WO1991019883A1

WO1991019883A1 - Tools for wells

Info

Publication number: WO1991019883A1
Application number: PCT/GB1991/000939
Authority: WO
Inventors: Paul Douglas Maxfield Gullett
Original assignee: Stirling Design International Limited
Priority date: 1990-06-12
Filing date: 1991-06-12
Publication date: 1991-12-26
Also published as: GB9013111D0

Abstract

A tool for use in wells has a body (10, 13; 72) which can pass through a casing string (28). The body includes a passage extending through the body for flowable material. The passage has an inlet and an outlet (19) and includes a valve for selectively closing and opening the passage. The body also has fingers (27) for anchoring the tool to the casing (28) at a predetermined position in the casing and means for forming a connection between the outlet (19) and an aperture (29) in the casing, so that the tool can be located at such an aperture (29) and a flowable material passed from said inlet to said aperture (29) via said passage and said outlet, with the valve open. In this way, selective sections of a well can be treated by a flowable material. For example, cement slurry can be supplied to a selected section.

Description

TOOLS FOR WELLS

The invention relates to tools for wells such as oil or gas wells.

A well is formed by a hole drilled through underground formations holding a required material such as gas or oil, into which a casing string is inserted. A cement slurry is pumped between the casing and the hole to hold the casing string in position and, in the portion of the formation which bears oil, the string is provided with inlets in the form of slots or holes through which the material can pass via the casing to the surface.

In some formations, the composition of the formation is uniform so that the material is extracted generally uniformly throughout the whole length of the casing within the bearing formation. However, in some bearing formations, the material may not be produced uniformly throughout the formation; there may be sections of the formation from which no material is received or from which only unwanted materials such as water only may be received.

In order to maximise the production of wells, it is increasingly common to drill the well hole not only vertically but also deviated and horizontally, so that it extends laterally into the bearing formation. The extent of these lateral runs may be up to 1000 metres or more. Such horizontal wells will encounter more variations in production along their length than will vertical wells. For example, some sections of a horizontal well may not yield material as a result of some reservoir discontinuity or some sections may pass through water bearing zones. In these circumstances, it may be desirable to perform selective treatments on specified sections of the hole. For example, a specified section may be cemented or may be supplied with a fluid which increases oil production or may be supplied with a gravel pack to form a filter round the casing. There may be other cases where a flowable material needs to be supplied at a specified point along the casing string.

According to a first aspect of the invention, there is provided a tool for a well comprising a hollow body for movement through a casing string and having an interior and an exterior, means defining a passage through the body from said interior to said exterior for exterior flowable material, means defining an inlet to said passage, means defining an outlet to said passage, a valve means arranged in said passage-defining means between said inlet means and said outlet means and operable to open and close said passage, means for anchoring the tool to a casing at a predetermined position in the casing string, means for closing said body downstream of said passage, means for forming a connection between said outlet means and an aperture in said casing at said predetermined position so that flowable material supplied to the interior of the hollow body passes through said inlet means and said passage, with the valve means open, and then passes through said outlet means and said connection means to said casing aperture.

According to a second aspect of the invention, there is provided a tool for use in pumping a flowable material to the exterior of a casing string through an aperture in a casing of the string comprising a generally cylindrical outer tube, means defining a hole in said outer tube, a generally cylindrical inner tube slidably received in said outer tube, means defining a hole in said inner tube, said inner tube hole means being alignable with said outer tube hole means by relative sliding of said inner tube and said outer tube, an open end to said inner tube defining an inlet for flowable material, means on an exterior surface of said outer tube movable from a retracted position to an extended position for engagement with an interior surface of a casing to define a closed chamber which communicates with the casing aperture and the outer tube hole means.

According to a third aspect of the invention, there is provided a method of supplying a flowable material to the exterior of a casing string comprising the steps of inserting a casing string into a well, inserting a tool into the casing string, halting the tool at a predetermined position along the casing string, anchoring the tool to the casing string at said predetermined position, forming a connection between an exterior of said tool and an aperture in said casing string, opening a normally closed passage between an interior of said tool and said connection, pumping flowable material to said body and through said passage, said connection and said aperture to the exterior of said casing string.

The following is a more detailed description of some embodiments of the invention, by way of example, reference being made to the accompanying drawings in which:-

Figure 1 is an axial cross-section through a portion of the casing string of an oil well showing a tool anchored relative to the casing string and in an inoperative position when no connection is made between an outlet of the tool and an aperture in the casing.

Figure 2 is a similar view to Figure 1 but showing flowable material supplied to the body and sleeves mounted on the body distended to engage an inner surface of the casing,

Figure 3 shows a similar view to Figure 2 but with an inner tube of the body slid into the body to open a valve and allow passage of the flowable material from the outlet to the aperture in the casing string.

Figure 4 is an axial cross-section through a hole of a horizontal oil well showing a casing string of the kind shown in Figures 1 to 3 within the hole, with the casing string being provided with a containment tool, the containment tool being in an inoperative position.

Figure 5 is a similar view to Figure 4 but showing the containment tool in an operative position and with a cement slurry supplied by the tool to the containment tool and to the annular space around the casing string, the annular space being only partially full,

Figure 6 shows a similar view to Figure 5 but with the annular space around the casing string almost completely full.

Figure 7 is an axial cross-section through a vertical oil well including a gas formation and showing a vertical casing string carrying an external casing packer and a containment tool and having within the casing string a tool of the kind shown in Figures 1 to 3 and supplying cement slurry to the annular space between the external casing packer and the containment tool.

Figure 8 is a similar view to Figure 7 but showing a subsequent stage in the cementing process.

Figure 9 is an axial cross-section through a portion of a casing string of an oil well showing a second form of tool anchored relative to the casing string and in an inoperative position when no connection is made between an outlet of the second form of tool and an aperture of the casing.

Figure 10 is a similar view to Figure 7 but showing the second form of tool in a disposition in which sleeves mounted on the body are distended to engage an inner surface of the casing.

Figure 11 is a similar view to Figure 8 but showing a valve between the second form of tool and the casing open for the passage of flowable material from the outlet of the second form of tool to the aperture of the casing. Figure 12 is a similar view to Figure 7 but showing the disposition of the second form of tool after flowable material has ceased to pass to the tool.

Referring first to Figures 1 to 3, the tool shown in those Figures comprises a tubular body 10 with a closed end 11 and an open end 12. An inner tube 13 is slidably received within the tubular body 10 and is provided on its outer surface 14 with an elongate annular recess 15 which receives an inwardly directed annular flange 16 at the open end 12 of the tubular body, so that engagement of the annular flange 16 with one or other of the ends of the recess 15 limits the sliding movement of the inner tube 13 into and out of the tubular body 10.

In the position shown in Figure 1 the inner tube 13 extends out of the tubular body 10 by its maximum extent.

The inner tube 13 is provided with a radially extending hole 17 which, in the position shown in Figure 1, is closed by a curved inner surface 18 of the tubular body 10. Similarly, the tubular body 10 is provided with a radially extending hole 19 that, in the position of the tool shown in Figure 1, is closed by the outer surface 14 of the inner tube 13.

The tubular body 10 has, adjacent its closed end 11, a cylindrical section of reduced diameter which forms a reservoir 20. A hydraulic fluid is contained within this reservoir 20 and the open end of the reservoir is closed by a piston 21. A passage 22 leads from the reservoir 20 to two outlets 23 on the exterior surface 24 of the tubular body 10 on opposite sides of the hole 19. At each outlet 23, an annular sleeve 25 of elastomeric material extends around the tubular body 10 and has its edges sealed to the tubular body 10. The function of these sleeves 25 will be described below.

The inner end of the inner tube 13 has an outer surface 26 of reduced diameter which is equal to the diameter of the reservoir 20. Again, the function of this portion will be described in more detail below.

Two or more fingers 27 are carried on the exterior surface of the tubular body 10 and are urged radially outwardly of the body by, for example, respective springs (not shown) . The exterior surface 24 of the tubular body 10 also carries a plurality of rollers 35 for engagement with the interior surface of a casing string during location of the tool.

The casing string 28 with which the tool is to be used is provided with a radially extending aperture 29 at required intervals along the casing string 28. The aperture 29 contains a one-way valve 30 allowing flow only from the interior of the casing string 28 to the exterior.

In addition, the interior of the casing string 28 is provided with two annular recesses 31 on opposite sides of the one-way valve 30 and is provided with an annular rebate 32 at a position spaced from the one-way valve 30 and facing in a direction away from the well head. A by-pass passage 37 (see Figure 3) is provided leading from an aperture on the exterior surface of the tubular body 10 to one side of the sleeves 25 and extending through the body 10 by-passing the sleeves 25 to an aperture on the other side of the sleeves 25. The function of this will be described below.

The tool is operated as follows.

First, the open end of the inner tube 13 is connected to a pipe 36 for the supply of flowable material to the tool. The pipe 36 may be any suitable tube commonly used in oil wells. The tool is then fed down the casing string 28 with the rollers 35 engaging the inner surface of the casing string 28 to ease the movement of the tool through the casing string 28. In view of the shape of the fingers 27 and the direction of the rebates 32, the fingers 27 will ride over the rebates as the tool is moved along the casing string 28.

Initially, the tool is positioned at a priming point in the casing string 28 where, a flowable material, such as cement slurry, is fed along the pipe 36 until the pipe is filled to a point adjacent the tool. Once this has been completed, the tool is moved from the priming point to a casing aperture 28 through which it is required to supply the cement slurry. The pipe 36 is provided with a pressure back valve (not shown) which limits the pressure in the cement slurry downstream of the valve so that the weight of cement slurry in vertical sections of the pipe 36 does not cause greater than required pressures in the cement slurry at the tool.

When the tool has reached the casing aperture 29 through which it is required to supply the cement slurry, the feed of the tool is halted. Next, a force is applied to the pipe 36 and hence to the tool in the direction of the arrow 34 in Figure 1 to draw the tool back towards the well head. This ensures that the fingers 27 engage in the associated rebate 32 and the arrangement is such that, when the sprags 27 are so engaged, the hole 19 in the tubular body 10 is axially aligned with the aperture 29 in the casing. In addition, this movement moves the inner tube 13 to the position shown in Figure 1.

The cement slurry is then passed down the pipe 36 and enters the tubular body 10 through the inner tube 13. However, since the hole 17 in the inner tube 13 is not aligned with the hole 19 in the tubular body 10, no flowable material passes from the interior of the tubular body 10 to the hole 19.

The pressure of the flowable material acts on the piston 21 and forces the piston 21 into the reservoir 20. This forces the hydraulic fluid out of the reservoir 20 and through the passage 22 to the outlets 23 and thence into the sleeves 25. This distends the sleeves 25 until they engage in the recesses 31 on either side of the aperture 29 in the casing string 28. In this way, an annular chamber is formed between the tubular body and the casing string 28. Further, the engagement of the sleeves 25 in the recesses 31 provides an additional anchor between the tubular body 20 and the casing string 28.

A force is then applied to the pipe 36 in the direction of the arrow 33 in Figure 2 and this pushes the inner tube 13 into the tubular body 10. As seen in Figure 3, this brings the hole 17 in the inner tube 13 into communication with the hole 19 in the tubular body. Thus, the flowable material can pass through the holes 17,19, through the chamber defined by the sleeves 25 and through the aperture 29 to the outer surface of the casing string 28. At the same time, the reduced diameter section 26 of the inner tube 13 engages the piston 21 to hold the piston 21 in a position in which the sleeves 25 are maintained distended.

If flowable material is to be supplied through other apertures 29 in the casing string 28, a force is applied to the tool via the supply tubing in the direction of the arrow 34 in Figure 1 and the sprags 27 are designed such that, at a pre-determined force, they will retract against the spring force and disengage the tool from the casing string 28. This movement also draws the inner tube 13 out of the tubular body, so releasing the piston for movement and allowing the sleeves 25 to resume their retracted position with the hydraulic fluid flowing back into the reservoir 20.

Two applications of the tool described above with reference to Figures 1 to 3 will now be described with reference to Figures 4 to 8.

In the first application shown in Figures 4 to 6, the tool is used to isolate a section of a horizontal well hole and supply a cement slurry to the isolated section. This is achieved in the following way.

A casing string 40 is inserted into the horizontal well hole 41, with, as is customary, drilling mud 42 between the casing string 40 and the well hole 41. Alternatively, water may be between the casing string 40 and the well hole 41.

The casing string 40 includes two axially spaced uphole and downhole containment tools 43 for closing the annular gap between the casing string 40 and the well hole 41 while at the same time allowing selective flow past the tool. Such a tool 43 is described in more detail in our co-pending U.K. Patent Application No. 9013110.3. It comprises a sleeve 44 of an elastomeric material connected at one end to a flange 45 on a casing section 46 and at the other end to a ring 47 slidable on the section 46. A number of tubes 48 are moulded into the sleeve 44, extend parallel to the axis of the casing string 40 and are equi-angularly spaced around the sleeve 44. In the downhole tool 43 shown in Figures 4 to 8, a hole (not shown) connects the space between the sleeve 40 and the adjacent exterior surface of the casing section 46 with a casing aperture 29 (not shown), rebates 32 and a recess 31, as described above with reference to Figures 1 to 3. The casing aperture 29 also leads to the exterior surface of the casing string 40 via a shuttle valve (not shown) . In the uphole containment tool (not shown) , the casing aperture 29 is not connected to the exterior surface of the casing string.

The tool 49 as described above with reference to Figures 1 to 3 is then fed through the casing string 40 at the end of a pipe 36 as described above with reference to Figures 1 to 3. It is halted by the upstream containment tool 43 when the fingers 27 have just passed the recess 31. The tool 49 is then anchored to the casing string 40, the sleeves 25 are distended, the valve opened and cement slurry pumped, all as described above with reference to Figures 1 to 3.

The cement slurry enters the space between the sleeve 44 and the casing section 46 and distends the elastomeric sleeve 44. This causes the sleeve 44 to engage the well hole 41 as shown in Figure 5. This moves the tubes 48 to a position in which they are closely adjacent the well hole 41. It also centralizes the casing string 40.

Once completed, the tool is released from the casing string 44 and is moved to a position adjacent the downhole containment tool 43. It is halted when the fingers 27 have just passed the recesses 31. The tool 49 is then anchored to the casing string 40 as described above.

The cement slurry first enters the space between the sleeve 44 and the casing section 46 and distends the elastomeric sleeve 44. This causes the sleeve 44 to enage the well hole 41 as shown in Figure 5. This moves the tubes 48 to a position in which they are closely adjacent the well hole 41. It also centralizes the casing string 40. No cement slurry passes to the aperture 29, being prevented from doing so by the shuttle valve. However, once the sleeve 44 has been filled, the pressure rises and opens the shuttle valve so that cement slurry is also supplied via the casing aperture 29, to the annular space formed behind the tool 43.

The annular space will begin to fill from the bottom of the well hole 41 with the cement slurry being displaced through the tubes 48. Eventually, however, at the lower end of the well hole 41 all the drilling mud will be displaced and the cement slurry will enter the tubes 48 of both containment devices 43. The tubes contain an additive X (such as sodium silicate) which reacts with an additive Y (such as calcium carbonate) provided in the cement slurry which causes the tubes to close. Thus, as the cement slurry commences passage through the tubes 49, they close, so ensuring that cement slurry is not lost. The cement slurry continues to fill- the annular space with an increasing number of tubes 48 closing as it does so. As seen in Figure 6, when the annular space is almost filled, only the uppermost tubes 48 will be passing drilling mud or water. Finally, the uppermost tubes 48 will close when the annular space is completely filled with cement.

It will be appreciated, of course, that the annular space need not be filled with cement slurry. It could be filled with any required flowable material such as chemicals to initiate oil release or a gravel pack to form an external filter or any other matter.

Referring now to Figures 7 and 8, there is shown the application of the tool in a vertical well.

It is a problem in such vertical wells to cement a casing string 50 in place when the oil bearing formation includes a gas formation 51. It is normal practice to cement the whole casing string 50 including the portion of the casing string 50 passing through the gas formation 51. It is a problem, however, that when the cement sets it passes through a period when its specific gravity decreases so that it exerts much less force than it does when in slurry form. In fact, there may be a period when it exerts only the same force as a corresponding volume of water. During this period, the pressure of the gas may be such that it can pass through the setting cement slurry destroying zonal isolation and causing communication even as far as the surface and this is plainly undesirable. In the arrangement now to be described with reference to Figures 7 and 8, this is avoided in the following way.

The casing string 50 includes a slotted liner 52 in the gas formation 51. The slotted liner 52 is beneficial because, unlike perforated liners, it provides a known flow restriction to the well bore. In addition, the slotted liner 52 can also be a "screen liner" when placing a gravel pack behind.

Next, a standard external casing packer 53 is provided around the casing string 50 just above the gas formation 51. This standard external packer is an elastomeric sleeve which can be distended to bear against the well hole.

A containment tool 43 of the kind described above with reference to Figures 4 to 6 is provided on the casing string 50 above the external casing packer 53. This containment tool 43 does not have the aperture 29 leading to the exterior of the casing string 50. The tool 49 described above with reference to Figures 1 to 3 is then moved to a position where it is adjacent an inlet to the space between the sleeve 44 and the adjacent casing section 46 of the tool 43 and it is operated as described above with reference to Figures 1 to 3 to pass cement slurry to distend the sleeve 44 until the walls of the well hole are contacted, to define a closed annular space between the tool 43 and the casing packer 53.

The tool 49 is then moved down the casing string 50 until it reaches a casing aperture similar to the casing aperture 29 leading to the interior of the external casing packer 50 and the exterior of the casing string 50 described above with reference to Figures 1 to 3 in relation to the downhole containment device 43, just above the external casing packer 53. Associated with this aperture are recesses and a rebate similar to the recess 31 and the rebate 32 described above with reference to Figures 1 to 3. The tool 49 is anchored in this position and operated as described above with reference to Figures 1 to 3 to pass cement into the closed annular space, with displaced drilling mud leaving through the tubes in the containment tool, which close as the cement slurry reaches the tubes, as described above with reference to Figures 4 to 6.

While it is setting, the cement slurry is isolated from the gas formation by the external packer 53. Thus, there can be no possibility of gas passing up the well hole. In addition, the by-pass 37 provided in the tool 55 causes the hydrostatic pressure in the drilling mud within the casing string 50 is maintained on the gas formation, tending to hold the gas in the formation.

Referring next to Figure 8, the tool is then moved to a position above the containment device 43 adjacent to circulating valve 54. The tool 55 is then operated as described above with reference to Figures 1 to 3 to pass cement slurry into the remainder of the annular space between the casing string 50 and the well hole, the drilling mud being displaced from the top of the well. Again, the hydrostatic pressure of the drilling mud is^' maintained on the gas formation by a by-pass in the tool 55.

Referring next to Figures 9 to 12, the second form of tool shown in those Figures has parts common with the tool of Figures 1 to 3. Those common parts will not be described in detail and will be given the same reference numerals.

The second tool has a tubular body 10 with up hole and down hole open ends 70,71. An inner tube 72 is slidably received in the tubular body 10 and is provided at its down hole end with a closed end • 73 of greater diameter than the remainder of the tube 72 and received in a co-operating recess 74 located at the down hole open end 71 of the tubular body and opening onto the open end 71. The axial extent of the recess 74 limits the sliding movement of the inner tube 72 and the body 10 in an up hole direction.

The up hole end of the tube 72 is provided with a flange 75 which, in the position of the parts shown in Figure 8, is axially spaced in an up hole direction from the up hole open end 70 of the body 10. This flange 75 limits the sliding movement of the inner tube 72 and the body 10 in a down hole direction.

The inner tube 72 contains a piston 21 which forms a reservoir 20 between the piston 21 and the closed end 73 of the inner tube 72. The piston 21 is urged towards the position shown in Figure 9 by a spring 86. A hydraulic fluid is contained within this reservoir 20 and a passage 22 leads from the reservoir 20 and, in the positions of the body 10 and tube 72 shown in Figure 8, radially through the tube 72 and the body 10 and then axially through the body 10 to two outlets 23 on the exterior surface of the body 10 on opposite sides of a radial hole 19 provided in the body 10.

At each outlet 23, an annular sleeve 25 of elastomeric material is provided, as described above with reference to Figures 1 to 3.

The inner tube 72 is provided with a radially extending hole 76 at a position spaced in an up hole direction from the radial hole 19 in the body 10, in the relative positions of these parts shown in Figure 9. The open end of the inner tube 72 is provided with a section 77 of restricted diameter which carries a sleeve 78 for sliding movement between up hole and down hole positions. The up hole end of the sleeve is provided with a head 79 and a spring 80 extends between the head 79 and the section 77 to urge the sleeve 78 into the up hole position (as shown in Figure 8). The down hole end of the sleeve 78 carries a plug 81 which, in the position shown in Figure 8, closes the restricted diameter section 77, for a purpose to be described below.

The exterior surface of the tubular body 10 is provided with fingers 27 and rollers 35, as described above with reference to Figures 1 to 3. The casing string 28 with which the tool is to be used is provided with an aperture 29 and valve 30, as described above with reference to Figures 1 to 3 and with annular recesses 31 (see Figure 9) and an annular rebate 32, also as described above with reference to Figures 1 to 3.

The tool is operated as follows.

First, the up hole end of the inner tube 72 is connected to a pipe 36 and is fed down the casing string 28 until the tool reaches the casing aperture 29 through which it is required to supply flowable material, as described above with reference to Figures 1 to 3. Next the tool is engaged with casing string 28 by use of the fingers 27, as described above with reference to Figures 1 to 3, so that the tool is in the position shown in Figure 9.

Next, the flowable material, which may be a cement slurry, is passed down the pipe 36 and into the sleeve 78. The pressure of the material moves the sleeve 78 in a down hole direction against the force of the spring 80 so that the plug 81 moves out of engagement with the section 77 and allows the material to enter the interior of the tube 72. The pressure of the material within the tube 72, forces the piston 21 in a down hole direction, so forcing hydraulic fluid from the reservoir 20 through the passage 22 to the sleeves 25 to form an annular chamber between the body 10 and the casing string 28, as described above with reference to Figures 1 to 3. This is shown in Figure 10.

A force is then applied to the pipe 36 in a down hole direction so that the inner tube 72 slides in a down hole direction relative to the body 10. This breaks the passage 22 (so maintaining the pressure in the sleeves 25) and brings the flange 75 into engagement with the body 10 and the hole 76 in the inner tube 72 into register with the hole 19 in the body 10. This is shown in Figure 11. The flowable material thus flows through the holes 76,19 and the chamber and then through the casing aperture 29 to the exterior of the casing string.

When sufficient material has been pumped to the exterior of the casing string, pumping ceases. The reduction of pressure within the inner tube 72 allows the spring 80 to move the sleeve 78 in an up hole direction so drawing the plug 81 into the section to close the section 77. This is shown in Figure 12. The pressure within the tube 72 is reduced by the volume occupied by the plug.

The tool can be moved to other positions in the casing string as described above with reference to Figures 1 to 3.

It will be appreciated that the maintenance of the relative positions of the inner tube 72 and the body 10 shown in Figure 11, when material is being supplied to the exterior of the casing string, is not dependent on the maintenance of pressure in the flowable material. Thus, if this pressure varies, there will be no relative movement between the body 10 and the tube 72.

The tool described above with reference to Figures 9 to 12 can be used in any of the applications described above with reference to Figures 4 to 8, in place of the tool described above with reference to Figures 1 to 3.

It will be appreciated, of course, that the tools described above with reference to Figures 1 to 3 and Figures 9 to 12 may have uses other than those described above with reference to Figures 4 to 8. In particular, it need not be used in oil wells. It could be used in gas or other wells and well completion tubulars.

It will be appreciated that the use of the piston and reservoir is not essential. The sleeves 25 may be distended by the cement slurry entering the tool. Further, the valve formed between the tubes may be replaced by a bull valve or a check valve.

In all the embodiments described above with reference to the drawings, once all zones have been filled with cement slurry, the tool is moved to a reverse circulating valve in the casing where it is anchored to the casing. Fluid is then pumped down the outside of the casing and into the tool so washing the cement slurry out of the tool and back to the surface. This prevents the cement slurry solidifying in the tool.

Claims

1. A tool for a well comprising a hollow body (10,13; 10,72) for movement through a casing string (28) and having an interior and an exterior and closed at a downstream end, a passage for flowable material through the body from said interior to said exterior, an inlet (13;72) to said passage, an outlet (19) to said passage, a valve means arranged in said passage between said inlet (13;72) and said outlet (19) and operable to open and close said passage, means (27) for anchoring the tool to a casing string (28) at a predetermined position in the casing string (28), means (25) on the body for forming a connection between said outlet (19) and an aperture (29) in said casing string (28) at said predetermined position so that flowable material supplied to the interior of the hollow body (10,13; 10,72) passes through said inlet and said passage, with the valve means open, and then passes through said outlet (19) and said connection means (25) to said casing aperture (28).

2. A tool according to claim 1 wherein the body comprises a generally cylindrical outer tube (10) and an inner tube (13;72) slidably received in the outer tube (10), an end of the inner tube (13;72) forming said inlet means, and the inner tube and the outer tube having respective holes (17,19) in curved surfaces thereof, with the hole (19) in the outer tube forming said outlet, the inner tube (13;72) and the outer tube (10) being relatively slidable to bring the respective holes (17,19) into and out of communication to provide said valve means.

3. A tool according to claim 2 wherein the connection forming means comprises means (25) on an outer surface of said generally cylindrical outer tube (10) movable from a retracted position adjacent said surface to an extended position for engagement with an interior surface of a casing string (28) to define a ' closed chamber which communicates with the casing aperture (28) and the outlet (19) of the outer tube (10).

4. A tool according to claim 3 wherein said movable means comprises two annular sleeves (25) of an elastomeric material extending around the outer surface of the outer tube (10) on opposite sides of said outlet (19), the sleeves (25) being movable from a retracted position to a distended position in which, in use, said sleeves contact the casing (28) on opposite sides of the casing aperture (29) to form said chamber.

5. A tool according to claim 4 wherein the body includes a reservoir (20) of a fluid, the fluid from said reservoir being selectively transferable to said sleeves (25) to distend said sleeves.

6. A tool according to claim 5 wherein the reservoir includes a piston (21) movable between first and second positions to effect said transfer of fluid from the reservoir (20) to the sleeves (25).

7. A tool according to claim 6 wherein the piston (21) is moved from said first to said second positions by the pressure of said flowable material in the inner tube (13;72) acting thereon.

8. A tool according to claim 7 wherein the reservoir is formed in the outer tube and wherein an end of the inner tube (13) within said outer tube (10) holds said piston in said second position when said inner tube (13) is slid into said outer tube to bring said holes (17,19) into communication.

9. A tool according to claim 8 wherein body closing means comprises a closure of said outer tube (10), said piston (21) being slidable within said tube (10) and said reservoir (20) being formed between the piston (21) and the closed end of the outer tube (10).

10. A tool according to claim 7 wherein the reservoir (20) is formed in the inner tube (72), the connection between said reservoir (20) and said sleeves (25) being interrupted when the inner tube (72) moves relatively to said outer tube (10) to bring said holes (17,19) into communication.

11. A tool according to claim 1 wherein the body carries at least two fingers (27) on an exterior surface thereof for engagement with respective recesses (32) on an interior surface of a casing string (28) to locate the body relative to a casing aperture (29).

12. A tool according to claim 11 wherein each finger (27) is urged resiliently radially outwardly of the body (10).

13. A tool according to claim 12 wherein each finger (27) is retractable against the resilient force upon the application to the body (10) of a predetermined axial force.

14. A tool according to claim 12 wherein a plurality of rollers (35) are provided on an exterior surface of the body (10) for contacting the interior surface of an associated casing string (25) to assist the passage of the body through a casing string (28) .

15. A tool for use in pumping a flowable material to the exterior of a casing string (28) through an aperture (29) in a casing of the string comprising a generally cylindrical outer tube (10), a hole (19) in said outer tube, a generally cylindrical inner tube (13;72) slidably received in said outer tube, a hole (17) in said inner tube, said inner tube hole means (17) being alignable with said outer tube hole (19) by relative sliding of said inner tube and said outer tube (13,72;10), an open end to said inner tube (13,72) defining an inlet for flowable material, means (25) on an exterior surface of said outer tube movable from a retracted position to an extended position for engagement with an interior surface of a casing to define a closed chamber which communicates with the casing aperture and the outer tube hole means.

16. A tool according to claim 15 wherein chamber defining means comprise two annular sleeves (25) of an elastomeric material extending around the outer surface of said outer tube (10) on opposite sides of said outer tube hole (19), the sleeves (25) being movable from a retracted position to a distended position for contacting said casing.

17. A method of supplying a flowable material to the exterior of a casing string comprising the steps of inserting a casing string (28) into a well, inserting a tool (53) into the casing string, halting the tool (53) at a predetermined position along the casing string, anchoring the tool (53) to the casing string at said predetermined position, forming a connection between an exterior of said tool and an aperture (29) in said casing string, opening a normally closed passage between an interior of said tool and said connection, pumping flowable material to said body and through said passage, said connection and said aperture to the exterior of said casing string.

18. A method according to claim 17 wherein the connection forming step comprises moving chamber-forming means (25) on an exterior surface from a retracted position to an extended position in which said means engage the casing string (28).

19. A method according to claim 18 wherein the chamber-forming means comprise two annular sleeves (25) of elastomeric material extending around an outer surface of said tool (53), said sleeves being distended to move said sleeves to said extended position.

20. A method according to claim 19 and comprising distending said sleeves (25) by pumping fluid from said body to said sleeves.

21. A method according to claim 17 wherein the step of opening said normally closed passage comprises anchoring an outer tube (10) of the tool (53) to the casing and then sliding an inner tube (13;72) of the tool, which is received in said outer tube (10) relative to said inner tube (13;72) to bring into register respective holes (17,19) in said inner tube and said outer tube.

22. A method according to claim 17 and further comprising halting pumping of said flowable material, closing said open passage, breaking said connection between the exterior of the tool and the aperture in said casing string, releasing said anchor between the tool and the casing string and moving the tool within the casing string.

23. A method according to claim 22 and comprising, after moving the tool within the casing string, pumping fluid around the exterior of the casing ^• and into the body to remove flowable material from the body.