System and method for completing multiple well intervals

[0001] This is a continuation-in-part of U.S. Ser. No. 10/905,073, filed Dec. 14, 2004, entitled “SYSTEM FOR COMPLETING MULTIPLE WELL INTERVALS.”

[0002] 1. Field of the Invention

[0003] 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.

[0004] 2. Background of the Invention

[0005] 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 reactive or 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.

[0006] 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 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.

[0007] Accordingly, there exists a need for systems and methods to deliver treatment fluids to multiple zones of a well in a single trip downhole.

[0008] The present invention relates to a system and method for delivering a treatment fluid to a well having multiple well zones (e.g., production zones). According to some embodiments of the present invention, a well completion system is provided having: (1) a casing installed in a wellbore such that the casing intersects one or more well zones, (2) a perforated interval formed at each well zone to establish hydraulic communication with the underlying formation at each particular well zone for delivery of a treatment fluid or for receiving a production fluid, and (3) a flapper valve installed in the wellbore at each well zone above the perforated interval to provide zonal isolation between the various well zones.

[0009] Another embodiment of the well completion system of the present invention includes a mechanism for selectively actuating the flapper valves. For example, one such mechanism may be a perforating gun, which actuates a selected flapper valve upon detonation.

[0010] Still another embodiment of the well completion system of the present invention includes a perforating gun string including multiple perforating guns that may be fired selectively in each zone of a multi-zonal well. This embodiment also includes a lubricator for storing the gun string at the surface while each well zone is treated.

[0011] Other or alternative embodiments of the present invention will be apparent from the following description, from the drawings, and from the claims.

[0016] 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.

[0017] 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.

[0018] 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 “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.

[0019] Generally, this invention relates to a system and method for completing multi-zone wells by delivering a treatment fluid to achieve productivity. 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.

[0020] 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) 12, 14. The completion system includes a casing 20 having one or more zonal isolation valves 30 integrated or connected inline with the casing and arranged to correspond with each formation zone 12, 14. Each zonal isolation valve 25 is arranged at or just below the corresponding well zone 12, 14 and includes a flapper 32 and a flapper-actuating mechanism 34. However, exact depth positioning of the flapper 32 of each zonal isolation valve 30 is not critical, as long a flapper is arranged somewhere in between each well zone to be treated. The flapper 32 may be any structure that is moveable between an open position whereby communication is established through the axial bore of the casing 20 and a closed position whereby communication is interrupted through the axial bore of the casing. The zonal isolation valves 30 function to regulate hydraulic communication through the axial bore of the casing 20 and thus to isolate a particular well zone from other well zones. For example, to deliver a treatment fluid to the formation at well zone 14, the flapper 32 of the isolation valve 30 shown just bellow well zone 14 must be closed. To close the flapper 32, the flapper-actuating mechanism 34 is activated to move the flapper into the closed position and seal the axial bore of the casing 20. Therefore, any treatment fluid injected into the axial bore of the casing 20 from the surface will be delivered to well zone 14 and blocked from communicating with well zone 12. The flapper-actuating mechanism 34 may be a control line from the surface or a tool controlled from the surface (e.g., a perforating gun). Alternatively, the flapper-actuating mechanism 34 may be controlled remotely as by pressure pulse, electromagnetic radiation waves, seismic waves, acoustic signals, radio frequency, or other wireless signaling. Moreover, while the present invention is described with respect to flapper valves, it is intended that any type of valve or combination of valves may be used to regulate communication through the axial bore of the casing including, but not limited to a flapper valve or a ball valve.

[0021] FIG. 2 illustrates an embodiment of a zonal isolation valve 30. In this embodiment, the valve 30 includes a valve housing 31 having an axial bore therethrough and which is connected to or integrally formed with a casing 20 (or other cemented-in tubular string). The housing 31 has a recess 36 defined therein for containing a flapper 32. The flapper 32 may be energized by any energy supplying device including, but not limited to, a coil spring, a linear spring, compressed gas spring, solenoid, gravity-actuated, mechanically actuated by a collet, fluid flow or hydraulic pressure. A sleeve 40 resides within the axial bore of the valve housing 31 adjacent the recess 36 to hold the flapper 32 in an energized state when the valve 30 is in the open position. The zonal isolation valve 30 further includes a mechanism for actuating the flapper 32 by shifting the sleeve 40 upward, thus allowing the flapper 32 to rotate such that the valve is in the closed position. In some embodiments, a spring (or other energizing device) is provided to energize the flapper. The sleeve 40 includes a piston ring 41 (or other piston element such as a tab or a protruding surface), which rests on or above a lower shoulder 37 formed on the inner bore of the valve housing 31. The shoulder 37 prevents the sleeve 40 from moving axially downward. An upper shoulder 38 may also be formed on the inner bore of the valve housing 31 to provide an upper stop for the piston ring 41 of the sleeve 40. An annular space 46 is defined between the valve housing 31 and the sleeve 40 for the piston ring 41 to traverse. A chamber 42 is arranged above the valve housing 31 and is hydraulically connected to the annular space 46 below the piston ring 41 via a hydraulic conduit 44. In some embodiments, the chamber 42 is an annular chamber having an axial bore sized to receive a perforating gun string. The pressure within the annular space 46 above the piston ring 41 should be less than the well pressure, but greater than the pressure within the chamber 42. Therefore, the pressure differential between the annular space 46 and the chamber 42 forces the sleeve axially downward and thus maintains the valve 30 in the closed position when the chamber is intact. In other embodiments, chambers 42 and 46 are set at a pressure of 0 psi or atmospheric pressure and the sleeve 40 may be held by a shear pin, rupture disk, or other frangible connection to hold the sleeve in place over the flapper 32. To move the zonal isolation valve 30 from the open position to the closed position, the chamber 42 is ruptured (e.g., as by detonating a shaped charge of a perforating gun) to establish communication between the wellbore 10 and the annular space 46 below the piston ring 41 via the hydraulic conduit 44. Once ruptured, well fluid flows from the wellbore 10 through the chamber 42 and into the annular space 46 below the piston ring 41 via the hydraulic conduit 44 to move the sleeve 40 axially upward. As the sleeve 40 clears the flapper 32 in the recess 36 of the valve housing 31, the energized flapper 32 is rotates to seal the axial bore of the casing 20 and move the zonal isolation valve 30 into the closed position.

[0022] FIG. 3 illustrates an embodiment of the well completion system 100 of the present invention for selectively perforating and delivering a treatment fluid to a well zone in a multi-zonal well. This well completion system 100 includes a wellbore 110 intersecting multiple well zones 112, 114. The well is supported by a casing 120, which is cemented in-place and suspended from a wellhead 130. The wellhead 130 may include: (1) an inlet conduit 132 (or multiple inlets) for injecting a treatment fluid into the wellbore 110, a lubricator 140 (or other tubular member inline with the casing and connected above the wellhead) for receiving a perforating gun string 150, and an inline valve 134 for selectively sealing the wellbore 110 during injection of treatment fluid. The inlet conduit 132 is connected to a treatment fluid supply and pump (not shown) for injection of treatment fluid into the wellbore to treat isolated well zones. The perforating gun string 150 may include a plurality of guns 152, 154 each holding one or more explosive charges and connected together by an adapter 156. The perforating gun string 150 may be suspended and run into the wellbore 110 by a line 160. The line 160 may be any structure capable of supporting and transporting the perforating gun string 150 in and out of the wellbore 110 including, but not limited to, wireline, slickline, or coiled tubing. It is intended that by using wireline or slickline, depth positioning of the perforating gun string 150 may be performed with increased accuracy over prior art completion systems (e.g., casing conveyed perforating gun systems). In other embodiments, the perforating gun may be formed integral with a pumpable dart to be deployed downhole and actuated by a wireless signal as shown in U.S. Ser. No. 10/905,372, which is incorporate herein by reference. The well completion system further includes one or more zonal isolation valves 30A, 30B for isolating and treating well zones 112 and 114 respectively. Each zonal isolation valve 30A, 30B is as described in detail above and illustrated in FIG. 2. However, it is intended that other types of valves or combinations of valves may be used to isolate particular well zones.

[0023] In operating the well completion system 100, with respect to FIG. 4, the inline valve 134 of the wellhead 130 is opened such that the perforating gun string 150 may be lowered into the well. In order to treat the well zone 112 underlying the casing 120, the perforating gun string 150 is first suspended by the line 160 and lowered to the target depth, which corresponds with the chamber 42A of valve 30A via the wellhead 130.

[0024] With respect to FIG. 5, once the perforating gun string 150 is lowered to the target depth at well zone 112 such that the lower-most gun 152 is adjacent the chamber 42A of valve 30A, the gun is detonated. The explosive charges of the lower gun 152 ignite and penetrate the surrounding formation at well zone 112 and simultaneously rupture the chamber 42A. In some embodiments, the perforating gun string 150 may be oriented, centralized, and positioned in the wellbore 110 as desired before ignition to create more uniform size penetrations. With more uniform sized penetrations, the treatment fluid subsequently delivered may be more equally distributed around the casing 120.

[0025] With respect to FIG. 6, with the chamber 42A ruptured, well fluid from the surrounding formation well zone 112 enters the chamber 42A and acts against the piston ring 41A via the hydraulic conduit 44A to move the sleeve 40A axially upward.

[0026] With respect to FIG. 7, once the sleeve 40A has been shifted upward a sufficient distance, the energized flapper 32A rotates to seal the axial bore of the casing 120. At this point, the well zone 112 is isolated from any other well zones below the valve 30A.

[0027] With respect to FIG. 8, once the well zone 112 is isolated, the perforating gun string 150 is pulled from the wellbore 110. A treatment fluid may then be injected into the perforated well zone 112 via the inlet conduit 132. In some embodiments, the gun string 150 may remain in the lubricator 140, which is sealed off from the wellbore 110 by the inline valve 134, instead of being removed from the completion system 100 all together. Each of the guns in the gun string are selectively detonated a each corresponding well zone. In such embodiments, significant operating time and cost saving may be achieved and more individual formation layers may be treated offering increased productivity.

[0028] With respect to FIG. 9, after treatment of well zone 112 is completed, it may be desirable to treat an upper well zone 114. In this event, inline valve 134 of wellhead 130 is opened and the perforating gun string 150 is lowered to the target depth such that the lower-most gun 154 is adjacent the chamber 42B of valve 30B. In this position, the gun 154 is detonated. The explosive charges of the upper gun 154 ignite and penetrate the surrounding formation at well zone 114 and simultaneously rupture the chamber 42B.

[0029] With respect to FIG. 10, with the chamber 42B ruptured, well fluid from the surrounding formation well zone 114 enters the chamber 42B and acts against the piston ring 41B via the hydraulic conduit 44B to move the sleeve 40B axially upward. Once the sleeve 40B has been shifted upward a sufficient distance, the energized flapper 32B rotates to seal the axial bore of the casing 120. At this point, the well zone 114 is isolated from well zone 112 and any other well zones below the valve 30B.

[0030] With respect to FIG. 11, once the well zone 114 is isolated, the perforating gun string 150 is pulled from the wellbore 110. A treatment fluid may then be injected into the perforated well zone 114 via the inlet conduit 132. Again, in some embodiments, the gun may remain in the lubricator 140, which is sealed off from the wellbore 110 by the inline valve 134.

[0031] In some embodiments, the well zones are selectively isolated and perforated starting from the bottom-most well zone and progressing uphole. In this way, each well zone is isolated from other downhole well zones by the zonal isolation valve and from other uphole well zones by the casing, which is not yet perforated for the uphole well zones.

[0032] Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.