure pads 30 to the borehole wall. This secures the steering unit 24 at the required location around the drill barrel 14. Thus, unintentional rotations of the steering pad assembly 24 are avoided and the desired drilling direction is maintained.

Figures 11 to 15 show a drilling apparatus 200 according to a second embodiment of the invention. The apparatus 200 according to the second embodiment is similar to the apparatus according to the apparatus of the first embodiment and similar reference numerals are used to identify similar parts.

Figure 11 shows an apparatus for drilling 200 in accordance to the second embodiment of the invention. The apparatus for drilling 200 comprises a drill string 12 and a drill barrel 14. A drill bit 16 is attached to the drill barrel 14. The drill barrel 14 is connected to the drill string 12 such that a force applied to the drill string is transferred to the drill bit 16 for drilling of the borehole. The apparatus for drilling 200 further comprises a locking and steering unit 20. The locking and steering unit 20 comprises a locking pad assembly 22, a steering pad assembly 24 and an outer barrel 26. The locking and steering pad assemblies 22 and 24, and the outer barrel 26 are mounted on the drill barrel 14 between the drill bit 16 and the distal end of the drill string 12.

Further, the apparatus for drilling 200 also comprises means for activating the locking and steering unit 20. The locking and steering unit 20 may be activated and/or operated by transferring the force that is being applied to the drill bit 16 for drilling of the borehole. For this, the apparatus for drilling 200 comprises means for transferring the force of the drill string 12 towards the locking and steering unit 20. Figures 2 and 13 show the steering pad assembly 24 of the apparatus 200 for drilling 200 in accordance with the second embodiment of the invention. As said before, the steering pad assembly 24 guides the drill bit 16 to a desired direction during directional drilling. r

The steering assembly 24 comprises an outer cylinder 202 and an inner cylinder 204 located opposite to each other. The outer cylinder 202 and inner cylinder 204 are joined by spring means 206. The inner cylinder 204 is adapted to slide into the outer cylinder 202. The spring means 206 impedes sliding of the inner cylinder 204 into the outer cylinder 202 unless a force is applied to the steering assembly 24. The spring means 206 comprise an helical spring 207 having an end attached to the outer cylinder and an opposite end attached to the inner cylinder such that the inner cylinder is surrounded by the helical spring 207.

The outer cylinder 202 comprises distal and proximal rings 208 and 210 arranged opposite to each other. The distal and proximal rings 208 and 210 are joined together by rods 212. The rods 212 are attached along the circumference of the distal and proximal rings 208 and 210 at spaced apart locations with respect to each other. In this manner, the outer cylinder 202 is defined as a cylinder having a side wall with openings 214 arranged around the circumference of the outer cylinder 202.

The outer cylinder 202 comprises a plurality of pressure pads 30. Each pressure pad 30 is located in one of the openings 214 of the outer cylinder 202. In this manner, the pressure pads 30 are arranged around the circumference of the outer cylinder 202. The pressure pads 30 are hingedly attached to the distal ring though a joint 216. This allows that each pressure pad 30 to pivot between a contracted condition and an expanded condition. The pressure pads 30 are biased towards the contracted position through the spring means 206.

The inner cylinder 204 comprises cylindrical body 218 having a plurality of slots 220 extending longitudinally along the circumference of the cylindrical body 218. In this manner a plurality of longitudinal sections 222 are defined radially around the cylindrical body 218. The plurality of the longitudinal sections 222 are configured as wedged sections 224. In the arrangement shown in figures 2 and 13 the plurality of wedged sections 224 are adjacent to each other and arranged only at an angular section of the circumference of the cylindrical body 218. As will be described with reference to the method of operation of the steering assembly 24, the fact that the wedged sections 224 are located only at an angular section (instead than around the entire circumference) of the cylindrical body 2 8 allows selection of which pressure pads 30 are to be located in expanded condition.

The wedged sections 224 comprise a slanted surface 230. The lowest portion of the slanted surface 230 is presented to the pressure pads 30. The highest portion 64 of the slanted surface 230 is located distal to the pressure pad 30. In this way, the pressure pads 30 can slide over the slanted surface 230 and the pressure pads 30 are progressively expanded as the pressure pads 30 slide over the slanted surface 230.

In the arrangement shown in figure 13, there are three wedged sections 224. Each of the wedged sections 224 will expand the pressure pad 30 located opposite to the wedged sectio 224. The remaining pressure pads 30 are maintained in the contracted condition. In this manner, only three pressure pads 30 will apply pressure to the borehole wall. As was explained with reference to first embodiment of the present invention and the method of operation of the drilling apparatus 10, the fact that only a group of pressure pads 30 apply pressure to the borehole wall allows guiding the drilling operation towards a desired direction. It is possible to select which group of pressure pads 30 will be expanded. This is accomplished by rotating the inner cylinder 204 around the outer barrel. Rotating the inner cylinder 204 presents each wedged sections 224 to the respective pressure pad 30 to be expanded. As said before, the pressure pads 30 are expanded by bringing the inner and outer cylinders 202 together and allowing the inner cylinder 204 to at least partially enter the outer cylinder 202. The fact that it is possible to select the pads 30 that will be displaced is particularly advantageous because it permits directing the drill bit 16 to a desired direction. The drill bit 16 can be directed to specific direction by presenting the three wedged sections 224 to the three pressure pads 30 which when expanded will guide the drilling operation to the desired location.

As was described with reference to the first embodiment regarding the rotations of the distal ring member 42, the inner cylinder 204 may be rotated through a driving unit located in the outer barrel 26. The driving unit will be described with reference figure 24.

Figure 14 shows the locking pad assembly 22. The locking assembly 22 is similar to the steering pad assembly 24 and similar reference numerals are used to identify similar parts. The locking assembly 22, in contrast to the steering assembly 24 of the second embodiment of the invention, includes wedge sections 224 around the entire circumference of the inner cylinder 204. This allows expansion of all of the pressure pads 30 of the outer cylinder 202 as the inner and outer cylinder 202 approach each other.

Figure 15 shows a pressure pad 30 in accordance with the second embodiment. The pressure pad 30 comprises a body 240 having a distal end 242 and a proximal end 244. The body 240 is hingedly attached to the joint

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216 at the distal end 242. The proximalend 244 of the body extends opposite to the distal end of the outer cylinder.

The body of the pressure pad 30 comprises a plurality of transversal slots 246. One of the transversal slots 246 are located adjacent the joint 216. The other transversal slot 246 is located adjacent the proximal end 244 of the body 240 of the pad 30. An indentation 248 extending longitudinally along the body 240 is located between the transversal slots 246. The pressure pad 30 comprises a plurality of wheels 250. Each wheel 250 comprises a plurality of teethed gears 252 located side by side. The wheels 250 are attached transversally to the pressure pads and inside the indentation. This allows the wheels 250 to freely rotate within the indentation 248. In this way, the wheels 250 of each pressure pad 30 are free to rotate against the borehole wall as the pressure pads 30 are in expanded condition.

As was explained with reference to first embodiment of the present invention and the method of operation of the drilling apparatus 200, prior to initiating the directional drilling process, the drilling apparatus 200 is locked within the borehole. This is accomplished by activating the locking pad assembly 22. The activation of the locking pad assembly 22 at this stage in accordance with the second embodiment of the invention may be conducted via activation means including a double shear pin system. ⁷ The double shear pin system affords control of the stage at which the locking assembly is activated. The shear pin system comprises a pin which is adapted to break (shear) when a specific force is applied to the drilling apparatus, thereby allowing activation of the locking assembly. This allows activating the locking system by applying a force of specific magnitude. For example, the shear pin system may be calibrated such that the shear pin is broken as the drill bit contacts the bottom of the borehole. In other arrangements, the shear pin system is calibrated to activate the locking system prior to the drill bit contacting the bottom of the borehole by applying a force of a specific magnitude. _; In an arrangement, in accordance with the present invention, the activation means comprises an activation system 232 of the type shown in figure 14.. The activation system 232 comprises an inner cylinder 234, and distal and proximal outer cylinders 236 and 238. The inner cylinder 234 is included inside the distal and proximal cylinders 236 and 238. In this manner, the outer cylinders 236 and 238 are adapted to slide axially along the inner cylinder 234. As will be described with reference to the method of operation of the activation system 232, the fact that the outer cylinders 236 and 238 are adapted to slide along the inner cylinder 234 allows activation of the locking assembly 22. This is because sliding of the inner and outer cylinder 236 and 238 allows displacement of the outer distal cylinder 236 from a contracted condition to an extended condition and vice versa.

During displacement of the outer distal cylinder 236 from the contracted condition to the extended condition, the outer distal cylinder 236 is driven towards the distal end of the drilling apparatus. The displacement of the outer distal cylinder 236 towards the distal end of the drilling apparatus drives the cylinders 202 and 204 of the locking assembly together expanding the pressure pads 30 of the locking assembly. In this manner, the locking assembly 22 is activated. The locking assembly 22 is deactivated as the outer distal cylinder 236 is returned to the contracted condition.

The outer distal cylinder 236 is biased to rotate around the inner cylinder 234. As will be described with reference to the method of operation of the activation system 232, rotation of the outer distal cylinder 236 allows locking of the outer distal cylinder 236 to the distal end of inner cylinder 234.

As mentioned above, the outer cylinders 236 and 238 are adapted to slide axially along the inner cylinder 234. The inner cylinder 234 comprises a plurality of projections 260 extending around the outer circumference of the inner cylinder 234 defining a plurality of channels 261. The inner surfaces of the outer cylinders 236 and 238 comprise protrusions 262 and 264. The protrusions 262 and 264 extend around the inner circumference of the outer cylinders 236 and 238. The protrusions 262 and 264 are adapted to slide within the channels 260 of the inner cylinder 234. In this manner, the outer cylinder 236 and 238 are guided along the inner cylinder 234. The protrusions 262 and 264 comprise ends 266 and 268. The ends 266 and 268 extend beyond the outer cylinders 236 and 238. The ends 266 and 268 are slanted ends (see figure 14). Further, the ends 236 and 238 are arranged in such a manner that when the outer proximal cylinder 238 and the outer distal cylinder 236 come together the ends 266 and 268 engage each other (see figure 17).

The projections 260 of the inner cylinder 234 comprise distal ends 270. As will be described with reference to the method of operation of the activation system 232, the ends 270 are adapted to lock the outer cylinder 236 in the extended condition. For this, each end 270 comprises a step-like configuration defining a right angled corner adapted to receive a corner of the slanted end 268 (located opposite to the end 270 when the outer distal cylinder 236 is in extended condition) of the outer distal cylinder 236.

As mentioned above, the outer distal cylinder 236 is displaced from a contracted condition to an extended condition in order to activate the locking ¹ assembly 22.

Figures 16 to 19 show the process for locating the outer distal cylinder 236 into the extended condition. Figure 16 shows the outer distal cylinder 236 prior to being displaced to the extended condition. For locating the outer distal cylinder 236 in the extended condition, the outer proximal cylinder 238 is displaced in direction towards to outer distal cylinder 236. The outer proximal cylinder 238 is displaced towards the outer distal cylinder 236 such that the ends 266 and 268 of the outer cylinder 236 and 238 contact each other (see figure 17). At this stage, the outer cylinder 238 pushes the outer distal cylinder 236 towards the distal end of the drilling tool. The outer proximal cylinder 238 is displaced by transferring at least a portion of the force that is applied to the drill during operation of the drilling apparatus. Referring now to figure 18, the outer cylinder 236 is displaced until the ends 268 surpass the ends 270 of the inner cylinder 234. At this stage, the outer cylinder 236 rotates with respect to the inner cylinder 234 to locate the ends 268 of the outer cylinder 236 opposite to the ends 270 of the inner cylinder 234. This allows for the ends 268 to engage the ends 270 of the inner cylinder 234 (see figure 19). In this manner, rotation of the outer cylinder 236 is stopped and the outer distal cylinder 236 is locked in the extended condition.

Figures 20 to 22 show the process of unlocking the outer cylinder 236 from the extended condition to the contracted condition. This deactivates the locking assembly 22. For unlocking of the outer cylinder 236 from the extended condition, the outer cylinder 236 is displaced along the inner cylinder 234 so that it contacts the outer cylinder 236 and pushes the outer cylinder 236 to release the ends 268 from the end 270 of the inner cylinder 234 (see figure 21). After releasing the ends 268 from the ends 270, the outer cylinder 236 rotates around the inner cylinder to locate each end 268 of the outer cylinder opposite to the counterpart channel 260 of the inner cylinder 234. At this stage, the protrusions 264 enter the channel 260 and the outer cylinder 236 is displaced together with the outer cylinder 238 to the proximal end of the drilling apparatus (see figure 22). In view that the outer cylinder 236 has returned to the contracted condition, the pad assembly is deactivated.

Figure 23 shows an alternative arrangement of the steering assembly 24 of the drilling apparatus 200 according to a second embodiment of the invention. The steering assembly 24 according to the alternative arrangement shown in figure 23 is similar to the steering assembly shown in figures 11 to 15 similar reference numerals are used to identify similar parts.

The steering assembly 24 shown in figure 23 comprises an outer cylinder 202 and an inner cylinder 204. The outer cylinder 202 is defined by a distal ring 208 at which the pressure pads 30 are attached. The pressure pads 30 are arranged at a spaced apart relationship around the circumference of the distal ring 208 defining the outer cylinder 202. The pressure pads 30 are hingedly attached to the distal ring though a joint 216. This allows that each pressure pad 30 to pivot selectively between a contracted condition and an expanded condition. The inner cylinder 204 comprises a proximal ring 206 having a wedged section 224. The wedged section 224 extends partially radially around the proximal ring 206. In this particular arrangement the wedge section 224 extends over a particular angular section of the circumference of the proximal ring 26. The fact that the wedged section 224 is located only at an angular section (instead than around the entire circumference) of the proximal ring 206 allows selection of which pressure pads 30 are to be located in expanded condition.

The wedged section 224 comprise a slanted surface 230. The lowest portion of the slanted surface 230 is presented to the pressure pads 30. The highest portion of the slanted surface 230 is located distal to the pressure pad 30. In this manner, the pressure pads 30 can slide over, the slanted surface 230 and the pressure pads 30 are progressively expanded as the pressure pads 30 slide over the slanted surface 230 as the inner cylinder 204 is inserted into the outer cylinder 202.

As mentioned before, the alternative arrangement of the steering assembly 24 shown in figure 23, comprises a single wedged section 224. The wedged section 224 will expand the pressure pads 30 located opposite to the wedged section 224. The remaining pressure pads 30 are maintained in the contracted condition. In this manner, the pressure pads 30 (located opposite to the wedged section 224) will apply pressure to the borehole wall. As was explained with reference to first embodiment of the present invention and the method of operation of the drilling apparatus 10, the fact that only a group of pressure pads 30 apply pressure to the borehole wall allows guiding the drilling operation towards a desired direction.

It is possible to select which group of pressure pads 30 will be expanded. This is accomplished by rotating the inner cylinder 204 around the outer barrel. Rotating the inner cylinder 204 presents each wedged section 224 to the respective pressure pads 30 to be expanded. As said before, the pressure pads 30 are expanded by bringing the inner and outer cylinders 202 together and allowing the inner cylinder 204 to at least partially enter the outer cylinder 202. The fact that it is possible to select the pads 30 that will be displaced is particularly advantageous because it permits directing the drill bit 16 to a desired direction. The drill bit 16 can be directed to specific direction by presenting the three wedged sections 224 to the three pressure pads 30 which when expanded will guide the drilling operation to the desired location. As was described with reference to the first embodiment regarding the rotations of the distal ring member 42, the inner cylinder 204 may be rotated through a driving unit located in the outer barrel 26. The driving unit is shown in figure 24.

Figure 24 shows a driving unit 300 used for rotating the distal ring member 42. The driving unit 300 comprises the orientation means 140, an on-board power supply 302, an arrangement of processors 304 and sensors 306, and micromotors 308. The orientation means 140 are adapted to provide instructions to the micro-motors 308 for rotation of the wedged section 224. As mentioned before, rotating the wedged section 224 allows selection of which of the pressure pads 30 are to be expanded. This allows directing the drilling to a particular direction.

It is evident that the drilling apparatus 10 in accordance with the embodiment first and second embodiments of the invention provides an effective and efficient manner for drilling a curved borehole path. The drilling apparatus 10 does not require systems based on fluids for activating the pressure pads 30. Instead, the pad assemblies are activated using the force that is applied to the drill bit 16 for drilling of the borehole.

Further, the drilling apparatus 10 in accordance with the present embodiments of the invention does not include a fixed (unchangeable) tool face. Instead, the drilling apparatus 10 in accordance with the present embodiments of the invention comprise pressure pads which are located symmetrically around the periphery of the drilling tool. The pressure pads 30 can be independently activated so as to apply pressure to specific locations of the wall of the borehole that is being drilled. This causes the position of the drill bit to deviate in order for the drilling apparatus to follow a curved path. The fact that the pressure pads located at different angular locations around the drilling tool may be activated independently from each other allows for the tool face (the orientation at which the drill bit of the drilling apparatus 10 is pointing) to be changed by expanding any particular pressure pad or pads 30. In view that the toolface may be changed it is not required to orient from the surface the drilling apparatus 10 to a particular direction in order to drill towards that particular direction. In contrast, in accordance with the present embodiments of the invention, the drilling orientation may be changed by selecting the particular pads 30 which allow drilling to the desired location. Selection of the particular pads that are to be expanded is conducted by the orientation means 140. As mentioned before, the orientation means 140 are adapted to provide instructions to the micro-motors 308 for rotation of the wedged section 224. In this manner, the present embodiments of the invention provide a dynamic tool face that can be changed as desired by rotating the distal ring member 42 through the motors 308 or 34.

In particular arrangement of the present embodiments of the invention the orientation means 140 may be programmed to provide instructions to the micro- motors 308 or 34 such that the drilling apparatus follow a particular path.

Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention. Further, it should be appreciated that the scope of the invention is not limited to the scope of the embodiment disclosed.

For example, in the arrangement shown in the drawings, the locking pad assembly 22 is adjacent to the steering pad assembly 24. In accordance with other embodiments of the invention, the locking pad assembly may be included on the locking and steering unit 20 at a location distal to the steering assembly. Moreover, the drilling apparatus 10 in accordance with other embodiments of the invention may include a steering assembly 24 as shown in the attached drawings. However, the locking pad assembly 20 may be any conventional locking pad assembly known in the art.

Furthermore, the locking assembly 20 in accordance with other embodiments of the invention may incorporate a wedge section 224 as shown in figure 23. However, in this particular arrangement, the wedged section 224 of the locking 20 would surround the entire circumference of the proximal ring member 204.

In the arrangements of the previously described embodiments the selection of the particular pressure pad or pressure pads that are to expanded for changing the drilling direction occurs by presenting the wedged section to the particular pressure pads or pad. The wedged sections are presented to the particular pressure pads or pad by rotating the wedge section around the outer barrel. In an alternative arrangement, the particular pressure pads or the pressure pad that are to be expanded may be the ones that are rotated to as to present the pad or pads to the wedged section. Throughout the specification and claims, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.