Abstract:
An apparatus and method, particularly useful for isolating zones in a hydrocarbon wellbore. The apparatus includes a tubular section, such as a length of casing or liner tubular, arranged to be run into and secured within the wellbore which may be open hole or already cased. At least one sleeve member is positioned on the exterior of the tubular section and is sealed thereto. A pressure control device, which typically consists of a pressurised hydraulic fluid delivery device, can be used to increase the pressure within the sleeve member to cause the sleeve member to move outwardly and bear against an inner wall of the wellbore.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to apparatus and methods for securing a tubular within another tubular or borehole, isolating an annulus or centralising sections of pipe. In particular the invention has application for centralising and/or securing a casing tubular or liner tubular within another casing section, liner section or open borehole in an oil, gas or water well and for isolating a portion of a borehole located below the apparatus from a portion of the borehole located above the apparatus.  
       BACKGROUND OF THE INVENTION  
       [0002]     Oil, gas or water wells are conventionally drilled with a drill string, which comprises drill pipe, drill collars and drill bit(s). The drilled open hole is hereinafter referred to as a “borehole”. A borehole is typically provided with casing sections, liners and/or production tubing. The casing is usually cemented in place to prevent the borehole from collapse and is usually in the form of at least one large diameter pipe.  
       SUMMARY OF THE INVENTION  
       [0003]     According to a first aspect of the present invention there is provided apparatus comprising: 
        a tubular section arranged to be run into and secured within a larger diameter generally cylindrical structure;     at least one sleeve member wherein the sleeve member is positioned on the exterior of the tubular section and sealed thereto; and     pressure control means operable to alter the pressure within the sleeve member such that an increase in pressure causes the sleeve to move outwardly and bear against an inner surface of the larger diameter structure.        
 
         [0007]     The large diameter structure may be an open hole borehole, a borehole lined with a casing or liner string which may be cemented in place downhole, or may be a pipeline within which another smaller diameter tubular section requires to be secured or centralised.  
         [0008]     The tubular section is preferably located coaxially within the sleeve. Therefore the present invention allows a casing section or liner to be centralised within a borehole or another downhole underground or above ground pipe by provision of an expandable sleeve member positioned around the tubular section.  
         [0009]     The tubular section can be used within a wellbore, run into an open or cased oil, gas or water well. The tubular section may be a part of a liner or casing string. In this context, the term “liner” refers to sections of casing string that do not extend to the top of the wellbore, but are anchored or suspended from the base region of a previous casing string. Sections of liner are typically used to extend further into a wellbore, reduce cost and allow flexibility in the design of the wellbore.  
         [0010]     As previously stated casing sections are often cemented in place following their insertion into the borehole. Extension of the wellbore can be achieved by attaching a liner to the interior of a base portion of a casing section. Ideally the liner should be secured in position and this is conventionally achieved by cementing operations. However, cementing sections of liner in place is time consuming and expensive. The present invention can be used as a means to centralise and secure such a liner section, thus removing the need for cementing.  
         [0011]     Downhole embodiments of the apparatus can be used to isolate one section of the downhole annulus from another section of the downhole annulus and thus can also be used to isolate one or more sections of downhole annulus from the production conduit. The apparatus preferably comprises a means of securing the sleeve member against the exterior of the tubular member which may be a casing section or liner wall and preferably, the sleeve member provides a means of creating a reliable hydraulic seal to isolate the annulus, typically by means of an expandable metal element.  
         [0012]     The sleeve member can be coupled to the casing section or liner by means of welding, clamping or other suitable means.  
         [0013]     Preferably the apparatus is also provided with seal means. The function of the seal means is to provide a pressure tight seal between the exterior of the tubular section and the sleeve member, which may be the interior or one or both ends of the sleeve member.  
         [0014]     The seal means can be mounted on the tubular section to seal the sleeve member against the exterior of the tubular section. A chamber is created, which chamber is defined by the outer surface of the tubular section, the inner surface of the sleeve member and an inner face of the seal means. The seal means may be annular seals which may be formed of an elastomer or any other suitable material.  
         [0015]     The sleeve may be manufactured from metal which undergoes elastic and plastic deformation. The sleeve is preferably formed from a softer and/or more ductile material than that used for the casing section or liner. Suitable metals for manufacture of the sleeve member include certain types of steel. Further, the sleeve member may be provided with a coating such as an elastomeric coating. In addition the sleeve member may be provided with a non-uniform outer surface such as ribbed, grooved or other keyed surface in order to increase the effectiveness of the seal created by the sleeve member when secured within another casing section or borehole.  
         [0016]     According to another aspect of the present invention, the pressure control means comprise a hydraulic tool equipped with at least one aperture. Additionally, the tubular section preferably comprises at least one port to permit the flow of fluid into and out of the chamber created by the sleeve member. In operation the hydraulic tool is capable of delivering fluid through the aperture of the hydraulic tool under pressure and through the at least one port in the tubular member into the chamber. The hydraulic tool may contain hydraulic or electrical systems to control the flow and/or pressure of said fluid.  
         [0017]     The pressure control means may also be operable to monitor and control the pressure within the casing section. The pressure in the sleeve member is preferably increased between seal means and may be achieved by introduction of pressurised fluid.  
         [0018]     Pressure within the sleeve member is preferably increased so that the sleeve member expands and contacts the outer casing or borehole wall, until sufficient contact pressure is achieved resulting in a pressure seal between the exterior of the sleeve member and the inner surface of the casing or borehole wall against which the sleeve member can bear. Ideally, this pressure seal should be sufficient to prevent or reduce flow of fluids from one side of the sleeve member to the other and/or provide a considerable centralisation force.  
         [0019]     The initial outside diameter of the sleeve member can increase on expansion of the sleeve member to seal against the interior of the wellbore or other casing section.  
         [0020]     The sleeve can be expanded by various means. According to one aspect of the invention, the tubular section is provided with at least one port formed through its sidewall and positioned between the seals of the sleeve member to allow fluid under pressure to travel therethrough from a throughbore of the tubular section into the chamber.  
         [0021]     The port(s) may be provided with check valves or isolation valves which, on hydraulic expansion of the sleeve into its desired position, act to prevent flow of fluid from the chamber to the throughbore of the tubular section to preferably maintain the sleeve in its expanded configuration once the hydraulic tool is withdrawn. In this context, check valve or isolation valve is intended to refer to any valve which permits flow in only one direction. The check valve design can be tailored to specific fluid types and operating conditions.  
         [0022]     Alternatively, the port(s) may be provided with a ruptureable barrier device, such as a burst disk device or the like, which prevents fluid flow through the port(s) until an operator intentionally ruptures the barrier device by, for example, applying hydraulic fluid pressure to the tubing side of the barrier device until the pressure is greater than the rated strength of the barrier device. The use of such optional barrier device can be advantageous if an operator wishes to keep well fluids out of the sleeve chamber until the sleeve is ready for expansion.  
         [0023]     Another method of effecting expansion of the sleeve member involves insertion of a chemical fluid which can set to hold the sleeve member in place. An example of such fluid is cement.  
         [0024]     Towards the end of each sleeve member, sliding seals between the interior of the sleeve member and exterior of the tubular casing may be provided. A sliding seal allows movement in a longitudinal direction to shorten the distance between the ends of the sleeve member such that outward movement of the sleeve does not cause excessive thinning of the sleeve member.  
         [0025]     Expansion of the sleeve can be facilitated by provision of a sliding seal and/or through elastic and/or plastic deformation when the sleeve member yields. The sleeve member should preferably expand such that contact is effected between the exterior of the sleeve member and another pipe or borehole wall. In this way the at least one outer sleeve can be used to support or centralise the tubular member within an outer tubular member or borehole. The apparatus can also be used to isolate one part of annular space from another section of annular space. The outer sleeve members can be utilised to centralise one casing section within another or within an open hole well section.  
         [0026]     There can be a plurality of sleeve members on a casing section to isolate separate zones and separate formations from one another. The plurality of sleeve members may be expanded individually, in groups or simultaneously. In a situation when it is desired that all sleeve members are expanded simultaneously, this can be achieved by increasing the pressure within the entire casing section. Expansion of individual sleeve members or groups of sleeve members can be achieved by plugging or sealing internally above and below the ports which communicate with the respective sleeve members to be expanded and the pressure between these seals can be increased to the desired level.  
         [0027]     In preferred embodiments, the apparatus further comprises a sealant material provided on the outer surface of said sleeve and more preferably, the sealant material is provided with a protective covering layer or yet further outer sleeve member. Said further outer sleeve member may be unitary in fashion in order to seal the sealant material within a chamber defined between the inner surface of said further outer sleeve member and the outer surface of the aforementioned sleeve member. Alternatively, the yet further outer sleeve member may be provided with perforations or apertures therein to permit the sealant material to be extruded from said chamber when the said sleeve member is expanded radially outwardly in order to further enhance the seal provided by the apparatus.  
         [0028]     In certain circumstances it is necessary to isolate portions of annular space from adjacent portions within a wellbore. The present invention also creates a reliable seal to isolate the annulus.  
         [0029]     The apparatus has a dual function since it can be utilised with concentric tubulars such as pipelines to support or centralise the inner member inside an outer member and to isolate one part of annular space from another.  
         [0030]     According to another aspect of the present invention, a casing section is provided with perforations. In this situation sleeve members may be located either side of a perforation in the casing section allowing fluid from the well to enter the casing through the perforation, with the expandable sleeve members acting as an impediment to prevent fluid from entering different annular zones.  
         [0031]     The casing section or liner should be designed to withstand a variety of forces, such as collapse, burst, and tensile failure, as well as chemically aggressive brines. Casing sections may be fabricated with male threads at each end, and short-length couplings with female threads may be used to join the individual joints of casing together.  
         [0032]     Alternatively the joints of casing may be fabricated with male threads on one end and female threads on the other. The casing section or liner is usually manufactured from plain carbon steel that is heat-treated to varying strengths, but other suitable materials include stainless steel, aluminium, titanium and fibreglass.  
         [0033]     In accordance with the present invention there is also provided a method comprising the steps of: 
        sealing at least one expandable sleeve member on the exterior of a tubular section;     inserting the casing section into a generally cylindrical structure; and     providing pressure control means operable to increase the pressure within the sleeve member, such that the pressure increase causes the sleeve member to move outwardly allowing the exterior surface of the sleeve member to bear against the inner surface of the generally cylindrical structure.        
 
         [0037]     In certain preferred embodiments the method is useful for centralising one pipe within another or within an open hole well section. More preferably, the apparatus and method are useful in isolating a section of borehole located below the expandable sleeve member from a section of borehole located above the expandable sleeve member.  
         [0038]     The above-described method comprises inserting the casing section into another section or borehole to the required depth. This may be by way of incorporating the casing section into a casing or liner string and running the casing/liner string into the other section or borehole.  
         [0039]     Pressure, volume, depth and diameter of the sleeve member at a given time during expansion thereof can be recorded and monitored by either downhole instrumentation or surface instrumentation. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0040]     Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings in which:— 
         [0041]      FIG. 1  is a cross-sectional view of a first embodiment of a casing section with surrounding sleeve welded thereto;  
         [0042]      FIG. 2  is a cross-sectional view of a second embodiment of a casing section with an outer sleeve mechanically clamped thereto at one end and a sliding seal provided at the other end;  
         [0043]      FIG. 3  is a cross-sectional view of a third embodiment of a casing section with an outer sleeve mechanically clamped at both ends;  
         [0044]      FIG. 4  is a cross-sectional view of the casing section and attached outer sleeve of  FIG. 3  and an hydraulic expansion tool therein;  
         [0045]      FIG. 5  is a cross-sectional view of the casing section of  FIG. 2  and expanded outer sleeve in contact with a borehole wall;  
         [0046]      FIG. 6  shows a sequence for expanding two sleeve members;  
         [0047]      FIG. 6   a  is a cross-sectional view of a perforated liner provided with two sleeve members;  
         [0048]      FIG. 6   b  shows the perforated liner in a borehole of  FIG. 6   a  with a hydraulic expansion tool inserted therein; and  
         [0049]      FIG. 6   c  is a cross-sectional view of the perforated liner of  FIGS. 6   a  and  6   b  with expanded sleeves;  
         [0050]      FIG. 7  is a half-cross-sectional view of a portion of a perforated liner or casing provided with a fourth embodiment of an outer sleeve member and being located in a borehole just prior to actuation by a hydraulic expansion tool (not shown);  
         [0051]      FIG. 8  is a half-cross-sectional view of the sleeve member of  FIG. 7  in contact with the borehole wall after actuation by the hydraulic expansion tool;  
         [0052]      FIG. 9   a  is a full-cross-sectional view of the sleeve member of  FIG. 8 ;  
         [0053]      FIG. 9   b  is a detailed view of a portion of the sleeve member of  FIG. 9   a;    
         [0054]      FIG. 10  is a half-cross-sectional view of a portion of a liner or casing provided with a fifth embodiment of a perforated outer sleeve member and being located in a borehole just prior to actuation by a hydraulic expansion tool (not shown);  
         [0055]      FIG. 11  is a half-cross-sectional view of the sleeve member of  FIG. 10  in contact with the borehole wall after actuation by the hydraulic expansion tool;  
         [0056]      FIG. 12   a  is a full-cross-sectional view of the sleeve member of  FIG. 10 ; and  
         [0057]      FIG. 12   b  is a detailed view of a portion of the sleeve member of  FIG. 12   a.   
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0058]      FIG. 1  shows an apparatus  10  in accordance with the present invention. A casing is generally designated at  1  and provided with two sets of circumferential equispaced holes through its sidewall; upper ports  2   u  and lower ports  2 L. However, it should be noted that casing  1  could be modified by only providing one set of ports  2  which could be located at the middle of the length of the casing  1 , and furthermore could be modified by only providing one such port  2 . Casing  1  is located coaxially within sleeve  3 . The casing  1  may be either especially manufactured or alternatively is preferably conventional steel casing with ports  2  formed therein. The sleeve  3  is typically  316 L grade steel but could be any other suitable grade of steel or any other metal material or any other suitable material.  
         [0059]     The apparatus  10  comprises a sleeve  3  which is a steel cylinder with tapered upper and lower ends  3   u  and  3 L and an outwardly waisted central section  3   c  having a relatively thin sidewall thickness. Sleeve  3  circumferentially surrounds casing  1  and is attached thereto at its upper end  3   u  and lower end  3 L, via pressure-tight welded connections  4 .  
         [0060]     Since the central section of sleeve  3  is waisted outwardly and is stood off from the casing  1 , this portion of the sleeve  3  is not in direct contact with the exterior of the casing  1  which it surrounds. The inner surface of the outwardly waisted section  3   c  of sleeve and the exterior of the casing  1  define a chamber  6 .  
         [0061]     Upper O-ring seals  5   u  are also provided towards the upper end of sleeve  3   u  but interior of the upper welded connection  4 . Similarly lower seals  5 L are positioned towards the lower end of sleeve  3 L but are also positioned interior of the lower welded connections. Seals  5   u  and  5 L are in direct contact with the exterior of the casing and the ends of the sleeve,  3   u  and  3 L thereby providing a pressure tight connection between the interior of sleeve  3  and the exterior of casing  1  and thus act as a secondary seal or backup to the seal provided by the welded connections  4 .  
         [0062]     Ports  2   u  and  21  permit fluid communication between the interior or throughbore of casing  1  and chamber  6 .  
         [0063]     A second embodiment of an apparatus  20  in accordance with the present invention is shown in  FIG. 2  and comprises a sleeve  23  which is substantially cylindrical in shape with upper and lower ends  23   u ,  23 L and an outwardly waisted central section and is arranged co-axially around casing  21  which is similar to casing  1  of  FIG. 1 . Sleeve  23  is secured at its upper end  23   u  to the casing  21  by means of a mechanical clamp  28 . Towards the upper end  23   u  of the sleeve, a pair of seal members  25  are also provided in the form of O-rings to provide a pressure tight connection between the upper end of the sleeve  23   u  and the exterior of the casing  21 . Sleeve  23  has a lower end  23 L which is provided with a pair of sliding O-ring seals  27 .  
         [0064]     The exterior of the casing  21  in the region of the seals  25 ,  27  is preferably prepared by machining to improve the surface condition thereby achieving a more reliable connection between the seals  25 ,  27  and the exterior of the casing  21 .  
         [0065]     Upper end  23   u  along with seals  25  and lower end of sleeve  23 L along with sliding seals  27 , waisted central section of sleeve  23   c  and exterior of casing  21  define a chamber  26 . Sidewall of casing  21  is provided with circumferential equispaced ports  22  through its sidewall which permits fluid communication between the interior of casing  21  and the chamber  26 .  
         [0066]     Chamber  26  can be filled with pressurised fluid such as hydraulic fluid to cause expansion of the waisted central section of the sleeve member  23   c  in the radially outward direction, which causes simultaneous upwards movement of the sliding seals  27 , which has the advantage over the first embodiment of the sleeve  3  that the thickness of the sidewall of the outwardly waisted central section  23   c  is not further thinned by the radially outwards expansion. However any such upwards movement should be restricted such that the ports  22 L,  22   u  in the sidewall of casing  21  remain within chamber  26 .  
         [0067]     A further embodiment of apparatus  30  in accordance with the present invention is shown in  FIG. 3 , where the apparatus  30  is arranged in a similar manner to the apparatus  10 ,  20  of  FIGS. 1 and 2 . However, sleeve  33  of  FIG. 3  is attached to casing  31  at both the upper end  33   u  and lower end  33 L by clamps  39 . Clamps  39  are provided to hold the ends of sleeve  33  in position to prevent the sleeve  33  becoming dislodged when the casing  31  is run into the wellbore. Clamp  39  at the upper end  33   u  of the sleeve will allow sleeve  33  to move in a downward direction enabling expansion thereof. However upwards movement of the upper end  33   u  is prevented by clamp  39  which acts as an impediment. Similarly, clamp  39  at the lower sleeve end  33 L prevents downward movement, but will permit the lower sleeve end  33 L to move upwardly. The clamps  39  also ensure that the sleeve  33  maintains the correct position in relation to the ports  32 . Additionally, the clamps  39  maintain the sleeve in position over a section of casing  31  with prepared external surfaces. The surfaces can be prepared by machining and optimise the effectiveness of the two pairs of seals  35 .  
         [0068]     A further and preferred embodiment of an isolation barrier apparatus  40  in accordance with the present invention is shown in  FIG. 7 , where the apparatus  40  is arranged in a similar manner to the apparatus  10 ,  20 ,  30  of  FIGS. 1, 2  and  3 , although the clamps for securing one or both ends of the sleeve  43  to the casing/liner  41  are not shown in  FIG. 7 . In  FIG. 7 , the apparatus  40  comprises a casing or liner  41  provided with one port  42  in its sidewall (or more likely a number of ports  41  circumferentially equi-spaced through the sidewall but only one of which is seen in  FIG. 7 ).  
         [0069]     Casing or liner  41  is located coaxially within sleeve  43  which comprises an inwardly waisted central section  43   c  having a relatively thin sidewall thickness, such that the central section  43   c  is either in contact with, or is close to contact with the outer circumference of the casing  41 . However, each end  43   u ,  43 L of the central section  43   c  is bowed outwardly in order to provide scope for hydraulic expansion of the sleeve  43  as will be subsequently described; furthermore, this arrangement provides a number of further advantages including reducing the outer diameter of the apparatus which eases running in of the apparatus into the borehole  79  and also provides a radial space within which a compliant material/sealant  75  and outer thin sleeve  77  is provided.  
         [0070]     Accordingly, the inner surface of the initially inwardly waisted section  43   c , the inner surfaces of the bowed out ends  43   u ,  43 L and the exterior of the casing/liner  41  define a chamber  46 . Port(s)  42  permit fluid communication between the interior or throughbore of the casing/liner  41  and chamber  46 .  
         [0071]     Upper  45   u  and lower  45 L O-ring seals are provided as before and perform the same function.  
         [0072]     However, the apparatus  40  of  FIG. 7  comprises a further enhancement over the previously described embodiments in that a compliant material/sealant  75  placed around the expandable diameter of the central section of the outer sleeve  43   c . A further concentric sleeve  77  formed of thin metal construction (approximately 1-2 mm in thickness) is placed around the compliant material/sealant  75  to effectively sandwich the compliant material/sealant  75  between the existing outer sleeve  43   c  and the thin metal sleeve  77 . The thin metal sleeve  77  can be seal welded or clamped to the outer sleeve  43   c  at each end to provide a closed envelope or closed chamber for the compliant material/sealant  75  within.  
         [0073]      FIG. 10  shows a yet further enhanced isolation barrier apparatus  50  and which is identical to the apparatus  40  of  FIG. 7  and components of the apparatus  50  which are similar to components of the apparatus  40  are denoted with the reference numeral pre-fix  5 - instead of  4 -. However, the apparatus  50  differs from apparatus  40  by the addition of holes or perforations  89  provided around the circumference of, and through the sidewall of, the thin metal sleeve  87  to permit the compliant material/sealant  85  to be extruded through such holes or perforations  89  when the sleeves  53   c ,  87  are forced against the borehole wall  79   w  as a result of the hydraulic expansion of the outer sleeve  53   c , as will be subsequently described. Furthermore, the compliant material  85  used in this embodiment  50  is specifically formulated to act as a sealant.  
         [0074]     The material for the compliant material/sealant  75  is required to be sufficiently viscous to withstand removal and/or erosion from any fluid bypass during the hydraulic expansion of the outer sleeve  43   c  and resulting creation of the isolation barrier (which will be described subsequently). Preferably, the compliant material/sealant  75  will stiffen and set when extruded into, and exposed to, wellbore fluid temperatures. A suitable material  75  may be unvulcanised (green) elastomer which when extruded through small ports undergo a shearing effect, in a manner similar to transfer moulding, which will further promote the setting of the sealant  75 . Chemical sealants, adhesives, lost circulation type fluids and specially developed pressure sealing crosslinked polymers are other possible materials  75 .  
         [0075]     Isolation barrier apparatus  10 ,  20 , or  30  is conveyed into the liner or borehole by any suitable means, such as incorporating the apparatus into a casing or liner string and running the string into the wellbore until it reaches the location within the liner or borehole at which operation of the apparatus  10 ,  20 ,  30  is intended. This location is normally within the liner or borehole at a position where the sleeve  3 ,  23 ,  33  is to be expanded in order to, for example, isolate the section of borehole (or if present, casing/liner) located above the sleeve  3 ,  23 ,  33  from that below in order to provide zonal isolation.  
         [0076]     Expansion of the sleeve member  3 ,  23 ,  33  can be effected by a hydraulic expansion tool such as that shown in  FIG. 4 .  FIG. 4  shows tool  140  inserted into the casing section  31  shown in  FIG. 3 . Once the casing  31  reaches its intended location, tool  140  can be run into the casing string from surface by means of a drillpipe string or other suitable method. The tool  140  is provided with upper and lower seal means  145 , which are operable to radially expand to seal against the inner surface of the casing section  31  at a pair of spaced apart locations in order to isolate an internal portion of casing  31  located between the seals  145 ; it should be noted that said isolated portion includes the fluid ports  32 . Tool  140  is also provided with an aperture  142  in fluid communication with the interior of the casing  31 .  
         [0077]     To operate the tool  140 , seal means  145  are actuated from the surface (in a situation where drillpipe or coiled tubing is used) to isolate the portion of casing. Fluid, which may be hydraulic fluid, is then pumped under pressure through the coiled tubing or drillpipe such that the pressurised fluid flows through tool aperture  142  and then via ports  32  into chamber  36 .  
         [0078]     A detailed description of the operation of such an expander tool  140  is described in UK Patent application no. GB0403082.1 (now published under UK Patent Publication number GB2398312) in relation to the packer tool  112  shown in  FIG. 27  with suitable modifications thereto, where the seal means  145  could be provided by suitably modified seal assemblies  214 ,  215  of GB0403082.1, the disclosure of which is incorporated herein by reference. The entire disclosure of GB0403082.1 is incorporated herein by reference.  
         [0079]     Tool  140  would operate in a similar manner when inserted into casing  1 ,  21  of  FIGS. 1 and 2 . In the case where wireline is used to convey tool  140  into the borehole, a pump motor is operated to pump fluid from a hydraulic fluid reservoir into chambers  6 ,  26 ,  36  through aperture  142  via ports  2 ,  22 ,  32 . The increase in pressure then causes the sleeve  3 ,  23 ,  33  to move radially outwardly and seal against a portion of the inner circumference of the adjacent pipe (not shown), casing or liner section (not shown) or borehole  153 . The pressure within the chambers  6 ,  26 ,  36  continues to increase such that the sleeve  3 ,  23 ,  33  initially experience elastic expansion followed by plastic deformation. The sleeve  3 ,  23 ,  33  expands radially outwardly beyond its yield point, undergoing plastic deformation until the sleeve  3 ,  23 ,  33  bears against the inner surface of the liner or borehole as shown in  FIG. 5 . If desired, the pressurised fluid within the chambers  6 ,  26 ,  36  can be bled off following plastic deformation of the sleeve  3 ,  23 ,  33 .  
         [0080]     Alternatively the increase of pressure within chambers  6 ,  26 ,  36 , can be maintained such that the sleeve  3 ,  23 ,  33  continues to move outwardly against the adjacent pipe, casing or liner section such that the adjacent casing or liner section or pipe starts to experience elastic expansion. As the sleeve  3 ,  23 ,  33  makes contact with the tubular member or pipe, the pressure increases due to the resilience of the tubular member or pipe wall until the tubular member or pipe wall undergoes elastic deformation typically in the region of up to half a percent. The increase in setting pressure can be continued until a desired level of plastic expansion of the sleeves  3 ,  23 ,  33  have occurred and with the adjacent tubular member or pipe having undergone elastic expansion, when the pressure of the fluid is reduced the tubular member or pipe will maintain a compressive force inwardly on the plastically expanded sleeve  3 ,  23 ,  33 .  
         [0081]     When the tubular member or pipe has undergone elastic deformation, pressure can be released. In this situation, sleeves  3 ,  23 ,  33  are securely held since they have undergone plastic deformation with the tubular member remaining elastically deformed.  
         [0082]      FIG. 5  shows the casing  21  of  FIG. 2  with sleeve  22  in its expanded configuration, bearing against the borehole wall  153 . Chamber  26  is filled with pressurised fluid which is prevented from exiting the chamber  26  by means of optional check valves (not shown) attached to ports  22  to maintain the sleeve  23  in an expanded condition; the check valves permit the flow of pressurised fluid from the throughbore  17 ,  29  into the chamber  6 ,  26  but prevent the flow of fluid in the reverse direction.  
         [0083]     Pressurised chemical fluid can be pumped into chamber  26  to expand sleeve  22 . Once expanded the sleeve  22  may be maintained in position by check valves or the chemical fluid can be selected such that it sets in place after a certain period of time.  
         [0084]     Alternatively, the ports  22  may be provided with a burst disks (not shown) therein, which will prevent fluid flow through the ports  22  until an operator intentionally ruptures the disks by applying hydraulic fluid pressure from the throughbore  17 ,  29  to the inner face of the disk until the pressure is greater than the rated strength of the disk.  
         [0085]      FIG. 6  shows a sequence for expanding two sleeve members. Different formations are indicated by reference numerals  180   a - e.    
         [0086]      FIG. 6   a  shows the embodiment where a perforated liner/casing  171  is attached at its upper end by any suitable means such as a liner hanger to the lower end of a cemented casing  160 . Liner  171  is provided with two sleeves  173   u ,  173 L sealed thereto and similar to those previously described.  
         [0087]      FIG. 6   b  shows the perforated liner  171  of  FIG. 6   a  in a borehole  163  with a hydraulic expansion tool  190  inserted therein.  
         [0088]     Activation of the hydraulic expansion tool  190  increases the pressure in the chambers defined by the sleeves  173  such that the sleeves expand outwardly as shown in  FIG. 6   c . Thus, the sleeves  173   u ,  173 L isolate formation  180   b  (which may be a hydrocarbon producing zone) from the zones above and below  180   a ,  180   c  to  180   e  (which may be, for example water producing zones) and thus provide a means of achieving zonal isolation.  
         [0089]     As shown in  FIG. 7 , the apparatus  40  complete with the additional compliant material  75  sandwiched between the thin metal sleeve  77  on the outside and the outer (outer to the casing  41 ) sleeve  43   c  is run into position in the open hole section  79  to be isolated in the same manner as the previously described embodiments  10 ,  20  and  30 . The hydraulic expansion tool (not shown in FIGS.  7  to  9   b ) is run into the well through the casing  41  bore in the same manner as the previously described embodiments  10 ,  20  and  30 , and the outer sleeve  43   c  is pressured up via the communication port  42  as previously described for the other embodiments. In this case however, when the outer sleeve  43   c  expands, both the compliant material  75  and thin metal sleeve  77  will be forced to move outwardly along with the outer sleeve  43   c  and will be forced into contact with the open hole  79 . As the thin metal sleeve  77  contacts the inner wall  79  of the open hole  79  it will conform to the irregularities of the borehole wall  79   w , since the compliant material  75  beneath it takes up the annular variances between the less compliant outer sleeve  43   c  and the more compliant thin metal sleeve  77 . As the volume of compliant material  75  remains unchanged once all irregularities are filled, the contact stresses between the thin metal sleeve  77  and the wall  79   w  will increase as the activating pressure provided by the hydraulic expansion tool is increased. This has the advantage of providing a metal to open hole seal that conforms more closely to the borehole wall  79   w  variations than the bare outer sleeve  43   c , the overall effect of which should improve the effectiveness of the isolation barrier apparatus  40 .  
         [0090]     The apparatus  50  is run into position in the same manner as the previously described embodiments  10 ,  20 ,  30  and  40 .  
         [0091]     When the outer sleeve  53   c  is pressured up in the same manner as previously described, the thin metal sleeve  87  is once again forced against the borehole wall  79   w . As this happens, the annular volume between the thin metal sleeve  87  and the outer sleeve  53   c  will decrease, which causes the compliant material/sealant  85  to be extruded out through the holes/perforations  89  in the thin metal sleeve  87  and to be squeezed into the remaining annular space between the thin metal sleeve  87  and the borehole wall  79   w . In this way, any deep irregularities in the borehole wall  79   w  can be filled with the compliant material/sealant  85 . As the sealant  85  sets or cures, it should create a more effective fluid seal and hence an improved isolation barrier can be achieved.  
         [0092]     Modifications and improvements may be made to the embodiments hereinbefore described without departing from the scope of the invention.