You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to United Kingdom Patent Application No. GB1117511.4, filed Oct. 11, 2011, and titled DOWNHOLE VALVE ASSEMBLY, the contents of which are expressly incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a downhole valve assembly. In particular, the present invention relates to a downhole valve assembly that provides a contingency/back-up device in the event that another downhole valve has failed to open. 
         [0004]    2. Description of the Related Art 
         [0005]    Well completion involves various downhole procedures prior to allowing production fluids to flow thereby bringing the well on line. One of the downhole procedures routinely carried out during well completion is pressure testing where one downhole section of the well is isolated from another downhole section of the well by a closed valve mechanism such that the integrity of the wellbore casing/liner can be tested. 
         [0006]    Well completion generally involves the assembly of downhole tubulars and equipment that is required to enable safe and efficient production from a well. In the following, well completion is described as being carried out in stages/sections. The integrity of each section may be tested before introducing the next section. The terms lower completion, intermediate completion and upper completion are used to describe separate completion stages that are fluidly coupled or in fluid communication with the next completion stage to allow production fluid to flow. 
         [0007]    Lower completion refers to the portion of the well that is across the production or injection zone and which comprises perforations in the case of a cemented casing such that production flow can enter the inside of the production tubing such that production fluid can flow towards the surface. 
         [0008]    Intermediate completion refers to the completion stage that is fluidly coupled to the lower completion and upper completion refers to the section of the well that extends from the intermediate completion to carry production fluid to the surface. 
         [0009]    During testing of the intermediate completion stage the lower completion is isolated from the intermediate completion by a closed valve located in the intermediate completion. When the integrity of the tubing forming the intermediate completion section is confirmed the upper completion stage can be run-in. 
         [0010]    Generally the completion stages are run-in with valves open and then the valves are subsequently closed such that the completion stages can be isolated from each other and the integrity of the production tubing and the well casing/wall can be tested. 
         [0011]    Typically, the valves remain downhole and are opened to allow production fluids to flow. By opening the valves the flow of production fluids is not impeded. 
         [0012]    In the event that a valve fails to open, for example where the valve or an actuating mechanism operable to open the valve becomes jammed, remedial action is generally required because a failed valve effectively blocks the production path. 
         [0013]    Remedial action often involves removing the valve. The valve may be removed by milling or drilling the valve out of the wellbore to provide a free flowing path for production fluid. 
         [0014]    It will be appreciated that resorting to such remedial action can result in costly downtime because production from the well is stopped or delayed. The remedial action may result in damage to the well itself where milling or drilling the valve or valves from the wellbore may create perforations in the production tubing or the well casing or well lining. As a result such actions would preferably be avoided. 
         [0015]    It is desirable to provide a downhole device such that production downtime due to a failed valve is reduced. 
         [0016]    It is further desirable to provide an improved downhole valve assembly that helps to avoid using remedial actions such as milling or drilling to remove a failed valve from an intermediate or upper completion section of a wellbore. 
         [0017]    It is desirable to provide a downhole valve assembly that provides a contingency or back-up system when there is a failed valve located in the wellbore. 
       BRIEF SUMMARY OF THE INVENTION 
       [0018]    A first aspect of the present invention provides a downhole valve assembly operable to control production fluid flow around an obstruction in a production tubing string; wherein the valve assembly comprises a tubular body comprising an axial passage extending through the body; one or more ports extending substantially radially through the body; and one or more actuating members operable to move relative to the body to selectively open the ports such that a fluid flow path through the ports is defined between an annulus region outside of the valve assembly and the axial passage. 
         [0019]    The obstruction in the production tubing string may comprise a downhole valve assembly that is closed due to failure to open. 
         [0020]    The valve assembly according to the present invention may comprise a mechanically actuated actuating member. 
         [0021]    The mechanically actuated actuating member may be adapted for mechanical engagement with a removable downhole tool such that upon removal of the downhole tool the actuating member may be moved from a first position to a second position. When the mechanically actuated actuating member is in the second position the valve assembly may be in a primed state. 
         [0022]    Mechanical engagement of the mechanically actuated actuating member with a downhole tool such as a stinger or a washpipe may comprise coupling the mechanically actuated actuating member to the downhole tool. Accordingly, the mechanically actuated actuating member may comprise a coupling member adapted to couple with a corresponding coupling member on the downhole tool. Removal of the downhole tool, for example using a sliding action of the downhole tool in a generally uphole direction, may engage the coupling member of the actuating member with the coupling member of the downhole tool such that the actuating member may be displaced and may disengage from the downhole tool leaving the valve assembly in the primed state. 
         [0023]    In the primed state the ports remain closed until a subsequent event, for example, when fluid pressure is applied via the axial passage to the valve assembly. The applied fluid pressure may be within a predetermined range such that unnecessary actuation may be avoided. 
         [0024]    The valve assembly may further comprise a hydraulic actuator, comprising at least a piston member and an inlet and an outlet. The inlet of the hydraulic actuator may be in fluid communication with the axial passage of the body. The outlet may be in fluid communication with a hydraulically actuated actuating member that moves when fluid pressure is applied via the inlet. 
         [0025]    The inlet of the hydraulic actuator may be closed when the mechanically actuated actuating member is arranged in the first position and may be opened when the mechanically actuated actuating member is arranged in the second position. When the mechanically actuated actuating member is in the second position the inlet of the hydraulic actuator may be open, wherein the hydraulic actuator may be in fluid communication with the axial passage of the body. The inlet of the hydraulic actuator may be in fluid communication with the axial passage when the valve assembly is in the primed state. 
         [0026]    The hydraulic actuator may be operable to open the one or more ports upon application of fluid pressure via the inlet when the valve assembly is in the primed state. Hydraulic actuation may be provided by fluid pressure applied via production tubing or annulus such that pressurised fluid enters the inlet of the hydraulic actuator and applies pressure upon the piston member, which acts to displace the hydraulically actuated actuating member thereby opening the ports. The hydraulic actuator may comprise, for example, a spring, an electronically controlled pump, or a hydraulic piston. 
         [0027]    The mechanically actuated actuating member and the hydraulic actuator may be arranged within the tubular body. The mechanically actuated actuating member and the hydraulic actuator may be adapted to move by sliding in an axial direction relative to the body. 
         [0028]    The hydraulic pressure required to actuate the hydraulic actuator may be applied via the inlet due to fluid pressure from the axial passage or from the annulus. 
         [0029]    The hydraulic actuator may comprise one or more fluid openings that each may be aligned with a corresponding port on the tubular body to define the flow path between an annulus region outside of the valve and the axial passage. 
         [0030]    The ports through the body may be inclined relative to the axis of the body. The direction of the incline of the ports through the body may correspond substantially with the direction of fluid flow. 
         [0031]    The downhole valve assembly according to the present invention provides an alternative flow route for fluid in the event that another downhole valve assembly, for example a barrier valve, has failed to open. Therefore, a valve assembly according to the present invention maintains production flow such that remedial actions such as milling or drilling to remove the obstruction are avoided. 
         [0032]    A valve assembly according to a first embodiment of the present invention may restore normal axial flow of fluid following a diversion of fluid flow around the obstruction using the annulus region defined between the inside wall of the well/reservoir and the outside of the tubing mounted completion assembly. 
         [0033]    The valve assembly according to the first embodiment of the present invention may be located uphole of the potential obstruction such that restoration of fluid flow passes from the annulus to the axial passage. It will be appreciated that the valve assembly restores normal axial flow before the annulus flow is blocked by a packer. 
         [0034]    The valve assembly according to the first embodiment may comprise ports through the body, wherein the ports incline in an uphole direction from outside to inside the body. Therefore the direction of incline may correspond substantially with the direction of fluid flow. Fluid flow through the valve according to the first embodiment of the invention may be from the annulus region outside the body to inside the axial passage. Alternatively, fluid flow through the valve according to a second embodiment may be from inside the axial passage to the annulus region outside of the body. 
         [0035]    In respect of the valve assembly according to the first embodiment, annulus flow is necessary to bypass the obstruction. Annulus flow may be generated by fluid flow through perforations in the production tubing in a region downhole of the potential obstruction. Annulus flow may be created by production or injection fluid flowing through the perforations into the annulus region defined between the outside of the production tubing and the inside wall of the well/reservoir. 
         [0036]    Alternatively, annulus flow from a region downhole of the valve assembly may be created by a disconnection in the production tubing, for example one tubing mounted completion assembly may be disconnected from another tubing mounted completion assembly such that when production fluid flows it divides at the disconnection to generate flow through the axial passage and in the annulus region. 
         [0037]    Alternatively, annulus flow may be created by a valve assembly according to a second embodiment of the invention. The valve assembly according to a second embodiment may be located in a region of the well that is downhole of a potential obstruction. 
         [0038]    A valve assembly according to the second embodiment may comprise ports through the body, wherein the ports incline from inside to outside in an uphole direction. Therefore, the direction of incline may correspond substantially with the direction of production fluid flow where production fluid flow through the valve according to a second embodiment of the invention may be from the axial passage inside the body to the annulus region outside the body. 
         [0039]    The valve assembly according to the second embodiment may be utilised to create annulus flow such that an obstruction uphole of the valve assembly can be bypassed. Hydraulic actuation of the valve assembly according to the second embodiment of the invention may be provided by annulus flow entering the inlet of the hydraulic actuator and acting upon the piston member, which acts to displace the hydraulically actuated actuating member thereby opening the ports for fluid to flow. The valve assembly according to the second embodiment may be utilised to create annulus flow. 
         [0040]    Annulus flow is required to bypass an obstruction in the production tubing. However, in a tubing mounted completion assembly comprising a packer, production fluid flow via the annulus is prevented beyond the packer because the packer seals the annulus region defined between the outside of the production tubing and the inside wall of the well. Therefore, a valve assembly according to the first embodiment may be utilised to restore normal flow by diverting annulus flow back into the axial passage and beyond a packer. 
         [0041]    The valve assembly according to embodiments of the invention and all its associated control lines and actuators may be contained within the wellbore as part of a tubing mounted completion assembly and as such operation of the valve assembly may be by application of fluid pressure from uphole or downhole of the valve. Therefore, a valve assembly according to embodiments of the invention does not require any control lines to surface to operate. 
         [0042]    The valve assembly according to the present invention may provide a back-up or contingency device to a downhole valve assembly that has failed to open. 
         [0043]    A second aspect of the present invention provides a method of controlling and diverting fluid flow around an obstruction in a production tubing string, wherein the method comprises the steps of: 
         [0044]    locating a valve assembly in a wellbore, wherein the valve assembly comprises a tubular body comprising an axial passage extending through the body, one or more ports extending substantially radially through the body; and one or more actuating members operable to move relative to the body to selectively open the ports such that a fluid flow path through the ports is defined between an annulus region outside of the valve and the axial passage; and 
         [0045]    moving the one or more actuating members relative to the body to open the ports such that a fluid flow path for production fluid is defined; wherein the fluid flow path is defined between an annulus region outside of the valve and the axial passage. 
         [0046]    The valve may comprise a mechanically actuated actuating member, wherein the method comprises the step of engaging the mechanically actuated actuating member with a retrievable downhole tool, moving the mechanically actuated actuating member from a first position to a second position and disengaging the mechanically actuated actuating member from the retrievable downhole tool. The retrievable downhole tool may be, for example a washpipe or stinger. When the mechanically actuated actuating member is in the second position the valve assembly may be in a primed state. 
         [0047]    The valve assembly may further comprise a hydraulic actuator comprising at least a piston member, a fluid inlet and a fluid outlet, wherein the method may further comprise applying fluid pressure via the axial passage or annulus and the inlet such that the fluid pressure may act upon the piston to selectively open the ports such that a fluid flow path for production fluid is defined through the body of the valve assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0048]    Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
           [0049]      FIG. 1  is a schematic representation of a wellbore assembly comprising a downhole valve assembly in accordance with an embodiment of the present invention; 
           [0050]      FIG. 2  is a schematic representation of the wellbore assembly of  FIG. 1  showing a production flow path during normal operation of a producing well; 
           [0051]      FIG. 3  is a schematic representation of the wellbore assembly of  FIG. 1  showing a modified production flow path of a producing well in accordance with an embodiment of the present invention; 
           [0052]      FIG. 4  is a schematic representation of a closed downhole valve assembly in accordance with an embodiment of the present invention; 
           [0053]      FIG. 5  is a schematic representation of a closed downhole valve assembly in accordance with an embodiment of the present invention; 
           [0054]      FIG. 6  is a schematic representation of an open downhole valve assembly in accordance with an embodiment of the present invention; 
           [0055]      FIG. 7  is a schematic representation of a wellbore downhole completion assembly comprising a lower completion assembly, intermediate completion assembly, an upper completion assembly and including a downhole valve assembly in accordance with an embodiment of the present invention; 
           [0056]      FIG. 8  is a schematic representation of a wellbore assembly comprising a downhole valve assembly in accordance with a second embodiment of the present invention; 
           [0057]      FIG. 9  is a further schematic representation of a wellbore assembly comprising a downhole valve assembly in accordance with a second embodiment of the present invention; 
           [0058]      FIG. 10  is a schematic representation of a closed downhole valve assembly in accordance with a second embodiment of the present invention; and 
           [0059]      FIG. 11  is a schematic representation of an open downhole valve assembly in accordance with a second embodiment of the present invention 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0060]    Referring to  FIG. 1 , a partial longitudinal view of a wellbore completion arrangement  100  is illustrated. The wellbore completion arrangement  100  comprises a first downhole valve assembly  10 , a second downhole valve assembly  12  and a packer assembly  14 . 
         [0061]    The second downhole valve assembly  12  is representative of a downhole valve assembly in accordance with embodiments of the present invention. The downhole valve assembly  12  will be hereinafter referred to as a bypass valve assembly  12  such that it is distinguishable from the first downhole valve assembly  10 , which may be for example a barrier valve. 
         [0062]    In the illustrated example, a wellbore  16  is lined with a casing  18 , which in the illustrated embodiment is held in place with cement  20 . 
         [0063]    The downhole valve assembly  10 , the bypass valve assembly  12  and the packer assembly  14  are all run into the casing  18  as part of the well completion assembly  100  on a running string that may include a stinger or washpipe (not illustrated). 
         [0064]    For illustrative purposes,  FIG. 1  does not indicate any specific form or type of downhole valve assembly  10 . Suitable valve assemblies  10  will be discussed further below with respect to the action of the bypass valve assembly  12  according to embodiments of the present invention. 
         [0065]    The packer assembly  14  provides a seal in the annulus region  23  defined between the outside diameter of the production tubing  22  and the inside diameter of the casing  18 . 
         [0066]    In the illustrated embodiment the downhole valve assembly  10  is run-in in an open state and is subsequently closed when it has reached its location downhole. Once closed, fluid pressure can be applied from above the downhole valve assembly  10  to check the integrity of the production tubing  22  and the well completion assembly  100 . Following successful testing, the downhole valve assembly  10  can be opened such that production fluid can flow unimpeded through the downhole valve assembly  10  when the well is brought on line. 
         [0067]    The downhole valve assembly  10  can be opened by suitable means, for example fluid pressure from control lines to surface (not illustrated), mechanical actuation (not illustrated) or remote electronic actuation (not illustrated). Examples of suitable valves are ball valves and flapper valves. 
         [0068]      FIG. 2  illustrates a producing well  200  comprising a downhole valve assembly  10 , a bypass valve assembly  12  and a packer assembly  14 , where the well is online and production fluid is flowing from a downhole location towards the surface as indicated by arrows  26 . The normal path for production fluid is to flow in the uphole direction, through the axial bore of the production tubing  22  and to pass unimpeded through the open axial bore of the downhole valve assembly  10  and to continue to flow through the axial bore of the production tubing  22  towards the surface as indicated by arrows  26 . 
         [0069]      FIG. 3  illustrates a producing well  200  in the event that the downhole valve assembly  10  has failed to open and remains closed regardless of further attempts to open the downhole valve assembly  10 . In this situation, the bypass valve assembly  12 , according to a first embodiment of the present invention, can be used to facilitate a diversion of production fluid flow around the failed valve assembly  10  as illustrated in  FIG. 3  and described further below. 
         [0070]    Normal flow  26  from a producing well is illustrated in  FIG. 2 , however in the example illustrated in  FIG. 3 , the normal flow path  26  for production fluids towards the surface is prevented due to the blockage provided by the closed or failed downhole valve assembly  10 . 
         [0071]    In the illustrated embodiment, annulus flow, as indicated by arrows  32 , is provided from a region downhole of the downhole valve assembly  10 . 
         [0072]    Perforations  28  through the production tubing  22  in the region downhole of the downhole valve assembly  10  enables annulus flow  32  from the production flow  26 . 
         [0073]    The annulus flow  32  is created by the production flow  26  in the axial bore of the production tubing  22  flowing through the perforations  28  into the annulus  30 . Annulus flow  32  is therefore allowed in the particular completion assembly, for example intermediate or upper completion up to the packer assembly  14 , which provides an annulus seal and therefore prevents further uphole passage of annulus fluid flow  32  beyond the packer assembly  14 . 
         [0074]    As is illustrated in  FIG. 3 , the annulus flow  32  provides a flow path around the failed downhole valve assembly  10 . 
         [0075]    With reference to  FIGS. 3 ,  4 ,  5  and  6 , the bypass valve assembly  12 , according to an embodiment of the invention, facilitates diverting the annulus flow  32  of production fluid  26  from the annulus  23  back into the axial bore of the production tubing  22  in a location uphole of an obstruction caused by the closed valve assembly  10 . 
         [0076]      FIG. 4  illustrates a bypass valve  12  in accordance with embodiments of the invention. The bypass valve  12  is shown in the closed state. 
         [0077]    The bypass valve  12  comprises a tubular body  300 , which includes an axial bore  320  between an inlet end  340  and an outlet end  360 . The inlet  340  and the outlet  360  each comprise a threaded connector for attachment to a tubing mounted completion assembly or to the production tubing  22  of a downhole assembly. 
         [0078]    The body  300  includes flow ports  380  extending through the body  300  in a substantially radial direction such that fluid can flow from outside the bypass valve  12  to inside the bypass valve  12  (see  FIG. 6 ) as indicated by arrows  400 . 
         [0079]    The bypass valve assembly  12  includes a mechanically actuated sleeve  420  that moves by the action of retrieval/withdrawal of a washpipe or stinger from the completion assembly. 
         [0080]    The washpipe or stinger (not illustrated) includes a mechanical coupling device such as collet fingers that are operable to engage with a profiled section  425  of the sleeve  420  such that the washpipe or stinger engages with and pulls the sleeve  420  as the washpipe or stinger is pulled from the completion assembly. 
         [0081]    When the sleeve  420  reaches a stop  460  inside the body  300  the washpipe or stinger disengages from the sleeve  420 . At the limit of its movement the sleeve  420  exposes and opens a port  440  to the axial passage  320  such that the bypass valve assembly  12  is in a primed state, wherein it is ready for operation in the event that the downhole valve assembly  10  fails to open. 
         [0082]    The bypass valve assembly  12  comprises an internal hydraulic actuation mechanism  470 , illustrated simply in  FIG. 5  as a piston  480 , a spring  490  and hydraulic fluid  500 . 
         [0083]    In the event that the downhole valve assembly  10  fails to open, the bypass valve  12  can be actuated by applying downhole tubing pressure  510  (see  FIG. 4 ) which acts on the piston  480  via the port  440  such that movement of the piston  480  due to fluid pressure  510  displaces the hydraulic fluid  500  contained within the bypass valve  12  to cause a mechanism  515  to move which causes a compressed spring  490  to be released such that the spring  490  extends to complete the movement of the sleeve  525  by mechanical force exerted by the spring  490  on the sleeve  525  such that the flow ports  380  of the body  300  and corresponding ports  385  through the sleeve  320  are aligned (see  FIG. 6 ). Alignment of the flow ports  380 ,  385  provides a flow path  400  through the bypass valve  12  to facilitate the diversion of fluid flow from the annulus  23  to fluid flow in the axial passage  320  of the bypass valve  12  and the production tubing  22  towards the surface. 
         [0084]    As is illustrated in each of  FIGS. 4 ,  5  and  6  the flow ports  380  are angled downwards from the inside to the outside of the bypass valve for smooth uninterrupted passage of production fluid from the downhole region of the production tubing towards the surface. 
         [0085]    As described above with reference to  FIGS. 3 ,  4 ,  5  and  6  annulus flow  32  is required such that production fluid can flow around an obstruction, such as a closed valve. Therefore, to restore production flow the bypass valve  12  diverts the annulus fluid flow  32  back into the axial passage  320  and the production tubing  22  beyond. 
         [0086]    As described above with reference to  FIG. 3  annulus flow  32  may be created by having a perforated joint  29  in the production tubing in a region below the area of a potential obstruction such as the downhole valve assembly  10 . 
         [0087]      FIG. 7  illustrates a wellbore assembly  600  comprising a lower completion assembly  610 , an intermediate completion assembly  620  and an upper completion assembly  630 . The intermediate completion assembly  620  and the upper completion assembly  630  each comprise a downhole valve assembly  10 , a bypass valve assembly  12  and a packer assembly  14  as described above with reference to  FIGS. 1 to 6 . 
         [0088]    The lower completion assembly  610  and the intermediate completion assembly  620  are fluidly coupled and comprise a perforated joint  635 , which comprises perforations  28  (see  FIG. 3 ) to allow production fluid  26  to flow from inside the production tubing  22  to the annulus  23 . 
         [0089]    As can be seen from  FIG. 7  the intermediate completion assembly  620  and the upper completion assembly  630  are not physically coupled together. Instead, a gap  660  is present between the intermediate completion assembly  620  and the upper completion assembly  630  such that the production fluid  400  exiting the intermediate completion  620  divides at the gap  660  to produce annulus flow  432  that can flow around the obstruction caused by the valve  10  failing to open. 
         [0090]    The gap  660  or the distance between the intermediate completion  620  and the upper completion  630  may be in the region of nine to twelve metres (30-40 feet), but can be whatever distance that is deemed necessary. 
         [0091]    Annulus flow is controlled and contained between zones  610 ,  620 ,  630  because of the sealing arrangement provided by each packer assembly  14 . 
         [0092]    The intermediate completion assembly  620  is generally engaged with a washpipe and run into the well/casing whilst the valve  10  is open. Upon completion of the intermediate completion assembly  620  and prior to installing the upper completion assembly  630  the washpipe is removed. Upon removal of the washpipe the bypass valve  12  is primed and ready as discussed above with reference to  FIGS. 4 ,  5  and  6 . 
         [0093]    The upper completion assembly  630  is generally engaged with and run in to the well with a downhole tool such as a stinger (not shown). For workover of a well the stinger is removed and the valve  10  is closed, either mechanically upon removal of the stinger or in some other way, for example by electronic or hydraulic actuation. Upon removal of the stinger all control lines from the surface to the upper completion assembly  630  are disconnected and the bypass valve  12  according to embodiments of the invention is primed and ready for use to divert annulus flow  432  to tubing flow  260 . Therefore, following workover of a well, the bypass valve  12  can be used to restore a flow path  260  for production fluid as described above if attempts to reopen the valve  10  fail. 
         [0094]    An advantage of the bypass valve  12  according to embodiments of the invention may be that production downtime due to a downhole obstruction, for example a failed valve, is minimal compared with the remedial methods described above. This is because the bypass valve  12  is primed for use on routine removal of a washpipe or stinger and the subsequent application of fluid pressure from the region uphole of the failed valve  10  opens the ports  380  such that annulus flow can bypass the obstruction and restores production flow. 
         [0095]      FIG. 8  illustrates a partial longitudinal view of a wellbore completion arrangement  800  showing an application of a downhole valve assembly  812  according to a second embodiment of the present invention. Similar reference numerals have been applied and prefixed by the number eight. 
         [0096]    The well completion arrangement  800  comprises a first downhole valve assembly  810  and a second downhole valve assembly  812 . 
         [0097]    The second downhole valve assembly  812  is representative of a downhole valve assembly in accordance with a second embodiment of the present invention. Therefore, the downhole valve assembly  812  will be hereinafter referred to as a bypass valve assembly  812 . 
         [0098]    Comparing  FIG. 8  (of the second embodiment) with  FIG. 1  (of the first embodiment) it is to be noted that in the well completion arrangement illustrated in  FIG. 8  the packer assembly is omitted and that the bypass valve assembly  812  is located below the downhole valve assembly  810 . 
         [0099]    In the second embodiment a guide arrangement (not illustrated) is provided uphole of both the downhole valve assembly  810  and the bypass valve assembly  812  such that annulus flow is allowed, if and when required. 
         [0100]    In  FIG. 8  the wellbore  816  is constructed in the same way as the wellbore  16  illustrated in  FIG. 1 , where the wellbore  816  is lined with a casing  818 , which is securely held in place with cement  820 . 
         [0101]    The downhole valve assembly  810  and the bypass valve assembly  812  are run into the well as part of the well completion assembly  800  on a running string that may include a stinger or washpipe (not illustrated). 
         [0102]    In the illustrated embodiment the downhole valve assembly  810  is run-in in an open state and is subsequently closed when it has reached its location downhole. Once closed, fluid pressure can be applied from above the downhole valve assembly  810  to check the integrity of the tubing  822  and the well completion assembly  800 . Following successful testing, the downhole valve assembly  810  can be opened such that production fluid can flow unimpeded through the downhole valve assembly  810  when the well is brought on line. 
         [0103]    Primarily, the downhole valve assembly  810  can be opened by suitable means, for example fluid pressure from control lines to surface (not illustrated), mechanical actuation (not illustrated) or remote electronic actuation (not illustrated). Examples of suitable valves are ball valves and flapper valves. 
         [0104]    As in the first embodiment, where the well is a producing well  800  comprising a downhole valve assembly  810  and the bypass valve assembly  812  according to a second embodiment of the invention, production fluid flows from a downhole location towards the surface as indicated by arrows  826 . The normal path for production fluid is to flow, in the direction indicated by arrows  826 , in the uphole direction, through the axial passage of the production tubing  822  and to pass unimpeded through the axial passage of the bypass valve assembly  812  and through the open axial passage of the downhole valve assembly  810  and continue to flow through the axial passage of the production tubing  822  towards the surface. 
         [0105]    In the event that the downhole valve assembly  810  fails to open, and remains closed regardless of further attempts to open the downhole valve assembly  810 , the bypass valve assembly  812  can be used to facilitate a diversion of production fluid flow past the failed valve assembly  810 . 
         [0106]    In the illustrated example the bypass valve  812  is located below the obstruction created by the closed valve  810  (as illustrated in  FIG. 8  and  FIG. 9 ). 
         [0107]    Fluid pressure  831  applied via the annulus activates the internal mechanism of the annulus bypass valve  812  such that the annulus bypass valve  812  is actuated and opened and creates annulus flow, as indicated by arrows  832 , in a region downhole of the downhole valve assembly  810 . 
         [0108]    The bypass valve assembly  812  facilitates diverting the production flow  826  through the open ports  880  in the body of the annulus bypass valve  812  to create annulus flow  832  that allows the flow of production fluid to continue uphole via the annulus region around the obstruction created by the closed downhole valve  810 . 
         [0109]    In the illustrated example, a packer is omitted from the tubing mounted completion assembly  800  and as such annulus flow  832  can continue, unimpeded to surface. 
         [0110]    The bypass valve  812  according to the second embodiment comprises the same components as the bypass valve  12  according to the first embodiment and for clarity the features of the second embodiment are described by the following with reference to  FIG. 10 . Like reference numerals have been applied. 
         [0111]    The bypass valve  812  comprises a tubular body  300 , which includes an axial passage  320  between an inlet end  340  and an outlet end  360 . The inlet  340  and the outlet  360  each comprise a threaded connector for attachment to other components of a tubing mounted completion assembly or the production tubing of a downhole assembly. 
         [0112]    In the second embodiment, the body  300  includes flow ports  380  extending through the body  300  in a substantially radial direction such that production fluid can flow from inside the bypass valve  812  to outside the bypass valve  812  as indicated by arrow  401 . 
         [0113]    The bypass valve assembly  812  includes a mechanically actuated sleeve  420  that moves by the action of retrieval/withdrawal of a washpipe or stinger from the completion assembly to prime the bypass valve assembly  812 . The bypass valve assembly  812  is prepared (primed) for operation in the event that the valve assembly  810  fails to open and is operational upon application of hydraulic pressure to open the ports in the body of the valve. 
         [0114]    The washpipe or stinger (not illustrated) includes a mechanical coupling device such as collet fingers that are operable to engage with the profiled section  425  of the sleeve  420  such that the washpipe or stinger engages with and pulls the sleeve  420  as the washpipe or stinger is pulled from the completion assembly. When the sleeve  420  reaches a stop  460  inside the body  300  the washpipe or stinger disengages from the sleeve  420 . At the limit of its movement the sleeve  420  opens a port  440  such that the bypass valve assembly  812  is primed and ready for operation in the event that the downhole valve assembly  10  fails to open. 
         [0115]    The bypass valve assembly  812  comprises an internal hydraulically actuated mechanism  470 , which includes a piston  480 , a spring  490  and hydraulic fluid  500  (see  FIGS. 9 ,  10  and  11 ). A more detailed view of the components of the bypass valve is illustrated in  FIG. 10  and  FIG. 11 . 
         [0116]    Referring to  FIGS. 10 and 11 , in the event that the downhole valve assembly  810  fails to open, the bypass valve  812  is actuated by pressure applied via the annulus/upper production tubing.  FIG. 10  illustrates the bypass valve  812  prior to actuation and  FIG. 11  illustrates the bypass valve  812  when actuated. The fluid pressure is applied to the inside of the bypass valve  812  and the fluid acts upon the piston  480  via the port  440 . The piston  480  is displaced such that the hydraulic fluid  500  contained within the bypass valve  812  is displaced, which subsequently causes a mechanism  515  to move which allows a compressed spring  490  to be released. The spring  490  extends to complete the movement of the sleeve  525 , which operates to move to open the ports  380  such that a flow path  401  is defined through the bypass valve  812  to facilitate the diversion of production fluid flow from the axial passage  320  to the annulus. 
         [0117]    Whilst specific embodiments of the present invention have been described above, it will be appreciated that departures from the described embodiments may still fall within the scope of the present invention.

Summary:
A downhole valve assembly operable to control production fluid flow around an obstruction in a production tubing string. The obstruction may be caused by another valve or valve assembly located in the production tubing string, where the valve is closed and blocks flow through the production tubing. The downhole valve assembly comprises a tubular body that includes an axial passage extending through the body and one or more ports extending substantially radially through the body. The downhole valve assembly also includes one or more actuating members operable to move relative to the body. Movement of the actuating members selectively opens the ports such that a fluid flow path through the ports is defined between an annulus region outside of the valve assembly and the axial passage such that the blockage can be bypassed.