Patent Publication Number: US-9896900-B2

Title: Sealing apparatus

Description:
FIELD OF THE INVENTION 
     The present invention relates to an apparatus for sealing a well bore, particularly, but not exclusively, the present invention relates to a high temperature and/or expansion sealing apparatus. 
     BACKGROUND TO THE INVENTION 
     In many downhole environments, packers or similar sealing devices are used to seal sections of the well bore so that, for example, hydrocarbons can be extracted from a well bore section into the production tube without leakage up or down the annulus between the well bore surface and the production tube. 
     Elastomeric seal elements are widely used in conventional packers as they are relatively easy to manipulate and have good sealing properties once engaged with a well bore surface. A conventional packer is also often provided with one or more seal back-ups to prevent extrusion of the elastomeric sealing element in the annulus when the sealing apparatus is under pressure. 
     However, the mechanical properties of elastomers can deteriorate as pressure and/or temperature increases. The performance of these conventional packers are also affected when, in addition to the high pressure and/or high temperature environment, the seal has to seal across a large annulus. These high expansion seals are particularly vulnerable in the aggressive environments described. 
     There is a desire within the oil industry to operate in high temperature and high pressure environments, and there is need for a sealing apparatus which can operate successfully in these environments, particularly a high expansion sealing apparatus. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention there is provided a sealing apparatus for sealing a well bore, the sealing apparatus comprising: 
     a sealing element adapted to be moved from a run-in configuration to a set configuration; 
     a first back-up layer; and 
     at least one second back-up layer sandwiched between the sealing element and the first back-up layer, the first back-up layer and the at least one second back-up layer being adapted to be moved from the run-in configuration to the set configuration under the action of the sealing element; 
     wherein the at least one second back-up layer comprises a thinner material than the first back-up layer. 
     In one embodiment, providing a second back-up layer of a thinner material than the first back-up layer facilitates the expansion of the back-up system as the sealing element moves from the run-in configuration to the set configuration. This is of particular importance in environments in which sealing apparatus has to seal across a large annular gap. Furthermore, use of a thinner material which is easier to bend will result in a reduced level of stress being built up in the sealing element during deployment. This is advantageous because stress can have a detrimental effect on the mechanical properties of the element. 
     Preferably, the first and second back-up layers are annular. 
     Preferably, the first back-up layer comprises a slotted portion. 
     Preferably, the first back-up layer is slotted to form discrete petals. A back-up layer which is slotted to form “petals” can expand greater distances than a non-slotted layer and permits the material to expand without elongation. Furthermore, a slotted first back-up layer will expand more easily than a continuous layer resulting in lower stress levels in the sealing element. The second layer of the thinner material has further advantages with a slotted first back-up layer. As the first back-up layer expands, the slots open up and a thinner second back-up layer can form into the gaps between the first back-up layer petals to remove any clearances between the first and second back-up layers and any curvature mismatches between the first back-up layer and the bore wall. Removal of these clearances and mismatches is important, since the properties of some sealing elements, for example rubber elements, are very poor at very high temperatures, i.e. around 200° C. At this temperature, rubber can extrude through any clearances in the back-up layers or between the apparatus and the bore wall. The first back-up layer is the primary structural layer supporting the sealing element. The second back-up layer is provided to fill the gaps inbetween the petals of the first back-up layer and to resist extrusion of the sealing element, in use, between the apparatus and the well bore. 
     Preferably, the first back-up layer comprises a non-slotted portion. 
     Preferably, the first back-up layer comprises a deformable material. 
     In one embodiment the deformable material is ductile. 
     Preferably, in use, the first back-up layer, in the run-in configuration, is adapted to engage the bore wall. This permits the first back-up layer, in use, to be pinned to the well bore surface by friction once the sealing apparatus is set. This method of constraint removes any shear loading applied to the first back-up layer, which in turn allows for a thinner section to be used. A thinner section reduces the stress imparted into the sealing element as the sealing element moves into the set configuration, and once fully deployed. 
     Preferably, the first back-up layer comprises a bore engaging surface. 
     Preferably, in use, more than 50% of the bore engaging surface is, in use, engaged with the bore surface in the set configuration. Such an arrangement ensures that the axial load applied to the sealing element, in use, is not sufficient to overcome the radial load maintaining the sealing apparatus in contact with the bore wall. 
     Preferably, in use, more than 50% of the slotted portion surface is, in use, engaged with the bore surface in the set configuration. 
     Preferably, the bore engaging surface comprises relatively high friction co-efficient. 
     Preferably, the bore engaging surface defines a relatively high friction co-efficient surface profile. 
     Alternatively or additionally, the bore engaging surface comprises a coating of a relatively high friction coefficient material. 
     Preferably, the/each second back-up layer is a ductile material. Providing a ductile layer, which can form and adapt in shape, minimises the stress imparted to the seal element as the seal apparatus sets and is adapted to mould, when used with a slotted first back-up layer, into gaps between adjacent first back-up layer petals. 
     Preferably, the ductile material is stainless steel. 
     In one embodiment, the/each second back-up layer comprises a plurality of back-up layers. 
     Preferably, the first back-up layer has an upper edge. 
     Preferably, the first back-up layer upper edge is chamfered. 
     Preferably, the upper edge, in use, is chamfered towards the bore wall. A chamfered edge will more easily deform into a close engagement with the bore wall reducing the possibility of clearances between the first back-up layer and the bore wall opening up. 
     Preferably, where the first back-up layer defines discrete petals, each petal has side edges. By side edges it is meant edges which lie in a direction parallel to the longitudinal axis of the sealing apparatus. 
     Preferably, the side edges are chamfered. 
     Preferably, the side edges are, in use, chamfered towards the bore wall. 
     Preferably, the at least one second back-up layer has an upper edge. 
     Preferably, the at least one second back-up layer upper edge is chamfered. 
     Preferably, the at least one second back-up layer upper edge extends above the first back-up layer upper edge. As the second back-up layer is of a thinner material to the first back-up layer, the/each second back-up layer will more easily deform into engagement with the well bore surface, in use, closing any clearances between the apparatus and the well bore and to remove any mismatches between the apparatus and the bore internal diameter. The removal of clearances is important as, at high temperatures, sealing elements made of elastomeric materials can extrude through the clearances. 
     In an alternative embodiment, the first back-up layer upper edge extends above the at least one second back-up layer upper edge. As the side edges are less exposed than the upper edge, it is possible to make the edge of the side edge chamfers sharper as they are not as exposed as the upper edge. A sharp edge can form a tighter fit with the at least one second back-up layer minimising the possibility of clearances between the first back-up layer and the bore wall opening up. 
     Preferably, each of the plurality of second back-up layers comprises a slotted portion. Having slotted second back-up layers also provides for additional expansion. If the back-up layers are slotted, the provision of multiple second layer will ensure that gaps between the adjacent petals of the first back-up layer are filled. 
     In one embodiment, each of the second back-up layers comprises fewer slots than the first back-up layer. 
     Preferably, at least one second back-up layer has a sealing element engaging surface. 
     Preferably the/each sealing element engaging surface comprises a low friction coating. A low friction coating reduces the stresses imparted into the element material during deployment and under pressure. 
     Preferably, the first and second back-up layers deform under the action of the sealing element. 
     In one embodiment, the back-up layers plastically deform. Plastic deformation reduces the stresses imparted to the sealing element by the back-up layers once the sealing apparatus is set. 
     In an alternative embodiment, the back-up layers elastically deform. Elastic deformation allows the back-up layers to at least partially recover to the run-in configuration when it is desired to retrieve the sealing apparatus. 
     In one embodiment a first back-up layer upper portion is bent inwards towards a sealing apparatus longitudinal axis. Having the upper portion of the first back-up layer facing radially inwards, biases the first back-up layer to a run in configuration such that the first back-up layer at least partially recovers to the run-in configuration when it is desired to retrieve the sealing apparatus. Such an arrangement is most effective in an apparatus in which the first back-up layer upper edge extends above the at least one second back-up layer upper edges. 
     Preferably, the sealing apparatus further comprises a ring member. 
     Preferably, the ring member is attached to a lower portion of the first back-up layer. A ring member is provided to withstand the hoop stress imparted to the back-up layers by the differential pressure held by the sealing element. 
     Preferably, the ring member is separate to the first and second back-up layers. The use of a separate ring member to the first and second back-up layers means that the back-up layers can be of substantially constant cross-sections. The use of a constant cross-section material, particularly for the first back-up layer, helps reduce stress concentrations in the first back-up layer and enables a relatively thin section to be used. A thin section will bend more easily and will reduce the stress imparted into the sealing element. 
     Preferably, the first back-up layer lower portion is received within the ring member. 
     Preferably, the ring member is attached to the non-slotted portion of the first back-up layer. 
     Preferably, the interface between the slotted and non-slotted portions of the first back-up layer is received within the ring member. 
     Preferably, the ring member is connected to an external surface of the first back-up layer lower portion. 
     Preferably, the/each second back-up layer is connected to the ring member. 
     Preferably, the ring member defines a profiled surface. 
     Preferably, as the sealing apparatus moves from the run-in configuration to the set configuration, the first back-up layer bends around at least a portion of the profiled surface. 
     In one embodiment, at least a portion of the first back-up layer, in the run-in configuration is displaced from the ring member profiled surface. 
     Preferably, in this embodiment, the ring member profiled surface tapers axially away from the first back-up layer in the run-in configuration. 
     In one embodiment the first back-up layer comprises spring steel. Spring steel can be used to assist in returning the sealing apparatus to the run-in configuration when it is desired to recover the sealing apparatus from downhole. 
     The sealing element may comprise a packing element, a cup, an expandable element, a swellable element, an inflatable element or any suitable style of element. 
     Preferably, in the run-in configuration, the maximum diameter defined by the back-up layers is no more than the maximum diameter defined by the ring member. 
     Preferably, the sealing apparatus further comprises an intermediate layer between the first back-up layer and the/each second back-up layer. 
     Preferably the intermediate layer extends above and below a first back-up layer upper edge. 
     Preferably the intermediate layer comprises a strong flexible material. 
     Most preferably the intermediate layer comprises a woven steel mesh. Using a flexible layer such as a woven steel mesh further minimises the existence of gaps between the first and second back-up layers in the set configuration. The flexible material fills up any gaps which may exist between the first and second back up layers. 
     Preferably the intermediate layer is thinner than either or any of the first and second back-up layers. 
     In one embodiment the intermediate layer wraps over an upper edge of the/each second back-up layer. 
     In an alternative embodiment the intermediate layer wraps over the upper edge of the first back up layer. 
     According to a second aspect of the present invention, there is a sealing apparatus for sealing a well bore, the sealing apparatus comprising: 
     a seal element adapted to move from a run-in configuration to a set configuration; 
     at least one back-up layer, the/each back-up layer being adapted to be moved from the run-in configuration to the set configuration under the action of the sealing element; and 
     a ring member; 
     wherein a portion of the/each back-up layer is received inside the ring member, the ring member and/each back-up layer being separate components. 
     Preferably, at least one of said back-up layers is of substantially constant cross-section. 
     According to a third aspect of the present invention, there is provided a sealing apparatus for sealing a well bore, the sealing apparatus comprising: 
     a seal element adapted to be moved from a run-in configuration to a set configuration; and 
     at least one back-up layer, the/each back-up layer being adapted to be moved from the run-in configuration to the set configuration under the action of the sealing element; 
     wherein at least one of said back-up layers comprises a resilient material, said resilient material being biased to the run-in configuration. 
     According to a fourth aspect of the present invention there is provided a sealing apparatus for sealing a well bore, the sealing apparatus comprising: 
     a sealing element adapted to be moved from a run in configuration to a set configuration; 
     a first back-up layer; 
     at least one second back-up layer located between the sealing element and the first back-up layer, and 
     an intermediate layer sandwiched between the first back-up layer and the at least one second back-up layer, the first back-up layer, the intermediate layer and at least one second back-up layer being adapted to be moved from the run-in configuration to the set configuration under the action of the sealing element. 
     It will be understood that features of one aspect may be equally applicable to the other aspects and are not listed for brevity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will now be described with reference to the accompanying drawings in which: 
         FIG. 1  is a perspective of a sealing apparatus in a run-in configuration according to a first embodiment of the present invention; 
         FIG. 2  is a section view of the apparatus of  FIG. 1 ; 
         FIG. 3  is an exploded view of the apparatus of  FIG. 1 ; 
         FIG. 4  is a section view of the apparatus of  FIG. 1  in a set configuration; 
         FIG. 5  is a perspective of a high expansion sealing apparatus in a run-in configuration according to a second embodiment of the present invention; 
         FIG. 6  is a section view of the apparatus of  FIG. 5 ; 
         FIG. 7  is an exploded view of the apparatus of  FIG. 5 ; 
         FIG. 8  is a section view of the apparatus of  FIG. 5  in a set configuration; 
         FIG. 9  is a perspective of a retrievable sealing apparatus in a run-in configuration according to a third embodiment of the present invention; 
         FIG. 10  is a section view of the apparatus of  FIG. 9 ; 
         FIG. 11  is a section view of the apparatus of  FIG. 9  in a set configuration; 
         FIG. 12  is a perspective view of the apparatus of  FIG. 9  in a set configuration; 
         FIG. 13  is a section view of part of a retrievable sealing apparatus according to a fourth embodiment of the present invention; 
         FIG. 14  is an exploded view of the apparatus in  FIG. 13 ; and 
         FIG. 15  is a section view through part of a sealing apparatus according to a fifth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Reference is firstly made to  FIGS. 1, 2 and 3  which show views of a sealing apparatus, generally indicated by reference numeral  10 , in a run-in configuration according to a first embodiment of the present invention. 
     The sealing apparatus  10  comprises a sealing element  12  (only shown in  FIG. 2  for clarity), the sealing element  12  adapted to be moved from the run-in configuration shown in  FIGS. 1, 2 and 3  to a set configuration shown in  FIG. 4 . The sealing apparatus  10  further comprises a first back-up layer  14 , a second back-up layer  16  and a ring member  20 . The second back-up layer  16  is sandwiched between the sealing element  12  and the first back-up layer  14 . 
     The second back-up layer  16  is pressed from annealed stainless steel sheet and is 0.5 mm thick. This is considerably thinner than the first back-up layer  14  which is machined from solid bar to a wall thickness of 2 mm. The thinness of the second back-up layer  16  facilitates the expansion of the back-up layers  14 , 16  as the sealing element  12  moves from the run-in configuration to the set configuration. 
     As can be seen from  FIGS. 1 to 3 , an upper portion  22  of the first back-up layer  14  is slotted to form a number of discrete petals  24 . The petals  24  permit the first back-up layer  14  to expand as the sealing element  12  moves from the run-in configuration to the set configuration more easily. As the first back-up layer  14  expands, the slots  26  defined by the first back-up upper portion  22  will open up leaving gaps. In the set configuration each of these gaps is filled by a petal  34  defined by the second back-up layer  16 . The thinness of the second back-up layer  16  and ductility of the material, permits the second back-up layer  16  to be bent into the gaps formed by the opening of the slots  26  in the first back-up layer  14  ensuring that the back-up layer  14 , 16 , once expanded to the set configuration, make a continuous surface. 
     Referring particularly to  FIGS. 1 and 2 , it will be noted that the tips  44  of the second back-up layer petals  34  extend above the tips  42  of the first back-up layer petals and both sets of tips  42 , 44  are chamfered. The tips  42 , 44  are chamfered to allow them to deform into engagement with the bore wall and close up any clearances between the apparatus and the bore wall. The second back-up layer tips  44  are of a thinner material than the first back-up layer tips  42  and are therefore more deformable. For this reason the second back-up layer tips  44  extend above the first back-up layer tips  42  to close any clearances between the first back-up layer and the bore wall and any clearances between the first and second back-up layers  14 , 16  into which the sealing element  12  could extrude. 
     As can be seen from  FIG. 1 , the slots  36  between adjacent second back-up layer petals  34  are considerably bigger than those defined in the first back-up layer  14 . This design of the second back up layer  16  is such that the petals  34  have sufficient width to fill the gaps between the adjacent petals  24  but are as narrow as possible to assist deformation. The internal surface  38  of the second back-up layer has a low coefficient of friction coating applied to prevent damage to the sealing element  12  as the sealing apparatus  10  sets. 
     The ring member  20  is provided as a separate component to the back-up layers  14 , 16 . During assembly the back-up layers  14 , 16  are slid inside the ring member  20 . The seal element  12  is bonded to the ring member  20 , trapping the back-up layers between the sealing element  12  and the ring member  20 . 
     The ring member  20  defines a profiled surface  40  which the back-up layers  14 , 16  bend around under the action of the sealing element  12  as the sealing apparatus  10  moves from the set configuration to the run-in configuration. As will be clear from  FIG. 3 , once assembled, the bottom  39  of the slots  26  will be received within the ring member  20  and will be engaged with the profiled surface  40 . The ring member  20 , during deployment of the first back-up layer  14 , will support the first back-up layer and will help reduce stress concentrations within the first layer  14 . The ring member  20  also enables a relatively thin section to be used for the first back-up layer  14  and permits the first back-up layer  14  to be of constant cross-section for the majority of its length reducing the likelihood of stress concentrations forming. 
     Referring now to  FIG. 4 , the sealing apparatus  10  is fully expanded and the first back-up layer external surface  28  is engaged with the bore wall  50 . The first back-up layer external surface  28  defines a profile having a high coefficient of friction to improve the grip between the apparatus  10  and the bore wall  50 . As can be seen, more than 50% of the first back-up layer slotted portion surface  28  is engaged with the bore wall  50 . This degree of surface area contact ensures that the friction between the surface  28  and the bore wall  50  is sufficient to resist the axial load applied to the first back-up layer  14  by the well pressure, preventing the first back-up layer from being subjected to shear and bending loads adjacent the ring member tip  80 . 
     As can be seen from  FIG. 4 , the back-up layers  14 , 16  have bent around the ring member profile  40  into engagement with the bore wall  50 . The second back-up layer petals  34  have filled the openings in the slots  26  of the first back-up layer  14  to provide a continuous surface engaged with the bore wall  50 , preventing extrusion of the sealing element (not shown) down the annulus  52  between the apparatus  10  and the bore wall  50 . 
     Reference is now made to  FIGS. 5, 6, 7 and 8  which show a sealing apparatus  110  according to a second embodiment of the present invention. The sealing apparatus  110  is a high expansion sealing apparatus for expanding across a larger annulus. In this apparatus, the first back-up layer  114  comprises many more petals  124  than the first back-up layer  14  of the first embodiment. These narrower petals  124  will expand further without imparting excessive stress to the sealing element  112  (shown in  FIG. 8 ). In addition, the use of narrower petal will reduce the size of the gaps between petals once the petals are expanded. As the first back-up layer  14  is the primary structural layer, the use of narrower petals and hence a greater number of slots ensures that the second back-up layers  116  are more evenly supported which in turn means the second back-up layers  116  can be thinner and more flexible. 
     In the second embodiment, the sealing apparatus  110  comprises two back-up layers  116   a , 116   b . Each second back-up layer  116   a , 116   b  is pressed from annealed stainless steel sheet. In this embodiment, two back-up layers  116  are required to fill the significant increase in the number of narrower gaps between adjacent petals  124  as the first back-up layer  114  expands. The second back-up layers  116  of this embodiment are thinner than the second back-up layer  16  of the first embodiment to compensate for the additional stiffness which arises by using wider petals  134 . 
     Referring now to  FIGS. 9, 10, 11 and 12 , these Figures show a sealing apparatus  210  according to a third embodiment of the present invention. The second back-up layer and the sealing element of this embodiment are not shown on the Figures for clarity. 
     The sealing apparatus  210  is a retrievable apparatus and the first back-up layer  214  is manufactured from spring steel. The first back-up layer  214  is biased towards the run-in configuration shown in  FIGS. 9 and 10 . The other difference between this and the apparatus of the first embodiment is that the profiled surface  240  of the ring member  220  includes a tapered portion  260  which tapers away from back-up layer  214  in the run-in configuration. As the sealing element expands, the first back-up layer  214  bends around the profiled surface  240  into engagement with the bore wall  250  (shown in  FIG. 11 ). During this expansion, the first back-up layer  214  is deformed within its elastic limit. When the pressure used to set the apparatus  210  is removed the spring steel first back-up layer  214  will recover at least partially to the run-in configuration permitting the apparatus  210  to be recovered to surface. 
     In addition, the first back-up layer petal tips  242 , in the run-in configuration, are bent slightly radially inwards to facilitate recovery to the run-in configuration. 
     Reference is now made to  FIGS. 13 and 14  which show views of a retrievable sealing apparatus  310  according to a fourth embodiment of the present invention. 
     The sealing apparatus  310  comprises a sealing element  312 , the sealing element  312  adapted to moved from the run-in configuration shown in  FIGS. 13 and 14  to a set configuration in which the sealing element  312  is engaged with a conduit wall (not shown). The sealing apparatus  310  further comprises a first back-up layer  314 , a second back-up layer  316  and a ring member  320 . As can be seen from  FIG. 13  in particular, the second back-up layer  316  is considerably thinner than the first back-up layer  314 . 
     Other features of note in this embodiment is the upper portion  322  of the first back-up layer  314  which includes a radially inward facing portion  360 . This radially inward facing portion  360  facilitates recovery of the first back up layer  314  from the extended configuration in which the first back-up layer  314  and the sealing element  312  are in contact with the conduit wall to the run-in configuration shown in  FIG. 13 , in which the maximum external diameter of the first back-up layer  314  and the seal element  312  is less than the maximum external diameter of the ring member  320  permitting the sealing apparatus  310  to be recovered from a downhole location. Even in the extended configuration (not shown), the diameter defined by the tip  362  of the first back-up layer  314  is less than the maximum external diameter of the ring member  320 . 
     It will also be noted that the first back-up layer  314  extends above an upper edge  364  of the second back-up layer  316 . To ensure tight fit between the first and second back-up layers  314 ,  316  and to eliminate any extrusion gaps, the side edges  366  ( FIG. 14 ) of the petals  324  are chamfered. As the side edges are partly concealed, if the gap between adjacent petals  324  is small enough, the petal chamfered side edges  366  can be relatively sharp facilitating a better fit, and consequently reduced gaps, between the first and second back-up layers  314 ,  316  in the extended configuration. The second back-up layer  316  can better mould around a sharp edge as provided for by the chamfered side edge  366 . 
     Referring finally to  FIG. 15 , this figure shows a section view of part of a sealing apparatus  410  according to a fifth embodiment of the present invention. This sealing apparatus  410  includes a sealing element (not shown) similar to the sealing element  12  of the first embodiment, a first back-up layer  414 , a second back-up layer  416  and a ring member  420 . The sealing apparatus  410  further comprises an intermediate layer  470  which is sandwiched between the first and second back-up layers  414 ,  416  and wraps over the top of and down the inside of the second back-up layer  416 . 
     The intermediate layer  470  is a woven steel mesh and is made from a sheet which is formed into a sleeve and spot welded to the first back-up layer  414 . As the sealing apparatus  410  expands from the run-in configuration (not shown) to the set configuration (shown in  FIG. 14 ) the intermediate layer  470  moulds itself into any remaining extrusion gaps between the first and second back-up layers  414 ,  416  providing an extremely reliable back-up to the sealing element. 
     Various modifications and improvements can be made to the above described embodiment without departing from the scope of the present invention. For example, for low expansion environments it is not necessary to have the first and/or second back-up layers slotted, continuous banded material could be used. In an alternative embodiment, where there are two second back-up layers used, the tips of the inner back-up layer could extend above the tips of the outer back-up layer, which in turn extend above the tips of the first back-up layer. This further facilitates the closing of any gaps or clearances between the apparatus and the well bore surface.