Patent Publication Number: US-2021172283-A1

Title: A device for forming a barrier in an annulus of a well

Description:
INTRODUCTION 
     The present invention relates to a device for forming a barrier in an annulus of a well, such as a hydrocarbon or water injector well. The device comprises an injection tool adapted to introduce a polymeric hardening liquid in through an opening in the annulus, and a pump unit adapted to provide pressure to said liquid so that the liquid is introduced into the opening in the annulus with a controllable pressure. 
     The present invention further relates to an arrangement and a method for forming a barrier in an annulus of a well. 
     PRIOR ART 
     In various situations, an annulus of a well needs to be remedially repaired in order to provide the required and necessary annulus sealing capabilities. The annulus of the well is located between two pieces of pipes, tubing-casings or casing to casing. The annulus can also be between the said tubing/casing and the wellbore formation. The purpose of the casings are for example to isolate different zones of the well, or to function as a well barrier to the surface. 
     In prior art, the annulus isolation are formed by either cement, another sealing material or by a mechanical packer being part of the initial well completion. A challenge with a cemented annulus is that it can leak water or hydrocarbons in between the zones, or to the surface via the cemented annulus. Prior art devices for repairing a leaking cemented barrier is called a cement squeeze and comprising a method where cement is squeezed into the annulus to repair the failed barrier. To repair a leaking packer is by traditional means not possible. 
     Prior art method of forming barriers by means of a polymeric hardening liquid, such as various types of resins are known. However, it has also proven to be difficult to form barriers using such resins with high reliability. 
     WO2010/147476A1 discloses a well tool and a method for forming a barrier in a well using a resin. 
     SUMMARY OF THE INVENTION 
     The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art. The object is achieved through features, which are specified in the description below and in the claims that follow. 
     The object of the invention is to provide an improved device for forming a barrier in an annulus of a well. In particular, an object of the invention is to provide a device that enables a barrier to be formed in an annulus of a well subjected to a differential pressure with improved reliability. 
     This object is provided by means of a device for forming a barrier in an annulus of a well according to the invention. The device comprises
         an injection tool adapted to introduce a polymeric hardening liquid in through an opening in the annulus, and   a pump unit adapted to provide pressure to said liquid so that the liquid is introduced into the opening in the annulus with a controllable pressure.       

     The device is characterized in that it comprises a control unit adapted to control the pump unit so that said liquid is provided into the opening with an initial pressure at a start up phase of introducing the liquid into the opening and a final pressure at a close-down phase of introducing the liquid into the opening, wherein the final pressure is higher than the initial pressure. 
     The injection tool is configured to introduce a polymeric hardening liquid in through the opening in the annulus when forming the barrier. The pump unit is adapted to provide pressure to the liquid so that the liquid is introduced in through the opening with a pressure. The control unit is adapted to control the pressure in which the pump unit introduces the liquid in through the opening in the annulus. 
     By means of introducing the polymeric hardening liquid in through the opening in the annulus during a period of time in which the pressure of introducing the liquid from the start up phase to the close-down phase is increased, the quality of the formed barrier is improved. The polymeric hardening liquid relates to a polymeric based liquid that is hardening with time, i.e. the viscosity of the hardening liquid increases from a pumpable liquid to a none pumpable paste, and being a solid at the final stage. 
     It is believed that by introducing the liquid at a low pressure at the start-up phase when the liquid has low viscosity, and subsequently introducing the liquid at a high pressure at the close-down phase when the liquid has a high viscosity, allows the liquid to first penetrate into the larger cracks of the annulus, and thereafter fill up the smaller volume of the cracks, whereby a barrier of high quality is formed. The “low” and “high” in the previous sentence is to be regarded as relative terms. The viscosity is lower at the start-up phase than at the close-down phase as the liquid is hardening with time. The pressure is lower at the start-up phase than at the close-down phase. 
     According to an embodiment of the invention, the control unit is adapted to control the pump unit so that said liquid is provided into the opening with a gradual increasing pressure over time from the start up phase to the close-down phase of introducing the liquid to the opening in the annulus. 
     The device is in particular preferably for forming a barrier in an annulus comprising a cement material. However, it shall be understood that the device may be applied to an annulus filed with other types of solids. 
     According to an embodiment of the invention, the initial pressure is between 1-50 bar, preferably between 10-30 bar. 
     According to an embodiment of the invention, the final pressure is between 2-400 bar, preferably between 30-250 bar. 
     According to an embodiment of the invention, the control unit adapted to control the pump unit between the start up phase and the close-down phase of introducing the liquid to the opening at a time period between one hour and 72 hours, preferably between 12 and 48 hours. 
     According to an embodiment of the invention, the device further comprises a device for forming said opening in the annulus. The device for forming said opening comprises for example a perforation unit or a drill unit. 
     According to an embodiment of the invention, the control unit adapted to control the pump unit so that said liquid is provided into the opening in the annulus with two or more injection sequences with increasing pressure. 
     The object of the invention is further obtained by means of an arrangement for forming a barrier in a concrete annulus of a well. The arrangement comprises the device according to any of above embodiments and a polymeric hardening liquid. 
     According to an embodiment of the invention, said liquid has a viscosity between 5-1*10{circumflex over ( )}6 cP at the start up phase of introducing the liquid to the opening, preferably a viscosity of between 15 20000 cP. 
     According to an embodiment of the invention, said liquid has a viscosity between 1*10{circumflex over ( )}6-10*10{circumflex over ( )}6 cP at the close down phase of introducing the liquid to the opening, preferably between 2*10{circumflex over ( )}6-5*10{circumflex over ( )}6 cP. 
     According to an embodiment of the invention, said liquid mainly comprises a thermoset material. 
     The object of the invention is further obtained by means of a method for forming a barrier in a concrete annulus of a well. The method comprises:
         positioning an injection tool at a position of an opening in the annulus for introducing a polymeric hardening liquid,   at a start up phase, introducing the liquid into the opening at a initial pressure, and   at a close-down phase, introducing the liquid into the opening at a final pressure, wherein the final pressure is higher than the initial pressure.       

     According to an embodiment of the invention, the method comprises:
         gradual increasing pressure over time from the start up phase to the close-down phase of introducing the liquid into the opening in the annulus.       

     According to an embodiment of the invention, the initial pressure is between 1-50 bar, preferably between 10-30 bar. 
     According to an embodiment of the invention, the final pressure is between 2-400 bar, preferably between 30-250 bar. 
     According to an embodiment of the invention, a time period between the start up phase and the close-down phase of introducing the liquid to the opening is between one hour and 72 hours, preferably between 12 and 48 hours. 
     According to an embodiment of the invention, the method comprises providing said liquid into the opening in the annulus with two or more injection sequences with increasing pressure. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       In the following is described examples of preferred embodiments illustrated in the accompanying drawings, wherein: 
         FIG. 1  discloses a schematic view of device for forming a barrier in an annulus of a well according to an embodiment of the invention; 
         FIG. 2  discloses a schematic view of a well comprising an annulus to be provide with a barrier by means of the device in  FIG. 1 ; 
         FIG. 3  discloses a flow chart of a method for forming a barrier in an annulus of a well according to an embodiment of the invention; 
         FIG. 4  discloses a flow chart of a method for forming a barrier in an annulus of a well according to a further embodiment of the invention; and 
         FIG. 5  discloses a flow chart of a method for forming a barrier in an annulus of a well according to yet another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1  is a schematic view of device  1  for forming a barrier in an annulus  5  of a well according to an embodiment of the invention disclosed.  FIG. 1  also discloses an arrangement  10  comprising the device  1  configured with a polymeric hardening liquid. 
     The device  1  comprises an elongated structure to be inserted in the well  11 , such as a hydrocarbon or water injector well. 
     In  FIG. 2  is a schematic view of a well  11  comprising the annulus  5  to be provided with a barrier by means of the device  1  in  FIG. 1 . The well  11  comprises a well head  12  and a first casing  14  and second casing  16  concentric between which an annulus  5  is formed that has been filled with a solid, such a solid comprising a cement material or other suitable material. The device  1  is adapted to be introduced into the well  11 . 
     For example, in  FIG. 2 , a part of the annulus  5  is filled with a good cement column, another part of the annulus  5  is filled with poor cement column, and yet another part of the annulus  5  is without filling. The annulus  5  is to be provided with one or several barriers by means of the device  1  in  FIG. 1 . 
     The device  1  comprises an injection tool  20 , a device  22  for forming the opening into the annulus  5 , a reservoir  24  for containing the polymeric hardening liquid and a pump unit  26 . 
     The device  22  for forming the opening in the annulus  5  comprises for example a drill unit comprising a drive unit and a drill bit for drilling through the first casing  14  and into the annulus  5 . The device  22  for forming the opening in the annulus  5  comprises alternatively a perforation unit. 
     The injection tool  20  is adapted to introduce the polymeric hardening liquid in through an opening in the annulus  5 . The injection tool  20  comprises an outlet adapted to be aligned with the opening in the annulus  5  for providing the liquid into the opening. 
     The pump unit  26  is configured to provide pressure to the liquid so that the liquid is introduced into the opening in the annulus  5  with a controllable pressure. The pump unit  26  comprises for example a hydraulic induced pump or an electric induced pump. 
     The device  1  further comprises a control unit  30  adapted to control the pump unit  26  and accordingly the pressure in which the liquid is introduced into the opening in the annulus  5 . The control unit  30  adapted to control the pump unit  26  so that said liquid is provided into the opening with an initial pressure at a start up phase of introducing the liquid into the opening and a final pressure at a close-down phase of introducing the liquid into the opening. The final pressure is higher than the initial pressure. Accordingly, the control unit  30  is adapted to control the pump unit  26  so that the liquid is introduced at a low pressure when the liquid has a low viscosity at the start-up phase of forming the barrier and at a high pressure when the liquid has a high viscosity at the close-down phase when forming the barrier. The “low” and “high” in the previous sentence is to be regarded as relative terms for the purpose of explaining the invention. Details on parameters for forming will be explained in connection with the explanation of the method. 
     The control unit  30  comprises a logic unit, such as a CPU, adapted to execute a computer program, and signalling means connected to the pump unit  26  for controlling the pressure of introducing the liquid into the opening in the annulus  5 . It shall be understood that the control unit  30  comprises the necessary features for controlling the pressure of introducing the liquid into the opening in the annulus  5  during a period of time of forming the barrier. 
     In the disclosed embodiment in  FIG. 1 , the device  1  comprises the control unit  30  and further control means  31  for controlling the control unit  30  from the surface. The further control means  31  is for example a computer unit comprising a CPU adapted to execute a computer program. The further control means  31  is connected to the control unit  30 , which in the disclosed embodiment is located in vicinity of the pump unit  26 . 
     Preferably, the polymeric hardening liquid comprise mainly a thermoset material. The liquid has preferably the characteristic in form a viscosity between 5-2000 cP at the start up phase of introducing the liquid to the opening, preferably a viscosity of between 15-1*10{circumflex over ( )}6 cP. Furthermore, the liquid has preferably the characteristic in form a viscosity between 1*10{circumflex over ( )}6-10*10{circumflex over ( )}6 cP at the close down phase of introducing the liquid to the opening, preferably between 2*10{circumflex over ( )}6-5*10{circumflex over ( )}6 cP. 
     The invention will now be explain in view of a method for forming a barrier in an annulus  5  of a well  11 . It shall be understood that the control unit  30  of above discussed device  1  is configured to control the device  1  accordingly. 
     In  FIG. 3  is a flow chart of a method for forming a barrier in an annulus  5  of a well  11  according to an embodiment of the invention disclosed. 
     The method comprises, in a step  110 , positioning an injection tool  20  at a position of an opening in in the annulus  5  for introducing the polymeric hardening liquid. 
     In a step  120 , the method comprises, at a start-up phase, introducing the liquid into the opening at an initial pressure. Subsequently, in a step  130 , the method comprises, at a close-down phase, introducing the liquid into the opening at a final pressure, wherein the final pressure is higher than the initial pressure. 
     According to a preferred embodiment, the method comprises introducing the liquid into the opening at the initial pressure between 1-50 bar, preferably between 10-30 bar. 
     According to a preferred embodiment, the method comprises introducing the liquid into the opening at the final pressure is between 2-400 bar, preferably between 30-250 bar. 
     According to a preferred embodiment, the duration between the start up phase and the close-down phase of introducing the liquid to the opening is between one hour and 72 hours, preferably between 12 and 48 hours. 
     In  FIG. 4  is a flow chart of a method for forming a barrier in an annulus  5  of a well  11  according to a further embodiment of the invention disclosed. The method in  FIG. 4  differs from the method in  FIG. 3  in that the method further comprises, in a step  125 , gradually increasing the pressure of the liquid over time from the start up phase to the close-down phase of introducing the liquid into the opening. 
     In  FIG. 5  is a flow chart of a method for forming a barrier in an annulus  5  of a well  11  according to yet another embodiment of the invention disclosed. The method in  FIG. 5  differs from the method in  FIG. 3  in that the method further comprises, in a step  127 , providing said liquid into the opening in the annulus  5  with two or more injection sequences with increasing pressure. 
     It shall be understood that the method in  FIG. 3-5  may also involve the step of forming the opening into the annulus  5  if the opening into the annulus  5  has not yet been established. 
     It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb “comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.