Patent Publication Number: US-9903175-B2

Title: Pressure control device

Description:
FIELD OF THE INVENTION 
     The present invention relates to a pressure control device for modulating pressure in a portion of a conduit. 
     BACKGROUND TO THE INVENTION 
     In the oil and gas exploration and extraction industries it is often desirable to be able to modulate downhole pressure when required. For example, it is desirable to isolate a section of well bore to create sections of differential pressure within the bore. A sealing device is used to create a seal within the bore, such that fluid pressure on one side of the seal increases relative to fluid pressure on the other side. Further, a temporary decrease in well pressure can be used to initiate flow from the reservoir in a process known as ‘swabbing’. One means of doing this is to make use of a swab cup, which is a cup-shaped resilient member which is lowered on a mandrel into the well. As a pressure differential develops across the cup, the walls of the cup are pushed into contact with the well tubing or bore wall, thereby sealing a portion of the well. Thus, the pressure below the cup may decrease, while the pressure above may increase. 
     Similarly-constructed pressure cups are also used in a wide variety of other sealing and fluid lifting applications. For example, variations in pressure may also be used to actuate or to control other downhole tools and instruments which rely on fluid pressure for their operation. Conventional cups are constructed with an outer diameter slightly larger than that of the bore, such that a seal is present even when the cup is not inflated. 
     Conventional pressure cups suffer from a number of disadvantages. For example, as the cup is constructed with an outer diameter slightly larger than the diameter of the bore, the cup will rub against the bore as it is run into position. This can wear the cup and may affect the formation of a seal between the cup and the bore wall. Furthermore, if the bore has restrictions which narrow the width of the bore, it may not be possible to pass the restriction without damaging the pressure cup and an alternative sealing mechanism is required. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention, there is provided a pressure control device for isolating a section of a conduit, the device comprising: 
     a support member; 
     a flexible cup member mounted to the support member; 
     a first swellable element, the first swellable element adapted, upon activation by an activation fluid, to urge a first portion of the cup member outwards into engagement with a surface of the conduit; and 
     at least one bypass arranged to permit the activation fluid to bypass the swellable element and build up behind a second portion of the cup member. 
     In an embodiment of the present invention, a pressure control device is provided in which a flexible cup member is expanded outwardly into contact with a conduit surface, such as a wellbore surface or a downhole tubular surface under the action of a swellable element. Once engaged with the surface, the fluid in the conduit can not pass by the outer edge of the cup member and is channelled, via the bypasses, to build up behind a second portion of the cup member. Using a flexible cup member permits the cup member to form an initial seal with conduits which are irregular shapes such as open hole wellbore walls, and conduits which are, for example, key seated. 
     In the preferred embodiment, the build up of fluid behind the second cup member portion creates a pressure on the second cup member portion. 
     The second cup member portion is adapted to be moved under the action of the fluid pressure into engagement with the conduit surface. In the preferred embodiment, the pressure is allowed to build up sufficiently to move the second cup member portion into engagement with the surface thereby increasing the seal with between the cup member and the wellbore or tubular surface. 
     The pressure control device may define a throughbore. 
     The pressure control device may further comprise a mandrel, the mandrel located in the device throughbore. 
     The first cup member portion is adapted to form a lip seal with the surface. 
     The at least one bypass is defined by the first swellable element. 
     Alternatively, the at least one bypass is defined by the first swellable element and the mandrel. 
     Alternatively the at least one bypass is defined by the first swellable element and the cup member first portion. 
     In one embodiment the pressure control device further comprises a mandrel. 
     In this embodiment, the at least one bypass is defined by the mandrel. 
     In one embodiment, a void is defined behind the second cup member portion by the second cup member portion and the mandrel. 
     In one embodiment, a void is defined behind the second cup member portion by the second cup member portion, the first swellable element and the mandrel. 
     In an embodiment, the void comprises at least one inlet such that fluid can flow into the void from the at least one bypass. 
     The support member is sealed to the mandrel. A seal is provided to prevent the fluid leaving the void via the interface between the support member and the mandrel. 
     The seal is located downstream of the void. 
     The seal is an o-ring seal. 
     The seal may hold pressure from one direction only. 
     The apparatus may further comprise at least one stiffening device. 
     In one embodiment, the at least one stiffening device is adapted to stiffen the walls of a bypass. If each bypass is completely or partially defined by the swellable material and/or the cup member first portion, there is a tendency for the bypass to close, either partially or completely, as the swellable element swells and pressure increases in the cup member. Stiffening devices are provided to allow the bypass to continue to function as a bypass. 
     The at least one stiffening device may define a bypass either wholly or partially. 
     The at least one stiffening device may define a bypass in combination with a mandrel. 
     The stiffening device is a length of tubular. 
     The at least one stiffening device may extend the full height of the first swellable element. 
     The apparatus may comprise at least one anti-extrusion device. An anti-extrusion device is provided to prevent the first swellable element from swelling in an axial direction, thereby increasing the swell in a radial direction towards the cup member first portion. 
     In one embodiment there is a first anti-extrusion device preventing swelling in a first axial direction. 
     In an alternative or additional embodiment there is a second anti-extrusion device preventing swelling in a second axial direction, opposite the first axial direction. 
     In this embodiment the anti-extrusion devices are connected. 
     The anti-extrusion devices are connected by a connecting member. 
     The connecting member may wholly or partially define the at least one bypass. 
     The connecting member may define the at least one bypass in combination with a mandrel. 
     The anti-extrusion devices may define access means to permit the fluid to access the first swellable element. 
     The anti-extrusion devices may be attached to a mandrel. Attaching the anti-extrusion devices to a mandrel is preferred to attaching them directly to the swellable element, as attaching the anti-extrusion devices to the swellable element may inhibit swelling of the element. 
     The anti-extrusion devices may be rings. 
     The connecting member is a tubular. 
     The first swellable element may comprise ethylene propylene rubber, polyacrylic rubber, polyethers, acrylate polymers, tetra fluoro ethylene-propylene and/or hydrogenated nitrile rubber or any suitable compound. 
     The first swellable element may define the first cup member portion. 
     Alternatively the first cup member portion may comprise a different material. 
     In one embodiment the first cup member portion may comprise a swellable material. 
     The first cup member portion may comprise an elastomer. 
     The first cup member portion may comprise a rubber. 
     The pressure control device may further comprise a second swellable element, the second swellable element adapted, in use, to urge the second cup member portion outwards into engagement with the surface. 
     The second swellable element may swell at a slower rate than the first swellable element. Such an arrangement permits the first swellable element to swell the first cup member portion into engagement with the surface and form a lip seal before the second swellable element swells the second cup member portion into engagement with the surface. 
     In one embodiment the second cup member portion may comprise a swellable material. 
     The second cup member portion may comprise an elastomer. 
     The second cup member portion may comprise a rubber. 
     The activation fluid is water, oil or solvent or any suitable fluid. 
     The first swellable element is glued or bonded to the first cup member portion. 
     Alternatively, the first swellable element is separate from the first cup member portion. 
     The/each bypass is parallel to the direction of fluid flow. Such an arrangement minimises the length of flow path the fluid must travel to reach the second cup member portion. 
     The flexible cup member may comprise a back-up. A back-up is provided to prevent the cup member extruding down or along the conduit under the action of the applied pressure. 
     In one embodiment the back-up could be a garter spring. 
     In an alternative embodiment the back up could be a plurality of overlapping petals, a wire mesh, a continuous ductile ring, a portion of harder material adapted to resist the pressure or any suitable device or mechanism. 
     According to a second aspect of the present invention there is provided a method of isolating a section of a conduit, the method comprising the steps of: 
     positioning a pressure control device in a conduit; 
     activating a first swellable element under the action of an activation fluid such that the first swellable element urges a first portion of a control device flexible cup member outwards into engagement with a surface of the conduit to form a lip seal with said surface of the conduit; 
     providing a bypass such that the activation fluid can bypass the swellable element to build up behind a second portion of the cup member. 
     According to a third aspect of the present invention, there is provided a system for isolating a section of a conduit, the system comprising a plurality of pressure control devices, each device comprising: 
     a support member; 
     a flexible cup member mounted to the support member; 
     a first swellable element, the first swellable element adapted, upon activation by an activation fluid, to urge a first portion of the cup member outwards into engagement with a surface of the conduit; and 
     at least one bypass arranged to permit the activation fluid to bypass the swellable element and build up behind a second portion of the cup member. 
     In one embodiment at least one of the cups faces in a first direction and, at least one of the cups faces in a second direction, the second direction being opposite the first direction. Such an arrangement permits pressure to be held from both ends or sides of the system. 
     Alternatively or additionally, there are a plurality of the pressure controlled devices facing the same direction. Such an arrangement allows improved pressure containment and provides redundancy in the system in the event that one of the cups fails or leaks. 
     It will be understood that the features of one aspect of the invention is equally applicable to other aspects and have not been repeated 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 section view of a pressure control device according to a first embodiment of the present invention; 
         FIG. 2  is a section view of the pressure control device of  FIG. 1  shown mounted on a mandrel; 
         FIG. 3  is a top view of the pressure control device of  FIG. 1 ; 
         FIG. 4  is a section view of part of the pressure control device of  FIG. 1  shown in a run in configuration in a wellbore; 
         FIG. 5  is a section view of part of the pressure control device of  FIG. 1  shown in a partially set configuration in a wellbore; 
         FIG. 6  is a section view of part of the pressure control device of  FIG. 1  shown in a fully set configuration in a wellbore; 
         FIG. 7  is a section view of a pressure control device according to a second embodiment of the present invention; 
         FIG. 8  is a section view of a pressure control device according to a third embodiment of the present invention; 
         FIG. 9  is a section view of a pressure control device according to a fourth embodiment of the present invention; 
         FIG. 10  is a section view of a pressure control device according to fifth embodiment of the present invention; and 
         FIG. 11  is a section view of a pressure control device according to a sixth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Reference is firstly made to  FIGS. 1 and 2 .  FIG. 1  is a section view of a pressure control device, generally indicated by reference numeral  10 , according to a first embodiment of the present invention and  FIG. 2  is a section view of the pressure control device  10  of  FIG. 1  shown fitted to a mandrel  12 . The pressure control device  10  is arranged to hold a pressure from above and comprises a soft rubber flexible cup member  14 , mounted and bonded to a steel support member  16 . The pressure control device  10  further comprises a first polyether swellable element  18 , adapted, in use, to urge a first portion  20  of the cup member  14 , upon activation, outwards (in the direction of arrows “A”) into engagement with a surface (not shown). 
     The pressure control device  10  further comprises four bypasses  22 , of which three  22   a - c  are shown on  FIG. 1 , arranged to permit a fluid to bypass the swellable element  18  and build up in a void  46  behind a second portion  24  of the cup member  14 . An o-ring seal  50  seals the interface between the support member  16  and the mandrel  12 , preventing fluid leaking out of the void  46  (best seen in  FIG. 2 ). 
     An anti-extrusion back-up  26  of nitrile rubber is also provided on the cup member  14  to prevent the soft rubber flexible cup member  14  from extruding downwards when exposed to a pressure from above. The anti-extrusion back-up  26  is biased to the position shown in  FIGS. 1 and 2  by an annular spring  28 . This will be discussed in greater detail in due course. 
     Referring to  FIG. 3 , a plan view of the pressure control device  10  of  FIG. 1 , and to  FIG. 2 , each of the four bypasses  22  are defined by the mandrel  12  and the first swellable element  18 . The portion of each bypass  22  defined by the swellable element  18  is lined by a stiffening device  60 , shown only in connection with the first bypass  22   a  on  FIG. 3 . The stiffening devices  60  line the entire surface of the bypasses  22  and are in contact with the mandrel  12  preventing extrusion of the swellable element  18  into the bypasses  22 . The semi-circular section of the stiffening devices  60  helps resist crushing by the swellable material. 
     The operation of the pressure control device  10  will now be described with reference to  FIGS. 4, 5 and 6 , section views of part of the pressure control device  10  of  FIG. 1  in a run-in configuration ( FIG. 4 ), a partially set configuration ( FIG. 5 ) and a fully set configuration ( FIG. 6 ). 
     In  FIG. 4  the pressure control device  10  has been run into a wellbore  40  defining a wellbore surface  42 . Water (W) is pumped down the wellbore  40  and comes into contact with the pressure control device  10 . As can be seen, the water flows down the bypasses  22  into the void  46  between the cup member second portion  24  and the mandrel  12 , and down an annulus  44  between the pressure controlled device  10  and the wellbore surface  42 . 
     The swellable material in the first swellable element  18  is activated by contact with water and, referring to  FIG. 5 , the water causes the swellable element  18  to swell up, pushing the first cup member portion  20  into contact with, and form a lip seal with, the wellbore surface  42 . 
     Once the cup member  14  has formed a lip seal with the wellbore surface  42 , the fluid path down the annulus  44  is closed and pressure builds up in the void  46  beneath the swellable element  18 . The pressure is held by the o-ring seal  50  which prevents leakage between the steel support member  16  and the mandrel  12 . 
     Pressure begins to build up in the void  46 , forcing the cup member second portion  24  into engagement with the wellbore surface  42 . The anti-extrusion back-ups  26  and the annular spring  28  also rotate outwards against the bias of the annular spring  28  preventing extrusion of the flexible cup member  14  down the annulus  44 , and maintaining the integrity of the cup member  14 . Continued application of pressure on the pressure control device  10  from above will maintain the seal and energise the pressure control device  10  to hold the pressure. 
     Referring now to  FIG. 7 , a pressure control device  110  is shown in accordance with the second embodiment of the present invention. This pressure control device  110  is similar in most respects to the pressure control device  10  of the first embodiment, however the pressure control device  110  of the second embodiment includes an anti-extrusion ring  170  mounted to an upper surface of the swellable element  118  to prevent the swellable element  118  from swelling in an upward (axial) direction, therefore increasing the swell in the radial direction. 
     A first portion  180  of the anti extrusion device  170  is glued or otherwise bonded to an upper surface  172  of the swellable element  118  and a second portion  182  is glued or otherwise bonded and sandwiched between the cup member first portion  120  and the swellable material  118 . The device upper portion  180  defines a plurality of holes (not visible) to permit the swelling fluid to contact the upper surface of the swellable element  118 . It is believed that the upper surface of the swellable element, is where the most swelling occurs. 
       FIG. 8  shows a pressure control device  210  according to a third embodiment of the present invention. In this embodiment, the bypasses  222  are wholly defined by the swellable element  218 . In the embodiment shown in  FIG. 8 , the bypasses  222  are circular in cross section and moulded into the swellable element  218  during manufacture. 
       FIG. 9  shows a fourth embodiment of the present invention. In this embodiment, the pressure control device  310  includes a swellable element  318  which also defines the cup member first portion  320 . In essence the cup member first portion  320  is moulded from a swellable material. In addition the second portion  324  of the flexible cup member  314  is also moulded from a swellable material. In this embodiment, the second portion swellable material  324  swells at a slower rate than the first portion swellable material  318  and is believed the use of a swellable material in this way can improve the seal. 
       FIG. 10  shows a pressure control device  410  according to a fifth embodiment of the present invention. In this embodiment, there are upper and lower anti-extrusion devices in the from of rings  470   a ,  470   b . These anti-extrusion rings  470  are attached to the mandrel  412  rather than the swellable element  418  so that swelling of the element  418  is not inhibited in the radial direction by bonding between the rings  470  and the swellable element  418 . 
       FIG. 11  shows a pressure control device  510  according to a sixth embodiment of the present invention. In this embodiment, rather than being attached to a mandrel, the upper and lower anti-extrusion rings  570   a ,  570   b  are attached to a tubular connecting member  590 . The connecting member  590  permits positioning of the anti-extrusion rings  570  above and below the swellable element  518  without the need to bond the anti-extrusion rings  570  to the swellable element  518 . The combination of the anti-extrusion rings  570  and the connecting member  590  prevents the swellable element  518  swelling in any direction other than radially outwardly, towards the cup member first portion  520 , thereby maximising the effect of the swellable element  518 . 
     The connecting member  590  partially defines the bypasses  522 , the bypasses  522  being wholly defined by the connecting member  590  and a mandrel (not shown). 
     In the embodiments of  FIGS. 10 and 11 , the anti-extrusion devices  470 ,  570  and where applicable the connecting member  590  define apertures to allow the fluid to access the swellable element  418 , 518  to swell the element  418 , 518 . 
     Various modifications and improvements can be made to the above described embodiment without departing from the scope of the present invention. For example, although the bypasses are shown as being defined by the swellable element alone or the swellable element in conjunction with a mandrel, they could be defined by the swellable element in conjunction with the flexible cup member. 
     Additionally it will be understood that although the pressure control device is shown holding pressure from above, it will be understood that the control device could be inverted to hold pressure from below, or the device could be one of a plurality of devices, arranged in series, to hold pressure from one direction or facing in opposite directions to hold pressure from above and below. 
     Furthermore it will also be understood that although a hard rubber back-up is used in the embodiments described, an overlapping petal arrangement of back-up could also be used.