Abstract:
A system and method for sealing a passage around a cable is disclosed. Embodiments of the system can include an axial passage, such as a conduit and subsea wellhead housing connected to a wellbore, that can have a cable extending therethrough. The system can include an upper restrictor and a lower restrictor for closing the axial passage. An injection module having an injector and a reservoir can be fluid communication with the axial passage at an axial location between the upper restrictor and the lower restrictor. The injector can discharge a curable sealant initially stored in the reservoir into the axial passage so that at least a portion of the sealant contacts the cable at the axial location of the restrictor while the cable remains static.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates in general to mineral recovery wells, and in particular to an apparatus and method for sealing a wellbore. 
         [0003]    2. Brief Description of Related Art 
         [0004]    Wire line operations in a wellbore typically use one of three types of wire line—slick line, e-line, or braided cable. In order to maintain pressure control during these operations, and thus prevent pressurized fluid escaping from the wellbore, the wire line is passed through a pressure controlling device. Devices for preventing pressure from escaping from the well bore include wire line blowout preventers (“BOP”), pressure control heads (“PCH”), lower riser packages (“LRP”), and lubricators. 
         [0005]    These pressure control devices employ different methods of pressure control including rams, pressure energized packing sets, and grease. These methods, although different, follow the same principals in that they all form a seal around the outside of the wire line. It therefore follows that the outer profile and indeed construction of the wire line can significantly alter the effectiveness of the seal generated. For example, on braided cable, the structure is such that it has a labyrinth of leak paths so even with tight sealing on the outer diameter, leakage is possible through the gaps which exist in the structure of the cable itself In some cases grease is injected into the cable, under high pressure, to fill the void, thus reducing the ingress and leakage of wellbore fluids through the cable. Unfortunately, the grease will follow the same principle of leakage through the labyrinth and ultimately be depleted over the duration of the operation. The grease must be replenished to maintain the seal for a length of time. Therefore, it is desirable to have a semi-permanent seal for use in emergency situations. 
       SUMMARY OF THE INVENTION 
       [0006]    Embodiments of the claimed invention relate primarily to sealing in an emergency. Because e-line and braided cable can have a labyrinth of leak paths, conventional sealing techniques require constant grease injection in order to maintain a seal. Under certain circumstances, such as an emergency condition, the seal around the wire line may be required to maintain pressure control for a significant length of time. The grease supply will therefore deplete and may be not be replenished or maintain enough pressure to seal. Embodiments of the claimed invention can include a cylinder of sealant, such as an elastomer, epoxy, or some other plastic, any of which can be stored in a liquid or paste form. In some embodiments, the sealant can include particles of predetermined sizes. The sealant can be stored in a two- part resin form, where it can remain in a fluid state for a long period of time. Upon actuation of an emergency sequence, an injection module would deploy the pressurized sealant to a pre-defined chamber wellbore member via one or several ports. Upon injection, it would begin to chemically change and increase in viscosity until it is set, ultimately forming a seal within the labyrinth of the e-line or braided cable. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, are attained and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which drawings form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the invention and is therefore not to be considered limiting of its scope as the invention may admit to other equally effective embodiments. 
           [0008]      FIG. 1  is a partial side view of an embodiment of a pressure control head with an injection module according to an embodiment of the present invention. 
           [0009]      FIG. 2  is a partial side view of the embodiment of  FIG. 1 , showing the pressure control head in a pressurized position. 
           [0010]      FIG. 3  is a partial side view of the embodiment of  FIG. 1 , showing the pressure control head in a pressurized position and the cable sealing apparatus having injected sealant into the cable. 
           [0011]      FIG. 4  is a cross section of an exemplary embodiment of cable. 
           [0012]      FIG. 5  is a cross section of another exemplary embodiment of cable. 
           [0013]      FIG. 6  is a partial side view of a cable having sealant injected into it according to an embodiment of the present invention. 
           [0014]      FIG. 7  is a partial sectional side view of an injection module and a lower riser package according to an embodiment of the present invention. 
           [0015]      FIG. 8  is a partial sectional side view of an injection module and a blowout preventer according to an embodiment of the present invention. 
           [0016]      FIG. 9  is a partial sectional side view of an injection module positioned within a remotely operated vehicle, and a blowout preventer according to an embodiment of the present invention. 
           [0017]      FIG. 10  is a partial sectional side view of an injection module and a lubricator according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings which illustrate embodiments of the invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout, and the prime notation, if used, indicates similar elements in alternative embodiments. 
         [0019]    Referring to  FIG. 1 , cable  100  is a flexible cable suspended through pressure control head (“PCH”)  102  into a wellbore (not shown). Cable  100 , which has a small diameter relative to the wellbore, can be used to lower a wireline-run tool into a wellbore. PCH  102  can be used to form a seal against cable  100  so that pressure from the wellbore is not released around cable  100  during wireline operations. Bore  104  is an axial passage through PCH  102 . In some embodiments, bore  104  is sufficiently large inner diameter (“ID”) that a wireline-run tool can pass through PCH  102 . In other embodiments, cable  100  can be run through PCH  102  prior to attaching the wireline-run tool. 
         [0020]    As best shown in  FIGS. 4 and 5 , cable  100  can be a braided cable having individual strands  106  of wire or other fibers. Strands  106  can be twisted or woven together to provide a cable with sufficient tensile strength and flexibility to lower a wireline-run tool into the wellbore. Even with a tight twisting or braiding of strands  106 , however, gaps  108  can exist between strands  106 . Cable  100  can also have an uneven outer profile, or outer surface, because of the gaps  108  around its outer diameter. Because strands  106  generally run in the axial direction, gaps  108  can form a labyrinth of leak paths through which fluid can travel. As shown in FIG.  4 , a cable  100  having relatively large diameter wires or strands  106  can have large gaps  108 . As shown in  FIG. 5 , a cable  100 ′ having a larger number of small diameter strands  106 ′ can have a smaller gaps  108 ′, albeit a larger number of them. Cable  100  can be an electric line, or “e-line,” wherein one or more of the strands  106  are insulated electrical conductors. In some embodiments, the outer diameter of cable  100  can have a protective or insulated sheath  110 . Sheath  110  can be a braided sleeve around, for example, individually insulated wires. A leak path can exist for fluid to pass through sheath  110  and then along the individual wires. 
         [0021]    Upper lubricator  112  and lower lubricator  114  can be used to form a seal against cable  100 . As one of skill in the art will appreciate, lubricators  112  and  114 , which can be conventional, can include fingers for imparting grease to cable  100  as cable  100  moves through PCH  102 . The grease can fill gaps  108  within cable  100  and along the outer diameter of cable  100 . Lubricators  112  and  114  can form a seal against cable  100  during routine operations. 
         [0022]    During a high pressure condition in the wellbore, the seal between cable  100  and lubricators  112 ,  114  may be inadequate. A restrictor, such as pressure energized packing sets  116 , can be used to establish a more robust seal around cable  100 . In one embodiment, packing sets  116  can include chamber  118 , connected to pressure port  120 . Sealing face  122  is the inner diameter wall of chamber  118  and, thus, faces radially inward toward the axis of bore  104 . As best shown in  FIG. 2 , when pressure, such as pneumatic or hydraulic pressure, is applied through pressure port  120 , chamber  118  expands to cause sealing face  120  to move radially inward toward the center of bore  104  to occupy the annular space of bore  104 . As chamber  118  expands so that sealing face  122  presses against an outer diameter of cable  100  to limit the flow of wellbore fluid through bore  104 . As with conventional pressure control heads, the grease imparted by lubricators  112 ,  114  can reduce the flow of wellbore fluid through gaps  108  between strands  106  of cable  100 . 
         [0023]    During a period of prolonged exposure to a high pressure condition, the grease imparted by packing sets  112  and  114  may be insufficient to maintain a seal. The high pressure can, over time, displace the grease from gaps  108 , in which case wellbore fluid can flow around and through cable  100  and past packing set  116  to ultimately leak out of the wellbore. In some circumstances, such a prolonged high pressure condition can be an emergency condition. 
         [0024]    An injection module  124  can be connected to PCH  102 . Injection module  124  is used to inject a curable sealant  126  into an axial passage such as bore  104  so that sealant  126  contacts at least a portion of cable  100 . In one embodiment, sealant  126  is injected into a portion of bore  104  that is located between two flow restrictors such as, for example, packing sets  116 . In some embodiments, the sealant can be injected into other portions of the wellbore or riser, provided that sealant  126  contacts cable  100 . The flow restrictors force the sealant to flow around and through cable  100 . Without the flow restrictors, sealant  126  could flow freely out of bore  104  rather than being injected into gaps  108 . 
         [0025]    As shown in  FIGS. 1-3 , injection module  124  has an injection port  128 , which is a tube or other fluid path from injection module  124  into bore  104 . Injection port  128  is located between two flow restrictors such as, for example, packing sets  116 . A one-way valve, such as check valve  130 , can be used to prevent fluid in bore  104  from moving through injection port  128  into injection module  124 . Injection module  124  can have a syringe type injector, wherein the sealant is initially stored in reservoir  132  and plunger  134  is actuated to force the sealant out of the reservoir and into bore  104 . In the embodiment shown in  FIGS. 1-3 , reservoir  132  is a part of the syringe injector. As best shown in  FIG. 3 , reservoir  132  can hold a sufficient volume of sealant  126  to adequately fill bore  104  between packing sets  116  with enough sealant  126  to cause at least a portion of the sealant to contact the outer diameter of cable  100 . In one embodiment, there is sufficient sealant  126  to cause at least a portion of the sealant to flow through gaps  108  in the vicinity of packing sets  116 . 
         [0026]    Plunger  134  can be actuated by any of a variety of techniques. For example, plunger  134  could be connected to a hydraulic piston and hydraulic pressure from the surface platform or from a remotely operated vehicle (“ROV”) (not shown in  FIGS. 1-3 ) can move the piston to actuate plunger  134 . Alternatively, plunger  134  could have a lead screw and an electric motor could rotate the lead screw to actuate plunger  134 . In another embodiment, an ROV can mechanically actuate injection module  124 . For example, the rod  136  of plunger  134  can be accessible from outside of the wellbore member such as PCH  102 , such that an ROV (not shown in  FIGS. 1-3 ) can move the rod to actuate plunger  134 . In one embodiment, injection module  124  is only actuated after the other sealing apparatus in the wellbore, such as PCH  102 , blowout preventers (not shown in  FIGS. 1-3 ), and various valves (not shown in  FIGS. 1-3 ) are closed to seal the wellbore. 
         [0027]    Sealant  126  can be any type of sealant for sealing gaps  108  or forming a seal between the outer diameter of cable  100  and the cable-facing surface of a restrictor, such as sealing face  120 . Sealant  126  can be stored as a liquid or paste, and can remain in a fluid state for a long period of time. Sealant  126  can chemically change upon injection into bore  104  so that it begins to harden and increase in viscosity. In one embodiment, sealant  126  can be an elastomer that sets, or hardens, under a pre-determined condition. For example, the elastomer could set after reaching a certain temperature or pressure. In another embodiment, the elastomer could set upon being exposed to a particular chemical. In the embodiment wherein the elastomer sets in response to reaching a certain pressure, the pressure can be selected so that bore  104  can be filled with the elastomer and the elastomer will set only after the pressure is sufficiently high to cause a portion of the elastomer to enter gaps  108  or enter the gap that may exist between cable  100  and sealing face  120 . In one embodiment, sealant  126  can be a curable sealant that hardens after being injected, such as, for example, a curable polymer, a binary epoxy, or two-part resin, wherein the sealant is initially stored as two separate liquids. As shown in  FIG. 6 , the two liquids can be mixed as they are injected into the bore, thus forming a sealant which will set in a predetermined amount of time or in response to predetermined conditions. In the embodiments described, the sealant can be a semi-permanent sealant such that removing the sealant, after it has set, requires a specific solvent or requires machining and re work of the cavity and bores. 
         [0028]    In one embodiment, sealant  126  can include a fluid suspended particulate such that, upon injection, a portion of the particulate will lodge in flow restrictions such as gaps  108  or the annular space between cable  100  and sealing face  120 . As shown in  FIG. 6 , various sizes of particulate can be used to form seals within cable  138  by sealing gaps between strands  140 . In one embodiment using at least two sizes of particulate, larger particulate  142  can fill large gaps  144  between strands  140 , and then smaller particulate  146  can lodge between the larger particulate and the strands, and can fill small gaps  148 , to form a tighter seal. A liquid sealant can then complete the seal, if needed, by adhering to the large and small particulate and the strands. 
         [0029]    In one embodiment, as shown in  FIG. 7 , injection module  150  can include more than one reservoir. For example, injection module  150  can include a first reservoir  152  containing a first fluid  154  and a second reservoir  156  containing a fluid  158 . The fluids within the reservoirs  152 ,  156  can be injected by plungers  160  and  162 , respectively. In one embodiment, the fluid can be contained in reservoirs  152 ,  156  by rupture discs  164  to keep the fluid from mixing prematurely. Alternatively, a valve, check valve, or other device can be used to contain the fluids within reservoirs  152 ,  156 . In embodiments where it is desirable to have the fluids mix prior to entering bore  104 , the fluids can be mixed in tubing  166 . In one embodiment, tubing  166  can include a mixing device (not shown) to promote the mixing of the fluids. The mixing device can be, for example, a vortex or series of baffles. This can be useful when the sealant is an epoxy having a separate curing agent. The reservoirs  152 ,  156  can be, but are not required to be, the same size or the same configuration. The fluid or fluids from the reservoirs  152 ,  156  can travel through tubing  166  to injection port  168 , which is in communication with bore  170 . A check valve  172  can be used to prevent fluid from bore  104  from entering tubing  166 . 
         [0030]    In one embodiment, the fluids can be a solvent and an elastomer, or a solvent and an epoxy. For example, reservoir  152  can initially contain a solvent that is suitable to displace grease, while reservoir  156  initially contains an elastomer sealant. The solvent, such as, for example, methanol, can be injected into bore  170  first, and used to displace grease from cable  174 . After a predetermined condition, such as a given amount of time, the elastomer from reservoir  156  can be injected into bore  170  to fill gaps in cable  174 . This can be useful when, for example, grease is occupying the gaps in cable  174  and that grease would prevent the elastomer from filling the gaps. Because the grease can be displaced over time, and thus undermine the seal, it can be beneficial to displace the grease before injecting the elastomer. In embodiments that do not use a solvent, the pressure of the sealant can displace some or all of the grease as the sealant is injected into the bore. In one embodiment, a solvent from a first reservoir  152  can be used to first displace and flush any grease that may be on cable  174 , followed an etching agent from the second reservoir  156 . The etching agent can be used to clean and prepare surfaces within cable  174  and within bore  170  to better adhere to the sealant. A sealant from a third reservoir (not shown) can then be injected under high pressure to fill the gaps and adhere to the surfaces of cable  174  and bore  170 . 
         [0031]    Still referring to  FIG. 7 , injection module  150  can be connected to lower riser package (“LRP”)  176 . Restrictors such as rams  178  can be used to close bore  170 . A sleeve  182  can run through LRP  176  and be used to guide cable  174 . Injection port  168  can be connected to sleeve  182  so that sealant is injected into sleeve  182  when injection module  150  is actuated. When rams  178  move inward toward the center of bore  170 , they apply sufficient pressure to deform sleeve  182  around cable  174  such that the inner diameter of sleeve  182  is pressed against the outer diameter of cable  174 . When the sealant is injected into sleeve  182 , the flow path of least resistance will be through the gaps  108  ( FIGS. 4 &amp; 5 ), thus imparting sealant into cable  174 . Furthermore, less sealant is required because the narrow diameter of sleeve  182  and the constriction of sleeve  182  due to rams  178  reduces the volume of sealant that must be injected. In some embodiments, the sealant does not flow axially past rams  178  due to the tight constriction. In some embodiments, some sealant does flow past rams  178  is it fills gaps  108 . 
         [0032]    The sealant injection system is not limited to use in a pressure control head. It can be used with any of a variety of wellbore devices, especially devices that constrict the bore around a wireline. As shown in  FIG. 8 , injection module  186  can be used in conjunction with blowout preventers  188 . In this embodiment, rams  190  move inward toward the center of bore  192  to prevent fluid flow through bore  192 . Injection module  186  can inject sealant  194  into bore  192  to fill gaps within cable  196 , which is extended between rams  190 . Sealant  194  can flow between rams  190  and adhere to the opposing faces of rams  190  and the annular gaps between rams  190  and cable  196 . Because it is injected under high pressure, sealant  194  can be forced through the strands of cable  196 , in the vicinity of rams  190 , and fill gaps within cable  196 . 
         [0033]    Still referring to  FIG. 8 , injection module  186  can be of various configurations suitable for injecting sealant into bore  192 . In the embodiment shown in  FIG. 7 , injection module  186  includes a reservoir  198  that is a cylindrical vessel, although reservoir  198  can be other shapes. Pump  200  is connected to reservoir  198 . Pump  200  can be any type of pump including, for example, a diaphragm pump or a centrifugal (impeller) pump. Tubing  202  can connect injection module  186  to bore  192 . One or more injection ports  204  can be used to inject sealant  194  into bore  192 .  FIG. 7  is shown with two injection ports  204  spaced apart around bore  192 , each with a check valve  206 . In some embodiments, the injection ports can be located axially nearer to one or the other restrictor such as rams  190 . 
         [0034]    Referring to  FIG. 9 , injection module  208  can be located apart from riser  210 . For example, injection module  208  can be located inside a remote operating vehicle (“ROV”)  212 . In this embodiment, an injection port  214  is connected to riser  210 , between a pair of BOPs  216 . Connector  218  of ROV  212  can connect to injection port  214  to inject a sealant into the bore of riser  210 . For example, ROV  212  can stab into a fluid passage in communication with injection port  214  and, thus, in communication with the bore of riser  210 . Connector  218  can be, for example, a quick disconnect fitting that mates to a corresponding quick disconnect fitting on injection port  214 . ROV  212  can connect connector  218  to injection port  214  so that after the restrictor, such as BOPs  216 , close around cable  220 , injection module  208  can inject sealant through injection port  214  to infuse cable  220  with sealant. 
         [0035]    Referring to  FIG. 10 , in another embodiment, injection module  222  can be used with lubricator  224 . In this embodiment, the restrictors are the lubricators  226 , with no other restrictors required. Injection module  222  can inject sealant through injection port  228  and into bore  230  of lubricator  224 . The sealant can permeate through bore  230  and into cable  232 , so that cable  232  can form a better seal against lubricators  226 . In the embodiment shown in  FIG. 10 , injection module  222  has a lead screw  234  to inject sealant from reservoir  236 , through check valve  238 , into bore  230 . 
         [0036]    Referring back to  FIGS. 1-3 , in operation of an embodiment, a seal can be formed around cable  100  that extends through a conduit, such as bore  104 , and a subsea wellhead assembly into a wellbore. The seal can be formed by, for example, providing upper and lower passage restrictors such as packing set  116  in the conduit above the wellhead assembly. An injection module  124  can be connected to injection port  128 , which is a port through a sidewall of bore  104 . Injection port  128  is located between the upper packing set  116  and the lower packing set  116 . Injection module  124  can have an injector and a reservoir  132 , the reservoir  132  can initially contain a curable sealant  126 . 
         [0037]    The wellbore restrictors, such as packing sets  116 , can be actuated so that sealing face  122  of the restrictors move radially toward the center of bore  104 . Curable sealant can be injected from injection module  124 , through injection port  128  so that curable sealant  124  flows around cable  100  between the upper and lower passage restrictors. In some embodiments, the restrictors can be actuated before curable sealant  124  is injected. 
         [0038]    In some embodiments, the restrictors can be actuated after curable sealant  124  is injected. Curable sealant  124  can fill bore  104 , permeate gaps  108  ( FIG. 4 ) in cable  100 , and fill any annulus space that may exist between the restrictors (such as sealing face  122  of packing set  116 ) and the outer diameter of cable  100 . In embodiments, curable sealant  124  can cure to form a plug encompassing cable  100  and filling the space between cable  100  and the as-yet un-actuated restrictors. Subsequently, when the restrictors are actuated, sealing face  122  can move inwards to exert pressure against the now cured, or solidified, curable sealant  124 , thus energizing curable sealant  124  as a seal between sealing face  122  and cable  100 . In some embodiments, curable sealant  124 , after it has cured, can provide the assistance of a preload force between any or all sealing surfaces. 
         [0039]    In embodiments, curable sealant  124  can be stored as two or more separate components in two or more separate vessels  152 ,  156  in the reservoir. The two or more separate components  154 ,  158  can react to form the curable sealant when the components are mixed prior to or during the injection of the components through injection port  128 . In embodiments, cable  100  can include a braided material and curable sealant  124  can be injected into the braided material. In embodiments, cable  100  can be remain axially stationary during the injection of curable sealant  124  and during the actuation of the restrictors. In some embodiments, cable  100  can be axially moved after the injection of curable sealant  124  so that the portion of cable  100  having sealant  124  is moved toward a restrictor prior to actuating the restrictor. In some embodiments, the reservoir can include a first and second container. The first container can initially contain a solvent and the second container can initially contain curable sealant  124 . The solvent can be injected before the sealant to remove grease from cable  100 , and then curable sealant  124  can be injected. 
         [0040]    While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention.