Patent Publication Number: US-8967589-B2

Title: Seal

Description:
FIELD OF THE INVENTION 
     The present invention relates to seals and sealing arrangements, especially those used in wireline valves. 
     BACKGROUND TO THE INVENTION 
     Seals prevent or mitigate leakage of one fluid into another. They may be selectively applied i.e. a flow may be allowed until a certain condition is reached and it is desirable for such fluid flow to be halted. 
     In a wireline well intervention environment, one application of such seals and sealing arrangements is wireline valves. Wireline valves or “WLVs” are backup valves used on wellbores when wireline is present in the event of wireline based intervention in the wellbore. 
     Wellbores frequently have highly flammable fluids at elevated temperatures and pressures within them. In the event of a mechanical problem on the wireline, such as stranded wire, the WLVs may be closed around the line to seal the wellbore allowing remedial work to be performed on the section of line above the valve. 
     Such wireline valves may have to seal a well for a prolonged period of time, typically more than 12 hours, until such times as the wireline and associated equipment can be repaired or replaced, the wellbore is permanently sealed or some other intervention made. 
     There are two general types of wireline valve rams: the line sized and shear/seal ram types. 
     Line sized rams, be they multi- or specific line size configuration, enable the wireline valve to close around static cable when activated. The rams contain rubber elements which, when actuated by the hydraulic actuators, apply such rubber pressure around the cable that an effective seal is created. Combined with a second set of rams, and standard viscous grease injection into the intermediate void, an effective well barrier is created through the application of rubber pressure around the cable and grease filling the intermediate voids inside the cable. 
     Shear/Seal type rams combine a cutting element at the front of the rams with blind seals to create an effective well barrier after the line has been cut and dropped. 
     Ram wireline valves typically have two gate-like members which, in a normal operating position, are positioned either side of a central bore of a wireline valve and upon actuation are forced together to prevent fluid flow. 
     The seals of a wireline valve may have to withstand the elevated temperatures and pressures of the wellbore fluid. 
     Rubber or some other elastomeric materials are often optimal sealing materials, as their resilience and imperviousness may produce good sealing arrangements. However, they may not be best suited to the high temperatures and pressures, and the seals may yield and flow and eventually fail if subjected to such conditions for extended periods. 
     The seals of either type will often be reinforced by attaching an elastomeric material to a metal reinforcing plate, either on one side, or more typically, by sandwiching the elastomeric material between two metal plates. 
     Typically, the wireline valve will have a wireline, rod or pipe suspended through it, and this wireline, rod or pipe may be attached to downhole tools or monitoring equipment. The wireline valve seals are usually adapted such that upon activation, a tight seal is formed around these wirelines, rods or pipes but they do not sever them nor is a good seal prevented by their presence. 
     In a wireline valve ram, the mating seal faces of the metal plates will usually include complementary channels positioned parallel to the wireline (for example) such that when the blowout preventer is activated, the channels form bores in the adjoined metal plates that the wireline is encased within. The elastomeric seal bodies will initially have a planar mating seal side face and the elasticity of the material allows it to be shaped around a wireline without severing it. The steel plates, being rigid, require the channels to be cut in them or it may either prevent a good seal forming or may damage/sever the wireline. 
     The elastomeric material immediately surrounding the wireline may be subject to the direct pressure and potentially elevated temperature from the fluid in the wellbore i.e. the steel reinforcing plates may not wholly cover that section of material. The elastomeric material may then be prone to flow or quasi-liquefy about the wireline and thereby eventually breaking the seal after sufficient exposure time. 
     The wireline valve rams and associated inner seals are designed such that when sealing under well pressure conditions the rams are energised by well pressure rather than hydraulic actuators. The rams have an amount of running clearance between the actuator and ram body which enables the rams to move independent of the actuator, typically about ⅛″ linear movement. Furthermore, the inner seals have a portion at the back where rubber protrudes beyond the supporting plates in a backwards direction, ensuring that the pressure face between ram body and inner seal is made up wholly of rubber. This ensures that the ram is able to maintain rubber pressure even in the event of rubber flow/loss over the cable interface as the ram will continually move to compensate for lost rubber volume. Thus inner seals can accommodate a certain amount of rubber loss without loss of seal integrity. Restricting this loss of rubber critical in the design of inner seals. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention there is provided a seal comprising an elastomeric seal body with a sealing surface, a plurality of generally planar inserts embedded within the elastomeric seal body adjacent the sealing surface, and having elastomeric seal material disposed between the plurality of generally planar inserts. 
     The elastomeric seal body may be of a generally cuboidal or toroidal shape. 
     By “generally planar”, it will be understood that this definition also includes generally wedge-shaped or prism-shaped inserts having a generally large ratio of facial dimension to mean thickness. 
     The generally planar inserts may be metallic, and may be copper alloys such as brass or aluminium bronze. 
     The generally planar inserts may have a slightly wedge shape, expanding from a first thickness deployed immediately adjacent the sealing surface, to a second thickness at the distal end thereof. The second thickness may be less than twice the first thickness. 
     The thickness of elastomeric material disposed between adjacent generally planar inserts may be equal to or less than the second thickness of the generally planar inserts, and may be equal to or less than the first thickness of the generally planar inserts. The thickness may be equal to or less than 2 mm, and may be equal to or less than 1 mm. 
     A plurality of the generally planar inserts may be embedded into the elastomeric seal body in a generally fan-shaped orientation. They may be orientated such that upon contacting a substantially tubular shaped body to be sealed around and the subsequent deformation of the seal body about said substantially tubular shaped body, the plurality of generally planar inserts become orientated such that they extend radially from the substantially tubular shaped body. 
     First edges of the generally planar inserts at the first thickness may be exposed i.e. they are not covered by isometric material. Second edges of the generally planar inserts, being perpendicularly adjacent the first edges may also be exposed i.e. they are not covered by isometric material. In use, both first edges and second edges may be covered by, for example, a substantially tubular shaped body to be sealed and reinforcing plates respectively. 
     The seal body may have a first arrangement of a plurality of generally planar inserts adjacent the sealing surface and a first surface of the seal body, the first surface being adjacent and substantially perpendicular to the sealing surface, and a second arrangement of a plurality of generally planar inserts adjacent the sealing surface and a second surface of the seal body, the second surface also being adjacent and substantially perpendicular to the sealing surface. The first and second surfaces may be upper and lower surfaces of the seal body. 
     There may be a discrete thickness of seal body between the innermost extents of the first and second arrangements. Such extents may be defined by fourth edges  32   d  ( FIG. 3 ) of the generally planar reinforcing elements, being the opposite edges to the second edges. 
     According to a second aspect of the present invention there is provided a wireline valve including at least one seal according to the first aspect. 
     According to a third aspect of the present invention there is provided a blow-out preventer including at least one seal according to the first aspect. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will now be described, by way of example only, with reference to the following drawings, in which: 
         FIG. 1  is a perspective view of a first embodiment seal according to a first aspect of the present invention; 
         FIG. 2  is an exploded perspective view of the seal of  FIG. 1 ; 
         FIG. 3  is a detail perspective view of  FIG. 2 ; 
         FIG. 4  is a further exploded perspective view of the seal of  FIG. 1 ; 
         FIG. 5  is a detail perspective view of  FIG. 4 ; 
         FIG. 6  is a perspective view of two seals according to an first aspect of the present invention; 
         FIG. 7   a - 7   d  are perspective detail views of the deformation mechanism of the seal of  FIG. 1 ; 
         FIG. 8  is a perspective view of a second embodiment seal according to a first aspect of the present invention; 
         FIG. 9  is an exploded perspective view of the seal of  FIG. 8 ; 
         FIG. 10  is a detail perspective view of  FIG. 9 ; 
         FIG. 11  is a further exploded perspective view of the seal of  FIG. 8 ; 
         FIG. 12  is a detail perspective view of  FIG. 11 ; 
         FIG. 13  is a further exploded perspective view of the seal of  FIG. 8 ; and 
         FIG. 14  is a perspective view of two second embodiment seals according to a first aspect of the present invention. 
     
    
    
     Referring to the drawings and initially to  FIG. 1 , a seal  10  is depicted comprising a seal body  12 , an upper reinforcing steel plate  14  and a lower reinforcing steel plate  16 . The seal body  12  is formed from an elastomeric substance, in this case rubber, and is sandwiched between the upper reinforcing steel plate  14  and the lower reinforcing steel plate  16 . 
     The seal body  12  is substantially a rectangular cuboid shape. An upper lip  18  extends from its upper surface  22 , projecting from three of the four edges of the upper surface  22 . A lower lip  20  also extends from the lower surface  24 , again projecting from three of the four edges of the lower surface  24 . The upper and lower lips  18 , 20  define upper and lower plate housings  26 , 28  into which the upper reinforcing steel plate  14  and the lower reinforcing steel plate  16  are received. The lips  18 , 20  provide sealing surfaces over the plates  14 , 16  in order to facilitate seal integrity. 
     The plates  14 , 16  are largely identical. They are substantially rectangular. A first edge  14   a , 16   a  is at a slight angle and not perpendicular to upper and lower surfaces of the plates  14 , 16 . These edges  14   a , 16   a  abut correspondingly angled surfaces  18   a , 20   a  of the lips  18 , 20 . 
     The seal body  12  has a seal face  30 . The seal face  30  extends between the upper surface  22  and the lower surface  24 , between the edges of the upper and lower surface  22 , 24  which do not have a lip  18 , 20  adjoined. 
     The seal face  30  is substantially planar. At an approximate mid-point of the greater dimension of the seal face  30 , adjacent the upper and lower surfaces  22 , 24  are provided upper and lower reinforcing arrangements  34 , 36 . The reinforcing arrangements  34 , 36  each comprise a plurality of substantially planar but slightly wedge-shaped brass inserts  32  embedded within the seal body  12 . As well as brass, other suitable alloys may be employed, such as aluminium bronze. 
     The brass inserts  32  have a high ratio of length and width to thickness i.e. they are relatively thin planar inserts. They are also slightly wedge shaped i.e. they expand from a first thickness T 1 , first edge  32   a , of about 0.5 mm to a second thickness T 2 , third edge  32   c , of about 2.0 mm. The brass inserts  32 , although embedded, are also exposed along two adjacent edges: a first edge  32   a  (which has a uniform thickness of the first thickness T 1 ) and a second edge  32   b  (which expands from first thickness T 1  to second thickness T 2 ). The first edge  32   a  is exposed on the seal face  30 , and the second edge  32   b  is exposed on either the upper surface  22  or the lower surface  24 , depending on whether the insert belongs to the upper reinforcing arrangement  34  or the lower reinforcing arrangement  36  respectively. 
     Between adjacent brass inserts  32  a relatively thin layer of seal body  12  isometric material is disposed. This layer is about 1 mm in thickness, albeit there is some variation in the exact thickness, due to the inserts  32  being wedge shaped and the deformation mechanism described below. 
     The brass inserts  32  are disposed in a generally fan-shaped orientation, and on either side of the plurality of brass inserts  32  in each of the upper and lower reinforcing arrangements  34 , 36  are provided end inserts  38 . 
     The end inserts  38  are slightly acute L-shapes i.e. they comprise a first plate section  38   a  adjoined at an angle less than 90 degrees to a second plate section  38   b . The second plate section  38   b  is about the same length as brass inserts  38 , and the first plate section  38   b  having a shorter length. The join between first plate section  38   a  and second plate sections  38   b  is chamfered on the inner edge. There is also a inwardly curved exterior edge  38   c  orientated towards the centre of the upper and lower reinforcing arrangements  34 , 36  and therefore the approximate mid-point of the greater dimension of the seal face  30 . The particular shape and orientation of the end inserts  38  including the size and relative angle of first plate section  38  and second plate section  38   b  may be different depending on the operating parameters including the wireline size. The end inserts  38  are orientated such that both first plate section  38   a  and second plate sections  38   b  project away from the centres of the upper and lower reinforcing arrangements  34 , 36  and therefore the approximate mid-point of the greater dimension of the seal face  30 . 
     Turning to  FIGS. 7   a - 7   d , a sequence showing the deformation mechanism of the upper reinforcing arrangement  34  is depicted.  FIG. 7   d  shows the initial condition and how the inserts  32 , 38  are initially orientated within the seal body  12 . It will be noted that they are orientated in a general fan shape, but are not yet in contact with the tubular member M suspended between two seals  10 . 
       FIGS. 7   a  and  7   b  depict the reinforcing arrangement  34  when fully closed in the absence of a tubular member M. In this case the seal is required to close in a blind fashion and the reinforcing arrangement  34  is required to fully deform to close off the circular line-sized cut in the reinforcing plates  14  and  16 . The rubber between the brass inserts  32  allows them to move independently and in full compliance with the body rubber, however the general fan shape arrangement is maintained. The mating sealing face of the brass inserts  32  forms a concertina shaped face  34   a , which under actuation pressure is filled with body rubber forming a pressure tight seal against a corresponding second and opposing seal  10  in a wireline valve  5  disposed for example in a blow-out preventer (“BOP”)  7  (see, e.g.,  FIG. 6 ). 
       FIG. 7   c  shows the fully sealed position in the presence of a tubular member M that is suspended between two seals  10 , which may be any size up to and including the maximum line size made possible by the cutting of line slots in the upper and lower reinforcing plates  16  and  14  and which will usually be a metal. A reaction force F acts against the mating face  34   a  forcing it to deform around the tubular member M. The mating face  34   a  will deform into a semicircular shape, matching the shape of the tubular member M. 
     The first edges  32   a  of the inserts  32  are in metal-to-metal contact with the tubular member M. Moreover, the inwardly curved exterior edge  38   c  also abuts the tubular member M in metal-to-metal contact. The inserts  32 ,  38  form a larger and more regular fan-shape in this orientation. 
       FIG. 5  depicts the flow of the elastomeric material (rubber) from the seal body  12  is restricted in this orientation. A tendency for the rubber to flow from the seal body radially outwardly of the upper and lower reinforcing arrangements  34 , 36  towards them, causes the inserts  32 , 38  to be forced towards the tubular member M maintaining a good seal. It will be noted that the slight wedge shape of the inserts  32  mitigates any tendency for them to shear out of embedment within the rubber, and also for the rubber to flow out between the inserts  32 , 38 . 
     The relatively large contact area between the rubber and the side faces  32   e ,  38   e  ( FIG. 3 ) of the inserts  32 ,  38  mitigates this shear as well. An effect akin to aerodynamic boundary layer effect may aid in mitigating rubber flowing from the intermediate spaces between inserts  32 ,  38 . 
     Rubber flow from between the upper and lower reinforcing arrangements  34 , 36  coaxial to the tubular member M is also mitigated by the presence and orientation of the upper and lower reinforcing arrangements  34 , 36 . 
     The plates  14 , 16  on the second edges  14   b , 16   b  have semicircular channels  14   c , 16   c  formed in them. These semicircular channels  14   c , 16   c  are formed at the approximate midpoint of the second edges  14   b , 16   b , and are located both adjacent the reinforcing arrangements  34 , 36  and, in use, the tubular member M. It will be appreciated that the plates  14 , 16  have little resilience, and hence the semicircular channels  14   c , 16   c  will need to be of equal or slightly larger diameter than tubular member M to mitigate damage being caused to the tubular member M when the seal is forced into contact with it in a blowout situation. There may therefore be a slight overlap of reinforcing arrangements  34 , 36  over the steel plates  14 , 16  and the reinforcing arrangements  34 , 36  not being provided with additional reinforcement at these slight overlaps. The design of the reinforcing arrangements  34 , 36  mitigates the presence of these overlaps and the tendency of rubber to be forced outwardly from the seal body  12  between the overlap and the tubular member M, as may be prevalent in prior art designs. 
     The wedge shaped nature of the inserts  32  also restricts rubber loss through the circular cut out in the reinforcing steel plates  12  and  14 . When the seal is required to close blind as in  FIGS. 7   a  and  7   b , the inserts  32  are required to move relatively large distances towards the centre. In doing so, they will expose an increasing extrusion gap to the cut out through which rubber loss can occur rapidly, this occurs over the back end of the inserts. The wedge shape of the inserts  32  ensures that the rate of increase of area is kept to a minimum as the inserts  32  move inwardly to create a seal. 
     The reinforcing plates  16  and  14  have release agent applied locally in the area immediately adjacent to, and in contact with, the inserts  32  to ensure that the inserts are free to move with the body rubber and are not restricted by being bonded to the reinforcing plates. The freedom for the inserts  32  to move relative to the reinforcing plates  16  and  14  is critical for the function of the seal. 
     A second embodiment seal  100  is shown in  FIGS. 8-14 . Elements identical or largely similar to those described in the first embodiment are numbered similarly, albeit prefixed with a “1”, apart from as described below. 
     The main difference between first and second embodiments is the specific design of the reinforcing arrangements. 
     In the second embodiment, upper and lower reinforcing arrangements  134 , 136  comprise a plurality of brass inserts  132 . They are similarly planar, but are not wedge-shaped, they are more regular plates. 
     The seal body  112  has upper and lower notches  133 , 137  formed in it; upper notch  133  is adjacent the seal face  130  and the upper surface  122 ; whereas lower notch  137  is adjacent the seal face  130  and the lower surface  124 . The notches  133 ,  137  have a ribbed rear surface  133   a ,  137   a  i.e. the surface that is in a plane substantially parallel to the plane of the seal face  130 . The ribbing corresponds in dimension to the thickness of the brass inserts  132 . 
     The plurality of brass inserts  132  are layered in between wedge shaped rubber inserts  138 , such that the planer brass inserts  132  are arranged in a fan-shape. At either side of this arrangement are provided triangular prism shaped inserts  138   a , which impart a substantially rectangular cuboid shape to the arrangement. The brass inserts  132  are slightly longer than the rubber inserts  138 , 138   a , thus provide a cooperating ribbing surface which cooperates with ribbed rear surfaces  133   a , 137   a.    
     The operation and deformation mechanism of the second embodiment is largely identical to that of the first embodiment described above. 
     Modifications and improvements can be made to the embodiments herein before described without departing from the scope of the invention.