Abstract:
A method and apparatus for containing fluid in ah area of a wellbore annulus, in which fluid is energized to create a fluid flow which is at least partially obstructed and is directed to form in the annulus a localized area of high pressure to contain fluid in an area of the annulus of lower pressure. In an embodiment, the method creates a pressure plug in the annulus.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119 to United Kingdom Patent Application Serial No. 0712528.9 filed on Jun. 28, 2007, entitled “APPARATUS AND METHOD,” the disclosure of which is hereby incorporated by reference. 
     RELATED ART 
     1. Field of the Invention 
     The present invention relates to an apparatus and method for creating a localized area of high pressure within a conduit and a method for retaining pressure within an annulus. In an exemplary application, the invention is useful for containing well pressure while performing wireline operations. 
     2. Brief Discussion of Related Art 
     When tool strings are deployed through an access hole into a live wellbore there is a need to contain pressurized well fluids and prevent their escape through the annulus between the tool string and the access hole of the wellbore. Sealing of the annulus around slickline (i.e. smooth wire) is currently achieved by compressing a cylindrical rubber to seal against the slickline in the annulus. For braided wire and lines with a rough profile, this type of sealing mechanism is not practical as the surface profile of the wire restricts effective sealing. Instead, a highly viscous fluid such as grease is injected into the annular space around the wife. This creates a seal that prevents the escape of well fluids but without restricting movement of the wire. There can be significant changes in viscosity as a result of temperature increases, which could be detrimental to the ability to contain the well pressure. In addition, there are practical disadvantages to purchasing, storing, handling and disposing of the grease. Grease tends to stick to the wire and as a result when the wire is removed from the well and spooled onto a drum, there can be spills on the deck of the platform leading to an unsafe working environment and environmental contamination. 
     INTRODUCTION TO THE INVENTION 
     According to a first aspect of the invention, there is provided a method for containing fluid in an area of a wellbore annulus, the method comprising the steps of: 
     (a) energizing a fluid to create a fluid flow; 
     (b) at least partially obstructing the fluid flow; and 
     (c) directing the fluid flow to form in the annulus a localized area of high pressure to contain fluid in an area of the annulus of lower pressure. 
     Typically, as a result of the obstruction to fluid flow, performance of step (b) causes a back pressure to be generated. The method may include impacting the fluid against a shaped surface to create a back pressure in the annulus, the back pressure being sufficiently high to contain fluid in the wellbore annulus. Thus, the energized fluid may seal the annulus in the localized area of high pressure, such that escape of fluid from regions of ambient pressure is restricted or prevented. 
     Step (a) can include accelerating the fluid flow. Step (a) can also include increasing the speed of fluid to a speed between 20-600 m/s. Step (a) can further include injecting fluid into a channel and shaping the channel to energize the fluid. Step (a) can even further include providing a body having a channel with a fluid inlet and a fluid outlet and shaping the channel to have a lower sectional area in the region of the outlet compared with the inlet such that the velocity of the fluid is increased in the region of the outlet. In this way, the fluid can be formed into a jet. Preferably, the jet has sufficient velocity to overcome the ambient pressure, (for example, the pressure at the outlet of the channel) so that it reaches the obstruction of step (b). 
     Step (b) can include impeding or placing an impediment in a path of the energized fluid. Step (b) can also include at least partially confining the fluid in a chamber and/or can include at least partially confining the energized fluid in a predetermined area of the annulus. Thus, the chamber may define an annular space. 
     Steps (b) and (c) can be performed simultaneously. Step (b) can include positioning a surface in the path of energized fluid flow and step (c) can include angling the surface such that flow is directed to generates localized area of higher pressure in a predetermined region. 
     Step (c) of the method can include deflecting the fluid flow to generate an area of higher pressure in the annulus. The method may include deflecting the fluid flow toward the area of higher pressure. The method may include deflecting the fluid flow to generate a pressure plug in the area of higher pressure. The pressure plug and/or area of high pressure may separate first and second regions of lower pressure, and may restrict of prevent fluid flow between the first and second regions. In particular, the plug and/or area of high pressure may contain, act as a barrier to, seal against, cap and/or act as a fluid wall for well fluid located downhole, and may prevent flow of fluid from the downhole location to a second region uphole in relation to the first region. The first and second regions, thus, may be regions of the wellbore annulus. 
     The wellbore annulus may be an annular space defined between a wireline or slickline, and an inner wall of a wellbore of other wellbore equipment, for example, a pressure control head, stuffing box, wellbore tubing or open hole formations. 
     The method can include a further step (d) of collecting fluid as the localized area of higher pressure dissipates to the ambient pressure. The method can further include recycling the fluid in step (d) by performing step (a) on the collected fluid. The method may include circulating fluid into and out of said area for maintaining the area of high pressure spatially and over a period time. Thus, in providing the high pressure area or pressure plug, fluid is moved through the high pressure region. In particular embodiments, where the area of high pressure and/of pressure plug separates first and second regions of lower pressure, the second region is at a lower pressure than that of the first region, to provide for fluid flow or dissipation of fluid from the high pressure region to the second region of lower pressure. In certain embodiments, the high pressure area or pressure plug may form an interface separating the first and second regions. Energized fluid used to create the high pressure area may be collected from the second region of lower pressure for repeat use. Fluid may flow from the high pressure region to the second region in preference to the first region, to maintain the pressure conditions of the high pressure region, whilst containing fluid, in the first region. 
     The method can involve containing ah ambient pressure in an annulus of a wellbore by performing the method previously described downstream of the intended containment region. 
     The method can include selecting the parameters for fluid speed and the obstruction such that the localized area of high pressure acts as a plug of high pressure to contain the ambient pressure. Such parameters may include, speed of fluid, direction of fluid flow, channel dimensions, relative position and orientation of the channel to the annulus, relative position and/or orientation of the channel to the angled surface. The method can include selecting a fluid having a viscosity of less than 10 centipoise (0.1 Pa s). 
     According to a second aspect of the invention, there is provided apparatus for containing a fluid in a wellbore annulus comprising: 
     a means for energizing a fluid to form a fluid flow; and 
     an obstruction adapted to obstruct the flow of energized fluid; and 
     means for directing the fluid to the wellbore annulus to create in the annulus a localized area of high pressure sufficient to contain fluid in ah area of the wellbore annulus of an ambient pressure. 
     The obstruction of fluid flow can creates back pressure, by presenting an obstacle to the flow of the fluid. The energized fluid may plug or seal the annulus at said area of high pressure. 
     The obstruction is formed from a material having an excellent wear resistance. 
     The fluid can be a low viscosity and/or water-based fluid. The fluid can be water. The water can include additives such as corrosion inhibitors. 
     The fluid can have a viscosity of around 1-5 centipoise (1-5×10−2 Pa s). 
     The apparatus may include a channel having a fluid inlet and a fluid outlet wherein the channel has a smaller sectional area in the region of the outlet than that of the inlet to increase fluid velocity in the region of the outlet for jetting the fluid into the localized area of high pressure. More specifically, the means for energizing a fluid can comprise a body having a channel with an inlet for receiving a fluid and an outlet, and wherein at least a portion of the channel converges towards the outlet. The portion of the channel that converges towards the outlet can have a lower sectional area, which increases the velocity of fluid within that portion of the channel. The apparatus and/or body can have a throughbore. The throughbore may be arranged to receive a line and wherein the obstruction can be arranged and/or positioned such that pressure is generated in an annular space between the throughbore and the line. The body and the channel can form asymmetrical concentric nozzle for producing an annular jet of energized fluid. 
     The obstruction and/or means for directing the fluid may include a deflector insert located in the throughbore. The deflector insert may be removably attached to a main body of the apparatus. The deflector insert and/or inner surface of the throughbore may include an angled and/or shaped surface. The deflector insert and/or inner surface of the throughbore may have an inwardly protruding member, which may in turn include the angled and/or shaped surface placed in the path of energized fluid. Thus, the shaped surface may extend inwardly to partially occlude an annular space which may be formed around a line received in the throughbore. 
     The obstruction and/or means for directing the fluid may include a nozzle insert located in the throughbore. The nozzle insert may be removably attached to a main body of the apparatus, and together with the main body may define a channel for jetting fluid into the wellbore annulus. The nozzle insert together with the deflector insert may be arranged to help energize, direct and obstruct the fluid to create said high pressure area and/or pressure plug. 
     The width of the annulus can be approximately 0.05 to 1.0 inch (1.27 to 25.4 mm). 
     The obstruction can comprise a surface that is angled relative to the direction of fluid flow. The angle of the surface relative to an axis of the conduit can be selected according to the desired application. The angle of the surface relative to an axis of the conduit can be selected to deflect the fluid flow to create an area of localized pressure in the predetermined position. Thus, the apparatus may include a surface in the path of energized fluid flow oriented at an angle relative to the direction of fluid flow for deflecting the fluid toward the annulus to generate the area of high pressure. 
     The directing means may include a fluid channel. The obstruction and the directing means may together define a geometry which interacts with the energized fluid permitting sufficient pressure build up to generate a pressure plug in the annulus from the energized fluid. The obstruction, together with the means for directing the fluid, may be adapted to create the localized area of high pressure in the annulus. This geometry may facilitate pressure build-up on directing energized fluid to the annulus. The geometry may be based on selected parameters for the fluid flow, such as required fluid flow speeds and/or other parameters. 
     The surface can be cone-shaped in section. The cone angle can be between 20° and 60° from the axis of the conduit. The cone angle can be defined as the angle of the surface relative top the axis of the conduit. Alternatively, the surface can be lens-shaped and/or concave. 
     The invention is advantageous for use in a wellbore to contain a pressure within an annulus as it reduces the amount of equipment space required, increases safety margins and reduces contamination of the surrounding environment. 
     Contact between a high velocity fluid stream and the surface causes a back pressure to be generated. This creates a localized area of high pressure that can be moved to an appropriate position in an annulus of the wellbore by deflecting fluid accordingly. When the pressure generated exceeds the pressure of the wellbore, the area of high pressure is effective in forming a pressure barrier that acts to substantially contain the well pressure. 
     The annulus can be created by running a line, such as wireline or slickline through a tubing. The line can be selected from the group consisting of: wireline; slickline; and downhole tubing. The annulus may be formed between a wireline and an inner wall of a throughbore for receiving the line. 
     The inner wall may have a recess, step, angled surface, inwardly protruding member or be otherwise shaped for interacting with a fluid and/or to assist energizing a fluid. The fluid may be jetted into the annulus through the inner wall of the throughbore. Thus, the wall may at least partially act as an obstruction, or a deflector for energized fluid. 
     The minimum predetermined velocity can be 20 m/s. More preferably, the minimum predetermined velocity can be 40 m/s. Alternatively, the value for the minimum predetermined velocity can be any value up to around 600 m/s, depending on the application and the pressures in the annulus that need to be contained. 
     Preferably, the fluid has a lower viscosity than a long-chain hydrocarbon, such as grease. Preferably, the fluid has a viscosity around a factor of 100 times less viscous than a long chain hydrocarbon. 
     The method can include shaping the surface to deflect the fluid to a predetermined region such that the back pressure forms a pressure plug in the annulus. Thus, the method may include shaping a surface for deflecting fluid to a predetermined region in the annulus and thereby facilitate creating the area of higher pressure. 
     The apparatus may take the form of a pressure control head, a stuffing box and/or any other pressure control apparatus for wellbore tubing. 
     The second aspect of the invention can include any previously described features or method steps of the first aspect of the invention, where appropriate. 
     According to a third aspect of the invention there is provided a pressure control head for wellbore tubing. The pressure control head may comprise apparatus according to the second aspect of the invention, and may be adapted to perform the method of the first aspect of the invention. 
     The pressure control head may include a main body having an axial throughbore for receiving a wireline therethrough, and an insert or cartridge, wherein the main body and the insert together may form a symmetrical concentric nozzle for producing an annular jet of energized fluid to an annular space defined between ah inner surface the pressure control head and the wireline providing a pressure seal against the wireline. 
     The insert may be removably attached to the main body for facilitating m maintenance. Other components of the apparatus of the second aspect of the invention, for example, the directing means, energizing means and/or the obstruction, may form a part of a removable cartridge or insert. 
     According to a fourth aspect of the invention there is provided a method for creating a localized area of higher pressure relative to an ambient pressure in a conduit, comprising the steps of: 
     (a) energizing a fluid; 
     (b) at least partially obstructing the fluid flow; and 
     (c) directing the fluid flow such that a localized area of high pressure is formed. 
     According to a fifth aspect of the invention, there is provided an apparatus for creating a localized pressure in a conduit comprising: 
     a means for energizing a fluid; and 
     an obstruction to obstruct the flow of energized fluid and create ah area of localized pressure. 
     The fluid may have a viscosity of less than 10 centipoise (0.1 Pa s). 
     According to a sixth aspect of the invention, there is provided a method for containing a pressure within ah annulus of a wellbore including the steps of: 
     providing a fluid having a predetermined minimum velocity; and 
     impacting a fluid against a shaped surface such that the impact creates a back pressure sufficient to contain fluids within the annulus of the wellbore. 
     According to a seventh aspect of the invention, there is provided a method for containing fluid at pressure in a wellbore annulus, the method comprising the steps of directing a flow of fluid to the annulus and obstructing the flow to create in the annulus an area of sufficiently high pressure to restrict escape of fluid from and/or contain fluid within an area of the wellbore annulus of lower pressure. 
     According to ah eighth aspect of the invention, there is provided a method for containing fluid at pressure in a wellbore annulus, the method comprising the steps of confining fluid in a localized area of the annulus, and pressurizing the fluid in said area sufficiently to restrict escape of fluid from an area of the wellbore annulus of lower pressure. 
     Any one of the third to eighth aspects of the invention can include any previously described features or method steps of the first and/or second aspects of the invention, where appropriate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a pressure control head; 
         FIG. 2  is a detailed sectional view of a nozzle and a deflector of the pressure control head shown in  FIG. 1 ; 
         FIG. 3  is a sectional schematic view of the nozzle and the deflector shown in  FIG. 2 ; 
         FIG. 4  is an alternative sectional view of the nozzle and the deflector of the  FIG. 1  apparatus; 
         FIG. 5  is a sectional view of the nozzle and an alternative deflector; and 
         FIG. 6  is a sectional view of the nozzle and another alternative deflector. 
     
    
    
     DETAILED DESCRIPTION 
     The exemplary embodiments of the present invention are described and illustrated below to encompass an apparatus and method for creating a localized area of high pressure within a conduit and a method for retaining pressure within an annulus. Of course, it will be apparent to those of ordinary skill in the art that the embodiments discussed below are exemplary in nature and may be reconfigured without departing from the scope and spirit of the present invention. However, for clarity and precision, the exemplary embodiments as discussed below may include optional steps, methods, and features that one of ordinary skill should recognize as not being a requisite to fall within the scope of the present invention. 
     Referencing  FIG. 1 , a pressure control head  8  has four main portions: a collar  110 ; a body  10 ; a housing  40 ; and a funnel  50   
     Referring to  FIGS. 1 and 2 , the collar  110  is connected to the body  10  at a coupling  111 . The body  10  is substantially cylindrical and is formed with a centrally disposed throughbore  13  having a flared portion  13   f  for accommodating inserts (described hereinafter). An inlet port  22  extends through a sidewall of the body  10  and an outlet port  44  also extends through the sidewall of the body  10 . Both the inlet port  22  and the outlet port  44  are in fluid communication with the throughbore  13 . 
     As shown in  FIG. 2 , the flared throughbore portion  13   f  of the body  10  is arranged to receive a deflector insert  20 . The deflector insert  20  engages the body  10  by means of a threaded connection  21 . An outer surface of the deflector insert  20  is provided with an annular groove  25  that accommodates an annular seal  26  to create a fluid tight seal between the exterior of the deflector insert  20  and the throughbore  13 . The deflector insert  20  has a central passageway or throughbore  23  for receiving a wireline. Part of the throughbore  13  is shaped as a frustocone having an impact surface  28  with a cone angle of around 50° relative to its axis of symmetry. At its upper end, the throughbore  23  of the deflector insert  20  opens out into a diverging annular side wall  27 . The impact surface  28  of the deflector insert  20  is formed from a ceramic material that has excellent wear resistance. 
     The flared throughbore portion  13   f  also has an annular step  13   s  positioned adjacent the part of the body  10  where the inlet port  22  communicates with the throughbore  13 . A nozzle insert  30  having a central passageway or throughbore  33  for receiving a wireline is positioned within the body  10  so that a portion of the nozzle insert  30  abuts the annular step  13   s . The nozzle insert  30  is provided with a shaped protrusion  38  at one end that extends into the throughbore  23  of the deflector insert  20 . The protrusion  38  of the nozzle insert  30  has an outer annular side wall  35 . Together, the outer side wall  35  of the nozzle insert  30  and the annular inner side wall  27  of the deflector insert  20  forms a concentric annular channel that acts as a convergent nozzle  31 . An inlet of the nozzle  31  is in communication with an annular chamber  37  and hence the inlet port  22  extending through the sidewall of the body  10 . The inlet port  22  is connected to a pump (not shown) to inject fluid through the port  22 , into the chamber and the nozzle  31 . The exterior of the nozzle insert  30  is provided with an annular groove  39  that accommodates ah annular seal  34  to create a fluid tight seal between the flared throughbore portion  13   f  and the exterior of the nozzle insert  30 . Together, the annular seals  26 ,  34  act to isolate the lower chamber  37  such that fluid entering through the inlet port  22  can only escape via the nozzle  31 . 
     The housing  40  has a box end coupled to a pin end of the body  10 , by means of a threaded connection  121 . The housing  40  is substantially cylindrical and has a hollow interior  43  that houses an annular piston  120 , a seal cone  70 , a spring  80  and a wiper  60 . The annular piston  120  is substantially cylindrical and one end is slidably disposed in the flared throughbore portion  13   f . A piston head  120   h  abuts and end face  10   e  of the body  10 . An upper chamber  46  is formed in the flared throughbore portion  13   f  between the nozzle insert  30  and the annular piston  120 . The upper chamber  46  is in fluid communication with the outlet port  44 . 
     The pin end of the body  10  has an annular groove  14  on its exterior and an annular groove  15  on its interior for accommodating annular seals  122 . The exterior of the piston head  120   h  is provided with an annular groove  123  that accommodates an annular seal  122 . All the seals  122  fluidly isolate an annular chamber  126  that is in fluid communication with a pump (not shown) via a port  128  extending through a sidewall of the housing  40 . 
     The spring  80  is retained between the housing  40  and the piston head  120   h , so that the annular piston  120  is resiliently urged to abut the end face  10   e  of the body  10 . The seal cone  70  is attached to the piston  120  and has an angled annular face that abuts the wiper  60 . The wiper  60  is typically a polymer disposed within the housing  40  and the wiper  60  is compressible by the action of the seal cone  70  thereon. 
     The funnel  50  has a pin end and is attached to a box end of the housing  40  via a threaded connection  51 . The funnel  50  is arranged with its divergent end distal from the housing  40 . The funnel  50  is provided with a centralizer  90  for centralizing a wireline running therethrough. The centralizer  90  also acts as a barrier against which the wiper  60  can react under the force of the seal cone  70  acting thereagainst. An outlet port  52  extending through a sidewall of the funnel  50  is provided to recover fluids collected in the funnel  50 . 
     A wireline  130  is shown in  FIGS. 1 to 6  centrally disposed in the throughbores  13 ,  23 ,  33  of the pressure control head  8 . The throughbores  13 ,  23 ,  33  of the components making up the pressure control head  8  shown in  FIG. 1  form a continuous throughbore that allows a wireline  130  to run unimpeded therethrough. An annular space  112  is created between the wireline  130  and the throughbores  13 ,  23 ,  33 . The annular space  112  is substantially continuous through the body  10 , the deflector insert  20  and the nozzle insert  30 . 
     Prior to use, the pressure control head  8  is assembled in the form shown in  FIG. 1 . The deflector insert  20  followed by the nozzle insert  30  are screwed into the flared throughbore portion  13   f  of the body  10 . The piston  120  is inserted into an upper end of the body  10  such that the end face  10   e  of the body abuts the piston head  120   h . The spring  80  is compressed between the piston  120  and the funnel  50  prior to making up the connections. Connections  111 , 121 ,  51 , are made up respectively, between the body  10  and the collar  110 , the body  10  and the housing  40  and the housing  40  and the funnel  50 . The pressure control head  8  is then incorporated in a downhole tubing string such that the divergent end of the funnel  50  is located upstream of (closer to surface than) the collar  110  that forms the lowermost part of the assembly closest to the downhole environment. The wireline  130  can then be run downhole through the pressure control head  8 . 
     In use when the wellbore is at high pressure e.g. 7500 psi (51.7 MPa), the method of the invention as used to contain these downhole pressures and substantially restrict the escape of downhole fluids via leak paths in the annulus  112  between the throughbores  13 ,  23 ,  33  and the exterior of the braided wireline  130 . According to the present embodiment, the diameter of the wireline  130  is 0.312 inches (7.9 mm). 
     As the wireline  130  is being run downhole, the pump connected to the inlet port  22  pumps a working fluid into the chamber  37 . The working fluid is water and can be used with some anti-corrosion additives to limit the corrosive potential of the fluid to the wireline  130 , the pressure control head  8  and other downhole components. Continued pumping of fluid into the lower chamber  37  forces fluid through the nozzle  31 . The dimensions of the nozzle  31  and specifically, the fact that the nozzle  31  converges towards its outlet causes the fluid to accelerate, thereby increasing the speed of the fluid until it exits the nozzle  31  at the outlet in a relatively high velocity jet haying a speed of around 500 m/s. The fluid jet impacts against the impact surface  28 , which acts as an obstruction in the path of the jet. The effect of the high velocity fluid impacting against the impact surface  28  is that a large back pressure is generated due to the surface presenting an impediment to the high speed fluid flow. The 50° cone angle of the impact surface  28  deflects the fluid flow towards the wireline  130 . A localized area of high pressure is thereby formed in the annulus  112  surrounding the wireline  130 . This acts as a pressure plug. The schematic diagram shown in  FIG. 3  indicates the direction of fluid flow. Arrows  114  indicate the direction in which the downhole pressures are acting. The pressure plug is at a higher pressure than the downhole pressure and therefore contains the downhole fluids at pressure that would otherwise escape in the direction of the arrows  114 . 
     The fluid exiting the outlet of the nozzle  31  must have sufficient velocity to overcome the pressure acting against the direction of fluid flow (shown by the arrows  114 ) in the annulus  112 . The small containment region between the nozzle  31  outlet, the impact surface  28  and the wireline  130  obstructs the fluid flow and thereby plugs the annulus to prevent the escape of high pressures. The working fluid then dissipates in the annulus  112  and the pressure decreases away from the region of the high pressure plug. Thus, working fluid flows into, through and then out from the region of the high pressure plug toward the chamber  46 . The pressure away from the pressure plug near the chamber  46  is at a lower pressure than that of the wellbore fluids contained downhole. Since the working fluid is continuously pumped and circulated through the nozzle  31 , the effect of the pressure plug is continuously maintained. 
     Once the working fluid has dissipated if moves up (and/or down) the annulus  112  and the fluid collected in the chamber  46  is recovered through the outlet port  44 . Fluid collected through the port  44  can then be recycled, treated if necessary, and reinjected through the inlet port  22 . 
     The method of the invention can be used both as the wireline  130  is run downhole and pulled from the wellbore. 
     In the case where the wireline  130  is being pulled to surface there may be a need to ensure that any excess fluid is removed before the wireline  130  exits the wellbore to prevent drips and spillage at the surface. In order to substantially reduce the amount of fluid carried by the wireline  130 , the wiper  60  can be urged into contact with the wireline  130  to remove excess fluid. This is achieved by injecting a hydraulic fluid through the port  128  into the chamber  126 . Fluid in the chamber  126  acts against the piston head  121  to urge upward movement of the piston  120  and hence the attached seal cone  70  against the bias of the spring  80  to force the wiper  60  into contact with the wireline  130  to remove excess fluids therefrom. The funnel  50  is shaped to collect any remaining drips from the wireline  130  that are then recovered through the port  52  and recycled if required. 
     The deflector insert  20  is advantageously provided as a separate component that is coupled to the body  10 . The deflector insert  20  and in particular, the impact surface  28  of the frustocone is prone to wear and can be easily removed and replaced because it is separable from the body  10 . This also applies to the nozzle insert  30  if it is damaged or suffers wear. 
     Ideally, the nozzle  31  should be sized to suit a large range of wireline diameters, thus, eliminating the need for bespoke equipment depending on wireline diameter. However, the fact that the deflector insert  20  and the nozzle insert  30  are separate components that together determine the shape of the nozzle  31  through which the working fluid is directed (and hence the fluid speed) allows the dimensions of the channel to be easily altered for different applications or ranges of wireline  130  size. For example, the nozzle insert  30  can be removable so that it may be replaced by a nozzle insert  30  having a steeper annular sidewall  35  to vary the speed of the fluid exiting the nozzle. Therefore, several different deflector inserts  20  and nozzle inserts  30  can be provided having differently sized throughbores  23 ,  33  to facilitate use of the apparatus with different sizes of wireline  130 . 
     According to other embodiments, the shape of the impact surface  28  and the geometry of the confined area can be modified to obstruct the fluid flow to create the back pressure and deflect the fluids to the desired region around the wireline  130 . As shown in  FIG. 4  the cone angle of the impact surface  28  is 50° relative to the axis of the wireline  130 . This is the preferred embodiment. Alternatively, a steeper cone angle may be used, as shown in  FIG. 6 , where the cone angle of an impact surface  28   g  is 25° from the axis of the wireline  130 . The 50° cone angle provides a more consistent pressure region in the area of the wireline  130 . According to another alternative arrangement, a lens shaped or concave surface  281  can be provided. The lens shaped surface  281  has the advantage that the smooth edges reduce the risk of cavitation caused by the turbulent flow of fluid. 
     Modifications and improvements can be made without departing from the scope of the present invention. For example, the nozzle  31  is not required to be concentric. Instead, individual nozzle outlets can create individual jets of fluid flow that create the same cumulative effect by forming a pressure plug in the annulus. The working fluid is not limited, to water and can be any suitable fluid that has a viscosity below around 10 centipoise (0.1 Pa s). 
     Following from the above description and invention summaries, it should be apparent to those of ordinary skill in the art that, while the methods and apparatuses herein described constitute exemplary embodiments of the present invention, the invention contained herein is not limited to this precise embodiment and that changes may be made to such embodiments without departing from the scope of the invention as defined by the claims. Additionally, it is to be understood that the invention is defined by the claims and it is not intended that any limitations or elements describing the exemplary embodiments set forth herein are to be incorporated into the interpretation of any claim element unless such limitation or element is explicitly stated. Likewise, it is to be understood that it is not necessary to meet any of all of the identified advantages or objects of the invention disclosed herein in order to fall within the scope of any claims, since the invention is defined by the claims and since inherent and/or unforeseen advantages of the present invention may exist even though they may riot have been explicitly discussed herein.