Technique and apparatus for completing multiple zones

An apparatus that is usable with a well includes a string and a plurality of tools that are mounted in the string. The string includes a passageway. The tools are mounted in the string and are adapted to be placed in a state to catch objects (free-falling objects and/or pumped-down objects, as just a few examples) of substantially the same size, which are communicated downhole through the passageway.

BACKGROUND

The present invention generally relates to a technique and apparatus to complete multiple zones.

For purposes of enhancing production from a subterranean well, the layers of the well may be fractured using a pressurized proppant-containing fracturing fluid or other treating fluids such as acid. The layers typically are fractured one at time by directing fracturing fluid to the layer being fractured and isolating the other layers.

A conventional fracturing system includes surface pumps that pressurize fracturing fluid, which may be communicated downhole via the central passageway of a tubular string. The string extends downhole through a wellbore that traverses the various layers to be fractured; and the string may include valves (sleeve valves, for example) that are generally aligned with the layers so that the valves may be used to control fluid communication between the central passageway of the string and the layers. Thus, when a fracturing operation is performed on one of the layers, one of the valves is opened so that fracturing fluid may be communicated through the opened valve to the associated layer.

To remotely operate the valves from the surface of the well, the valves may contain many different size ball seats. More specifically, to target and actuate the valves, differently sized balls may be dropped into the central passageway of the string from the surface of the well. Each ball size may be uniquely associated with a different valve, so that a particular ball size is used to actuate a specific valve. The smallest ball opens the deepest valve. More particularly, a free-falling ball lodges, or is “caught” by, a ball seat of the targeted valve. To discriminate between the different valves, each ball seat of the string has a different diameter.

After a ball lodges in a ball seat, fluid flow through the central passageway of the string becomes restricted, a condition that allows fluid pressure to be applied from the surface of the well for purposes of exerting a downward force on the ball. The ball seat typically is attached to a sleeve of the valve to transfer the force to the sleeve to cause the valve to open.

The annular area that is consumed 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 passageway of the string, as the flow through each ball seat becomes progressively more narrow as the number of ball seats increase. Thus, a large number of valves may significantly restrict the cross-sectional flow area through the string.

As an alternative to the ball seat being located in the string as part of the valves, a single activation tool may be selectively positioned in side the central passageway of the string to operate the valves. More specifically, a valve actuation tool may be lowered downhole by a conveyance mechanism (a slickline, for example) to the valve to be opened and to close previously-opened valves.

A challenge with this alternative is that the fracturing pumps at the surface of the well may need to be idled after each layer is fractured. Furthermore, each valve typically is closed after its associated fracturing operation. The reclosure of the valves demands that the seals and sealing surfaces withstand the fracturing operations without damage.

Thus, there is a continuing need for a technique and/or arrangement to address one or more of the problems that are set forth above as well as possibly address one or more problems that are not set forth above.

SUMMARY

In an embodiment of the invention, an apparatus that is usable with a well includes a string and a plurality of tools that are mounted in the string. The string includes a passageway. The tools are mounted in the string and are adapted to be placed in a state to catch objects (free-falling objects and/or pumped-down objects, as just a few examples) of substantially the same size, which are communicated downhole through the passageway.

In another embodiment of the invention, an apparatus that is usable with a well includes a tubular member, a first tool and a second tool. The tubular member includes a passageway. The first tool is attached to the tubular member, and the first tool is adapted to be placed in a state to catch a first object that is communicated through the passageway and perform an operation after catching the first object. The second tool is attached to the tubular member and is adapted to transition to a state to catch a second object communicated through the passageway in response to the operation.

In yet another embodiment of the invention, a technique that is usable with a well includes providing a string that has a plurality of tools and a passageway that extends through the tools. The technique includes without running an activation tool into the passageway; and selectively activating the tools of the string to cause each activated tool to transition from a first state in which the activated tool is configured to allow a free-falling object to pass through the passageway to a second state in which the activated tool is configured to catch the free-falling object.

Advantages and other features of the invention will become apparent from the following description, drawing and claims.

DETAILED DESCRIPTION

Referring toFIG. 1, an embodiment10of a fracturing system includes a string12that extends into a wellbore11that traverses N layers15(layers151,152,153. . .15N−1and15N, depicted as examples) of the well. As depicted inFIG. 1, the string12includes valves14(valves141,142,143. . .14N−1and14N, depicted as examples), each of which is associated with a particular layer15. For example, the valve143is associated with the layer153. Thus, to fracture a particular layer15, the associated valve14(initially run downhole in a closed state) is opened by dropping a ball and pumping up, which shifts the sleeve valve open (as described below) to allow communication between the central passageway of the string12and the associated layer15. This communication, in turn, permits fracturing fluid and pressure to be routed to the associated layer15.

More specifically, in some embodiments of the invention, each valve14controls communication between a central passageway of the string12and an annular region that surrounds the valve14. When the string12is run downhole, all of the valves14are initially closed. However, the valves14are successively opened one at a time in a predetermined sequence (described below) for purposes of fracturing the layers15.

As a more specific example, in some embodiments of the invention, the valves are opened in a sequence that begins at the bottom of the string12with the lowest valve14N, proceeds uphole to the next immediately adjacent valve14, then to the next immediately adjacent valve14, etc. Thus, the valve14Nis opened before the valve14N−1, the valve143, is opened before the valve142, etc.

For purposes of opening a particular valve14, a free-falling or pumped-down object is deployed from the surface of the well into the central passageway of the string12. It is assumed below for purposes of clarifying the following discussion that the object is a spherical ball. However, it is understood that in other embodiments of the invention, other object types and/or differently-shaped objects may be used.

In some embodiments of the invention, a ball of the same dimension may be used (although different size balls may be used in other embodiments of the invention) to open all of the valves14, as only one of the previously-unopened valves (called the “targeted valve” herein) is in a “ball catching state” at any one time. More specifically, in accordance with some embodiments of the invention, all of the balls that are pumped or dropped downhole for purposes of opening one of the valves14may have diameters that vary less than approximately 0.125 inches from each other.

As described below, initially, all of the valves14are closed, and none of the valves14are in ball catching states. When a particular valve14opens, the valve14places the next valve14in the sequence in the ball catching state. When in the ball catching state, the valve14forms a seat that presents a restricted cross-sectional flow passageway to catch a ball that is dropped into the central passageway of the string12. For the sequence that is described above, the unopened valves14that are located above the unopened valve14that is in the ball catching state allow the ball to pass through.

After the ball lodges in the ball catcher of the targeted valve14, the ball significantly restricts, if not seals off, the central passageway of the string12below the ball so that fluid pressure may be applied above the ball to generate a force to cause the valve to open, as further described below.

As a more specific example, a ball may be dropped from the well's surface into the central passageway of the string12for purposes of opening a previously-unopened valve14Nthat has previously been placed in a ball catching state. In response to the fluid pressure that is applied to the resultant restricted central passageway, the valve14Nopens to allow a fracturing operation to be performed on the associated layer15N. The opening of the valve14N, in turn, places the next valve14N−1in the sequence in the ball catching state. Once the fracturing operation on the layer15Nis complete, another ball is dropped into the central passageway of the string12for purposes of opening the valve14N−1so that the layer15N−1can be fractured. Thus, this sequence continues until the last valve141is opened, and the associated layer151is fractured.

As a more specific example, in accordance with some embodiments of the invention,FIGS. 2 and 3depict upper14A and lower14B sections of an exemplary valve14that is closed and has not been placed in ball catching state (i.e., the valve14is in its initial states when run into the well). Thus, as depicted inFIGS. 2 and 3, the valve14does not restrict its central passageway24. As further described below, the valve14may be subsequently placed in the ball catching state, a state in which the valve14compresses a collet sleeve30to form an annular seat to catch the ball.

Turning now to the specific details of the embodiment that is depicted inFIGS. 2 and 3, in some embodiments of the invention, the valve14includes a generally cylindrical upper housing section20(FIG. 2) that is coaxial with a longitudinal axis26of the valve14. The upper housing section20includes an opening19to communicate fluids (well fluid, fracturing fluid, etc.) with the portion of the string12that is located above and is attached to the upper housing section20. At its lower end, the upper housing section20is coaxial with and is connected to a generally cylindrical lower housing section22(FIGS. 2 and 3). As depicted inFIG. 2, in some embodiments of the invention, a seal such as an O-ring23may be present between the upper20and lower22housing sections.

The valve14includes a valve sleeve60(FIG. 2) that is coaxial with the longitudinal axis26and is constructed to move longitudinally within an annular pocket80(seeFIG. 3) that is formed in the upper20and lower22housing sections of the valve14. The central passageway of the valve sleeve60forms part of the central passageway24of the valve14. Upper62and lower64O-rings circumscribe the outer surface of the sleeve60and form corresponding annular seals between the outer surface of the sleeve60and the inner surface of the housing section20for purposes of sealing off radial openings (not shown inFIG. 2) in the upper housing section20during the closed state (depicted inFIGS. 2 and 3) of the valve14. As further described below, when the sleeve60moves in a downward direction to open the valve14, openings in the upper housing section20are exposed to place the valve14in an open state, a state in which fluid communication occurs between the central passageway24of the valve14and the region that surrounds the valve14.

At its lower end, the valve sleeve60is connected to the upper end of the collet sleeve30, a sleeve whose state of radial expansion/contraction controls when the valve14is in the ball catching state. The collet sleeve30is generally coaxial with the longitudinal axis26. In some embodiments of the invention, the collet sleeve30includes a lower end32in which longitudinal slots34are formed, and these slots34may be regularly spaced about the longitudinal axis26of the collect sleeve30.

In its expanded state (depicted inFIG. 2), the lower end32of the collet sleeve30is flared radially outwardly for purposes of creating the maximum diameter through the interior of the collet sleeve30. Thus, as depicted inFIG. 2, in this state of the collet sleeve30, an opening38in the lower end32of the sleeve30has its maximum inner diameter, thereby leaving the central passageway24unobstructed.

For purposes of radially compressing the lower end32of the collet sleeve30to place the valve14in its ball catching state, the valve14includes a mandrel40. The mandrel40is designed to slide in a downward longitudinal direction (from the position depicted inFIG. 2) for purposes of sliding a sleeve48over the lower end32to radially compress the lower end32. The mandrel40is depicted inFIG. 2in a position to allow full radial expansion of the lower end32of the collet sleeve30, and thus, in this position, the mandrel40does not configure the collet sleeve30to catch a ball.

For purposes of actuating the mandrel40to move the mandrel40in a downward direction, the mandrel40includes a piston head43that has an upper surface44. The upper surface44, in turn, is in communication with a fluid passageway42that may be formed in, for example, the upper housing section20. The upper surface44of the piston head43is exposed to an upper chamber90(having its minimum volume inFIG. 2) of the valve14for the purpose of creating a downward force on the mandrel40to compress the lower end32of the collet sleeve30.

As depicted inFIG. 2, an O-ring47forms a seal between the inner surface of the piston head43and the outer surface of the collet sleeve30; and a lower O-ring72is located on the outside of the mandrel40for purposes of forming a seal between the exterior surface of the mandrel40and the interior surface of the upper housing section20. Due to these seals, the upper chamber90is sealed off from a lower chamber75, a chamber that is below a lower surface73of the piston head43. As an example, in some embodiments of the invention, the lower chamber75has gas such as air at atmospheric pressure or other low pressure or at a vacuum.

The lower end of the mandrel40is connected to the sleeve48that has an inner diameter that is sized to approximately match the outer diameter of the section of the collet sleeve30located above the flared lower end32. Thus, when the pressure that is exerted on the upper surface47of the piston head43creates a force that exceeds the combined upward force exerted from the chamber75to the lower surface73and the reaction force that is exerted due to the compression of the lower end32, the sleeve48restricts the inner diameter of the lower end32of the collet sleeve30to place the valve14in its ball catching state.

FIG. 4depicts the upper section14A of the valve14when the valve14is in the ball catching state, a state in which the mandrel40is at its lowest point of travel. In this state, the valve sleeve60remains in its uppermost point of travel to keep the valve14closed. As shown, in this position, the outer diameter of the lower end32of the collet sleeve40is confined by the inner diameter of the sleeve48, and an interior annular seat94is formed inside the collet sleeve30. The seat94, in turn, presents a restricted inner diameter for catching a ball.

The capture of the ball on the seat94substantially restricts, if not seals off, the central passageway of the valve14above the ball from the central passageway of the valve14below the ball. Due to this restriction of flow, pressure may be applied from the surface of the well for purposes of exerting a downward force on the collet sleeve30. Because the upper end of the collet sleeve30is connected to the lower end of the valve sleeve60, when pressure is applied to the lodged ball and collet sleeve30, a corresponding downward force is generated on the valve sleeve60. The sleeve60may be initially retained in the upward position that is depicted inFIGS. 2 and 4by such mechanism(s) (not depicted in the figures) as one or more detent(s), one or more shear pins, trapped low pressure, or vacuum chamber(s). However, when a sufficient downward force is applied to the valve sleeve60, this retention mechanism gives way to permit downward movement of the valve sleeve60.

Thus, to open the valve14, a ball is dropped from the surface of the well, and then a sufficient pressure is applied (aided by the restriction presented by the lodged ball) to cause the valve sleeve60to shift from its uppermost position to its lowest position, a position that is depicted inFIGS. 5 and 6. More particularly,FIGS. 5 and 6depict the valve14in its open state. As shown inFIG. 5, in the open state, one or more radial ports100formed in the upper housing section20are exposed to the central passageway24of the valve14. Thus, in the open state, fluid, such as fracturing fluid (for example), may be communicated from the central passageway24of the string (seeFIG. 1) to the annular region that surrounds the valve14. It is noted that when the valve14is closed, the radial openings100are sealed off between the upper62and lower64O-rings.

Referring toFIG. 6, due to the pressure that is exerted on the valve sleeve60, the assembly that is formed from the valve sleeve60, collet sleeve30, mandrel40and sleeve48travels downwardly until the bottom surface of the collet sleeve30and the bottom surface of the sleeve48reside on an annular shoulder that is formed at the bottom of the annular pocket80.FIG. 6also depicts a sphere, or ball150, that rests on the seat94and has caused the valve14to transition to its open state.

Referring back toFIG. 5, in the open state of the valve14, the passageway70is in fluid communication with the central passageway24. This is in contrast to the closed state of the valve in which the O-ring68forms a seal between the central passageway24and the passageway70, as depicted inFIGS. 2 and 4. Therefore, in the valve's open state, fluid pressure may be communicated to the passageway70(seeFIG. 5) for purposes of transitioning another valve14of the string12(seeFIG. 1) to its ball catching state.

As a more specific example, in some embodiments of the invention, the passageway70may be in fluid communication with the passageway42of another valve14(the immediately adjacent valve14above, for example). Therefore, in response to the valve sleeve60moving to its lower position, a downward force is applied (through the communication of pressure through the passageways70and42) to the mandrel40of another valve14of the string12. As a more specific example, in some embodiments of the invention, the passageway70of each valve14may be in fluid communication with the passageway42of the immediate upper adjacent valve in the string12. Thus, referring toFIG. 1, for example, the passageway70of the valve143is connected to the passageway42of the valve142, and the passageway70of the valve142is connected to the passageway42of the valve141. It is noted that the valve141in the exemplary embodiment that is depicted inFIG. 1, is the uppermost valve14in the string12. Thus, in some embodiments of the invention, the passageway70of the valve141may be sealed off or non-existent.

For the lowermost valve14N, the passageway42is not connected to the passageway of a lower valve. Thus, in some embodiments of the invention, the lowermost valve14Nis placed in its ball catching state using a mechanism that is different from that described above. For example, in some embodiments of the invention, the valve14Nmay be placed in its ball catching state in response to a fluid stimulus that is communicated downhole through the central passageway of the string12. Thus, the lowermost valve14Nmay include a mechanism such as a rupture disc that responds to a remotely-communicated stimulus to permit a downward force to be applied to the mandrel40.

As another example, in some embodiments of the invention, the above-described actuator may move the mandrel40in a downward direction in response to a downhole stimulus that is communicated via a slickline or a wireline that are run downhole through the central passageway of the string12. As yet another example, the stimulus may be encoded in an acoustic wave that is communicated through the string12.

As another example of a technique to place the valve14Nin its ball catching state, in some embodiments of the invention, the mandrel40may have a profile on its inner surface for purposes of engaging a shifting tool that is lowered downhole through the central passageway of the string12for purposes of moving the mandrel40in a downward direction to place the valve14Nin its ball catching state. As yet another example of yet another variation, in some embodiments of the invention, the valve14Nmay be run downhole with a collet sleeve (replacing the collet sleeve30) that is already configured to present a ball catching seat. Thus, many variations are possible and are within the scope of the claimed invention.

Because the valve14Nis the last the valve in the string12, other challenges may arise in operating the valve14N. For example, below the lowest layer15N, there is likely to be a closed chamber in the well. If a ball were dropped on the seat94(seeFIG. 14, for example), the valve sleeve60of the valve14Nmay not shift downwardly because any movement downward may increase the pressure below the ball. Thus, in some embodiments of the invention, the string12includes an atmospheric chamber17(seeFIG. 1) that is located below the valve14N. As an example, the chamber17may be formed in a side pocket in a wall of the string12. To initiate the valve14Nfor operation, a perforating gun may be lowered downhole through the central passageway of the string12to the position where the atmospheric chamber17is located. At least one perforation formed from the firing of the perforating gun may then penetrate the atmospheric chamber17to create the lower pressure needed to shift the valve sleeve60in a downward direction to open the valve14N.

In some embodiments of the invention, when the atmospheric chamber17is penetrated, a pressure signal is communicated uphole, and this pressure signal may be used to signal the valve14Nto shift the operator mandrel40in a downward direction to place the valve14Nin the ball catching state. More specifically, in some embodiments of the invention, the valve14Nmay include a pressure sensor that detects the pressure signal so that an actuator of the valve14Nmay respond to the pressure signal to move the mandrel40in the downward direction to compress the lower end32of the collet sleeve30.

Alternatively, in some embodiments of the invention, the collet sleeve30of the valve14Nmay be pre-configured so that the seat94is already in its restricted position when the string12is run into the well. A perforating gun may then be lowered through the central passageway of the string12for purposes of piercing the atmospheric chamber17to allow downward future movement of the sleeve valve60, as described above.

Referring toFIG. 7, in some embodiments of the invention, a technique200may be used for purposes of fracturing multiple layers of a subterranean well. The technique200is used in conjunction with a string that includes valves similar to the ones that are described above, such as the string12that contains the valves14(seeFIG. 1).

Pursuant to the technique200, the lowest valve of the string is placed in its ball catching state, as depicted in block202. Next, the technique200begins an iteration in which the valves are opened pursuant to a sequence (a bottom-to-top sequence, for example). In each iteration, the technique200includes dropping the next ball into the string12, as depicted in block204. Next, pressure is applied (block206) to the ball to cause the valve to open and place another valve (if another valve is to opened) in the ball catching state. Subsequently, the technique200includes performing (block208) fracturing in the layer that is associated with the opened valve. If another layer is to be fractured (diamond210), then the technique200includes returning to block204to perform another iteration.

As a more specific example, in some embodiments of the invention, the lowest valve15N(seeFIG. 1) may be open via a rupture disc and an atmospheric chamber. More specifically, the string12is pressured up, the rupture disc breaks and then fluid pushes on side of a piston. The other side of this piston is in contact with an atmospheric chamber or a vacuum chamber.

Contrary to conventional strings that use ball catching valves, the valves14are not closed once opened, in some embodiments of the invention. Furthermore, in some embodiments of the invention, each valve14remains in its ball catching state once placed in this state. Because the valves14are designed to trap a ball of the same size, the cross-sectional flow area through the central passageway of the string is not significantly impeded for subsequent fracturing or production operations.

It is noted that for an arbitrary valve14in the string12, once the valve14is placed in its ball catching state, the restricted diameter formed from the lower end of the collet sleeve30prevents a ball from below the collet sleeve30below from flowing upstream. Therefore, during flowback, each ball may be prevented from flowing past the lower end32of the collet sleeve30of the valve14above.

However, in accordance with some embodiments of the invention, each ball may be formed from a material, such as a dissolvable or frangible material, that allows the ball to disintegrate. Thus, although a particular ball may flow upstream during flowback and contact the bottom end of the collet sleeve30above, the ball is eventually eroded or at least sufficiently dissolved to flow upstream through the valve to open up communication through the string12.

In some embodiments of the invention, captured ball used to actuate a lower valve14may push up on the collet sleeve30of a higher valve in the string12until the collet sleeve30moves into an area (a recessed region formed in the lower housing22, for example) which has a pocket in the inner diameter to allow the collet sleeve30to reopen. Thus, when the collet sleeve30reopens, the inner diameter is no longer small enough to restrict the ball so that the ball can flow uphole. Other variations are possible and are within the scope of the appended claims.

Referring toFIG. 8, in accordance with some embodiments of the invention, a bottom surface251of the lower end32of the collet sleeve30is designed to be irregular to prevent a ball that is located below the collet sleeve30(and has not dissolved or eroded enough to pass through) from forming a seal that blocks off fluid communication. Thus, as depicted inFIG. 8, in some embodiments of the invention, the surface251may have one or more irregularities, such as a depression251that permits the surface32from becoming an effective valve seat. Other types of irregularities may be introduced to the surface251, such as raised portions, generally rough surfaces, etc., depending the particular embodiment of the invention.

Other embodiments are within the scope of the appended claims. For example, referring toFIG. 9, in some embodiments of the invention, in a valve290(that replaces the valve14) the collet sleeve30may be replaced by a C-ring300. The valve290has the same generally design of the valve14, except for the C-ring300and the following differences. The C-ring300, in some embodiments of the invention, includes a single open slot309when the valve is not in the ball catching state. Thus, as depicted inFIG. 9, in this state, a mandrel302is located above the C-ring300so that the open ends307of the C-ring300do not compress to close the slot309. As depicted inFIG. 9, an end304of the mandrel302may be inclined, or beveled, in some embodiments of the invention so that when the mandrel302slides downhole, as depicted inFIG. 10, the ends307meet to close the slot309(FIG. 9) and thus restrict the inner diameter through the C-ring300. In the state that is depicted inFIG. 10, the valve is in a ball catching state, as the inner diameter has been restricted for purposes of catching a free-falling or pumped down object.

The C-ring design may be advantageous, in some embodiments of the invention, in that the C-ring300includes a single slot309, as compared to the multiple slots34(seeFIG. 2, for example) that are present in the collet sleeve30. Therefore, the C-ring design may be advantageous in that sealing is easier because less leakage occurs when the C-ring ring300contracts.

Referring to back toFIG. 1, in some embodiments of the invention, the string12may be deployed in a wellbore (e.g., an open or uncased hole) as a temporary completion. In such embodiments, sealing mechanisms may be employed between each valve and within the annulus defined by the tubular string and the wellbore to isolate the formation zones being treated with a treatment fluid. However, in other embodiments of the invention, the string12may be cemented in place as a permanent completion. In such embodiments, the cement serves to isolate each formation zone.

The cementing of the string12may potentially block valve openings, if not for certain features of the valve14. For example, referring back toFIG. 5, in some embodiments of the invention, the valve14may include lobes101that are spaced around the longitudinal axis26. Each lobe101extends radially outwardly from a main cylindrical wall103of the upper housing20, and each radial port100extends through one of the lobes101. The lobes101restrict the space otherwise present between the valve14and the wellbore to limit the amount of cement that may potentially block fluid communication between the central passageway24and the region outside of the valve14, as described in co-pending U.S. patent application Ser. No. 10/905,073 entitled, “SYSTEM FOR COMPLETING MUTLIPLE WELL INTERVALS,” filed on Dec. 14, 2004.

In accordance with some embodiments of the invention, each radial port100is formed from an elongated slot whose length is approximately equal to at least five times its width. It has been discovered that such a slot geometry when used in a fracturing operating allows radial deflection when pressuring up, which increases stress in the rock and thus, reduces the fracturing initiation pressure.

Depending on the particular embodiment of the invention, the valve may contain, as examples, three (spaced apart by 120° around the longitudinal axis26, for example) or six (spaced apart by 60° around the longitudinal axis26, for example) lobes101. In some embodiments of the invention, the valve14does not contain the lobes101. Instead, the upper housing section20approximates a circular cylinder, with the outer diameter of the cylinder being sized to closely match the inner diameter of the wellbore.

Other variations are possible in accordance with the various embodiments of the invention. For example, depending on the particular embodiment of the invention, each radial port100may have a length that is at least approximately equal to ten or (in other embodiments) is approximately equal to twenty times its length.

The radial slots100are depicted inFIG. 5as being located at generally the same longitudinal position. However, in other embodiments of the invention, a valve (FIG. 11) may include a valve housing400(replacing the upper valve housing20) that includes radial slots420that extending along a helical, or spiral path422, about the longitudinal axis26. As shown inFIG. 11, the valve housing400does not contain the radially-extending lobes. Thus, many variations are possible and are within the scope of the appended claims.

Although directional and orientational terms (such as “upward,” “lower,” etc.) are used herein to describe the string, the valve, their components and their operations, it is understood that the specific orientations and directions that are described herein are not needed to practice the invention. For example, in some embodiments of the invention, the valve sleeve may move in an upward direction to open. As another example, in some embodiments of the invention, the string may be located in a lateral wellbore. Thus, many variations are possible and are within the scope of the appended claims.