CA3140862A1 - System and method for energy storage using geological formations as reservoirs - Google Patents

Abstract

Provided herein are systems and methods for storing energy using a subterranean reservoir, comprising pumping a fluid from a lower pressure reservoir to a higher pressure reservoir and recovering the energy by allowing the fluid to flow through a turbine as it flows from the higher pressure reservoir to the lower pressure reservoir.

Description

SYSTEM AND METHOD FOR ENERGY STORAGE USING GEOLOGICAL FORMATIONS AS
RESERVOIRS
TECHNICAL FIELD
[0001] The following generally relates to a method of storing electricity for off peak use and more specifically relates to a pumped fluid storage system utilizing geological formations as reservoirs.
BACKGROUND

[0002] As energy companies shift their focus towards renewable energy sources such as wind and solar power, there is an increasing need for energy storage systems and methods.
Renewable energy cannot be produced on demand but rather is generated when it is available (e.g., solar energy is collected during sunny periods, wind energy is collected during windy periods). However, the energy demands may not match with the amount of renewable energy produced at any given time. Therefore, there is a need for systems and methods to store excess energy produced for later use when supply does not meet the demand.

[0003] One example of a system for storing excess energy is a pumped hydro storage strategy. During times of excess energy supply, water is pumped from a water body at a low elevation to another water body at higher elevation. The pumping phase is done during times of excess energy production to store energy for times of higher usage (or lower production).
During the electricity generation phase, water flows by gravity from the higher elevation body, through a turbine to the lower reservoir producing electricity. However, surface based pumped hydro storage solutions are limited by geographical requirements and can also have a negative impact on the sensitive ecology of these areas.

[0004] Other examples of energy storage systems include systems where oil or brine are moved between cavities at different depths in an underground salt dome or thick salt deposit of systems utilizing subsurface storage of carbon dioxide in reservoir formations.

[0005] Various methods exist for extraction of oil and gas from underground hydrocarbon reservoirs. Conventional gas wells are typically drilled vertical wells that tap into hydrocarbon (oil and gas) reserves that are easy to extract utilizing the natural pressure from the well and pumping operations. By contrast oil sands are a natural mix of sand, clay, water, and bitumen.
Bitumen is considerably viscous and does not flow like conventional crude oil.
As such, bitumen CPST Doc: 391662.1 Date recue / Date received 2021-11-30 is recovered from oil sands using either surface mining techniques or in situ techniques. For in situ oil sand methods, the bitumen reservoir is heated and the bitumen within flows into one or more production wells, leaving the formation rock of the bitumen reservoir in place.

[0006] Common in situ techniques include Steam Assisted Gravity Drainage (SAGD) and Cyclic Steam Stimulation (CSS). In SAGD, a pair of horizontally oriented wells are drilled into the bitumen reservoir, such that the pair of horizontal wells are vertically aligned with respect to each other and separated by a relatively small distance, typically in the order of several meters.
The well installed closer to the surface and above the other well is generally referred to as an injection well, and the well positioned below the injection well is referred to as a production well.
The injection well and the production well are then connected to various subsurface equipment, such as electric submersible pumps (ESPs) and sensors, and to equipment installed at a surface site. The injection well facilitates steam injection into the reservoir. Latent heat released by the injected steam mobilizes the bitumen by lowering its viscosity. The bitumen, in turn, drains due to gravity and is produced, along with condensed water, by the production well.
Typically, multiple well pairs are drilled substantially parallel to each other (e.g., from approximately 50 to greater than 120 m apart) to create what is referred to as a well pad.

[0007] In CSS, a single, vertical, production/injection well extending into a bitumen reservoir can be used for both steam injection and production. CSS typically involves three main phases, namely an injection phase, a shut in phase, and a production phase. During the injection phase, steam is injected through the production/injection well into the bitumen reservoir. Next, the bitumen reservoir is shut in to allow heat from the steam to reduce the viscosity of the bitumen in the reservoir. The bitumen of reduced viscosity can then be produced through the production/injection well, and the three-phase cycle can be repeated.

[0008] Whether the oil and gas are extracted by conventional wells or by an in situ process, once the bulk of the available hydrocarbon has been removed the remaining well is decommissioned. Decommissioning of spent wells can be an expensive process, therefore, it would be advantageous to find new uses for such late life (late state) wells and for the surrounding depleted hydrocarbon reservoirs.

[0009] In addition to hydrocarbon reservoirs, other types of geological formations are known which form natural reservoirs. These geological formations can include underground water reservoirs and salt domes or other types of natural reservoir or porous formations.
CPST Doc: 391662.1 Date recue / Date received 2021-11-30 SUMMARY

[0010] Methods and systems for storing and releasing energy have been developed.

[0011] In one aspect of the description, there is provided a method of storing energy and releasing the stored energy, comprising inputting electricity to pump a liquid from a low potential energy reservoir to a high potential energy reservoir, the reservoirs being separated by a geological formation and having a passage therebetween; wherein at least one reservoir is subterranean; and permitting the liquid in the high potential energy reservoir to flow through a turbine to a low potential energy reservoir, wherein the turbine generates electricity.

[0012] In an implementation of the method, the liquid is stored in the high potential energy reservoir for a period of time before permitting the liquid to flow through the turbine.

[0013] In an implementation of the method, storing the liquid in the high potential energy reservoir is achieved by closing the passage between the low potential energy reservoir and high potential energy reservoir to store energy; and permitting the liquid to flow through the turbine is achieved by opening the passage.

[0014] In an implementation of the method, the high potential energy reservoir is a high pressure reservoir and the low potential energy reservoir is a lower pressure reservoir than the high pressure reservoir. In a particular aspect, the difference in pressure between the high pressure reservoir and the lower pressure reservoir is in the range of 100 kPa to 50000 kPa kPa.

[0015] In an implementation of the method, the lower pressure reservoir is located at a lower elevation than the high pressure reservoir, such that the flow from the high pressure reservoir to the lower pressure reservoir is further assisted by gravity.

[0016] According to another aspect of the description there is provided a system for storing energy and releasing energy, the system comprising: a low potential energy reservoir and a high potential energy reservoir that are separated by a geological formation and having a passage therebetween; a liquid that can flow from the low potential energy reservoir through the passage to the high potential energy reservoir and from the high potential energy reservoir to the low potential energy reservoir; a pump to propel the liquid from the low potential energy reservoir to the high potential energy reservoir; and a turbine to generate electricity from energy produced when the liquid flows from the high potential energy reservoir to the low potential CPST Doc: 391662.1 Date recue / Date received 2021-11-30 energy reservoir; wherein at least one of the high potential energy reservoir and the low potential energy reservoir is subterranean.

[0017] In an implementation the system further comprises a mechanism to prevent the flow of the liquid from the high potential energy reservoir to the low potential energy reservoir during a period of energy storage.

[0018] In an implementation of the system the high potential energy reservoir is a high pressure reservoir and the low potential energy reservoir is a lower pressure reservoir than the high pressure reservoir. In a particular aspect, the differential in pressure between the high pressure reservoir and the lower pressure reservoir is in the range of about 100 kPa to about 50000 kPa.

[0019] In an implementation of the system the lower pressure reservoir is at a lower elevation than the high pressure reservoir, such that the flow from the high pressure reservoir to the lower pressure reservoir is further assisted by gravity.

[0020] In an implementation, the system can further comprise one or more additional high potential energy storage reservoirs and/or one or more additional low potential energy storage reservoirs wherein the additional storage reservoirs can be connected with additional passages and wherein the liquid can be selectively pumped from any one of the low potential energy storage reservoirs to one or more of the high potential energy storage reservoirs and wherein the passages comprise mechanisms to control the flow of liquid from the one or more of the high potential energy reservoirs to the one or more low potential energy reservoirs.

[0021] In an implementation, the system can include one or more additional pumps and/or one or more additional turbines.

[0022] Advantages of the system and method include exploiting potential energy differences between reservoirs, for example pressure differences, by pumping a fluid to a reservoir of higher potential energy when there is excess electricity and allowing the fluid to flow back to the reservoir of lower relative pressure in order to generate electricity at a time of need.
BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Embodiments will now be described with reference to the appended drawings wherein:
CPST Doc: 391662.1 Date recue / Date received 2021-11-30

[0024] FIG. 1 is an illustration of an energy storage system having high and low potential energy reservoirs depicting a period of excess energy storage where the energy is stored by pumping a fluid to the high potential energy reservoir.

[0025] FIG. 2 is an illustration of an energy storage system having high and low potential energy reservoirs depicting a period of energy generation where the energy is generated by a fluid flowing through a turbine from the high potential energy reservoir to a lower potential energy reservoir zone.

[0026] FIG. 3 is an illustration of an energy storage system depicting a low pressure reservoir located above a high pressure reservoir.

[0027] FIG. 4 is an illustration of an energy storage system showing an alternative configuration of the low pressure and high pressure reservoirs.

[0028] FIG. 5 is an illustration of an energy storage system where the pump and turbine are separated.

[0029] FIG. 6 is an illustration of an energy storage system where the reservoirs have a gas cap.

[0030] FIGS. 7a, 7b and 7c illustrate different configurations of the pump and turbine of the energy storage system.
DETAILED DESCRIPTION

[0031] The term "pumped fluid storage" is used to describe a method or system for storing energy by moving a fluid from a position of lower energy to a position of higher energy and subsequently recovering the energy by allowing the fluid to flow from the position of higher energy to a position of lower energy.

[0032] FIG.1 and FIG. 2 depict an embodiment of a pumped energy storage system and method. The system has two fluid storage reservoirs with a differential between them. The differential creates a reservoir of high potential energy (2) relative to a second reservoir of lower potential energy (4). The two reservoirs are connected by a passage (6). The system includes a pump (8) for moving the fluid to the higher energy reservoir and a turbine/generator (9) for converting released energy to electricity when the fluid flows back to the lower energy reservoir.
The passage also optionally includes a mechanism to prevent fluid flow (10) from the high CPST Doc: 391662.1 Date recue / Date received 2021-11-30 potential energy reservoir to the lower potential energy reservoir during a period of energy storage. FIG. 1 depicts the energy storage phase wherein the fluid is pumped from the lower potential energy reservoir to a high potential energy reservoir. This phase occurs during periods of excess electricity production. FIG. 2 depicts the energy generation phase wherein the fluid flows from the high potential energy reservoir (2) through a turbine (9) (or other generator) to the lower potential energy reservoir (4) to produce electricity. Generated electricity can optionally be fed back to the grid.

[0033] The terms "high potential energy reservoir" or "higher potential energy reservoir" are used to define a reservoir that has a higher potential energy than a second reservoir where the second reservoir is the "low potential energy reservoir" or "lower potential energy reservoir". It will be understood that these terms are used to define a difference in potential energy between reservoirs and the terms "high" and "low" are used to define the relative potential energy of one reservoir as compared to a second reservoir.

[0034] In one aspect the differential between the reservoirs is a pressure differential. Such that the high potential energy reservoir is at a higher pressure than the lower potential energy reservoir, (lower pressure reservoir). In one embodiment the pressure differential between the reservoirs is from about 100 kPa to about 50000 kPa. In a particular aspect, the pressure differential between the reservoirs is from about 1000 kPa to about 40000 kPa, in a further aspect the pressure differential is about 10000 kPa to about 30000 kPa. In another aspect the differential is at least about 1000 kPa, at least about 5000 kPa or at least about 10000 kPa.

[0035] In a particular example, following extraction, the depleted hydrocarbon reservoirs can exhibit differences in pressure. These pressure differences can be exploited in the present energy storage system by pumping a fluid to a reservoir of higher pressure when there is excess electricity and allowing the fluid to flow back to the reservoir of lower relative pressure in order to generate electricity at a time of need.

[0036] The terms, "high pressure reservoir" or "higher pressure reservoir"
are used to describe a reservoir that is under a higher pressure than a second reservoir which is identified as the "low pressure reservoir" or "lower pressure reservoir". It will be understood that these terms are used to define a difference in pressure between reservoirs and the terms high and low (or higher and lower) are used to define the relative pressure of one reservoir as compared to a second reservoir.
CPST Doc: 391662.1 Date recue / Date received 2021-11-30

[0037] In one example of the energy storage system, a fluid is pumped to a high pressure storage reservoir to store energy and the energy is recovered as the fluid flows through a turbine as it moves from the high pressure storage reservoir to a lower pressure storage reservoir. In a particular example, the pressure (P) in the high pressure storage reservoir is approximately 15000 kPag and the pressure (P) in the low pressure storage reservoir, or sink is approximately 5000 kPag.

[0038] In another aspect, the differential between the reservoirs is a height differential.
Surface based pumped hydro-storage strategies are limited by the available geological elevations or man-made elevated water bodies/reservoirs and are typically only meters, whereas the differential between hydrocarbon reservoir can be 1000 meters or more.
This height differential provides a significant advantage in the amount of energy that can be stored using a subterranean hydrocarbon reservoir.

[0039] In a further aspect the differential between the reservoirs can include both a height and pressure differential. In this way, the high energy zone can have both higher position and pressure than the lower energy zone, thereby further increasing the energy storage capacity of the system.

[0040] In another aspect the higher potential energy reservoir and the lower potential energy reservoir can be separated by a rock formation to mitigate cross flow between the zones.

[0041] A passage linking the reservoirs can be used to allow the fluid to move from one reservoir to the other. In one embodiment, a well completion can form the passage between the reservoirs. The well completion can be a vertical well as depicted in the figures or can be horizontal or slanted depending on the orientation of the reservoirs being connected.

[0042] The passage can optionally include a mechanism for preventing flow from the high potential reservoir to the low potential reservoir during energy storage periods is optionally provided. Various mechanisms can be envisioned for controlling the flow of fluid from the higher potential energy reservoir to the lower potential energy reservoir. In a particular example, a sleeve is provided which is moveable between a closed position, preventing fluid flow between the zones, and an open position which allows the fluid to flow. The sleeve can comprise a tubing deployed sleeve or casing deployed sleeve. Various mechanism will be known to one of CPST Doc: 391662.1 Date recue / Date received 2021-11-30 skill in the art for controlling the flow of fluid from the reservoirs into the passage or the flow through the passage.

[0043] In another embodiment the pump can be run to maintain the fluid in the higher potential energy reservoir. When the pump is stopped, the fluid flows to the lower potential energy reservoir.

[0044] The reservoirs of the present system and method include reservoirs formed within geological formations. Examples of such reservoirs include virgin or depleted hydrocarbon reservoirs, depleted gas cap and downhole drainage reservoirs, water bearing formations or salt caverns. Embodiments of the system and method can include combinations of different types of reservoirs. In a particular aspect the reservoir is in an overpressure or under-pressure state wherein the pressure in the reservoir is above or below hydrostatic pressure, respectively.

[0045] The reservoirs of higher and lower potential energy can both be subterranean as depicted in FIG. 1 and 2 or one of the reservoirs can be above ground. For example, a fluid can be pumped to a surface reservoir such as a water body and allowed to flow down to a subterranean reservoir through a turbine to generate electricity. The surface reservoir and subterranean reservoir can also exhibit a difference in pressure. The surface and subterranean reservoirs can also benefit from a combination of a difference in relative position (height) and pressure, to provide even more energy storage capacity. In one embodiment the surface reservoir/water body is a pond, which can include a tailings pond or other body of water created as a by-product of an industrial process such as bitumen extraction. In another embodiment the surface reservoir/water body is a storage tank.

[0046] The low potential energy reservoir and high potential energy reservoirs can have different orientations. For example, FIG. 3 depicts an embodiment of the energy storage system having a low pressure reservoir (24) that is located vertically higher than the high pressure reservoir (22). It is further understood that the reservoirs need not be stacked one above the other but can have different orientations and spatial arrangements.
Other configurations can include horizontal wells to access more reservoirs and increase storage capacity.

[0047] FIG. 4 illustrates another embodiment of the energy storage system where the reservoirs are horizontally spaced apart and are connected by passage (6) to allow flow of the fluid between the high pressure reservoir (22) and the lower pressure reservoir (24). During CPST Doc: 391662.1 Date recue / Date received 2021-11-30 periods of excess energy, energy is provided to the pump (8) which pumps the fluid from the lower pressure reservoir (24) to the high pressure reservoir (22). The mechanism to prevent fluid flow (10) is then moved to a closed phase to prevents the fluid from flowing from the high pressure reservoir back to the low pressure reservoir during the energy storage phase. During the energy production phase, the mechanism (10) is moved to an open position allowing the fluid to flow through the turbine (9) in passage (6) to generate energy.
Passage (6) can extend to the surface as depicted in FIG. 4 or it can be subterranean.

[0048] FIG. 5 illustrates yet another embodiment of the energy storage system, where the fluid is produced to a turbine (9) that can be located at the surface, and the fluid is then directed back down the casing to the second reservoir.

[0049] FIG. 6 illustrates a further embodiment wherein a gas cap (12) can be added to increase the pressure in the reservoir. Although FIG. 6 illustrates a gas cap in both reservoirs, the gas cap can be added to one or both of the reservoirs to maintain pressure during the energy storage cycles. The gas cap can be naturally occurring or can be created by supplying gas to the reservoir(s).

[0050] Other examples for increasing the pressure in one or more reservoirs include fracturing to increase the pressure in the reservoirs, or in situ combustion (of hydrocarbon) to create non-condensable gases. Another example for increasing pressure involves injecting water into a "hot zone" or geological feature having a temperature high enough to vaporize the water to create steam that can be used to maintain pressure in the reservoir.

[0051] It will be understood that various pumps, and the like can be used for moving the fluid from a reservoir of low potential energy to a reservoir of higher potential energy. Similarly, various turbines and the like can be used for converting energy from a flowing fluid into electricity. In one aspect a separate pump and turbine are used. FIG. 4 and 5 depict examples of systems with separate pump and turbine. In another aspect an electric submersible pump (ESP) is used to act as both pump and turbine. The use of an ESP has the advantage of reduced equipment. The use of an ESP also has the added advantages that production of the fluid up to the surface is not necessarily required. This opens up the opportunity to use fluids other than water, such as hydrocarbon, in a closed system.

[0052] The passage linking the two zones can be fitted with a pump or compressor (e.g., an ESP) and turbine for storing and extracting energy. These would typically be configured for CPST Doc: 391662.1 Date recue / Date received 2021-11-30 axial flow and could be constructed as a single unit or as separate units. For example, the blade row stages of the pump can be optimized to allow efficient reverse flow to also act as the turbine. FIG 7a shows a combined pump and turbine stages (50). In this example the electrical components motor/generator (52) are combined and the flow direction (54) changes with energy extraction or storage operation. Alternatively, the pump and turbine can share the same electrical drive/power generation components but use separate blade stages for optimal efficiency as depicted in FIG. 7b. In FIG 7b, the pump stages (56) are separate from the turbine stages (58) while the shared electrical components (60) drive both the turbine and pump. In this case, bypass flow passages (62) are used to direct flow to the pump or turbine, depending on flow direction. These bypass flow passages could be fitted with valves (64) to serve as a shutoff to flow in either direction. The valves can be used to control flow rate and/or flow direction and can be surface controlled or automated. A third option depicted in FIG. 7c is similar to the previous configuration, but with completely separate electrical components as well. FIG 7c shows pump stages (66) and an associated electrical motor (68) which are separate from turbine stages (70) and associated electric generator (72). In a further embodiment a compressor can be used in place of the pump in the various configurations of FIG. 7a-7c when the fluid is a gas.

[0053] To facilitate installation of downhole equipment and/or to limit energy loss with the flow, the diameter of passage between the reservoirs can be optimally larger than other portions of the well. This can be accomplished with underreaming techniques and expandable tubing and liners.

[0054] A further advantage offered by the use of the subterranean reservoirs over conventional surface based pumped hydro storage strategies is that there is less impact to the surface. This is the case even where a surface pump or surface reservoir water body are used in the system. Conventional pumped hydro strategies typically take advantage of geological formations such as mountains or gorges. The technology has therefore been limited by geography. The building of pumped energy systems on mountain sides can pose many challenges including the high cost of construction in difficult terrain and the environmental impact to these sensitive geological regions. In a particular example, the use of existing hydrocarbon reservoirs takes advantage of the existing structures so less new construction is required and any effects are limited to areas that have already been developed with minimal additional land disturbance.
CPST Doc: 391662.1 Date recue / Date received 2021-11-30

[0055] In a particular example, the geological formation forming the reservoir is late life hydrocarbon reservoir. The term "late life reservoir" or "late state reservoir" as used herein refers to a hydrocarbon reservoir that has been substantially depleted of hydrocarbon by extraction either through conventional gas or oil extraction methods or in situ bitumen extraction methods. Late life reservoirs can be used as low potential energy reservoirs and/or high potential energy reservoirs. A fluid can be moved from one reservoir having lower potential energy to a second reservoir having higher potential energy using excess renewable energy.
The fluid can be stored in the high potential energy reservoir for a period of time until the energy is required. The fluid can then produce energy at a time of need when it is allowed to flow back to the reservoir of lower potential energy. In one example the high and low potential energy reservoirs have a difference in pressure. The method can also take advantage of other differences between the reservoirs, such as height, which can lead to energy potential. In a particular embodiment there can be a difference in height and pressure that contribute to the energy potential in the high energy reservoir.

[0056] Late life oil-sands reservoirs (in situ reservoirs) can be uniquely in an "under-pressure" state. This means that water or other fluids stored in a second reservoir at a higher pressure, such as a tailing pond or vessel at the surface at atmospheric pressure would naturally flow down into the oilsands reservoir due to the unique pressure gradient. Therefore, older or late life oilsands reservoirs can be leveraged to take advantage of this unique property to enable the water to flow downwardly in the energy generation phase. This allows for the combined effect of the pressure differential and gravity to provide a significant energy storage capacity using a late life in situ reservoir. The "under-pressure" late life oil sands reservoir can also used in combination with another subterranean reservoir that is at a higher pressure.

[0057] In another example, reservoirs having naturally high pressure such as depleted conventional oil or gas reservoirs, can be used in the energy storage system and method of the application as the high energy storage reservoir and can be combined with a lower pressure reservoir which can be either subterranean or at the surface.

[0058] Another advantage of using late life hydrocarbon, virgin or depleted hydrocarbon or water bearing formations or salt caverns as reservoirs is that it can be possible locate renewable energy sources, such as wind turbines or solar panels, near existing reservoirs in order to take advantage of close proximity to energy storage.
CPST Doc: 391662.1 Date recue / Date received 2021-11-30

[0059] Additionally, the existence of many hydrocarbon wells in relatively close proximity in an oil producing region can allow for networks of energy storage facilities.
Taking advantage of multiple reservoirs in a particular geographic area could allow for the creation of a network of energy storage banks. It is contemplated that multiple high potential energy and/or low potential energy reservoirs can be combined in various combinations to create a network for energy storage. The reservoirs can be connected by passages having mechanisms for controlling the flow from one reservoir to another and the passages can further include multiple pumps to move the liquid from low to high energy reservoirs using excess electrical energy and multiple turbines or generators to produce electricity when the fluid flows from the high energy reservoirs to one or more low energy reservoirs. In one example, a liquid can be pumped from a low potential energy reservoir to a high potential energy reservoir and can then be directed to flow to a second low potential energy reservoir.

[0060] It is envisaged that the energy storage systems described herein can be connected directly to a renewable energy source to store excess energy produced during low demand periods. It is further envisaged that the energy storage systems described herein can also be connected to the power grid to feed stored energy to the grid during periods of high demand. In another embodiment the energy storage system can receive excess energy from the grid for storage. The storage system and method can work in power/energy shifting and ancillary services.

[0061] To identify reservoirs that can be suitable for the described system of energy storage, a geological review of candidate locations can be undertaken.
Simulations can also be run to identify reservoirs exhibiting the characteristics needed for the proposed system.

[0062] Various fluids can be used in the described method and system. In one aspect the fluid is liquid or substantially liquid. Water or aqueous solutions can be used as the fluid and can be obtained directly from the reservoir or from another source. It will be particularly advantageous to use fluids that are already available at the reservoir location. For example, the fluid can be hydrocarbon and can be hydrocarbon extracted from the reservoir.
In another example the fluid can be waste fluid from the hydrocarbon extraction process, such as tailings of formation water.

[0063] For simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.
CPST Doc: 391662.1 Date recue / Date received 2021-11-30 In addition, numerous specific details are set forth in order to provide a thorough understanding of the examples described herein. However, it will be understood by those of ordinary skill in the art that the examples described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the examples described herein. Also, the description is not to be considered as limiting the scope of the examples described herein.

[0064] The examples and corresponding diagrams used herein are for illustrative purposes only. Different configurations and terminology can be used without departing from the principles expressed herein. For instance, components and modules can be added, deleted, modified, or arranged with differing connections without departing from these principles.

[0065] The steps or operations in the flow charts and diagrams described herein are just for example. There may be many variations to these steps or operations without departing from the principles discussed above. For instance, the steps may be performed in a differing order, or some steps may be added, deleted, or modified.

[0066] Although the above principles have been described with reference to certain specific examples, various modifications thereof will be apparent to those skilled in the art as outlined in the appended claims.
CPST Doc: 391662.1 Date recue / Date received 2021-11-30

Claims (41)

Claims:

1. A method of storing energy and releasing the stored energy, comprising:
inputting electricity to pump a liquid from a low pressure reservoir to a high pressure reservoir, the reservoirs being separated by a geological formation and having a passage therebetween, wherein at least one reservoir is subterranean; and permitting the liquid in the high pressure reservoir to flow through a turbine to a low pressure reservoir, wherein the turbine generates electricity.

2. The method of claim 1, further comprising storing the liquid in the high pressure reservoir for a period of time before permitting the liquid to flow to through the turbine.

3. The method of claim 2, wherein storing the liquid in the high pressure reservoir is achieved by continuing to input electricity to the pump and permitting the liquid to flow through the turbine is achieved by discontinuing inputting electricity to the pump.

4. The method of claim 2, wherein storing the liquid in the high pressure reservoir is achieved by closing the passage between the low pressure reservoir and high pressure reservoir to store energy; and permitting the liquid to flow through the turbine is achieved by opening the passage.

5. The method of any one of claims 1-4, wherein the pressure difference between the high pressure reservoir and the lower pressure reservoir is in the range of 100 kPa to 50000 kPa kPa.

6. The method of any one of claims 1-5, wherein the lower pressure reservoir is located at a lower elevation than the high pressure reservoir, such that the flow from the high pressure reservoir to the lower pressure reservoir is further assisted by gravity.

7. The method of any one of claims 1 to 6, wherein at least one of the high pressure reservoir and the low pressure reservoir is a subterranean hydrocarbon reservoir, water bearing formation, or a salt cavern.

8. The method of any one of claims 1 to 7, wherein at least one of the high pressure reservoir and the low pressure reservoir is a hydrocarbon reservoir.

9. The method of claim 8, wherein the hydrocarbon reservoir comprises a late life in situ bitumen/oilsands reservoir.

10. The method of any one of claims 1 to 9, wherein both the low pressure and high pressure reservoirs are subterranean reservoirs.

11. The method of any one of claims 1 to 9, wherein the high pressure reservoir is at the surface and the low pressure reservoir is subterranean.

12. The method of any one of claims 1 to 9, wherein the high pressure reservoir is subterranean and the low pressure reservoir is at the surface.

13. The method of any one of claims 1 to 12, wherein the turbine is provided by an electric submersible pump (ESP), which is also used to perform the pumping.

14. The method of any one of claims 1 to 13, wherein the liquid is water or hydrocarbon.

15. The method of claim 14, wherein the water is recycled water from the hydrocarbon extraction.

16. The method of any one of claims 1 to 16, wherein a gas cap is formed in at least one of the high pressure reservoir and the low pressure reservoir to maintain the pressure in the reservoir.

17. The method of any one of claims 1 to 16, wherein naturally occurring or induced fractured zones are used to increase the permeability of the formation and to increase the pressure of the reservoir over its initial pressure.

18. The method of any one of claims 1 to 17, wherein the liquid is produced to the surface as it flows through the turbine.

19. The method of any one of claims 1 to 18, wherein the electricity input to the pump is obtained from a renewable energy source.

20. The method of any one of claims 1 to 19, wherein the electricity generated by the turbine is input to the power grid.

21. A system for storing energy, the system comprising:
a lower pressure reservoir and a higher pressure reservoir that are separated by a geological formation and having a passage therebetween, wherein the pressure in the higher pressure reservoir is higher than the pressure in the lower pressure reservoir;
a liquid that can flow from the lower pressure reservoir through the passage to the higher pressure energy reservoir and from the higher pressure reservoir to the lower pressure reservoir;
a pump to propel the liquid from the lower pressure reservoir to the higher pressure reservoir; and a turbine to generate electricity from energy produced when the liquid flows from the higher pressure reservoir to the lower pressure reservoir;
wherein at least one of the higher pressure reservoir and the lower pressure reservoir is subterranean.

22. The system of claim 21, further comprising a mechanism to prevent the flow of the liquid from the higher pressure reservoir to the lower pressure reservoir during a period of energy storage.

23. The system of claim 22, wherein the differential in pressure between the higher pressure reservoir and the lower pressure reservoir is in the range of about 100 kPa to about 50000 kPa.

24. The system of any one of claims 21 or 23, wherein the lower pressure reservoir is at a lower elevation than the higher pressure reservoir, such that the flow from the higher pressure reservoir to the lower pressure reservoir is further assisted by gravity.

25. The system of any one of claims 21 to 24, wherein at least one of the higher pressure reservoir and the lower pressure reservoir is a hydrocarbon reservoir, water bearing formation or a salt cavern.

26. The system of any one of claims 21 to 25, wherein at least one of the higher pressure reservoir and the lower pressure reservoir is a hydrocarbon reservoir.

27. The system of claim 26, wherein hydrocarbon reservoir comprises a late life in situ bitumen/oilsands reservoir.

28. The system of any one of claims 21 to 27, wherein both the lower pressure reservoir and higher pressure reservoir are subterranean.

29. The system of any one of claims 21 to 27, wherein the higher pressure reservoir is at the surface and the lower pressure reservoir is subterranean.

30. The system of any one of claims 21 to 27, wherein the higher pressure reservoir is subterranean and the lower pressure reservoir is at the surface.

31. The system of any one of claims 21 to 30, wherein the turbine is provided by an ESP, which is also used as the pump.

32. The system of any one of claims 21 to 31, wherein the liquid is hydrocarbon or water.

33. The system of claim 32, wherein the water is recycled water from the hydrocarbon extraction.

34. The system of any one of claims 21 to 33, wherein the system further comprises a renewable energy source to provide power to the pump.

35. The system of any one of claims 21 to 34, wherein the system further comprises a connection to the power grid.

36. The system of any one of claims 21 to 35, further comprising one more additional higher pressure reservoirs and/or one or more additional lower pressure reservoir, wherein the additional reservoirs may be connected with additional passages and wherein the liquid can be selectively pumped from one or more of the lower pressure reservoirs to one or more of the higher pressure storage reservoirs and wherein the passages comprise mechanisms to control the flow of liquid from the one or more higher pressure reservoirs to one or more of the lower pressure reservoirs.

37. The system of claim 36, further comprising one or more additional pumps and/or one or more additional turbines.

38. The system of any one of claims 21 to 30 and 32 to 37, wherein the pump and turbine are separate units and the system further comprises bypass flow passages.

39. The system of claim 38, wherein the bypass flow passages include valves to control the flow and/or flow direction.

40. The system of claim 39, wherein the valves are surface controlled or automated.

41. The system of any one of claims 36 to 40, wherein the pump and turbine are controlled by common electronics components or separate electronics components.