Title:
SYSTEM AND METHOD FOR MULTI-ZONE WELL TREATMENT
Kind Code:
A1


Abstract:
A technique is provided for treating a plurality of well zones with a service tool during a single trip downhole. The service tool is run downhole to a selected well zone that is isolated for treatment. Following treatment of the well zone, the service tool is moved to a subsequent well zone isolated for treatment. When the lengths of the well zones to be treated are dissimilar, the active length of the service tool can be adjusted to correspond with the well zone length to optimize the well treatment operation.



Inventors:
Guignard, Thibaut (Houston, TX, US)
Whitsitt, John R. (Houston, TX, US)
Application Number:
11/748280
Publication Date:
11/20/2008
Filing Date:
05/14/2007
Assignee:
SCHLUMBERGER TECHNOLOGY CORPORATION (Sugar Land, TX, US)
Primary Class:
Other Classes:
166/387
International Classes:
E21B43/00
View Patent Images:
Related US Applications:



Primary Examiner:
GITLIN, ELIZABETH C GOTTLIEB
Attorney, Agent or Firm:
SCHLUMBERGER ROSHARON CAMPUS (Houston, TX, US)
Claims:
What is claimed is:

1. A method of treating a well, comprising: moving a service tool downhole into a well having a plurality of zones to be treated; isolating each zone prior to treatment; circulating a treatment fluid into each isolated zone; providing an entry port into the service tool to accommodate any returning treatment fluid; and changing the position of the entry port relative to the service tool to maintain the entry port proximate a bottom of each isolated zone when treating subsequent zones having differing lengths.

2. The method as recited in claim 1, wherein moving comprises running the service tool in-hole with a completion assembly.

3. The method as recited in claim 1, wherein moving comprises moving the service tool downhole in the form of a washpipe.

4. The method as recited in claim 1, wherein isolating comprises setting a plurality of isolation packers.

5. The method as recited in claim 1, wherein changing comprises selectively opening a valve of a plurality of valves positioned along the service tool.

6. The method as recited in claim 5, wherein selectively opening comprises sealing the valve in a seal bore positioned proximate an isolation packer at a downhole end of the zone subject to treatment; and subsequently opening the valve.

7. The method as recited in claim 5, wherein selectively opening comprises creating a pressure differential between the treatment fluid and the next sequential zone downhole of the valve.

8. The method as recited in claim 5, wherein selectively opening comprises using an internal pressure within the service tool to open the valve.

9. The method as recited in claim 5, wherein selectively opening comprises opening the valve with a magnetic force.

10. The method as recited in claim 5, further comprising locking the valve in an open position.

11. The method as recited in claim 1, further comprising selectively isolating a bottom of the service tool with the valve

12. A system for treating a multi-zone well, comprising: a service tool having a plurality of valves arranged along the service tool, each valve cooperating with a sealing member; a tubular member disposed around the service tool, the tubular member having a bore region sized to form a seal with each valve via the sealing member as each valve is moved into the bore region; and an isolation packer disposed externally of the tubular member proximate an exterior of the bore region, wherein any valve of the plurality of valves can be moved into sealing engagement with the bore region to ensure the effective length of the service tool corresponds with the length of a well zone to be treated.

13. The system as recited in claim 12, wherein each valve is actuated by one of a group consisting of: (i) pressure actuation, the pressure actuation requiring formation of a seal via the sealing member positioned between the valve and the bore region; (ii) magnetic actuation: and (iii) internal pressure actuation within the service tool.

14. (canceled)

15. (canceled)

16. The system as recited in claim 12, wherein the service tool has a bottom opening; and wherein at least one of the valves comprises an in-line valve that can selectively open and close the bottom opening.

17. The system as recited in claim 16, wherein the in-line valve is a one-way valve.

18. The system as recited in claim 16, wherein the in-line valve is a two-way valve.

19. The system as recited in claim 12, wherein each valve comprises a lock to lock the valve in an open position.

20. The system as recited in claim 19, wherein the lock is a hydraulic lock.

21. The system as recited in claim 12, wherein each valve is biased toward a closed position.

22. A system, comprising: a well treatment system having: a bore region; an isolation packer disposed proximate an exterior of the bore region; and a valve selectively movable to a position inside the bore region for sealing engagement with the bore region, wherein the valve may be selectively actuated to open an entry port for admitting fluid into the valve once sealed with the bore region.

23. The system as recited in claim 22, wherein the valve comprises a plurality of valves that may be selectively opened when sealed with the bore region to accommodate treatment of well zones with differing lengths, and wherein the isolation packer comprises a plurality of isolation packers located to isolate a plurality of well zones having differing lengths.

24. (canceled)

25. A method, comprising: sequentially treating a plurality of well zones with a single trip downhole; and: adjusting the active length of a service tool according to the length of each well zone treated while maintaining a fluid return path port proximate a lower region of the well zone treated.

26. The method as recited in claim 25, wherein sequentially treating comprises running the service tool in-hole with a completion assembly.

27. The method as recited in claim 25, wherein adjusting comprises positioning a plurality of valves along the service tool such that a valve located at the lower end of an isolated well zone can selectively be opened.

28. The method as recited in claim 27, wherein the valve located at the lower end of the well zone is selectively opened by creating a pressure differential between the pressure of treatment fluid in a treatment zone and the pressure in an adjacent well zone, and wherein each valve comprises a seal member positioned to seal with a seal bore located proximate a tower end of the treatment zone.

29. (canceled)

Description:

BACKGROUND

Many types of completions are used in sand control operations. Generally, a slurry or other fluid is circulated downhole to a well zone to be treated and a return fluid is circulated back up through the completion. However, installation of typical sand control completions usually involves several trips downhole. For example, the installation may require a perforating trip, a cleanup trip, and a treatment trip. If the well has multiple zones, each of these processes is repeated for each zone.

Single trip multizone systems have been designed and used. However these systems suffer from a variety of other drawbacks, including a limited capability for handling well zones of dissimilar lengths. Some of these systems also are limited by their use of concentric strings to form the fluid flow paths required for performing the well treatment operation at multiple well zones. Other systems can be limited because the fluid flow from the surrounding reservoir into a central return passage is substantially axial rather than radial. The resulting effect can be an inefficient drainage pattern having potential for premature watering.

SUMMARY

In general, the present invention provides a system and method for treating a plurality of well zones with a single trip downhole. A service tool is run downhole to a selected well zone that is isolated for treatment. Following treatment of the well zone, the service tool is moved to a subsequent well zone isolated for treatment. The active length of the service tool can be adjusted according to the length of each well zone isolated for treatment while maintaining a fluid return path in a desired location for improving the well treatment operation.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:

FIG. 1 is a front elevation view of a completion assembly and service tool deployed in a wellbore, according to an embodiment of the present invention;

FIG. 2 is an expanded, cross-sectional view of the service tool positioned downhole at a well zone, according to an embodiment of the present invention;

FIG. 3 is an illustration of a completion assembly and service tool in which the active length of the service tool has been adjusted to treat a well zone having a given length, according to an embodiment of the present invention;

FIG. 4 is an illustration of a completion assembly and service tool in which the active length of the service tool has been adjusted to treat a subsequent well zone having a different length, according to an embodiment of the present invention;

FIG. 5 is an illustration of a completion assembly and service tool in which the active length of the service tool has been adjusted to treat another subsequent well zone having a different length, according to an embodiment of the present invention;

FIG. 6 is a cross-sectional view of one of a plurality of valves utilized in the service tool to open a selected return flow path, according to an embodiment of the present invention;

FIG. 7 is a view similar to that of FIG. 6 but showing the valve in a closed position, according to an embodiment of the present invention;

FIG. 8 is a cross-sectional view of an alternate embodiment of a valve having a lock able to maintain the valve in an open position until valve closure is desired, according to another embodiment of the present invention;

FIG. 9 is a view similar to that of FIG. 8 showing the valve locked in an open position, according to an embodiment of the present invention;

FIG. 10 is a view similar to that of FIG. 8 showing the valve returned to a closed position, according to an embodiment of the present invention;

FIG. 11 is another embodiment of a valve that can be actuated by an internal pressure within the service tool, according to an alternate embodiment of the present invention;

FIG. 12 is a view similar to that of FIG. 11 but showing the valve progressing from a closed positioned to an open position, according to an embodiment of the present invention;

FIG. 13 is a view similar to that of FIG. 11 showing the valve in an open position, according to an embodiment of the present invention;

FIG. 14 is a view similar to that of FIG. 11 showing the valve returned to a closed position after breaking the seal with a surrounding seal bore, according to an embodiment of the present invention;

FIG. 15 is another embodiment of a valve that can be actuated by a magnetic force, according to an alternate embodiment of the present invention;

FIG. 16 is a view of an in-line valve in an open position to permit flow through a bottom opening of the service tool, according to an embodiment of the present invention;

FIG. 17 is a view similar to that of FIG. 16 showing the in-line valve in a closed position, according to an embodiment of the present invention;

FIG. 18 is another embodiment of an in-line valve having a ball valve rotated to an open position, according to another embodiment of the present invention; and

FIG. 19 is a view similar to that of FIG. 18 showing the in-line ball valve in a closed position, according to an embodiment of the present invention.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

The present invention generally relates to a well system that can be used for well treatment operations, such as sand control operations. The well system is designed to treat multiple well zones in a single trip downhole. Generally, the well system comprises a completion assembly and a service tool which can be moved from one well zone to another to perform a treatment operation at each well zone. Packers are used to isolate the well zones to be treated. The well system is adaptable for use in a variety of wells and with a variety of well zones. For example, the active or effective length of the service tool can be changed to accommodate well zones of dissimilar lengths while enabling a bottom-of-zone clean fluid return path.

In one embodiment, the well system utilizes a service tool in the form of a washpipe that provides multiple selected entry points into and out of the washpipe. The service tool also enables selective zone isolation via a plurality of selectively actuatable valves within the washpipe that are able to seal inside the seal bores within isolation packers deployed between well zones. In this particular example, the valves are positioned along the wash pipe such that each well zone length encountered in the well relates to a corresponding valve within the service tool. The valves may be biased to a closed position until actuated to an open position when positioned near or inside the isolation packers. The valves above and/or below the lower isolation packer defining a well zone remain closed.

Referring generally to FIG. 1, one embodiment of a well system 30 is illustrated. In this embodiment, well system 30 comprises a completion assembly 32 and a service string 34 deployed in a wellbore 36. The wellbore 36 is drilled into a subsurface formation 38 having a plurality of well zones 40 that may contain desirable production fluids, such as petroleum. In the example illustrated, wellbore 36 is lined with a casing 42. The casing 42 typically is perforated in a manner that places perforations 44 along each well zone 40. The perforations 44 enable flow of fluids into (or out of) wellbore 36 at each well zone 40.

In the embodiment illustrated, completion assembly 32 comprises a tubular member 46 having screens 48 positioned at each well zone 40 to allow fluid flow therethrough. For example, screens 48 allow the inward flow of returning treatment fluid from the annulus surrounding the completion assembly 32 into the region between tubular member 46 and service string 34 at the subject treatment zone. A packer 50, such as a GP packer, secures completion assembly 32 to wellbore casing 42. Additionally, a plurality of isolation packers 52 are positioned between completion assembly 32 and the surrounding casing 42 at selected locations to selectively isolate the well zones 40. On an interior of tubular member 46 proximate each isolation packer 52 is positioned a bore region 54, e.g. a polished bore receptacle, for selective formation of seals with service string 34, as discussed in greater detail below.

Service string 34 is deployed downhole with completion assembly 32 on an appropriate conveyance 56, such as a tubing. The service string 34 may be attached to completion assembly 32 proximate the upper packer 50. Generally, service string 34 comprises an upper section 58 coupled to a service tool 60, e.g. a washpipe, through a crossover 62. Crossover 62 comprises one or more crossover exit ports 64 that are positioned adjacent corresponding circulating ports of completion assembly 32 to enable the flow of treatment fluid into the annulus surrounding completion assembly 32. In a sand control operation, for example, a slurry may be pumped down into this annulus at a given well zone, and a return fluid or liquid portion of the slurry is returned up through service string 34. In many applications, it is desirable for this return fluid to reenter the service string 34 at a lower end of the well zone being treated.

Service tool 60 is designed so that its active or effective length can be changed to accommodate well zones of dissimilar lengths. In the embodiment illustrated, the effective length of service tool 60 can be changed while maintaining an entry port 66, for any return fluid entering service tool 60, proximate a lower end of the well zone 40 being treated. The effective length of service tool 60 can be adjusted by a service tool length altering mechanism 68. By way of example, the length altering mechanism 68 may comprise a plurality of valves 70 arranged along at least a portion of the length of service tool 60. The valves 70 can each engage the seal bore 54 to form a seal at the lower end of a well zone 40 to be treated. Each valve 70 also can be individually actuated to selectively open its entry port 66, thereby allowing flow of fluid into the service tool at a lower end of the well zone. The length of each well zone 40 to be treated dictates which of the valves 70 engages/seals with bore region 54 proximate the corresponding lower isolation packer 52. The other valves 70, whether above or below this isolation packer 52, remain biased to a closed position. The service tool 60 can be sealed at its upper end by appropriate seal members 71 positioned around crossover 62 or at the upper end of service tool 60.

Service tool 60 also may comprise an open bottom end 72. The open bottom end 72 may be plugged with a ball or other blanking device 74 during the treatment operation. As discussed in greater detail below, linear fluid flow through service tool 60 also may be selectively opened or closed by appropriate in-line valves.

In some well treatment operations, each well zone 40 is sequentially treated. A well treatment fluid is flowed downhole as indicated by arrows 76. The well treatment fluid exits the service string at crossover 62 via crossover exit ports 64. The fluid flows into the surrounding annulus between completion assembly 32 and casing 42 at the well zone being treated. The return fluid then reenters completion assembly 32 via the screen 48 positioned at that particular well zone. The return fluid reenters service string 34 at the entry port 66 which has been opened proximate the lower isolation packer 52 via actuation of the valve 70 engaged with the corresponding seal bore 54. The fluid is then returned upwardly along appropriate flow paths through service string 34.

The actual components and procedure for carrying out a given multizone well treatment operation can vary. However, one example comprises initially running a perforation assembly in-hole and perforating each of the well zones 40. Subsequently, completion assembly 32, along with service string 34, is run-in-hole. The service string 34 can be attached to completion assembly 32 at the upper packer. Once the completion assembly is placed on depth, open bottom end 72 is blocked by, for example, dropping the ball or other blanking device from the surface to make service string 34 pressure competent. Pressure is then applied into service string 34 to set the GP packer and secure completion assembly 32 to the wellbore casing 42. The isolation packers are then set by an appropriate packer setting procedure, e.g. by applying tubing pressure with the service string in a packer setting position.

Additionally, the appropriate valve 70 is placed in sealing engagement with the appropriate bore region 54, e.g. a seal bore, at a lower end of the zone to be treated. The service string 34 is placed in a circulating position in which exit port 64 is positioned adjacent the circulating port of completion assembly 32. The return or entry port 66 at the lower end of the zone to be treated is actuated to an open position to enable circulation of the treatment fluid. Upon completion of the treatment, the valve 70 is disengaged from bore region 54, and service tool 60 is moved to the next well zone to be treated.

Referring generally to FIG. 2, one embodiment of service tool length altering mechanism 68 is illustrated. In this embodiment, mechanism 68 comprises a plurality of valves 70, e.g. three valves, positioned at unique locations along the tubing or wash pipe 78 of service tool 60. The illustrated valves 70 are pressure actuated valves that are actuated to an open flow position by application of a differential pressure once a particular valve 70 engages and seals with bore region 54. The differential pressure is created between the pressure of the treatment fluid above (uphole) of the sealed valve 70 and the pressure in the next sequential, e.g. next lower, well zone. The valves 70 that are not sealed with bore region 54 do not get exposed to this differential pressure and remain biased to a closed position. Accordingly, the linearly spaced valves 70 can accommodate well zones 40 of different lengths while maintaining the fluid reentry port 66 proximate the lower isolation packer 52 at the lower end of the well zone.

The ability to accommodate multiple well zones of dissimilar lengths is illustrated in FIGS. 3-5 which show service tool 60 positioned at three different well zones of three different lengths. In FIG. 3, for example, a lower well zone 40 is initially treated. The lower well zone 40 is relatively short in length so service tool 60 is moved into the well zone 40 until the upper valve 70 forms a seal with the bore region 54 proximate the isolation packer 52 at the lower and of this well zone. The proximate seal can be located, for example, radially within the isolation packer or slightly linearly offset of the isolation packer. The valves 70 below the valve sealed against bore region 54 remain biased to the closed position. The closed valves 70 make the effective length of service tool 60 relatively short to correspond with the length of the lower well zone.

In FIG. 4, the service tool 60 has been moved to a subsequent well zone 40 above the lower well zone that was initially treated. This subsequent well zone 40 has a greater length than the first well zone treated, and service tool 60 has been moved into this subsequent well zone until the middle valve 70 forms a seal with the bore region 54 at the lower end of the zone. The valves 70 that are above and below the sealed valve remain biased to the closed position. This causes the effective length of service tool 60 to be of an intermediate length that corresponds with the length of the second or subsequent well zone being treated.

In this example, the third well zone treated is above the second well zone, as illustrated in FIG. 5. FIG. 5 illustrates service tool 60 positioned in the third zone which has a greater length than both the first and second zones treated. The service tool has been moved into this third zone until the lower valve 70 forms a seal with the bore region 54 at the lower end of this third well zone. The valves 70 that are above the sealed valve remain biased to the closed position. This causes the effective length of service tool 60 to be longer than with either of the first two zones treated. Because each valve 70 opens its own entry port 66, the fluid reentry point remains at the lower end of the well zone during treatment of any of these well zones regardless of the well zone length.

One embodiment of valve 70 is illustrated in FIGS. 6 and 7. In this embodiment, valves 70 is actuated by a pressure differential between the well treatment fluid above the valve forming a seal with seal bore 54 and the adjacent zone below the well zone being treated. In FIG. 6, the valve 70 has been shifted or actuated to an open position in which entry port 66 is open to admit flow into service tool 60. Valve 70 comprises a closure member 80, such as a sleeve, connected to a piston 82. Additionally, a seal member 84 is associated with the valve 70 and is positioned to form a seal between bore region 54 and valve 70 when valve 70 is moved into the bore region. By way of example, each seal member 84 is mounted along the exterior of a corresponding valve 70, however the seal members also can be mounted in corresponding bore regions 54. Piston 82 is biased toward a closed position by a spring 86. However, once seal member 84 seals between seal region 54 and valve 70, piston 82 also is acted on by the pressure of well treatment fluid on an uphole side and by the pressure of the next lower well zone on a downhole side. When the pressure differential between these two regions reaches a sufficient level, the bias of spring 86 is overcome and valve 70 is shifted to an open position, as illustrated in FIG. 6. When the pressure differential is sufficiently reduced or eliminated, e.g. by moving seal member 84 off bore region 54, spring 86 once again biases the valve 70 to a closed position, as illustrated in FIG. 7.

An alternate embodiment of valve 70 is illustrated in FIGS. 8-10. In this alternate embodiment, the valve 70 is again actuated by a sufficient pressure differential, but the valve includes a lock which maintains the valve in an open position until the seal member 84 is disengaged from its seal between valve 70 and the surrounding bore region 54. The valve illustrated in FIGS. 8-10 is similar in operation and has many similar components to the valve described with reference to FIGS. 6 and 7. Similar components have been labeled with the same reference numerals. In FIG. 8, valve 70 is biased to a closed position by spring 86 and flow through entry port or ports 66 is blocked by closure member 80.

When a sufficient differential pressure is created between the well treatment fluid on the treated zone side and the next adjacent well zone on an opposite side of valve 70, valve 70 is moved to an open position as illustrated in FIG. 9. Specifically, the pressure of the well treatment fluid acts against piston 82 and the bias of spring 86. Any fluid trapped by piston 82 in a sealed region 88 (see FIG. 8) is forced along the piston 82 and discharged radially outwardly through a check valve 90 to the next adjacent well zone. The check valve 90 prevents the flow of fluid back into sealed region 88 and thus holds piston 82 and closure member 80 in the open position illustrated in FIG. 9 even if the pressure differential is reduced or eliminated. Sealed region 88 also is in fluid communication with a second port 92, however second port 92 is blocked from receiving any external fluid flow while seal member 84 is sealingly engaged between valve 70 and bore region 54. In the embodiment illustrated, seal member 84 is mounted on valve 70 and second port 92 extends to a region within seal member 84. Second port 92 is blocked from receiving fluid flow while seal member 84 engages bore region 54, e.g. a seal bore.

Accordingly, valve 70 can be unlocked or released from its open position by moving valve 70 and its seal member 84 off seal bore 54, as illustrated in FIG. 10. Once seal member 84 is moved away from seat bore 54, second port 92 is open to allow fluid flow radially inward through second port 92 and into sealed region 88. Spring 86 is then able to bias piston 82 and closure member 80 to a closed position blocking flow through entry ports 66, as illustrated in FIG. 10.

Another embodiment of valve 70 is illustrated in FIGS. 11-14. In this embodiment, valve 70 is operated by internal pressure within the washpipe when the valve is located within one of the bore regions 54. As illustrated in FIG. 11, this embodiment of valve 70 comprises of valve section 94 and a primer section 96. The valve section 94 comprises a piston 98 mounted on a piston sleeve 100. Piston sleeve 100 includes a closure member 102 and a port 104. Piston 98 and piston sleeve 100 are biased toward a closed position, as illustrated in FIG. 11, by a spring 106. A secondary piston 108 is slidably mounted around piston sleeve 100 between piston 98 and primer section 96.

Primer section 96 comprises a piston member 110 biased toward a non-actuated position by a spring 112. When in the non-actuated position, piston member 110 creates a cavity 114 filled with an incompressible fluid 116, which may be well fluid. As pressure is increased within an interior 118 of the service tool 60, piston member 110 is shifted and fluid 116 is forced through a check valve 120 and ultimately into a cavity 122 surrounding piston sleeve 100 between secondary piston 108 and primer section 96. Movement of incompressible fluid 116 into cavity 122 forces secondary piston 108 to move toward piston 98, as illustrated in FIG. 12. A cavity 124 located between piston 98 and secondary piston 108 is filled with a compressible fluid 126 which is compressed as secondary piston 108 moves toward piston 98. Compressible fluid 126 acts as a spring which, when sufficiently compressed, overcomes spring 106 and moves piston 98 and piston sleeve 100 toward an open position. Ultimately, piston sleeve 100 is fully shifted to an open position and port 104 is aligned with entry port 66 to enable flow of well treatment fluid into the valve, as illustrated in FIG. 13.

Check valve 120 holds incompressible fluid 116 in cavity 122 and maintains valve 70 in an open position even if the internal pressure is lowered. In the embodiment illustrated, a check valve 128 allows fluid from the well zone adjacent the well zone being treated to once again flow into cavity 114. This enables spring 112 to move piston member 110 back to the non-actuated position, as illustrated in FIG. 13. In this embodiment, the overall valve 70 is actuated to an open position when the pressure differential between the internal pressure and the pressure of the adjacent zone is sufficient to initiate actuation of primer section 96. The valve 70 can be returned to its closed position by moving seal member 84 off bore region 54 which allows the incompressible fluid trapped in cavity 122 to flow outwardly through port 92, as illustrated in FIG. 14. Spring 106 is then able to bias piston 98 and piston sleeve 100 to the closed position.

As illustrated in FIG. 15, valve 70 also may be constructed for actuation between a closed and open position without creation of pressure differentials. In the embodiment illustrated, valve 70 is magnetically operated by creation of a magnetic force via a magnetic component 130 located in the completion string near the isolation packer 52. As the valve 70 is moved through the isolation packer 52 and seal element 84 engages bore region 54, the magnetic component 130 acts against a magnetic piston 132. The magnetic force acting against magnetic piston 132 is sufficient to compress a spring 134 and to open the valve 70, as illustrated in FIG. 15. Spring 134 normally biases the valve toward a closed position. The magnetic component can be located to open valve 70 before or after the seal is formed between valve 70 and bore region 54. The timing of the valve opening relative to formation of the seal also can be adjusted for certain other types of valves, such as mechanically actuated valves.

One or more of the washpipe valves 70 also can be coupled with an in-line valve 136, as illustrated in FIGS. 16-19. The in-line valve 136 can be used to isolate a bottom portion of the service tool 60 and can be constructed in a variety of configurations. For example, FIGS. 16 and 17 illustrate an embodiment of in-line valve 136 that uses a one-way valve, e.g. a check valve, 138 that seals against a seat 140 to prevent flow to the section of the washpipe below the corresponding valve 70. When valve 70 is biased to its closed position, one-way valve 138 is open, as illustrated in FIG. 16, and fluid is free to flow through check valve ports 142. However, when valve 70 is shifted to an open position, one-way valve 138 seats against seat 140 and prevents flow into the lower section of the service tool, as illustrated in FIG. 17.

Another embodiment of in-line valve 136 is illustrated in FIGS. 18 and 19. In this embodiment, in-line valve 136 uses a two-way valve, e.g. a ball valve, 144 that can be moved along a seat 146 to selectively allow and prevent flow to the section of the washpipe below the corresponding valve 70. When valve 70 is biased to its closed position, two-way valve 144 is open, as illustrated in FIG. 18, and fluid is free to flow through to the lower section of the service tool. However, when valve 70 is shifted to an open position, two-way valve 144 is rotated to a closed position via a linkage 148, as illustrated in FIG. 19.

The unique service tool 60 can be used in a variety of well treatment applications. One example is a sand control application in which a gravel slurry is circulated into the desired treatment zone 40 through the crossover exit port 64 and corresponding circulating port. Gravel is placed in the well zone and dehydrated from the bottom up. The return fluid passes through the corresponding screen 48 and into the annulus between screen 48 and service tool 60. The return fluid flows into the entry port 66 at the lower end of the well zone and is directed upwardly into the wellbore annulus above service tool 60. As in other gravel packing operations, the service tool is moved to a reverse position when screenout is achieved. Pressure applied in the wellbore annulus forces the slurry that remains in the tubing uphole to the surface. The service tool 60 is then moved to the next well zone and the operation is repeated. The plurality of valves 70 enables optimization of the sand control treatment or other well treatment by enabling adjustment of the length of the service tool to correspond with the length of the subsequent well zone. Even when the length of the service tool is adjusted, the return fluid port 66 is maintained at the lower end of the treated well zone.

The embodiments described above provide examples of well treatment systems that can be used to perform sand control treatments as well as other well treatments. The configuration of the completion assembly and service string can be changed according to requirements of a given treatment operation. Other components can be added, removed or interchanged to facilitate the treatment operation. For example, a variety of valves 70 can be used, including pressure actuated valves, magnetically actuated valves, mechanically actuated valves, and other valves that are capable of enabling the effective length of the service tool to be adjusted. Other components, such as a service string position indicator, can be added to further facilitate the operation. Additionally, the isolation of zones and the placement of the isolation packers can be adjusted according to parameters of the well. Furthermore, the present system and methodology can be utilized in both cased hole applications and open hole applications.

Accordingly, although only a few embodiments of the present invention have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this invention. Such modifications are intended to be included within the scope of this invention as defined in the claims.