Abstract:
Devices and methods useable for repairing seal surfaces in an oil and gas installation used at offshore locations are provided. A removable device useable for locally repair a seal surface of a receiver plate, includes a rigid portion and a seal. The rigid portion is made of a material substantially similar to a material of the receiver plate, and is configured to be removably inserted in a fluid port of the receiver plate, having a seal surface flushed with the seal surface of the receiver plate when the device is inserted in the fluid port, and a channel configured to allow a fluid communication. The seal is made of a rubber-like material and is placed outside the rigid portion, the seal being configured to prevent a fluid leak.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    Embodiments of the subject matter disclosed herein generally relate to devices and methods useable for repairing seal surfaces of an oil and gas installation used at offshore locations, more particularly, to a removable device with a seal surface, a receiver plate having a seal surface and configured to accommodate one or more removable devices, and related methods of locally replacing seal surface. 
         [0003]    2. Discussion of the Background 
         [0004]    During the past years, with the increase in price of fossil fuels, the interest in developing new production fields has dramatically increased. However, the availability of land-based production fields is limited. Thus, the industry has now extended drilling to offshore locations, which appear to hold a vast amount of fossil fuel. 
         [0005]    An installation for drilling at an offshore location includes a subsea blowout preventer (“BOP”) stack useable to seal a wellbore during drilling operations, both for safety and environmental reasons. As shown in  FIG. 1 , a subsea blowout preventer (“BOP”) stack includes a lower blowout preventer stack  10  attached to a wellhead on the sea floor  20 , and a Lower Marine Riser Package (“LMRP”)  30  at a distal end of a marine riser  40 , extending from a drill ship  50  or any other type of surface drilling platform or vessel. When desired, blowout preventers of the LMRP  30  and of the lower BOP stack  10  may be closed. The LMRP  30  may be detached from the lower BOP stack  10  and retrieved to the surface, leaving the lower BOP stack  10  atop the wellhead, on the sea floor  20 . Thus, for example, the LMRP  30  may be retrieved when inclement weather is expected or when work on a particular wellhead is to be temporarily stopped. The LMRP  30  may include a stinger  26  at its distal end configured to engage a receptacle  29  located on a proximal end of lower BOP stack  10 . 
         [0006]    Various electrical, mechanical, and hydraulic control signals need to be transmitted from the surface vessel  50  to devices (e.g., BOPs  60 ) located in the LMRP  30  and the lower BOP stack  10 . In order to enable transmitting these signals, multiple electrical cables and/or hydraulic lines are used. 
         [0007]    Several and varied feed-thru components may be used to carry some of the signals (including working fluids) between the LMRP  30  and the lower BOP stack  10 . A MUX “pod”  70  is a subsea single mono-block feed-thru component attached to the LMRP  30  enabling transmission of a plurality of hydraulic control signals to the lower BOP stack  10 . 
         [0008]    The MUX “pod”  70  is detailed in  FIG. 2 , showing a plurality of output ports  80  on wedge sides  75  (one visible) of the MUX “pod”  70 . When the LMRP  30  is engaged with the lower BOP stack  10 , the MUX “pod”  70  is lowered to engage with a receiver plate  90  located on the lower BOP stack  10  such that the ports  80  on the wedge sides  75  communicate with ports  85  on a wedge side  95  of the receiver plate  90 . The wedge side  90  of the receiver plate has a seal surface to prevent hydraulic fluid to leak outside intended channels, from the ports  80  to the ports  85 . 
         [0009]    A fluid port is an exit of a channel configured to enable a fluid communication between the LMRP  30  and the lower BOP stack  10 , while engaged with each other. The size of the fluid ports may be in a range of ½″ to 2″ diameter depending on the functions they serve related to the devices in the lower BOP stack  10  towards the fluid is directed. 
         [0010]    Any scratch occurring during transport or exploitation on the seal surface of the wedge  95  of the receiver plate  90 , in the proximity of any fluid port  85  compromises the integrity of the seal, and, therefore, a seal function between the MUX “pod”  70  and the receiver plate  90 . When the seal surface  95  of the receiver plate  90  is damaged, the repairs trigger costly downtime (e.g., rig downtime cost 500,000$/day). A damaged seal surface may have to be machined. Weld repairs can be used, but their execution may distort the metal from which the receiver plate is made leading to additional downtime. Sometimes, the receiver plate  90  (which, for example, may weigh up to 500 lb and may have dimensions of 2 ft×3 ft×½ ft) has to be replaced. 
         [0011]    Accordingly, it would be desirable to provide devices and methods that avoid the long and costly repairs of the seal surfaces. 
       SUMMARY 
       [0012]    According to an exemplary embodiment a removable device useable for locally repairing a seal surface of a receiver plate is provided. The removable device includes a rigid portion is made of a material substantially similar to a material of the receiver plate, and is configured to be removably inserted in a fluid port of the receiver plate, the rigid portion having (i) a seal surface flushed with the seal surface of the receiver plate when the device is inserted in the fluid port, and (ii) a channel configured to allow a fluid communication. The removable device also includes a seal made of a rubber-like material and placed outside the rigid portion, and configured to prevent a fluid leak. 
         [0013]    According to another exemplary embodiment, a receiver plate configured to engage with one or more removable devices having a seal surface is provided. The receiver plate has one or more channels configured to allow fluid to pass therethrough, and at least one fluid port formed at an end of a channel among the one or more fluid channels, the at least one fluid port being configured to receive a removable device. The receiver plate also includes a wedge seal surface ( 320 ) on which the at least one or more fluid ports open to achieve a fluid communication, the wedge seal surface being configured to prevent fluid leak when the receiver plate is engaged with another wedge having a surface with one or more wedge fluid ports. 
         [0014]    According to another exemplary embodiment, a method of repairing a receiver plate being damaged on a wedged seal surface with one or more fluid ports in an oil and gas installation is provided. The method includes mounting a removable device with a seal surface configured to flush with the wedged seal surface, the removable device being mounted inside a fluid port located in a damaged portion of the wedged seal surface. The method further includes machining the seal surface of the removable device and a portion of the wedged seal surface surrounding the fluid port. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. In the drawings: 
           [0016]      FIG. 1  is a schematic diagram of an offshore rig; 
           [0017]      FIG. 2  is a schematic diagram of a MUX pod; 
           [0018]      FIG. 3  is a schematic diagram of a receiver plate; 
           [0019]      FIG. 4  is a cross-section of a removable device according to an exemplary embodiment; 
           [0020]      FIG. 5  is a cross section in a receiver plate according to another exemplary embodiment; 
           [0021]      FIG. 6  is a cross section in a receiver plate having a removable device mounted therein according to another exemplary embodiment; 
           [0022]      FIG. 7  is a view of a portion of a seal surface of a receiver plate in which a removable device is inserted according to an exemplary embodiment; and 
           [0023]      FIG. 8  is a flow chart of a method of repairing a receiver plate having a damaged seal surface, according to an exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    The following description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to the terminology and structure of a subsea oil and gas installation having seal surfaces with fluid ports interfacing detachable parts. However, the embodiments to be discussed next are not limited to these systems, but may be applied to other systems that require local repair of a seal surface around a fluid port at a low price and with a reduced repair time. 
         [0025]    Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments. 
         [0026]      FIG. 4  illustrates a cross section across a removable device  200  according to an exemplary embodiment. The device  200  includes a rigid portion  210  and an O-ring  220  seal. The rigid portion  210  is made of a material similar with the material of a receiver plate in which the device is inserted (e.g., stainless steel). The O-ring  220  seal is made of a rubber-like material (e.g., an elastomer). In a non-limiting embodiment, the removable device  200  has a diameter D of about 1″ and a length L of about 1.5″. The O-ring seal  220  illustrated in  FIG. 4  is not intended to be limiting relative to the useable types of seals. Seals having other types of seals than the O-type may be used to prevent a fluid leak between the receiver plate and the removable device  200 . 
         [0027]    The rigid portion  210  has a tubular shape with a channel  212  substantially in the middle. When the LMRP and the lower BOP stack are attached to each other, fluid from the MUX pod may circulate through the channel  212  towards devices in the BOP stack. Threads  214  are located on an outer surface of the rigid portion  210 . The threads  214  have shapes complementary to threads in a fluid port of the receiver plate configured to receive the removable device  200 . The threads  214  may be SAE threads (i.e., as standardized by Society of Automotive Engineers). A surface  216  of the rigid portion  210  aligns (flushes) with the seal surface of the receiving plate, when the removable device  200  is mounted in a corresponding fluid port of the receiving plate. At an end  218  of the rigid portion  210 , opposite to the surface  216 , a groove  219  is configured to accommodate the O-ring seal  220 . 
         [0028]    In order to accommodate one or more removable devices similar to the one illustrated in  FIG. 4 , a receiver plate  300  (a cross section through a portion of which is illustrated in  FIG. 5 ) may be manufactured to have one or more fluid ports  310  substantially perpendicular to the wedged seal surface  320 , along channels  340  configured to direct fluid towards devices in the lower BOP stack. Alternatively, in order to repair a seal surface around a fluid port on an existing receiver plate, a fluid port  310  may be drilled enlarging the existing port in order to enable receiving a removable device therein. 
         [0029]    Threads  330  may be formed on at least a part of the inside surface of the fluid port  310  to configure the receiver plate  300  to receive the removable device  200  therein. The depth of the fluid port  310  is substantially equal to the length L of the removable device  200  to be mounted therein. The fluid port  310  may be configured along a fluid channel  340 , and emerges substantially perpendicular to the seal surface  320 . The threads  330  have shapes complementary to shapes of threads  214  on an outer surface of the removable device  200  to be mounted in the fluid port  310 . 
         [0030]      FIG. 6  is a cross section in a receiver plate  300  having a removable device  200  mounted therein. The threads  330  on the inner surface of the fluid port  310  in the receiver plate  300  are engaged with the threads  214  on the outer surface of the rigid portion  210  of the removable device  200 . The surface  216  of the removable device  200  aligns (flushes) with the seal surface  320  of the receiver plate  300 . The channel  340  in the receiver plate and the channel  212  of the removable device  200  may have substantially similar diameters and extend along the same axis  250 . 
         [0031]      FIG. 7  is a view of a portion of a seal surface  320  of a receiver plate  300  in which a removable device  200  is inserted according to an embodiment. The seal surface  216  may align with the surface  320  in a manner that would require no other operation for completing the repair. However, the surface  216  of the removable device  200  and a part  260  of the seal surface  320  surrounding the surface  216  may be locally machined to improve the overall sealing quality. 
         [0032]    Thus when a scratch affecting the seal related to a port  285  occurs in an area where a removable device is mounted, the device  200  is removed (e.g., un-screwed) and another similar device is inserted in the fluid port (e.g.,  310 ). Alternatively, for a conventional receiving plate, when a scratch affecting sealing of a fluid port occurs, a fluid port with inner threads is formed to enable inserting of a removable device (e.g.,  200 ) therein. Local machining of an area including the outer surface of the removable device and the surrounding part of the seal surface may be performed to ensure smoothness and, thus, enhancing the sealing quality of the seal surface after this repair. 
         [0033]    By using removable devices with a seal surface to repair a seal surface, the downtime is shortened and the cost of the repair is reduced. Additionally, instead of machining the entire angled surface, machining may be performed only locally and smaller machines may be used. Another advantage is that since damaged areas are locally repairable, the need to replace the receiver plate occurs less frequently. 
         [0034]    The flow chart of a method  400  of repairing a receiver plate having damage on a seal surface with one or more fluid ports is illustrated in  FIG. 5 . 
         [0035]    The method  400  includes mounting a removable device with a seal surface in a fluid port of the receiver plate such that the seal surface of the removable device substantially aligns with the seal surface of the receiving plate, at S 410 . The method  400  further includes machining an area including the seal surface of the removable device and a portion of the seal surface of the receiver plate, the portion surrounding the seal surface of the removable device, at S 420 . 
         [0036]    If the receiving plate is a plate manufactured to have a fluid port in which a device with a seal surface is inserted, and a damaged portion of the seal surface includes the seal surface of the existing device, prior to S 410 , removing the existing device is performed. If the receiving plate is a conventional plate manufactured without a fluid port in which a device with a seal surface to be inserted, a fluid port configured to receive the device is formed, prior to S 410 . 
         [0037]    The disclosed exemplary embodiments provide devices and methods for repairing seal surfaces of a receiver plate in a subsea oil and gas installation. It should be understood that this description is not intended to limit the invention. On the contrary, the exemplary embodiments are intended to cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the exemplary embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details. 
         [0038]    Although the features and elements of the present exemplary embodiments are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein. 
         [0039]    This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims.