Patent Publication Number: US-2022235617-A1

Title: Coiled tubing injector and method of controlling same

Description:
TECHNICAL FIELD 
     The present disclosure relates to the control of coiled tubing injectors for running coiled tubing into and out of a well in a hydrocarbon recovery operation. 
     BACKGROUND 
     Injection and production wells are commonly utilized in the recovery hydrocarbons from a hydrocarbon-bearing reservoir. 
     One method of recovering viscous hydrocarbons from a subterranean hydrocarbon-bearing formation using spaced horizontal wells is known as steam-assisted gravity drainage (SAGD). Various embodiments of the SAGD process are described in Canadian Patent No. 1,304,287 and corresponding U.S. Pat. No. 4,344,485. In the SAGD process, steam is injected through an upper, horizontal, injection well into a viscous hydrocarbon reservoir while hydrocarbons are produced from a lower, substantially parallel, horizontal, production well that is vertically spaced from and near the injection well. The injection and production wells are generally located close to the base of the hydrocarbon deposit to collect the hydrocarbons that flow toward the production well. 
     Coiled tubing is commonly run into and out of such wells utilizing a coiled tubing injector. For example, during a start-up phase of operation in SAGD, steam is generally injected through tubing strings extending through an injection well and a production well. Fluids are produced from both wells via the annulus of each well, around the respective tubing string. The steam is thus circulated to heat the viscous hydrocarbons, promoting flow of the hydrocarbons to develop fluid communication between the injection well and the production well. After sufficient heating of the hydrocarbons around the injection well and the production well, the start-up phase is discontinued. One or more tubing strings may be retracted from the well after start-up, for example, to reconfigure the well for production. 
     The removal of the coiled tubing from a well may present safety issues as the end of the coiled tubing exits the well and moves past the coiled tubing injector, leaving the free end uncontained. In such a case, the movement of the coiled tubing may be uncontrolled and the release of pressure unpredictable. 
     Improvements in retraction of coiled tubing from a well in a hydrocarbon bearing formation are desirable. 
     SUMMARY 
     According to an aspect of an embodiment, there is provided a coiled tubing injector for running coiled tubing into and out of a well in a hydrocarbon-bearing formation, includes a coiled tubing injector head including a base and a gripping mechanism configured to grip the coiled tubing running through the base and to advance and retract the coiled tubing, and a control system. The control system includes a coiled tubing indicator disposed between the gripping mechanism and a blowout preventer coupled to a head of the well, to indicate a change from presence of the coiled tubing to absence of the coiled tubing. The control system also includes a gripping mechanism control coupled to the coiled tubing indicator and operable to stop movement of gripping mechanism, thus discontinuing movement of the coiled tubing in response to the coiled tubing indicator indicating the change from the presence of the coiled tubing to the absence of the coiled tubing. 
     According to another aspect of an embodiment, there is provided a method of controlling a coiled tubing injector for running coiled tubing into and out of a well in a hydrocarbon-bearing formation. The method includes retracting the coiled tubing from the well utilizing a gripping mechanism of the coiled tubing injector, and, in response to an indication of a change from presence of coiled tubing to absence of coiled tubing at a coiled tubing indicator disposed between the gripping mechanism and a blowout preventer coupled to a head of the well, automatically discontinuing retracting the coiled tubing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will be described, by way of example, with reference to the drawings and to the following description, in which: 
         FIG. 1  is a schematic sectional view of a reservoir and shows the relative location of an injection well and a production well; 
         FIG. 2  is a sectional side view of a well pair including an injection well and a production well; 
         FIG. 3A  is a side view of a coiled tubing injector according to an embodiment; 
         FIG. 3B  is a side view of the coiled tubing injector of  FIG. 3A , with parts removed to show internal components thereof; 
         FIG. 4  is an enlarged portion of the coiled tubing injector of  FIG. 3A , showing an indicator arm in a first position; 
         FIG. 5  is the enlarged portion of the coiled tubing injector of  FIG. 4  with the indicator arm in a second position; 
         FIG. 6  is a flowchart showing a method of controlling a coiled tubing injector for running coiled tubing according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosure generally relates to a coiled tubing injector for running coiled tubing into and out of a well in a hydrocarbon-bearing formation, includes a coiled tubing injector head including a base and a gripping mechanism configured to grip the coiled tubing running through the base and to advance and retract the coiled tubing, and a control system. The control system includes a coiled tubing indicator disposed between the gripping mechanism and a blowout preventer coupled to a head of the well, to indicate a change from presence of the coiled tubing to absence of the coiled tubing. The control system also includes a gripping mechanism control coupled to the coiled tubing indicator and operable to stop movement of gripping mechanism, thus discontinuing movement of the coiled tubing in response to the coiled tubing indicator indicating the change from the presence of the coiled tubing to the absence of the coiled tubing. 
     For simplicity and clarity of illustration, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. Numerous details are set forth to provide an understanding of the examples described herein. The examples may be practiced without these details. In other instances, well-known methods, procedures, and components are not described in detail to avoid obscuring the examples described. The description is not to be considered as limited to the scope of the examples described herein. 
     Reference is made herein to an injection well and a production well. The injection well and the production well may be physically separate wells. Alternatively, the production well and the injection well may be housed, at least partially, in a single physical wellbore, for example, a multilateral well. The production well and the injection well may be functionally independent components that are hydraulically isolated from each other, and housed within a single physical wellbore. 
     The description below refers generally to wells utilized in SAGD. The coiled tubing injector and the method described herein are not limited to SAGD, however, as the coiled tubing injector and the method may be utilized in other operations in which a well is utilized. 
     In one example, a steam-assisted gravity drainage (SAGD) process may be utilized for mobilizing viscous hydrocarbons. In the SAGD process, a well pair, including a hydrocarbon production well and a steam injection well are utilized. An example of a well pair is illustrated in  FIG. 1  and  FIG. 2 . The hydrocarbon production well  100  includes a generally horizontal portion  102  that extends near the base or bottom  104  of the hydrocarbon reservoir  106 . An injection well  112  also includes a generally horizontal portion  114  that is disposed generally parallel to and is spaced vertically above the horizontal portion  102  of the hydrocarbon production well  100 . 
     During a production phase of SAGD, steam is injected through the injection well head  116  and through the steam injection well  112  to mobilize the hydrocarbons and create a steam chamber  108  in the reservoir  106 , around and above the generally horizontal portion  114 . 
     Viscous hydrocarbons in the reservoir  106  are heated and mobilized and the mobilized hydrocarbons drain under the effects of gravity. Fluids, including the mobilized hydrocarbons along with condensate, are collected in the generally horizontal portion  102  and are recovered via the hydrocarbon production well  100 . Production may be carried out for any suitable period of time. 
     As indicated above, the description generally refers to SAGD herein. The coiled tubing injector and the method described herein are not limited to SAGD, however. Coiled tubing (CT) has many applications and has been widely applied in the petroleum industry, including, for example, in drilling (CT drilling), cementing, wellbore cleanout, acidizing, sand control, testing, logging, workovers, and hydraulic fracturing. Thus, the injector and the method described herein are also applicable to other operations. SAGD is referred to for the purpose of providing one particular example of the use of the injector and method of controlling the coiled tubing injector. 
     A coiled tubing injector may be utilized to run coiled tubing into and out of a well, for example, for use in running instruments, shift tools, or other equipment downhole or for pump stimulation or other fluids. A coiled tubing injector may be utilized during workover of the injection well  112  or the production well  100 . In a particular example, a workover is performed between a start-up phase of a SAGD operation and a production phase of the SAGD operation. 
     During the start-up phase of operation in SAGD, steam is generally injected through tubing strings that extend through the injection well  112  and through the production well  100 , respectively. Fluids are produced from both wells via the annulus of each well, around the respective tubing string. The fluids that are produced are primarily steam, although some small amount of hydrocarbons may be present. The steam is thus circulated to heat the viscous hydrocarbons, promoting flow of the hydrocarbons to develop fluid communication between the injection well  112  and the production well  100 . 
     After sufficient heating of the hydrocarbons around the injection well  112  and the production well  100 , the start-up phase is discontinued. A workover is performed to reconfigure the wells for the production phase of the operation, in particular, for injection of steam via the injection well and production of fluids via the production well. The workover is performed to change, add, or remove equipment and may include retraction of coiled tubing in one or both of the injection well  112  and the production well  100 . 
     Before the production phase, the coiled tubing string extending through the production well  100 , for example, is utilized to run monitoring instruments into the well. The coiled tubing string that is utilized to run monitoring instruments or for other equipment, may later be removed. 
     Removal of the coiled tubing, however, presents risks, particularly in the event that the coiled tubing exits the injector, resulting in uncontrolled “whipping” of the coiled tubing. The coiled tubing that comes out of the injector poses a physical hazard as the uncontrolled movement may cause the coiled tubing to hit and injure nearby workers. 
     In addition, the pressure in the reservoir  106  and into the production well  100  may be in the range of, for example, about 2500 kPa to about 3200 kPa. In addition, to steam, hydrogen sulfide as well as vapours from lighter hydrocarbons may enter the well, exiting at the wellhead and posing a danger while work is performed on the well. These vapours pose a risk to workers near the production well head  118  when the well head is open. With an increase in the use of solvents in hydrocarbon recovery processes, these vapors are more likely to enter the wellbore, escape to the atmosphere, and pose risk to workers. 
     Referring to  FIG. 3A  and  FIG. 3B , a coiled tubing injector  300  according to one embodiment is illustrated. The coiled tubing injector  300  includes a coiled tubing injector head  302  that includes a frame  304 . The frame  304  is mounted above a wellhead, such as the production well head  118  or the injection well head  116  to support and to inject the coiled tubing into the well or to retract coiled tubing from the well. The frame  304  includes a base  306  that is supported above blowout preventers  308  in a stack on the wellhead. The frame  304  also includes frame members  310  that are connected to the base  306  and that, together provide the frame in which components of the coiled tubing injector head  302  are housed or mounted. 
     The coiled tubing injector head  302  includes a gripping mechanism  310  that includes a pair of opposing endless chains  312  with links of the chains  312  coupled to gripper blocks  314  that act on opposing sides of the coiled tubing by applying force on diametrically opposite sides of the coiled tubing. The gripping mechanism  310  also includes hydraulic motors  316 . Each of the hydraulic motors  316  is coupled to a respective one of the endless chains  312  to drive the chains  312  forward or backward, thus injecting or retracting the coiled tubing. 
     The coiled tubing injector head  302  may include other elements, for example, to adjust the spacing between the gripper blocks  314  and thus adjust the force applied to the coiled tubing. 
     The coiled tubing injector  300  also includes a goose neck  320  coupled to the coiled tubing injector head  302 . The goose neck  320  directs the coiled tubing from a coiled tubing reel, into the coiled tubing injector head  302 . The coiled tubing is then directed through the gripping mechanism  310  and downwardly to the well. 
     The coiled tubing injector  300  also includes a control system  324  utilized to control the hydraulic motors  316 . The control system  324  includes a coiled tubing indicator  326  disposed between the gripping mechanism  310  and the blowout preventers  308 . The control system  324  is utilized to indicate a change from presence of the coiled tubing to absence of the coiled tubing. In the present example, the coiled tubing indicator  326  is disposed between the gripping mechanism  310  and a coiled tubing stripper  322 , near the base  306 . 
     The control system also includes a gripping mechanism control  328  that is connected to the coiled tubing indicator  326  and to the hydraulic motors  316  to control the hydraulic motors  316  to stop movement of gripping mechanism  310 , thus discontinuing movement of the coiled tubing in response to the coiled tubing indicator  326  indicating the change from the presence of the coiled tubing to the absence of the coiled tubing. 
     Reference is made to  FIG. 4  to describe the coiled tubing indicator  326  according to one embodiment. As illustrated in  FIG. 4 , the coiled tubing indicator  326  includes a support structure  402  that is mounted on the base  306  of the frame  304 . The support structure  402  may be a frame or may be a solid structure mounted on the base  306 , below the gripping mechanism  310 . In the present example, the support structure  402  is a solid structure including sides  404 , a top  406 , and a bottom  408  that is fixed to the base  306 . The support structure  402  in this example includes a chamfered edge  410  between the top  406  and the one of the sides  404  that is closest to the coiled tubing  412 . 
     An indicator arm  414  is coupled to the support structure  402  by a yoke mount  416 . The indicator arm  414  is a rectangular member that includes a first end  418  and an opposing second end  420 . 
     One end of the yoke mount  416  is fixed to the one of the sides  404  of the support structure  402  that is closest to the coiled tubing  412 . The yoke mount  416  extends away from the support structure  402  and couples to the indicator arm  414  by a hinge pin  424  that extends through the indicator arm  414  and couples to arms  426  of the yoke mount  416 . The indicator arm  414  is moveable relative to the arms  426  of the yoke mount  416  by rotation about the hinge pin  414 . 
     A roller  428  is rotatably coupled to the indicator arm  414 , near the first end  418  of the indicator arm  414 . The roller  428  is rotatable relative to the indicator arm  414 . The roller  428  is biased away from the support structure  402  and into contact with the coiled tubing  412  by a biasing mechanism  430  that acts on the indicator arm  414 . The biasing mechanism  430  in the present example comprises a spring coupled at one end to the support structure  402  and coupled at the opposing end to the indicator arm  414 . Thus, in this example, the biasing mechanism acts on the indicator arm  414 , on an opposite side of the yoke mount, to bias the second end  420  toward the support structure  402  and thus bias the roller  428  toward the coiled tubing  412 . 
     A switch  432  is mounted on the support structure  402 , on or near the chamfered edge  410 . The switch  432  is located such that the switch  432  is actuatable by the indicator arm  414  when the coiled tubing  412  is absent and therefore not acting against the roller  428 . Thus, when the coiled tubing  412  is absent, the indicator arm  414  moves, as a result of the bias from the biasing mechanism  430 , from the position show in  FIG. 4  in which the roller  428  abuts the coiled tubing  412 , to the position shown in  FIG. 5  in which the indicator arm  414  actuates the switch  432 . 
     Referring again to  FIG. 3A  and  FIG. 3B , in addition to  FIG. 4  and  FIG. 5 , the switch  432  is connected to a controller  330  that together are part of the gripping mechanism control  328 . The controller  330  is connected to the hydraulic motors  316 . The switch  432  may be connected by wired connection to the controller  330  or by a wireless connection, to communicate with the controller  330  when the switch  432  is actuated. The controller  330  causes the hydraulic motors of the gripping mechanism to discontinue movement of the coiled tubing when the switch  432  is actuated. Thus, in response to the coiled tubing indicator  326  indicating the change from the presence of the coiled tubing to the absence of the coiled tubing, the gripping mechanism controller  328  discontinues movement of the coiled tubing to inhibit the coiled tubing from exiting the gripping mechanism  310 . 
     The controller  330  may also include a control panel or device connected thereto and that is controllable by an operator to control the operation of the hydraulic motors  316  and the gripping mechanism  310 . 
     Reference is now made to  FIG. 6  to describe a method of controlling a coiled tubing injector for running coiled tubing into and out of a well in a hydrocarbon-bearing formation. The method may contain additional subprocesses other than that shown or described. 
     The coiled tubing injector  300  is utilized to retract coiled tubing in the well at  600 . The coiled tubing injector  300  is controlled by controlling the hydraulic motors  316  to retract the coiled tubing. 
     In response to the indicator indicating that the coiled tubing is present at the coiled tubing indicator  326  at  604 , the method continues at  602  and retraction of the coiled tubing continues. In response to the indicator indicating that the coiled tubing is absent at the coiled tubing indicator  326  at  604 , the method continues at  606  and retraction of the coiled tubing is discontinued. The indicator indicates that the coiled tubing is absent as the indicator arm  414  moves to the second position shown in  FIG. 5 . The switch  432  is actuated by the indicator arm  414  and sends a signal to the controller  330  as the indicator arm  414  moves to the second position. In turn, the controller  330  stops the hydraulic motors  316 , thus stopping the gripping mechanism and stopping retraction of the coiled tubing. 
     In the above-described embodiment, the coiled tubing indicator  326  is coupled to the base  306 , above the coiled tubing stripper  322  and below the gripping mechanism  310 . Alternatively, the coiled tubing indicator  326  may be disposed below the coiled tubing stripper, and above the blowout preventers  308 , such that the coiled tubing indicator  326  is located within a pressure contained region above the wellhead. By including a coiled tubing indicator  326  in the pressure contained region, the coiled tubing indicator  326  is positioned to indicate the change from the presence of the coiled tubing to the absence of coiled tubing prior to withdrawal of the coiled tubing from the pressure containment. 
     In addition, in the above-described embodiment, the coiled tubing indicator is a mechanical indicator. The mechanical indicator may take other forms than that specifically described. In addition, other devices or indicators may be utilized to sense the end of the coiled tubing. 
     Advantageously, the control system is utilized to automatically detect the end of the coiled tubing by detecting that there is no longer coiled tubing at the coiled tubing indicator, and to stop the hydraulic motors, thereby stopping retraction of the coiled tubing. By automating the detection and stopping of the retraction, there is less chance of the coiled tubing becoming completely removed from the gripping mechanism and resulting in uncontrolled release of the coiled tubing from the gripping mechanism. Thus, the end of the coiled tubing remains controlled. In addition, the continued control of the end of the tubing provides for improved safety for the operators. 
     The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole. All changes that come with meaning and range of equivalency of the claims are to be embraced within their scope.