BACKGROUND OF THE INVENTION
Field of the Invention. 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 well zones.
Background of the Invention. 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 produced 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 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 well zones. According to some embodiments of the present invention, a well completion system is provided including one or more polished bore receptacles installed in a casing and a fluid delivery device having at least one seal assembly for selectively isolating a selected well zone and delivering a fluid to the selected zone.
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 polished bore receptacles installed in a wellbore.
FIG. 2 illustrates a profile view of an embodiment of the multi-zonal well completion system of the present invention having polished bore receptacles installed in a wellbore for isolating perforated well zones and a fluid delivery tool having a sealing assembly arranged thereon for delivering a fluid to a selected perforated well zone.
FIGS. 3A-3F illustrate profile views of an embodiment of the multi-zonal well completion system of the present invention depicting a perforating gun and seal assembly arranged below a fluid delivery tool being run in a wellbore having polished bore receptacles for isolating multiple well zones.
FIGS. 4A-4B illustrate profile views of an embodiment of the multi-zonal well completion system of the present invention depicting a string of perforating guns being run in a wellbore having polished bore receptacles for isolating multiple well zones and detonated simultaneously.
FIGS. 5A-5D illustrate profile views of an embodiment of the multi-zonal well completion system of the present invention depicting a fluid delivery tool with seal assemblies arranged above and below the fluid delivery tool, the fluid delivery tool being run in a wellbore having polished bore receptacles for isolating multiple well zones.
FIG. 6 illustrates a profile view of an embodiment of the multi-zonal well completion system of the present invention depicting concentric inner and outer strings having one or more seals formed on the outer surface of the outer string for bypassing particular well zones of a wellbore having polished bore receptacles and a diverter tool connected to the bottom of the concentric strings for directing flow between inner string, the annulus defined between the outer string and inner string, and the well annulus outside the outer string.
FIGS. 7A-7D illustrate profile views of an embodiment of the multi-zonal well completion system of the present invention depicting a actuatable seal dart with a perforating gun connected above the dart, the dart being run in a wellbore having polished bore receptacles for isolating multiple well zones.
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
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: O-ring, chevron seal, V-packed seal, bonded elastomer seal, compression seal element, inflatable seal element, face seal, and all other methods and devices for engaging a polished bore receptacle and 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. Still furthermore, the terms “tubular member”, “casing”, and “liner” may be used interchangeably (e.g., any embodiment described herein for use with a casing may also be used with a liner or other tubular member). Yet furthermore, the term “polished bore receptacle” or “PBR” includes a smooth, polished, or honed bore formed on the inner surface of a tubular member (e.g., casing or liner) having a predetermined diameter for sealing or mating with a sealing mechanism.
Generally, this invention relates to a system and method for completing multi-zone wells by delivering a treatment fluid to achieve, facilitate, and/or improve 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. Moreover, some embodiments of this invention provide a system and method for completing a well without the use of inflatable packers, which may need to be set and reset to facilitate multiple zonal isolations in a single run.
FIGS. 1 and 2 illustrate 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 wellbore 10 includes a tubular member 15 such as a casing, liner, production string, and so forth defining an axial bore therethrough with a selected diameter D1. At least one polished bore receptacle (PBR) 20A, 20B, 22A, 22B is installed in the tubular member 15 to facilitate isolating a well zone 12A, 12B. A PBR 20A, 20B, 22A, 22B may be a tubular element formed or installed along the inner wall of the tubular member 15 having an axial bore with a diameter D2 less than the diameter D1 of the axial bore of the tubular member. Moreover, each PBR 20A, 20B, 22A, 22B may include a smooth and/or honed inner surface to provide a sealing surface for a sealing mechanism 30 to engage and seal to restrict access to the axial bore of the tubular member 15 below the PBR.
In one embodiment, PBRs 20A, 20B are installed only below the well zones 12A, 12B respectively. In this embodiment, the lower well zone 12B is perforated first. Then a sealing mechanism 30 is used to seal the tubular member 15 at PBR 20B. The well zone 12B is then treated via a fluid delivery device 40 on a tubing string 50. Next the upper well zone 12A is perforated. The sealing mechanism 30 is used to seal the tubular member 15 at PBR 20A and isolate well zone 12A from well zone 12B. The well zone 12A is then treated via a fluid delivery device 40.
In another embodiment, PBRs 20A, 20B are installed below the well zones 12A, 12B respectively and PBRs 22A, 22B are installed above the well zones 12A, 12B respectively. In this embodiment, the well zones 12A, 12B may both be perforated before any well zone 12A, 12B is treated. Once the well zones 12A, 12B are perforated, a straddling sealing mechanism (such as shown in FIG. 5A) may be used to isolate a particular well zone and treat the well zone via a fluid delivery device. For example, the straddling sealing mechanism may include seals for engaging PBRs 20B and 22B and isolating well zone 12B. A fluid delivery device being arranged between the seals is then used to treat the perforated well zone 12B via a tubular string 50.
FIGS. 3A-3F illustrate another embodiment of the present invention for isolating and treating a well zone. In this embodiment, a wellbore 100 having well zones 120, 130 is drilled and a tubular member 101 is fixed therein with cement 102. A PBR 110 is installed between the well zones 120, 130. The lower well zone 120 is perforated and treated thus the well zone may be referred to as a “finished well zone.” A completion tool 140 is provided having a perforating gun 142, a sealing mechanism 144, and a fluid delivery device 146. In one embodiment, the sealing mechanism 144 may be arranged above the perforating gun 142 and below the fluid delivery device 146. The completion tool 140 may be suspended in the tubular member 101 on a tubing string 150 having an axial bore therethrough. The fluid delivery device 146 may include at least one port 148 formed therein for establishing communication between the axial bore of the tubing string 150 and the annulus within the tubular member 101.
With reference to FIGS. 3A-3F, in operation, once the well zone 120 is perforated and treated, the completion tool 140 is pulled upward by the tubing string 150 (FIG. 3A). The perforating gun 142 is aligned proximate the next well zone 130 and the gun is detonated thereby perforating the well zone 130 (FIG. 3B). The completion tool 140 is then lowered until the sealing mechanism 144 engages and seals with the PBR 110 (FIG. 3C). In this arrangement, the sealing mechanism isolates the well zone 130 from the finished well zone 120 and the fluid delivery device is proximate the new target zone 130 such that a treatment fluid may be delivered to the target zone 130 via the at least one port 148 of the fluid delivery device (FIG. 3D). If circulation is required (e.g., as to circulate out sand), then fluid pressure may be increased to circulate fluid upward through the at least one port 148 of the fluid delivery device (FIG. 3E). Once the well zone 130 is finished, the completion tool 140 may be moved upward again to the next target well zone (FIG. 3F).
In other embodiments of the present invention, instead of perforating and treating one well zone at a time, all well zones may be perforated before any well zone is treated. With respect to FIGS. 4A-4B, each well zone 202, 204 of a wellbore 200 may be perforated by a perforating gun 210 on a line 220 (e.g., wireline, slickline, or tubing string) one at a time (as shown in FIG. 4A), or each well zone 202, 204 may be perforated by a perforating gun string 212 simultaneously on a line 220 (as shown in FIG. 4B). In either case, a plurality of PBRs 231, 232, 233 are installed in or formed on the casing 205 of the wellbore 200 such that a PBR is located above and below each respective well zone 202, 204.
In one embodiment, once the well zones are perforated, a well completion tool is provided to isolate and deliver a treatment fluid to each well zone. With respect to FIGS. 5A-5D, an embodiment of the well completion tool 250 includes a fluid delivery device 252 and sealing mechanisms 254, 255 arranged above and below the fluid delivery device or “straddling” the device. The well completion tool 250 is suspended in the wellbore 200 on a tubing string 260 and defines an axial bore therethrough for communication with the tubing string. The fluid delivery device 252 includes at least one port 253 formed therein for establishing hydraulic communication between the perforated well zones 202, 204 and the tubing string 260.
In operation, the well completion tool is run in the casing 205 of a wellbore 200 to a target well zone 204 (FIG. 5A). At this position, the fluid delivery device is proximate the target well zone 204 and the sealing mechanisms 254, 255 engage and seal with the PBRs 231, 230 respectively to isolate the target well zone. Once the well zone 204 is isolated, a treatment fluid may be pumped or otherwise delivered down the tubing string 260 and into the formation of the target well zone 204 via the port 253 of the fluid delivery device 252 (FIG. 5B). After treating the well zone 204, the well completion tool 250 may be lifted upward to break the seals between the sealing mechanisms 254, 255 and the PBRs 231, 230 respectively. Next, hydraulic pressure in the well completion tool 250 may be increased to circulate out any excess sand from the annulus between the tool and the casing 205 (FIG. 5C). The tool 250 may then be lifted further upwards to the next target well zone 202 where the sealing mechanisms 254, 255 engage and seal with PBRs 232, 231 respectively to isolate the well zone 202 for treatment.
In an alternative embodiment of the present invention, a well completion tool is provided to deliver treatment fluid to isolated well zones, each of which have been perforated as shown in FIGS. 4A, 4B. In this embodiment, a well completion tool 270 having: (1) an inner string 272 and outer string 274 arranged concentrically to define a first annulus within the inner string 272, a second annulus within the outer string 274 but outside the inner string 272, and a third annulus within the casing 205 and outside the outer string 274; (2) a diverter tool 280 connected to the lower end of the inner string 272 and having at least one port 282 formed therein for establishing hydraulic communication between the axial bore of the inner string 272 and the annulus inside the casing 205; and (3) a sealing mechanism 276 formed on the outer surface of the diverter tool 280 and a plurality of sealing mechanisms 277, 278 formed on the outer surface of the outer string 274 to engage and seal with PBRs 230, 231, 232 in the casing 205. The lower end of the outer string 274 is open to the annulus within the casing 205. This embodiment provides circulation to a target well zone 204 via both the annulus between the inner string 272 and outer string 274 and the annulus within the inner string 272 without flowing past open formations of well zone 202 (or any other well zone above or below the target well zone 204 for that matter).
Still with respect to FIG. 6, in operation, the well completion tool 270 is run in a casing 205 of a wellbore 200 to a target formation 204. In this position, the diverter tool 280 is proximate the target well zone 204 and the sealing mechanisms 276, 277, 278 engage and seal with the PBRs 230, 231, 232 thus isolating well zone 204 from other zones. A treating fluid may then be delivered through the inner string 272 to the formation of the target well zone 204 via the port 282 of the diverter tool 280. Alternatively, a treatment fluid may be delivered via the outer string 274 alone or both the inner string 272 and the outer string 274 simultaneously. Furthermore, the outer string 274 may be used to circulate excess sand once the well completion tool 270 is pulled out of engagement with the PBRs 276, 277, 278 and moved to another target well zone. Alternatively, circulation may be achieved through the inner string 272 alone or both the inner string 272 and the outer string 274 simultaneously.
With respect to FIGS. 7A-7D, yet another embodiment of the present invention is provided for selectively perforating and isolating a target well zone for delivery of a treatment fluid to the underlying formation. FIG. 7A illustrates a casing 402 being fixed to a wellbore 400 by cement 404. The wellbore 400 intersects a plurality of well zones 410, 412 and the casing 402 includes a plurality of PBRs 420, 422 arranged below the well zones 410, 412 respectively. Transmitters 430, 432 are arranged proximate to the well zones 410, 412 respectively. In one embodiment, the transmitters 430, 432 are attached to the PBRs 420, 422. In other embodiments, the transmitters 430, 432 may be embedded in the cement 404 or attached to the casing 402. Each transmitter 430, 432 emits a particular or unique signal (e.g., a radio frequency “RF” signal, an acoustic signal, a radioactive signal, a magnetic signal, or other signal). A dart 440 having a sealing mechanism 442, perforating gun 444, and receiver 446 is provided. Certain embodiments of the dart 440 may include a centralizer 448 (e.g., guiding fins) for maintaining the alignment of the dart being pumped downhole. Other embodiments of the dart 440 may include a fishing profile 450 such that the dart may be retrieved after the treatment fluid is delivered and before the well is produced. The sealing mechanism 442 of the dart is moveable between a collapsed position wherein the dart 440 does not engage and seal with a PBR 420, 422 (as shown in FIGS. 7A, 7D) and a biased position wherein (as shown in FIGS. 7B, 7C). The receiver 446 controls (e.g., by means of a controller, PLC, or other similar device) the position of the sealing mechanism 442 based on detection of a signal from a transmitter 430, 432.
Still with respect to FIGS. 7A-7D, in operation, the dart 440 is initially run downhole with the sealing mechanism 442 collapsed and is programmed to bias radially outward upon coming into proximity of a predetermined target well zone 432. Particularly, the receiver 446 of the dart 440 is programmed to take an action upon receiving the particular signal being emitted by transmitter 432. Thus, no action is taken as the dart 440 passes transmitter 430, which is emitting a different signal (FIG. 7A). Once the receiver 446 of the dart 440 is proximate to the transmitter 432, the sealing mechanism 442 moves radially outward into the biased position (FIG. 7B). The biased sealing mechanism 442 then engages and seals with the PBR 422. The perforating gun 444 is then in a position proximate the target well zone 412. In some embodiments, the perforating gun 444 is set to detonate after a predetermined delay once the sealing mechanism 442 is actuated to bias radially outwards as by a counter or timer. In other embodiments, the perforating gun 444 may be actuated from the surface to detonate via pressure pulses, pressure changes, or other signaling in the wellbore. Either way, the perforating gun 444 detonates to penetrate the casing, cement, and the underlying formation of the well zone 412 (FIG. 7C). Once the target well zone 412 is perforated, a treatment fluid may be delivered down the annulus of the casing 402 to the target well zone 412. The sealing mechanism 442 of the dart 440 effectively seals and isolates the target well zone 412 from any previously perforated and treated well zones below. After treatment of the target well zone 412, the sealing mechanism 442 moves back into the collapsed position and the dart 440 is freed from sealing engagement with the PBR 422. The dart 440 may then be pumped to the bottom of the wellbore 400 (FIG. 7D). Another dart (not shown) keyed to the frequency of the signal emitted by transmitter 430 may be used to seal with PBR 420, perforate, and treat the next target well zone 410. In some embodiments, the darts may include a fishing profile such that the darts may be retrieved after zonal operations are complete (e.g., isolate, perforate, and treat) and before the well is produced.
In some alternative embodiments of the present invention using PBRs to achieve zonal isolation in a wellbore, an anchoring device may be installed proximate to each PBR for the purpose of providing a positive location for depth control. The anchoring device may also support the weight of any dart or fluid delivery tools or applied forces produced from differential pressure across the seals of the PBRs and sealing mechanisms.
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.
Patent Application
20060144590
