Valve and a method for closing fluid communication between a well and a production string, and a system comprising the valve

A valve, a system and a method are for closing fluid communication between a well and a production string when a content of an undesired fluid in the fluid flow exceeds a predetermined level. The valve has a primary flow channel having a primary inlet through a flow barrier, and a low pressure portion; a secondary flow channel having a secondary inlet through the flow barrier and provided with a flow restrictor; a chamber connected to the secondary flow channel; a piston for opening and closing the primary flow channel; and an inflow control element movable in response to a density of a fluid. The inflow control element is exposed to the fluid flow upstream of the flow barrier and moves to close the secondary inlet when the content of the undesired fluid exceeds the predetermined level, activating the piston and closing the valve.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. national stage application of International Application PCT/NO2018/050311, filed Dec. 14, 2018, which international application was published on Aug. 22, 2019, as International Publication WO 2019/160423 in the English language. The International Application claims priority of Norwegian Patent Application No. 20180230, filed Feb. 13, 2018. The international application and Norwegian application are both incorporated herein by reference, in entirety.

FIELD

The present invention relates to a valve and a system for use in a well. More particularly, the invention relates to a valve for closing inflow of various fluids that may be drained from a reservoir or utilized for preparing the well. The fluids may typically be prevented from being drained into a production string when a content of an undesired fluid in the fluid flow exceeds a predetermined level. In this document the term “level” means volume fraction of undesired fluid.

BACKGROUND

Undesired fluids might typically, but not exclusively, be gas or water. A person skilled in the art will appreciate that fluids regarded as desired or undesired will vary depending on the purpose of the well and the operational scenario.

Thus, one purpose of the invention is to control the inflow of various fluids that may be drained from a reservoir or utilized for preparing the well. In a well for producing gas or oil such fluids may be one or more of oil, gas and water which is drained from the reservoir, and also well construction fluids such as drilling fluid and completion fluids which are used when constructing the well prior to initial start-up of production from the well.

The valve and the system according to the invention are configured to discriminate between desired and undesired fluids when the undesired fluid exceeds a predetermined level. The invention may form part of an autonomous inflow control device (AICD). A plurality of AICDs may be distributed along a reservoir section of a well to block or restrict inflow of unwanted fluids from the reservoir, typically water and gas.

Modern long-reach horizontal production wells for oil and gas have the objective to increase the contact to a productive reservoir. Modern drilling, both offshore and onshore, is a costly operation as the initial cost of establishing a secure and cased wellbore down to the reservoir depth is mandatory, independent of the later well objective. Such wells might penetrate several thousands of meters of productive reservoir, and in order to establish desired productivity along these wellbores, proper removal of drilling fluids and other well construction fluids are required during the initial startup and clean-up of these wells.

Today, AICDs commonly used in the petroleum exploration industry are configured in such a way that they distinguish between unwanted fluids (normally gas and water) and wanted fluids (normally oil) based on differences in fluid viscosity. This results in different Re (Reynolds number—a dimensionless number that gives a measure of the ratio of inertial forces to viscous forces for given flow conditions) and therefore different flow characteristics, e.g. different pressure drop across a hydraulic restriction. A person skilled in the art will know that Reynolds number is a dimensionless number that gives a measure of the ratio of inertial forces to viscous forces for given flow conditions. These differences are then transformed into a force that controls the opening and closing of the AICD.

However, differences in Reynolds number are not necessarily caused by different viscosities. It can also be caused by differences in velocity. In a heterogeneous reservoir with large variations in permeabilities and local inflow rates along the reservoir, the velocity and therefore the Reynolds number can be very different in different AICDs along the reservoir. This becomes even more challenging if the objective is to distinguish between two fluids that only have a small difference in viscosity, like water and light oil.

The effective viscosity of a two-phase mixture (oil-gas or oil-water) is dominated by the viscosity of the continuous phase. This means that the effective viscosity of the mixture varies significantly near that inversion point (typically around 50% volume fraction), but not so much when approaching the one-phase limit (pure gas or pure water). It is often desirable to block or restrict the unwanted fluid only when its volume fraction approaches a high value close to 100%, for example 90%, but this will be challenging for AICDs based on viscosity differences as the effective viscosity of the mixture is practically insensitive to the volume fraction at high volume fractions.

Publication US2008041581 A1 discloses a fluid flow control apparatus for controlling the inflow of production fluids from a subterranean well. The apparatus includes a fluid discriminator section and a flow restrictor section that is configured in series with the fluid discriminator section such that fluid must pass through the fluid discriminator section prior to passing through the flow restrictor section. The fluid discriminator section comprises a plurality of free floating balls, each ball operable to autonomously restrict a hole and thereby at least a portion of an undesired fluid type, such as water or gas, from the production fluids. The flow restrictor section is operable to restrict the flow rate of the production fluids, thereby minimizing the pressure drop across the fluid discriminator section.

The publication US2007246407 discloses inflow control devices for sand control screens. A well screen includes a filter portion and at least two flow restrictors configured in series, so that fluid which flows through the filter portion must flow through each of the flow restrictors. At least two tubular flow restrictors may be configured in series, with the flow restrictors being positioned so that fluid which flows through the filter portion must reverse direction twice to flow between the flow restrictors. US2007246407 also discloses a method of installing a well screen wherein the method includes the step of accessing a flow restrictor by removing a portion of an inflow control device of the screen. US2007246407 suggests a plurality of free-floating balls in annular chambers. If the fluid flowing through the chamber has the same density as the balls, the balls will start to flow along with the fluid. Unless a ball is trapped inside a recirculation zone, it will eventually be carried to an exit hole, which it blocks. Suction force will cause the ball to block the hole continuously until production is stopped. A production stop will cause pressure equalization, such that the ball can float away from the hole. The free-floating balls block a main flow passage.

Publication US20080041580 discloses an apparatus for use in a subterranean well wherein fluid is produced which includes both oil and gas. The apparatus comprises: multiple first flow blocking members, each of the first members having a density less than that of the oil, and the first members being positioned within a chamber so that the first members increasingly restrict a flow of the gas out of the chamber through multiple first outlets. The flow blocking members block a main flow passage.

Publications US2008041582 discloses an apparatus which is based on the same principles as US20080041580 mentioned above.

Publication US20130068467 discloses an inflow control device for controlling fluid flow from a subsurface fluid reservoir into a production tubing string, the inflow control device comprising: a tubular member defining a central bore having an axis, wherein upstream and downstream ends of the tubular member may couple to the production tubing string; a plurality of passages formed in a wall of the tubular member; an upstream inlet to the plurality of passages leading to an exterior of the tubular member to accept fluid; each passage having at least two flow restrictors with floatation elements of selected and different densities to restrict flow through the flow restrictors in response to a density of the fluid; at least one pressure drop device positioned within each passage in fluid communication with an outflow of the flow restrictors, the pressure drop device having a pressure piston for creating a pressure differential in the flowing fluid based on the reservoir fluid pressure; and wherein an outflow of the pressure drop device flows into an inflow fluid port in communication with the central bore.

Publication WO2014081306 discloses an apparatus and a method for controlling fluid flow in or into a well. The apparatus includes at least one housing having an inlet and at least one outlet, one of which is arranged in a top portion or a bottom portion of the housing when in a position of use, and a flow control means disposed within the housing. The flow control means has a density that is higher or lower than a density of a fluid to be controlled and a form adapted to substantially block the outlet of the housing when the flow control means is in a position abutting the outlet.

In the prior art apparatuses referred above, the unwanted fluid, such as gas or water, is blocked by means of flow control elements arranged in a main flow path. Thus, it is difficult for the apparatus to control where an interface of the wanted and unwanted fluid is located.

Publications US20150060084 A1 and W02016033459 A1 disclose a flow control device to improve a well operation, such as a production operation. A flow control device has a valve positioned in a housing for movement between flow positions. The different flow positions allow different levels of flow through a primary flow port. At least one flow regulation element is used in cooperation with and in series with the valve to establish a differential pressure acting on the valve. The differential pressure is a function of fluid properties and is used to autonomously actuate the flow control device to an improved flow position. Different fluids with different viscosities or Reynolds numbers have different flow characteristics and pressure drop through the secondary flow path, which means that the piston can open for wanted fluid and close for unwanted fluid.

Publication WO 2013139601 discloses a fluid flow control device comprising a housing having a fluid inlet and at least one fluid outlet. A first fluid flow restrictor serving as an inflow port to a chamber in the housing, and a second fluid flow restrictor serving as an outflow port from the chamber. The first fluid flow restrictor and the second fluid flow restrictor are configured to generate different fluid flow characteristics. The chamber comprises actuating means that is responsive to fluid pressure changes in the chamber. The first fluid flow restrictor and the second fluid flow restrictor are configured to impose its respective different fluid flow characteristics. The device is sensitive inter alia to Reynolds number.

Publication US2009151925 discloses a well screen inflow control device with check valve flow controls. A well screen assembly includes a filter portion and a flow control device which varies a resistance to flow of fluid in response to a change in velocity of the fluid. Another well screen assembly includes a filter portion and a flow resistance device which decreases a resistance to flow of fluid in response to a predetermined stimulus applied from a remote location. Yet another well screen assembly includes a filter portion and a valve including an actuator having a piston which displaces in response to a pressure differential to thereby selectively permit and prevent flow of fluid through the valve.

Publication NO20161700 discloses an apparatus and a method for controlling a fluid flow in, into or out of a well, the apparatus comprising: a main flow channel having an inlet and an outlet being in fluid communication with the fluid flow; at least one chamber arranged in fluid communication with the main flow channel, the chamber having at least one flow control element movable between a first non-blocking position and a second blocking position for the fluid flow between the inlet and the outlet of the main flow channel, the flow control element movable in response to density of fluid in said chamber. The main flow channel is provided with pressure changing means causing a pressure differential in a fluid return conduit providing fluid communication between said chamber and a portion of the main flow channel, so that fluid in said chamber is recirculated back to the main flow channel when the main flow channel is open, and an orientation means for orienting the apparatus in the well. NO20161700 suggests ejectors to remove accumulations of undesired fluids, such that the valve will close at higher volume fractions of unwanted fluids. The apparatus and method disclosed in NO20161700 has proven to function satisfactorily. The flow control elements are configured to operate in a main flow path through the apparatus, and the drag forces acting on the flow control elements are thus sensitive inter alia to Reynolds number.

There is a need for a valve, hereinafter also denoted an AICD, that operates independently of fluid viscosity, local velocity and Reynolds number, and that is also capable of reliably blocking or restricting the unwanted fluid for all flow rates once the volume fraction of the unwanted fluid exceeds a pre-defined limit.

SUMMARY

The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least to provide a useful alternative to prior art.

The object is achieved through features, which are specified in the description below and in the claims that follow.

The invention is defined by the independent patent claims. The dependent claims define advantageous embodiments of the invention.

In a first aspect of the invention there is provided a valve suitable for closing fluid communication between a well and a production string when a content of an undesired fluid in the fluid flow exceeds a predetermined level, the valve comprising:a primary flow channel having a primary inlet through a flow barrier, and a low pressure portion;a secondary flow channel connected to the primary flow channel at the low pressure portion, the secondary flow channel having a secondary inlet through the flow barrier and provided with a flow restrictor;a chamber in connection with the secondary flow channel;a piston arranged in the primary flow channel for opening and closing the primary flow channel, the piston defining a portion of the chamber in connection with the secondary flow channel;an inflow control element movable between a first position and a second position in response to a density of a fluid;
wherein the inflow control element is exposed to the fluid flow upstream of the flow barrier and is arranged to move to the second position and close the secondary inlet when the content of the undesired fluid in the flow upstream of the flow barrier exceeds the predetermined level; and
wherein the closing of the secondary inlet causes an underpressure in the chamber such that the piston is activated and the valve is closed.

By the term “low pressure portion” is meant a portion of the primary flow channel wherein the pressure of a flowing fluid is lower than the fluid pressure upstream of the barrier.

Thus, the position of the piston depends on whether fluid is flowing into the secondary flow channel or not, which flow depends on the content, or volume fraction, of the undesired fluid in the flow upstream of the barrier and a position of the inflow control element with respect to the secondary inlet. By the term upstream is meant fluid “abutting” or being adjacent the barrier.

The operation of the valve according to the invention depends on the density of the fluid flow upstream of the flow barrier only, and is thus independent of fluid viscosity, velocity of the flowing fluid and Reynolds number.

The predetermined level may be set by means of a hydraulic resistance of the secondary flow channel, i.e. a configuration of the apparatus. The secondary inlet of the secondary flow channel forms a fluid inlet of the chamber. The outlet of the chamber is formed by the connection between the secondary flow channel and the primary flow channel. In what follows, said connection between the secondary flow channel and the primary flow channel will also be denoted “pilot hole”. In one embodiment, the pilot hole is arranged at a vena contracta of the primary flow channel. When fluid is flowing through the primary flow channel a fluid pressure at the outlet of the pilot hole will then be lower than the fluid pressure at the secondary inlet through the flow barrier, i.e. in the fluid upstream of the secondary inlet and thus the barrier.

The hydraulic resistance depends inter alia on a configuration of the pilot hole providing the connection between the secondary flow channel and the primary flow channel.

Preferably, a pressure drop through the secondary inlet is smaller than a pressure-drop through the pilot hole. Preferably, the pilot hole is designed so that a discharge coefficient (effective flow area divided by the physical flow area) is substantially independent of the Reynolds number.

The primary inlet may, in the position of use, be arranged at a first elevation, and the secondary inlet may be arranged at a second elevation that is different from the first elevation.

The valve may be an autonomous inflow control device, a so-called AICD, for controlling a fluid flow in, into or out of a production string of a well, the apparatus comprising:a primary flow channel having a primary inlet through a flow barrier, and a low pressure portion;a secondary flow channel connected to the primary flow channel, the secondary flow channel having a secondary inlet through the flow barrier, and a secondary outlet connected to the low pressure portion of the primary flow channel;an outlet for fluid flowing into the passage; anda pressure controlled piston configured to move with respect to a stationary valve seat between an open position wherein the piston does not abut the valve seat and therefore allows fluid flow through the passage, and a closed position wherein the piston abuts the valve seat so that the passage is at least partially blocked;
whereinthe primary inlet is arranged at a first elevation, and the secondary inlet in a position of use is arranged at a second elevation being different from the first elevation;the apparatus further comprising an inflow control element responsive to a density of a fluid, the inflow control element being movable distant from the primary inlet between a first position wherein the inflow control element does not block the secondary inlet, and a second position wherein the inflow control element blocks the secondary inlet for inflow of unwanted fluid; andthe pressure controlled valve is responsive to fluid pressure in the secondary flow path in such a way that the pressure controlled valve is moved to the closed position when the secondary inlet is blocked by the inflow control element.

For a petroleum well, the undesired fluid may typically be water or gas.

In an embodiment where the undesired fluid is water, the secondary inlet may, in the position of use, be arranged at a higher elevation than the primary inlet. In such an embodiment the inflow control device may have a density between the density of water and the density of oil.

In an embodiment where the undesired fluid is gas, the secondary inlet may, in the position of use, be arranged at a lower elevation than the primary inlet. In such an embodiment the inflow control device may have a density between the density of gas and the density of oil.

In an embodiment where the valve is configured for use in a WAG injection well (WAG—Water Alternating Gas), the secondary inlet may, in the position of use, be arranged at a lower elevation than the primary inlet. In such an embodiment the inflow control device may have a density between the density of water and a density of gas at an in situ condition. By in situ condition is meant reservoir pressure and temperature.

The inflow control element may be a float element movable in a path arranged at an upstream side of the flow barrier. The path may extend between the first position and the second position.

There are several advantages of providing such a path.

A first advantage is that the movement of the float element is kept within defined limits. This has the effect that the float element may be kept distant from the primary inlet for all flow regimes that may appear. The float element will thus not be subject to a “mix-phase” that may appear at the primary inlet in the fluid flow upstream of the barrier. Further, the float element will not provide an obstruction to the fluid flowing into the primary inlet.

A second advantage is that the secondary inlet may be arranged at a desired second elevation, and that the float element can be prevented from moving beyond the second elevation even if the fluid would otherwise move the float element beyond the secondary inlet.

The float element may be a ball movable in a path constituted by a guide element, such as for example a cage. The float element may typically be circular, but other shapes are also conceivable, such as non-circular, for example oblong, or disc-shaped, or polygonal.

In an alternative embodiment, the float element may be pivotably connected to an upstream portion of the barrier. In an embodiment where the float element is a disc, such a disc may be arranged in a disk-channel forming part of the barrier itself. Such a channel will then serve the same purpose as the path discussed above. The channel will be in constant fluid communication with the fluid flow upstream of the barrier so that the disc is exposed to the fluid flow upstream of the barrier.

Independent of the type of float element utilized, it must be capable of blocking the secondary inlet when the content of the undesired fluid in the fluid flow upstream of the barrier exceeds the predetermined level.

The piston may be axially movable within a portion of an annulus defined by:an inner tubular body being in fluid communication with the production string;a housing arranged coaxially with and surrounding a portion of the inner tubular body;a downstream barrier arranged within the annulus and axially spaced apart from the flow barrier;
wherein the annulus further comprises a stationary valve seat arranged between the downstream barrier and the flow barrier so that the piston abuts the valve seat when the valve is closed, and the piston does not abut the valve seat when the valve is open.

Such an axially movable piston may be movable with respect to a stationary valve seat typically arranged within in the valve chamber. Preferably, the primary flow channel is substantially a continuation of the flow upstream of the barrier.

The primary flow channel extends between the primary inlet and an outlet for providing fluid communication with a fluid flowing in the inner tubular body wherein the tubular body is in fluid communication with the production string as mentioned above. In what follows, the inner tubular body will also be denoted barrel.

In a basic configuration, the valve according to the invention has only two movable parts; the float element and the axially movable piston. This has the effect that the valve may be very reliable.

The valve seat may comprise a first valve seat element and a second valve seat element axially spaced apart from the first valve seat element. In such an embodiment, a portion of the piston may be movable between the valve seat elements. Said portion of the piston is operatively connected to the rest of the piston. When the valve is in the closed position the piston may abut both valve seat elements. This configuration with two valve seat elements is particularly useful for providing an added closing force to the valve and for providing a re-opening mechanism as will be discussed below.

To provide an added closing force, the valve may be provided with a pressure-controlled mechanism for providing a pressure differential across a portion of the piston when the piston abuts the stationary valve seat, the pressure-controlled mechanism may be responsive to a difference in fluid pressure upstream and downstream of the valve so that a closing force of the valve is added to the piston when said difference in fluid pressure is positive.

The pressure-controlled mechanism may comprise an annular cavity formed between a portion of the piston and the second valve seat element when said piston abuts a downstream face of the second valve seat element, and pressure communication channel passing through the second valve seat element for communicating fluid from the primary inlet to an annulus formed between the second valve seat element and the first valve seat element when the valve is closed.

The valve may be provided with a leakage means for allowing leakage through the valve when the valve is in a closed position.

In one embodiment, the leakage means may be an aperture extending through a portion of the second valve seat element, the aperture providing fluid communication through a portion of the piston and the first valve seat element. The purpose of such a leakage means is to provide a small leakage, typically in the range of 2-20% of a flow capacity of an open valve, through the valve so that an undesired fluid that caused the valve to initially close, is subsequently replaced by a desired fluid that may re-occur upstream of the barrier. Such a situation may occur if undesired fluid, for example water in a near-wellbore region, retreats and is replaced by desired fluid, such as oil. Thus, the leakage means may form part of a re-opening mechanism.

By the term “closing for fluid communication” as stated in the first aspect of the invention, is therefore meant restricting at least a major part of the fluid communication between a well and a production string.

In one embodiment, the fluid flow within the inner tubular body has to be temporarily stopped in order to re-open the secondary inlet in the barrier. In a petroleum well, fluid flow within the inner tubular body is stopped by stopping the production from the production string.

To facilitate re-opening of a closed valve, the valve may be provided with a biasing means configured for facilitating movement of the piston from a position wherein the valve is closed, to a position of the piston wherein the valve is open. The biasing means may be provided by at least one spring. Thus, the biasing means may be used to enforce a re-opening of a closed valve when fluid flow in the inner tubular body is temporarily stopped by stopping the production from the production string.

In some cases, it may be desired to provide a re-opening mechanism that is not dependent on stopping fluid flow within the inner tubular body, typically by stopping production of a petroleum well.

The pressure-controlled mechanism may further comprise a first leakage channel and a second leakage channel for communicating fluid upstream of the flow barrier to the pressure-controlled mechanism. The second leakage channel may be in fluid communication with a third inlet through the flow barrier, wherein the third inlet is arranged to be closed by means of the inflow control element when the content of undesired fluid in the fluid flow upstream of the flow barrier is below the predetermined level. Thus, the first leakage channel may provide a pressure differential across a portion of the piston when the piston abuts the stationary valve seat, and the pressure-controlled mechanism being responsive to a difference in fluid pressure upstream and downstream of the valve so that a closing force of the valve is added to the piston when said difference in fluid pressure is positive.

In a position of use, the first leakage channel may be arranged at an extreme level with respect to the primary inlet, the secondary inlet and the third inlet. For a valve configured for blocking inflow of water exceeding a predefined level in an oil producing well, the first leakage channel may be arranged at a higher level than the primary inlet, the secondary inlet and the third inlet. For such a configuration, the third inlet may be arranged between the level of the primary inlet and the secondary inlet. The effect of this is that when the valve is closed, the oil-water interface will be either at the first leakage channel or the second leakage channel being in fluid communication with the third inlet, depending on the water fraction and on a diameter ratio of the first leakage channel and the second leakage channel. For high water fractions, for example 80%, the interface will be at the first leakage channel, and for low water fractions, for example 20%, the interface will be at the third inlet that is in fluid communication with the second leakage channel.

For this embodiment, like the embodiment discussed above, the pressure-controlled mechanism may comprise an annular cavity formed between a portion of the piston and the second valve seat element when said piston abuts a downstream face of the second valve seat element. The pressure-controlled mechanism may further comprise a pressure communication channel passing through the second valve seat element for communicating fluid from the primary inlet to an annulus formed between the second valve seat element and the first valve seat element when the valve is closed.

The valve may comprise at least one secondary piston being axially movable with respect to the piston of the valve. In such an embodiment, the first leakage channel and the second leakage channel may be in fluid communication via a pressure communication channel influencing a position of the at least one secondary piston. The pressure communication channel may be in fluid communication with the third inlet of the barrier.

Thus, the secondary piston is configured to control a fluid communication and a pressure in the pressure-controlled mechanism and thus a position of the piston.

The first leakage channel and the second leakage channel may be merged or interconnected into one common channel prior to entering the pressure-controlled mechanism. A total leakage flow through a valve being in a closed position is thus controlled by the flow area of the common channel. Preferably, the flow area of the common channel is less than a sum of the flow area of the first leakage channel and the second leakage channel. The diameter ratio of the first leakage channel and the second leakage channel influences the fraction of the undesired fluid, for example water, at which the valve will re-open from a closed position.

Preferably, the valve is designed to re-open at a fraction of undesired fluid that is significantly lower than a fraction of undesired fluid where the valve closes. This has the effect of at least reducing possibility of the valve toggling between a closed position and an open position. By the term “significantly” is meant more than 5% difference.

The valve may further comprise a secondary inflow control element located in the fluid flow upstream of the flow barrier, and a further secondary inlet through the flow barrier and in fluid communication with the secondary flow channel. The further secondary inlet may be closable by the secondary inflow control element and arranged to open the further secondary inlet when the fluid upstream of the barrier comprises drilling fluid, and to close the further secondary inlet when the fluid upstream of the barrier does not comprise drilling fluid. The secondary inflow control element may have a density higher than the density of a desired fluid and the undesired fluid, but lower than the density of the drilling fluid. This has the effect that a drilling fluid that typically may exist in a well after the well has been drilled and completed, can be produced out of the well without being blocked or restricted by the valve.

The secondary inflow control element may be arranged in a similar manner as discussed above for the inflow control element for controlling inflow of fluid into the secondary inlet, i.e. movable for example in a path extending between a first position and a second position. Preferably, the path of the secondary inflow control element is different from the path of the inflow control element for the desired/undesired fluid.

Also described herein is a diverting device for controlling inflow of fluid to an inflow control device such as for example the valve according to the first aspect of the invention. The diverting device is arranged upstream of the inflow control device, such as the valve. The diverting device has an upstream end portion and a downstream end portion, and:a flow through conduit for allowing fluid communication from a flow through inlet at the upstream end portion, to the downstream end portion;a bypass conduit for allowing fluid communication from a bypass inlet at the upstream end portion, to an outlet arranged in fluid communication with an aperture in a wall of the production string, the outlet being arranged between the upstream end portion and the downstream end portion of the diverting device, the flow through inlet being spaced apart from the bypass inlet; andat least one diverting device inflow control element responsive to a density of a fluid;
wherein the diverting device inflow control element is located in the fluid flow at an upstream portion of the device and is arranged to block one of the flow through inlet and the bypass inlet depending on the density of the fluid at the upstream portion of the diverting device.

In a second aspect of the present invention there is provided a system for controlling inflow of a fluid from a well and into a tubular body forming part of a production string. The system may comprise at least one valve according to the first aspect of the invention. The system may further comprise:a diverting device arranged upstream of at least one of the at least one valve, wherein the diverting device has an upstream end portion and a downstream end portion, and:a flow through inlet in the upstream end portion;a flow through conduit for allowing fluid communication from a flow through inlet at the upstream end portion, to the downstream end portion;a flow through conduit for allowing fluid communication from the flow through inlet to the downstream end portion;a bypass inlet in the upstream end portion;a bypass conduit for allowing fluid communication from the bypass inlet to an outlet arranged in fluid communication with an aperture in a wall of the production string, the outlet being arranged between the upstream end portion and the downstream end portion of the diverting device, the flow through inlet being spaced apart from the bypass inlet; andat least one diverting device inflow control element responsive to a density of a fluid;
wherein the diverting device inflow control element is located in the fluid flow at an upstream portion of the device and is arranged to block one of the flow through inlet and the bypass inlet depending on the density of the fluid at the upstream portion of the diverting device.

The at least one diverting device inflow control element may comprise:a diverting device first inflow control element arranged to block the flow through inlet when the fluid is drilling fluid;a diverting device second inflow control element arranged to block the bypass inlet when the fluid is oil, water and/or gas;
wherein the first diverting device inflow control element is arranged in a first path, and the diverting device second inflow control element is arranged in a second path being separate from the first path.

In the position of use, the flow through inlet may be arranged at a higher elevation than the bypass inlet, and the diverting device inflow control element is one element movable in a path extending between a first position and a second position, wherein the inflow control element in the first position is configured to block the flow through inlet, and in the second position is configured to block the bypass inlet.

The diverting device inflow control element may have a density between that of drilling fluid and that of water. This has the effect that fluid is allowed through the flow through conduit and to the subsequent valve(s) when the diverting device is exposed to a fluid having a density being less than that of the inflow control element.

The diverting device may be provided with at least one leakage channel for allowing a leakage flow through the diverting device. This has the effect of continuously displacing “old” fluid with “new” fluid, such that the system can respond to changes in incoming fluid composition.

Hereinafter, the diverting device is also denoted a “cleanup module”. The cleanup module may be arranged upstream of a valve configured for undesired fluid being water, hereinafter also denoted “water module”, or a valve configured for undesired fluid in the form of gas, hereinafter also denoted “gas module”. In one embodiment the cleanup module is arranged upstream of a water module and a gas module arranged in series with the water module.

In some wells, drilling fluid is displaced from the reservoir section prior to cleanup and before socalled “swell packers” have been expanded. A clean fluid, such as for example a base oil, is then pushed down a basepipe that may be in fluid communication with the inner tubular body disclosed herein, to TD (Total Depth) and back up in an annular space between a lower completion and a sandface. A person skilled in the art will appreciate that the sandface is the boundary between the well bore and the reservoir. The drilling fluid is then pushed up into a cased annulus. In order to ensure an efficient process whereby all the drilling fluid is displaced from the reservoir section, it is important to avoid backflow through the valves as this will represent short-circuits for the flow. Instead, temporary check valves can be installed in the cleanup module to prevent backflow and instead force the flow all the way to TD before returning in the annulus. The check valve can be made temporary by using a material that dissolves after some time of oil production. Thus, it may be advantageous if the cleanup module is provided with a check valve.

The system may be further provided with an ICD module (ICD—Inflow Control Device) on the downstream side of the valve(s). The purpose of the ICD module is to create a minimum pressure drop across the valve when the valve is open in order to enforce a more uniform inflow profile from the reservoir, which in turn may contribute to delayed gas and/or water breakthrough and therefore a more favourable reservoir drainage.

The ICD may be a single orifice with a small diameter, or it may comprise a plurality of parallel orifices with different sizes, where only one orifice is selected by configuring the ICD module manually prior to installation, or using a downhole prior art tool to rotate the ICD module to the desired position from the inside after installation. The ICD module might also have a permanent check valve that prevents reversed flow through the ICD, gas module and water module.

The system discussed above may also comprise a fail-safe mechanism, e.g. in the form of a sliding sleeve arranged inside the inner tubular body. Such a sliding sleeve may for example be pulled open from the inside by a well tool. The fail-safe mechanism may also be an integral part of the cleanup module or a separate module placed upstream of the cleanup module.

As will be discussed in more detail below, the present invention may also be utilized in WAG injection wells (WAG—Water Alternating Gas). In order to obtain a substantial uniform outflux profile along the reservoir section when gas is injected, it is desirable for some WAG injection wells to restrict the outflow of gas more than the outflow of water.

In a third aspect of the invention, there is provided a method for controlling fluid flow in, into or out of a well. The method may comprise the steps of:mounting a valve according to the first aspect of the invention as part of a well completion string prior to inserting the string in the well;bringing the well completion string into the well;orienting the valve within the well; andflowing fluid in, into or out of the well.

The valve may for example be oriented by using an orientation means disclosed in Norwegian Patent application NO 20161700.

The method may further comprise:arranging a diverting device upstream of at least one of the at least one valve, the diverting device having:an upstream end portion and a downstream end portion;a flow through inlet in the upstream end portion;a flow through conduit for allowing fluid communication from the flow through inlet to the downstream end portion;a bypass inlet in the upstream end portion;a bypass conduit for allowing fluid communication from the bypass inlet to an outlet arranged in fluid communication with an aperture in a wall of the production string, the outlet being arranged between the upstream end portion and the downstream end portion of the diverting device, the flow through inlet being spaced apart from the bypass inlet; andat least one diverting device inflow control element responsive to a density of a fluid;
wherein the method comprises locating the diverting device inflow control element in the fluid flow at the upstream portion of the diverting device and arranging the inflow control element to block one of the flow through inlet and the bypass inlet depending on the density of the fluid at the upstream portion of the diverting device.

DETAILED DESCRIPTION OF THE FIGURES

Positional indications such as for example “above”, “below”, “upper”, “lower”, “left”, and “right”, refer to the position shown in the figures.

In the figures, same or corresponding elements are indicated by same reference numerals. For clarity reasons some elements may in some of the figures be without reference numerals.

A person skilled in the art will understand that the figures are just principle drawings. The relative proportions of individual elements may also be strongly distorted.

In the figures, the reference numeral1denotes a valve according to the present invention.

FIG. 1shows a typical use of the valve1in a well completion string CS arranged in a substantially horizontal wellbore or well W penetrating a reservoir F. The well W is in fluid communication with a rig R floating in a surface of a sea S. The well W comprises a plurality of zones separated by packers PA, for example so-called swell packers, as will be appreciated by a person skilled in the art. A person skilled in the art will understand that the well W may alternatively be an onshore well.

InFIG. 1, one valve1is shown for between pairs of packers PA. However, it should be clear that two or more valves1will typically be arranged between each pair of packers PA

FIG. 2shows a typical arrangement of the valve1in a portion of a well completion string CS. The valve1is positioned between a basepipe P and a sandscreen SS. InFIG. 2, the valve1according to the invention is indicated with broken lines. An inflow portion of the valve1is denoted I.

The valve1may form part of a so-called pipe stand that may have a typical length of approximately 12 meters, for example. However, the valve1may also be arranged in a separate pipe unit having for example a length of only 40-50 centimeters. Such a unit may be configured to be inserted between two subsequent pipe stands.

The valve1according to the invention is orientation dependent. In the figures, this is indicated by a g-vector.

In order to explain a basic principle of the valve1according to the invention, reference is first made toFIGS. 3a-3f. It should be emphasized that the primary purpose ofFIGS. 3a-3fis to explain how a position of an axially movable piston is activated when an undesired fluid, here in the form of water, exceeds a predetermined level. It should also be noted that required elements of the valve, such as a valve seat, has been left out. However, a more detailed description of embodiments of the valve1are disclosed inFIGS. 4aet seq.

InFIGS. 3a-3f, the valve1comprises a primary flow channel3having a primary inlet5through a flow barrier7. The primary flow channel3is configured for influencing a pressure of the fluid through the channel3. In the embodiment shown, the primary flow channel comprises a venturi with a vena contracta portion5′ for providing a low pressure portion.

The valve1further comprises a secondary flow channel9having a secondary inlet11in the flow barrier7, and a pilot hole in the form of a secondary outlet13in fluid communication with the vena contracta portion5′, i.e. the low pressure portion of the primary flow channel3.

A chamber17is arranged between the secondary inlet11and the secondary outlet13of the secondary flow channel9. Thus, the chamber17forms part of the secondary flow channel9.

Although not specifically shown inFIGS. 3a-3fit should be clear that a hydraulic resistance of the secondary outlet13or the pilot hole is larger than the hydraulic resistance of the secondary inlet11.

The secondary outlet13is provided with a funnel-shaped inlet portion. Such an inlet portion is favourable as the effective flow area then becomes substantially the same as the smallest cross-section of the secondary outlet13. A discharge coefficient of the secondary outlet13(the pilot hole) will then be close to one, thereby removing its sensitivity to Reynolds number.

An axially movable piston20has a first piston portion22exposed to the fluid in the chamber17, and a second piston portion24exposed to a fluid in the primary flow channel3downstream of the venturi. In this way, an axial position of the piston20is influenced by any pressure differential across the piston20. The piston20is operatively connected to a valve seat (not shown) so that the primary flow channel3can be closed.

The valve1further comprises an inflow control element30responsive to a density of an undesired fluid, here in the form of water. The inflow control element30is located in the fluid flow upstream of the barrier7and is arranged to close the secondary inlet11when the content of the undesired fluid in the flow upstream of the barrier7exceeds a predetermined level. The inflow control element30is, in the embodiment shown, movable in a path32constituted by a cage-like arrangement, between a first position wherein the inflow control element30does not block the secondary inlet11, and a second position wherein the inflow control element30does block the secondary inlet11.

Both in the first position and the second position the inflow control element30is located distant from the primary inlet5of the primary flow channel3. Thus, the inflow control element30will not be subject to a stratified flow that may occur at the primary inlet5, and the inflow control element30will not “disturb” or provide an obstruction to the fluid flowing into the primary flow channel3.

InFIG. 3a, oil only is drained from for example the reservoir F as shown inFIG. 1. Oil is therefore flowing into the primary flow channel3via the primary inlet5and into the secondary flow channel9via the secondary inlet11which is open, i.e. not blocked by the inflow control element30which in the embodiment shown has a density between that of oil and that of water.

Upstream of the barrier7there is a fluid having a high pressure HP. In the vena contracta portion5′ of the primary flow channel3, there will be a low pressure LP. In a producing well being in fluid communication with a downstream portion of the primary flow channel3, a partial pressure recovery will exist downstream of the venturi that comprises the vena contracta portion5′. The partial pressure recovery will result in a medium fluid pressure MP downstream of the venturi. Due to the hydraulic resistance of the secondary outlet13being larger than the hydraulic resistance of the secondary inlet11, a high pressure HP will exist also in the chamber17forming part of the secondary flow channel9. Thus, there will be a pressure difference between the piston surfaces22,24which urges the piston20to the left. In this position, the piston20does not close the primary flow channel3as will be explained in more details fromFIGS. 4aet seq.

The terms high pressure, medium pressure and low pressure denote mutual relative fluid pressures upstream of and within the valve1.

In an oil producing well W, a person skilled in the art will appreciate that the well is likely to produce also water.

InFIG. 3b, a so-called water-cut WC has risen to about 75%. InFIG. 3b, the valve1is configured to close with a water cut higher that 75%. Thus, a mixture of all the water and a portion of the oil is flowing through the primary flow channel3as indicated, while oil is flowing through the secondary flow channel9. Since all the water is flowing through the primary flow channel3, the inflow control element30is still in the first, non-blocking position.

The pressure regime in the situation shown inFIG. 3bis similar to that discussed with regards toFIG. 3a. Thus, the valve1is open.

FIG. 3cshows a situation wherein the inflow of water has just passed a predetermined level. The predetermined level may for example be a water content of 90%. In this situation, all the water flow upstream of the valve1is larger than a flow through the primary channel3. Thus, the water will ascend very quickly, typically within a few seconds, and bring the inflow control element30upwards. The inflow control element30will therefore move from the first position to the second position where it blocks the secondary inlet11.

The pressure regime in the situation shown inFIG. 3cis similar to that discussed with regards toFIG. 3a. Thus, the valve1is open.

InFIG. 3d, the inflow control element30has just reached the second position and blocks the secondary inlet11. The pressure within the chamber17will quickly (instantaneously) be reduced from the high pressure HP to a low pressure LP shown inFIG. 3e. Due to the medium pressure MP in the portion of the primary flow channel3being downstream of the venturi and the second piston portion24, the piston20will be axially displaced in an upstream direction, i.e. towards the right as indicated by the arrow at the first piston portion22, and close the valve1. Again, further features of the valve1causing closing of the valve1will be explained below.

When the valve1has been closed, as shown inFIG. 3f, the pressure regime within the valve will be equalized with the pressure upstream of the valve1, including the pressure across the inflow control element30.

The above should explain the basic feature of the valve1according to the present invention.

In what follows, the invention will be explained in more details.

FIGS. 4a-4fshow an example of a basic configuration of a valve1according to the present invention. The valve1comprises similar elements as discussed above with regards toFIGS. 3a-3f. Elements discussed inFIGS. 3a-3fwill therefore be denoted in definite form in what follows.

The valve1is designed for closing inflow of a fluid from the well W shown inFIG. 1. The valve1may typically be arranged as shown in principle inFIG. 2. In the embodiment shown inFIG. 4a, the valve is in an open position and configured for blocking inflow of an undesired fluid in the form of water exceeding a predetermined level.

The valve1is arranged in an annular space defined between an inner barrel P, such as for example a basepipe that may form part of or be connected to a production string PS of a petroleum well W, an outer housing H enclosing a portion of the inner barrel P, an upstream barrier7and a downstream barrier7′.

The barrel P is provided with an aperture35for allowing fluid communication between the primary flow channel3and the production string. The aperture35is arranged downstream of the second piston portion24.

The valve1shown inFIGS. 4a-4fcomprises a hollow, annular piston20axially movable in a portion of the annular space, between a first position and a second position.

The second piston portion24is provided with an opening24′ forming part of the primary flow channel3.

The valve1is further provided with a valve seat40in the form of an annular wall40protruding from an inner surface of the housing H. The valve seat40is arranged within a hollow portion25of the piston20so that the second piston portion24of the piston20does not abut the wall40when the piston20is in the first position, but abuts the wall40when the piston20is in the second position. The opening24′ in the second piston portion24is blocked by the wall40when the piston20is in the second position. In what follows, the piston portion24will also be denoted piston surface24. Fluid flow through the primary flow channel3is prevented when the opening24′ is blocked. The valve1is closed when there is no flow through the primary flow channel3.

As best seen inFIG. 4a, the chamber17which forms part of the secondary flow channel9, and a portion of the piston20encloses an axial portion of the venturi portion of the primary flow channel3. The venturi portion of the primary flow channel3comprises the primary inlet5, the vena contracta5′, and an expansion or diffuser section5″. The primary inlet5is arranged in a lower portion of the flow barrier7facing an inlet I of the valve1.

The piston20encloses a portion of the expansion section5″ of the venturi portion of the primary flow channel3.

InFIG. 4avarious stopping mechanisms and seals S are configured for defining end positions for the axial movements of the piston20, and for preventing leakage around the piston20and venturi whenever the piston20is in fully open or fully closed position, which will be the case during a majority of the operational lifetime of the valve1. In order to avoid excessive leakage around the piston20and/or venturi, which might jeopardize the reliability of the valve, small clearances and/or slide bearings are preferably utilized.

InFIG. 4bthe valve1is seen from right to left inFIG. 4aand shows that the secondary inlet11of the secondary flow channel9is arranged at a higher elevation than the primary inlet5of the primary flow channel3.

The inflow control element30is in the form of a ball30which in the embodiment shown inFIG. 4a-4f, has a density between that of oil and water.

FIG. 4aandFIG. 4bshow a situation wherein the fluid flow upstream of the valve1corresponds to that discussed above in relation toFIGS. 3a-3b. Thus, when oil flows through the valve1, the inflow control element30, here the ball30, will reside at the bottom of the path32. The path32will hereinafter also be denoted cage32. When the ball30resides at the bottom of the cage32, the secondary inlet11of the secondary flow path9is open to flow. Thus, the fraction of the total flow rate that flows in the secondary flow path9is determined by the diameter of the vena contracta5′ and the pilot hole or secondary outlet13that is in fluid communication with the vena contracta5′. As indicated inFIG. 4ashowing the secondary outlet13and for exampleFIG. 4bshowing the secondary inlet11, a diameter of the secondary inlet11is much larger than the diameter of the secondary outlet13such that a hydraulic resistance of the secondary outlet13is larger than the hydraulic resistance of the secondary inlet11. In one embodiment, the hydraulic resistance of the secondary outlet13is about 200 times larger than the hydraulic resistance of the secondary inlet11. Thus, most of the pressure drop along the secondary flow path9takes place across the secondary outlet13. As a result, the pressure acting on the first piston surface22facing the chamber17is substantially the same as the inlet pressure of the valve1.

When the water fraction is low or moderate, for example in the range of 0%-80%, the oil-water interface level of the incoming stratified flow will be located at the primary inlet5of the primary flow channel3. This means that all the water will follow a flow path through the venturi, whereas the oil flow will be split between the primary inlet5of the primary flow channel3and the secondary inlet11of the secondary flow channel9.

As the water fraction increases, for example above 80%, a point will be reached where the flow rate of the water fraction exceeds a flow capacity of the venturi. The oil-water interface level will then ascend from the primary inlet5to the secondary inlet11. As the inflow control element30, here in the form of a ball30, is free to move within the cage32, it will follow the oil-water interface upward and eventually block the secondary inlet11, as illustrated inFIGS. 4cand 5a. Once this situation occurs, the pressure within the chamber17and thus against the first piston surface22, will be quickly reduced from a pressure being higher than the pressure against the second piston surface24, to a pressure against the first piston surface22being lower than the pressure against the second piston surface24. Thus, the piston20will move from the position shown inFIGS. 4aand 5a, via an intermediate position shown inFIG. 5bto a position shown inFIG. 5cwherein the piston20has moved to the second position (to the right) and thereby closed valve1. When the valve1has been closed, the pressure regime in all parts of the valve1will be equalized with the pressure upstream of the valve1, including the pressure across the inflow control element30.

InFIG. 5a, the valve1is provided with an optional rod21(indicated by dotted lines) protruding from the first piston surface22towards a portion, for example a centre portion, of the secondary inlet11. The purpose of the rod21is to push the inflow control element30, here the ball30, away from secondary inlet11. As the piston20moves from an open position, as shown inFIG. 5a, to closed position, seeFIG. 5c, the rod21will approach the ball30. Right before the piston20reaches its closed position and the sealings S start to be activated, an end portion of the rod21moves through a portion of the secondary inlet11and abuts against the ball30which is then urged away from the periphery of the secondary inlet11. The optional rod21represents a mechanical supplement or an alternative to a pressure equalization mechanism that will be discussed below. It should be noted that if the valve1is provided with the annular wall71indicated inFIG. 4a, such an annular wall71must be provided with an aperture (not shown) for allowing axial movement of the optional rod21.

With the secondary inlet11blocked by the ball30, all the flow is forced through the venturi, which means that the oil-water interface level will for continuity reasons be forced back down to the venturi. The ball30, however, will still remain at the secondary inlet11because of the low pressure within the chamber17and a high pressure at the inlet I.

During normal production of reservoir fluids through the valve1, there is a risk that particles and fines may settle in the vicinity of the piston20. By vicinity is meant upstream of and in the narrow annular spaces defined by the piston20and the barrel P and housing H. Settled particles and fines may restrict or even prevent the piston from moving. This risk that the piston20being restricted or prevented from moving may be reduced by providing a fixed wall71on an upstream side of the piston20. Such wall71, indicated by dotted lines inFIG. 4a, should extend radially from the outer surface of the inner barrel P to the inner surface of the housing H. The wall71shown inFIG. 4awill protect the piston20from the surrounding flow and particles. The wall71is provided with a tortuous channel72running through the wall71. The tortuous channel72ensures pressure communication, but no flow, except when the piston20is moving and fluid needs to be communicated through the walls. The content (amount) of fines and particles associated with this fluid communication is negligible. A similar principle may be used for reducing a risk that particles and fines may settle in the vicinity of a downstream side or the piston20.FIGS. 4d-4fshow various cuts through the valve shown inFIG. 4a.

The limiting water fraction above which the valve closes, depends on the diameter ratio of the secondary outlet13and vena contracta5′. If it is preferred that the valve1closes at a high water cut, for example above 80%, the secondary outlet13should have a small diameter, such as for example 1 mm. If a small diameter represents an unacceptable risk of particle blockage, the secondary outlet13can alternatively be replaced by a long circular tube with the smallest acceptable diameter. By making the tube sufficiently long, for example by winding it helically around the barrel P, the limiting water fraction can become very close to 100%.

The valve1shown inFIGS. 4a-4fmay also be configured for use in gas fields where the production facilities, for example a rig, has a limited capacity for handling liquid. By providing an inflow control element30having a density between that of gas and oil instead of a density between water and oil as discussed above, the valve1can be used to block or restrict both water and oil (condensate).

InFIGS. 6a-6c, the valve1is provided with a pressure-controlled mechanism for providing a pressure differential across a portion of the piston20when the piston20abuts the valve seat40. The pressure-controlled mechanism is responsive to a difference in fluid pressure upstream and downstream of the valve1, so that a closing force of the valve1is added to the piston20when said difference in fluid pressure is positive. A purpose of the pressure-controlled mechanism is to facilitate in keeping the valve1closed.

In the embodiment shown inFIG. 6a, the pressure-controlled mechanism comprises an annular cavity42formed in a portion of the second piston portion24facing the valve seat40. However, it should be clear that the annular cavity42in an alternative embodiment could be formed in both the second piston portion24and the valve seat40, or in the valve seat40only. The point is to create an annular cavity42between the valve seat40and the second piston portion24when abutting each other.

The annular cavity42is in fluid communication with the aperture35in the barrel P via a piston conduit240protruding in an axial downstream direction from the second piston portion24. The piston conduit240extends through an aperture in an annular additional or second valve seat element40′. When the piston20is in its closed position as shown inFIG. 6a, a distant end portion242of the piston conduit240abuts a periphery of the aperture in the additional valve seat element40′. As indicated inFIG. 6a, the periphery is provided with a sealing element.

The valve seat40, hereinafter also denoted first valve seat element40, is in the embodiment shown inFIG. 6aprovided with two channels; a leakage channel44configured for providing fluid communication between the venturi and the annular cavity42, and a pressure communication channel46for providing fluid communication between the venturi and an annular conduit chamber48defined by the barrel P, the housing H, the additional valve seat element40′, the second piston portion24and a portion of the first valve seat element40.

The purpose of the piston conduit240is to provide a pressure within the cavity42that is lower than the pressure within the conduit chamber48. Such a pressure differential will arise due to the fact that the cavity42is in fluid communication with the fluid flowing within the barrel P, while the fluid pressure within the conduit chamber48is in fluid communication with the high-pressure fluid at the inlet I of the valve1. Thus, the pressure differential will result in a net pressure force on the piston20in an upstream direction, which increases the pressure toward the first valve seat element40and the additional or second valve seat element40′.

The purpose of the leakage channel44is to make the valve1capable of re-opening if the water for example in a near-wellbore region retreats and is replaced by oil. The leakage channel46ensures that old fluid, in this example water, is continuously displaced by new fluid from the reservoir.

If new fluid, such as oil comes back and leaks through a closed valve1, the water that caused the ball30to block the secondary inlet11, as shown inFIGS. 4band 5a, will eventually be drained through the leakage channel44. If production is then stopped temporarily such that the pressure across the valve1equalizes and the ball30falls down, one or more springs23can be used to enforce re-opening of the valve.

InFIG. 6a, a biasing means in the form of one or more springs49(one shown inFIG. 6a) is provided within the chamber17. The spring49is connected to the first piston portion22and to a downstream face of the barrier7. The purpose of the spring49is to facilitate a re-opening of the valve1by providing a force in a downstream direction, i.e. towards left inFIG. 6a. It should be emphasized that the spring force is relatively small, and of course smaller than a total closing force of the valve1.

The re-opening mechanism described in relation toFIG. 6a, may require pressure equalization across the valve. Such a pressure equalization will typically occur during for example a production shut down by preventing fluid flow within the barrel P.

By providing an inflow control element30having a density between that of gas and oil instead of a density between water and oil as discussed above, the valve1can be used to block or restrict both water and oil (condensate) when producing gas from a gas field where the production facilities, for example a rig, has a limited capacity for handling liquid.

However, it may be advantageous to provide a valve1that is configured for re-opening once the fraction of undesired fluid drops below a predetermined limit, even if there is a pressure difference across the valve. One embodiment of such a valve1that is configured to re-open “on the fly” is shown inFIGS. 7a-7g.

FIG. 7ais a cross-sectional view of the alternative embodiment of the valve1seen from the same position as inFIG. 4b, i.e. across the inlet I of the valve1. The valve1shown inFIG. 7adiffers from the valve1shown inFIG. 4b.

A first difference is that the barrier7is provided with a third inlet50. The third inlet50is additional to the primary inlet5and the secondary inlet11. In the embodiment shown, the third inlet50is arranged in the path32of the inflow control element30and configured to be closed by the inflow control element30when this is in the first, or lower, position.

When oil flows through the valve1, the inflow control element30will, due to its density in the embodiment shown being between that of oil and that of water, be located in its lower portion of the path32, i.e. in the first position. The open or unblocked secondary inlet11allows flow through the secondary flow path9, as discussed above.

When the water fraction increases, and the oil-water interface level ascends from the primary inlet5to the secondary inlet11(for example as indicated inFIG. 3c), the ball30will move along with said interface and finally block the secondary inlet11and cause the piston20to move and close the valve1, as shown inFIGS. 5band5c.

A second difference from the valve1shown inFIG. 4b, is that a first leakage channel52extends through a top portion of the barrier7. As seen inFIG. 7b, the first leakage channel52is in fluid communication with the annular cavity42of the pressure-controlled mechanism. The first leakage channel52replaces the leakage channel44for allowing leakage through the valve seat40shown inFIG. 6a.

FIG. 7cis a view through I-I ofFIG. 7a. The valve1is further provided with a second leakage channel54connected to and protruding axially from an inner surface of the second piston portion24towards the third inlet50arranged in a portion of the barrier7.

The second leakage channel54forms part of the axially movable piston20and moves together with the piston20. The second leakage channel54is provided with apertures extending radially from end portions of the leakage channel54. At an upstream end portion, the second leakage channel54is provided with an end cap56. The purpose of the end cap56will be explained below.

The third inlet50is provided with a channel50′ extending in an axial direction downstream of the third inlet50. When the valve1is closed as shown inFIG. 7c, a downstream or left end portion of the channel50′ abuts, via seals, the second end portion24of the piston. When the valve1is in this closed position, the cavity42is in fluid communication with fluid flow upstream of the barrier7via the third inlet50, the channel50′, a clearance between the end cap56, the radially extending apertures in the second leakage channel54, and the channel54itself. InFIG. 7c, the fluid communication path is indicated by a dotted line D. Thus, the leakage channel54is open when the valve1is closed.

InFIG. 7d, the valve1is in the open position. The end cap56, which is connected to an end portion of the second leakage channel54operatively connected to the piston20as explained above, sealingly abuts an inclined inner wall portion of the channel50′. A fluid communication between the channel50′ and the second leakage channel54is thereby prevented. Thus, the leakage channel54is closed when the valve1is open.

From the above it should be clear that when the valve1is closed, both the first leakage channel52and the second leakage channel54provide fluid communication between the fluid upstream of the barrier7, i.e. the inlet I of the valve1, and the annular cavity42. Also, when the valve1is closed, the fluid pressure across the inflow control element30in the secondary inlet11, will be equalized.

When said pressure is equalized, the inflow control element, here the ball30, is not prevented from moving within the path32.

When the valve1is closed, the oil-water interface will reside either at the first leakage channel52or at the second leakage channel54, depending on the water fraction and on the diameter ratio of the two leakage channels. For high water fractions, such as for example 80%, the interface may be at the first (upper) leakage channel52, and for low water fractions the interface may be at the second (lower) leakage channel54being in fluid communication with the third inlet50. The water fraction below which the interface moves from the upper to the lower channel depends on the diameter ratio of the two leakage channels52,54, or the equivalent diameter ratio of whatever apertures or flow restrictions that may constitute the smallest cross-sectional flow area along each of the leakage channels52,54. If the upper leakage channel52has larger diameter than the lower leakage channel54, the oil-water interface will tend to reside at the upper leakage channel52, causing the valve1to re-open at a high water fraction, and vice versa.

The channel50′ connected to the third inlet50is provided with apertures58for providing fluid communication between the channel50′ and a pressure communication channel60shown inFIGS. 7c-7e. As indicated inFIG. 7e, the pressure communication channel60extends along the path32of the inflow control element30.

If oil comes back and the water fraction drops below the predetermined limit mentioned above, the oil-water interface will descend to the third inlet50and bring the ball30with it. The ball30then blocks third inlet50. This creates a low pressure in the channel50′ behind the ball30. This low pressure propagates via apertures58though the pressure communication channel60, to a secondary piston62shown inFIGS. 7fand 7gwhich are a view through K-K inFIG. 7e. In the embodiment shown inFIG. 7e, the valve1comprises two secondary pistons62arranged along the path32. It should be noted that in an alternative embodiment, the valve1may comprise only one or more than the two secondary pistons62shown.

The secondary piston62is axially movable between an extended position and a retracted position in a piston chamber63provided in a portion of the piston20, as shown inFIGS. 7fand 7g, respectively. The piston chamber63is in fluid communication with the pressure communication channel60.

The secondary piston62is provided with a downstream end surface64, a downstream intermediate surface65, an upstream end surface66and an upstream intermediate surface67. The upstream surfaces66,67are within the piston chamber63and are thus influenced by the fluid pressure in the pressure communication channel60. In the extended position, seeFIG. 7f, the downstream end surface64of the secondary piston62abuts an opening41of the annular wall or valve seat40. When the valve1is closed, the downstream end surface64of the secondary piston62is subject to the fluid pressure within the cavity42. The downstream intermediate surface65is subject to fluid pressure within the hollow portion25of the piston20, independent of the axial position of the secondary piston62.

Continuing the discussion above where oil comes back, the low pressure in the channel50′, see for exampleFIG. 7d, propagates though the pressure communication channel60and into the piston chamber63. With low pressure exerted on the upstream end surface66and the upstream intermediate surface67, and also on the downstream end surface64being subject to the low pressure within the cavity42, and with high pressure exerted on the downstream intermediate surface65, there will be a net pressure force acting on the secondary piston62in the upstream direction, causing it to move axially from the position shown inFIG. 7fto the position shown inFIG. 7gwherein fluid from the primary flow channel3flows to the low-pressure cavity42as indicated by arrows.

The low-pressure cavity42is in communication with the piston conduit240extending through an aperture in the annular additional valve seat element40′ as shown inFIG. 6a.

With flow through the venturi portion of the primary flow channel3, the pressure will become lower on the downstream portion24than on the upstream portion22the piston20. Because of this press sure differential across the piston20, the piston20will move axially in the downstream direction and thus open the valve1, as discussed above. In the configuration shown inFIGS. 7fand 7g, an open valve1will cause the at least one secondary piston62to be brought back to an original closed position, i.e. a retracted position.

When the piston20is in fully open position, the leakage channel54will be blocked by the end cap56abutting the inclined inner wall portion of the channel50′. A blocked leakage channel54will cause the pressure across the ball30to be equalized, such that the ball30, in the embodiment shown, is free to move upward if the water fraction once again increases and the oil-water level ascends.

In order to avoid a too high leakage flow rate through a closed valve1, the two leakage channels52,54may be merged into one common channel (not shown) before entering the low-pressure cavity42. A diameter of the merged leakage channel will determine the total leakage flow rate, whereas the diameter ratio of channel first leakage channel52and the second leakage channel54will determine the water fraction below which the valve1re-opens. The valve1will normally be designed to re-open at a water fraction significantly lower than the water fraction where it closes in order to prevent a situation where the valve1continuously toggles between closed and open position. By significantly lower is meant for example 10%.

By providing an inflow control element30having a density between that of gas and oil instead of a density between water and oil as discussed above, the valve1can be used to block or restrict both water and oil (condensate) when producing gas from a gas field where the production facilities, for example a rig, has a limited capacity for handling liquid.

The embodiments of the present invention discussed above are examples of designs suitable for achieving the desired properties of the valve1. However, numerous alternative designs are possible.

For example; InFIGS. 8aand 8b, the secondary piston62shown inFIGS. 7fand 7ghas been replaced by a fixed wall62′. Further, in the embodiments shown inFIGS. 4a, 5a-5c, 6a, 7b, the venturi portion of the primary flow channel3is provided with an expansion section5″. However, in the alternative embodiment shown inFIG. 8a, the expansion section5″ shown in previous figures, has been omitted and replaced by a straight pipe51. Thus,FIG. 8aillustrates an alternative embodiment of the valve1shown inFIG. 7b.FIG. 8billustrates an alternative embodiment of the valve1shown inFIG. 7c.

When a valve1comprising the features shown inFIGS. 8aand 8b, is water-filled, the ball30will block the secondary inlet11, and the upstream portion22of the piston20will be exposed to the low pressure in vena contracta5′ via the secondary outlet or pilot hole13, whereas the pressure communication channel60within the piston20will be exposed to the full inlet pressure through the apertures58in the channel50′. A net force will therefore push the piston20in the upstream direction to the position shown inFIGS. 8aand 8b, and thereby close the valve1. If oil comes back and displaces the water through the leakage channels52and54shown inFIGS. 8aand 8b, respectively, the ball30will descend along its path32and finally block the third inlet50. The piston20will then be exposed to the inlet pressure on the upstream side22and to the then low pressure within the pressure communication channel60, causing the piston20to move in the downstream direction and re-open the valve1.

By providing an inflow control element30having a density between that of gas and oil instead of a density between water and oil as discussed above, the valve1can be used to block or restrict both water and oil (condensate) when producing gas from a gas field where the production facilities, for example a rig, has a limited capacity for handling liquid

In the embodiments discussed above in relation toFIGS. 4a-8b, and in the general principle of the invention shown inFIGS. 3a-3f, the valve1is configured for being responsive to an undesired fluid in the form of water such that the valve1closes when the content of water in the flow upstream of the barrier7exceeds a predetermined level. However, the valve1may in an alternative embodiment be configured for being responsive to an undesired fluid in the form of gas such that the valve1closes when the content of gas in the flow upstream of the barrier7exceeds a predetermined level.

The valve1shown inFIGS. 9aand 9bis configured for being responsive to gas, and the valve1corresponds substantially to the valve1shown inFIGS. 4aand 4b, but rotated 180° around its center axis. However, the density of the inflow control element or ball30must have a density between that of oil and gas at in-situ conditions.

As for water, the gas fraction above which the valve1closes will be determined by the ratio between the diameter of the secondary outlet or pilot hole13and the diameter of the primary flow channel3at the vena contracta5′. The diameter ratio will be designed with respect to reservoir pressure and temperature, which affect the gas density. The pressure reversion principle discussed in relation toFIG. 6aand the re-opening mechanism inFIGS. 7cand 7d, orFIG. 8b, can also be used for gas.

After a typical petroleum well has been drilled and completed, and before production starts, the lower part of the well is normally filled with drilling fluid having a density being higher than the density of water. During an initial clean-up process, it is important that this drilling fluid can be produced out of the well without being blocked or restricted by valves1that close. One way of achieving this is shown inFIG. 10, where the barrier7of the valve1is provided with an additional inflow control element30′ arranged in a separate path32′ which resembles the path32discussed above.

In the embodiment shown inFIG. 10, the valve1is provided with the re-opening mechanism described in relation toFIGS. 7c-7g.

At a lower end portion, the separate path32′ is provided with an inlet11′ which hereinafter will be denoted drilling fluid inlet11′. The drilling fluid inlet11′ is in fluid communication with the chamber17(see for exampleFIG. 4a) forming part of the secondary flow channel9.

The additional inflow control element30′, here shown as a ball30′, has a density between that of drilling fluid and water, and is configured to move within the path32′ between a first position wherein the additional inflow control element30′ does not block the drilling fluid inlet11′, and a second position wherein the additional inflow control element30′ blocks the drilling fluid inlet11′.

As long as drilling fluid flows through the valve1, both balls30,30′ will reside at the top of their respective paths32,32′ since they have a density below that of drilling fluid. With the drilling fluid inlet11′ unblocked, the drilling fluid will flow into the said chamber17and consequently exert a high pressure on the first end portion22of the piston20, see for exampleFIG. 4a. Thus, the valve1will remain open.

When drilling fluid is subsequently displaced by oil, the additional inflow control element or ball30′ will descend and finally block the drilling fluid inlet11′. The inflow control element30for blocking inflow of water fraction above the predetermined level will remain at the secondary inlet11because of a slightly lower back-pressure within the cavity17. With both inlets11,11′ blocked, the pressure on the upstream or first end portion22of the piston20will drop and the valve1will close. Immediately thereafter, the valve1will re-open because of the automatic re-opening mechanism comprising the third inlet50.

When the drilling fluid has been drained out of the well, which normally will be for the rest of the life time of the well, ball30′ will remain at the bottom or second position within the path32′ and block the drilling fluid inlet11′, whereas ball30will move up and down within its path32and thereby close and open the valve1depending on the water fraction being produced through the valve1.

In the embodiments discussed above, the valve1comprises an annular piston20, wherein the first end portion or piston surface22fills substantially the cross-sectional area between the inner barrel P and the outer housing H. See for exampleFIG. 4d. An advantage of such an annular piston20is that the cross-sectional area of the piston surface22is maximized. However, an annular piston20may be subjected to friction forces due to its relatively large surface areas of the inner and outer perimeter surfaces, and also to leakage past the inner and outer perimeter. As an alternative to an annular piston20, one circular piston20′ or two or more circular pistons20′ may be arranged within the annular space between inner barrel P and the outer housing H. Said two or more circular pistons20′ may be interconnected. A valve provided with three circular pistons20′ are indicated in smaller scale inFIG. 4g. The purpose of such circular piston(s)20′ is the same as the annular piston20, i.e. to move axially in order to close the valve1when the content of undesired fluid in the flow upstream of the flow barrier7exceeds a predetermined level. Contrary to the annular piston20discussed above, such circular piston(s) will be without an inner perimeter surface. The circular pistons20′ indicated inFIG. 4gare equidistantly distributed and interconnected (indicated by dotted lines) within the annular space defined by the inner barrel P and the housing H, with a centre portion arranged at 0° (top portion in a position of use), at 120° and at 240°. A conceivable advantage of providing circular piston(s)20′ instead of an annular piston20shown inter alia inFIG. 4d, is that a circular piston by nature has only one outer perimeter and no inner perimeter and thereby a smaller surface area that may be subject to friction force. However, the applicant has calculated a ratio of pressure force to friction force for the two alternatives to determine which approach is more favorable. The calculations show that the ratio of pressure force to friction force is always twice as large for the annular valve as for the circular valve. This applies to all basepipe and housing dimensions. The applicant therefore prefers the annular piston20as disclosed herein.

It is possible to increase the total force towards the piston20if the piston is made up of multiple interconnected discs (not shown) stacked in the axial direction, where each disc has a low-pressure side and a high-pressure side. All low-pressure sides should in such a “stacked” embodiment be in mutual pressure communication, and all high-pressure sides should also be in mutual pressure communication. The total force acting on the piston will then be increased by a factor whose theoretical maximum equals the number of discs.

Turning now toFIGS. 11a-13concerning a system100comprising at least one valve1according to the present invention. The system100according to the invention provides additional features for controlling inflow of a fluid from the well W and into for example a production string PS.

InFIG. 11a, the system100further comprises an annular diverting device102. The diverting device will hereinafter also be denoted a cleanup module102. The diverting device or cleanup module is arranged upstream of a partly shown valve1in a portion of the production string PS as indicated, or in a portion of the barrel1. In the embodiment shown, the cleanup module102is arranged in a similar annulus as the valve1, such that the cleanup module102is arranged in series upstream of the valve1.

In the embodiment shown, the cleanup module102is provided with a lower leakage channel104and an upper leakage channel106a purpose of which will be discussed below.

FIG. 11bis an upstream view through M -M ofFIG. 11a, i.e. seen from right to left. The cleanup module102is provided with an upstream cleanup module barrier wall107provided with diverting device or cleanup module inflow control elements130,130′ arranged movable in paths132,132′, respectively, similar to the paths32,32′ for the inflow control elements30,30′ for the valve1discs cussed above. Hereinafter, the inflow control elements130,130′ will be denoted first inflow control element130and second inflow control element130′, respectively.

The first cleanup module inflow control element130is arranged in a first path132. In the position of use, a top end portion the first path132is provided with a first inlet111of a first channel112shown inFIG. 11c.

The second cleanup module inflow control element130′ is arranged in a second path132′. In the position of use, a bottom end portion the second path132′ is provided with a second inlet111′ of a second channel112′.

Both of the cleanup module inflow control elements130,130′ have a density between that of drilling fluid and that of water.

As shown inFIG. 11c, the first channel112extends straight through an upper portion of the cleanup module102, while the second channel112′ provides fluid communication between the second inlet111′ and an outlet135arranged in a wall portion of the barrel P or production string PS. Thus, the first channel112provides fluid communication from an upstream portion of the cleanup module102to an upstream or inlet portion I of the valve1(not shown inFIG. 11c), and the second channel112′ is configured to divert the fluid flow into the production string PS upstream of the valve1so is that the fluid flow bypasses the valve1.

When the fluid in the system is drilling fluid, both of the cleanup module inflow control elements130,130′ will be in the upper position of the paths132,132′, respectively. Thus, the first inlet111will be blocked while the second inlet111′ will be open. The drilling fluid will therefore flow through the second channel112′ only, i.e. into the production string PS and not to an inlet portion I of the subsequent valve1.

When the drilling fluid is eventually displaced by reservoir oil, the second cleanup module inflow control element or ball130′ will descend and finally block the second inlet111′ and thereby the second channel112′. However, the first cleanup module inflow control element or ball130will not fall down because leakage through the leakage channels104,106in the cleanup module102and the leakage channels52,54in the valve1, seeFIGS. 7cand 7d, will cause a back- or downstream pressure on the first ball130to be lower than the front or upstream pressure. This means that both the first channel112and the second channel112′, will be blocked, and there is only a small leakage rate through the leakage channels104,106and through the subsequent valve1. When the cleanup module102closes in this way and the total flow rate from the well W is kept constant by opening a topside or seabed choke more, a lower back-pressure is exerted on valves that may be located further upstream in the reservoir section, seeFIG. 1. This will in turn increase the pressure drawdown from the reservoir and thereby make the drilling fluid removal more efficient and complete.

When the cleanup process is eventually stopped, and the pressure is equalized across all valves1and cleanup modules102that may have been provided along a portion of the well W (for example the well W shown inFIG. 1), the first ball130will descend, uncover the first inlet111and thus open the first channel112, such that oil can subsequently be produced through the subsequent downstream valve1. The second channel112′ will remain blocked by second ball130′ for the rest of the lifetime of the producing well W.

Towards the end of the cleanup process discussed above, when all the drilling fluid has been removed from a reservoir section of a well W, all the valves1will eventually be closed. Such a situation might choke the well W too much and make it impossible to maintain a high and constant cleanup rate throughout the full duration of the cleanup process. In order to avoid that the last valves1(those located in a toe section of the well) close, an alternative design shown inFIG. 12can be used for the valves1in the toe section.FIG. 12is an alternative of the embodiment shown inFIG. 11b.

In the alternative design shown inFIG. 12, the cleanup module barrier107comprises an upper, first inlet111and a lower, second inlet111′ arranged in end portions of a path132for an inflow control element130.

The first inlet111is an inlet of a channel112extending in an axial direction through the cleanup module102. Thus, the first inlet111and corresponding channel112correspond to the first inlet111and the appurtenant channel112shown inFIG. 11c.

The second inlet111′ is an inlet of a second channel112′ that is configured to divert the fluid flow into the production string PS upstream of the valve1so that the fluid flow bypasses the subsequent valve1. Thus, the second inlet111′ corresponds to the second channel112′ shown inFIG. 11c.

When drilling fluid is displaced by oil, cleanup module inflow control element130′ will not fall down because it has lower back-pressure than front pressure as a result of leakage through channels104,106shown inFIG. 11a. Oil can therefore continue to flow through the second channel112′, i.e. directly into the production string PS.

Independent of the embodiment shown inFIG. 11bor the alternative embodiment shown inFIG. 12, the cleanup module102according to the invention is configured for diverting the fluid flow into the production string PS upstream of the barrel P and the valve1so that the fluid flow bypasses the valve1when fluid upstream of the cleanup module102is drilling fluid, and for allowing flow of fluid through the cleanup module102and to the inlet I of a subsequent valve1, or valves, when the cleanup module102is exposed to a fluid having a density being less than the density of the inflow control element.

When the cleanup process is finished and the flow from the well W is stopped, such that the pressure is equalized across the valve1, the second cleanup module inflow control element130′ shown inFIG. 11bor the inflow control element130shown in the alternative embodiment shown inFIG. 12, will descend and block the second inlet111′ and thus the second channel112′, and unblock the first inlet111and thus the channel112for subsequent oil flow through the subsequent valve1.

If it is desired to block or restrict both gas and water from an oil-producing well, a series of at least two differently configured valves1may be utilized. For example, the valve1shown inFIGS. 9aand 9bwhich is configured for closing the valve1when a content of gas upstream of the barrier7exceeds a predetermined level, may be arranged downstream of a valve1shown for example inFIGS. 4aand 4bor any of the other embodiments of the valve1configured for closing the valve1when a content of water upstream of the barrier7exceeds a predetermined level. In what follows the valve1shown inFIGS. 9aand 9bwill also be denoted “gas valve”1G, while the valve1shown for example inFIGS. 4aand 4bwill also be denoted “water valve”1W.

FIG. 13is an axial cross section of a principle arrangement of a system100comprising (from right to left) a cleanup module102, a water valve1W, a gas valve1G and an ICD module (ICD—Inflow Control Device) arranged downstream of the gas valve1G. The ICD is a commercially available product and is known to a person skilled in the art. The purpose of the ICD module is to create an extra pressure drop across the system100when fluid flows through the system100, in order to enforce a more uniform inflow profile from the reservoir, which in turn can contribute to delayed gas and/or water breakthrough and therefore a more favourable reservoir drainage of the reservoir F indicated inFIG. 1.

The ICD can either be a simple orifice with a small diameter, or it can consist of several parallel orifices with different sizes, where only one orifice is selected by configuring the ICD module manually prior to installation in the well W, or by using a downhole tool that can rotate the ICD module to the desired position from the inside after installation. The ICD module may also be provided with a permanent check valve (not shown) configured for preventing so-called reversed flow through the ICD module, gas valve1G and water valve1W.

However, a possibility for reversed fluid flow may be required during various well operations like scale squeeze and wellkill. Such a reversed fluid flow can be achieved by flowing fluid through the second channel112′ in the cleanup module102, wherein the second cleanup module inflow control element130′ will simply be pushed aside from the second inlet111′ when backflowing through channel112′.

In some wells, drilling fluid is displaced from the reservoir section prior to cleanup and before swell packers PA (seeFIG. 1) have expanded. A clean fluid, such as for example a base oil, is then pumped down the basepipe P (seeFIGS. 1 and 2) to TD (TD—Total Depth) and back up in the annular space between a lower completion CS and the sandface. The drilling fluid is then pushed up into the cased annulus. In order to ensure an efficient process whereby all the drilling fluid is displaced from the reservoir section, it is important to avoid backflow through the valves1as this will represent short-circuits for the flow. In order to avoid said backflow, temporary check valves can be installed in the cleanup module102of the system100, which prevent backflow and thereby force the flow all the way to TD before returning in the annulus. The check valve can be made temporary by using a material that dissolves after some time of oil production. Such a temporary check valve is known to a person skilled in the art.

The modular valve assembly shown inFIG. 13may also comprise a fail-safe mechanism, e.g. in the form of a sliding sleeve (not shown) arranged on an inner surface of the pipe P, wherein such a sliding sleeve is configured to be pulled open from the inside by a well tool (not shown). The failsafe mechanism may also be an integral part of the cleanup module102or a separate module placed upstream of the cleanup module102. An example of a suitable sliding sleeve is disclosed in Norwegian patent publication NO 334657.

Yet another use of the invention can be found for WAG injection wells (WAG—Water Alternating Gas). In order to obtain a more uniform outflux profile along the reservoir section when gas is injected, it is desirable for some WAG injection wells to restrict the outflow of gas more than the outflow of water. This can be achieved by the embodiment inFIG. 14awhich has similarities to the embodiment shown inFIG. 9a, but wherein the valve1is “mirrored” with respect to an imaginary vertical axis so that the inlet5of the valve1receives the “reversed” fluid flowing from the inside of the basepipe P, via the inlet35′ to the inlet I upstream of the inlet5.

The inflow control element30in the WAG application should have a density between that of water and gas at in-situ conditions. The leakage channel44should be have a diameter that provides the desired hydraulic resistance for gas.

The pressure reversion principle shown and discussed in relation toFIG. 6aand the re-opening mechanism shown and discussed in relation to inFIG. 7corFIG. 8bcan also be used for WAG wells.

From the disclosure herein, a person skilled in the art will appreciate that the valve1according to the present invention is an AICD (Autonomous Inflow Control Device) that operates independently of fluid viscosity, flow rate and Reynolds number, and that is also capable of reliably blocking or restricting the unwanted fluid for all flow rates once the volume fraction of the unwanted fluid exceeds a pre-defined limit. The valve1has very few movable parts and operates in response to phase split, i.e. volume fractions of desired and undesired fluids flowing through the valve1.

Embodiments of the valve1according to the invention provides reliable re-opening mechanisms.