GB2513574A

GB2513574A - Wellbore Completion Method

Info

Publication number: GB2513574A
Application number: GB1307701.1A
Authority: GB
Inventors: Michael Stafford Cowling; Sara Sparre Kofoed; Rasmus Lystbaek Petersen
Original assignee: Maersk Olie og Gas AS
Current assignee: Total E&P Danmark AS
Priority date: 2013-04-29
Filing date: 2013-04-29
Publication date: 2014-11-05
Also published as: GB201307701D0; DK201470817A1; WO2014177587A3; WO2014177587A2

Abstract

A method for completing a well comprises forming a lateral wellbore 20 extending laterally from a primary wellbore 12 so as to define a junction between the primary wellbore and the lateral wellbore, preventing fluid flow between the lateral wellbore and the primary wellbore, and then permitting fluid flow between the lateral wellbore and the primary wellbore. The method may further comprise installing completion infrastructure 70 in the primary wellbore in the region of the junction between the step of preventing fluid flow between the lateral wellbore and the primary wellbore and the step of permitting fluid flow between the lateral wellbore and the primary wellbore. The completion assembly may be an isolator and may include a timer, a rupture disc, glass disc, flapper valve or ball valve. Also disclosed is an isolator and a well system.

Description

WELLBORE COMPLETION METHOD

FIELD

The present invention relates to a method for well completion and, in particular, though not exclusively, to a method for completion of an oil or gas well for the extraction of hydrocarbons from a subterranean formation.

BACKGROUND

In the oil and gas exploration and production industries wellbores are drilled from surface to intercept subterranean formations or reservoirs. These wellbores may be used to produce fluids, such as oil and gas, from a subterranean reservoir to surface. Further, these wellbores may be used to inject a fluid, such as water or gas, into a subterranean region, for example for disposal, to assist in recovery of a further fluid to surface, and the like.

Wellbores are typically formed in stages, with a first section drilled with a drill bit mounted on the end of a drill string, and the drilled section then lined with casing which is cemented in place for sealing and support. Following this a drill string with a smaller diameter drill bit is run through the cased first section to advance the bore, with the further drilled section also lined with casing. This process is repeated until the bore intercepts the target formation or reservoir, with the reservoir section of the bore typically being lined with a reservoir liner, and cemented in place, and/or sealed via liner packers. As each new bore section is drilled with a drill bit of reducing diameter to permit passage of the drill string and casing/liner through the previous cased section, the diameter of the wellbore decreases with bore depth. In some cases the reservoir liner may define a diameter of, for example, 178mm (7").

During each drilling stage a drilling fluid, known as drilling mud, is circulated through the bore. This drilling mud has multiple functions, such as to lubricate and cool the drill bit, to carry drill cuttings back to surface, and to control the hydrostatic pressure within the bore and establish a desired balance between the bore pressure and surrounding reservoir pressure to minimise the risk of inflow from the formation to the bore and/or outflow from the bore to the formation during this bore forming stage.

Once the reservoir section is lined, this may be perforated at various locations along its length to establish fluid communication between the reservoir and the wellbore. Where the wellbore is required to produce reservoir fluids to surface, a production completion is installed, which may include a production tubing string with multiple in-flow ports along its surface to facilitate entry of reservoir fluids to be communicated to surface.

In many instances efficient production rates can only be achieved if the reservoir is first stimulated. Many stimulating techniques are known, such as fracturing and acid stimulation, which usually function to effectively increase the effective permeability of the reservoir, especially in the near wellbore region which may have suffered damage during drilling. A Perforate, Stimulate and Isolate (PSI) completion system is a known completion system in which individual sealed zones within the perforated liner are established by use of a number of packers mounted on the production string. The production string includes sliding sleeves which are opened to permit outflow of a stimulating fluid, such as an acid, fracturing fluid and the like, into each isolated zone and ultimately into the reservoir for stimulation thereof via the liner perforations. The sliding sleeves may selectively permit the inflow of fluids such as hydrocarbon fluids into the liner to surface. The sliding sleeves are typically operated by coiled tubing extended from surface, and as such the total length of this type of completion is restricted to the reach of the coiled tubing.

To maximise the interface area between the wellbore and the reservoir, and therefore maximise recovery rates, it is common practice to form extended lateral or horizontal wellbore sections. For example, such lateral wellbores are extensively used in the Dan/Halfdan oil accumulation, offshore Denmark. However, the extent of such lateral wells may be limited by the desired or required completion techniques. For example, the PSI completion system, as noted above, is limited by the maximum reach of coiled tubing or any other known mechanical way of sliding the sleeves. Also, in some circumstances, although a bore may be drilled to a significant depth it may not be possible to line or case the bottom part of such a bore with a conventional cemented reservoir liner, and subsequently perforate this to establish communication with the reservoir.

It has been proposed in the art to leave extended reach sections of a bore unlined or open, and permit communication of reservoir fluids directly through the bore/reservoir interface region. However, it is extremely difficult to stimulate such open hole sections, for example due to the complexity and often the inability to run and install completion equipment at such depths. Also, as noted above, the process of drilling the bore often has a detrimental effect on the bore/reservoir interface region, causing damage in the near-wellbore region, resulting in a reduction in porosity and permeability and thus restricting inflow of reservoir fluids. This damage or reduction in porosity and permeability is often termed the wellbore skin, and must be addressed to ensure efficient and maximum production rates are achieved.

For example, the drilling fluid or mud used during the drilling process may form a layer or coating on the surface of the bore, called mud or filter cake, which presents a restriction to inflow from the reservoir. This mud cake must be removed to improve the rate of inflow from the reservoir, and again difficulties exist due to the depths involved.

The present applicant has developed a technique for use in stimulating extended reach reservoir sections, which is disclosed in ER 1 184 537 and in SPE paper 78318 entitled "Controlled Acid Jet (CAJ) Technique for Effective Single Operation Stimulation of 14,000+ ft Long Reservoir Sections". The disclosure of each of these documents is incorporated herein by reference. This technique involves running a liner, called a Controlled Acid Jet (CAJ) liner, into a drilled bore which extends beyond an existing lined upper bore section, wherein the CAJ liner is sealed against a liner in the upper bore section. The CAJ liner includes a number of pre-drilled holes extending through its wall, which permit an acid pumped from surface to exit the CAJ liner and into the annulus between the CAIJ liner and the bore wall. This acid functions to break down the mud cake and then flows into the reservoir to stimulate the reservoir. Such techniques are based on a principle of limited entry into, and the simultaneous stimulation of, the extended reach reservoir section.

The use of multi-lateral or fishbone' wells may be desirable for more efficient and/or more complete extraction of fluids, such as oil and gas, from a subterranean reservoir to surface from a single point of entry at surface. Such multi-lateral or fishbone wells generally comprise a primary wellbore having a cemented casing or liner and one or more open hole lateral wellbores formed by drilling through a sidewall of the cemented casing or liner. It is known to stimulate the lateral wellbores by injecting acid from the primary wellbore into the lateral wellbores. However, such techniques have resulted in low oil and/or gas production, solids production and hole collapse in the lateral wellbores. Accordingly, it is known to install a liner such as a CAJ liner in one or more lateral wellbores of a multi-lateral well to alleviate such problems. However, these known multi-lateral wells rely on pressure-tight completion infrastructure at each junction between production tubing installed in the primary wellbore and a CAJ liner in each lateral wellbore. Installing such pressure-tight completion infrastructure at each junction of a multi-lateral well may be time-consuming and/or expensive, with the time and/or costs involved increasing with the number of lateral wellbores.

SUMMARY

According to a first aspect of the present invention there is provided a method for completion of a well, comprising: forming a lateral wellbore extending laterally from a primary wellbore so as to define a junction between the primary wellbore and the lateral wellbore; preventing fluid flow between the lateral wellbore and the primary wellbore; and then permitting fluid flow between the lateral wellbore and the primary wellbore.

It should be understood that terms such as "upper", "lower", "upwardly", "downwardly", below", above", and other related terms, refer to the arrangement of a feature relative to an entry point of a bore, such that a region or section nearer to an entry point may be defined as an upper region, and a region further from an entry point may be defined as a lower region. In this respect, the drilled bore may extend vertically, horizontally, and/or be inclined relative to vertical and/or horizontal directions.

The primary wellbore may comprise a primary borehole drilled into a subterranean formation and a liner or casing which is secured relative to the primary borehole using cement.

Forming the lateral wellbore may comprise drilling a lateral borehole through the casing and cement of the primary wellbore into the subterranean formation.

The method does not require pressure integrity between the primary wellbore and the subterranean formation surrounding the primary wellbore in the region of the junction between the primary wellbore and the lateral wellbore. Similarly, the method does not require pressure integrity between the lateral borehole of the lateral wellbore and the subterranean formation. Consequently, the method may permit production from a multi-lateral well without requiring the installation of completion infrastructure extending from the primary wellbore into each lateral wellbore to provide pressure integrity at wellbore junctions defined between the primary wellbore and the lateral wellbores. The method may reduce the time and cost of completing multi-lateral wells.

Hydrocarbons may flow into the lateral wellbore from a formation surrounding the lateral wellbore. Preventing fluid flow between the lateral wellbore and the primary wellbore may prevent the flow of hydrocarbons from the lateral wellbore into the primary wellbore. This may prevent the production of the hydrocarbons from the formation surrounding the lateral wellbore to surface via the primary wellbore before a completion assembly is installed in the primary wellbore.

The method may comprise installing a completion assembly in the primary wellbore in the region of the junction between the step of preventing fluid flow between the lateral wellbore and the primary wellbore and the step of permitting fluid flow between the lateral wellbore and the primary wellbore.

Once a completion assembly is installed in the primary wellbore and communication is established between the primary wellbore and the lateral wellbore to permit fluid to flow from the lateral wellbore to the primary wellbore, hydrocarbons from the formation surrounding the lateral wellbore may be produced to surface via the completion assembly.

The method may comprise treating the lateral wellbore.

The method may comprise treating the lateral wellbore before preventing fluid flow between the lateral wellbore and the primary wellbore.

Such a method permits stimulation of the lateral wellbore without requiring the installation of completion infrastructure extending from the primary wellbore into the lateral wellbore to provide pressure integrity in a region of the junction. Such a method may enhance oil and/or gas production, reduce solids production and at least partially mitigate against the risk of hole collapse in the region of wellbore junctions defined between the primary wellbore and the lateral wellbores of a multi-lateral well. Such a method may reduce the complexity and/or lower the cost of completing a multi-lateral well.

The method may comprise treating a borehole wall of the lateral wellbore and/or a formation surrounding the lateral wellbore.

The method may comprise subjecting the lateral wellbore to a matrix treatment and/or a hydraulic fracturing treatment.

The method may comprise injecting a fluid into the lateral wellbore.

The method may comprise injecting a fluid into the lateral wellbore for stimulating the production of hydrocarbons into the lateral wellbore.

The method may comprise injecting at least one of a chemical, an acid, a gel, a friction reducer, a crosslinker, a breaker, a surfactant, water, a proppant, particulates, sand and the like into the lateral wellbore.

The primary wellbore may comprise a primary borehole.

The primary wellbore may comprise a liner or a casing cemented to the primary borehole.

The method may comprise installing a tubular string comprising a plurality of axially spaced fluid ports in the lateral wellbore.

For example, the method may comprise inserting or running the tubular string into the lateral wellbore.

The tubular string may be configured for installation in an open hole.

The tubular string may comprise at least one of a liner, a sleeve, a screen, casing, production tubing and the like in the lateral wellbore.

The tubular string may comprise a Controlled Acid Jet (CAd) liner.

A spacing between adjacent fluid ports may vary along a length of the tubular string. For example, a spacing between adjacent fluid ports may decrease from an uphole end of the tubular string to a downhole end of the tubular string. Such an arrangement of fluid ports may provide a more even fluid flow distribution when injecting a fluid through the tubular string.

The fluid ports may be arranged circumferentially around the tubular string.

The tubular string may comprise multiple sets of fluid ports. Each set of fluid ports may comprise a plurality of circumferentially arranged fluid ports. Different sets of fluid ports may be arranged at different positions along the length of the tubular string.

A spacing between adjacent sets of fluid ports may vary along the length of the tubular string. For example, a spacing between adjacent sets of fluid ports may decrease from an uphole end of the tubular string to a downhole end of the tubular string.

The tubular string may comprise a valve operable between an open configuration in which fluid is permitted to flow through a corresponding fluid port and a closed configuration in which fluid is prevented from flowing through the corresponding fluid port.

The tubular string may comprise a plurality of valves, each valve being operable between an open configuration in which fluid is permitted to flow through a corresponding fluid port and a closed configuration in which fluid is prevented from flowing through the corresponding fluid port.

Each valve may be operable between a closed and an open configuration in response to receipt of a stimulus at or proximate to the tubular string.

The stimulus may be transmitted from a remote location.

The stimulus may be transmitted from surface.

The stimulus may comprise an acoustic signal, an electromagnetic signal or a pressure pulse or the like.

The tubular string may be configured to receive or to detect the proximity of a stimulus device.

The stimulus device may comprise a ball, dart, or the like.

The stimulus device may comprise a Radio Frequency Identification (RFID) tag.

The method may comprise dropping, pumping, flushing or otherwise transmitting the stimulus device from a remote location to the tubular stung.

The method may comprise sealing the tubular string with respect to a borehole wall of the lateral wellbore.

The method may comprise sealing the tubular string with respect to a borehole wall of the lateral wellbore at a position adjacent the junction.

The method may comprise using a packer such as an external casing packer between an outer surface of the tubular string and the borehole wall of the lateral wellbore.

The method may comprise inserting or running the tubular string from surface along at least part of the primary wellbore into the lateral wellbore.

The method may comprise inserting or running the tubular string into the lateral wellbore on a running string such as a frac string or the like.

The method may comprise mounting the tubular string on the end of the running string.

The method may comprise sealing the tubular string with respect to the running string.

The method may comprise sealing the tubular string with respect to the running string at a position adjacent the junction.

The method may comprise sealing the tubular string with respect to the running string using one or more external packers located between the tubular string and the running string. The running string may provide a sealed fluid-flow path which extends from surface to an upper end of the tubular string.

The method may comprise injecting a fluid through one or more of the fluid ports of the tubular string to the borehole wall of the lateral wellbore.

The method may comprise injecting a fluid into the tubular string through the running string.

Preventing fluid flow between the lateral wellbore and the primary wellbore may comprise installing an isolator device in the lateral wellbore.

Preventing fluid flow between the lateral wellbore and the primary welibore may comprise installing the isolator device in the lateral wellbore at a position adjacent to the junction.

Preventing fluid flow between the lateral wellbore and the primary wellbore may comprise preventing fluid flow between an interior of the tubular string from an interior of the primary wellbore.

Preventing fluid flow between the lateral wellbore and the primary wellbore may comprise installing an isolator device within an interior of the tubular string.

Preventing fluid flow between the lateral wellbore and the primary wellbore may comprise activating the isolator device on or after installation in the lateral wellbore.

Such an isolator device may be used to prevent fluid flow between the lateral wellbore and the primary wellbore in the absence of any pressure integrity along the primary wellbore and/or the lateral wellbore in a region of the junction.

Preventing fluid flow between the lateral wellbore and the primary wellbore may comprise inserting or running the isolator device from surface along at least part of the primary wellbore into the lateral wellbore.

The method may comprise engaging the tubular string with a running string such as a work string, frac string or the like.

The method may comprise sealingly engaging the tubular string with the running string.

The method may comprise engaging a lower end of the running string with an upper end of the tubular string.

The method may comprise stinging a lower end of the running string into an upper end of the tubular string.

The running string may comprise a stinger and the method may comprise engaging the stinger with the tubular string.

The method may comprise inserting or running the isolator device through the running string.

The method may comprise sealingly engaging the isolator device with a landing profile located in the lateral wellbore.

The method may comprise sealingly engaging the isolator device with a landing profile located in the lateral wellbore adjacent to the junction.

The landing profile may be defined by the tubular string.

The landing profile may be defined at an uphole end of the tubular string.

The method may comprise inserting or running the isolator device into the lateral wellbore on coiled tubing.

The method may comprise inserting or running the isolator device into the lateral wellbore using at least one of slickline, wireline and a tractor.

The method may comprise activating the isolator device via coiled tubing.

The isolator device may be configurable between an activated state in which the isolator device substantially prevents fluid flow therethrough, and a de-activated state in which the isolator device permits or at least does not unduly impede fluid flow therethrough.

The isolator device may be configured for activation on receipt of a stimulus at or proximate to the isolator device.

The method may comprise transmitting the stimulus to the isolator device from a remote location.

The method may comprise transmitting the stimulus to the isolator device from surface.

The stimulus may comprise an acoustic signal and/or an electromagnetic signal.

The isolator device may be configured to receive or to detect the proximity of a stimulus device.

The isolator device may be configured for activation on receipt of or on detection of the proximity of the stimulus device.

The stimulus device may comprise a ball, dart, or the like.

The stimulus device may comprise a Radio Frequency Identification (RFID) tag.

The method may comprise dropping, pumping, flushing or otherwise transmitting the stimulus device from a remote location to a location at or proximate to the isolator device.

The method may comprise preventing fluid flow between the lateral wellbore and the primary wellbore after treatment of the lateral wellbore, for example after stimulation of the lateral wellbore.

The isolator device may be configured for deployment with the tubular string.

The isolator device may form part of, be incorporated within, or be otherwise attached to the tubular string. During installation of the isolator device into the lateral wellbore with the tubular string, the isolator device may be de-activated to permit treating of the lateral wellbore through the tubular string.

The method may comprise perforating the primary wellbore.

The method may comprise perforating a casing or liner installed in the primary wellbore.

The method may comprise perforating any cement used to fix the casing or liner installed in the primary wellbore to a borehole of the primary wellbore.

The method may comprise perforating a wall of a borehole of the primary wellbore.

The method may comprise perforating the primary wellbore uphole and/or downhole from the junction. Since the primary and/or secondary wellbores may lack structural integrity in the region of the junction, such a method avoids perforation of the primary wellbore in the region of the junction and may avoid or at least mitigate any risk of structural damage to the primary and/or secondary wellbores in the region of the junction as a result of perforation.

The method may comprise perforating the primary wellbore after preventing fluid flow between the lateral wellbore and the primary wellbore.

The method may comprise perforating the primary wellbore before preventing fluid flow between the lateral wellbore and the primary wellbore.

The completion assembly may comprise a conventional completion assembly.

The completion assembly may comprise at least one of production tubing, one or more packers, and one or more screen sections. The completion assembly may comprise one or more fluid valves such as one or more sliding side door (SSD) valves and/or one or more inflow control valves (by).

Installing the completion assembly in the primary wellbore may comprise locating the completion assembly in the primary wellbore.

Installing the completion assembly in the primary wellbore may comprise activating the completion assembly once located in the primary wellbore.

Installing the completion assembly in the primary wellbore may comprise activating one or more packers of the completion assembly so that each packer provides a seal between an outer surface of the production tubing and an inner surface of the primary wellbore. Installing the completion assembly in the primary wellbore may comprise activating a pair of axially spaced packers to define an annular zone or region therebetween.

Installing the completion assembly in the primary wellbore may comprise locating and/or activating one or more packers in the primary wellbore uphole and/or downhole of the junction. Such an arrangement may serve to define an annular zone or region which extends radially between an outer surface of the production tubing and an inner surface of the primary weilbore and which extends axially within the primary wellbore above and below the junction.

Installing the completion assembly in the primary wellbore may comprise installing a string of production tubing at or adjacent to the junction.

Installing the completion assenibly in the primary wellbore may comprise installing one or more fluid valves at or adjacent the junction. Each fluid valve may be configured to selectively provide fluid flow communication through a wall of the production tubing.

The method may comprise installing a completion assembly uphole and/or downhole from the junction. The method may comprise installing a first completion assembly in the primary wellbore below the junction before forming the lateral wellbore.

The method may comprise installing a first completion assembly in the primary wellbore downhole from the junction before drilling the lateral wellbore.

The method may comprise installing a first completion assembly in the primary wellbore downhole from the junction before treating the lateral wellbore.

The method may comprise installing a first completion assembly in the primary wellbore downhole from the junction before preventing fluid flow between the lateral wellbore and the primary wellbore.

The method may comprise installing a second completion assembly in the primary wellbore adjacent and/or uphole from the junction after preventing fluid flow between the lateral wellbore and the primary wellbore.

The method may comprise treating the primary wellbore.

Treating the primary wellbore may comprise treating a borehole wall of the primary wellbore and/or a formation surrounding the primary wellbore.

The method may comprise subjecting the primary wellbore to a matrix treatment and/or a hydraulic fracturing treatment.

The method may comprise injecting a fluid into the primary wellbore.

The method may comprise injecting a stimulation fluid into the primary wellbore for stimulating the production of hydrocarbons into the primary wellbore.

The method may comprise injecting at least one of a chemical, an acid, a gel, a friction reducer, a crosslinker, a breaker, a surfactant, water, a proppant, particulates, sand and the like into the primary wellbore.

The method may comprise injecting a fluid out through one or more fluid valves of the completion assembly into the primary wellbore.

The method may comprise treating the primary welibore uphole from and/or downhole from the junction. The method may comprise injecting a fluid into the primary wellbore above and/or below the junction. The method may comprise injecting a fluid out through one or more fluid valves of the completion assembly into the primary wellbore uphole and/or downhole from the junction. Since the primary wellbore and/or the lateral wellbore may lack structural integrity in the region of the junction, treating the primary wellbore uphole and/or downhole from the junction but not in the region of the junction may avoid damage to the primary wellbore and/or the lateral wellbore in the region of the junction. Such a method may, for example, be employed where the completion assembly is configured to selectively permit treatment of the primary wellbore uphole and/or downhole from the junction, but not in the region of the junction.

The isolator device may be configured to remain in the activated state even when subjected or exposed to the effects of any fluid used to treat the primary wellbore.

The method may comprise permitting fluid flow between the primary wellbore and the lateral wellbore before treating the primary wellbore.

The method may comprise permitting fluid flow between the primary wellbore and the lateral wellbore after treating the primary wellbore.

The method may comprise permitting fluid flow between the primary wellbore and the lateral wellbore after a predetermined period of time has elapsed after preventing fluid flow between the lateral wellbore and the primary wellbore.

Such methods which do not rely on the use of fluid pressure for transmission of a stimulus to permit fluid flow between the primary wellbore and the lateral wellbore may be advantageous because the lack of integrity of the primary wellbore and/or the lateral wellbore in the region of the junction may mean that the primary wellbore and/or the lateral wellbore in the region of the junction are exposed to a pressure of the formation in the region of the junction making control of fluid pressure in the region of the junction difficult or impossible.

Permitting fluid flow between the primary wellbore and the lateral wellbore may comprise de-activating the isolator device.

Permitting fluid flow between the primary wellbore and the lateral wellbore may comprise de-activating the isolator device after elapse of a pre-determined time period from activation of the isolator device.

The isolator device may comprise an actuator for activating and/or de-activating the isolator device.

The isolator device may comprise a controller for controlling the actuator.

The controller may comprise a timer.

The isolator device may comprise a power source, for example a battery, for providing power to the controller and/or the actuator.

Once the completion assembly has been installed in the primary wellbore adjacent to the junction, access to the isolator device may be restricted or impossible.

Accordingly, running an intervention operation to de-activate and/or retrieve the isolator device through the primary wellbore may be difficult or impossible. De-activating the isolator device after the elapse of a pre-determined time period from activation of the isolator device may permit fluid flow between the primary wellbore and the lateral wellbore without intervention.

Permitting fluid flow between the primary wellbore and the lateral wellbore may comprise de-activating the isolator device in response to a stimulus received by the isolator device.

The stimulus may be transmitted to the isolator device from a remote location.

The stimulus may be transmitted to the isolator device from surface.

Accordingly, running an intervention operation to de-activate and/or retrieve the isolator device through the primary wellbore may be difficult or impossible. Transmitting a stimulus to the isolator device from a remote location may permit fluid flow between the primary wellbore and the lateral wellbore without intervention.

The method may comprise transmitting an acoustic signal and/or an electromagnetic signal to the isolator device for de-activation of the isolator device.

The isolator device may comprise a plug portion configured to provide a seal or barrier to fluid flow through the isolator device.

The plug portion may comprise a frangible or a rupturable element.

The plug portion may comprise a glass disc, a burst disc and/or the like.

The actuator may be configured to break, fracture, rupture, dissolve or otherwise remove the plug portion.

The actuator may comprise an explosive charge which is configured to break or rupture the plug portion to de-activate the isolator device.

The actuator may comprise a fluid reservoir containing a fluid such as a chemical, acid or the like for at least partially dissolving the plug portion to de-activate the isolator device.

The isolator device may comprise a valve which is configurable between a closed configuration and an open configuration.

The actuator may be configured to activate and/or de-activate the valve.

The valve may comprise at least one of a flapper valve, a ball valve, a sliding door valve, an inline valve and the like.

The isolator device may comprise at least one of a flapper valve, a ball valve, a sliding door valve, an inline valve and the like.

The method may comprise forming a further lateral wellbore extending laterally from the primary wellbore between the step of preventing fluid flow between the lateral wellbore and the primary wellbore and the step of permitting fluid flow between the lateral wellbore and the primary wellbore. Such a method may be used to prevent or control production from the lateral wellbore, whilst the further lateral wellbore is formed.

The method may comprise treating the further lateral wellbore before permitting fluid flow between the lateral wellbore and the primary wellbore. Such a method may be used to prevent or control production from the lateral wellbore, whilst the further lateral wellbore is stimulated.

The further lateral wellbore may be formed so as to define a further junction between the primary wellbore and the further lateral wellbore.

The method may comprise preventing fluid flow between the further lateral wellbore and the primary wellbore.

The method may comprise permitting fluid flow between the further lateral wellbore and the primary wellbore.

Such a method may permit a plurality of lateral wellbores to be formed and stimulated and production from each lateral wellbore to be prevented or controlled until after completion of the primary wellbore.

According to a second aspect of the present invention there is provided an isolator device for use in temporarily preventing fluid flow between a primary wellbore and a lateral wellbore, the lateral wellbore extending laterally from the primary wellbore so as to define a junction between the primary wellbore and the lateral wellbore, wherein the isolator device is configured for installation in the lateral wellbore and is configurable from an activated state in which the isolator device prevents fluid flow along a fluid flow path between the lateral wellbore and the primary wellbore and a de-activated state in which the isolator device permits fluid flow along the fluid flow path.

The isolator device may be configured for location in the lateral wellbore adjacent to the junction.

The isolator device may be configured to prevent fluid flow between the lateral welibore and the primary welibore in the absence of any pressure integrity of the primary wellbore and/or the lateral wellbore in the region of the junction.

The isolator device may be configurable from the de-activated state to the activated state.

The isolator device may be configured to engage a tubular string comprising a plurality of axially spaced fluid ports in the lateral wellbore.

The tubular string may comprise a Controlled Acid Jet (CAJ) liner.

The isolator device may be configured for installation within an interior of the tubular string.

The isolator device may be configured to be inserted or run from surface along at least part of the primary wellbore into the lateral wellbore.

The isolator device may be configured to be inserted or run from surface into the lateral wellbore through a running string such as a work string, frac string or the like.

The isolator device may be configured for sealing engagement with a landing profile located in the lateral wellbore.

The isolator device may be configured for sealing engagement with a landing profile located in the lateral wellbore adjacent to the junction.

The landing profile may be defined by the tubular string.

The landing profile may be defined at an uphole end of the tubular string.

The isolator device may be configured to be inserted or run from surface into the lateral wellbore on coiled tubing.

The isolator device may be configured to be inserted or run from surface into the lateral wellbore using at least one of slickline, wireline and a tractor.

The isolator device may be configured for deployment with the tubular string.

The isolator device may form part of, be incorporated within, or be otherwise attached to the tubular string.

On installation of the isolator device into the lateral wellbore with the tubular string, the isolator device may be in a de-activated configuration to permit treating of the lateral wellbore through the tubular string.

The isolator device may be configured for activation on or after installation in the lateral wellbore.

The isolator device may be configured to be activated via coiled tubing.

The isolator device may be configured for activation on receipt of a stimulus during and/or after treatment of the lateral wellbore, for example during and/or after stimulation of the lateral wellbore.

The stimulus may comprise an acoustic signal and/or an electromagnetic signal.

The isolator device may be configured for activation on receipt of or on detection of the proximity of a stimulus device.

The stimulus device may comprise a ball, dart, or the like.

The stimulus device may comprise a Radio Frequency Identification (RFID) tag.

The isolator device may be configured for de-activation after elapse of a pre-determined time period from activation.

The isolator device may comprise a controller for controlling the actuator.

The controller may comprise a timer.

The isolator device may be configured for de-activation in response to a stimulus received by the isolator device.

The stimulus may be transmitted to the isolator device from a remote location.

The stimulus may be transmitted to the isolator device from surface. The isolator device may be configured for de-activation in response to an acoustic signal and/or an electromagnetic signal.

The plug portion may comprise a frangible or a rupturable element.

The plug portion may comprise a glass disc, a burst disc and/or the like.

The actuator may be configured to activate and/or de-activate the valve.

It should be understood that any feature defined in relation to one aspect may be provided in combination with any other aspect.

According to a third aspect of the present invention there is provided a well system comprising a primary wellbore, a lateral wellbore which extends laterally from the primary wellbore so as to define a junction between the primary wellbore and the lateral wellbore, a completion assembly located in the primary wellbore, and an isolator device located in the lateral wellbore and separated from the completion assembly, wherein the isolator device is configurable between an activated state in which the isolator device prevents fluid flow along a fluid flow path between the lateral wellbore and the primary wellbore, and a de-activated state in which the isolator device permits fluid flow along the fluid flow path.

The completion assembly may comprise a Perforate, Stimulate and Isolate (PSI) completion.

The well system may comprise a Controlled Acid Jet (CAJ) liner installed in the lateral wellbore.

According to a fourth aspect of the present invention there is provided a well system comprising a primary wellbore and a lateral wellbore extending laterally from the primary wellbore, wherein the primary wellbore includes completion infrastructure which defines a plurality of zones along a length of production tubing, each zone comprising an annular region around the production tubing and at least one valve for selectively providing fluid flow communication between the production tubing and the annular region, and the lateral wellbore is arranged in fluid flow communication with the annular region of a single zone.

The well system may comprise a Perforate, Stimulate and Isolate (PSI) completion installed in the primary wellbore.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further described by way of non-limiting example only with reference to the following figures of which: Figure 1 shows a well comprising a lateral wellbore extending laterally from a primary wellbore so as to define a junction between the primary wellbore and the lateral wellbore during stimulation of the lateral wellbore through a liner installed in the lateral well bore; Figure 2 shows the well of Figure 1 during installation of an isolator device into the liner; Figure 3 shows the well of Figure 1 after installation of the isolator device into the liner and withdrawal of the frac string and coiled tubing used to install the isolator device; Figure 4 shows the well of Figure 1 after perforation of the primary well bore; Figure 5 shows the well of Figure 1 during stimulation of the primary wellbore after installation of completion infrastructure into the primary wellbore; Figure 6 shows the well of Figure 1 during production after removal of the isolator device from the lateral wellbore; Figure 7A shows the liner and a landing shoe installed within the liner in a region of the well of Figure 1 in the vicinity of the junction; Figure 7B shows the well region of Figure 7A after engagement of a stinger device at the end of a frac string with the landing shoe during stimulation of the lateral wellbore through the frac string and the liner; Figure 7C shows the well region of Figure 7A after running an isolator device downhole on coiled tubing and engaging the isolator device with a landing profile of the landing shoe; Figure 7D shows the well region of Figure 7C after engagement of the isolator device with the landing profile and withdrawal of the coiled tubing; Figure 7E shows the well region of Figure 7D after withdrawal of the stinger device; Figure 7F shows the well region of Figure 7E during production after de-activation of the isolator device; Figure BA shows the liner and a landing shoe installed within the liner including a flapper valve isolator device in a region of a well comprising a lateral wellbore extending laterally from a primary wellbore in the vicinity of the junction; Figure BB shows the well region of Figure 8A after engagement of a stinger device at the end of a frac string with the landing shoe during stimulation of the lateral wellbore through the frac string and the liner; Figure 80 shows the well region of Figure 8A during activation of the isolator device using RFID tags; Figure 8D shows the well region of Figure 80 after activation of the isolator device; Figure BE shows the well region of Figure 3D after withdrawal of the stinger device with the isolator device still in an activated configuration; and Figure 8F shows the well region of Figure 8E during production after de-activation of the isolator device.

DETAILED DESCRIPTION OF THE DRAWINGS

Figures 1 to 6 illustrate a sequence of steps in the completion of a well 10 comprising a primary wellbore generally designated 12 extending from surface 14 to intercept a subterranean formation generally designated 16 and a lateral wellbore generally designated 20 extending laterally into the subterranean formation 16 from the primary wellbore 12 so as to define a junction generally designated 22 between the primary wellbore 12 and the lateral wellbore 20. Although the primary wellbore 12 is shown extending downwardly from a point of entry 24 of the well 10 at surface 14, it should be understood that the primary wellbore 12 may be inclined relative to the vertical and/or may even extend horizontally. Similarly, the orientation of the lateral wellbore 20 may also be different to the particular orientation of the lateral wellbore 20 shown in Figures 1 to 6. In addition, the well 10 may comprise a multi-lateral or fishbone well having one or more additional lateral wellbores (not shown).

Referring initially to Figure 1, the primary wellbore 12 comprises a primary borehole 30 drilled into the formation 16 and a liner or casing 32 which is secured relative to the primary borehole 30 using cement 34. The lateral wellbore 20 comprises a lateral borehole 40 drilled through the casing 32 and cement 34 of the primary wellbore 12 into the formation 16. It should be understood that, in general, there is no pressure integrity between the primary wellbore 12 and the subterranean formation 16 in the region of the junction 22. Similarly, there is no pressure integrity between the lateral borehole 40 and the subterranean formation 16.

A tubular string in the form of a Controlled Acid Jet (CAJ) liner 42 is run through the primary wellbore 12 into the lateral wellbore 20. The CAJ liner 42 comprises an external casing packer 44 which is activated to seal an external surface of the CAJ liner 42 relative to a wall of the lateral borehole 40. An external packer 52 is subsequently run with a frac string 50 through the primary wellbore 12 so as to sealingly engage an interior surface of the CAIJ liner 42. The CAJ liner 42 comprises a plurality of ports 46 distributed along its length. As illustrated by the arrows 60 in Figure 1, a stimulation fluid in the form of acid is injected into the formation 16 surrounding the lateral wellbore via the frac string 50 and the pods 46 of the CAd liner 42 to treat the formation 16 surrounding the lateral wellbore 20 for the stimulation of production of hydrocarbons from the formation 16 into the CAd liner 42 via the ports 46.

As shown in Figure 2, once stimulation of the formation 16 surrounding the lateral wellbore 20 is complete, an isolator device 62 is installed through the frac string in the primary wellbore 12 into the CAJ liner 42 within the lateral wellbore 20 using coiled tubing 64. As will be described in more detail below, the isolator device 62 sealingly engages a landing profile (not shown in Figure 1) defined within the CAd liner 42 so as to isolate an interior of the CAd liner 42 from an interior of the primary wellbore 12. Subsequently, the coiled tubing 64 and the frac string 50 are withdrawn from the well 10 to leave the isolator device 62 in position within the CAJ liner 42 as shown in Figure 3. The primary wellbore 12 is perforated at one or more locations uphole and/or downhole from the junction 22 to form perforations 66 extending into the formation 16 surrounding the primary wellbore 12 as shown in Figure 4. No perforation of the primary wellbore 12 takes place in the region of the junction 22 so as to avoid any damage of the primary and/or lateral wellbores 12, 20 in the region of the junction 22.

Referring to Figure 5, a completion assembly generally designated 70 is installed in the primary wellbore 12 including a region of the primary wellbore 12 at or adjacent the junction 22. As shown in Figure 5, the completion assembly 70 comprises a string of production tubing 72 and a plurality of production packers 74 which define a plurality of zones 78 of the primary wellbore. Each packer 74 provides a seal between an outer surface of the production tubing 72 and an inner surface of the casing 32 of the primary wellbore 12. Adjacent packers 74 define a corresponding annular region 76 around the production tubing 72. The completion assembly 70 comprises one or more valves 80 for controlling the flow of fluid in each zone 78 between an interior of the production tubing 72 and the corresponding annular region 76. It should be understood that the valves 80 may be any type of valve which is configurable between an open state in which the valve 80 permits fluid flow between the interior of the production tubing 72 and a corresponding annular region 76, and a closed state in which the valve 80 prevents fluid flow between the interior of the production tubing 72 and the corresponding annular region 76. The valves 80 may, in particular, comprise sliding side door valves.

As illustrated by the arrows 82 in Figure 5, a stimulation fluid in the form of acid is injected into the formation 16 surrounding the primary wellbore 12 via the production tubing 72 and the valves 80 to treat the formation 16 surrounding the primary wellbore 12 for the stimulation of production of hydrocarbons from the formation 16 in all zones 78 other than the zone 78 which bridges the junction 22. Stimulation of the formation 16 surrounding the primary wellbore 12 is avoided in the region of the junction 22 so as to avoid any damage of the primary and/or lateral wellbores 12, 20 in the region of the junction 22.

As will be described in more detail below, the isolator device 62 is configured to be de-activated once stimulation of the primary wellbore 12 is finished to permit fluid to flow from the lateral wellbore 20 into the primary wellbore 12. Once stimulation of the primary wellbore 12 is finished and the isolator device 62 is de-activated, hydrocarbons flow through the one or more valves 80 in each zone 78 in the primary wellbore 12 into the production tubing 72 towards surface 14 as shown by the arrows 84 in Figure 6. In addition, the valves 80 in the zone 78 which bridges the junction 22 with the lateral wellbore 20 are opened so as to permit hydrocarbons produced within the lateral wellbore 20 to flow through the CAJ liner 42 into the annular region 76 of the zone 78 which bridges the junction 22 and into the production tubing 72 via one or more valves towards the surface 14.

The operation of the isolator device 62 will now be described with reference to Figures 7A to 7F which show an uphole end 85 of the CAJ liner 42 located within the lateral borehole 40 in the region of the junction 22 (not shown in Figures 7A to 7F). It should be understood that in Figures 7A to 7F, the lateral borehole 40 is shown aligned horizontal for ease of illustration only. Figure 7A shows the uphole end 85 of the CAJ liner 42 located within the lateral borehole 40 after installing a generally tubular landing shoe 86 together with the external packer 52 within the CAJ liner 42. The landing shoe 86 defines a landing profile 88 for receiving the isolator device 62. The landing shoe 86 is sealed with respect to the CAJ liner 42 by the external packer 52. As shown in Figure 73, a stinger device 89 is mounted on the end of the frac string 50 (shown in Figures 1 and 2) and is run downhole so as to sealingly engage the landing shoe 86.

The frac string 50 provides a sealed path for the flow of stimulation fluid from the primary wellbore 12 to the lateral wellbore 20 through the landing shoe SGas indicated by arrow 90.

Once stimulation of the formation 16 surrounding the lateral wellbore 20 is complete, the isolator device 62 is run along the frac string 50 on coiled tubing 64 until the isolator device 62 sealingly engages the landing profile 88 of the landing shoe 86 as shown in Figure 7C to thereby isolate the lateral wellbore 20 from the primary wellbore 12 (not shown in Figure 7C). The isolator device 62 comprises a frangible plug portion in the form of a glass disc 92, an actuator in the form of an explosive charge 94, and a controller 96. The glass disc 92 is configured to provide a frangible seal across the interior of the landing shoe 86 so as to prevent the flow of fluid through the landing shoe 86.

With the isolator device 62 in engagement with the landing profile 88 of the landing shoe 86, the coiled tubing 64 is withdrawn from the frac string 50 resulting in the situation shown in Figure 7D. The stinger device 89 is subsequently detached from the landing shoe 86 and withdrawn from the primary wellbore 12 to leave the isolator device 62 in engagement with the landing shoe 86 as shown in Figure 7E.

The controller 96 of the isolator device 62 is configured to ignite the explosive charge 94 after a predetermined period has elapsed from engagement of the isolator device 62 with the landing shoe 86. Ignition of the explosive charge 94 breaks the glass disc 92 and thereby establishes communication between the primary wellbore 12 (not shown) and the lateral wellbore 20 as shown in Figure 7F. As indicated by arrow 98 in Figure 7F, hydrocarbon fluids are then permitted to flow through the landing shoe 86 from the lateral wellbore 20 into the annular region 76 adjacent to the production tubing 72 in the primary wellbore 12 adjacent to the junction 22 (see Figure 6). As shown in Figure 6, the hydrocarbon fluids may then flow to surface 14 via the one or more valves 80 and the production tubing 72.

Figures BA to 8F illustrate an alternative isolator device 162 which shares many like features with the isolator device 62 described with reference to Figures 7A to 7F and, as such, like features share like reference numerals. With reference initially to Figure BA, the isolator device 162 comprises a flapper valve 192, an actuator 194, and a controller 196. The isolator device 162 is brought into sealing engagement with a landing shoe 186 located within the CAJ liner 42. An outer surface of the landing shoe 186 is sealed with respect to an inner surface of the CAd liner 42 by the external packer 52.

As shown in Figure SB, a stinger device 189 mounted at the end of the frac string 50 (shown in Figures 1 and 2) is brought into sealing engagement with the landing shoe 186. The frac string 50 provides a sealed path for the flow of stimulation fluid from the primary wellbore 12 to the lateral wellbore 20 through the landing shoe 186 as indicated by arrow 190 in Figure 8B.

After stimulation of the lateral wellbore 20 is complete, radio frequency identification (RFID) tags 199 are injected from surface into the lateral wellbore 20 as shown in Figure 80. The controller 196 is configured to detect the proximity of the REID tags 199. In response to detection of the proximity of the REID tags 199, the controller 196 controls the actuator 194 to close the flapper valve 192 as shown in Figure SC. As shown in Figure SD, the lateral wellbore 20 is then isolated from the primary wellbore 12 (not shown in Figure 8D) to prevent fluid flow from the lateral wellbore 20 to the primary wellbore 12 (not shown in Figure SD). Once the flapper valve 192 is closed, the stinger device 189 is withdrawn leaving the landing shoe 186 in engagement with the CAJ liner 42 as shown in Figure SE. The controller 196 of the isolator device 162 is configured to open the flapper valve 192 after a predetermined period has elapsed from engagement of the isolator device 162 with the landing shoe 186 to thereby permit hydrocarbon fluids 198 to flow through the landing shoe 186 from the lateral wellbore 20 into the annular region 76 adjacent to the junction 22 in the primary wellbore 12 (see Figure 6). As shown in Figure 6, the hydrocarbon fluids may then flow to surface 14 via the one or more valves 80 and the production tubing 72.

One skilled in the art will appreciate that the foregoing methods and systems may be modified without departing from the scope of the present invention. For example, a first completion assembly may be installed within the primary wellbore 12 downhole from the junction 22 before isolating the lateral wellbore 20 from the primary wellbore 12. A second completion assembly may be installed within the primary wellbore 12 at and/or uphole from the junction 22 after isolating the lateral wellbore 20 from the primary wellbore 12.

Fluid flow may be permitted between the lateral wellbore 20 and the primary wellbore 12 before the primary wellbore 12 is perforated.

Fluid flow may be permitted between the lateral wellbore 20 and the primary wellbore 12 before stimulation of the primary wellbore 12.

The isolator device 62 may comprise a fluid reservoir containing a fluid such as a chemical, acid or the like for dissolving the one or more frangible plug portions to de-activate the isolator device.

The isolator device 162 may comprise a valve other than a flapper valve such as sliding door valve, a ball valve, an inline valve or the like.

Rather than being installed and sealed inside the CAJ liner 42 after installation of the CAJ liner 42 in the lateral wellbore 20, either of the isolator devices 62, 162 may be run as part of the CAJ liner 42 and may be installed together with the CAJ liner 42 in the lateral wellbore 20.

Claims

CLAIMS1. A method for completion of a well, comprising: forming a lateral wellbore extending laterally from a primary wellbore so as to define a junction between the primary wellbore and the lateral wellbore; preventing fluid flow between the lateral wellbore and the primary wellbore and then permitting fluid flow between the lateral wellbore and the primary wellbore.
2. A method according to claim 1 comprising: installing a completion assembly in the primary wellbore in the region of the junction between the step of preventing fluid flow between the lateral wellbore and the primary wellbore and the step of permitting fluid flow between the lateral wellbore and the primary wellbore.
3. A method according to claim 1 or 2, comprising treating the lateral wellbore.
4. A method according to claim 3, comprising treating the lateral wellbore before preventing fluid flow between the lateral wellbore and the primary wellbore.
5. A method according to claim 3 or 4, wherein treating the lateral wellbore comprises treating a borehole wall of the lateral wellbore and/or a formation surrounding the lateral wellbore.
6. A method according to any of claims 3 to 5, wherein treating the lateral wellbore comprises injecting a fluid into the lateral wellbore.
7. A method according to any of claims 3 to 6, wherein treating the lateral wellbore comprises injecting a fluid into the lateral wellbore for stimulating the production of hydrocarbons into the lateral wellbore.
8. A method according to any of claims 3 to 7, wherein treating the lateral wellbore comprises injecting an acid, a proppant and/or a production enhancing treatment into the lateral wellbore.
9. A method according to any preceding claim, comprising installing a tubular string in the lateral wellbore, the tubular string defining a plurality of axially spaced fluid ports through a sidewall thereof.
10. A method according to claim 9, comprising sealing the tubular string with respect to a borehole wall of the lateral wellbore.
11. A method according to claim 9 or 10, comprising sealing the tubular string with respect to a running string.
12. A method according to any preceding claim, wherein preventing fluid flow between the lateral wellbore and the primary wellbore comprises installing an isolator device in the lateral wellbore.
13. A method according to claim 12, comprising installing the isolator device in the lateral wellbore at a position adjacent to the junction.
14. A method according to any preceding claim, comprising perforating the primary wellbore.
15. A method according to any preceding claim, comprising perforating the primary wellbore uphole and/or downhole from the junction.
16. A method according to any preceding claim, comprising perforating the primary wellbore before and/or after preventing fluid flow between the lateral wellbore and the primary wellbore.
17. A method according to any of claims 2 to 16, wherein installing a completion assembly in the primary wellbore comprises installing at least one of production tubing, a production packer, a fluid valve and a screen section in the primary wellbore.
18. A method according to any of claims 2 to 17, wherein installing a completion assembly in the primary wellbore comprises installing a completion assembly in the primary wellbore uphole and/or downhole from the junction.
19. A method according to any of claims 2 to 18, comprising installing a first completion assembly in the primary wellbore downhole from the junction before preventing fluid flow between the lateral wellbore and the primary wellbore.
20. A method according to claim 19, comprising installing a second completion assembly in the primary wellbore adjacent to the junction and/or uphole from the junction after preventing fluid flow between the lateral wellbore and the primary wellbore.
21. A method according to any preceding claim, comprising treating the primary wellbore.
22. A method according to claim 21, comprising treating the primary wellbore uphole and/or downhole from the junction.
23. A method according to claim 21 or 22, comprising permitting fluid flow between the primary wellbore and the lateral wellbore before, during or after treating the primary wellbore.
24. A method according to any preceding claim, comprising permitting fluid flow between the primary wellbore and the lateral wellbore on the elapse of a predetermined period of time after preventing fluid flow between the lateral wellbore and the primary wellbore.
25. A method according to any preceding claim, comprising: forming a further lateral wellbore extending laterally from the primary wellbore between the step of preventing fluid flow between the lateral wellbore and the primary wellbore and the step of permitting fluid flow between the lateral wellbore and the primary wellbore.
26. A method according to claim 25, comprising: treating the further lateral wellbore before permitting fluid flow between the lateral wellbore and the primary wellbore.
27. An isolator device for use in temporarily preventing fluid flow between a primary wellbore and a lateral wellbore which extends laterally from the primary wellbore so as to define a junction between the primary wellbore and the lateral wellbore, wherein the isolator device is configured for installation in the lateral wellbore and is configurable from an activated state in which the isolator device prevents fluid flow along a fluid flow path between the lateral wellbore and the primary wellbore and a de-activated state in which the isolator device permits fluid flow along the fluid flow path.
28. An isolator device according to claim 27, wherein the isolator device is configured for installation in the lateral wellbore in a region of the junction.
29. An isolator device according to claim 27 or 28, wherein the isolator device is configured for use in providing isolation between the primary wellbore and the lateral wellbore in the absence of any pressure integrity of the primary wellbore and/or the lateral wellbore in a region of the junction.
30. An isolator device according to any of claims 27 to 29, wherein the isolator device is configured for activation using coiled tubing.
31. An isolator device according to any of claims 27 to 30, wherein the isolator device is configured for de-activation after elapse of a predetermined time period from activation of the isolator device.
32. An isolator device according to any of claims 27 to 31, comprising an actuator for activating and/or de-activating the isolator device.
33. An isolator device according to claim 32, comprising a controller for controlling the actuator.
34. An isolator device according to claim 32 or 33, comprising a power source for providing power to the controller and/or the actuator.
35. An isolator device according to claim 33 or 34, wherein the controller comprises a timer.
36. An isolator device according to any of claims 32 to 35, comprising a frangible and/or a rupturable plug portion.
37. An isolator device according to claim 36, wherein the plug portion comprises a glass disc and/or a burst disc.
38. An isolator device according to claim 36 or 37, wherein the actuator is configured to remove the plug portion.
39. An isolator device according to claim 38, wherein the actuator comprises an explosive charge which is configured to break or rupture the plug portion.
40. The isolator device according to any of claims 36 to 39, comprising a fluid reservoir containing a fluid for at least partially dissolving the plug portion.
41. An isolator device according to any of claims 32 to 35, comprising a valve which is configurable between a closed configuration and an open configuration.
42. An isolator device according to claim 41, wherein the valve comprises at least one of a flapper valve, a ball valve, a sliding door valve, and an inline valve.
43. An isolator device according to claim 41 or 42, wherein the actuator is configured to activate and/or de-activate the valve.
44. An isolator device according to claim 43, wherein the actuator is configured to activate the valve more than once and/or de-activate the valve more than once.
45. An isolator device according to any of claims 27 to 44, wherein the isolator device is configured to be de-activated as a result of differential pressure.
46. A well system comprising a primary wellbore, a lateral wellbore which extends laterally from the primary wellbore so as to define a junction between the primary wellbore and the lateral wellbore, a completion assembly located in the primary wellbore, and an isolator device located in the lateral wellbore and separated from the completion assembly, wherein the isolator device is configurable between an activated state in which the isolator device prevents fluid flow along a fluid flow path between the lateral wellbore and the primary wellbore, and a de-activated state in which the isolator device permits fluid flow along the fluid flow path.
47. A well system comprising a primary wellbore and a lateral wellbore extending laterally into the primary wellbore, wherein the primary wellbore includes completion infrastructure which defines a plurality of zones along a length of production tubing, each zone comprising an annular region around the production tubing and at least one valve for selectively providing fluid flow communication between the production tubing and the annular region, and the lateral wellbore is arranged in fluid flow communication with the annular region of a single zone.