Abstract:
Remote cement plugging device ( 10 ) and method of use. The device has at least one means ( 60 ) for perforating at least one hole through a wall of a first well casing, and means to inject cement into an annulus between the inner well casing and a second well casing. The perforating means has at least one punch ( 65 ) actuated by compressed fluid (hydraulic, pneumatic) to form the hole(s), and thereafter the cement is delivered to the annulus between the inner and outer/intermediate casings to form the cement plug without the need to withdraw the device from the well casing.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to the plugging of hydrocarbon wells, particularly subsea hydrocarbon wells, when barriers must be maintained between the hydrocarbon formation and the surface to prevent hydrocarbon contamination by leakage from the well. 
       BACKGROUND OF THE INVENTION 
       [0002]    In the field of subsea oil and gas production there are regulations that require barriers to be maintained between the oil and/or gas formation and the surface. 
         [0003]    During abandonment of subsea wells the barrier system must be maintained to ensure that any residual oil or gas in the formation does not dissipate from the well leading to a potential pollution event, with the associated environmental and social impact. 
         [0004]    Barrier systems for offshore wells consist of active and passive systems, with the passive systems a physical barrier is maintained between the formation and the seabed. Active systems are designed then in the case of an emergency or in unforeseen circumstance the active system deploys to provide a barrier between the formation and the seabed. 
         [0005]    When abandoning an offshore well the use of active systems to maintain the barriers between the seabed and the formation is not suitable as there will be no ongoing maintenance of the barrier. Further during removal of the well head of the subsea well one of the barriers covering the annulus between the inner casing and the first intermediate casing is removed and needs to be replaced prior to severing the well head. 
         [0006]    One way of maintaining the barriers during abandonment of a subsea well is the use of cement. A cement plug is cast into the central casing and cement is injected into the annulus between the central casing and the first intermediate casing. To pump the cement into the annulus it is first necessary to provide a pathway for the cement to travel from the central casing into to the annulus. This is usually done by the use of explosives to puncture holes in the central casing through to the annulus. 
         [0007]    When a subsea well is abandoned the use of a jack up oil rig, work barge or semi submersible has traditionally been used. With the use of these types of vessel, the production of holes in the casing through to the annulus is usually by the use of explosives. There are several issues with the use of explosives not least of which is the safety aspects. Further a large stable platform must be provided so that explosives can be safely handled. 
         [0008]    The existing methods for subsea intervention and abandonment of wells have some inherent disadvantages including the use of large vessels so that explosives can be used, these vessels tend to be slow moving, take a relatively long time to reach offshore oil and gas fields and are expensive to operate while on station. 
         [0009]    In order to alleviate problems of the cost and time taken to get a large work platform on a station, the use of a work boat is desired. Problems with using a work boat arise when using explosives, so alternative methods and means of providing holes in the casing and injecting cement are required. 
         [0010]    The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement of any form of admission that the prior art forms part of the common general knowledge in Australia. 
       SUMMARY OF THE INVENTION 
       [0011]    With the aforementioned in mind, in one aspect the present invention provides a device for oil field operations including means for perforating holes in a wall of a first well casing and means for injecting sealant into an annulus between the first well casing and a second well casing, 
         [0012]    including at least one punch assembly, a cutting tool the cutting tool being designed to produce a hole in the casing and a sealant delivery means. 
         [0013]    wherein the tool is able to perforate the holes and deliver sealant to the annulus without the need to withdraw the tool from the well casing. 
         [0014]    A further aspect of the present invention provides a remote plugging device for well operations, including at least one perforating means for perforating at least one hole through one or more well casings, and sealant injection means to inject sealant between at least one of said one or more well casings and at least another of said well casings or a further well casing, 
         [0015]    wherein the perforating means includes at least one punch actuated by pressurised fluid to perforate the at least one the hole, and thereafter the sealant is delivered to the annulus to form the sealant plug without the need to withdraw the device from the well casing. 
         [0016]    In another preferred embodiment the device and ancillary equipment is adapted for deployment from a work boat for use in subsea applications. 
         [0017]    Another aspect of the present invention provides a remote plugging device for well operations, including at least one perforating means for perforating at least one hole through a wall of a first well casing, and injection means to inject a sealant into an annulus between the first well casing and a second well casing, 
         [0018]    wherein the perforating means includes at least one punch actuated by compressed fluid to perforate the at least one the hole, and thereafter the sealant is delivered to the annulus to form the sealant plug without the need to withdraw the device from the well casing. 
         [0019]    Preferably the sealant is cement based, or may be a none setting medium such as drilling mud. 
         [0020]    Actuation of the punch(s) by compressed fluid advantageously avoids the need for explosive charges to effect perforation. 
         [0021]    The at least one punch may be actuated by hydraulic or pneumatic pressure. 
         [0022]    The at least one punch may be extended or retracted by at least one double acting hydraulic or pneumatic piston, which provides positive actuation and retraction to assist in ensuring that the perforator(s) is/are retracted so that the sealant can flow through the perforation(s). Alternatively, the at least one punch may be extended by hydraulic or pneumatic pressure and retracted by at least one resilient biasing means, which simplifies the means of return actuation, such as by return spring(s). 
         [0023]    Preferably there may be one or more outlet/ports for sealant flow provided adjacent at least one of said at least one perforation means. This helps to ensure that sealant flow readily reaches the perforation(s) and reduces the overall amount of cement required. 
         [0024]    At least one packer assembly may be provided, whereby, when the packer assembly or assemblies is/are expanded to hold the device by pressure inside the well casing e.g. by pressure against an interior wall of the inner casing of the well. Such packers may be energized by hydraulic or pneumatic pressure. 
         [0025]    Alternatively or in addition, packers may be provided which are self energizing. These may expand as a result of initial pressure from a pressurized fluid supply line (e.g. from the surface) or from hydrocarbon escaping through at least one hole made by the device. The applied pressure causes the packers to seal the device within the bore prior to the sealant being pumped into the hole(s). 
         [0026]    The device may include at least one fluid pressure accumulator, preferably hydraulic or pneumatic accumulator(s), within or proximate to a leading nose end of the device, the accumulator providing fluid pressure to the at least one packer assembly in the event of a failure of the device. Fluid pressure may be supplied from the hydraulic or pneumatic supply used to actuate the perforation means. 
         [0027]    At least two of the perforation means may be spaced apart such that the distance between a first punch of a first perforation means and a first punch of a second perforation means is greater than a length of coupling members used to couple together lengths of well casing. 
         [0028]    One or more of the punches may have a breakaway shaft such that in the event of the punch being jammed in the perforated hole, the piston and base of the punch can be positively retracted and a working end of the punch sheared off. 
         [0029]    At least one of the punches may be retained to the piston by a quick release means, such as by a quick release ring, clip or other retainer. 
         [0030]    At least one resilient packer may be provided which absorbs shock induced on the respective punch during perforation of the casing. Silicon rubber, rubber, nitrile, or the like, or combinations thereof may be used. 
         [0031]    The perforating means may be adapted to perforate consecutive holes through multiple casing walls, one after the other. That is, where the well has multiple casings one within another, the perforator may, for example, perforate a hole through more than one casing to set a sealant (e.g. cement) plug between the first and/or second and third concentric casings. 
         [0032]    A further aspect of the present invention provides a method of sealing a well riser, including the steps of; 
         [0033]    a) inserting a remote plugging device into a riser; 
         [0034]    b) supplying compressed fluid to the plugging device; 
         [0035]    c) perforating at least one hole through at least a first well casing using at least one respective punch actuated by the compressed fluid; and 
         [0036]    d) pumping a sealant through said at least one hole into an annulus between the at least one first casing and a second or intermediate casing to form a plug seal. 
         [0037]    The method may further include the steps of perforating one or more holes with a respective at least one punch, and leaving at least one said punch extended to act as an anchor for the device. Thus, one or more punches may remain unretracted to anchor the device. There can be significant hydrocarbon pressure on the device when a hole is perforated through the casing, and the unretracted punch(es) may act as a secondary lock to hold the device in place. Also, in the event that the device needs to be abandoned within the well for any reason, this anchoring arrangement can assist in maintaining the device in place. An accumulator may be employed to provide sufficient pressure to maintain the at least one punch extended. A one way or check valve may be employed to prevent pressure loss once the hydraulic or pneumatic feed is removed from the device. 
         [0038]    The method may include withdrawing the at least one punch from at least one respective hole. However, it is envisaged that the device may pump fluid around, through, or a combination thereof, the at least one punch; Hydraulic fluid may be used to actuate the punch(s). Preferably the sealant contains cement. 
         [0039]    Retraction of the at least one punch may be by hydraulic or pneumatic pressure. Alternatively, extending the at least one punch may be by hydraulic or pneumatic pressure and retraction by resilient biasing means. 
         [0040]    Perforating said at least one hole may be through a multiplicity of well casing walls, and injecting the sealant into the annulus between at least one of said multiplicity of walls and a further casing wall. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0041]      FIG. 1  shows an overview of an embodiment of the device. 
           [0042]      FIG. 2  shows a section of the entry nose and lower packer assembly of the embodiment shown in  FIG. 1 . 
           [0043]      FIG. 3  shows a section of hydraulic punch assembly of the embodiment shown in  FIG. 1 . 
           [0044]      FIG. 4  shows the lower perforation tool of  FIG. 1  in more detail. 
           [0045]      FIG. 5  shows an alternative embodiment of the device. 
           [0046]      FIG. 6   a  shows a sectional view of an alternative embodiment of the device including spring return hydraulic pistons. 
           [0047]      FIG. 6   b  shows a perspective view of the complete device of  FIG. 6   a.    
           [0048]      FIG. 7   a  is a perspective view of a perforation assembly of an embodiment of the present invention. 
           [0049]      FIG. 7   b  is a sectional view of the embodiment shown in  FIG. 7   a.    
       
    
    
     DETAILED DESCRIPTION 
       [0050]    The invention will now be described with reference to the accompanying figures. Referring first to  FIG. 1  that shows an overview of the remote plugging device herein after referred to as the “tool”. Whilst cement is referred to hereinafter as the sealant, it will be appreciated that other sealants may be employed, such as drilling mud. 
         [0051]    The construction of the tool  10  is based on modular construction methods so that individual components can be replaced if they are damaged during an offshore campaign. Other possible arrangement of the components are possible provide that they allow for the operation of the tool  10  such that the casing is perforated and cement is injected into the annulus. Only a typical example is described in the following detailed description. 
         [0052]    The overall layout of the tool  10  includes of an entry nose  20  at a leading end  25 , designed to allow the cement injection tool  10  to be inserted into a subsea well. The entry nose  20  is connected to a lower packer mandrel  30  that has a packer assembly  40  fitted. This packer assembly  40  is designed so that when the tool  10  is inserted into the inner casing of the subsea well, the packer assembly  40  can expand and hold the tool  10  in place and seal the tool  10  in the casing. The lower packer mandrel  30  is connected to a hydraulic module  50  at the hydraulic module first end  52 . 
         [0053]    The hydraulic module  50  consists of a number of punch assemblies  60  with punches  65 . The punch assemblies  60  are arranged circumferentially around the hydraulic module  50  and are designed so that they can punch holes in the inner casing. It will however be appreciated that at least one said punch may be used to perforate through more than one casing wall, such that sealant can be pumped into the annulus or cavity between further casings e.g., between the inner and intermediate casing, and between the intermediate casing and an outer casing. 
         [0054]    At the hydraulic module second end  54 , there is a cement exit port  75 . At the hydraulic module second end  54  there is an upper packer mandrel  80  which includes a packer assembly  90  to seal the tool  10  into the well inner casing attached to the second end  81  of the upper packer mandrel  80  there is a breakaway barrier  70 . On the upper most portion of the tool  10 , there is a hydraulic hose guide  100  and lifting points  110  connecting the cement injection tool  10  by a lifting cable and hydraulic and services lines to the boat. 
         [0055]    As shown in more detail in  FIG. 2 , the entry nose  20  is designed with a taper  22  at the leading end thereof to allow for positioning the tool in a subsea well and to guide the tool  10  in to the well inner casing during deployment of the tool  10 . The entry nose  20  has also been designed to incorporated a hydraulic accumulator  25 . The hydraulic accumulator  25  is used to provide hydraulic pressure to the packer assemblies  40 ,  90  in the event of a failure in the tool  10  necessitating abandonment of the tool  10  in the well. The hydraulic accumulator  25  allows for the tool  10  to act as a barrier in the event that the tool  10  needs to be abandoned. The entry nose  20  may be held by a threaded portion  28  to the first end  31  lower packer mandrel  30 . 
         [0056]    The lower packer mandrel  30  is generally hollow but could be made of a range of materials or densities to provide the desired buoyancy characteristics of the tool  10 . The packer assembly  40  associated with the lower packer mandrel  30  is designed that once subjected to a hydraulic pressure, the packer assembly  40  can expand and seal against the inner casing. The pressure that can be applied to the packer assembly  40  is approximately 5000 psi, but could be more on some applications. At the second end  32  of the lower packer mandrel  30  there is packer mandrel threaded portion  33  that connects the lower packer mandrel  30  to the hydraulic module  50  at the hydraulic module first end  52 . 
         [0057]    The hydraulic module  50  is the module that contains active hydraulic components and the tooling required to perforate holes through the well inner casing. The hydraulic module  50  includes at least one hydraulic punch assembly  60 , though there may be as many as ten or more hydraulic punch assemblies  60 . The spacing and orientation of the hydraulic punch assemblies  60  is such that holes can be perforated through the inner casing in different locations around the circumference of the inner casing and in different positions vertically along the inner casing. 
         [0058]    In a preferred embodiment, the punch assemblies  60  are spaced apart such that the distance between a first punch  62  and second and subsequent punches  65  is greater than the length of the coupling members not shown normally used to couple lengths of well casing together. This is so that when the tool  10  is inserted into an inner casing holes can still be perforated even if one punch assemblies  60  is behind a coupling member, the remaining punch assemblies  60  will not coincide with the coupling members and therefore will able to perforate the inner casing. 
         [0059]    At the second end of the upper punch mandrel  82  there is a breakaway barrier  70 . This breakaway barrier  70  is designed such that should the device need to be abandoned in the well due to unforeseen circumstances, the well remains plugged such that the contents of the well will not leak. The breakaway barrier  70  has hydraulic lines and coupling check valves connected so that in the event of a breakaway event, the hydraulic pressure in the packer assemblies  40   90  remains constant, thus, ensuring that the packer assemblies  40   90  are held firmly in place against the inner casing. The breakaway barrier  70  is designed to have locking pins to take a predetermined load. These locking pins are designed to have sufficient strength that the tool  10  can be extracted from the inner casing even with residual cement surrounding the hydraulic module  50  yet can be broken away in the event that the tool  10  must be abandoned. A typical breakaway load is 25 tons but this load could be varied depending on the application of the tool  10 . 
         [0060]    The breakaway barrier  70  also includes a check valve on the sealant line that may be actuated by hydraulic pressure or automatically actuated (e.g. by spring loaded pressure). This check valve may be located in the upper packer mandrel  80  the check valve can be a normally closed check valve that is actuated by hydraulic pressure, or pneumatic pressure. 
         [0061]    The tool may be provided with a number of lines that communicate with the vessel (not shown). These lines will include hydraulic, control, monitoring and bypass lines. These line allow for the tool  10  to be operated from the vessel and parameters such as the pressure in the well can be monitored. 
         [0062]    Referring now to  FIG. 3 , the hydraulic punch cylinder assemblies  60  include two way hydraulic pistons  61  capable of at least 5000 psi or more, though the upper pressure limit may vary depending on the expected loads required to perforate the casing. The hydraulic pistons are fitted with punches  65  used to perforate the inner casing. The two-way piston is selected to ensure that the punch  65  can be retracted once a hole has been perforated in the inner casing. The two way type of hydraulic punch assembly includes a hydraulic feed  69  to provide hydraulic pressure to retract the piston 
         [0063]    The punch  65  is manufactured of a tool steel and is used to punch holes in the inner casing. The punch  65  is designed with a breakaway shaft  66  so that in the event of the punch  65  being jammed in the perforated hole in the inner casing the hydraulic piston  61  can be positively retracted and the punch  65  sheared. The punch  65  is held into the punch piston assemblies with a quick release ring  67 . This quick release ring can be removed to allow for field removal and replacement of the punch  65  in the situation where multiple wells are being abandoned and a punch  65  requires replacement. In the case of punches used for anchoring the device, these would preferably be non-breakaway punches, such that the punches remain extended to hold the device in place. 
         [0064]    Behind the quick release ring  67  is a resilient packer  68  that acts to absorb the shock induced on the punch  65  when the holes are produced. The resilient packer  68  may be made out of a range of materials capable of absorbing a shock load. Preferred materials are ultra high molecular weight synthetic materials, such as PEEK, UHMPE, HFPE, or Nylon etc, or other water stable dense synthetic materials. 
         [0065]    In an alternate embodiment, the hydraulic pistons  61  are not two way hydraulic pistons but use the pressure of the cement or formation to retract the hydraulic pistons  61  once the holes have been punched. In a possible variation the use of spring actuated hydraulic pistons may be used when the tool  10  is intended to be abandoned in the well. 
         [0066]      FIG. 4  shows the hydraulic module  50  of the lower perforation tool of  FIG. 1  in more detail. The module that contains active hydraulic components and the tooling required to perforate holes through the well inner casing. The hydraulic module includes at least one hydraulic punch assemblies  60 , and one of the cement feed outlets  75 . 
         [0067]      FIG. 5  shows an alternative embodiment of the device including first  60   a  and second  60   b  lower perforation assemblies, and first  60   c  and second  60   d  upper perforation assemblies. These are connected via a cable link  110  of variable length “D” to suit a particular application. Upper cup packer  112   a  and lower cup packer  112   b  are provided. These act to provide a seal between the device and the casing wall to prevent cement from flowing beyond the packer. They also provide a pressure seal if hydrocarbons present after perforating would otherwise leak out. 
         [0068]    Upper and lower bore supply ports  114  are provided. These ports supply cement respectively to the upper and lower sections of the device. 
         [0069]      FIGS. 6   a  and  6   b  shows a further embodiment including single acting spring biased hydraulic punches  65   a - 65   d . The punches are hydraulically extended to create holes through the inner casing of the bore, and are biased by spring pressure to the retracted position shown in the figures. 
         [0070]      FIGS. 7   a  and  7   b  show one of the hydraulic perforation assemblies  60 .  FIG. 7   a  is a perspective view of the assembly with a punch  65 . In sectional view  FIG. 7   b  of the assembly  60 , with the hydraulic piston  61   b  retracted within the body  61   a  of the assembly. The punch  65  is retained in place by a screw fit ring  120  analogous to the quick release ring in  FIG. 3 . Grub screws  122   a  and  122   b  retain the hydraulic cylinder  61   a  within the casing  124 . 
         [0071]    A hydraulic release shackle  116  is provided (analogous to the breakaway system previously described), which allows the device to be completely uncoupled i.e. in the event that the device becomes unrecoverable from the well. Annulus bore pressure monitoring and bleed off ports are provided. 
         [0072]    In operation the cement injection tool  10  is lowered from a vessel  1  and with the assistance of divers or an ROV is positioned into the inner casing of a subsea well. Once the cement injection tool  10  is lowered and is positioned, hydraulic pressure is applied forcing the packer assemblies  40 ,  90  to lock the cement injection tool  10  against the inner casing walls. The packers are then tested to ensure there are no leaks. Hydraulic pressure is then applied to each of the punch assembly  60  in turn resulting in a series of holes being perforated in the inner casing. Any pressure from the annulus is then bled off in a controlled manner either into the sea or into a tank on the vessel. Ideally the hole punching will result in multiple holes being punched in the inner casing, the holes being evenly distributed around the circumference and along a length of the inner casing. 
         [0073]    Once the holes in the inner casing have been perforated, a cement inhibitor is injected to inhibit the setting of the cement in the crevices and joints surrounding the packer assemblies and the punch assemblies. The inhibitor is injected through the cement injection port  54 , it then travels down past the hydraulics in the hydraulic module  50 . 
         [0074]    After the inhibitor has been injected, cement is injected through the cement injection port  54  and flows around the hydraulic module  50  and through the holes punched in the inner casing into the annulus between the inner casing and the first intermediate casing. Once the cement is injected into this annulus and pressure tested, the packer assemblies are released and the cement injection tool  10  is extracted. 
         [0075]    The punch assembly  60  includes hydraulics specifically designed for this application, which include a double acting hydraulic piston  61  (positive displacement and retraction piston). This is designed so that the punch  65  can be forcibly retracted from the inner casing in the event of a problem. The punch  65  is inserted into a hydraulic ring and is held in place by a shock absorbing ring  66  and a punch retaining member  67 . 
         [0076]    Variations and modifying are possible to the tool  10  that will still fall with the scope of the invention.