FIELD OF THE INVENTION

The present invention relates to multi-stage liners used in open hole or cased completions for injection of fluids at successive contiguous locations along a wellbore to create multiple fractures in a hydrocarbon zone along the wellbore.

BACKGROUND OF THE INVENTION

This background and documents mentioned below are provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention, and in particular allowing the reader to understand advantages of the invention over devices and methods known to the inventor, but not necessarily public. No admission is necessarily intended, nor should be construed as admitting, that any of the following documents or methods known to the inventor constitute legally citable prior art against the present invention.

After an oil or gas well is drilled within an underground hydrocarbon formation, the zones of interest need to be completed, namely conditioned typically by a fracking operation, in order to most quickly and to the greatest extent possible produce oil and/or gas from each particular zone. If the zone of interest requires a type of fracture stimulation, including but not limited to acid fracture or propped fracture, the zone of interest will be isolated to focus the fracture on the particular zone, and to prevent fracture in other zones which may not be desired.

Liner systems can be used prior to conducting the fracture stimulation and can be run in either open hole or cased hole applications.

In the stimulation of directional and horizontal wells, it can be desirable to treat multiple stages in a single zone, known as a cluster, with a single fracture stimulation. It can also be desirable to treat more than one zone with a single fracture stimulation to save time and expense associated with multiple treatments and time spent running tubing and tools in and out of the wellbore.

Various downhole tools and systems have been used to stimulate wells by permitting treatment/fracturing in multiple contiguous regions within a single zone. Many of such tools and systems require components within the bore of the liner at each valve which disadvantageously restricts flow of fluid through the liner during fracture pumping operations, and also, to the extent such systems or remnants thereof remain, similarly restrict production of hydrocarbons. Due to such flow restrictions, pressure drops occur, which result in less efficient operations as there is pressure loss incurred prior to the fracture fluid contacting the zone. Ideally, less pressure drop is desired to conduct a fracture stimulation more efficiently in each stage and in addition. In addition, such tools and methods require milling out of such components at each valve location prior to switching to production flow from the hydrocarbon bearing zones. It is desirous to have fewer materials/components to mill out within the bore liner immediately prior to commencing production from the hydrocarbon bearing zones.

Numerous patents and pending patent applications exist related to apparatus and systems for opening a plurality of ports in a liner within a wellbore at multiple contiguous locations therealong, to thereby permit injection of a fluid from such liner into a hydrocarbon formation, typically for the purpose of fracturing the formation at such locations.

For example, U.S. Pat. No. 8,215,411 teaches a plurality of opening sleeve/cluster valves along a liner for wellbore treatment, and utilizes a ball member or plug to open a sleeve at each valve thereby allowing fluid communication between the bore and a port in the sleeve's housing. This invention requires, however, a ball seat corresponding to each sleeve in a cluster valve, potentially restricting flow. The presence of a ball seat at each valve to be opened, due to the resulting bore restriction at each valve sleeve, creates a significant pressure drop across the cluster valve assembly.

U.S. Pat. No. 8,395,879 teaches a hydrostatically powered sliding sleeve. Again, such configuration utilizes a single ball, but each sliding sleeve configuration requires its own ball seat.

U.S. Pat. No. 4,893,678 discloses a multiple-set downhole tool and method that utilizes a single ball. Again, each valve requires a seat which is integral with a sliding sleeve, and which remains with each valve/port. When the sleeve/seat is forced by the ball to slide and thereby open the port, collet fingers may then move radially outwardly, disengaging the ball and allowing the ball to further travel downhole to actuate (open) further ports.

US Patent Application Publication No. 2014/0102709 discloses a tool and method for fracturing a wellbore that uses a single ball, each valve with a deformable ball seat. Again, each valve has a valve seat which remains with each valve/port.

Other patents and published applications avoid the problem of each valve/port having a ball seat which remains with each valve, and provide a dart or ball member which actuates a number of valves/ports. However, such designs are not without their own unique drawbacks.

For example, US 2013/0068484 published Mar. 21, 2013, inter alia in FIG. 6 thereof, (and likewise to same effect US 2004/0118564 published Jun. 24, 2004, likewise in FIG. 6 thereof) teaches an axially movable sliding sleeve 322 which is capable of actuating (i.e. opening) a number of downhole port sleeves 325a, 325b to thereby open corresponding respective downhole ports 317a, 317a′ which are normally covered by port sleeve 325a, and similarly subsequently open respective downhole ports 317b, 317b′ normally covered by port sleeve 325b. Sliding sleeve 322 is mounted by a shear pin 350 in the tubing string. Plug/ball 324 is inserted in the tubing, and uphole fluid pressure applied thereto cause plug 324 to travel downwardly in the in the string and abut sliding sleeve 322, further causing shear pin 350 to shear and thus sleeve 322 to then be driven downhole. Spring-biased dogs 351 on outer periphery of sliding sleeve 322 then engage inner profile 353a on sliding sleeve 325a and cause sleeve 325a (due to fluid pressure acting on plug 324) to move downhole thereby opening ports 317a, 317a′. As noted in paragraph [0071] therein, continued application of fluid pressure causes dogs 351 to collapse, thereby releasing sleeve 322 from engagement with inner profile 353a on sliding sleeve 325, and allowing sleeve 322 to further travel downhole and actuate (i.e. open) further sleeves in like manner. Although not expressly mentioned nor shown in US 2013/0068484, seals are necessary around dogs 351 in order to allow creation of a pressure differential when such continued application of fluid pressure is applied, in order to cause collapse of such dogs to allow disengagement with a first sleeve and allow the dart to thereafter further travel downhole for subsequent actuation of additional downhole sleeves and ports. The necessity for seals around dogs 351 necessarily introduces added mechanical complexity and the possibility of inability to release sleeve 322 from engagement if such seals were to leak due to the then-inability to create a pressure differential.

WO 2013/048810 entitled “Multizone Treatment System” published Apr. 4, 2013 teaches a system and method for successively opening flow control devises (which may be sliding sleeves) in a tubing string along a length thereof, commencing with a most downhole valve and opening a sleeve at such location, and by insertion of additional darts progressing successively upwardly in the tubing string to open further uphole sleeves. The tubing string is provided with a plurality of spaced apart flow control devices, such as sliding sleeves, each having an annulary-located recess therein with a unique profile relative to other flow control devices. A first dart, having an engagement feature sized to correspond with a selected annulary-located recess of a particular most-downhole flow control device, is injected, and such dart passes to actuate the flow control device to allow it to open a port. The process is progressively repeated for additional uphole flow control devices by injecting additional darts, having corresponding features to engage a selected flow control device. The darts are then drilled out to allow production from the tubing. Disadvantageously, only one dart can open one port, and thus a plurality of contiguously spaced ports are not capable of being opened by a single dart using such apparatus/method, thereby rendering such system/method time consuming.

CA 2,842,568 entitled “Apparatus and Method for Perforating a Wellbore Casing, and Method and Apparatus for Fracturing a Formation” published May 29, 2014 teaches inter alia dart members similar to the dart of WO 2013/048810, each dart having a protruding spring-biased profile uniquely sized to engage a similarly-sized annular recess on a plurality of downhole sliding sleeves, and thereby open sliding sleeve, with further means being provided on each of such sliding sleeves to allow the single dart member to further travel downhole and open additional sleeves having similar-sized annular recesses. No collet sleeve is provided, and a non-beveled (non-chamfered) surface on the annular recess of the most downhole sleeve is used to retain the dart from travelling further downhole. Disadvantageously, in comparison to the system as hereinafter described, the configuration of the dart, namely having a spring-biased profile and a cup seal thereon, essentially requires the dart to be virtually solid and thereby permanent obstruction to the wellbore once opening the last of a series of slidable sleeves. If additional uphole sleeves are desired to be actuated using a second dart (having a narrower protruding spring-biased profile than the first dart used), the first dart must be installed using a locator tool and thereafter retrieved, after actuating a plurality of sleeves and associated ports using such tool, as shown inFIGS. 9A-9D. Such a system involves use of extensive equipment from surface and the need of a bypass port that need by opened and closed to allow effective operation including insertion and withdrawal of the locator tool. These steps and features complicate the operation of such prior art system and add to expense and time.

A need exists for an effective and simpler system which does away with tools from surface for opening production tubing for use after actuation of such ports.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an additional alternative system to existing systems and methods for opening contiguously spaced-apart ports located along a tubing within a wellbore to allow injection of fluid into a hydrocarbon formation.

It is a further object of the present invention, in certain embodiments thereof, to provide a system which may selectively open groups of continuous ports along a tubing liner separately, to allow separate and discrete fracking of various differently-located hydrocarbon zones which may exist along a length of a tubing liner within a wellbore in a hydrocarbon formation.

It is a still further object of the present invention to provide a system which can do each of the above, yet nevertheless provide a minimum restriction to the bore of the tubing liner to thereby maximize production and flow rate of hydrocarbon therefrom.

It is a still further object of certain embodiments of the present invention to be able to accomplish each of the foregoing objects, yet nonetheless not have to, after the completion of the opening of the ports and the fracking process, insert a reamer to ream out any remaining flow obstructions within the tubing liner, and thereby avoid additional steps prior to being able to produce hydrocarbons from a wellbore.

Accordingly, in a first broad embodiment, the present invention provides for a system for successively uncovering a plurality of contiguous spaced-apart ports along a wellbore, comprising:(i) a tubular liner having a bore, further comprising:(a) a plurality of said spaced-apart ports longitudinally and contiguously spaced along said tubular liner;(b) a corresponding plurality of cylindrical sliding sleeve members, each longitudinally slidable within said bore, each configured in an initial closed position to overlap a corresponding of said ports, and when slidably moved to an open position to uncover said corresponding port, each of said sliding sleeve members having an interior circumferential groove therein;(c) a shear member, initially securing said slidable sleeve members in said initial closed position, and sheareable when a force is applied to a respective of said slidable sleeve members;(ii) an actuation member positioned within said bore, comprising:(a) a cylindrical hollow collet sleeve, having a radially-outwardly biased and protruding protuberance, said protuberance configured to successively matingly engage each of said respective interior circumferential grooves on said sliding sleeve members, wherein said protuberance is of a substantially equal or lesser width than a width of said circumferential grooves on each of said sliding sleeve members, wherein said protuberance may be inwardly compressed to allow said collet sleeve and protuberance thereon to become disengaged from mating engagement in said circumferential groove;(b) a plug member, situated within said collet sleeve and when in a first position situated at an uphole end thereof, which at least for a limited time together with said collet sleeve substantially obstructs passage of fluid within said bore when said collet sleeve and plug member are together situated in said bore;(c) a shear pin, releasably securing said plug member to an uphole end of said collet sleeve, shearable when a force is applied to said plug member to cause said plug member to move downhole in said collet sleeve to a second position therein preventing said protuberance from thereafter being forcibly inwardly compressed and thereby maintaining said protuberance in mating engagement with said circumferential groove;

wherein fluid pressure applied to an uphole end of said actuation member causes said actuation member to move downhole and successively engage said circumferential groove in each of said sliding sleeve members and move said sliding sleeve members downhole so as to thereby uncover each of said plurality of ports;

wherein fluid pressure required to shear said shear members in all of said slidable sleeve members save and except for a most-downhole of said slidable sleeve members, is less than fluid pressure required to shear said shear pins securing said plug member to said uphole end of said collet sleeve; and

wherein said plug member, when opening a most-downhole sliding sleeve member, shears said shear pin therein and moves downhole in said collet sleeve from said first position therein to said second position thereby preventing said protuberance from being inwardly compressed.

In a further refinement, the tubing liner is further provided with burst plates covering each of said ports, said burst plates adapted to rupture and allow fluid communication from said bore to said port upon a fluid pressure in said bore being higher than and exceeding the fluid pressure necessary to:(i) cause said plug member and collet sleeve to shear said shear member; and(ii) cause said plug member to shear said shear pin and move to said plug member to said second position.

In a still further refinement, the plug member is dissolvable, and after moving to said second position and after a period of time being exposed to fluid within said bore, becomes dissolved. Such advantageously avoids having to insert a downhole reamer within the tubing liner, once fluid injection into the formation via the opened ports has been completed, in order to ready the tubing liner for production so as to allow hydrocarbons from locations further downhole to flow uphole to surface.

In a further refinement of the aforementioned system, means is provided to lock the sliding sleeves in the open position once such sliding sleeves have been moved by the plug and collet sleeve to the open position uncovering such ports. Thus in a preferred embodiment, a snap ring member is provided with each of said plurality of sliding sleeve members, which snap ring member locks each sliding sleeve member in said open position when said sliding sleeve member is moved to said open position. Other similar means of locking each sliding sleeve in an open position will now occur to persons of skill in the art, and are likewise alternatively contemplated for use in the system of the present invention to lock the sliding sleeves in the open position.

In a still further refinement, the plug member upon movement to said second position prevents said protuberance from being inwardly compressed, and said actuation member is further prevented along from further movement downhole.

In a further preferred embodiment, a plurality of actuation members, each comprised of a collet sleeve having a protuberance thereon of a different with, are utilized to uncover a plurality of groups of discrete/separate spaced apart ports, wherein each of the groups of ports in the liner are positioned in different zones of the formation. Such allows injection of fluid in separate zones of the wellbore, at a time and in a sequence determined by the completions engineer who controlling the fracking/completion process to be most optimal for allowing greatest recovery from the well.

Accordingly, in such further preferred embodiment of the system of the present invention, a system for successively uncovering at least two separate groups of contiguous spaced-apart ports along a wellbore is provided, comprising:(i) a tubular liner having a bore, further comprising:(a) a plurality of first spaced-apart ports longitudinally spaced along said tubular liner;(b) a corresponding plurality of first cylindrical sliding sleeve members, each longitudinally slidable within said bore, each configured in an initial closed position to overlap a corresponding of said first ports and when slidably moved to an open position to not overlap said first port, each of said sliding sleeve members having an interior circumferential groove therein of a first width;(c) a plurality of said second spaced-apart ports longitudinally and contiguously spaced along said tubular liner, situated in said tubular liner downhole from said first ports;(d) a corresponding plurality of second cylindrical sliding sleeve members, each longitudinally slidable within said bore, each configured in an initial closed position to overlap a corresponding of said second ports and when slidably moved to an open position to not overlap said corresponding second port, each of said second sliding sleeve members having an interior circumferential groove therein of a second width, wherein said second width is greater than said first width;(e) shear members, respectively securing said first and second slidable sleeve members in said initial closed position, and shearable when a force is applied to a respective of said first and second slidable sleeve members;(ii) a first actuation member positioned within said bore, comprising:(a) a cylindrical hollow collet sleeve, having a plurality of elongate longitudinally extending finger members thereon, said finger members having thereon a radially-outwardly protruding protuberance, said protuberance configured to successively matingly engage said respective interior circumferential groove on each of said second sliding sleeve members, wherein said protuberance is of a width substantially equal to said second width but greater than said first width, wherein said protuberance may upon fluid pressure being applied to an uphole side of said first actuation member be inwardly compressed to allow said collet sleeve and protuberance thereon to become disengaged from mating engagement in said circumferential groove in each of said second sliding sleeve members;(b) a plug member, situated within said collet sleeve and when in a first position situated at an uphole end of said collet sleeve, which at least for a limited time together with said collet sleeve substantially obstructs passage of fluid within said bore when said collet sleeve and plug member are together situated in said bore;(c) a shear pin, releasably securing said plug member to an uphole end of said collet sleeve, shearable when a force is applied to said plug member to cause said plug member to move downhole in said collet sleeve to a second position therein preventing said finger members from thereafter being forcibly inwardly compressed and thereby maintaining said protuberance in mating engagement with said circumferential groove;

wherein fluid pressure applied to an uphole end of said first actuation member causes said first actuation member to move downhole and cause said collet sleeve thereof to successively engage said second circumferential groove in each of said second slidable sleeve members and move each of said second sliding sleeve members downhole so as to thereby uncover each of said plurality of second ports;

wherein fluid pressure required to shear said shear members in all of said second slidable sleeve members save and except for a most-downhole of said slidable sleeve members, is less than fluid pressure required to shear said shear pins securing said plug member to said uphole end of said collet sleeve; and

wherein said plug member in said first actuation member, when opening a most-downhole second sliding sleeve member, shears said shear pin therein and moves downhole in said collet sleeve from said first position therein to said second position thereby preventing said protuberance from being inwardly compressed;

said system further comprising:(iii) a second actuation member positioned within said bore, comprising:(a) a cylindrical hollow collet sleeve, having a plurality of elongate longitudinally extending finger members thereon, said finger members having thereon a radially-outwardly protruding protuberance, said protuberance configured to successively matingly engage said respective interior circumferential groove on each of said first sliding sleeve members, wherein said protuberance is of a width substantially equal to said first width, but less than said second width, wherein said protuberance may be inwardly compressed to allow said collet sleeve and protuberance thereon to become disengaged from mating engagement in said first circumferential groove in each of said first sliding sleeve members;(b) a plug member, situated within said collet sleeve and when in a first position situated at an uphole end of said thereof, which at least for a limited time together with said collet sleeve substantially obstructs passage of fluid within said bore when said collet sleeve and plug member are together situated in said bore;(c) a shear pin, releasably securing said plug member to an uphole end of said collet sleeve, shearable when a force is applied to said plug member to cause said plug member to move downhole in said collet sleeve to a second position therein preventing said finger members from thereafter being forcibly inwardly compressed and thereby maintaining said protuberance in mating engagement with said circumferential groove;

wherein fluid pressure applied to an uphole end of said second actuation member causes said second actuation member to move downhole and said collet sleeve thereof successively engage said circumferential grooves in each of said first slidable sleeve members and move each of said first sliding sleeve members downhole so as to thereby uncover each of said plurality of first ports; and

wherein fluid pressure required to shear said shear members in all of said first slidable sleeve members save and except for a most-downhole of said first slidable sleeve members, is less than fluid pressure required to shear said shear pins securing said plug member to said uphole end of said collet sleeve.

In a further embodiment the plug member in said second actuation member, when opening a most-downhole sliding sleeve member, shears said shear pin therein and moves downhole in said collet sleeve from said first position therein to said second position thereby preventing said protuberance from being inwardly compressed.

In a still further embodiment, the plug member in the second actuation member and/or first actuation member may be dissolvable by a fluid that may be injected downhole.

In a further refinement burst plates may likewise be provided covering each of said first and second ports, said burst plates adapted to rupture and allow fluid communication from said bore to said port only upon a fluid pressure in said bore exceeding:

(i) the fluid pressure necessary to cause said plug member in each of said first and second actuation member and said associated collet sleeve to shear said shear member; and

(ii) the fluid pressure necessary to cause said plug member in each of said first and second actuation member to shear said shear pin and move to said plug member to said second position in each collet sleeve.

In such manner, as fracking operations are typically conduced commencing with a most downhole/furthest extremity of the wellbore, the wellbore may be progressively fracked in each zone, commencing from the most downhole/furthest extremity of the wellbore.

In a further embodiment of the present invention, the invention provides a system using at least two actuating (slidable dart) members, each of said at least two actuating members having a differently-dimensioned (or differently-configured) protuberance profile, so that the protuberance profile on a collet sleeve of each of the actuation members is unique. A first of such actuation members having such a unique protuberance profile successively matingly engages at least one sliding sleeve member, and preferably successively matingly engages a first group of sliding sleeve members, all having a similarly configured inner circumferential groove or series of grooves thereon which matingly engage the protuberance profile on the actuation member, to allow the actuation member to thereby uncover/open a series of ports along a hollow tubular member. A plug member, typically a spherical ball pumped down the tubular liner, obstructs the flow of fluid through each actuation member, thereby providing a downhole motive force on each of said at least two actuation members. After opening, by a first of the at least two actuation members, at least one port and preferably a group of ports, a second actuation member having a differently configured or dimensioned profile, can be pumped downhole to then similarly move and thereby open a second group of sliding sleeve members, so as to allow opening at a different time of a second group of ports along a tubular liner.

As many groups of ports may be individually opened as there are actuation members having different configured/dimensioned protuberance profiles.

In such further embodiment, it is not necessary that the plug member, typically in this embodiment a spherical ball, be affixed via shear pins to the collet sleeve of the actuation member.

Accordingly, in a first broad embodiment of such further embodiment a system for successively uncovering at least two separate groups of contiguous spaced-apart ports along a pipe inserted in a wellbore is provided. Such system comprises:(i) a tubular liner having a bore, further comprising:(a) a plurality of said spaced-apart ports longitudinally and contiguously spaced along said tubular liner;(b) a corresponding plurality of cylindrical sliding sleeve members, each of said sleeve members associated with a respective of said plurality of spaced-apart ports, each sliding sleeve member longitudinally slidable within said bore and configured in an initial closed position to overlap a corresponding of said ports, and when slidably moved to an open position to uncover a corresponding of said ports, each of said sliding sleeve members having an interior circumferential groove, a width of said interior circumferential groove in said sliding sleeve members associated with a first group of contiguous spaced-apart ports being different than a width of said interior circumferential grooves in said sliding sleeve members associated with a second group of contiguous spaced-apart ports;(c) a shear member, initially securing said slidable sleeve members in said initial closed position, and sheareable when a force is applied to a respective of said slidable sleeve members;(ii) a first actuation member positioned within said bore, comprising:(a) a cylindrical hollow collet sleeve, having a radially-outwardly biased and protruding profile, said profile configured to matingly engage said interior cylindrical grooves in said sliding sleeves associated with a first of said at least two groups of ports, but not matingly engage said interior cylindrical grooves associated with sliding sleeve members which initially cover said second group of ports;(b) a dissolvable plug member, dimensioned so as to be positionable and remain lodged within said collet sleeve of said first actuation member at an uphole end thereof, which at least for a limited time when not dissolved together with said collet sleeve substantially obstruct passage of a fluid within said bore when said collet sleeve and dissolvable plug member are together situated in said bore, and becomes dissolved after said fluid is injected down said wellbore;wherein fluid pressure applied to an uphole end of said first actuation member causes said first actuation member to move downhole and engage said circumferential groove in said at least one sliding sleeve member associated with said first group of ports, and not engage said circumferential grooves of a different width in remaining cylindrical sliding sleeve members associated with said second group of ports, and move each sliding sleeve member associated with said first group of ports downhole so as to thereby uncover said ports in said first group of ports; and(iii) a second actuation member positioned within said bore, comprising:(a) a cylindrical hollow collet sleeve, having a radially-outwardly biased and protruding profile, said profile configured to matingly engage said interior cylindrical grooves in said sliding sleeves associated with a second of said at least two groups of ports;(b) a dissolvable plug member, dimensioned so as to be positionable and remain lodged within said collet sleeve of said second actuation member at an uphole end thereof, which at least for a limited time when not dissolved together with said collet sleeve substantially obstructs passage of a fluid within said bore when said collet sleeve and dissolvable plug member are together situated in said bore, and becomes dissolved after said fluid is injected down said tubular liner;wherein fluid pressure applied to an uphole end of said dissolvable plug member upon a fluid being injected down said tubular liner, causes said second actuation member to move downhole and engage said circumferential groove in said at least one sliding sleeve members associated with said second group of ports, and move each sliding sleeve member associated with said second group of ports downhole so as to thereby uncover said ports in said second group of ports.

As noted above, such system is particularly adapted for successively uncovering at least two separate groups of contiguous spaced-apart ports along a tubular liner. Preferably, the interior grooves and/or said resiliently outwardly biased profile on said first and/or second actuation members are provided with a chamfer so as to permit, after said profile on said first and second actuation members has matingly engaged a respective of said interior circumferential grooves, said profile on said first and/or second actuation member to be released from said mating engagement therein upon further fluid pressure being applied uphole to said plug member, so as to allow the first and/or second actuation member to move further downhole and actuate (i.e. open) additional desired ports along such tubing liner.

In a preferred refinement of such further embodiment, each of sliding sleeve members at a lowermost (downhole) end thereof, possess radially-outwardly biased and extending tab members which engage an aperture in said tubing liner when a respective of said sliding sleeve members is moved to uncover an associated port, which tab members when engaged in said aperture prevent respective of said sliding sleeve members from moving uphole to thereby close an associated port.

In a further refinement, said first and second actuation members are provided, at a downhole end thereof, with an annular ring of a diameter substantially equal to the diameter of the sliding sleeve members, having a chamfer thereon to assist said actuation member in moving downhole in the tubular liner.

In a further refinement, one or both of said first or second actuation members may be dissolvable upon being exposed for a period of time to said fluid. Such a configuration advantageously eliminates, after the opening of ports along the tubular liner, any remaining restriction in the diameter of the tubing liner, and allows as much cross-sectional area of the tubing liner to be utilized for producing oil collected in such tubing liner after fracking via the opened ports. Horsepower pumping requirements, due to the reduced restrictions inherent in the tubing liner when producing, are thereby reduced to the maximum possible for a given tubing liner diameter.

In a further embodiment of the present invention, the invention relates to a method for successively uncovering a plurality of spaced-apart ports along a hollow tubular liner. Such method comprises the steps of:

(i) injecting a first actuation member having a profile thereon of a first width down said tubular liner having a plurality of sliding sleeve members respectively covering a corresponding plurality of said spaced-apart ports along said tubular liner;

(ii) causing said profile on said first actuation member to engage an interior circumferential groove on a lowermost of said sliding sleeve members, and upon application of fluid pressure uphole of said first actuation member, causing said sliding sleeve member to move downhole and thereby uncover an associated of said ports in said tubular liner;

(iii) allowing fluid in said tubular liner to dissolve a plug in said first actuation member so as to allow flow of fluid in said tubular liner through said first actuation member;

(iv) injecting a further actuation member down said tubular liner having a profile thereon of a lesser width;

(v) causing said profile of said lesser width thereon to engage an interior circumferential groove on a sliding sleeve member uphole of said lowermost sliding sleeve member, and upon application of fluid pressure uphole of said further actuation member, causing said uphole sliding sleeve member to move downhole and thereby uncover an additional associated of said ports in said tubular liner;

(vi) allowing fluid in said tubular liner to dissolve a plug in said further actuation member so as to allow flow of fluid in said tubular liner through said further actuation member; and

(vii) repeating steps (iv)-(vi) until all of said plurality of spaced-apart ports along said tubular liner have been opened.

The above summary of the invention does not necessarily describe all features of the invention. For a complete description of the invention, reference is to further be had to the drawings and the detailed description of some preferred embodiments, read together with the claims.

