Patent Publication Number: US-9410400-B2

Title: Downhole completion

Description:
This application is the U.S. national phase of International Application No. PCT/EP2011/073101 filed 16 Dec. 2011 which designated the U.S. and claims priority to EP 10195577.1 filed 17 Dec. 2010, the entire contents of each of which are hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a downhole completion comprising a production casing and a sliding sleeve assembly connected as part of a production casing, comprising a tubular part and a tubular sleeve. 
     BACKGROUND ART 
     In a casing downhole, it is often necessary to pressurise the interior of the casing, or parts of it, during completion or operation of the well. 
     The interior is pressurised to expand one or more components in predetermined positions along the casing string. These components may be expandable annular barriers, rock anchors, etc. 
     Common for these components is that a high pressure is necessary to expand them. The high pressure may influence on other components and in severe circumstances in fact damage these components. 
     Therefore, these components are protected by for instance sliding elements which are adapted to be positioned in front of the components. However, since the components to be expanded require higher and higher pressure to obtain expansion, the sealing properties of the sliding elements are not sufficient to secure that the other components are not damaged. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to wholly or partly overcome the above disadvantages and drawbacks of the prior art. More specifically, it is an object to provide an improved downhole completion comprising a sliding sleeve assembly which is adapted to protect and seal an opening in a tubular section and/or a component inserted in the opening, even during high interior pressurising. 
     The above objects, together with numerous other objects, advantages, and features, which will become evident from the below description, are accomplished by a solution in accordance with the present invention by a downhole completion, comprising
         a production casing, and   a sliding sleeve assembly connected as part of a production casing, comprising:
           a tubular part forming part of the production casing and having a recess, an inner face, an opening and an axial extension, and   a tubular sleeve slidable within the recess and having an outer face and being slidable in the axial extension along the inner face between a first position, wherein fluid is allowed to flow through the opening, and a second position, wherein the fluid is hindered from flowing through the opening,
 
wherein a sealing element is arranged in connection with the sleeve at its outer face.
   
               

     In an embodiment, the opening may have a width in the axial extension and the sealing element may have a width which is larger than the width of the opening. 
     Furthermore, the tubular sleeve may have at least one circumferential groove arranged at its outer face. 
     Moreover, the sealing element may be arranged in the groove. 
     In addition, the sleeve may have at least two circumferential grooves, each groove comprising a sealing element. 
     Also, the tubular part may have a recess in which the sleeve slides. 
     In an embodiment, the opening may have a width in the axial extension and the sealing elements may be arranged with an axial distance which is larger than the width of the opening. 
     Moreover, the sealing element may be a chevron seal or an O-ring. 
     Additionally, the sleeve may have an inner face comprising indentations. 
     Furthermore, the opening may comprise a valve, such as an inflow control valve, a flow restriction, a throttle or similar restriction. 
     Also, the tubular part may have threads for connecting the tubular part with other tubular parts to form a casing. 
     The invention furthermore relates to use of the downhole completion described above in connection with a casing string in a borehole. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention and its many advantages will be described in more detail below with reference to the accompanying schematic drawings, which for the purpose of illustration show some non-limiting embodiments and in which 
         FIG. 1  shows a sliding sleeve assembly connected as part of a casing in its first and open position, 
         FIG. 2  shows the sliding sleeve assembly of  FIG. 1  in its second and closed position, 
         FIG. 3  shows another embodiment of the sliding sleeve assembly, 
         FIG. 4  shows another embodiment of the sliding sleeve assembly, 
         FIG. 5  shows yet another embodiment of the sliding sleeve assembly, and 
         FIG. 6  shows a downhole system according to the invention. 
     
    
    
     All the figures are highly schematic and not necessarily to scale, and they show only those parts which are necessary in order to elucidate the invention, other parts being omitted or merely suggested. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a partial view of a downhole completion  100  of a sliding sleeve assembly  1  connected as part of a production casing  4 . The sliding sleeve assembly  1  comprises a tubular part  2  having an inner face  3 , an opening  5  and an axial extension  28 . The tubular part  2  is connectable with other tubular parts to form a production casing or casing string. The connection between the tubular part  2  and the production casing  4  is most often a threaded connection. The sliding sleeve assembly  1  further comprises a tubular sliding sleeve  26  having an outer face  8  and being slidable in the axial extension  28  along the inner face  3  of the tubular part. In  FIG. 1 , the sliding sleeve assembly  1  is shown in a first position, wherein fluid is allowed to flow through the opening  5 , and in  FIG. 2 , the sliding sleeve assembly  1  is shown in a second position, wherein the fluid is hindered from flowing through the opening. The sliding sleeve assembly  1  further comprises a sealing element  9  arranged in connection with the sleeve in circumferential grooves  10  at the outer face  8  of the tubular sleeve  26 . 
     By having a sliding sleeve  26  in a production casing of a completion  100  or system  100 , a production section producing water can be closed off. Furthermore, such sliding sleeve can be used to protect a completion component  50  (shown in  FIGS. 4-6 ) pressurising a casing in order to expand e.g. an annular barrier. Not all components  50  can withstand the high pressure required to expand annular barriers, and thus it may be necessary to seal off these components  50  when making the completion and subsequently open them in order to use the functionality of the component  50 . 
     The sliding sleeve slides in a recess in the tubular part  2  so that the sleeve  26  does not limit the space within the casing, and thus a sliding sleeve in a recess  27  does not decrease the overall inner diameter of the tubular part  2  and thus of the casing  4 . When making the completion, it is very important that the inner diameter is not reduced unnecessarily as further components or tubulars are to pass the already installed casing  4 . 
     As can been seen in  FIG. 1 , the opening  5  has a width w o  in the axial extension of the tubular part  2 , and the sealing element  9  has a width w s  which is larger than the width of the opening. The width w s  of the sealing element  9  being larger than the width w o  of the opening  5  ensures that the sealing element does not get stuck when the sliding sleeve assembly  1  passes the opening  5 . If the sealing element  9  is smaller than the width w o  of the opening, the sealing element may get stuck at an edge of the opening  5  and be pulled up and squeezed between the outer face  8  of the tubular sleeve  26  and the inner face of a recess  27 . In this situation, the sealing element  9  is no longer able to seal off the opening  5 . 
     The sliding sleeve  26  has an inner face  15  comprising indentations  11  for moving the sleeve in the recess by means of a key tool extending into the indentations and forcing the sleeve  26  to slide axially along the inner face of the recess  27 . 
     In  FIGS. 1 and 2 , the sealing elements  9  are arranged with an axial distance between them which is larger than the width w o  of the opening  5  so that the sealing elements  9  in the second position is arranged on opposite sides of the opening  5 , thereby sealing the opening  5 . 
     In  FIG. 3 , the sliding sleeve assembly  1  comprises one sealing element  9  and one indentation  11 . The sliding sleeve assembly  1  is shown in its closed and second position. The width w s  of the sealing element  9  is more than twice the width w o  of the opening  5 , meaning that the sealing element  9  covers the opening  5  and part of the inner face of the recess  27  surrounding the opening  5  in order to seal the opening. 
     The sealing element  9  is a chevron seal in  FIGS. 1-3  and an O-ring in  FIG. 4 . The chevron seals have V-shaped parts, the tips of which point towards the outer face  8  of the sliding sleeve  26  or in the opposite direction. In  FIG. 4 , the opening  5  comprises a completion component  50 , such as a valve  13 , such as an inflow control valve, a flow restriction, a throttle or similar restriction. The sliding sleeve assembly  1  is shown in its first and open position, in which fluid may flow from the surrounding annulus or formation into the interior of the tubular part  2 . 
     The sliding sleeve assembly  1  of  FIG. 5  is shown in its second and closed position, in which fluid from the surrounding annulus or formation is hindered from entering into an interior of the production casing  4 . When the sleeve is moved to its open position, the fluid may enter from the formation into the interior of the tubular part  2  through the valve  13 . The V-shaped parts of the chevron seal point in a direction perpendicular to the direction shown in  FIGS. 1-3  and thus point in a direction along the axial extension. 
     The sliding sleeve  26  is shown in its closed position, in which fluid from the valve  13  is prevented from flowing into the production casing  4 , but also preventing the fluid in the production casing from escaping through the inflow control valve. The sliding sleeves  26  are arranged opposite the valves  13  and are slidable from an open position to a closed position, causing the sleeves  26  to slide back and forth in recesses  27  in the wall of the production casing  4  and form part of the wall thickness. 
     Having a slidable sleeve  26  opposite a valve  13  as part of a casing wall allows for closing of the sliding sleeve  26  when the production casing  4  is pressurised from within to perform an operation requiring highly pressurised fluid, such as when expanding annular barriers. When the operation requiring high pressure is finalised, the sliding sleeve  26  can be opened, and fluid from the annulus is able to flow into the production casing  4  through the valve  13 . 
     Having a sleeve sliding in a recess in the production casing  4  ensures that the inner diameter of the production casing is not decreased, which is advantageous as such a decrease may limit subsequent operations in the well. 
     In  FIG. 5 , the sliding sleeve assembly  1  comprises an inflow control valve, such as a constant flow valve. In order to control the flow, the valve comprises a spring element  12 A,  12 B. The spring element  12 A,  12 B is springy along the axial direction of the valve perpendicular to the axial extension of the production casing for providing a spring force. The housing has a seat  35  and a membrane  31 , and the spring element is a diaphragm moving towards the seat to close any valve openings  36  in the valve  13 . The spring element  12 A,  12 B comprises two spring plates, each formed as a star, arranged one on top of the other and displaced in relation to each other so that the tips of the star-shaped plates  12 A,  12 B form openings there between. When the pressurised fluid from a reservoir flows in through a screen  20  in the inlet, the fluid forces the star-shaped plates  12 A,  12 B down towards the seat  35  and the membrane  31 , thereby minimising the passage through the openings. The membrane  31  has an aperture in its centre through which the fluid passes before entering the outlet  7  and after passing the openings. 
     The tubular part  2  of the sliding sleeve assembly  1  has fastening means for being fastened to the production casing  4  and thereby form part of a production casing string. The fastening means may be threads for creating a threaded connection with the rest of the production casing  4 . 
       FIG. 6  shows a downhole system  100  comprising a casing string or production casing  4  and at least one sliding sleeve assembly  1  connected with the casing string  4 . The downhole system  100  comprises several sliding sleeve assemblies  1  along the casing string, also called the production casing. In this way, the entry of fluid from the formation can be controlled by opening and closing the sliding sleeves. Furthermore, the casing can be pressurised from within by closing the sliding sleeve assemblies  1  when performing an operation requiring high pressurised fluid to expand expandable sleeves of annular barriers or a fixation device, such as a rock anchor. 
     By fluid or well fluid is meant any kind of fluid that may be present in oil or gas wells downhole, such as natural gas, oil, oil mud, crude oil, water, etc. By gas is meant any kind of gas composition present in a well, completion, or open hole, and by oil is meant any kind of oil composition, such as crude oil, an oil-containing fluid, etc. Gas, oil, and water fluids may thus all comprise other elements or substances than gas, oil, and/or water, respectively. 
     By a production casing is meant any kind of pipe, tubing, tubular, liner, string etc. used downhole in relation to oil or natural gas production and thus the production casing is the casing in which the hydro carbons, such as oil and/or gas, flow in order to bring up oil and/or gas from the reservoir. The production casing may comprise a surface casing and a hanging casing. The sliding sleeve is used to seal off or expose an opening through which the oil and/or gas or water from the formation/reservoir could flow through, and thus closing the sleeve seals off the opening so that oil and/or gas and/or water can no longer flow into the production casing. 
     Although the invention has been described in the above in connection with preferred embodiments of the invention, it will be evident for a person skilled in the art that several modifications are conceivable without departing from the invention as defined by the following claims.