TECHNICAL FIELD
The present invention relates generally to recovery of hydrocarbons in subterranean formations, and more particularly to a system and method for delivering treatment fluids to wells having multiple production zones or a single production zone with a relatively large reservoir height.
BACKGROUND
In typical wellbore operations, various treatment fluids may be pumped into the well and eventually into the formation to restore or enhance the productivity of the well. For example, a non-reactive “fracturing fluid” or a “frac fluid” may be pumped into the wellbore to initiate and propagate fractures in the formation thus providing flow channels to facilitate movement of the hydrocarbons to the wellbore so that the hydrocarbons may be pumped from the well. In such fracturing operations, the fracturing fluid is hydraulically injected into a wellbore penetrating the subterranean formation and is forced against the formation strata by pressure. The formation strata is forced to crack and fracture, and a proppant is placed in the fracture by movement of a viscous-fluid containing proppant into the crack in the rock. The resulting fracture, with proppant in place, provides improved flow of the recoverable fluid (i.e., oil, gas or water) into the wellbore. In another example, a reactive stimulation fluid or “acid” may be injected into the formation. Acidizing treatment of the formation results in dissolving materials in the pore spaces of the formation to enhance production flow.
Currently, in wells with multiple production zones, it may be necessary to treat various formations in a multi-staged operation requiring many trips downhole. Each trip generally consists of isolating a single production zone, perforating the isolated zone, and then delivering the treatment fluid to the isolated zone. Since several trips downhole are required to isolate and treat each zone, the complete operation may be very time consuming and expensive.
Accordingly, there exists a need for systems and methods to deliver treatment fluids to multiple zones of a well in a single trip downhole.
SUMMARY
The present invention relates to a system and method for delivering a treatment fluid to a well having multiple production zones or a single production zone with a relatively large reservoir height. According to some embodiments of the present invention, a well completion system having one or more zonal communication valves is installed and/or deployed in a wellbore to provide zonal isolation and establish hydraulic communication with each particular well zone for facilitating delivery of a treatment fluid or squeezing remedial cement. Each communication valve may be set to an open position, a closed position, and a filtering position.
Other or alternative embodiments of the present invention will be apparent from the following description, from the drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The manner in which these objectives and other desirable characteristics can be obtained is explained in the following description and attached drawings in which:
FIG. 1 illustrates a profile view of an embodiment of the multi-zonal well completion system of the present invention having zonal communication valves being installed/deployed in a wellbore.
FIGS. 2A-2C illustrate cross-sectional profile views of an embodiment of a sliding sleeve zonal isolation valve of the present invention.
FIGS. 3A-3C illustrate cross-sectional profile views of an embodiment of a sliding sleeve zonal isolation valve of the present invention being installed/deployed in a wellbore, and shifted between closed, open, and filtering positions.
FIGS. 4A-4B illustrate cross-sectional profile views of an embodiment of a sliding sleeve zonal isolation valve of the present invention having a screen protector that is a mechanical sleeve.
FIGS. 5A-5B illustrate cross-sectional profile views of an embodiment of a sliding sleeve zonal isolation valve of the present invention having a screen protector that is a set of shearable caps.
FIGS. 6A-6B illustrate cross-sectional profile views of an embodiment of a sliding sleeve zonal isolation valve of the present invention having a screen protector that is a dissolvable or degradable sheet or coating.
FIG. 7 illustrates a cross-sectional profile view of an embodiment of a sliding sleeve zonal isolation valve of the present invention having a metering mechanism.
FIG. 8 illustrates a cross-sectional profile view of an embodiment of a system of sliding sleeve zonal isolation valves of the present invention having control lines.
FIG. 9 illustrates a cross-sectional profile view of an embodiment of a system of sliding sleeve zonal isolation valves of the present invention having a sealing assembly for sealing with a downhole string.
FIGS. 10A-10F illustrate cross-sectional profile views of an embodiment of an operational method of the present invention with a downhole tool having a sealing mechanism (e.g., a packer assembly located above the shifting profile).
FIGS. 11A-10F illustrate cross-sectional profile views of an embodiment of an operational method of the present invention with a downhole tool having a sealing mechanism to facilitate fracturing operations.
It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
DETAILED DESCRIPTION OF THE INVENTION
In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those skilled 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.
In the specification and appended claims: the terms “connect”, “connection”, “connected”, “in connection with”, and “connecting” are used to mean “in direct connection with” or “in connection with via another element”; and the term “set” is used to mean “one element” or “more than one element”. As used herein, the terms “up” and “down”, “upper” and “lower”, “upwardly” and downwardly”, “upstream” and “downstream”; “above” and “below”; and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly describe some embodiments of the invention. Moreover, the term “sealing mechanism” includes: packers, bridge plugs, downhole valves, sliding sleeves, baffle-plug combinations, polished bore receptacle (PBR) seals, and all other methods and devices for temporarily blocking the flow of fluids through the wellbore. Furthermore, the term “treatment fluid” includes any fluid delivered to a formation to stimulate production including, but not limited to, fracing fluid, acid, gel, foam or other stimulating fluid.
Generally, this invention relates to a system and method for completing multi-zone wells (or, alternatively, wells with relatively large reservoir heights) by delivering a treatment fluid to achieve productivity, or for delivering remedial cement to target areas as necessary. Typically, such wells are completed in stages that result in very long completion times (e.g., on the order of four to six weeks). The present invention may reduce such completion time (e.g., to a few days) by facilitating multiple operations, previously done one trip at a time, in a single trip.
In general, embodiments of the present invention include a system of one or more zonal isolation valves movable (e.g., by shifting, rotating, indexing, or other means) between three positions: (1) an open position whereby a treatment fluid may be pumped/injected into the well, (2) a closed position whereby communication is interrupted between the well and the interior of the valve, and (3) a filtering position whereby a fluid (e.g., a produced hydrocarbon or other production or return fluid) is free to flow from the well into the interior of the valve via a filtering medium (e.g., sand screen).
FIG. 1 illustrates an embodiment of the well completion system of the present invention for use in a wellbore 10. The wellbore 10 may include a plurality of well zones (e.g., formation, production, injection, hydrocarbon, oil, gas, or water zones or intervals) 12A, 12B. The completion system includes a casing 20 having one or more zonal isolation valves 25A, 25B arranged to correspond with each formation zone 12A, 12B. The zonal isolation valves 25A, 25B function to regulate hydraulic communication between the axial bore of the casing 20 and the respective formation zone 12A, 12B. For example, to deliver a treatment fluid to formation zone 12B, valve 25B is opened and valve 25A is closed. Therefore, any treatment fluid delivered into the casing 20 from the surface will be delivered to zone 12B and bypass zone 12A. The valves 25A, 25B of the well completion system may include a sliding sleeve assembly 36 to selectively open or close a port 32 and a sand screen assembly 38 (or other filter assembly) to selectively filter or not filter the port 32. Furthermore, while this embodiment describes a completion system including a casing, in other embodiments any tubular string may be used including a casing, a liner, a tube, a pipe, or other tubular member. While only two valves are shown, in other system embodiments there may be one, two, three, or more valve assemblies installed in a well casing.
Regarding use of the well completion system of the present invention, some embodiments may 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 the valves and casing of the completion system may be cemented in place as a permanent completion. In such embodiments, the cement serves to isolate each formation zone.
FIGS. 2A-2C illustrate an embodiment of a zonal isolation valve 12. FIG. 2A illustrates a zonal isolation valve in a “filtering position” (e.g., for production). FIG. 2B illustrates a zonal isolation valve in an “open port position” (e.g., for treatment). And, FIG. 2C illustrates a zonal isolation valve in a “closed port position” (e.g., for bypassing the underlying well zone).
The zonal isolation valve 25 includes an outer housing 30 having an axial bore therethrough and which is connected to or integrally formed with a casing (or liner, or any tubular string both cemented or uncemented). The housing 30 has a set of housing ports 32 formed therein for establishing communication between the wellbore and the axial bore of the housing. In some embodiments, the housing may protrude radially outward to minimize the gap between the valve 12 and wellbore 10 (as shown in FIG. 1). By minimizing the gap between the housing and the formation, the amount of cement interfering with communication via the ports 32 is also minimized. A sleeve 36 is arranged within the axial bore of the housing 30. Furthermore, a tubular sand screen assembly 38 is arranged within the housing 30 and connected to the sleeve 36. The sand screen assembly 38 includes a filtering media (e.g., wire-wrap or wire-mesh) to filter produced fluids from the ports 32 when the sand screen assembly 38 is aligned with the ports 32. The sleeve 36 is moveable between: (1) an “open port position” whereby a flow path is maintained between the wellbore and the axial bore of the housing 30 via the set of ports 32, (2) a “closed port position” whereby the flow path between the wellbore and the axial bore of the housing 30 via the set of ports 32 is obstructed by the sleeve 36, and (3) a “filtering position” whereby the flow path between the wellbore and the axial bore of the housing 30 via the set of ports 32 is interrupted by the sand screen assembly 38, which facilitates filtering of fluids following such flow path.
Actuation of the zonal communication valve (sliding sleeve and sand screen assemblies) may be achieved by any number of mechanisms including, but not limited to, darts (see U.S. Pub. No. 2006/0124310, which disclosure of dart actuation is incorporated herein by reference), tool strings, control lines, (see U.S. Pub. No. 2006/0124312, which disclosure of control line actuation is incorporated herein by reference), electrical lines selectively powering solenoids for valve shifting, and drop balls (see U.S. Pub. Nos. 2006/0124312 and 2007/0044958, each of which discloses use of drop ball actuation, are incorporated herein by reference). Moreover, embodiments of the present invention may include wireless actuation of the zonal communication valve as by pressure pulse, electromagnetic radiation waves, seismic waves, acoustic signals, and other wireless signaling.
With reference to FIGS. 3A-3C, embodiments of the present invention further include methods of running the above-described system and assemblies. In one such embodiment, as shown in FIG. 3A, valves 110 are provided comprising a housing 112 with one or more ports or sets of ports 114 formed therein, a sliding sleeve 122 and a filter assembly 120. The filer assembly 120 comprises a screen 124, a perforated base pipe section 126, and a screen protector 128. The screen protector 128 protects the screen 124 during run-in, installation, cementing, and treatment operations against abrasion, erosion, contamination, or other damage resulting from movement through the wellbore and/or initial operation of the well system. The screen protector 128 may be a mechanical sleeve 128A (FIG. 4A-4B), a set of shearable caps 128B (FIG. 5A-5B), or a dissolvable or degradable sheet or coating 128C (FIG. 6A-6B), which is removed before production.
In operation, once run-in on casing, installed and cemented into place, a target valve 110 is actuated to shift the sleeve 124 from the closed to the open position. In the embodiment illustrated in FIG. 3B, a service tool (or other tool or work string) 150 having a mating profile 152, a treatment port 156, and a set of sealing elements 158 is positioned inside the housing 112 of the valve 110 to sealingly engage the sleeve 122. The sleeve 122 is shifted to open the port 114 and created a treatment flow path via a bore in the service tool 150. With the port 114 open, a treatment fluid is pumped through the port 156 of the service tool 150 and into the formation. When the treatment is completed, the service tool 150 is used to shift the sleeve 122 back to the closed position, thus controlling potential fluid loss. The service tool is repositioned to the next valve (not shown) in the well, repeating the operational described above: Shift open, treat, shift closed. Each successive zone is treated in this manner. The treatments may be done bottom up, top down, or any other sequence. Alternatively, it is understood that various other methods (as described herein) may be used to shift each valve between the open and closed positions. In alternative embodiments, after targeted zonal treatment, the valve may be left open as subsequent upper valves are opened for treatment in reliance on the sand fill forming to isolate off the lower zones.
With respect to FIG. 3C, after each zone is treated, the filter assembly 120 is mechanically shifted across the port 114 formed in the housing 112 of the valve 110. The screen protector 128 is then removed such that the screen 124 and base pipe 126 filter and produced fluids from the reservoir zone into the well. Produced fluid may flow into the well through the screened ports 114.
The screen protector may be removed to facilitate production by various methods and employing various tools. In one embodiment, as shown in FIG. 4A-4B, a mechanical sleeve 128A is provided to protect the screen 124. The mechanical sleeve may be disposed on the inner wall of the perforated base pipe 126 and include a profile for engagement with an actuator (not shown) such as a drop ball, a pumpable dart, or a service tool. In some embodiments, the mechanical sleeve 128A may be held in place by a shear screw 129 or any other removable fastener (e.g., epoxy/adhesive, bolt, clip, and so forth). In operation, the actuator is made to engage the profile of the mechanical sleeve 128A and pressure is applied to the actuator to remove the sleeve from engagement with the base pipe 126 to establish a filtered flow path from the reservoir to the well via the screen 124 and perforated base pipe 126. Alternatively, in another embodiment (not shown), the mechanical sleeve may be punctured (instead of shifted) by a mechanical punching tool run from surface.
In another embodiment, as shown in FIGS. 5A-5B, a set of removable caps or plugs 128B is provided such that each perforation hole in the base pipe 126 is covered by a cap or plug to isolate the screen 124. In operation, the set of caps or plugs 128B is removable by disengagement with the perforated base pipe 126 using a drop ball, dart, or service tool to shear or otherwise remove each cap or plug. The ball, dart, or service tool has a profile with an outer diameter sufficiently large enough to engage the radially inward protruding caps or plugs. Once the caps or plugs 128B are removed from engagement with the base pipe 126, a filtered flow path from the reservoir to the well via the screen 124 and perforated base pipe 126 is established.
In still another embodiment, as shown in FIGS. 6A-6b, a sacrificial member 128C (e.g., a dissolvable or degradable sheet or coating) is provided such that each perforation hole in the base pipe 126 is covered by the sacrificial member to temporarily isolate the screen 124. The sacrificial member 128C may comprise a dissolvable or degradable sheet or coating disposed on the inner wall of the perforated base pipe 126. Some embodiments of such sacrificial members are as those described in U.S. Ser. No. 11/555,404, filed Nov. 1, 2006, which is incorporated herein by reference. In operation, the sacrificial member 128C is removed (e.g., by dissolving in wellbore fluids or a fluid agent or by breaking up where the member is frangible) from the base pipe 126 to establish a filtered flow path from the reservoir to the well via the screen 124 and perforated base pipe 126.
Where the sacrificial member 128C is formed of a dissolvable material, in one embodiment, the dissolvable material may be selected to dissolve at a desired rate when exposed to well fluid within wellbore. Accordingly, the dissolving of the temporary covering 128C is controlled by submerging dissolvable material in fluids found within wellbore during movement of the valve 110 to a desired location within the wellbore. Alternatively, fluid agents also can be added to the wellbore to control the dissolving of material. The dissolvable material may be formed from a variety of materials depending on the specific application and environment in which it is used. For example, the materials selected may vary depending on the potential heat and pressures in a given wellbore environment. The materials selected also may depend on the types of well fluids encountered in a given wellbore environment. Examples of dissolvable material comprise highly reactive metals such as calcium, magnesium or alloys thereof, or materials that dissolve in acidic or basic fluids, e.g. aluminum, polymers or specially formulated plastics. Examples of suitable materials used to form a coating comprise aluminum or other metals that can be removed with acid or specifically formulated chemicals. Other examples of materials comprise low-temperature plastics or elastomers that fail at higher pressures or temperatures. Additional examples of suitable materials comprise metallic coatings that differ greatly in thermal expansion coefficient relative to their carrier material, such that the coating material fractures and breaks away at elevated temperatures.
Still with respect to FIGS. 6A-6B, in some embodiments of the present invention, the sacrificial member 128C is formed by a dissolvable element temporarily protected by a coating designed to prevent exposure of dissolvable material to dissolving fluids until a desired time following the valve installation and/or treatment operation. The coating can be degraded or otherwise removed by providing an appropriate input downhole. For example, the coating can be selected such that it is sensitive to heat. In this embodiment, once the coating is exposed to sufficient heat at a desired depth within wellbore, the coating is degraded which exposes the inner element to well fluids able to dissolve the inner layer. In another embodiment, the coating can be designed to degrade under sufficient pressure provided either naturally at certain wellbore depths or artificially by applying pressure to the wellbore from, for example, a surface location. In other embodiments, the coating can be designed to degrade when exposed to specific chemicals directed downhole. In any of these embodiments, the coating prevents the disappearance of the inner element until a specific time period in which the pressure or temperature, for example, causes the coating to fail, thus initiating dissolving of inner element. Once the inner element is dissolved, the sacrificial member 128C is gone and the screen 124 is exposed for filtering operations.
Now, with respect to moving the filtering assembly into place, the filter assembly may be mechanically shifted across the ports by various methods and employing various tools, including: drop balls, pumped darts, or by mating profiles in the service tool (or other tool string). Other methods of moving the filter assembly include non-mechanical (e.g., hydraulic) means. For example, as shown in FIG. 7, the filter assembly 120 may be metered to move relatively slowly downward as soon as the sliding sleeve 122 of the valve 110 is shifted into the open position. Metering oil through a tight restriction 121 may be used to provide a time delay for the treatment to occur before the filter assembly 120 is displaced across the port 114. In another example, as shown in FIG. 8, where an upper valve 110U having a port 114U, a sleeve 122U and a filter assembly 120U and a lower valve 110L having a port 114L, a sleeve 122L and a filter assembly 120L is provided, a first control line 1001 is run between a surface location (or, alternatively, from a control hub located above the valves but below the surface) and an area A1 within valve 110U defined by the sliding sleeve 122U and above the piston 127U. A second control line 1002 is run between an area A2 within valve 110U defined by the sliding sleeve 122U and below the piston 127U and an area A3 within valve 110L defined by the filter assembly 120L and above the piston 125L. In this case, when the upper valve 110U is opened by communicating pressure from the surface down control line 1001, the second control line 1002 is pressurized to shift the filter assembly 120L of the lower valve 110L across the port 1114L.
With respect to FIG. 9, in an alternative embodiment of the present invention, a system of zonal isolation valves 200 run casing 230 and installed in a well 210 includes a bottom valve 200A having a housing 201 with a port 202 formed therein and a sliding sleeve 204 and filtering assembly 206 as described in the various embodiments above. The bottom zonal isolation valve 200A further includes a sealing mechanism 207 (e.g., o-rings) for sealingly engaging a work string 220. In operation, the work string 220 may be run from a surface location to stab through the sealing assembly 207 of the bottom zonal isolation valve 200A. Cement may be pumped through the work string 220 and squeezed in the annulus formed between the casing 230 and the well 210. In this way, the valves 200 are bypassed and protected by the sealing assembly 207, and the need for a screen protector (as described in embodiments above) may be unnecessary.
In some embodiments of the present invention, the zonal isolation system may include a cable (e.g., running down the outer surface of the casing) for monitoring and surveillance of wellbore parameters, such as pressure, temperature, pH, strain, and so forth. This is possible with embodiments of the present valve-actuated zonal isolation system as perforation operations are not required; and such perforation operations would likely damage any installed cable.
The invention also includes various embodiments of operational methods for treating multiple zones of a well via a zonal isolation system. One example is shown in FIGS. 10A-F. In this method, a work string 330 having a sealing mechanism 332 (e.g., a packer) and a shifting profile 334 is run in a wellbore 300 having a casing 302 cemented in place with a lower zonal isolation valve 310 and an upper zonal isolation valve 320. The valves 310, 320 are initially closed (FIG. 10A). The shifting profile 334 of the work string 330 is used to engage the lower valve 310 and shift the valve open before setting the sealing mechanism 332 (FIG. 10B). The lower zone underlying the lower valve 310 is now treated via the work string 330 (FIG. 10C). Once treatment of the lower zone is complete, the lower valve 310 is shifted closed using the shifting profile 334 of the work string 330 (FIG. 10D). In an alternative embodiment where the sand fill is sufficiently plugging the lower zones, the lower valve may not need to be shifted closed. The valve opening process is repeated to open the upper valve 320 and the upper zone is treated (FIG. 10E). The valve closing process is repeated to close the upper valve 320 (FIG. 10F). These processes of opening, treating, and closing valves may be repeated for any additional valves in the well. Once all treatment is accomplished, the valves can all be shifted to the filtering position (as described in previous embodiments) to facilitate production.
Another example is shown in FIGS. 11A-F. In this method, a work string 430 having an upper sealing mechanism 432 (e.g., a packer), a shifting profile 434, and a lower sealing mechanism 433 (e.g., a bridge plug) is run in a wellbore 400 having a casing 402 cemented in place with a lower zonal isolation valve 410 and an upper zonal isolation valve 420. The valves 410, 420 are initially closed (FIG. 11A). The lower sealing mechanism 433 is located below the lower valve 410 and set and released (FIGS. 11B and 11C). The shifting profile 434 of the work string 430 is used to engage the lower valve 410 and shift the valve open before the setting the upper sealing mechanism 432. The lower zone underlying the lower valve 410 is now treated via the work string 430 (FIG. 11C). Once treatment of the lower zone is complete, the upper sealing mechanism 432 is released and the fill is washed (FIG. 11D) and the lower sealing mechanism 433 is re-latched and unset (FIG. 11E). The work string 430 is then moved proximate the upper valve 420 and the process is repeated (FIG. 11F). In this embodiment, the lower valve 410 may be left open (or alternatively, shifted to the producing/filtered position) as the lower sealing mechanism 433 provides isolation to the lower zones. Once all treatment is accomplished, the valves can all be shifted to the filtering position (as described in previous embodiments) to facilitate production.
Yet another example is shown in FIGS. 12A-D. In this method, a work string 530 having a sealing mechanism 532 (e.g., a packer) and a shifting profile 534 (located above the sealing mechanism) is run in a wellbore 500 having a casing 502 cemented in place with a lower zonal isolation valve 510 and an upper zonal isolation valve 520. The valves 510, 520 are initially closed (FIG. 12A). The shifting profile 534 of the work string 530 is used to engage the lower valve 510 and shift the valve open before setting the sealing mechanism 532 (FIG. 12B). The lower zone underlying the lower valve now receives annulus pressurize (e.g., using a fracturing means like hydraulic fracturing) to break the cement external and proximate the lower valve 510. The sealing mechanism 532 may now be unset, the work string 530 moved proximate the upper valve 520, and the sealing mechanism 532 reset to break the cement external and proximate the lower valve 520 using annulus fracturing means. Once the targeted zones underlying the valves 510, 520 are fractured, the zones may be treated via the work string 530. Once all treatment is accomplished, the valves can all be shifted to the filtering position (as described in previous embodiments) to facilitate production.
While the invention has been disclosed with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover such modifications and variations as fall within the true spirit and scope of the invention.
Patent Application
20090084553
