Method to manipulate a well using an overbalanced pressure container

Abstract

A method to manipulate a well, comprising running an apparatus (60a) having a container (68a) with a volume of gas at a higher pressure than a surrounding portion of the well. The well is isolated, and a wireless control signal, such as an electromagnetic or acoustic signal, is sent to operate a valve assembly (62a) to selectively allow or resist fluid exit from a portion of the container (68a), via a port (61a). Some of the pressurised gas may itself be expelled in to the surrounding portion of the well, or it may be used to drive a fluid out of the container, such as an acid.

Claims

1. A method to deploy fluid in a well, comprising: (a) providing an apparatus comprising: a container having a volume of at least 1 litre (l) and at most 1600 l; a port to allow pressure and fluid communication between a portion of the container and a surrounding portion of the well; a mechanical valve assembly having a valve member adapted to move and one of to selectively allow and to selectively resist, directly or indirectly, fluid exit from at least a portion of the container, via the port; a control mechanism to control the mechanical valve assembly, comprising a communication device configured to receive a control signal for moving the valve member; (b) providing a fluid comprising a gas in at least a portion of the container, said portion having a volume of at least 1 l; (c) pressurising the gas to a pressure of at least 1000 psi and maintaining it at said pressure for at least one minute; (d) running the apparatus into the well, such that the apparatus is at least 100 m below the surface of the well; then, (e) isolating the port of apparatus from the surface of the well using at least one isolating component, the, or the uppermost, isolating component being at least 100 m from the surface well; (f) sending a control signal to the communication device at least in part by a wireless control signal transmitted in at least one of the following forms: electromagnetic (EM), acoustic, inductively coupled tubulars and coded pressure pulsing; then, (g) moving the valve member in response to said control signal to allow at least a portion of the fluid to be released from the container; and wherein (h) the container has a pressure of at least 100 psi more than a surrounding portion of the well immediately before the valve member is moved in response to the control signal and wherein the fluid is released from the container due to the pressure in the container being higher than the surrounding portion of the well immediately before the valve member is moved in response to the control signal.

2. A method as claimed in claim 1, wherein the fluid released displaces at least 1 l, optionally at least 5 l or at least 10 l of well fluid.

3. A method as claimed in claim 1, wherein step (b) is performed within 20 m of the surface of the well, and step (b) is performed before step (d) and so the apparatus is run into the well with the container having said fluid comprising a gas.

4. A method as claimed in claim 1, wherein the container has a floating piston, and on one side of the floating piston the gas is provided, and on an opposite side of the floating piston a liquid is provided, and the port is in communication with the side of the piston having the liquid.

5. A method as claimed in claim 1, wherein the apparatus is provided in the well below an annular sealing device, the annular sealing device engaging with an inner face of one of a casing and a wellbore in the well, and being at least 100 m below a surface of the well, and a connection means is provided connecting the apparatus to the annular sealing device, the connection means being above the apparatus and below the annular sealing device.

6. A method as claimed in claim 5, wherein the control signal is sent from above the annular sealing device.

7. A method as claimed in claim 5, wherein the port of the apparatus is provided above a second annular sealing device.

8. A method as claimed in claim 7, including conducting a short interval test and wherein the annular sealing device and second annular sealing device are less than 30 m apart, or less than 10 m apart, optionally less than 5 m apart, more optionally less than 2 m, or less than 1 m, or less than 0.5 m apart.

9. A method as claimed in claim 5, wherein the apparatus is deployed into the well in the same operation as deploying the annular sealing device into the well.

10. A method as claimed in claim 1, wherein in step (d) the apparatus is conveyed on one of tubing, drill pipe and casing/liner.

11. A method as claimed in claim 1, wherein a pressure sensor is provided in the well and is coupled to a wireless transmitter and pressure data is transmitted from the wireless transmitter.

12. A method as claimed in claim 1, wherein at least a section of the well containing the port of the apparatus is shut in, at one of surface and downhole, after the apparatus has been run and before the valve member moves in response to the control signal.

13. A method as claimed in claim 1, including using the apparatus to conduct at least one of an interval injectivity test, permeability test, pressure test, a connectivity test such as one of a pulse and interference test, hydraulic fracturing/minifrac procedure, image capture, chemical delivery, and well/reservoir treatment such as acid treatment.

14. A method as claimed in claim 13, wherein the apparatus delivers at least one of a breaker fluid, an acid and one of a chemical barrier and precursors to a chemical barrier, to the well.

15. A method as claimed in claim 1, further comprising conducting a procedure on the well, wherein the procedure includes at least one of image capture, a connectivity test such as one of a pulse and interference test, a build-up test, a drawdown test, a drill stem test (DST), an extended well test (EWT), one of hydraulic fracturing and minifrac procedure, a pressure test, a flow test, well/reservoir treatment such as an acid treatment, a permeability test, an injection procedure, gravel pack operation, perforation operation, string deployment, workover, suspension and abandonment.

16. A method as claimed in claim 1, wherein a pressure test is conducted on a barrier by the apparatus being provided below the barrier, the valve member being moved in response to the control signal causing the fluid to be released from the container to increase pressure below the barrier, and the pressure below the barrier is then monitored.

17. A method as claimed in claim 1, further comprising a charging means having a valve on the or another port, the method including exposing the gas to well pressure via said port to compress the gas, closing said port with said valve to resist fluid and pressure communication from the well into the container, using the compressed gas to facilitate said release of fluid from the container.

18. A method as claimed in claim 1, wherein the apparatus comprises a choke, optionally one of fixed and adjustable.

19. A method as claimed in claim 1, wherein the wireless control signal is transmitted as at least one of electromagnetic and acoustic control signals.

20. A method as claimed in claim 1, wherein the container comprises a propellant which is activated to create gas.

21. A method to deploy fluid in well, comprising: (a) providing an apparatus comprising: a container having a volume of at least 1 l and at most 1600 l; a port to allow pressure and fluid communication between a portion of the container and the surrounding portion of the well; a mechanical valve assembly having a valve member adapted to move and one of to selectively allow and to selectively resist fluid exit from at least a portion of the container via the port; a control mechanism to control the mechanical valve assembly, comprising a communication device configured to receive a control signal for moving the valve member; (b) providing a propellant in at least a portion of the container; (c) activating the propellant to produce a gas at a pressure of at least 1000 psi; (d) running the apparatus into the well, such that the apparatus is at least 100 m below the surface of the well; then, (e) sending a control signal to the communication device at least in part by a wireless signal transmitted in at least one of the following forms: electromagnetic (EM), acoustic, inductively coupled tubulars and coded pressure pulsing; then, (f) moving the valve member in response to said control signal to allow at least a portion of one of the gas and a liquid to be released from the container, wherein said portion of one of the gas and liquid is released from the container due to the pressure in the container being higher than the surrounding portion of the well immediately before the valve member is moved in response to the control signal to conduct at least one of an interval injectivity test, permeability test, pressure test, a connectivity test such as one of a pulse and interference test, chemical delivery, and well/reservoir treatment such as acid treatment; and wherein the container has pressure of at least 100 psi more than a surrounding portion of the well immediately before the valve member is moved in response to the control signal.

22. A method as claimed in claim 21, wherein the apparatus is provided in the well below an annular sealing device, the annular sealing device engaging with an inner face of one of a casing and a wellbore in the well, and being at least 100 m below a surface of the well, and a connection means is provided connecting the apparatus to the annular sealing device, the connection means being above the apparatus and below the annular sealing device.

23. A method as claimed in claim 21, wherein the apparatus is conveyed on one of tubing, drill pipe and casing/liner.

24. A method as claimed in claim 21, wherein the well is shut in, at one of surface and downhole, after the apparatus has been run and before the valve member moves in response to the control signal.

25. A method to deploy fluid in a well, comprising: providing an apparatus in the well, the apparatus comprising: a container having a volume of at least 10 l, and containing at least one of gas and liquefied gas at a pressure of at least 1000 psi; a port to allow pressure and fluid communication between a portion of the container and the surrounding portion of the well; a mechanical valve assembly having a valve member adapted to move, and one of to selectively allow and selectively resist, directly or indirectly, fluid exit from at least a portion of the container, via the port; a control mechanism to control the mechanical valve assembly, comprising a communication device configured to receive a control signal for moving the valve member; sending a control signal to the communication device at least in part by a wireless control signal in at least one of the following forms: electromagnetic (EM), acoustic, inductively coupled tubulars and coded pressure pulsing; moving the valve member in response to said control signal; allowing gas from said at least one of gas and liquefied gas in the container, to escape from the container to reduce the hydrostatic head in the well; and wherein the gas escapes from the container due to the pressure in the container being higher than the surrounding portion of the well immediately before the valve member is moved in response to the control signal.

Description

(1) FIG. 1 is a schematic view of a first apparatus which may be used in the method of the present invention;

(2) FIG. 2 is a schematic view of a second apparatus including a floating piston which may be used in the method of the present invention;

(3) FIG. 3 is a schematic view of a third apparatus including a drive chamber which may be used in the method of the present invention;

(4) FIG. 4 is a schematic view of a well with multiple zones, illustrating one aspect of the present invention;

(5) FIG. 5 is a schematic view of a further well illustrating further aspects of the present invention;

(6) FIG. 6 is a schematic view of a further well showing a further embodiment of the present invention where a portion of casing forms a container;

(7) FIG. 7 is an alternative apparatus having a charging means for use with embodiments of the present invention; and,

(8) FIG. 8 is a front view of an embodiment of a valve assembly for use with the various apparatus whilst conducting the method in accordance with the present invention.

(9) FIG. 1 shows apparatus 60a in accordance with the present invention in the form of a modified pipe, comprising a side opening 61a, a valve 62a, a control mechanism comprising a valve controller 66a and wireless transceiver (or receiver) 64a, a battery 63a and a container 68a. In use there is an overbalance of pressure between the container 68a and a surrounding portion of a well.

(10) The battery 63a serves to power the apparatus 60a after it has been run into the well.

(11) The valve 62a is configured to isolate the opening 61a to seal the container 68a from the surrounding portion of the well in a closed position and allow pressure and fluid communication between a portion of the container 68a and the surrounding portion of the well via the opening 61a in an open position.

(12) The components of the control mechanism (the transceiver 64a and the valve controller 66a which controls the valve 62a) are normally provided adjacent each other, or close together as shown; but may be spaced apart.

(13) In some embodiments, the container 68a is filled with a gas, such as nitrogen. In such embodiments, the gas is sealed in the container at the surface before being run into the well.

(14) In an alternative, the apparatus 60a may be used to reduce the hydrostatic head of a fluid column in a well, in order to assist in starting fluid flow from the well. The valve 62a is opened and the gas allowed to escape at an appropriate rate, which reduces the hydrostatic head. Such embodiments can obviate the requirement to run coiled tubing. For example, in certain circumstances such a method can help start a production well.

(15) FIG. 2 shows an embodiment of the apparatus 60b. FIG. 2 shows the apparatus 60b comprising an opening 61b, a choke 76b, a container 68b with a drive chamber section 70b; and a floating piston 74b which separates a main fluid-release section 67b of the container 68b from the drive chamber section 70b.

(16) The opening 61b branches into two different lines 61b′ & 61b″ controlled by valves 62b′ and 62b″ respectively. Each line 61b′ & 61b″ connects to a separate outlet tube 135, 136.

(17) Depending on the position of valve members (not shown) of the valves 62b′ & 62b″, pressure and fluid communication between a portion of the container 68b and a surrounding portion of a well is selectively allowed. The valves 62b′ & 62b″ are configured to isolate the lines 61b′ & 61b″ of the opening 61b to seal the container 68b from the surrounding portion of the well in a closed position, and allow pressure and fluid communication between a portion of the container 68b and the surrounding portion of the well via the opening 61b in an open position.

(18) The valves 62b′ & 62b″ are controlled by a valve controller 66b. The apparatus 60b also includes a communication device in the form of a transceiver 64b coupled to the valve controller 66b which is configured to receive a wireless control signal. In use, the valves 62b′ & 62b″ are moved from the closed position to the open position in response to the control signal.

(19) The apparatus 60b also comprises a battery 63b to power electronics such as the transceiver 164ba and valve controller 66b. Separate batteries may be provided for each powered component.

(20) The floating piston 74b comprises an annular seal 75b located around the floating piston 74b and in contact with an inner surface of the container 68b.

(21) The present embodiment is designed to expel the contents of the fluid-release section 67b of the container 68b into the well due to an overbalance of pressure in the container 68b; compared to the well. The drive chamber 70b comprises a gas (filled through a fill port, not shown), which is allowed to expand when pressure is dropped—caused by opening of the valves 62b′ and/or 62b″- and so drives the floating piston 74b towards the opening 61b to expel at least some of the contents of the fluid-release section 67b of the container 68b.

(22) A signal is sent to the valve controller 66b instructing the valves 62b′ and/or 62b″ to open. Once one or both of the valves 62b′ & 62b″ are open, the gas in the drive chamber 70b can expand. This expansion forces the floating piston 74b to move in an upwards direction, thus forcing the liquid in the fluid-release section 67b of the container 68b upwards towards the choke 76b. The liquid in the fluid-release section 67b is then forced out of the opening 61b at a rate controlled by the cross-sectional area of the choke 76b. For certain embodiments, the choke 76b and the valves 62b′ & 62b″ may be combined to create a variable choke. Also, the valves 62b′ & 62b″ may be opened and closed multiple times to release the contents over a period of time.

(23) The fluid-release section 67b of the container 68b is filled with a liquid, such as hydrochloric acid, so that an acid treatment, sometimes called an “acid wash” can be conducted to clean or treat the inner surface of the well. In some embodiments, the choke 76b may be integral with the valves 62b′ and/or 62b″.

(24) FIG. 3 shows a further embodiment of the apparatus 160. The apparatus 160 includes many common features of the earlier embodiments. But in contrast to the embodiments shown in FIGS. 1 and 2, FIG. 3 shows apparatus 160 wherein a control valve 162 is located in a central portion of the apparatus between a fluid-release section 167 and a drive chamber 170 both of the container 168. The present embodiment is designed to expel fluids from the fluid-release section 167 into a well via a mechanical control valve 162 which indirectly allows or resists fluid exit from the port 161 due to an overbalance of pressure in the drive chamber 170.

(25) The floating piston 174 is located in the fluid-release section 167 of the container 168 above the control valve 162. The drive chamber 170 is pressurised so that its pressure is higher than the surrounding portion of the well.

(26) A further check valve (not shown) may be provided close to the choke 176 to prevent fluids from mixing with well fluids. However even without such a check valve, the piston doesn't move with the control valve 162 closed and so little mixing occurs.

(27) In use, the sequence begins with the control valve 162 in the closed position and the floating piston 174 located towards the bottom (as illustrated) of the container 168. A signal is then sent to the valve controller 166 instructing the control valve 162 to open. Once the control valve 162 opens, the overbalance of pressure in the drive chamber 170, drives the piston 174 upwards and expels fluid in the fluid-release section 167 of the container to the surrounding portion of the well. The rate at which the fluid in the fluid-release section 167 is expelled into the well is controlled by the choke 176.

(28) FIG. 4 shows a multi-zone well 114 comprising a liner hanger 129 and a liner 112 and two sets of apparatus labelled 60a′ and 60a″ in separate sections. These can be the apparatus 60a described above or indeed the other embodiments 60b or 160 also described above.

(29) Instrument carriers 140, 141 and 146 are provided in each section and also above an annular sealing device in the form of a packer element 122a. Each instrument carrier comprises a pressure sensor 142, 143, and 148 respectively, and a wireless relay 144, 145, and 149 respectively. Data from the pressure sensor(s) can be wirelessly transmitted to the surface, for example by acoustic or electromagnetic signals, for monitoring purposes.

(30) Pressure gauges can monitor the pressure within the containers. Moreover, the gauges or other devices can be powered by batteries.

(31) The apparatus 60a′ also includes an outlet tube 135, which has multiple openings or outlets 137 through which fluid can be released onto an adjacent upper slotted liner 154a.

(32) The outlet tube 135 and openings 137 can direct fluid from the container at multiple points, and controlled by the valve 62a as shown. A number of other options are available—this tube can be used in the lower section instead of, or in addition to, its illustrated position, and separate valves may be used to control fluid through the openings 137.

(33) The well 114 has its own well apparatus 110 which comprises two annular sealing devices in the form of two packer elements 122a & 122b which splits the well into a plurality of sections. A first, upper, section comprises the upper packer element 122a, a wirelessly controlled upper sleeve valve 134a, the upper apparatus 60a′ and the upper slotted liner 154a. The sleeve valve 134a, together with the packer 122a are the isolating components which isolate the port of the apparatus 60a′ from the surface of the well.

(34) A second, lower, section comprises the lower packer element 122b, a wirelessly controlled lower sleeve valve 134b, the lower apparatus 60a″ and a lower slotted liner 154b. For this second section, the sleeve valve 134b, together with the packer 122b are the isolating components which isolate the port of the apparatus 60a″ from the surface of the well. Moreover, they also function as lower isolating components for the first upper section.

(35) The slotted liners 154a, 154b create communication paths between the inside of the liner 112 and the adjacent formation.

(36) Isolating the sections from each other provides useful functionality for manipulating each adjacent zone individually though this is not an essential feature of the invention. For example, the valve 134a in the upper section can be closed to isolate the upper apparatus 60a′ from surface of the well, whilst flow continues from the zone adjacent the second lower section.

(37) The well 114 further comprises a packer such as a swell packer 128 between an outer surface of the liner 112 and a surrounding portion of the formation. An upper tubular 118 and lower tubular 116 are continuous and connected to the liner 112 via the upper packer element 122a and the lower packer element 122b. Portions of the upper tubular 118 and lower tubular 116 thus serve as connectors to connect the upper apparatus 60a′ and lower apparatus 60a″ to the packer elements 122a, 122b respectively.

(38) In use, the well 114 flows through the lower slotted liner 154b and into the lower tubular 116 via the lower sleeve valve 134b. The flow continues through the lower tubular 116 past the lower packer element 122b, the upper apparatus 60a′ and instrument carrier 146 before continuing through the upper tubular 118 towards the surface. The upper apparatus 60a′ (in contrast to the lower apparatus 60a″) does not take up the full bore of the upper tubular 118 and so fluid can flow therepast from below without being diverted outside of the upper tubular 118.

(39) From an upper zone, the well flows through the slotted liner 154a and into the upper tubular 118 via the sleeve valve 134a. The flow continues through the upper tubular 118, past the upper packer element 122a towards the surface.

(40) In use, the flow may be from the upper zone adjacent the well 114 only, the lower zone adjacent the well 114 only, or may be co-mingled, that is produced from the two zones simultaneously. For example, fluids from the slotted liner 154b combine with further fluids entering the well 114 via the upper slotted liner 154a to form a co-mingled flow.

(41) The apparatus 60a′/60a″ is activated when the port of the respective apparatus is isolated from the surface by the respective sleeve valves 134a/134b, which may be prior to flowing the well or after flowing the well. A wireless signal is sent from a controller (not shown) to the valve controller via the transceiver and the valve member opens to allow pressure and fluid communication with the surrounding portion of the well. The overbalance of pressure in the container 168a causes the fluid to be released.

(42) The apparatus 60a′ is particularly suited to deploying acid for an acid treatment, as it can distribute the fluid over the slotted liner 154a via the tube 135. The acid can be deployed from the apparatus 60a′ to function as an acid wash and then optionally pressure in the well can be increased by conventional means to “inject” the acid into the formation.

(43) The apparatus 60a″ can also be used for chemical discharge for example.

(44) FIG. 5 illustrates another method of the present invention used during a drill stem testing (DST) operation. Where the features are the same as the FIG. 4 embodiment they have been labelled with the same number except preceded by a “2”. These features will not be described in detail again here. Apparatus 60a is located above the packer 222 and includes some propellant (not shown), and apparatus 60b is located below the packer 222. Apparatuses 60a and 60b were previously described in FIG. 1 and FIG. 2. Alternatively the apparatus 160 can be used in place of the apparatus 60a and/or 60b.

(45) In use, the annulus 214 between the tubing 218 and the casing 212 above the packer 222 includes well fluids which may be relatively dense fluid or mud especially for high pressure wells. The present inventors have noted that under certain circumstances, the mud may become particularly dense and indeed partially solidify, close to the packer 222, for example as the heavier components settle due to gravity or other forces. The transmission of pressure signals close to or through this substance is more difficult—signals may only be received intermittently or not at all. For example, transmission of signals to a tester 230 or circulation 231 valve can be inhibited.

(46) The apparatus 60a therefore functions to cause a dynamic overbalance to disrupt, inhibit and/or reverse the settling out and partial solidification of well fluids in the annulus. Signals to the tester valve 230 or circulation valve 231 above the apparatus 60a are thereafter more reliable.

(47) A variety of alternatives can be provided. The valve may be cycled so that the overbalanced chamber creates a number of dynamic overbalances spaced apart in time. Further containers or indeed apparatus may also be used for the same purpose.

(48) The apparatus 60b is provided below a perforating gun 250. Two outlet tubes 135, 136 extend from opening 61b of the apparatus 60b over the perforating gun 250. The tubes 135, 136 can have multiple outlets 137 as shown, or alternatively a single outlet, for example to deploy a deploying fluid. The tubing 218 and perforating gun 250 serve as a connector to connect the apparatus 60b to the annular sealing device 222.

(49) A discrete temperature array 253 is provided adjacent to the perforations 252 and connected to a controller 255. In this embodiment the discrete temperature array has multiple discrete temperature sensors along the length of a small diameter tube.

(50) After being isolated from the surface of the well by the tester valve 230, the apparatus 60b is activated wirelessly by the valves 62b′ and/or 62b″ opening, creating a dynamic overbalance, which can direct fluid, such as acid, onto the perforations. Providing two outlets and respective tubes 135, 136 allows fluids to be directed onto the area of the perforations which is assessed as requiring treatment.

(51) The apparatus 60a′, 60a″, 60a, 60b illustrated in FIGS. 4 and 5 can be used independent of each other in single or multiple zone wells.

(52) Various embodiments of the apparatus are interchangeable. For example the apparatus 60a can be used in place of the apparatus 60b to deploy chemicals.

(53) In FIG. 6, an alternative embodiment of an apparatus 260 with a container 268 is illustrated. Common features, for example a valve (labelled 265 in FIG. 6), with earlier embodiments are not described again in detail for brevity. In contrast to earlier figures the container 268 is in part defined by the surrounding casing 212a and outlet tube 235 with openings 237 is secured to a portion of the casing 212b above the container 268 by clamps 296. Such an apparatus 260 is normally run on the casing, slotted liner or screens 212a/212b when completing the well. An advantage of such an embodiment is that the container can have larger volumes without running further tubing into the well. The apparatus 260 may have flow bypass 297 for cementing during completion or for circulating during deployment. Whilst applicable more generally, such embodiments are useful for deploying treatments or artificial gas lift in accordance with the third aspect of the present invention to a toe of a deviated well.

(54) Moreover, embodiments can be used to clear water from a gas well. In such embodiments, the outlet tube 235 would not be required and the gas is ported to the casing above the container (rather than the annulus between the casing and the well). In certain situations, a gas well produces from an upper zone or section of a zone and a water column resists gas production from a lower zone which has insufficient pressure to overcome the combined hydrostatic head of the water column and upper zone. The water column is thus ‘trapped’ in the well and prevents production from a lower zone. Certain embodiments of the present invention, such as the FIG. 6 embodiment, can be used to remove a portion of the water column to allow the lower zone to produce.

(55) More generally, embodiments of the present invention in accordance with the third aspect of the invention can function in a gas lift application, for example to assist in commencing flow from the lower end of a highly permeable well.

(56) An alternative apparatus providing a similar charging option is an apparatus 460 shown in FIG. 7. Like parts with earlier embodiments are not described in detail but are prefixed with a ‘4’.

(57) The apparatus 460 comprises a container 468, a first valve 462 in a first port 461, and a second valve 477 in a second port 473 at an opposite end to the first port 461. The container 468 has a first floating piston 474 separating a first liquid containing section 491 from a second gas containing section 492. A second floating piston 482 is provided in the container 468 between the second port 473 and the first floating piston 474, to define a third ‘charging’ section 493.

(58) In use, the apparatus 460 may be launched with the floating piston 474 positioned such that around three quarters of the container 468 is the gas containing section 492 and around one quarter is the liquid containing section. As the apparatus is moved deeper into the well, the increased well pressure will cause movement of the floating piston 474 and compress the gas.

(59) The apparatus is positioned below the barrier to be tested, with the valve 477 open and well fluids are received into the charging section 493 of the container 468 compressing or ‘charging’ the gas in the second section 492 to the surrounding well pressure. The valve 477 is then closed.

(60) When the barrier (not shown) is in place, and the pressure surrounding the apparatus reduced (for example less pressure from surface) the valve 462 is opened to allow the fluid from the first section 491 of the container 468 into the surrounding portion of the well driven by the compressed gas in the second section 492 of the apparatus 460. Thus using the FIG. 7 apparatus the charging functionality is provided and also the fluid being expelled can be chosen for its intended use, such as an acid treatment.

(61) The embodiments as described may make use of any additional pressure in the well in order to charge the gas further. For example if a certain operation was occurring in the well resulting in a higher surrounding well pressure, the valve may be opened to allow the well pressure (when higher) to act on the floating piston and compress the gas in the section before closing the valve. At a later time when the surrounding pressure is less (which may be a consequence of temperature changes), this compressed gas can be used to expel the fluid from the container. This may be useful for pressure testing a barrier which is formed after the apparatus is charged from below since the nature of fluids expelled is not important.

(62) A variety of valves may be used with the apparatus described herein. FIG. 8 shows one example of a valve assembly 500 in a closed position A and in an open position B. The valve assembly 500 comprises a housing 583, a first inlet port 581, a second outlet port 582 and a valve member in the form of a piston 584. The valve assembly further comprises an actuator mechanism which comprises a lead screw 586 and a motor 587.

(63) The first port 581 is on a first side of the housing 583 and the second port 582 is on a second side of the housing 583, such that the first port 581 is at 90 degrees to the second port 582.

(64) The piston 584 is contained within the housing 583. Seals 585 are provided between the piston 584 and an inner wall of the housing 583 to isolate the first port 581 from the second port 582 when the valve assembly 500 is in the closed position A; and also to isolate the ports 581, 582 from the actuator mechanism 586, 587 when the valve assembly is in the closed A and/or open B position.

(65) The piston 584 has a threaded bore on the side nearest the motor 587 which extends substantially into the piston 584, but does not extend all the way through the piston 584. The lead screw 586 is inserted into the threaded bore in the piston 584. The lead screw 586 extends partially into the piston 584 when the valve assembly 500 is in the closed position A. The lead screw 586 extends substantially into the piston 584 when the valve assembly is in the open position B.

(66) In use, the valve assembly is initially in the closed position A. A side of the piston 584 is adjacent to the first port 581 and a top side of the piston 584 is adjacent to the second port 582 so that the first port 581 is isolated from the second port 582. This prevents fluid flow between the first port 581 and the second port 582. Once the actuator mechanism receives a signal instructing it to open the valve, the motor begins to turn the lead screw 586 which in turn moves the piston 584 towards the motor 587. As the piston 584 moves, the lead screw 586 is inserted further into the piston 584 until one side of the piston 584 is adjacent to the motor 587. In this position, the first port 581 and the second port 582 are open and fluid can flow in through the first port 581 and out through the second port 582.

(67) Modifications and improvements can be incorporated herein without departing from the scope of the invention. For example various arrangements of the container and electronics may be used, such as electronics provided in the apparatus below the container.

(68) Moreover, whilst the chokes illustrated here are purely reduced diameter chokes, other forms of chokes can be utilised, for example an extended section with a restricted diameter.