Patent Publication Number: US-2016237748-A1

Title: Deviated Drilling System Utilizing Force Offset

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of and priority to U.S. Provisional Application Ser. No.: 62/116,534, filed Feb. 15, 2015, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Drilling systems are employed for drilling a variety of wellbores. A drilling system may comprise a drill string and a drill bit which is rotated to drill a wellbore through a desired subterranean formation. In various drilling applications, a desired borehole trajectory is planned and calculated prior to drilling based on geological data. A number of steering techniques and equipment types may be employed to achieve a planned trajectory. For example, a bottom hole assembly may comprise a drill bit, stabilizers, drill collars, a mud motor, and a bent housing which cooperate to control a drilling direction. In other applications, a rotary steerable tool may be used to enable directional drilling while rotating a drill string. Rotary steerable drilling systems utilize various components including stabilizers, actuator pads, and other components to control the drilling direction. However, existing systems tend to be complex assemblies with multiple moving parts, and this complexity can lead to service quality issues and downtime. 
     SUMMARY 
     In general, a system and methodology are provided to facilitate steering during, for example, a borehole drilling operation. A steering tool is employed to control an orientation of a drill bit or other component. The steering tool provides a simple structure comprising a tool body and at least one actuator, e.g. a piezo actuator or other suitable actuator. The at least one actuator is selectively displaced via application of controlled inputs, e.g. electrical or hydraulic inputs. Appropriate application of the inputs enables selective deformation of the actuator(s) in a manner which changes the orientation of the drill bit or other component to a predetermined, desired orientation. 
     However, many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein, and: 
         FIG. 1  is a schematic illustration of an example of a drilling system deployed in a wellbore, according to an embodiment of the disclosure; 
         FIG. 2  is a cross-sectional schematic illustration of an example of a steering tool which may be positioned in a drilling system, e.g. the drilling system illustrated in  FIG. 1 , according to an embodiment of the disclosure; 
         FIG. 3  is a cross-sectional schematic illustration taken generally along line  3 - 3  of  FIG. 2 , according to an embodiment of the disclosure; 
         FIG. 4  is a schematic illustration of an example of a piezo actuator which can be used in the steering tool, according to an embodiment of the disclosure; 
         FIG. 5  is a schematic illustration of an example of another piezo actuator which can be used in the steering tool, according to an embodiment of the disclosure; 
         FIG. 6  is a cross-sectional schematic illustration of another example of a steering tool, according to an embodiment of the disclosure; 
         FIG. 7  is a cross-sectional schematic illustration of another example of a steering tool, according to an embodiment of the disclosure; 
         FIG. 8  is a cross-sectional schematic illustration similar to that of  FIG. 2  but showing another example of a steering tool, according to an embodiment of the disclosure; 
         FIG. 9  is a cross-sectional schematic illustration of another example of a steering tool, according to an embodiment of the disclosure; 
         FIG. 10  is a cross-sectional schematic illustration taken generally along line  10 - 10  of  FIG. 9 , according to an embodiment of the disclosure; 
         FIG. 11  is an illustration of another example of a piezo actuator which may be used in the steering tool, according to an embodiment of the disclosure; 
         FIG. 12  is a cross-sectional schematic illustration of another example of a steering tool, according to an embodiment of the disclosure; 
         FIG. 13  is a cross-sectional schematic illustration taken generally along line  13 - 13  of  FIG. 12 , according to an embodiment of the disclosure; 
         FIG. 14  is a schematic side view of the steering tool illustrated in  FIG. 12 , according to an embodiment of the disclosure; and 
         FIG. 15  is a schematic illustration of an example of a steering tool utilized in a steerable motor application, according to an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. 
     The present disclosure generally relates to a system and methodology which facilitate steering during, for example, a borehole drilling operation. For example, the technique may be used for drilling deviated wellbores. According to embodiments described herein, a steering tool is employed to control an orientation of a drill bit or other component. By way of example, the steering tool may comprise a tool body and at least one actuator, e.g. a piezo actuator. In a specific embodiment, at least one piezo actuator is selectively displaced via application of electrical inputs. Appropriate application of electrical inputs enables selective deformation of the piezo actuator in a manner which changes the orientation of the drill bit or other component to a predetermined, desired orientation. In some applications, the piezo actuator may be replaced or supplemented with mechanical, e.g. hydraulic, actuators such as fluidic muscle actuators. 
     According to an embodiment, a new actuation scheme is defined for a steering tool, such as a rotary steerable drilling tool. In some applications, the new actuation scheme may be implemented in a steerable motor system with a downhole controlled bend section. In a specific embodiment, the actuation scheme comprises applying forces generally parallel to an axis of rotation. The forces may be applied to change the orientation of a drill bit or other component by applying a series of forces offset from the axis of rotation. In some applications, a series of actuators may be actuated in a specific combination/order such that a desired displacement is provided at the drill bit. 
     Embodiments of the steering tool described herein can be used to provide a simple, cost-effective, and reliable steering tool able to provide directional control during drilling operations. In some embodiments, the forces are generated by actuators such as actuators which are in the form of piezo-electric devices serving as piezo actuators. Depending on the parameters of a given application, many types of piezo actuators may be employed. However examples include a piezo electric stack (e.g. a ø56 mm×154 mm long stack) where displacements of 0.180 mm can be achieved with, for example, a 78 kN force and a response time of &lt;1 ms up to 150° C. 
     It should be noted that other actuation methods also may be employed in some applications. For example, such other applications may utilize fluidic muscle (e.g. a fluidic muscle of nominal ø40 mm which provides 6 kN of contraction at 0.6 Mpa). The fluidic muscle system is a hydraulic/mechanical system which utilizes fluids in the actuators to achieve the desired actuation forces. The embodiments described herein also may be used to provide a device which can be locked into a state such that straight drilling is achieved without drilling an over-gauged hole (as is the case when using a bent angle such as in a positive displacement motor system). 
       FIG. 1  illustrates an example of a wellsite system in which embodiments described herein may be employed. The wellsite may be onshore or offshore. In a wellsite system, a borehole  20  is formed in a subsurface formation by drilling. The method of drilling to form the borehole  20  may include, but is not limited to, rotary and directional drilling. A drill string  22  is suspended within the borehole  20  and has a bottom hole assembly (BHA)  24  that includes a drill bit  26  at its lower end. 
     An embodiment of a surface system includes a platform and derrick assembly  28  positioned over the borehole  20 . An example of assembly  28  includes a rotary table  30 , a kelly  32 , a hook  34  and a rotary swivel  36 . The drill string  22  is rotated by the rotary table  30 , energized by a suitable system (not shown) which engages the kelly  32  at the upper end of the drill string  22 . The drill string  22  is suspended from the hook  34 , attached to a traveling block (not shown) through the kelly  32  and the rotary swivel  36  which permits rotation of the drill string  22  relative to the hook  34 . A top drive system can be used in other embodiments. 
     An embodiment of the surface system also includes a drilling fluid  38 , e.g., mud, stored in a pit  40  formed at the wellsite. A pump  42  delivers the drilling fluid  38  to the interior of the drill string  22  via one or more ports in the swivel  36 , causing the drilling fluid to flow downwardly through the drill string  22  as indicated by directional arrow  44 . The drilling fluid exits the drill string  22  via one or more ports in the drill bit  26 , and then circulates upwardly through the annulus region between the outside of the drill string  22  and the wall of the borehole, as indicated by directional arrows  46 . In this manner, the drilling fluid lubricates the drill bit  26  and carries formation cuttings and particulate matter up to the surface as it is returned to the pit  40  for recirculation. 
     The illustrated embodiment of bottom hole assembly  24  includes one or more logging-while-drilling (LWD) modules  48 / 50 , one or more measuring-while-drilling (MWD) modules  52 , one or more roto-steerable systems and motors (not shown), and the drill bit  26 . It will also be understood that more than one LWD module and/or more than one MWD module may be employed in various embodiments, e.g. as represented at  48  and  50 . It should also be noted that some applications may utilize the steering tool without MWD or LWD modules. 
     The LWD module  48 / 50  may be housed in a type of drill collar, and includes capabilities for measuring, processing, and storing information, as well as for communicating with the surface equipment. The LWD module  48 / 50  also may include a pressure measuring device and one or more logging tools. 
     The MWD module  52  also may be housed in a type of drill collar, and includes one or more devices for measuring characteristics of the drill string  22  and drill bit  26 . The MWD module  52  also may include one or more devices for generating electrical power for the downhole system. In an embodiment, the power generating devices include a mud turbine generator (also known as a “mud motor”) powered by the flow of the drilling fluid. In other embodiments, other power and/or battery systems may be employed to generate power. 
     The MWD module  52  also may include one or more of the following types of measuring devices: a weight-on-bit measuring device, a torque measuring device, a vibration measuring device, a shock measuring device, a stick slip measuring device, a direction measuring device, and an inclination measuring device. These measuring devices may be used individually or in various combinations. 
     In an operational example, the wellsite system of  FIG. 1  is used in conjunction with controlled steering or “directional drilling.” Directional drilling is the intentional deviation of the wellbore from the path it would naturally take. In other words, directional drilling is the steering of the drill string  22  so that it travels in a desired direction. Directional drilling is, for example, useful in offshore drilling because it allows multiple wells to be drilled from a single platform. Directional drilling also enables horizontal drilling through a reservoir. Horizontal drilling, in turn, enables a longer length of the wellbore to traverse the reservoir, which increases the production rate from the well. 
     A directional drilling system also may be used in vertical drilling operations. Often the drill bit will veer off of a planned drilling trajectory because of the unpredictable nature of the formations being penetrated or the varying forces that the drill bit experiences. When such a deviation occurs, a directional drilling system may be used to put the drill bit back on course. 
     A method of directional drilling includes the use of a rotary steerable system (“RSS”). In an embodiment that employs the wellsite system of  FIG. 1  for directional drilling, a steerable tool or subsystem  54  is provided. In an RSS, the drill string may be rotated from the surface, and downhole devices cause the drill bit to drill in the desired direction. Rotating the drill string greatly reduces the occurrences of the drill string getting hung up or stuck during drilling. Rotary steerable drilling systems for drilling deviated boreholes into the earth may be generally classified as either “point-the-bit” systems or “push-the-bit” systems. 
     In an example of a “point-the-bit” rotary steerable system, the axis of rotation of the drill bit is deviated from the local axis of the bottom hole assembly in the general direction of the new hole. The hole is propagated in accordance with the customary three-point geometry defined by upper and lower stabilizer touch points and the drill bit. The angle of deviation of the drill bit axis coupled with a finite distance between the drill bit and lower stabilizer results in the non-collinear condition for a curve to be generated. This may be achieved in a number of different ways, including a fixed bend at a point in the bottom hole assembly close to the lower stabilizer or a flexure of the drill bit drive shaft distributed between the upper and lower stabilizer. In its idealized form, the drill bit is not required to cut sideways because the bit axis is continually rotated in the direction of the curved hole. Examples of “point-the-bit” type rotary steerable systems and their operation are described in U.S. Pat. Nos. 6,394,193; 6,364,034; 6,244,361; 6,158,529; 6,092,610; and 5,113,953; and U.S. Patent Application Publication Nos. 2002/0011359 and 2001/0052428. 
     In an example of a “push-the-bit” rotary steerable system, there is no specially identified mechanism that deviates the bit axis from the local bottom hole assembly axis. Instead, the requisite non-collinear condition is achieved by causing either or both of the upper or lower stabilizers to apply an eccentric force or displacement in a direction that is orientated with respect to the direction of hole propagation. This may be achieved in a number of different ways, including non-rotating (with respect to the hole) eccentric stabilizers (displacement based approaches) and eccentric actuators that apply force to the drill bit in the desired steering direction. Steering is achieved by creating non co-linearity between the drill bit and at least two other touch points. In its idealized form, the drill bit is forced to cut sideways to generate a curved hole. Examples of “push-the-bit” type rotary steerable systems and their operation are described in U.S. Pat. Nos. 6,089,332; 5,971,085; 5,803,185; 5,778,992; 5,706,905; 5,695,015; 5,685,379; 5,673,763; 5,603,385; 5,582,259; 5,553,679; 5,553,678; 5,520,255; and 5,265,682. 
     Referring generally to  FIGS. 2 and 3 , an example of steering tool  54  is illustrated as combined with drill bit  26 . In this example, the steering tool  54  comprises a tool body  56  which may be in the form of a collar. The steering tool  54  also comprises at least one actuator  58  which deforms in response to controlled inputs, e.g. electrical inputs. By way of example, the at least one actuator  58  may comprise a piezo-electric material and thus be in the form of a piezo actuator. In the illustrated example, a plurality of piezo actuators  58 , e.g. three, four or more actuators, is illustrated. During rotation of drill bit  26  via, for example, rotation of drill string  22  and/or a downhole motor, the steering tool  54  controls the trajectory of a borehole being drilled. Effectively, the steering tool  54  changes the angular orientation of the drill bit  26  by selectively displacing individual piezo actuators  58  in a longitudinal direction, as represented by arrow  60 . The longitudinal direction  60  is oriented along the length of tool body  56  and may be generally parallel with a longitudinal axis  62  of steering tool  54 . 
     In this example, the actuators  58  are selectively fired via application of electrical inputs so that the drill bit  26  and drilling direction can be deviated along a desired trajectory. At locations where the actuators  58  are not firing, the actuators  58  may be left unconstrained, or the actuators  58  may be attached and operated such that expansion, e.g. elongation, of one actuator  58  is matched by contraction of an opposing actuator  58  or another suitable actuator  58  to obtain the desired bending. In a variety of applications, the actuators  58  fire as the steering tool  54  rotates with a speed of rotation that matches the speed of tool body/collar rotation. In other applications, however, the speed of rotation may not be matched so as to obtain another desired wellbore trajectory. Regardless, the actuators  58  may be selectively expanded and contracted to provide the desired forces and the desired trajectory. 
     By forming actuators  58  as piezo actuators, the actuators are capable of precise movements which exert high force. Piezo actuators also are compact, have low energy consumption, quick response times, and no electromagnetic interference. The piezo actuators  58  can be actuated by applying a voltage as illustrated in  FIG. 4 . This enables the actuator  58  to provide small displacements with a large amount of force. In some applications, a plurality of piezo actuators may be stacked together (and pre-wired/packaged) to form a single overall actuator  58 , as illustrated in  FIG. 5 . This enables actuations with suitable displacements and large amounts of force which can be used, for example, at or inside the drill bit  26  or at other desired positions. 
     Instead of utilizing the actuators  58  directly against the drillbit  26 , however, the actuators  58 , e.g. piezo actuators, may be mounted along tool body  56  and selectively actuated to deform a weakened section  64  of the tool body/drill collar  56 , as illustrated in  FIG. 6 . The weakened section  64  may have a variety of constructions including that of a separately installed component. For example, the weakened section  64  can be a joint, e.g. a universal joint or flex joint. In these embodiments, the weakened section  64  provides a section of the tool body/drill collar  56  which is more flexible than the rest of the tool body  56 . In the specific example illustrated, the piezo actuators  58  may be selectively elongated to cause bending of the tool body  56  and thus deviation of the drill bit  26  such that the drill bit  26  is oriented to drill in a new direction. In this and certain other embodiments, the piezo actuators  58  also may be controlled to provide a straight (non-bent) tool body  56  to enable straight drilling without drilling an over-gauged borehole. 
     In some applications, each actuator  58  may be constructed from a plurality of pieces  66 , e.g. piezo-electric actuator discs, positioned independently along the tool body  56 , as illustrated in  FIG. 7 . The individual pieces or portions  66  of the actuator  58  may be selectively fired or actuated via electrical input to cause bending of the tool body  56  and thus deviation of the drill bit  26 . In some applications, the individual portions  66  may be constructed to extend circumferentially along at least a portion of the tool body  56 , as illustrated in  FIG. 8 . By way of example, this type of embodiment can be used in a sliding (oriented) mode. It should also be noted that in this and other embodiments, a driveshaft may be positioned through a center of the tool body  56  to provide additional rotation to the drill bit  26  if desired. 
     In some embodiments, bending actuators  58  (e.g. three, four or more bending actuators) may be used, as illustrated in  FIGS. 9-11 . In these types of embodiments, application of controlled inputs to the actuators  58 , e.g. application of electrical inputs to piezo actuators  58 , causes the actuators  58  to deform in a lateral direction as indicated by arrows  68 . The electrical inputs can be used to effectively bend the actuator  58  in a controlled manner, as illustrated in  FIG. 11 . In some applications, the actuators  58  may again be used in combination with weakened area  64  such that bending of the actuators  58  causes bending of the tool body/drill collar  56  and thus deviation of drill bit  26 . 
     In another embodiment, a series of the actuators  58  may be placed into a tube, e.g. embedded into a tubular tool body  56 , as illustrated in  FIGS. 12-14 . The actuators  58  may be in the form of discs or other suitable structures able to establish a stress field when inputs, e.g. electrical inputs, are selectively applied to the actuators. The stress field causes a controlled bending of the tube, e.g. tubular tool body  56 . This bending motion is again translated into deviation of the drill bit  26 . 
     In the embodiments discussed above, actuators  58  have been described as piezo actuators, however actuators  58  also may comprise other types of integral actuators able to control bending of the tool body/drill collar  56  and thus deviation of drill bit  26 . For example, actuators  58  may be in the form of hydraulic actuators, e.g. fluidic muscle actuators which utilize fluidic muscle to selectively cause the straightening or bending of the tool body/drill collar  56  to control drilling direction. The fluidic muscle system is a hydraulic/mechanical system which utilizes fluids in the actuators to achieve the desired actuation forces. In other words, fluid inputs are used rather than electrical inputs to control the bending and drilling direction. Additionally, other types of actuators also can be used to achieve the desired, control bending and consequent steering control. 
     Referring generally to  FIG. 15 , an embodiment is illustrated in which a plurality of the actuators  58 , e.g. piezo actuators, is used with a downhole steerable motor  70  having a downhole adjustable bent angle section  72 . By way of example, the downhole steerable motor  70  may comprise a positive displacement motor having a rotor  74  which is rotatably driven within a stator  76 . The rotor  74  is coupled with a drill bit shaft  78  rotatably mounted within bearings  80 . The drill bit shaft also is coupled to the drill bit  26  to enable roatation of the drill bit  26  by motor  70 . The actuators  58  may be operated to adjust the bent angle section  72  and to thus adjust a bend angle  82 . This embodiment may be used to enable directional drilling without conventional tool face control. In some applications, the actuators  58  may be used to adjust the tool face and the bend angle at the same time through, for example, dynamic control of the actuators  58 . This latter type of embodiment enables drilling of a borehole while rotating 100% without sliding. 
     Depending on the parameters of a given application, the steering tool  54  may utilize a variety of structures and techniques to control the orientation of drill bit  26 . For example, various electro-mechanical, electro-magnetic, hydraulic, pneumatic, magneto-rheological, and/or other devices may be incorporated into the steering tool  54  to facilitate deviation of the drill bit  26  and to provide control over the direction of drilling. Additionally, a closed loop control system may be used to provide feedback with respect to the direction of drilling and/or other aspects of the drilling operation. 
     In some applications, the closed loop control system may enable vibration measurement so as to facilitate damping of vibrations to help optimize drilling parameters such as rate of penetration and/or drill bit life. In some embodiments, material, e.g. the material of tool body  56 , may be formed directly around the actuators  58  to provide protection from the drilling environment. For example, additive manufacturing can be used to embed the actuators  58  by building up material around them. However, the actuators  58  also can be fitted into pockets or otherwise affixed, mounted to, or attached to the tool body  56 . 
     Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.