Patent Publication Number: US-11643877-B2

Title: Self-adjusting directional drilling apparatus and methods for drilling directional wells

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation and claims priority to U.S. patent application Ser. No. 14/667,026, filed Mar. 24, 2015, the contents of which are incorporated herein in their entirety. 
    
    
     BACKGROUND 
     1. Field of the Disclosure 
     This disclosure relates generally to drilling directional wellbores. 
     2. Background of the Art 
     Wellbores or wells (also referred to as boreholes) are drilled in subsurface formations for the production of hydrocarbons (oil and gas) using a drill string that includes a drilling assembly (commonly referred to as a “bottomhole assembly” or “BHA”) attached to a drill pipe bottom. A drill bit attached to the bottom of the drilling assembly is rotated by rotating the drill string from the surface and/or by a drive, such as a mud motor in the drilling assembly. A common method of drilling curved sections and straight sections of wellbores (directional drilling) utilizes a fixed bend AKO mud motor to provide a selected bend to the drill bit to form curved sections of wells. To drill a curved section, the drill string rotation from the surface is stopped, the bend of the AKO is directed into the desired build direction and the drill bit is rotated by the mud motor. Once the curved section is complete, the drilling assembly including the bend is rotated from the surface to drill a straight section. Such methods produce uneven boreholes. The borehole quality degrades as the bend is increased causing effects like spiraling of the borehole. Other negative borehole quality effects attributed to the rotation of bent assemblies include drilling of over-gauge boreholes, borehole breakouts, and weight transfer. Such apparatus and methods also induce high stress and vibrations on the mud motor components compared to drilling assembles without an AKO and create high friction between the drilling assembly and the borehole due to the bend contacting the borehole as the drilling assembly rotates. Consequently, the maximum build rate is reduced by reducing the angle of the bend of the AKO to reduce the stresses on the mud motor and other components in the drilling assembly. Such methods result in additional time to drill the wellbore and thus may drive expenses far higher. Therefore, it is desirable to provide drilling assemblies and methods for drilling curved wellbore sections with a bend and straight sections without a bend in the drilling assembly to reduce stresses on the drilling assembly components. 
     The disclosure herein provides apparatus and methods for drilling wellbores, wherein the drilling assembly includes a deflection device that self-adjusts to provide a desired tilt for drilling curved sections and straightens itself when the drilling assembly is rotated for drilling straight wellbore sections. 
     SUMMARY 
     In one aspect, an apparatus for drilling curved and straight sections of a wellbore is disclosed that in one non-limiting embodiment includes a drilling assembly configured to include a drill bit at an end thereof that can be rotated by a drive in the drilling assembly and by rotating the drilling assembly from a surface location, wherein the drilling assembly includes a deflection device that (i) tilts a section of the drilling assembly with respect to a selected axis or within selected plane when the drilling assembly is substantially stationary to allow drilling a curved section of the wellbore by rotating the drill bit by the drive; and (ii) straightens the lower section when the drilling assembly is rotated to allow drilling of a straight section of the wellbore. 
     In another aspect, a method of drilling a wellbore is disclosed that in one non-limiting embodiment includes: conveying a drilling assembly in the wellbore that includes a drive for rotating a drill bit, a deflection device that tilts the drilling assembly with respect to a selected axis or within a selected plane when the drilling assembly is substantially stationary and straightens the drilling assembly when the drilling assembly is rotated; maintaining the drilling assembly substantially stationary to enable the drilling assembly housing to tilt; applying a weight on the drill bit; and rotating the drill bit by the drive to drill a curved section of the wellbore 
     Examples of the more important features of a drilling apparatus have been summarized rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are additional features that will be described hereinafter and which will form the subject of the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a detailed understanding of the apparatus and methods disclosed herein, reference should be made to the accompanying drawings and the detailed description thereof, wherein like elements are generally given same numerals and wherein: 
         FIG.  1    shows a drilling assembly in a curved section of a wellbore that includes a deflection device or mechanism for drilling curved and straight sections of the wellbore, according to one non-limiting embodiment of the disclosure; 
         FIG.  2    shows the deflection device of the drilling assembly of  FIG.  1    when the a lower section of the drilling assembly is tilted; 
         FIG.  3    shows the deflection device of the drilling assembly of  FIG.  1    when the lower section of the drilling assembly is straight; 
         FIG.  4    shows a non-limiting embodiment of a deflection device that includes a force application device that initiates the tilt in a drilling assembly, such as the drilling assembly shown in  FIG.  1   ; 
         FIG.  5    shows another non-limiting embodiment of a hydraulic deflection device that that initiates the tilt in a drilling assembly, such as the drilling assembly shown in  FIG.  1   ; and 
         FIGS.  6 A and  6 B  show certain details of a dampener, such as the dampener shown in  FIGS.  2 - 5    to reduce or control the rate of the tilt of the drilling assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     In aspects, the disclosure herein provides a drilling assembly or BHA that includes a deflection device that initiates a tilt to enable drilling of curved sections of wellbores and straightens itself to enable drilling of straight (vertical and tangent) sections of the wellbores. Such a drilling assembly prevents or reduces borehole spiraling, reduces friction between the drilling assembly and the wellbore during drilling of straight sections, reduces stress on components of the drilling assembly, such as a downhole drive (such as a mud motor), and also allows for easy positioning of the drilling assembly for directional drilling. Such a drilling assembly allows drilling of straight sections without a bend in the drilling assembly when the drilling assembly is rotated and allows drilling a curved section when the drilling assembly is stationary (not rotated) while the drill bit is rotated with the downhole drive. In aspects, such drilling is achieved by using a self-adjusting articulation joint to create a tilt in the drilling assembly when the drill string and thus the drilling assembly is stationary (not rotating) and using a dampener to maintain the drilling assembly straight when the drilling assembly is rotated. In other aspects a force application device, such as a spring or a hydraulic device, may be utilized to initiate the tilt by applying a force into a hinged direction when the drilling assembly is not rotated. 
       FIG.  1    shows a drilling assembly  100  in a curved section of a wellbore  101 . In a non-limiting embodiment, the drilling assembly  100  includes a deflection device (also referred herein as a flexible device or a deflection mechanism)  120  for drilling curved and straight sections of the wellbore  101 . The drilling assembly  100  further includes a downhole drive or drive, such as a mud motor  140  having a stator  141  and rotor  142 . The rotor  142  is coupled to a transmission, such as a flexible shaft  143  that is coupled to another shaft  146  disposed in a bearing assembly  145 . The shaft  146  is coupled to a drill bit  147 . The drilling assembly  100  further includes a drill bit  147  that rotates when the rotor  142  of the mud motor  140  rotates due to circulation of a drilling fluid, such as mud, during drilling operations. The drilling assembly  100  is connected to a drill pipe  148 , which is rotated from the surface to rotate the drilling assembly  100  and thus the drill bit  147 . In the particular drilling assembly configuration shown in  FIG.  1   , the drill bit  147  may be rotated by rotating the drill pipe  148  and thus the drilling assembly  100  and/or the mud motor  140 . The rotor  142  rotates the drill bit  147  when a fluid is circulated through the drilling assembly  100 . The drilling assembly  100  further includes a deflection device  120 . While in  FIG.  1    the deflection device  120  is shown below the mud motor  140  (drive) and coupled to a lower section, such as housing or tubular  160  disposed over the bearing section  145 , the deflection device  120  may also be located above the drive  140 . In various embodiments of the deflection device  120  disclosed herein, the housing  160  tilts a selected amount along a selected plane to tilt the drill bit  147  along the selected plane to allow drilling of curved borehole sections. As described later in reference to  FIGS.  2 - 6   , the tilt is initiated when the drilling assembly  120  is stationary (not rotating) or substantially rotationally stationary. The curved section is then drilled by rotating the drill bit by the mud motor  140  without rotating the drilling assembly  120 . The lower section  160  straightens when the drilling assembly is rotated, which allows drilling of straight wellbore sections. Thus, in aspects, the deflection device  120  provides a selected tilt in the drilling assembly  100  that allows drilling of curved sections when the drill pipe  148  and thus the drilling assembly is substantially rotationally stationary and the drill bit  147  is rotated by the drive  140 . However when the drilling assembly  100  is rotated, such as by rotating the drill pipe  148  from the surface, the tilt straightens and allows drilling of straight borehole sections, as described in more detail in reference to  FIGS.  2 - 6   . In one embodiment, a stabilizer  150  is provided below the flexible device  120  (between the flexible device  120  and the drill bit  147 ) that initiates a bending moment in the deflection device  120  and also maintains the tilt when the drilling assembly  100  is not rotated and a weight on the drill bit is applied during drilling of the curved borehole sections. In another embodiment a stabilizer  152  may be provided above the deflection device  120  in addition to or without the stabilizer  150  to initiate the bending moment in the deflection device  120  and to maintain the tilt during drilling of curved borehole sections. In other embodiments, more than one stabilizer may be provided above and/or below the deflection device  120 . Modeling may be performed to determine the location and number of stabilizers for optimum operation. 
       FIG.  2    shows a non-limiting embodiment of a deflection device  120  for use in a drilling assembly, such as the drilling assembly  100  shown in  FIG.  1   . Referring to  FIGS.  1  and  2   , in one non-limiting embodiment, the deflection device  120  includes a pivot member, such as a pin  210  having an axis  212  perpendicular to the longitudinal axis  214  of the drilling assembly  100 , about which the housing  270  of a lower section  290  of the drilling assembly  100  tilts or inclines a selected amount relatively to the transmission  143  about the plane defined by the axis  212 . The housing  270  tilts between a straight end stop  282  and an inclined end stop  280  that defines the maximum tilt. When the housing  270  of the lower section  290  is tilted in the opposite direction, the straight end stop  282  defines the straight position of the drilling assembly  100 , where the tilt is zero. In such an embodiment, the housing  270  tilts only along a particular plane or radial direction. One or more seals, such as seal  284 , is provided between the inside of the housing  270  and another member the drilling assembly  100  to seal the inside section of the housing  270  below the seal  284  from the outside environment, such as the drilling fluid. 
     Still referring to  FIGS.  1  and  2   , when a weight on the bit  147  is applied while the drill pipe  148  is substantially rotationally stationary, it will initiate a tilt of the housing  270  about the pin axis  212  of the pin  210 . The stabilizer  150  below the flexible device  120  initiates a bending moment in the deflection device  120  and also maintains the tilt when the drill pipe  148  and thus the drilling assembly  120  is substantially rotationally stationary (not rotating) and a weight on the drill bit  147  is applied during drilling of the curved borehole sections. Similarly, stabilizer  152  in addition to or without the stabilizer  150  also initiates the bending moment in the deflection device  120  and maintains the tilt during drilling of curved borehole sections. In one non-limiting embodiment, a dampening device or dampener  240  may be provided to reduce or control the rate of increase of the tilt when the drilling assembly  100  is rotated. In one non-limiting embodiment, the dampener  240  may include a piston  260  and a compensator  250  in fluid communication with the piston  260  via a line  260   a  to reduce or control the rate of the tilt. Applying a force F 1  on the housing  270  will cause the housing  270  and thus the lower section  290  to tilt about the pin axis  212 . Applying a force F 1 ′ opposite to the direction of force F 1  on the housing  270  causes the housing  270  and thus the drilling assembly  100  to straighten. The dampener may also be used to stabilize the straightened position of the housing  270  during rotation of the drilling assembly  100  from the surface. The operation of the dampening device  240  is described in more detail in reference to  FIGS.  6 A and  6 B . Any other suitable device, however, may be utilized to reduce or control the rate of the bend of the drilling assembly  100  about the pin  210 . 
     Referring now to  FIGS.  1 - 3   , when the drill pipe  148  is substantially rotationally stationary (not rotating) and a weight is applied on the drill bit  147 , the deflection device will initiate a tilt of the drilling assembly  100  at the pivot  210  about the pivot axis  212 . The rotating of the drill bit  147  by the downhole drive  140  will cause the drill bit  147  to initiate drilling of a curved section. As the drilling continues, the continuous weight applied on the drill bit  147  will continue to increase the tilt until the tilt reaches the maximum value defined by the inclined end stop  280 . Thus, in one aspect, a curved section may be drilled by including the pivot  210  in the drilling assembly  100  with a tilt defined by the inclined end stop  280 . If the dampening device  240  is included in the drilling assembly  100  as shown in  FIG.  2   , tilting the drilling assembly  100  about the pivot  210  will cause the housing  270  in section  290  to apply a force F 1  on the piston  260 , causing a fluid  261 , such as oil, to transfer from the piston  260  to the compensator  250  via a conduit or path  260   a . The flow of the fluid  261  from the piston  260  to the compensator  250  may be restricted to reduce or control the rate of increase of the tilt and avoid sudden tilting of the lower section  290 , as described in more detail in reference to  FIGS.  6 A and  6 B . In the particular illustrations of  FIGS.  1  and  2   , the drill bit  147  will drill a curved section upward. To drill a straight section after drilling the curved section, the drilling assembly  100  may be rotated 180 degrees to remove the tilt and then later rotated from the surface to drill the straight section. However, when the drilling assembly  100  is rotated, based on the positions of the stabilizers  150  and/or  152  and the well path, bending forces in the wellbore act on the housing  270  and exert forces in opposite direction to the direction of force F 1 , thereby straightening the housing  270  and thus the drilling assembly  100 , which allows the fluid  161  to flow from the compensator  250  to the piston  260  causing the piston to move outwards. Such fluid flow may not be restricted, which allows the housing  270  and thus the lower section  290  to straighten rapidly (without substantial delay). The outward movement of the piston  260  may be supported by a spring either positioned in force communication with the piston  260  or the compensator  250 . The straight end stop  282  restricts the movement of the member  270 , causing the lower section  290  to remain straight as long as the drilling assembly  100  is being rotated. Thus, the embodiment of the drilling assembly  100  shown in  FIGS.  1  and  2    provides a self-initiating tilt when the drilling assembly  120  is stationary (not rotated) or substantially stationary and straightens itself when the drilling assembly  100  is rotated. Although the downhole drive  140  shown in  FIG.  1    is shown to be a mud motor, any other suitable drive may be utilized to rotate the drill bit  147 .  FIG.  3    shows the drilling assembly  100  in the straight position, wherein the housing  270  rests against the straight end stop  282 . 
       FIG.  4    shows another non-limiting embodiment of a deflection device  420  that includes a force application device, such as a spring  450 , that continually exerts a radially outward force F 2  on the housing  270  of the lower section  290  to provide or initiate a tilt to the lower section  290 . In one embodiment, the spring  450  may be placed between the inside of the housing  270  and a housing  470  outside the transmission  143 . In this embodiment, the spring  450  causes the housing  270  to tilt radially outward about the pivot  210  up to the maximum bend defined by the inclined end stop  280 . When the drilling assembly  100  is stationary (not rotating) or substantially rotationally stationary, a weight on the drill bit  147  is applied and the drill bit is rotated by the downhole drive  140 , the drill bit  147  will initiate the drilling of a curved section. As drilling continues, the tilt increases to its maximum level defined by the inclined end stop  280 . To drill a straight section, the drilling assembly  100  is rotated from the surface, which causes the borehole to apply force F 3  on the housing  270 , compressing the spring  450  to straighten the drilling assembly  100 . When the spring  450  is compressed by application of force F 3 , the housing  270  relieves pressure on the piston  260 , which allows the fluid  261  from the compensator  250  to flow back to piston  260  without substantial delay as described in more detail in reference to  FIGS.  6 A and  6 B . 
       FIG.  5    shows a non-limiting embodiment of a hydraulic force application device  540  to initiate a selected tilt in the drilling assembly  100 . In one non-limiting embodiment, the device  540  includes a piston  560  and a compensation device or compensator  550 . The drilling assembly  100  also may include a dampening device or dampener, such as dampener  240  shown in  FIG.  2   . The dampening device  240  includes a piston  260  and a compensator  250  shown and described in reference to  FIG.  2   . The device  540  may be placed 180 degrees from device  240 . The piston  560  and compensator  550  are in hydraulic communication with each other. During drilling, a fluid  512   a , such as drilling mud, flows under pressure through the drilling assembly  100  and returns to the surface via an annulus between the drilling assembly  100  and the wellbore as shown by fluid  512   b . The pressure P 1  of the fluid  512   a  in the drilling assembly  100  is greater (typically 20-50 bars) than the pressure P 2  of the fluid  512   b  in the annulus. When fluid  512   a  flows through the drilling assembly  100 , pressure P 1  acts on the compensator  550  and correspondingly on the piston  560  while pressure P 2  acts on compensator  250  and correspondingly on piston  260 . Pressure P 1  being greater than pressure P 2  creates a differential pressure (P 1 -P 2 ) across the piston  560 , which pressure differential is sufficient to cause the piston  560  to move radially outward, which pushes the housing  270  outward to initiate a tilt. A restrictor  562  may be provided in the compensator  550  to reduce or control the rate of the tilt as described in more detail in reference to  FIGS.  6 A and  6 B . Thus, when the drill pipe  148  is substantially rotationally stationary (not rotating), the piston  560  slowly bleeds the hydraulic fluid  561  through the restrictor  562  until the full tilt angle is achieved. The restrictor  562  may be selected to create a high flow resistance to prevent rapid piston movement which may be present during tool face fluctuations of the drilling assembly to stabilize the tilt. The differential pressure piston force is always present during circulation of the mud and the restrictor  562  limits the rate of the tilt. When the drilling assembly  100  is rotated, bending moments on the housing  270  force the piston  560  to retract, which straightens the drilling assembly  100  and then maintains it straight as long as the drilling assembly  100  is rotated. The dampening rate of the dampening device  240  may be set to a higher value than the rate of the device  540  in order to stabilize the straightened position during rotation of the drilling assembly  100 . 
       FIGS.  6 A and  6 B  show certain details of the dampening device  600 , which is the same as device  240  in  FIGS.  2 ,  4  and  5   . Referring to  FIG.  2    and  FIGS.  6 A and  6 B , when the housing  270  applies force F 1  on the piston  660 , it moves a hydraulic fluid (such as oil) from a chamber  662  associated with the piston  660  to a chamber  652  associated with a compensator  620 , as shown by arrow  610 . A restrictor  611  restricts the flow of the fluid from the chamber  662  to chamber  652 , which increases the pressure between the piston  660  and the restrictor  611 , thereby restricting or controlling the rate of the tilt. As the hydraulic fluid flow continues through the restrictor  611 , the tilt continues to increase to the maximum level defined by the end inclination stop  280  shown and described in reference to  FIG.  2   . Thus, the restrictor  611  defines the rate of increase of the tilt. Referring to  FIG.  6 B , when force F 1  is released from the housing  270 , as shown by arrow F 4 , force F 5  on compensator  620  moves the fluid from chamber  652  back to the chamber  662  of piston  660  via a check valve  612 , bypassing the restrictor  611 , which enables the housing  270  to move to its straight position without substantial delay. A pressure relief valve  613  may be provided as a safety feature to avoid excessive pressure beyond the design specification of hydraulic elements. 
     Thus, in aspects, the drilling assemblies described herein include a deflection device that: (1) provides a tilt when the drilling assembly is not rotated and the drill bit is rotated by a downhole drive, such as a mud motor, to allow drilling of curved or articulated borehole sections; and (2) the tilt automatically straightens when the drilling assembly is rotated to allow drilling of straight borehole sections. In one non-limiting embodiment, a mechanical force application device may be provided to initiate the tilt. In another non-limiting embodiment a hydraulic device may be provided to initiate the tilt. A dampening device may be provided to aid in maintaining the tilt straight when the drilling assembly is rotated. A dampening device may also be provided to support the articulated position of the drilling assembly when rapid forces are exerted onto the tilt such as during tool face fluctuations. Additionally, a restrictor may be provided to reduce or control the rate of the tilt. Thus, in various aspects, the drilling assembly automatically articulates into a tilted or hinged position when the drilling assembly is not rotated and automatically attains a straight or substantially straight position when the drilling assembly is rotated. For the purpose of this disclosure, substantially rotationally stationary generally means the drilling assembly is not rotated by rotating the drill string  148  from the surface. The phrase “substantially rotationally stationary” and the term stationary are considered equivalent. Also, a “straight” section is intended to include a “substantially straight” section. 
     The foregoing disclosure is directed to the certain exemplary embodiments and methods. Various modifications will be apparent to those skilled in the art. It is intended that all such modifications within the scope of the appended claims be embraced by the foregoing disclosure. The words “comprising” and “comprises” as used in the claims are to be interpreted to mean “including but not limited to”.