Device and method for use in a borehole

Abstract

Device for use in a bore with a tubular element having a passage, characterized in that a first tool is attached to the tubular element, the first tool is designed in such a way that it can be set into a state to catch a first object delivered through the passage and performs an operation after catching the first object, and that a second tool is attached to the tubular element and is designed to transition to a state for catching a second object which is guided through the passage in response to the operation.

Description

The present invention relates to an apparatus and a method for use in a wellbore according to the pre-characterizing parts of claims 1 and 8, which apparatus and method are preferably used to complete multiple zone wells.To increase production from a subterranean well, the layers of the well may be fracture using a pressurized fracturing fluid containing a support agent or other treatment fluid such as acid. The layers are typically cracked one at a time by supplying a cracking fluid to the layer to be cracked and isolating the other layers.A conventional fracturing device includes surface pumps that pressurize the fracturing fluid that can be transferred underground via the central passage. The string extends underground through a wellbore traversing the various layers to be fracture; and the string may include valves (e.g., sleeve valves) substantially aligned with the layers such that the valves may be used to control fluid communication between the central passage of the string and the layers. Therefore, when a fracturing operation is performed on one of the layers, one of the valves is opened so that the fracturing fluid can be communicated through the opened valve to the associated layer.To operate the valves remotely from the surface of the bore, the valves may include many ball seats of various sizes. More specifically, to select and activate the valves, balls of various sizes may be dropped into the central passage of the string from the surface of the bore. Each ball size may be uniquely associated with one of several valves, such that a particular ball size is used to actuate a particular valve. The smallest ball opens the deepest valve. A free-falling ball sticks or is "captured" by a ball seat of the selected valve. In order to distinguish between the different valves, each ball seat of the rod has a different diameter.After a ball rests on a ball seat, fluid flow through the central passage of the string is restricted. This allows fluid pressure to be applied from the surface of the bore for the purpose of exerting a downward force on the ball. The ball seat is attached to a sleeve of the valve to transmit the force to the valve to cause the valve to open.The annular area occupied by each ball seat restricts the cross-sectional flow area through the string (even in the absence of a ball), and the addition of each valve (and ball seat) to the string further restricts the cross-sectional flow area through the central passage of the string as the flow through each ball seat becomes progressively narrower as the number of ball seats increases. Therefore, a large number of valves can substantially reduce the cross-sectional flow area through the string.As an alternative to the ball seat disposed in the string as part of the valves, a single activating tool may be selectively positioned in the central passage of the string to actuate the valves. More specifically, a valve operating tool may be lowered underground by a transport mechanism (e.g., a mud line) to the valve to be opened and to close previously opened valves.Such tools and methods are known from the prior art, for example from U.S. Pat. No. 4,194,561 a, U.S. Pat. No. 5,244,044 a, U.S. Pat. No. 2004 / 0 118 564 A1 and WO 2004 / 088 091 A1.One challenge with this alternative is that the fracturing pumps at the surface of the bore must idle after each layer has been fractured. Further, typically each valve is closed after its respective fracturing operation. Re-opening the valves requires the seals and seal surfaces to withstand the fracturing process without damage.Therefore, there is a need for a method and apparatus in which the above problems are alleviated.It is therefore an object of the invention to provide an apparatus and a method in which the above-mentioned problems are reduced.This object is achieved by the features of claims 1 and 8.Further embodiments of the invention can be taken from the dependent claims and the following description.The invention is explained in more detail below with reference to the exemplary embodiments shown in the appended drawings. FIG. 1 shows a fracture device according to an embodiment of the invention. FIGS. 2 and 3 show a valve in a closed state and before it is placed in a ball-trapping state according to an embodiment of the invention. FIG. 4 shows the valve in a closed state and after it has been set in a ball-trapping state according to an exemplary embodiment of the invention. Figures 5 and 6 show the valve in its open state according to an embodiment of the invention. FIG. 7 is a flow diagram illustrating a method for fracture of layers in a multi-layer bore according to an embodiment of the invention. FIG. 8 is a perspective view illustrating surface features at a lower end of a collar sleeve of a valve according to an embodiment of the invention. FIGS. 9 and 10 illustrate various states of a valve using a C-ring as a ball catcher according to an embodiment of the invention. FIG. 11 is a perspective view of a valve housing according to another embodiment of the invention.Referring now to Figure 1, there is shown an embodiment 10 of a fracture apparatus including a string 12 extending into a wellbore 11 having N layers 15 (layers 15 1, 152, 153... 15 N-1 and 15 N shown as an example) of the bore. As shown in FIG. 1, the string 12 includes valves 14 (valves 14 1, 142, 143... 14 N-1 and 14 N shown as examples), each of which is associated with a particular layer 15. For example, valve 14 is associated 3 with layer 15 3. Thus, to fracture a particular layer 15, the associated valve 14 (initially run underground in a closed state) is opened by dropping a drop ball and pumping up which moves the sleeve valve to the open state (as described below) to allow communication between the central passage of the string 12 and the associated layer 15. This connection in turn allows aeration fluid and pressure to be supplied to the associated layer 15.In some embodiments of the invention, each valve 14 controls communication between a central passage of the string 12 and an annular region surrounding the valve 14. When the string 12 runs underground, all valves 14 are initially closed. However, the valves 14 are opened one after another in a predetermined sequence (as will be described below) to fracture the sheets 15.In some embodiments of the invention, the valves are opened in a sequence starting at the bottom of the string 12 with the deepest valve 14 N advancing up to the next immediately adjacent valve 14, then going to the next immediately adjacent valve 14, etc. The valve 14 N is therefore opened before the valve 14 N-1 the valve 14 3 is opened before the valve 14 2 etc.For the purpose of opening a particular valve 14, an object to be freely dropped or pumped down is exposed from the surface of the bore into the central passage of the string 12. For the sake of simplicity, it is assumed in the following description that the object is a spherical ball. However, in other embodiments of the invention, a different type of object may be used and / or objects of different shapes may be used.In some embodiments of the invention, a ball of the same dimension may be used (although balls of different size may be used in other embodiments of the invention) to open all of the valves 14, since only one of the previously unopened valves (referred to herein as the "target valve") is in a "ball-trapping state" at a particular time. In some embodiments of the invention, the balls that have been pumped or dropped underground to open one of the valves 14 may have diameters that differ by less than 0.32 cm.As described below, initially, all of the valves 14 are closed and none of the valves 14 is in a ball-trapping state. When a particular valve 14 opens, the valve 14 subsequently places the next valve 14 in the ball-trapping state. In the ball catch state, the valve 14 forms a seat having a reduced cross-sectional flow passage to catch a ball dropped in the central passage of the string 12. In the sequence described above, the unopened valves 14 disposed above the unopened valve 14 that is in the ball catching state allow the ball to pass through.After the ball becomes stuck in the ball catcher of the target valve 14, the ball limits, if not completely seals, the central passage of the string 12 below the ball, so that fluid pressure can be applied across the ball to generate a force that causes the valve to open, as further described below.In a more specific example, a ball may be dropped from the bore surface into the central passage of the string 12 for the purpose of opening a previously unopened N valve 14 that was previously placed in the ball-trapping state. In response to the fluid pressure applied to the resulting restricted central passage, the valve 14 N opens to allow a fracturing operation to be performed on the associated layer 15 N. Opening of the valve 14 N in turn sets the next valve 14 N-1 in the ball-trapping state in sequence. When the fracturing operation is completed on layer 15 N another ball is dropped into the central passage of string 12 to open valve 14 N-1 so that layer 15 N-1 can be fracture. This sequence continues until the last valve 14 1 is opened and the associated layer 15 1 is cracked.In an example described in more detail, in accordance with some embodiments of the invention, Figures 2 and 3 illustrate upper and lower portions 14A, 14B of an exemplary valve 14 that is closed and has not been placed in the ball-trapping state (i.e., the valve 14 is in its initial state when running into the bore). As shown in FIGS. 2 and 3, therefore, the valve 14 does not restrict its central passage 24. As will be described further below, the valve 14 may subsequently be placed in the ball catch state, a state in which the valve 14 compresses a collet sleeve 30 to form an annular seat for catching the ball.Turning now to the more detailed details of the embodiment illustrated in FIGS. 2 and 3, the valve 14 includes a substantially cylindrical upper housing portion 20 (FIG. 2 ) coaxial with a longitudinal axis 26 of the valve 14. The upper housing portion 20 includes an opening 19 for supplying fluids (drilling fluid, fracturing fluid, etc.) to the portion of the string 12 disposed over and connected to the upper housing portion 20. At its lower end, the upper housing portion 20 is coaxially aligned and connected to a substantially cylindrical lower housing portion 22 (FIGS. 2 and 3 ). As shown in FIG. 2, in some embodiments of the invention, a seal, such as an O-ring 23, may be present between the upper and lower housing portions 20, 22.The valve 14 includes a valve sleeve 60 (FIG. 2 ) disposed coaxial with the longitudinal axis 26 and configured to move within an annular pocket 80 (see FIG. 3 ) formed in the upper and lower housing portions 20, 22 of the valve 14. The central passage of the valve sleeve 60 forms part of the central passage 24 of the valve 14. upper and lower O-rings 62, 64 encircle the outer surface of the sleeve 60 and form corresponding annular seals between the outer surface of the sleeve 60 and the inner surface of the housing portion 20 for purposes of sealing radial openings (not shown in FIG. 2 ) in the upper housing portion 20 during the closed state (shown in FIGS. 2 and 3 ) of the valve 14, when the sleeve 60 is moved in a downward direction to open the valve 14.At its lower end, the valve sleeve 60 is connected to the upper end of the collar sleeve 30, the sleeve radial expansion / contraction state controlling when the valve 14 is in the ball-trapping state. The collar 30 is substantially coaxial with the longitudinal axis 26. In some embodiments of the invention, the collar 30 includes a lower end 32 in which longitudinal slots 34 are formed which are uniformly spaced about the longitudinal axis 26 of the collar 30.In its expanded state (shown in FIG. 2 ), the lower end 32 of the collar sleeve 30 is expanded radially outwards to provide the maximum diameter through the interior of the collar sleeve 30. As shown in Figure 2, in this condition of the collar sleeve 30, an opening 38 in the lower end 32 of the sleeve 30 has its maximum inner diameter, leaving the central passage 24 free.For purposes of radially contracting the lower end 32 of the collar sleeve 30 to place the valve 14 in its ball-trapping state, the valve 14 includes a stem (mandrel) 40. the sleeve 40 is configured to translate in a downward longitudinal direction (from the position shown in FIG. 2 ) to slide a sleeve 48 over the lower end 32 to radially contract the lower end 32. The spindle 40 is shown in FIG. 2 in a position that allows complete radial expansion of the lower end 32 of the collar sleeve 30, such that in this position the spindle 40 does not configure the collar sleeve 30 to capture a ball.For the purpose of actuating the spindle 40 to move the spindle 40 in a downward direction, the spindle 40 includes a piston head 43 having an upper surface 44. The upper surface 44 is in turn in communication with a fluid passage 42 formed, for example, in the upper housing portion 20. The upper surface 44 of the piston head 43 is exposed to an upper chamber 90 (which is at its minimum volume in Figure 2) of the valve 14 to provide a downward force on the spindle 40 to narrow the lower end 32 of the collar 30.As shown in FIG. 2, an O-ring 47 forms a seal between the inner surface of the piston head 43 and the outer surface of the collar sleeve 30; and a lower O-ring 72 is disposed on the outside of the spindle 40 to form a seal between the outer surface of the spindle 40 and the inner surface of the upper housing portion 20. Due to these seals, the upper chamber 90 is sealed by a lower chamber 75 located below a lower surface 73 of the piston head 43. By way of example, in some embodiments of the invention, the lower chamber 75 comprises a gas, such as air at atmospheric pressure or other lower pressure, or a volume.The lower end of the spindle 40 is connected to the sleeve 48 which has an inner diameter which approximately matches the outer diameter of the portion of the collar sleeve 30 which is located above the outwardly flared lower end 32. When the pressure applied to the upper surface 47 of the piston head 43 generates a force exceeding the combined upward force exerted from the chamber 75 on the lower surface 73 and the reaction force caused due to the constriction of the lower end 32, the sleeve 48 reduces the inner diameter of the lower end 32 of the collar sleeve 30 to place the valve 14 in its ball-trapping state.Figure 4 shows the upper portion 14A of the valve 14 when the valve 14 is in the ball-trapping state, in which state the spindle 40 is at its lowest point of movement. In this state, the valve sleeve 60 remains at its highest point of movement to keep the valve 14 closed. As shown, the outer diameter of the lower end 32 of the collar sleeve 40 is constricted by the inner diameter of the sleeve 48, and an inner annular seat 94 is formed within the collar sleeve 30. The seat 94 in turn provides a narrowed inner diameter for capturing a ball.The trapping of the ball in the seat 94 substantially, if not sealing, narrows the center passage of the valve 14 above the ball from the center passage of the valve 14 below the ball. Due to the restriction of the flow, pressure may be applied from the surface of the bore to exert a downward force on the collar 30. Because the lower end of collar sleeve 30 is connected to the lower end of valve sleeve 60, a corresponding downward force is generated on valve sleeve 60 when pressure is applied to the locking ball and collar sleeve 30. The sleeve 60 may be initially retained in the upper position shown in FIGS. 2 and 4 by one / more mechanisms (not shown in the figures), such as one or more latches, one or more shear pins, vacuum trapped, or one or more vacuum chambers. However, when sufficient downward force is applied to the valve sleeve 60, this restraining mechanism releases the downward movement of the valve sleeve 60.Thus, to open the valve 14, a ball is dropped from the surface into the bore and then sufficient pressure is applied (aided by the constraint imposed by the ball resting thereon) to cause the valve sleeve 60 to move from its uppermost position to its lowermost position illustrated in Figures 5 and 6. Specifically, Figs. 5 and 6 show the valve 14 in its open state. As shown in FIG. 5, in the open state, one or more radial passages 100 formed in the upper housing portion 20 are exposed to the central passage 24 of the valve 14. Therefore, in the open state, fluid, such as fracturing fluid, may be directed from the center passage 24 of the string (see FIG. 1 ) to the annular region surrounding the valve 14. It should be noted that when the valve 14 is closed, the radial ports 100 are sealed between the upper and lower O-rings 62, 64.Referring to Figure 6, the assembly formed of valve sleeve 60, collar sleeve 30, spindle 40 and sleeve 48 moves downwardly due to the pressure applied to valve sleeve 60 until the lower surface of collar sleeve 30 and the lower surface of sleeve 48 abut an annular shoulder formed at the bottom of annular pocket 80. Figure 6 therefore shows a ball or ball 150 resting on the seat 94 and causing the valve 14 to pass to its open state.Referring to FIG. 5, in the open state of the valve 14, the passage 70 is in fluid communication with the central passage 24, which is in contrast to the closed state of the valve 14 in which the O-ring 68 forms a seal between the central passage 24 and the passage 70, as shown in FIGS. 2 and 4. Thus, in the open state of the valve 14, fluid pressure may be directed to the passage 70 (see FIG. 5 ) to place another valve 14 of the string 12 (see FIG. 1 ) in its ball-trapping state.As a more detailed example, in some embodiments of the invention, passage 70 may be in fluid communication with passage 42 of another valve 14 (e.g., the immediately adjacent upper valve 14). Thus, in response to the valve sleeve 60 being moved to its lower position, a downward force (by the application of pressure through the passages 70 and 42) is applied to the spool 40 of the other valve 14 of the string 12. As another more specified example, in some embodiments of the invention, the passage 70 of each valve 14 may be in fluid communication with the passage 42 of the immediately upper adjacent valve in the string 12. Thus, for example, referring to FIG. 1, passage 70 of valve 14 3 is connected to passage 42 of valve 14 2 and passage 70 of valve 14 2 is connected to passage 42 of valve 14 1. It should be noted that the valve 14 1 is the uppermost valve 14 of the branch 12 in the embodiment shown in FIG. 1. Thus, in some embodiments of the invention, the passage 70 of the valve 14 may be 1 sealed or absent.For the lowermost valve 14 N the passage 42 is not connected to the passage of a lower valve. Thus, in some embodiments of the invention, the lowermost valve 14 N is placed in its ball-trapping state by a mechanism different from those described above. For example, in some embodiments of the invention, the valve 14 N may be placed in its ball-trapping state in response to a fluid excitation conducted downhole through the central passage of the string 12. The lowermost valve 14 N may therefore include a mechanism, such as a rupture plate, that responds to remote actuation excitation to allow a downward force to be applied to the spindle 40.As another example, in some embodiments of the invention, the actuator described above may move the sleeve 40 in a downward direction in response to an underground excitation communicated by a mud line or wireline running underground through the central passage of the string 12. As another example, the excitation may be encoded in an acoustic wave communicated by the strand 12.As another example of a technique for placing the valve 14 N in its ball-trapping state, in some embodiments of the invention, the spindle 40 may have on its inner surface a profile for engaging a switching tool that is lowered downhole through the central passage of the string 12 to move the spindle 40 in a downward direction to place the valve 14 N in its ball-trapping state. In another example of another variation, in some embodiments of the invention, the valve 14 N may run downhole with a collar sleeve (replacing the collar sleeve 30) already configured to have a ball-trapping seat. Many variations are therefore possible.Because the valve 14 N is the last valve of the branch 12, other requirements for operating the valve 14 N may occur. For example, below the lowermost layer 15 N there is likely to be a closed chamber in the bore. If a ball was dropped onto the seat 94 (see FIG. 14, for example), the valve sleeve 60 of the valve 14 N cannot slide downward, as any downward movement would increase the pressure below the ball. Thus, in some embodiments of the invention, the string 12 includes an atmospheric chamber 17 (see FIG. 1 ) disposed below the valve 14 in N fashion. For example, chamber 17 may be formed in a side pocket in a wall of strand 12. To initiate operation of the valve 14 in N a perforating gun may be lowered underground through the central passage of the string 12 to the position where the atmospheric chamber 17 is located. At least one perforation formed by the firing of the perforating gun may then pass through the atmospheric chamber 17 to generate the lower pressure required to push the valve sleeve 60 in a downward direction to open the valve 14 in N fashion.In some embodiments of the invention, a pressure signal is directed upward as the atmospheric chamber 17 is penetrated, and the pressure signal may be used to signal the valve 14 N to move the operating spindle 40 in a downward direction to place the valve 14 N in the ball-trapping state. In some embodiments of the invention, the valve 14 N may include a pressure sensor that detects the pressure signal such that an actuator of the valve 14 N in response to the pressure signal moves the spindle 40 in the downward direction to narrow the lower end 32 of the collar 30.Alternatively, in some embodiments of the invention, the collar sleeve 30 of the valve 14 may be preconfigured in N such that the seat 94 is already in its limited position when the string 12 is retracted into the bore. A perforating gun may then be lowered through the central passage of the string 12 to pierce the atmospheric chamber 17 to allow future downward movement of the sleeve valve 60 as described above.Referring to FIG. 7, in some embodiments of the invention, a method or technique 200 may be used to fracture multiple layers of a subterranean well. The method 200 is used in conjunction with a string that includes valves similar to the valves described above, such as the string 12 that includes the valves 14 (see FIG. 1 ).According to method 200, the bottom most valve of the string is placed in its ball-trapping state, as illustrated in block 202. Next, the method 200 begins an iteration in which the valves are opened according to a sequence (e.g., a bottom-up sequence). In each iteration, the method 200 includes dropping the next sphere into the string 12 as illustrated in block 204. Next, pressure is applied to the ball (block 206) to open the valve and place another valve (if another valve is to be opened) in the ball-trapping state. Subsequently, the method 200 includes performing (block 208) a fracture in the layer associated with the opened valve. If another layer is to be cracked (diamond 210), then the method 200 includes returning to block 204 to perform another iteration.In some embodiments of the invention, the lowermost valve 14 N( see FIG. 1 ) may be opened by a rupture plate and an atmospheric chamber. More specifically, the strand 12 is pressurized, the rupture plate breaks, and then forces fluid onto one side of a piston. The other side of this bulb is in contact with an atmospheric chamber or a vacuum chamber.Unlike the conventional strings using ball trap valves, in some embodiments of the invention, the valves 14 are not closed after opening. Further, in some embodiments of the invention, each valve 14 remains in its ball-trapping state when placed in this state. Because the valves 14 are configured to trap a ball of the same size, the cross-sectional flow area through the central passage of the string is not significantly more difficult for subsequent fracture or production operations.It is noted that for any valve 14 in the string 12, the constricted diameter formed by the lower end of the collar 30 prevents a ball from flowing upward when the valve 14 is placed in its ball-trapping state. Therefore, during backflow, each ball must be prevented from flowing upward toward the lower end 32 of the collar sleeve 30 of the valve 14.However, in accordance with some embodiments of the invention, each ball may be formed of a material that is, for example, decomposable or breakable. This allows the ball to be decomposed. Although a particular ball may flow upwardly during reflow and contact the lower end of collar 30 thereover, the ball is eventually eroded or at least sufficiently dissolved to flow upwardly through the valve to open a connection through string 12.In some embodiments of the invention, trapped balls used to activate a lower valve 14 may push the collar sleeve 30 of a higher valve up in the string 12 until the collar sleeve 30 moves in an area (e.g., a stepped area formed in the lower housing 22) that has a pocket in the inner diameter to allow the collar sleeve 30 to re-open. Then, when the collar sleeve 30 re-opens, the inner diameter is no longer small enough to narrow the ball so that the ball can flow upward. Other variants are possible.Referring to FIG. 8, a bottom surface 252 of the bottom end 32 of the collar sleeve 30 is irregularly shaped in accordance with some embodiments of the invention to prevent a ball disposed below the collar sleeve 30 (and not dissolved or eroded enough to fit therethrough) from forming a seal that blocks fluid communication. Therefore, in some embodiments of the invention, surface 251 may have one or more irregularities, such as notch or depression 252, that prevent surface 32 from becoming an effective valve seat. Other types of irregularities may be provided on the surface 251, such as raised portions, substantially rough surfaces, etc., depending on the particular embodiment of the invention.For example, referring to FIG. 9, in some embodiments of the invention, in a valve 290 (which replaces the valve 14), the collar sleeve 30 may be replaced with a C-ring 300. The valve 290 has substantially the same structure as the valve 14 except for the C-ring 300 and the following differences. The C-ring 300 includes a single open slot 309 in some embodiments of the invention when the valve 290 is not in the ball-trapping state. In this state, as shown in FIG. 9, a sleeve, a shaft 302 is disposed above the C ring 300 so that the open ends 307 of the C ring 300 are not narrowed to close the slit 309. As shown in FIG. 9, in some embodiments of the invention, an end 304 of the spindle 302 may be tapered or sloped such that when the spindle 302 translates downward as shown in FIG. 10, the ends 307 meet to close the slot 309 (FIG. 9 ) and thus restrict the inner diameter by the C-ring 300. In the state shown in FIG. 10, the valve 290 is in a ball trapping state because the inner diameter has been reduced to trap a free-falling or downwardly pumped object.The configuration of the C-ring may be advantageous in some embodiments of the invention such that the C-ring 300 includes a single slot 309 compared to the multiple slots 34 (see, e.g., FIG. 2 ) present in the collar sleeve 30. Therefore, the C-ring configuration may be advantageous in that the seal is simpler because less leakage occurs when the C-ring 300 contracts.Referring to FIG. 1, in some embodiments of the invention, the string may be inserted into a wellbore (e.g., an open or unpiped hole) for temporary completion. In such embodiments, the sealing mechanisms between each valve and within the annulus defined by the tubular string and the wellbore may be actuated to isolate the formation zones to be treated with a treatment fluid. However, in other embodiments of the invention, the strand 12 may be cemented in place as a permanent completion. In such embodiments, the cement serves to isolate each formation zone.Cementing the string 12 may potentially block valve ports if the valve 14 is not specially configured. For example, with reference to FIG. 5, in some embodiments of the invention, the valve 14 may include protrusions 101 spaced about the longitudinal axis 26. Each ridge 101 extends radially outward from a cylindrical main wall 103 of the upper housing 20, and each radial passage 100 extends through one of the ridges 101. The ridges 101 reduce the space otherwise present between the valve 14 and the wellbore to limit the amount of cement that can potentially block fluid communication between the central passage 24 and the area outside the valve 14, as described in U.S. application Ser. No. 10 / 905,073, issued to 2004.According to some embodiments of the invention, each radial passage 100 is formed by an elongated slot having a length approximately equal to five times its width. Such a slot geometry has been found to allow radial deflection upon pressurization when used in a fracturing process, which increases stress in the rock and thus reduces fracture initiation pressure.Depending on the particular embodiment of the invention, the valve may include, for example, three (e.g., spaced 120° about the longitudinal axis 26) or six (e.g., spaced 60° about the longitudinal axis 26) ridges 101. In some embodiments of the invention, the valve 14 does not include any lands 101. Instead, the upper housing portion 20 approximates a circular cylinder whose outer diameter size is adapted to closely fit the inner diameter of the wellbore.Other variations are possible. For example, depending on the particular embodiment of the invention, each radial passage 100 may have a length that is at least about ten times or (in other embodiments) about twenty times its length.The radial slots 100 are shown in FIG. 5 as being disposed at substantially the same longitudinal position. However, in other embodiments of the invention, a valve (FIG. 11 ) may include a valve housing 400 (replacing the upper valve housing 20) that includes radial slots 420 that extend along a helical or helical path 422 about the longitudinal axis 26. As shown in FIG. 11, the valve housing 400 does not include radially extending ridges. Therefore, various variations are possible.Although terms indicating directions and orientations (e.g., "upward", "lower", etc.) have been used to describe the string, valve, components, and operation thereof, it will be appreciated that the exact orientations and directions used are not needed to practice the invention. For example, in some embodiments of the invention, the valve sleeve may be moved upwardly to open. As another example, in some embodiments of the invention, the string may be disposed in a lateral borehole.

Claims

An apparatus for use in a bore having a tubular member having a passageway, characterised in that a first tool is attached to the tubular member, the first tool is configured to be placed in a state to catch a first object supplied through the passageway and to perform an operation after catching the first object, and a second tool is attached to the tubular member and configured to transition to a state to catch a second object directed through the passageway in response to the operation.Device according to claim 1, characterised in that the first and second objects comprise spheres of the same size.Device according to claim 1 or 2, characterised in that at least one of the first and second tools comprises a valve (14).The apparatus of any of claims 1 to 3, characterized in that the first tool comprises a valve comprising a sleeve operable to open and close the valve (14), the sleeve opening to perform the operation and the opening of the sleeve providing a fluid communication path that causes the second tool to transition to the state for capturing the second object.The device according to any one of claims 1 to 4, characterized in that the first tool comprises a sleeve configured to form a seat for catching the first object, for placing the first tool in the state.Device according to any one of claims 1 to 5, characterised in that the second tool comprises a sleeve adapted to form a seat for catching the first object, in order to put the second tool in the state.The apparatus of any one of claims 1 to 6, characterized in that the second tool comprises a surface for contacting by the first object after the second tool transitions to the state for capturing the second object, the surface configured to prevent formation of a seal between the first object and the surface.A method for use in a well, in which a first object is dropped into a passage of a string (12), the first object being captured downhole in a first tool, characterised in that after the capturing pressure is applied in the passage to cause the first tool to perform an operation that provides a downhole pressure change, and in response to the pressure change, a second tool is caused to transition from a first state in which the second tool is caused to pass a second object directed through the string (12) through the second tool to a second state in which the second tool is caused to capture the second object.Method according to claim 8, characterized in that the first and the second object comprise spheres of the same size.Method according to claim 8 or 9, characterized in that at least one of the first and second tools comprises a valve (14).Method according to one of Claims 8 to 10, characterized in that the first tool comprises a valve and, furthermore, the valve (14) is opened in order to create the pressure change.Method according to claim 10, characterised in that the act of responding comprises narrowing a sleeve of the second valve (14) to form a seat for catching the second object.Method according to any of claims 8 to 12, characterized in that a flow of the first object is performed upstream to cause the second tool to transition from the second state to the first state.The method of claim 13, characterized in that the flow comprises using the first object to contact a radially contracting mechanism of the second tool to urge the mechanism into an annular region in which the mechanism radially expands.

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