Method and apparatus

Abstract

In an aspect of the invention there is provided a method comprising: pumping fluid from a first source of fluid into a first, motive, fluid store by means of a mechanical pump and storing the fluid under pressure in the first fluid store; releasing fluid under pressure from the first fluid store and supplying the fluid to a motive fluid inlet of a first ejector; drawing further fluid from the first or a further fluid source into the pumping inlet of the first ejector by means of the fluid supplied to the motive fluid inlet; storing fluid output from an outlet of the first ejector in a second fluid store.

Description

[0001] METHOD AND APPARATUS

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to the storage of compressible fluid in a fluid store by means of an ejector pump. In particular but not exclusively the invention relates to the storage of fluid in a fluid store whereby the fluid store comprises a geological store such as a well, an aquifer such as a saline aquifer, a mine or a cavern.

[0004] BACKGROUND

[0005] Carbon capture, usage, and storage (CCUS) is being employed to reduce global emissions of carbon dioxide to the atmosphere. Spent gas wells and spent oil wells, as well as disused coal mines, salt mines and other geological structures are being considered as potential long term stores for greenhouse gases such as carbon dioxide (CO2).

[0006] The present applicant has recognised that ejectors may be used to compress gas to be stored in a gas store suitable for long term gas storage.

[0007] It is known to provide an ejector pump for pumping fluid in the form of a liquid or gas. A supply of motive fluid is provided to a motive fluid inlet of the ejector, whilst a source of fluid to be pumped is supplied to a fluid inlet. Motive fluid entering the ejector causes a drop in pressure at the fluid inlet, drawing fluid to be pumped into the ejector. Fluid to be pumped becomes entrained in motive fluid passing from the motive fluid inlet to a fluid outlet of the ejector. The entrained fluid is thereby compressed and exits the ejector at a higher pressure.

[0008] STATEMENT OF THE INVENTION

[0009] Embodiments of the invention may be understood with reference to the appended claims.

[0010] Aspects of the present invention provide a method and an apparatus.

[0011] In one aspect of the invention for which protection is sought there is provided a method comprising: pumping fluid from a first source of fluid into a first, motive, fluid store by means of a mechanical pump and storing the fluid under pressure in the first fluid store; releasing fluid under pressure from the first fluid store and supplying the fluid to a motive fluid inlet of a first ejector; drawing further fluid from the first or a further fluid source into the pumping inlet of the first ejector by means of the fluid supplied to the motive fluid inlet; storing fluid output from an outlet of the first ejector in a second fluid store.

[0012] Embodiments of the invention have the advantage that the mechanical pump used to pump fluid from the first source into the first store is not required to pump further fluid from the first or further source into the second store. Rather, a pressure of fluid stored in the first store may be used to pump further fluid from the first or further source into the second store by means of the ejector. During the period in which the pressure of fluid stored in the first store is being so used, the mechanical pump may be used to pump further fluid from the first or further source. Thus, the rate at which fluid is drawn from the first or further source may be increased. This feature allows more rapid storage of fluid from the first or further source in a store and may be useful at times when demand for storage of fluid is at a peak, for example when a rate of supply of fluid increases or a new source of fluid becomes available such as a fresh delivery of fluid to be stored, such as a ship having fluid in a fluid store that is required to be transferred to the first fluid store, second fluid store, or a further fluid store.

[0013] It is to be understood that the first fluid store may be considered to be an energy store or “battery” since the fluid stored therein under pressure may be employed to drive the ejector to pump fluid from the first or a further fluid source to the second fluid store where it may be stored under pressure.

[0014] Furthermore, in some arrangements, a distance between the mechanical pump and second fluid store may be too long to allow an adequate pumping speed of fluid from the first or further source to the second fluid store to be achieved. By positioning the ejector pump in a fluid line connecting the first and second fluid stores, the ejector may be used to pump fluid from the first or further sources to the second fluid store using the pressure of fluid in the first fluid store developed by the mechanical pump.

[0015] Some embodiments of the invention may reduce overall energy consumption. In some embodiments, a fresh or part used natural gas well may be employed to provide the motive fluid to power an ejector for pumping fluid to a fluid store such as a disused natural gas well, for example for pumping fluid such as carbon dioxide into the disused natural gas well. By disused is meant that the pressure of natural gas in a well has fallen to a relatively low level, for example following extraction, permitting carbon dioxide to be stored therein.

[0016] The method may comprise pumping fluid from the first source or further source of fluid into a further, motive, fluid store by means of the mechanical pump whilst fluid from the first fluid store is supplied to the motive fluid inlet of the first ejector.

[0017] Optionally, the first fluid store is one selected from amongst a well, a mine and a cavern. Optionally, the first fluid store may be an aquifer.

[0018] This feature has the advantage that relatively large amounts of fluid requiring long term storage may be stored in existing storage volumes. The requirement to fabricate suitable storage volumes such as metal or concrete storage tanks is therefore obviated.

[0019] Optionally, the second fluid store is one selected from amongst a well, a mine and a cavern. Optionally, the second fluid store may be an aquifer.

[0020] The well may be an oil well, a gas well, aquifer such as saline aquifer or any other suitable geological feature in which a fluid may be stored under pressure.

[0021] In some arrangements, a mine may be employed such as a disused coal mine, a mineral mine or any other suitable form of mine in which a fluid may be stored under pressure.

[0022] A cavern may be employed such as a salt cavern or any other suitable form of cavern in which a fluid may be stored under pressure.

[0023] Optionally, the fluid drawn from the first or further fluid sources comprises carbon dioxide, optionally whereby the first and second fluid is at least 50% carbon dioxide, further optionally whereby the first and second fluid is at least 75% carbon dioxide, further optionally whereby the first and second fluid consists substantially of carbon dioxide. Optionally, the fluid drawn from the first or further fluid sources comprises methane, optionally whereby the first and second fluid is at least 50% methane, further optionally whereby the first and second fluid is at least 75% methane, further optionally whereby the first and second fluid consists substantially of methane.

[0024] Disused wells and aquifers are known to provide suitable long-term storage opportunities for waste carbon dioxide produced by industrial processes such as combustion processes.

[0025] The method may comprise releasing fluid stored in the second fluid store and supplying the fluid to a motive fluid inlet of a second ejector.

[0026] The method may comprise: drawing second fluid from a fluid source into the pumping inlet of the second ejector by means of the fluid supplied to the motive fluid inlet; storing fluid output from an outlet of the second ejector in a third fluid store.

[0027] Optionally, the fluid source from which second fluid is drawn is the first or a further fluid source.

[0028] It is to be understood that one or more mechanical pumps or compressors may be used to pump fluid from the first or a further fluid source to the first, second or a further fluid store.

[0029] In a further aspect of the invention there is provided apparatus comprising: a mechanical pump; and a first ejector, wherein an inlet of the mechanical pump is arranged to be coupled to a first source of fluid and an outlet of the mechanical pump is arranged to be coupled to a first fluid store, the apparatus being configured to pump fluid from the first source to the first fluid store by means of the mechanical pump; and wherein a motive inlet of the first ejector is arranged to be coupled to the first fluid store, a pumping inlet of the first ejector is arranged to be coupled to the first or further fluid source, and the outlet of the first ejector is arranged to be coupled to a second fluid store, the apparatus being configured to supply fluid under pressure from the first fluid store to the motive inlet of the first ejector and to pump fluid from the first or further fluid source to the second fluid store by means of the first ejector. The apparatus may be configured to: pump fluid from the first source or further source of fluid into a further, motive, fluid store by means of the mechanical pump whilst fluid from the first fluid store is supplied to the motive fluid inlet of the first ejector.

[0030] Optionally, the first fluid store is one selected from amongst a well, a mine and a cavern.

[0031] This feature has the advantage that relatively large amounts of fluid requiring long term storage may be stored in existing storage volumes. The requirement to fabricate suitable storage volumes such as metal or concrete storage tanks is therefore obviated.

[0032] Optionally, the second fluid store is one selected from amongst a well, a mine, an aquifer and a cavern.

[0033] The well may be an oil well, a gas well, aquifer such as saline aquifer or any other suitable geological feature in which a fluid may be stored under pressure.

[0034] In some arrangements, a mine may be employed such as a disused coal mine, a mineral mine or any other suitable form of mine in which a fluid may be stored under pressure.

[0035] A cavern may be employed such as a salt cavern or any other suitable form of cavern in which a fluid may be stored under pressure.

[0036] Optionally, the fluid drawn from the first or further fluid sources comprises carbon dioxide, optionally whereby the first and second fluid is at least 50% carbon dioxide, further optionally whereby the first and second fluid is at least 75% carbon dioxide, further optionally whereby the first and second fluid consists substantially of carbon dioxide.

[0037] Disused wells and aquifiers are known to provide suitable long-term storage opportunities for waste carbon dioxide produced by industrial processes such as combustion processes.

[0038] The apparatus may be configured to release fluid stored in the second fluid store and supply the fluid to a motive fluid inlet of a second ejector. The apparatus may be configured to: draw second fluid from a fluid source into the pumping inlet of the second ejector by means of the fluid supplied to the motive fluid inlet; and store fluid output from an outlet of the second ejector in a third fluid store.

[0039] Optionally, the fluid source from which second fluid is drawn is the first or a further fluid source.

[0040] In an aspect of the invention there is provided a method comprising: releasing a first fluid under pressure from a first fluid store and supplying the fluid to a motive fluid inlet of an ejector; drawing a second fluid into the pumping inlet of the ejector from a second fluid source by means of the fluid supplied to the motive fluid inlet; storing fluid output from an outlet of the ejector in a second fluid store.

[0041] In an aspect of the invention there is provided a method comprising: storing a first, motive, fluid in a first, motive, fluid store; releasing the first fluid from the first fluid store and supplying the fluid to a motive fluid inlet of an ejector; drawing a second fluid into the pumping inlet of the ejector from a second fluid source by means of the fluid supplied to the motive fluid inlet; storing fluid output from an outlet of the ejector in a second fluid store.

[0042] This feature has the advantage that the pressurised fluid in the first motive fluid store may be used to pump fluid from a second fluid source. The first, motive, fluid in the first, motive, fluid store, may be an oil well comprising oil under pressure and optionally gas under pressure, or a gas well comprising gas under pressure. Accordingly, in some embodiments, naturally present pressurised fluid in a first fluid store such as oil in an oil well or gas in a gas well may be used to pump fluid from a second fluid source to a second fluid store. The pressurised fluid may be subject to a phase separation process prior to a portion of the separated fluid being supplied to the motive fluid inlet of the ejector.

[0043] Optionally, the first fluid store is one selected from amongst a well, a mine and a cavern.

[0044] Optionally, the second fluid store is one selected from amongst a well, a mine and a cavern. The well may be an oil well, a gas well or any other suitable well in which a fluid may be stored under pressure.

[0045] The mine may be a coal mine, a mineral mine or any other suitable form of mine in which a fluid may be stored under pressure.

[0046] The cavern may be a salt cavern or any other suitable form of cavern in which a fluid may be stored under pressure.

[0047] Optionally, the first and second fluid is carbon dioxide.

[0048] The method may comprise, prior to releasing the first fluid from the first fluid store, pumping the first fluid into the first fluid store by means of a mechanical compressor.

[0049] The method may comprise releasing fluid stored in the second fluid store and supplying the fluid to a motive fluid inlet of a second ejector.

[0050] The method may comprise drawing second fluid from a fluid source into the pumping inlet of the second ejector by means of the fluid supplied to the motive fluid inlet; storing fluid output from an outlet of the second ejector in a third fluid store.

[0051] The fluid source from which second fluid is drawn may be the second fluid source.

[0052] Within the scope of this application it is envisaged that the various aspects, embodiments, examples, features and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings may be taken independently or in any combination. Features described with reference to one embodiment are applicable to all embodiments, unless there is incompatibility of features.

[0053] For the avoidance of doubt, it is to be understood that features described with respect to one aspect of the invention may be included within any other aspect of the invention, alone or in appropriate combination with one or more other features.

[0054] BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described with reference to the accompanying figures in which:

[0055] FIGURE 1 is a schematic illustration of a known design of a system for sequestering carbon dioxide in a subsea natural gas and / or oil well;

[0056] FIGURE 2 is a schematic illustration of an arrangement according to an embodiment of the present invention for sequestering carbon dioxide in two natural gas or oil wells;

[0057] FIGURE 3 is a schematic illustration of an arrangement according to an embodiment of the present invention for sequestering carbon dioxide in two natural gas or oil wells, corresponding to the arrangement of FIG. 2 with the storage vessel for storing gas to be sequestered removed;

[0058] FIGURE 4 is a schematic illustration of a further arrangement according to an embodiment of the present invention for sequestering carbon dioxide in three expired gas or oil wells;

[0059] FIGURE 5 is an enlarged view of a portion of FIG. 3 showing the ejector device; and

[0060] FIGURE 6 is a schematic illustration of an arrangement according to an embodiment of the present invention for sequestering carbon dioxide in a natural gas or oil well, using the pressure of natural gas or oil in an oil well.

[0061] DETAILED DESCRIPTION

[0062] Embodiments of the present invention are directed to providing apparatus for sequestering carbon dioxide or other gas to be sequestered. FIG. 1 shows a known apparatus 100 in which a mechanical pump 110 draws gas such as waste gas (in the example shown, waste carbon dioxide) from one or more sources that may include rail 102a, road 102b, pipeline 102c or ship 102d. The pump 110 pumps the gas along a pipeline 120 along a seabed 105b to a selected one (or more) of several stores in the form of disused natural gas wells 150a, 150b, 150c. In some known arrangements the wells may be disused oil wells, or disused wells of oil and gas. The wells may be onshore or offshore. It is to be understood that the pressure at which a given geological well closes and is no longer drawn from may differ from well to well. A well may close at a pressure in the range 5-10 bar in some examples.

[0063] In the example shown, the wells 150a-c are accessed via a respective rig 155a, 155b, 155c. Thus the gas to be stored is pumped via subsea pipeline 120 to a selected rig 155a-c, which in turn feeds the gas to a respective well 150a-c. In the configuration shown, carbon dioxide gas under pressure is being supplied to first well 150a, such that a pressure of carbon dioxide in the well 150a is rising. The well is thus shown as a “HP” or “high pressure” well 150a.

[0064] Once the pressure of carbon dioxide in the first well 150a reaches a required value, such as a pressure in the range 40-50 bar in some examples, the carbon dioxide gas is directed to the second rig 155b, which in turn directs the gas into the second well 150b. Once the second well reaches the desired pressure, such as a pressure in the range 40- 50 bar, further carbon dioxide may be directed to the third well 150c via third rig 155c in a corresponding manner.

[0065] FIG. 2 shows an apparatus 200 according to an embodiment of the present invention for sequestering gas. The embodiment of FIG. 2 will be described with respect to the storage of carbon dioxide but it is to be understood that any suitable compressible fluid such as a gas may be sequestered using the apparatus 200. Like features of the apparatus 200 to that of known apparatus 100 are shown with like reference numerals incremented by 100. The gas to be sequestered, in this example carbon dioxide, may also be described as a “primary” fluid since the primary purpose of the apparatus is to sequester the primary fluid.

[0066] The apparatus 200 has a mechanical pump 210 that may be similar to or substantially the same as the mechanical pump 110 used in the known apparatus of FIG. 1. The mechanical pump 210 is configured to supply carbon dioxide from a source 202 of carbon dioxide to a first subsea storage volume or store 250a in the form of a disused gas well via a subsea pipeline 220. The gas well may have a residual pressure of around 5-10 bar of natural gas (typically primarily methane) therein prior to injection of carbon dioxide. Other residual pressures may be found to be present in some examples. A valve 220a allows the mechanical pump 210 to be isolated from the first store 250a when required, for example when the mechanical pump 210 is not required to pump gas into the first store 250a.

[0067] In the arrangement shown in FIG. 2 the source of carbon dioxide is a storage vessel 202 that receives carbon dioxide via pressure vessels carried by rail 202a, pressure vessels carried by road 202b, and carbon dioxide supplied via a pipeline 202c. Pressure vessels carried by sea 202d or one or more other sources may supply carbon dioxide to the storage vessel 202 in addition or instead. In some arrangements, one of more of the sources may be connected to the mechanical pump 210 substantially directly without being supplied to the storage vessel 202. The storage vessel 202 acts as a ballast tank to receive and temporarily hold carbon dioxide for sequestration in subsea storage volumes as described herein.

[0068] In some alternative embodiments, the storage vessel 202 may be omitted and gas fed to the pump 210 directly from a source such as one or more of sources 202a, 202b, 202c, 202d. FIG. 3 is a schematic illustration of the apparatus 200 of FIG. 2 with the storage vessel 202 removed.

[0069] The first subsea storage volume or store 250a is connected by means of a pipeline 223 to a motive inlet 260m of an ejector 260. A valve 223a is provided to isolate the first store 250a from the motive inlet 260m when desirable, for example when valve 220a is open and the mechanical pump 210 is charging (i.e. filling or loading) the first store 250a with carbon dioxide via pipeline 220. However in some operational situations valve 223a may remain open such that mechanical pump 210 continues to charge the first store 250a whilst the first store 250a is used to drive the ejector 260.

[0070] A pumping inlet 260in of the ejector 260 is connected via pipeline 222 to the storage vessel 202. A valve 222A is provided to isolate the storage vessel 202 from the pumping inlet 260in when required, for example when valve 223a is closed.

[0071] A pumping outlet 260out of the ejector 260 is connected via pipeline 224 to second store 250b. A valve 224a is provided to isolate the pumping outlet 260out of the ejector 260 from the second store 250b, for example when valves 223a and 222a are closed. It is to be understood that pipeline 222 supplying the ejector 260 with gas to be stored may have a diameter of around 28 inches (around 71cm) in some embodiments. Other diameters may be useful in some embodiments.

[0072] In use, the apparatus 200 may be configured such that valves 222a, 223a, 224a are closed. The mechanical pump is then activated and valve 220a opened in order to store carbon dioxide from one or more sources 202a-d via vessel 202 under pressure in the first store 250a.

[0073] Carbon dioxide may be pumped into the first store 250a until the pressure of gas stored in the first store 250a reaches a required value, such as a value in the range 40-50 bar. In some examples, carbon dioxide may be pumped into the first store 250a until the pressure of gas therein is at a higher value, for example a value in the range 100-150bar or more.

[0074] Once the desired pressure is reached, valve 220a may be closed. The mechanical pump 210 may then be coupled to another store 250 and used to pump carbon dioxide from the source 202a-d into the other store 250. Meanwhile, the pressure of gas stored in the first store 250a may be used to drive the ejector 260 to draw fluid from the source 202a-d and store the fluid in the second store 250b. The first store 250a may thus be considered to be an energy store or “battery” from which energy may be drawn to pump further gas from the source 202a-d to a store 250b.

[0075] Accordingly, valves 223a and 224a may be opened, allowing pressurised carbon dioxide in first store 250a to pass through the ejector 260 from the motive fluid inlet 260m to the outlet 260out. This results in a drop in pressure at inlet 260in. Subsequently, valve 222a may be opened, allowing carbon dioxide from the source 202a-d to be drawn into the inlet 260in, becoming entrained in carbon dioxide flowing from the first store 250a to the second store 250b via the ejector 260. Thus, further carbon dioxide is drawn from the source 202a-d and stored in store 250b without a requirement to operate the mechanical pump 210.

[0076] In some embodiments one or more mechanical pumps may be provided in the line 222 between the source 202a-d and pumping inlet 260in to assist the ejector 260 to draw carbon dioxide to the pumping inlet 260in. Embodiments of the invention have the advantage that, because further carbon dioxide may be drawn from the source 202a-d and stored in a store 250b without a requirement to operate the mechanical pump 210, the apparatus 200 can continue to store carbon dioxide even during times when the mechanical pump 210 cannot be operated, such as during maintenance periods or in the event of a failure of the pump 210.

[0077] It is to be understood that one or more further stores 250 may be provided in addition to the first and second stores 250a, 250b.

[0078] As noted above, both the mechanical pump 210 and the ejector 260 may be used to pump carbon dioxide from the source 202a-c into respective different stores 250 such that whilst the mechanical pump 210 is supplying carbon dioxide from the source 202a-d to (say) a third store, the first store 250a is used to drive the ejector 260 to draw carbon dioxide from the source 202a-d to the second store 250b. This mode of operation may be employed when it is expedient to do so, for example during periods of peak demand for the storage of carbon dioxide.

[0079] It is to be understood that if the pressure of carbon dioxide in the first store 250a falls below a required level following a period of operation of the ejector 260, the mechanical pump 210 may be used to recharge the first store 250a with pressurised carbon dioxide.

[0080] It is to be understood that, in some embodiments, the first, second and any further stores 250a, 250b may be in the form of a geological structure other than a natural gas well or oil well such as one or more disused aquifers such as saline aquifers or any other suitable geological features. In some embodiments, geological features such as disused mines (such as coal or salt mines) or any other suitable mine such as a mineral mine may be used. Other forms of store may be used such as caverns or any other suitable store in the form of a geological feature including saline aquifers. Stores in the form of a fabricated vessel such as a steel vessel, such as a stainless steel vessel, may be useful in some embodiments.

[0081] It is to be understood that the use of an ejector 260 in harnessing the power of fluid stored under pressure has the advantage that ejectors 260 are typically resilient to the pumping of gas / liquid mixtures. Thus if a mixture of gas and liquid is expelled from store 250a and provided to the motive inlet of the ejector 260, the ejector 260 will continue to function and draw fluid from the source 202a-d into the ejector 260 and output the mixture from the outlet 260out. Similarly, if liquid is present in the gas supplied from the source 202a-d, the ejector 260 is able to pump the gas / liquid mixture. In some embodiment, the pressurised fluid may be subject to a phase separation process prior to a portion of the separated fluid being supplied to the motive fluid inlet of the ejector. For example, where the pressurised fluid comprises an oil / gas mixture, separation of oil from the gas may be performed, and the separated gas (or oil) used as the motive fluid for the ejector 260.

[0082] In some embodiments, once a certain minimum pressure has been reached in a given store 250a, such as a pressure of 20bar, the pressure of gas stored in that store 250a may be used to drive an ejector 260 to draw gas from the source 202a-d in order to fill another store 250b with gas to be stored.

[0083] In some embodiments, the first store 250a may be a fresh or partially depleted natural gas or oil well having sufficient pressure of oil or gas to power the ejector 260. The pressure of oil or gas in the first store 250a may be used to power the ejector 260 to pump gas from storage vessel 202 (FIG. 2) or source 202a-d (FIG. 3) to second store 250b. Thus, it is to be understood that in some embodiments the pump 210 may be omitted.

[0084] FIG. 4 illustrates apparatus 300 according to a further embodiment of the invention applied to a scenario corresponding to that illustrated in FIG. 1, in which three stores 350a-c are provided. It is to be understood that apparatus according to embodiments of the present invention are suitable for use in scenarios having more than three stores.

[0085] It can be seen that, in a similar manner to the arrangement of FIG. 2, the mechanical pump 310 may be used to feed carbon dioxide from a source 302a-d to the first, second or third stores 350a-c via a pipeline 320, the stores 350a-c being connected in parallel to the mechanical pump 310. A respective valve 320a1 , 320a2, 320a3 allows each respective store 350a-c to be selectively isolated from the mechanical pump 310.

[0086] In the embodiment illustrated each store 350a-c is in the form of a disused gas well and has a relatively low pressure of gas therein, such as residual natural gas at a pressure in the range 5-10 bar, for example. Other forms of store 350, whether subsea or onshore, may be used in embodiments of the invention. The stores 350a-c may be used in embodiments of the present invention to store other gases or compressible fluids therein instead of or in addition to carbon dioxide. In the arrangement shown in FIG. 4 the carbon dioxide from the mechanical pump 310 may be fed to the stores 350a-c via a respective gas rig 355a-c. In some alternative embodiments one or all of the rigs 355a-c may not be present and the corresponding store (well) 350a-c may be accessed directly e.g. via a hub such as a subsea hub or by a direct connection to the mechanical pump 310. In some arrangements one or more of the wells 350a — c may be onshore wells.

[0087] In the embodiment of FIG. 4 an ejector 360 (shown in more detail in FIG. 5) is provided between the first and second stores 350a, 350b and between the second and third stores 350b, 350c. The first ejector 360a has a motive fluid inlet 360am coupled to the first store 350a via a line 323 and valve 323a and a pumping outlet 360aout coupled to the second store 350b via a line 324 and valve 324a. Similarly, the second ejector 360b has a motive fluid inlet 360bm coupled to the second store 350b via a line 323’ and a valve 323a’ and a pumping outlet 360bout coupled to the third store 350c via a line 324’ and a valve 324a’. The pumping inlets 360ain, 360bin of both ejectors 360a, 360b are coupled to the fluid source 302a-d via respective lines 322, 322’ with respective valves 322a, 322a’ provided therein to isolate the respective ejectors 360a, 360b from the source 302a-d. Line 322 couples the inlet 360ain of the first ejector 360a to the source 302a-d via valve 322a whilst line 322 and additional portion 322’ coupled to line 322 couple the pumping inlet 360bin of the second ejector 360b to the source 302a-d via valve 322a’.

[0088] It is to be understood that pipelines 322, 322’ may have a diameter of around 28 inches (around 71cm) in some embodiments. Other diameters may be useful in some embodiments.

[0089] In one operational method, the mechanical pump 310 is used to charge the first store 350a to a first pressure suitable for powering the first ejector 360a as described below. In some arrangements a minimum pressure of around 20 bar may be desirable in order to power the ejector 360a. However it is to be understood that the desired pressure may be dependent on the ejector design and may be adjusted to suit a given installation requirement. It is to be understood that the first pressure may be any suitable pressure, for example a pressure in the range 20-150 bar, optionally in the range 40-50 bar, optionally in the range 100-150 bar.

[0090] In order to charge the first store 350a, valve 320a1 is opened and valves 320a2, 320a3 and valve 323a are closed in order to isolate the mechanical pump 310 and first store 350a from the second and third stores 350b, 350c. Once the first pressure is reached in the first store 350a, valve 320a1 is closed in order to isolate the mechanical pump 310 from the first store 350a in addition to the second and third stores 350b, 350c.

[0091] Valves 322a, 323a, 324a may then be opened to employ ejector 360a to direct carbon dioxide from the first store 350a to the second store 350b, drawing gas from one or more of sources 302a-d to the second store 350b through inlet 360ain. During this period, the mechanical pump 310 may be employed to pressurise third store 350c by opening valve 320a3 if desired.

[0092] When the pressure of carbon dioxide in the first store 350a falls to a value precluding a suitable pumping speed of gas from one or more of sources 302a-d, such as a pressure in the range 15-20 bar, valves 322a, 323a, 324a may be closed. The mechanical pump 310 can then be used to pump carbon dioxide into the first store 350a to recharge the pressure of carbon dioxide stored therein with carbon dioxide from the source 302a-d. Depending on the relative pressure of gas in the second and third stores 350b, 350c, second ejector 360b may be employed to draw carbon dioxide from the source 302a-d into the third store 350c using the carbon dioxide stored in the second store 350b as the motive fluid to drive the ejector 360b. That is, with valves 320a2 and 320a3 closed, valves 322a’, 323a’ and 324a’ may be opened. This allows high pressure gas in store 350b to enter the motive inlet 360bm of second ejector 360b, causing a drop in pressure at inlet 360bin, drawing carbon dioxide from source 302a-d into the pumping inlet 360bin where it becomes entrained in motive fluid passing through the ejector 360b from the second store 350b to the third store 350c.

[0093] This operational mode may be referred to as a cascade mode of operation or pressure cascade, since the pressure of gas in one store 350a is used to power an ejector 360a to increase the pressure of gas stored in another store 350b, which is in turn used to drive an ejector 360b to increase the pressure of gas stored in yet another store 350c. It is to be understood that this does not preclude the use of a mechanical pump 310 to supplement the pumping of gas from the source 302a-d into one or more of the stores 350a-c to boost the pressure of gas stored therein.

[0094] It is to be understood that, by operating the mechanical pump 310 to increase the pressure of gas from a source 302a-d in a first store 350a, and then using the pressure of gas in the first store 350a to power an ejector 360 to increase the pressure of gas from the source 302a-d in a second store 350b, the mechanical pump 310 may be made available to charge the pressure of gas in a further store, such as the third store 350c or a fourth store (not shown). The rate at which carbon dioxide may be stored in the available stores 350a-c (and optionally a fourth or further store) by means of the apparatus 300 may be increased, for example during periods of peak demand for storage.

[0095] In some embodiments, the pumping outlet 360aout of the first ejector 360a may be selectively connected by means of a valved bypass pipeline (not shown) connected between points A and B of FIG. 3, to the third store 350c substantially directly, bypassing the second ejector 360b. Accordingly, the pressure of gas in the first store 350a may be used to pump gas from the source 302a-d to the third store 350c by opening the valve in the valved bypass pipeline.

[0096] Alternatively or in addition, in some embodiments gas from the first store 350a may be supplied to the motive inlet 360bm of the second ejector 360b via a further valved pipeline connecting points A’ and B’, whereby the second ejector 360b may be driven by the pressure of gas in the first store 350a. In some embodiments, the first and second ejectors 360a, 360b may be driven by the pressure of gas in the first store 350a and used to pump gas from the source 302a-d into the third store 350c substantially simultaneously.

[0097] In some embodiments the apparatus 300 may be operable to allow the first and second ejectors 360a, 360b to draw gas to be stored from the same and / or different respective sources.

[0098] In some embodiments, the apparatus 300 may be operable to allow the first and second ejectors 360a, 360b to be powered by the pressure of gas stored in respective first and second stores 350a, 350b and to feed gas to the same store 350c or to different respective stores 350 substantially simultaneously.

[0099] In some embodiments, the apparatus 300 may be operable to allow the first and second ejectors 360a, 360b to be powered by the pressure of gas stored in the same store 350a and to feed gas to the same store 350c or to different respective stores 350 substantially simultaneously. In a variation on the arrangement of FIG. 4, one or more of the wells 350a, 350b, 350c may be high pressure wells that are pressurised with natural gas or oil, or other fluid, such as virgin or untapped fields or wells. The high pressure well may be used to power an ejector to store a gas such as carbon dioxide in a low pressure well, without requiring use of a mechanical pump to pressurise the high pressure well. Thus, in some embodiments, including the embodiments described herein, the mechanical pump is not required and may be omitted.

[0100] FIG. 6 illustrates such an embodiment. The arrangement of FIG. 6 is similar to that of FIG. 3, but with the mechanical pump 210 and associated pipe 220 and valve 220a omitted. Like features of the embodiment of FIG. 6 to that of the embodiment of FIG. 3 are otherwise shown with like reference numerals. In the embodiment of FIG. 6, the fluid store 250a is a natural store containing fluid under pressure such as an oil or gas well containing natural oil or gas that has formed in the well and is under natural pressure. The natural pressure of fluid in the well can be used to drive the ejector 260 to pump carbon dioxide from a source 202 such as 202a, 202b, 202c, 202d into a second store 250b. The second store may be any suitable store such as another natural store having capacity to receive carbon dioxide under pressure, such as a spent or partially spent oil or gas well, an aquifer, another geological structure, or a fabricated pressure vessel such as a pressure vessel formed from one or more of a suitable material such as steel, aluminium, concrete, a plastics material or other suitable material.

[0101] Some embodiments of the present invention may be understood by reference to the following numbered clauses:

[0102] 1. A method comprising: releasing a first fluid under pressure from a first, motive, fluid store and supplying the fluid to a motive fluid inlet of a first ejector; drawing a primary fluid into the pumping inlet of the ejector from a primary fluid source by means of the fluid supplied to the motive fluid inlet; storing fluid output from an outlet of the ejector in a second fluid store.

[0103] 2. A method according to clause 1, comprising pumping primary fluid from the primary fluid source into the first, motive, fluid store by means of a mechanical pump.

[0104] 3. A method according to clause 2 comprising: pumping fluid from the primary source or further source of fluid into a further fluid store by means of the mechanical pump whilst fluid from the first fluid store is supplied to the motive fluid inlet of the first ejector.

[0105] 4. A method according to any preceding clause whereby: the first fluid store is a geological store, optionally one selected from amongst a well, a mine, a cavern and an aquifer.

[0106] 5. A method according to clause 4 wherein the first fluid store is an oil well or gas well and the step of releasing the first fluid under pressure from the first fluid store and supplying the fluid to a motive fluid inlet of the first ejector comprising releasing oil and / or gas from the first fluid store and supplying the fluid to the motive fluid inlet of the first ejector.

[0107] 6. A method according to any preceding clause whereby: the second fluid store is a geological store, optionally one selected from amongst a well, a mine, a cavern and an aquifer.

[0108] 7. A method according to any preceding clause whereby the fluid drawn from the primary or further fluid source comprises carbon dioxide, optionally whereby the fluid is at least 50% carbon dioxide, further optionally whereby the fluid is at least 75% carbon dioxide, further optionally whereby the fluid consists substantially of carbon dioxide.

[0109] 8. A method according to any preceding clause comprising releasing fluid stored in the second fluid store and supplying the fluid to a motive fluid inlet of a second ejector.

[0110] 9. A method according to clause 8 comprising drawing fluid from the primary or further fluid source into the pumping inlet of the second ejector by means of the fluid supplied to the motive fluid inlet; storing fluid output from an outlet of the second ejector in a third fluid store.

[0111] 10. Apparatus comprising: a first ejector, wherein a motive inlet of the first ejector is arranged to be coupled to a first, motive, fluid store, a pumping inlet of the first ejector is arranged to be coupled to a primary or further fluid source, and the outlet of the first ejector is arranged to be coupled to a second fluid store, the apparatus being configured to supply fluid under pressure from the first fluid store to the motive inlet of the first ejector and to pump fluid from the primary or further fluid source to the second fluid store by means of the first ejector.

[0112] 11. Apparatus according to clause 10 comprising a mechanical pump, wherein an inlet of the mechanical pump is arranged to be coupled to the primary or further source of fluid and an outlet of the mechanical pump is arranged to be coupled to the first fluid store, the apparatus being configured to pump fluid from the primary or further source to the first fluid store by means of the mechanical pump.

[0113] 12. Apparatus according to clause 11 configured to: pump fluid from the primary source or further source of fluid into a further, motive, fluid store by means of the mechanical pump whilst fluid from the first fluid store is supplied to the motive fluid inlet of the first ejector.

[0114] 13. Apparatus according to any one of clauses 10 to 12 wherein the first fluid store is a geological store, optionally one selected from amongst a well, a mine, a cavern and an aquifer.

[0115] 14. Apparatus according to clause 13 wherein the first fluid store is an oil well or gas well comprising oil and / or gas under pressure, the apparatus being configured to supply oil and / or gas under pressure from the first fluid store to the motive inlet of the first ejector and to pump fluid from the primary or further fluid source to the second fluid store by means of the first ejector.

[0116] 15. Apparatus according to any one of clauses 10 to 14 wherein the second fluid store is a geological store, optionally one selected from amongst a well, a mine, a cavern and an aquifer.

[0117] 16. Apparatus according to any one of clauses 10 to 15 wherein the fluid drawn from the primary or further fluid source comprises carbon dioxide, optionally whereby the fluid is at least 50% carbon dioxide, further optionally whereby the fluid is at least 75% carbon dioxide, further optionally whereby the fluid consists substantially of carbon dioxide.

[0118] 17. Apparatus according to any one of clauses 10 to 16 configured to release fluid stored in the second fluid store and supply the fluid to a motive fluid inlet of a second ejector. 18. Apparatus according to clause 17 configured to draw fluid from the primary or further fluid source into the pumping inlet of the second ejector by means of the fluid supplied to the motive fluid inlet, and store fluid output from an outlet of the second ejector in a third fluid store.

[0119] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of the words, for example “comprising” and “comprises”, means “including but not limited to”, and is not intended to (and does not) exclude other moieties, additives, components, integers or steps.

[0120] Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0121] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.

Claims

CLAIMS:

1. A method comprising: pumping fluid from a first source of fluid into a first, motive, fluid store by means of a mechanical pump and storing the fluid under pressure in the first fluid store; releasing fluid under pressure from the first fluid store and supplying the fluid to a motive fluid inlet of a first ejector; drawing further fluid from the first or a further fluid source into the pumping inlet of the first ejector by means of the fluid supplied to the motive fluid inlet; storing fluid output from an outlet of the first ejector in a second fluid store.

2. A method according to claim 1 comprising: pumping fluid from the first source or further source of fluid into a further, motive, fluid store by means of the mechanical pump whilst fluid from the first fluid store is supplied to the motive fluid inlet of the first ejector.

3. A method according to claim 1 or claim 2 whereby: the first fluid store is one selected from amongst a well, a mine, a cavern and an aquifer.

4. A method according to any preceding claim whereby: the second fluid store is one selected from amongst a well, a mine, a cavern and an aquifer.

5. A method according to any preceding claim whereby the fluid drawn from the first or further fluid sources comprises carbon dioxide, optionally whereby the first and second fluid is at least 50% carbon dioxide, further optionally whereby the first and second fluid is at least 75% carbon dioxide, further optionally whereby the first and second fluid consists substantially of carbon dioxide.

6. A method according to any preceding claim comprising releasing fluid stored in the second fluid store and supplying the fluid to a motive fluid inlet of a second ejector.

7. A method according to claim 6 comprising drawing second fluid from a fluid source into the pumping inlet of the second ejector by means of the fluid supplied to the motive fluid inlet;storing fluid output from an outlet of the second ejector in a third fluid store.

8. A method according to claim 7 whereby the fluid source from which second fluid is drawn is the first or a further fluid source.

9. Apparatus comprising: a mechanical pump; and a first ejector, wherein an inlet of the mechanical pump is arranged to be coupled to a first source of fluid and an outlet of the mechanical pump is arranged to be coupled to a first fluid store, the apparatus being configured to pump fluid from the first source to the first fluid store by means of the mechanical pump; and wherein a motive inlet of the first ejector is arranged to be coupled to the first fluid store, a pumping inlet of the first ejector is arranged to be coupled to the first or further fluid source, and the outlet of the first ejector is arranged to be coupled to a second fluid store, the apparatus being configured to supply fluid under pressure from the first fluid store to the motive inlet of the first ejector and to pump fluid from the first or further fluid source to the second fluid store by means of the first ejector.

10. Apparatus according to claim 9 configured to: pump fluid from the first source or further source of fluid into a further, motive, fluid store by means of the mechanical pump whilst fluid from the first fluid store is supplied to the motive fluid inlet of the first ejector.

11. Apparatus according to claim 9 or claim 10 wherein the first fluid store is one selected from amongst a well, a mine, a cavern and an aquifer.

12. Apparatus according to any one of claims 9 to 11 wherein the second fluid store is one selected from amongst a well, a mine, a cavern and an aquifer.

13. Apparatus according to any one of claims 9 to 12 whereby the fluid drawn from the first or further fluid sources comprises carbon dioxide, optionally whereby the first and second fluid is at least 50% carbon dioxide, further optionally whereby the first and second fluid is at least 75% carbon dioxide, further optionally whereby the first and second fluid consists substantially of carbon dioxide.14 Apparatus according to any one of claims 9 to 13 configured to release fluid stored in the second fluid store and supply the fluid to a motive fluid inlet of a second ejector.

15. Apparatus according to claim 14 configured to: draw second fluid from a fluid source into the pumping inlet of the second ejector by means of the fluid supplied to the motive fluid inlet; and store fluid output from an outlet of the second ejector in a third fluid store.

16. Apparatus according to claim 15 whereby the fluid source from which second fluid is drawn is the first or a further fluid source.

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