Abstract:
A downhole tool for use in a cased or lined well bore ( 40 ), the tool including a barrier ( 36 ) arranged on an outer surface of the tool. The barrier may be of a resilient material so that it can be deformed on actuation to control the passage of fluid between the tool and the casing or liner. Fluid flow is thus selectively diverted through flow paths ( 22 ) in the tool. Embodiments are described for actuating the barrier by hydraulic means and for filtering the fluid within the flow paths.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This patent application claims priority from PCT/GB03/05337, having an international filing date of 8 Dec. 2003, and a priority date of 9 Dec. 2002. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not Applicable 
   THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
   Not Applicable 
   INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
   Not Applicable 
   BACKGROUND OF THE INVENTION 
   The present invention relates to downhole tools for use in cased or lined well bores for the oil and gas industry, and in particular to a downhole tool which includes a barrier between the tool body and well bore wall which is actuable to control fluid flow past the tool. 
   It is considered desirable when drilling for oil or gas to maintain a clean interior in the casing or liner of the drilling well. For this purpose, well cleaning equipment is well known and comes in a variety of different forms, including casing scrapers, brushes and circulation tools. Such equipment is used to free the well tubing from debris particles, cement lumps, rocks, congealed mud and so on. 
   Indeed well clean-up apparatus is used in an attempt to clean the casing or other well tubing of even smaller particles or debris such as oxidation lumps, scale and burrs for example. 
   More advanced clean-up tools have also been developed which filter the well fluid downhole. This is done to remove the debris prior to production of the well. Such filtering tools generally operate by providing a barrier in the annulus between the tool body and the wall of the well casing or liner. The barrier causes diversion of fluid flowing past the tool into the tool. Once inside the tool the fluid is passed through a filter and then directed back into the annulus on the opposite side of the barrier. Such a tool is that disclosed in GB 2335687. 
   A major disadvantage of these tools is that, as filtering is required in one flow direction through the tool, a second flow path through the tool must be provided for fluid flow in the opposite direction so that the tool can be run in and/or pulled out of the well bore without re-dispersing the collected debris. This additional flow path restricts the volume of fluid which can pass the tool and may be prone to clogging if unfiltered well fluid is required to take this flow path on running in. 
   It is an object of the present invention to provide a downhole tool which allows for selective bypass of fluid around the outer body of the tool. 
   It is a further object of at least one embodiment of the present invention to provide a downhole tool with an actuable barrier which can be used to selectively divert fluid through the tool body. 
   It is a yet further object of at least one embodiment of the present invention to provide a downhole tool with an actuable barrier which can be used to selectively divert fluid passing the tool body through the tool body when the tool is run-in, pulled out or is stationary within the well bore. 
   BRIEF SUMMARY OF THE INVENTION 
   According to a first aspect of the present invention there is provided a downhole tool for use in a cased or lined well bore, the tool comprising a body connectable in a work string, a fluid flow path through the tool body and a barrier located at an outer surface of the tool, wherein the barrier is actuable to control fluid flow passing the tool and selectively divert fluid flow through the flow path. 
   When the barrier is not actuated the tool allows fluid flow to run unimpeded in the annulus between the tool body and the wall of the well bore. Conversely, the barrier may be actuated to cause passage of fluid through the tool. 
   Preferably the barrier comprises a resilient member which when acted upon by actuating means deforms to extend the member towards a wall of the well bore. The resilient member may be a rubber ball. Alternatively the resilient member may be an inflatable bladder. 
   Advantageously the barrier includes a surface engageable with the well casing or liner. The surface may provide a seal such that fluid is substantially restricted from passing the tool. Thus the barrier is circumferentially arranged on the outer surface of the tool body. Further the barrier may be rotatable with respect to the tool body. Advantageously also the surface is a wiper so that as the tool is moved within the well bore the casing or liner is cleaned when the surface is engaged. 
   Preferably the actuating means is a hydraulic actuator. Hydraulic fluid may flow directly against the resilient member to cause deformation. Alternatively the fluid may act upon a piston member, wherein movement of the piston member causes the resilient member to deform. In a first embodiment the resilient member may be initially held in compression by a retainer and the piston member releases the retainer. 
   Advantageously, well fluid within the well bore may be the hydraulic fluid to operate the actuating means. 
   Alternatively the actuating means may include a ball valve. Thus the barrier may become actuable through a drop ball released at the surface and carried through a bore in the work string. To selectively actuate the barrier the drop ball may be deformable as are known in the art. This is as disclosed in WO02/061236 for example. 
   The work string may be a pipe string, coiled tubing or a wireline. 
   Preferably the tool includes an axial bore for fluid circulation through the work string. Preferably also the tool body is substantially cylindrical to provide the annulus between the tool and the wall of the well bore. 
   There may be a plurality of fluid flow paths through the tool body. One or more of the fluid flow paths may include a filter so that well fluid can be filtered downhole. Alternatively the fluid flow path may form a hydraulic line for the actuation of a feature of the downhole tool. Preferably the fluid flow path has an inlet and an outlet. Preferably the inlet and outlet are each arranged on an outer surface of the tool. Preferably also the inlet and outlet are arranged on either side of the barrier. 
   According to a second aspect of the present invention there is provided a downhole tool for collecting loose debris particles within a well bore, the tool comprising a body connectable in a work string, a fluid flow path through the tool body including means for filtering debris particles and a barrier located at an outer surface of the tool, wherein the barrier is actuable to control fluid flow passing the tool and selectively divert fluid flow through the flow path. 
   The filtration means may be a wire screen sized to prevent particles of a predetermined size from passing therethrough. It will be appreciated however that many different types of filtration apparatus may be used, including permeable textiles, holed tubes or cages, and so on. The filtration means need not be limited to any one particular type of screen or filter, but may rather comprise of a plurality of filters in series; the filters being potentially of varying type and permeability. 
   The tool may also act as a collector or trap for debris and the like. For example, a trap may be provided on the up-stream side of the filter means for storing the filtered debris. 
   Optionally, a separate filter may be provided for each filtered flow path. 
   Preferably the barrier comprises a resilient member which when acted upon by actuating means deforms to extend the member towards a wall of the well bore. The resilient member may be a rubber ball. Alternatively the resilient member may be an inflatable bladder. 
   Advantageously the barrier includes a surface engageable with the well casing or liner. The surface may provide a seal such that fluid is substantially restricted from passing the tool. Thus the barrier is circumferentially arranged on the outer surface of the tool body. Further the barrier may be rotatable with respect to the tool body. Advantageously also the surface is a wiper so that as the tool is moved within the well bore the casing or liner is cleaned when the surface is engaged. 
   Preferably the actuating means is a hydraulic actuator. Hydraulic fluid may flow directly against the resilient member to cause deformation. Alternatively the fluid may act upon a piston member, wherein movement of the piston member causes the resilient member to deform. In a first embodiment the resilient member may be initially held in compression by a retainer and the piston member releases the retainer. 
   Advantageously, well fluid within the well bore may be the hydraulic fluid to operate the actuating means. 
   Alternatively the actuating means may include a ball valve. Thus the barrier may become actuable through a drop ball released at the surface and carried through a bore in the work string. To selectively actuate the barrier the drop ball may be deformable as are known in the art. This is as disclosed in WO02/061236. 
   The work string may be a pipe string, coiled tubing or a wireline. 
   Preferably the tool includes an axial bore for fluid circulation through the work string. Preferably also the tool body is substantially cylindrical to provide the annulus between the tool and the wall of the well bore. 
   There may be a plurality of fluid flow paths through the tool body. Preferably the/each fluid flow path has an inlet and an outlet. Preferably the inlet and outlet are each arranged on an outer surface of the tool. Preferably also the inlet and outlet are arranged on either side of the barrier. 
   According to a third aspect of the present invention there is provided a method of controlling fluid flow in a well bore, comprising the steps:
         (a) running a tool having an actuable barrier on a work string downhole;   (b) creating relative movement between the fluid in the well bore and the tool;   (c) actuating the barrier to control fluid flow passing the tool by varying the cross sectional area of the annulus between the tool and the wall of the well bore.       

   The method may further include the step of selectively diverting fluid flow through a flow path in the tool. 
   Preferably the method may include the step of actuating the barrier until the barrier sealingly engages the wall of the well bore and thus substantially restricts fluid flow passing the tool. 
   Additionally the method may include the step of filtering the fluid flow through the flow path in the tool. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings of which: 
       FIG. 1  is a part cross-sectional view through a downhole tool according to a first embodiment of the present invention; 
       FIG. 2  is a part cross-sectional view through a downhole tool according to a second embodiment of the present invention; and 
       FIG. 3  is a part cross-sectional view through a downhole tool according to a third embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference is initially made to  FIG. 1  of the drawings, which illustrates a downhole tool, generally indicated by reference numeral  10 , according to a first embodiment of the present invention. Tool  10  comprises a generally cylindrical body  12  having an axial bore  14  therethrough. At an upper end  16  of the tool  10  there is provided a box section (not shown) and at the lower end  18  of the tool  10  there is a pin section (not shown), as are known in the art, for connecting the tool  10  to a work string (not shown). 
   Around an inner mandrel  11  of the body  12  there is located a sleeve  20 . Sleeve  20  provides an inlet port  22  of annular shape at the upper end  16  of the tool  10 . At the lower end  18  is arranged a stop surface  24  to join the sleeve  20  to the mandrel  11 . In a portion of the wall  26  of the sleeve  20 , towards the lower end  18 , there is a filter  28 . Filter  28  is a cylindrical screen which can filter loose debris and particles from fluid passing through it. Together the sleeve  20  with filter  28  and stop  24  provide a trap  30  where debris will collect when fluid flow is in a direction marked by arrows A. 
   Between the mandrel  11  and the sleeve  20  are located ports  32 . Although a single port  32  is shown, typically there will be a number of ports symmetrically arranged around the mandrel  11 . However sufficient space around the ports  32  is provided for the entry of larger pieces of debris to the trap  30 . Mounted at an outlet  34  of the port  32  is an inflatable seal  36 . Seal  36  is circumferentially arranged around the sleeve  20 . Seal  36  is made of a resilient rubber which when inflated from the inside will increase the size of the seal to fill the annular space  38  between the tool  10  and the casing/liner wall  40  of the well bore  42 . When deflated the seal  36  is afforded some protection by a lip  43  on sleeve  20  which directs fluid toward the casing  40 . 
   Within the mandrel is located a ball valve, generally indicated by reference numeral  44 . Valve  44  comprises a seat  46  which is initially held to the mandrel  11  by a shear pin  48 . A stop  50  is also provided on the mandrel  11 . 
   In use, tool  10  is run in well bore  42  through casing  40  on a work string (not shown). As shown on the left hand side of  FIG. 1 , the seal  36  is initially deflated so fluid can flow upstream or downstream of the tool shown by arrows B. This provides a large circulation path for the fluid. Fluid can also flow through the axial bore  14  independently. Valve seat  46  is located across the port (s)  32  to prevent the seal inflating. The valve seat is held in position by the shear pin  48 . 
   When fluid is required to be filtered, such as on pulling out the tool  10  from the well bore  42 , a ball  52  is dropped from the surface into the axial bore  14 . Ball  52  travels under fluid pressure to the seat  46  where it blocks the passage of fluid through the bore  14 . Pressure then builds up behind the ball, sufficient to shear the pin  48  and move the seat  46  downwards. The seat  46  will fall to the stop  50 , whereupon fluid within the bore can now flow through port  32  to outlet  34  and fill the seal  36 . Seal  36  consequently expands by inflation to fill the annulus  38  and prevent fluid flow down the outside of the tool  10  between the sleeve  20  and the casing  40 . The fluid flow to the seal  36  is regulated by a check valve  54  located in the port  32  to prevent over inflation of the seal  36 . 
   Seal  36  now engages the casing  40 , as shown in the right hand side of  FIG. 1 . Seal  36  has a surface which is suitable for continuous contact to the casing  40  while the tool is moved within the casing  40 . This surface is typically a roughened rubber surface such as knobbles which reduce the surface contact area without reducing the quantity of fluid flow passed the tool  10 . When tool  10  is moved, fluid is now directed into the annular port  22  and travels into the trap  30 . The fluid is filtered by passing through filter  28  and the clean fluid exits the tool below the seal  36 . Any debris filtered from the fluid is caught within the sleeve  20  and falls against stop  24  or is held in filter  28 . Trap  30  can be emptied when the tool  10  is removed from the well bore  42 . 
   If filtering is not required at any time, that is if the tool is to be further plunged into the well, fluid pressure is increased through the axial bore  14 . As valve  54  is closed, the increased pressure acts upon the drop ball  52 . Drop ball  52  is deformable and thus will be extruded through the seat  46  and fall through the axial bore  14 . A ball catcher can be located further down the work string to retrieve the ball  52 . When extruded the pressure drop in the bore  14  causes the check valve  54  to open and fluid is released from the seal  36 . Seal  36  then deflates, just before spring  56  returns the valve seat  46  back over the port  32 . The tool  10  is thus reset and seal  36  can be actuated as often as required by repeating the process. 
   Reference is now made to  FIG. 2  of the drawings which illustrates a downhole tool, generally indicated by reference numeral  210 , according to a second embodiment of the present invention. Like parts to those of  FIG. 1  have been given the same reference numeral with the addition of  200 . The filter and trap arrangement are included in the tool but are omitted from the Figure to provide better clarity to the sealing arrangement. 
   In this second embodiment the valve seat  246  extends through the sleeve  220  to provide a retainer cup  70  in the annulus. Engaging slots are provided between the sleeve  220  and the cup  70  to prevent a fluid path being provided at this position on the tool. 
   Initially the retainer cup  70  retains a rubber ring  72  against the sleeve  220  to provide the passage past the tool. On dropping the ball  252 , to a similar ball valve arrangement, the cup  70  is moved downwards and the ring expands to fill the annulus  38 . The tool  210  can then operate in an identical manner to the tool  10  of  FIG. 1 . 
   Reference is now made to  FIG. 3  of the drawings which illustrates a downhole tool, generally indicated by reference numeral  310 , according to a third embodiment of the present invention. Like parts to those of  FIG. 1  have been given the same reference numeral with the addition of  300 . 
   In likeness to the previous example embodiment, the barrier in the embodiment of  FIG. 3  is a rubber ring  372 . The ring  372  is shown in a non-actuated position in the left hand section of the drawing, where it is compressed against sleeve  320  by a drag block  370 . The drag block  370  is sufficiently slotted or ported so as to enable fluid to flow through it, yet nevertheless it is also adapted to undergo movement when drag forces resulting from a predetermined flow of fluid act on it. Thus in use, fluid can flow over the outside of the tool, by the route of arrow B. Here the ring  372  is compressed and held in position by the drag block  370 . When fluid pressure is increased by a predetermined amount or, alternatively, the tool is pulled from the well bore, an increase in pressure will occur on the surface  374  of each drag block  370 . Drag block  370  will then move relative to the tool  310  and the ring  372  will be released to expand and fill the annulus  38 , thereby redirecting fluid flow through the tool in the direction of arrow A. The advantage of this embodiment is that the barrier is actuated by the well fluid and a second actuating fluid is not required. 
   The principal advantage of the present invention is that it provides a downhole tool wherein fluid passing the tool can be selectively diverted through the tool. 
   A further advantage of the present invention is that it provides a downhole tool wherein fluid can be filtered within a well bore when the tool is run in or pulled out of the well bore. 
   It will be appreciated by those skilled in the art that further modifications could be made to the invention herein described without departing from the scope thereof. For instance the ball valve could be released by inserting a smaller steel ball to block the port  32  to allow pressure to build up on the deformable ball  52 .