Many wells are fractured with a proppant (e.g., sand or the like) to treat a formation and improve production. In many cases, multiple fracs are performed in a single wellbore to treat various zones of interest in the formation. Systems exist in the art that allow operators to frac multiple zones in a single trip in the wellbore. Some systems even use a wellscreen to prevent proppant flowback during operations.
Unfortunately, current systems that include a wellscreen use a service crossover tool for operation. The crossover tool crosses over the fluid flow path from a workstring to the annulus outside the wellscreen and vice versa. However, using the crossover tool has a number of disadvantages.
The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
A multi-zone frac assembly for a borehole has a tubular structure disposed in the borehole and defining a through-bore. A plurality of sections disposed on the tubular structure each has an isolation element, a flow valve, a screen, and a check valve. The isolation element, which can be a swellable packer, a hydraulically-set packer, or a mechanically-set packer, isolates a borehole annulus around the section from the other sections along the borehole. If desired, a flow tube can be disposed in the borehole annulus and can communicate through the isolation elements between one or more of the sections.
The flow valve is selectively operable between opened and closed conditions. Thus, the flow valve in the opened condition permits fluid communication between the through-bore and the borehole annulus, but the flow valve in the closed condition prevents fluid communication between the through-bore and the borehole annulus.
The screen disposed on the tubular structure communicates with the borehole annulus, and the check valve is in fluid communication between the screen and the through-bore. The check valve permits fluid communication from the screen into the through-bore, but prevents fluid communication from the through-bore to the screen.
In one arrangement, at least a portion of the tubular structure for a given one of the sections includes a basepipe having the through-bore and defining at least one pipe port communicating the through-bore outside the basepipe. Disposed on the basepipe, the check valve permits fluid communication from the screen to the at least one pipe port and prevents fluid communication from the at least one pipe port to the screen.
In particular, the check valve can have a housing disposed on the basepipe, and the screen can have one end in fluid communication with the housing. The housing has at least one internal flow passage and has at least one check ball. The at least one internal flow passage communicates the screen with the at least one pipe port. To control flow, the at least one check ball is movable relative to the at least one internal flow passage. In one condition, the at least one check ball permits fluid communication through the at least one internal flow passage, while in another condition, the at least one check ball prevents fluid communication through the at least one internal flow passage.
In one arrangement, the flow valve is a sliding sleeve having a housing and in insert movable therein. The housing has a flow port communicating the through-bore outside the housing, and the insert is movable in the housing between the closed condition preventing fluid communication through the flow port and the opened condition permitting fluid communication through the flow port.
To move the seat, the insert has a seat disposed therein that seats a plug deployed in the tubular structure thereon and moves the insert from the closed condition to the opened condition in response to application of fluid pressure against the seated plug.
In other arrangements, the insert can be moved by a shifting tool. In particular, the assembly can have a workstring disposing in the through-bore of the tubular structure. The workstring has an actuating tool and defines a fluid passageway therethrough. An outlet port communicates the fluid passageway outside the workstring. In the assembly, the workstring is operable to open and close the flow valve of each section with the actuating tool. The workstring is operable to seal inside the assembly and place the outlet port in sealed fluid communication with the borehole annulus when the flow valve has the opened condition.
If desired, the assembly can have a bypass tube for at least one of the sections. The bypass tube communicates a first portion of the through-bore on one side of a location of the workstring sealed inside the assembly to another side of the location.
In a multi-zone frac method for a borehole, an assembly disposes in the borehole, and an annulus of the borehole around the assembly is isolated into a plurality of isolated zones. To isolate the annulus, for example, the method can involve engaging packing elements on the assembly against the borehole.
Fluid communication from the annulus of the isolated zones is screened into a through-bore of the assembly with screens on the assembly, and fluid communication is prevented from the through-bore to the annulus of the isolated zones through the screens. For example, screening the fluid can involve allowing fluid communication from the screens through perforations in the assembly communicating with the through-bore, and prevent fluid communication from the through-bore to the annulus can involve disposing a check valve in fluid communication between the screens and the perforations.
In the method, treating each of the isolated zones with a treatment fluid is achieved by: selectively opening a port in the assembly at the each isolated zone, and flowing the treatment fluid down the through-bore to the each isolated zone through the opened port. For example, selectively opening the port in the assembly at the each isolated zone involves opening the port in the assembly by moving an insert in the assembly away from the port. Further, selectively closing the opened ports in the assembly can be achieved at each of the isolated zones.
In moving the insert in the assembly away from the port, the method in one arrangement involves engaging a plug on the insert; and moving the insert away from the port with application of fluid pressure against the engaged plug. Then, to flow the treatment fluid down the through-bore to the each isolated zone through the opened port, the treatment fluid can flow through the opened port when the insert is moved away from the port. In this way, treating each of the isolated zones with the treatment fluid involves successively treating the isolated zones uphole on the assembly by successively engaging plugs and moving inserts uphole on the assembly for successive ones of the isolated zones. Once treatment is completed, the engaged plug can be remove, and the insert can be selectively closed over the opened port in the assembly.
In another arrangement to move the insert in the assembly away from the port, the insert can be engaged with a workstring disposed in the through-bore of the assembly, and the insert can be moved away from the port with movement of the engaged workstring. In this arrangement, flowing the treatment fluid down the through-bore to the each isolated zone through the opened port involves flowing the treatment fluid through an outlet in the workstring and through the opened port when the insert is moved away from the port. In this way, treating each of the isolated zones with the treatment fluid involves successively closing a given one of the insert with the workstring after treatment, and successively opening another one of the inserts with the workstring before treatment.
Various embodiments of a multi-zone screened frac system are disclosed. The system does not require a crossover tool as required in the prior art. In some implementations, the system does not even require a complete service tool. To perform a frac operation on multiple zones in a cased or open borehole, the system combines: (1) wellscreens with integrated check valves, (2) frac valves, and (3) optional shunt tubes for slurry dehydration. The system can also include fiber optic technology.
In a first embodiment according to the present disclosure,
Internally, the production string 22 of the frac assembly 20 has a through-bore 25 communicating along the length of the string 22 and communicating with the completion string 14. Externally, the frac assembly 20 has isolation devices 18, such as but not limited to a hydraulic, a mechanical, or a swellable packer, to seal the production string 22 in the casing 12. One of the isolation devices 18 is disposed at the string 22's uphole end 24, while other isolation devices 18 are disposed along the length of the production string 22. Separated by the isolation devices 18, the frac assembly 20 has various sections 28 disposed at various intervals or zones of interest in the surrounding formation. At its downhole end 26, the frac assembly 20 has a bottom seat 50 for engaging a setting ball 54 during frac operations.
Each section 28 has a selective frac valve 30 and a flow device 40. Each of the selective frac valves 30 and flow devices 40 in a given section 28 is separated from other sections 28 by isolation elements 18, which isolate the borehole annulus 15 for the respective sections 28. As shown, the selective frac valves 30 are disposed uphole of the flow devices 40 in the various sections 28. As an alternative, the selective frac valves 30 can be disposed downhole of the flow devices 40 in each section 28.
The selective frac valves 30 have one or more ports 32 that can be selectively opened and closed during operation. In this arrangement and as discussed in more detail below, for example, each of the selective frac valves 30 can be opened to communicate their ports 32 with the surrounding annulus 15 by using frac plugs or balls 34 deployed downhole during frac operations. As treatment is performed in the well, these dropped plugs or balls 34 selectively open the frac valves 30 and isolate lower sections 28 so the selective frac valves 30 can successively divert frac treatment to adjacent zones of interest up the frac assembly 20.
The flow device 40 for each section 28 is disposed adjacent or near perforations 13 in the casing 12. In this and other assemblies disclosed herein, the flow devices 40 use wellscreens 42 with integrated check valves 44 to control the flow of fluid through the devices 44. In particular, each flow device 40 exclusively screens fluid communication through a first flow path (i.e., flow from the borehole annulus 15 to the through-bore 25 of the assembly 20 through the flow device 40). At the same time, the flow device 40 exclusively prevents fluid communication from the through-bore 25 of the assembly 20 to the borehole annulus 15 along this first flow path. Thus, the wellscreen 42 screens fluid flow along the first flow path from the borehole annulus 15 to the through-bore 25. However, the flow device 40 does not permit fluid flow in the opposite direction along this same flow path, but in the opposite direction from the through-bore 25 to the borehole annulus 15.
In particular, the flow devices 40 can each include a wellscreen 42 and an inflow control device 44, such as a FloReg™ Deploy-Assist (DA) Device available from Weatherford International. Preferably, the inflow control device 44 lacks nozzles and is used in the system primarily as a check valve, but nozzles can be used in other arrangements. Further details of a suitable flow device 40 having a wellscreen 42 and an inflow control device 44, such as the FloReg™ Deploy-Assist (DA) Device, are provided below in
In this and other assemblies disclosed herein, each selective frac valve 30 selectively permits and prevents fluid communication through a second flow path (i.e., between the through-bore 25 of the assembly 20 and the borehole annulus 15). In particular, the selective frac valves 30 can be sliding sleeves, such as a ZoneSelect™ MultiShift frac sliding sleeve available from Weatherford International. The selective frac valve 30 is designed to open when a ball 34 lands on a landing seat (not shown) disposed in the selective frac valve 30 and tubing pressure is applied to shear the selective frac valve 30 open to expose the through-bore 25 to the surrounding annulus 15. The balls 34 are dropped from the surface once the appropriate amount of proppant is pumped into each zone 28. Further details of a suitable multi-shift sliding sleeve, such as the ZoneSelect™ MultiShift frac sliding sleeve, are provided below in
In this and other assemblies 10 disclosed herein, a fracing operation uses the series of packers 18 and selective frac valves 30 to sequentially isolate the different zones or sections 28 of the downhole formation. Initially, the assembly 20 having the packers 18, selective frac valves 30, and flow devices 40 is run downhole and set up using known techniques. Eventually, a bottom plug or ball 54 is pumped downhole to close off the flow path through the assembly's bottom end 50.
Next, operators set the packers 18 to create the multiple isolated sections 28 down the borehole annulus 15. How the packers 18 are set depends on the type of packers 18 used. For example, hydraulic pressure pumped down the assembly's through-bore 25 can be used to set the packers 18. The closed bottom end 50, the closed frac valves 30, and the integrated check valves 44 prevent fluid pressure in the assembly 20 from escaping to the annulus 15 during the setting procedures. Use of different types of packers 18 would require other known procedures.
Once the packers 18 are set, operators apply a frac treatment successively to each of the isolated sections 28 by selectively opening the selective frac valves 30 and allowing the treatment fluid to interact with the adjacent zones of the formation through the opened ports 32. To open each frac valve 30, for example, operators drop specifically sized plugs or balls 34 into the assembly 20 and land them on corresponding seats (not shown) on the designated frac valves 30. Typically, the balls 34 increase in size up the borehole so that a smaller ball 34 can pass through all of the seats (not shown) on the uphole frac valves 30 before engaging its designated seat further downhole. For example, a range of plugs or balls 34 may allow fracturing up to 13, 19, and 21 sections in the borehole when 3½ in., 4½ in., and 5½ in. frac valves 30 are used, respectively. An additional section can be added by using a toe sleeve (not shown).
Once a dropped ball 34 is seated, the ball 34 closes off the lower section 28 just treated, and built up pressure on the seated ball 34 forces the frac valve 30 open so frac fluid can interact with the adjacent zone of the formation through the open flow ports 32. Operators repeat this process up the assembly 20 to treat all of the sections 28 by successively dropping bigger balls 34 against bigger seats (not shown) in the frac valves 30. Once the frac treatment is complete, flow in the assembly 20 can float all the balls 34 to the surface, or operators can mill out the balls 34 and ball seats (not shown) from the frac valves 30. Finally, after fracing, the system 10 may need a clean-out trip in which a fluid wash is pumped down the assembly 10 to clear it of excess or residual proppant and frac fluid.
The multi-zone frac system 10 of
In a second embodiment according to the present disclosure, the multi-zone screened frac system 10 of
The dehydration tube 60 communicates with the borehole annulus 15 of each of the sections 28 using flow ports (not shown) or the like. Additionally, the tube 60 passes through the packers 18 isolating the sections 28. Use of the tube 60 is beneficial when frac pack operations are performed, which involve fracing a zone of interest and then gravel packing the borehole annulus 15 around the wellscreen 42. In this way, use of the tube 60 in the system 10 allows dehydration of the annular gravel pack when performed.
After fracing operations, the system 10 in
As noted above in
How the liner hanger and packer assembly 17b and the expandable liner 17a are installed in the borehole will be appreciated by one skilled in the art with the benefit of the present disclosure so that particular details are not provided here. Briefly though, the liner hanger and packer assembly 17b and expandable liner 17a are disposed downhole, and the hanger and packer assembly 17b is set by dropping a ball and applying pressure. Expansion of the liner 17a is then performed using liner expansion tools. Once the liner is set, frac operations can be performed by deploying the frac assembly 20 as described previously.
Other than a cased or lined borehole as noted above, the multi-zone screened frac system 10 can also be used for open hole completions. In a third embodiment according to the present disclosure, for example, the multi-zone screened frac system 10 of
After fracing operations, the system 10 may need a clean-out operation. As before, the frac valves 30 are disposed uphole of the flow devices 40, but they could be disposed downhole of the flow devices 40 in each section 28. As another alternative, slurry de-hydration tubes (not shown) could also be used along the assembly 10.
The multi-zone frac system 10 of
In a fourth embodiment according to the present disclosure, the multi-zone screened frac system 10 in
The frac operation for the system 10 of
Details about opening the frac valves 30 are provided below with reference to
Once a given frac valve 30 is opened, the seals 76 on the workstring 70 can engage and seal against inner seats 36, surfaces, seals, or the like in the frac valve 30 or elsewhere in the assembly 20 on both the uphole and downhole sides of the opened ports 32. The seals 76 can use elastomeric or other types of seals disposed on the inner workstring 70, and the seats 36 can be polished seats or surfaces inside the frac valve 30 or other part of the assembly 30 to engage the seals 76. Although shown with this configuration, the reverse arrangement can be used with seals on the inside of the frac valve 30 or assembly 20 and with seats on the workstring 70.
Once the workstring 70 is seated, treatment fluid is flowed down the through-bore 75 of the workstring 70 to the sealed and opened ports 32 in the frac valve 30. The treatment fluid flows through the outlet ports 72 in the workstring 70 and through the opened ports 32 to the surrounding borehole annulus 15, which allows the treatment fluid to interact with the adjacent zone of the formation.
Once treatment is completed for the given zone, operators manipulate the workstring 70 to engage the shifting tool 78 in the frac valve 30 to close the ports 32. For example, the shifting tool 78 can engage another suitable profile on an inner sleeve of the frac valve 30 to move the sleeve and close the ports 32. At this point, the workstring 70 can be moved in the assembly 20 to open another one of the frac valves 30 to perform treatment. Operators repeat this process up the assembly 20 to treat all of the sections 28. Once the frac treatment is complete, the system 10 may not need a clean-out trip.
The multi-zone frac system 10 of
In a fifth embodiment of the multi-zone screened frac system 10 of
During a frac operation similar to that discussed above, the tubes 80 help dehydrate slurry intended to gravel pack the borehole annulus 15 of the sections 28 during a frac pack type of operation. In addition, the tubes 80 can act as a bypass for fluid returns during the operation. As treatment fluid flows from the workstring 70 seated in a frac valve 30, through the opened ports 32, and into the borehole annulus 15, the wellscreen 42 screens fluid returns from the annulus 15, and the fluid returns can flow into the assembly 20 downhole of the engagement of the workstring 70 in the assembly 20. The tubes 80 can, therefore, allow these fluid returns to flow from the downhole section of the assembly 20 to the micro-annulus between the workstring 70 and the inside of the assembly 20 uphole of the sealed engagement of the workstring 70 with the ports 32. From this point, the fluid returns can then flow to the surface.
The multi-zone frac system 10 of
As noted above, the various embodiments of the multi-zone frac system 10 in
The flow device 150 is deployed on a completion string (22:
As noted above, the inflow control device 170 can be similar to a FloReg deploy-assist (DA) device available from Weatherford International. As best shown in
For its part, the screen jacket 160 is disposed around the outside of the basepipe 152. As shown, the screen jacket 160 can be a wire wrapped screen having rods or ribs 164 arranged longitudinally along the base pipe 152 with windings of wire 162 wrapped thereabout to form various slots. Fluid can pass from the surrounding borehole annulus to the annular gap between the screen jacket 160 and the basepipe 152. Although shown as a wire-wrapped screen, the screen jacket 160 can use any other form of screen assembly, including metal mesh screens, pre-packed screens, protective shell screens, expandable sand screens, or screens of other construction.
Internally, the inflow control device 170 has a number (e.g., ten) flow ports 180. Rather than providing a predetermined pressure drop along the screen jacket 160 by using multiple open or closed nozzles (not shown), the inflow control device 170 as shown in
Internally, however, the inflow control device 170 does include port isolation balls 182, which allow the device 170 to operate as a check valve. Depending on the direction of flow or pressure differential between the inner spaces 186 and 188, the port isolation balls 182 can move to an open condition (to the right in
In general, the inflow control device 170 can facilitate fluid circulation during deployment and well cleanup and can be used in interventionless deployment and setting of openhole packers. In deployment, for example, the isolation balls 182 maximize fluid circulation through the completion shoe (50:
Should a pressure drop be desired from the screen jacket 160 to the basepipe 152, the flow ports 180 can include nozzles (not shown) that restrict flow of screened fluid (i.e., inflow) from the screen jacket 160 to the pipe's inner space 188. For example, the inflow control device 170 can have ten nozzles, although they all may not be open. Operators can set a number of these nozzles open at the surface to configure the device 170 for use downhole in a given implementation. Depending on the number of open nozzles, the device 170 can thereby produce a configurable pressure drop along the screen jacket 160.
As noted above, the various embodiments of the multi-zone frac system 10 in
When initially run downhole, the inner sleeve 230 positions in the housing 220 in a closed state (
As noted previously with respect to
Once the ball 34 is seated, built up pressure forces against the inner sleeve 230 in the housing 220, thereby shearing any shear pins and freeing the dogs 238 from the housing's annular slot to the inner sleeve 230 can slide downward. As it slides, the inner sleeve 230 uncovers the flow ports 226. Preferably, as the inner sleeve 230 shifts past the flow ports 226, fracturing does not occur through the inner sleeve 230, which protects it from erosion.
To mitigate potential damage to the sleeve 210 as the inner sleeve 230 moves downward, a shock absorber 240 can be connected to the inner sleeve 230's lower end. As shown in
After the fracturing job, the well is typically flowed clean and the ball seat 232 and remaining ball 34 is milled out. The ball seat 232 can be constructed from cast iron to facilitate milling, and the balls can be composed of aluminum or non-metallic material. Once milling is complete, the inner sleeve 230 can be closed or opened with a standard “B” shifting tool on the tool profiles 234 and 236 in the inner sleeve 230 so the sliding sleeve 210 can then function like any conventional sliding sleeve shifting with a “B” tool. The ability to selectively open and close the sliding sleeve 210 with a “B” shifting tool after milling enables operators to isolate the particular section (28:
For those embodiments of the disclosed multi-zone screen frac system 10 that do not use a ball and seat arrangement, such as in
Turning now to
In the present example, the upper tool 310 is designed to be an closing tool for closing a sliding sleeves (e.g., 210:
As detail of the closing shifting tool 310 shows a biased collet 312 that fits around the mandrel 302 and that connects at both ends to stops 314 and 316 on the mandrel 302. The collet 312 has B-profiles 318 that include an upward facing shoulder, an upper (shortened) cam, and a lower (extended) cam. As discussed above, the B-profiles 318 enable the collet 312 to engage the recessed profile (234) in the sliding sleeve (210) in the up direction and bypass the recessed profiles (234 and 236) in the sliding sleeve (210) in the down direction. This type of shifting tool is typically referred to as a B shifting tool with a B-profile.
Another arrangement of the shifting tool 78 uses a two-way shifting tool 330 as shown in
The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. It will be appreciated with the benefit of the present disclosure that features described above in accordance with any embodiment or aspect of the disclosed subject matter can be utilized, either alone or in combination, with any other described feature, in any other embodiment or aspect of the disclosed subject matter.
In exchange for disclosing the inventive concepts contained herein, the Applicants desire all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.
This is a non-provisional of U.S. Provisional Appl. 61/506,897, filed 12 Jul. 2011, which is incorporated herein by reference and to which priority is claimed.
Number | Date | Country | |
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61506897 | Jul 2011 | US |