Method for operating gas deposits and gas reservoirs

Abstract

The invention relates to a method for operating natural gas deposits or natural gas reservoirs which are converted into hydrogen reservoirs. Natural gas is extracted from the gas reservoir or from the gas deposit, and the extracted natural gas is subjected to a splitting process, thus producing hydrogen, wherein the hydrogen is injected back into the deposit or reservoir, and the process of splitting the natural gas is carried out before or when the cushion gas pressure is reached. The hydrogen is injected such that at least the cushion gas pressure is maintained.

Description

[0001] Procedures for operating gas deposits and gas storage facilities

[0002] The invention relates to a method for operating gas deposits and gas storage facilities according to the preamble of claim 1.

[0003] It is known that in order to extract liquid raw materials from deposits, in particular natural gas or crude oil, these deposits can be pressurised with a gas in order to ensure sufficient pressure for the extraction of residual volumes, or to flush them with a gas in order to displace hydrocarbons remaining in the deposit or to entrain them in the gas flow.

[0004] Either nitrogen or carbon dioxide is used for this purpose, with the use of carbon dioxide now also being used to sequester carbon dioxide in depleted deposits, thus generating a double benefit.

[0005] An overview of Enhanced Gas Recovery, i.e. the removal of residual gas using CO2, is available from "Journal of Petroleum Science and Engineering", 196 (2021) "CO2 enhanced gas recovery and sequestration in depleted gas reservoirs: review", Ahmed Hamza et.al., in which an overview of the known processes and problems is presented.

[0006] Fundamentally, during a gas-gas exchange in a reservoir, physical and chemical processes take place that are not limited to the displacement of one gas by another. In addition, adsorption processes of the introduced displacement gas take place in pores and on the rocks forming the pores, and desorption processes of the gas to be displaced take place there. As is well known in these processes, equilibria are established.

[0007] Also from AT Turta, SSK Sim, AK Singhai, BF Hawkins, Alberta Research Council, Journal of Canadian Petroleum Technology, October 2008, Vol. 47, No. 10 is an overview of residual gas removal by gas-gas displacement, in particular using CO2 and N2 with CO2.

[0008] The same authors provide an overview of the factors that determine gas-to-gas displacement efficiency in the same journal, in the August 2009 issue, Vol. 48, No. 8. Here, too, nitrogen and carbon dioxide are used, as well as combustion gases.

[0009] The expulsion of residual natural gas by CO2 is also known from "Society of Petroleum Engineers, Enhanced Gas Recovery by CO2 Injection and Sequestration: Effect of Connate Water Salinity on Displacement Efficiency"; MK Abba et.al., 2017.

[0010] Despite the now critically scrutinized use of fossil fuels, natural gas remains a highly valuable raw material, particularly for the chemical industry. Therefore, it is essential to effectively exploit existing natural gas reserves. However, it is important to keep costs low, which is why carbon dioxide is a cheap and, if sequestered, also a good raw material for extracting natural gas.

[0011] And, as explained in the aforementioned publications, carbon dioxide is also extracted along with the extracted natural gas, which must be separated from the natural gas and returned. This naturally also applies to gas mixtures with nitrogen or other gases. This is based on the described equilibrium processes. The necessary processes and equipment are known to those skilled in the art.

[0012] The equilibrium processes during adsorption / desorption mean that the displacement of natural gas is only possible to a certain extent.

[0013] In particular, it is known that extraction at the end of a storage or storage period involves such high costs that economically viable exploitation is difficult or impossible.

[0014] DE 10 2010 035 260 Al discloses the exploitation of natural gas deposits with hydrogen and its recovery.

[0015] DE 10 2010 034 711 Al describes the extraction of natural gas using hydrogen extracted from the natural gas. In this process, the methane in the natural gas is reacted with water. DE 10 2010 031 777 Al describes the storage of hydrogen in natural gas reservoirs. This involves continuously analyzing the gas mixtures produced in the gas grid and reacting with them at the point of consumption.

[0016] From DE 10 2010 020 762 A1 a method for the amplification and transport of renewable energies is known, in which electrolytically produced hydrogen is to be supplied to a natural gas pipeline and the gas mixture is supplied to a point of consumption.

[0017] The object of the invention is to efficiently convert existing natural gas storage facilities or natural gas deposits into hydrogen storage facilities.

[0018] The problem is solved by a method having the features of claim 1.

[0019] Advantageous further training is indicated in the dependent subclaims.

[0020] According to the invention, a natural gas reservoir is converted into a hydrogen reservoir, or an under-extracted reservoir is converted into a hydrogen reservoir. Instead of removing existing cushion gas (CH4) and then introducing hydrogen, the invention instead involves flushing and realizing volume effects. The invention allows for time and cost savings and allows for easily controllable operation.

[0021] The inventors recognized that the conversion of existing natural gas storage facilities, and especially porous natural gas storage facilities, to hydrogen storage facilities is likely to result in mixing of natural gas and hydrogen over extended periods. Therefore, for efficient conversion and operation, it is necessary to take this possible mixing into account.

[0022] The total amount of gas contained in the storage tank can be divided into working gas and cushion gas.

[0023] The working gas—the actual purpose of a gas storage facility—is the amount of gas that can be injected and withdrawn. This portion is therefore the usable gas volume that can be marketed. The cushion gas provides the necessary pressure to allow the working gas to be withdrawn from the storage facility at high rates, even at low storage levels. Furthermore, maintaining a minimum pressure may be necessary to ensure long-term integrity in underground storage facilities.

[0024] The required cushion gas quantity, as well as the pressures in a storage facility at which cushion gas would be pumped instead of working gas, cannot be specified in absolute terms. These values ​​vary from storage facility to storage facility and are defined for each storage facility. However, they are always known for the specific storage facility and are also subject to, for example, approval procedures. The specialist therefore knows exactly what is meant by cushion gas and working gas and will be able to apply this to the specific case without further ado.

[0025] In pore storage facilities with aquifer influence, the cushion gas also prevents excessive water inflow into the pore space used for gas storage, which would otherwise lead to a reduction in the usable storage volume. This reduction has been observed in individual storage facilities, both in the loss of existing cushion gas and in the loss of potential working gas volume.

[0026] To avoid this, the cushion gas remains permanently in the storage and accounts for a proportion of 30 vol.% to 60 vol.% of the total storage volume.

[0027] The cushion gas limit is a lower limit for the emptying of a gas storage facility during ongoing storage operation, determined by official regulations or by geological / technical conditions.

[0028] It is well known in the art to also extract the cushion gas, for example, after storage operations have ended or when a storage facility is decommissioned. The cushion gas itself represents considerable value. This is a very lengthy process that can easily take several years.

[0029] The extraction of cushion gas requires a high level of technical effort, particularly with regard to the extraction systems, in order to empty the porous reservoir or convert it to a desired state. The inventors have recognized that if a natural gas storage facility or natural gas reservoir is converted into a hydrogen storage facility over a long operating period, natural gas components must be expected in the withdrawn hydrogen, making an additional processing step absolutely necessary to ensure the desired hydrogen purity. Without cushion gas exchange, unfavorable broad specifications and necessary oversizing can be expected for both the processing step and the withdrawal systems themselves. According to the invention, cushion gas exchange enables efficient processing and avoids oversizing.

[0030] With current technology, the cushion gas contained in a reservoir can be extracted up to an economically viable point. This point is defined by the technical specifications of the available facilities, including the pressure limit and the economic viability of the extraction process.

[0031] The more complex and larger the reservoir, the more technically complex and time-consuming the extraction of the cushion gas becomes. Furthermore, as reservoir pressure drops, the producible rate also decreases, leading to further delays. Complete extraction or complete depletion of the natural gas will never be possible for techno-economic and reservoir-related reasons.

[0032] After the removal of the hydrogen, the new, required cushion gas is introduced, which also takes some time depending on the available hydrogen source and technical equipment.

[0033] In addition, work must be carried out within a very large pressure window, as the pressure must first be reduced to extract the natural gas and then the pressure must be reapplied to introduce the new cushion gas, hydrogen.

[0034] Despite replacing the cushion gas from natural gas to hydrogen, this method still requires a certain amount of residual natural gas in the hydrogen working gas, at least initially. The inventors have recognized that the cushion gas plays a significant role in the inventive conversion of a natural gas storage facility or a natural gas reservoir still in production into a hydrogen storage facility.

[0035] One might assume that extracting the natural gas cushion gas and replacing it with hydrogen cushion gas would promote the conversion. However, the inventors have recognized that this is not the case.

[0036] In order to extract the purest hydrogen possible during the later operational phase of an H2 storage facility and to minimize processing costs, as much cushion gas natural gas as possible must be exchanged for cushion gas hydrogen when converting a natural gas storage facility to an H2 storage facility. If natural gas is extracted and subsequently injected as H2 cushion gas, significant time, technical, and commercial challenges must be overcome, as previously outlined.

[0037] According to the invention, the aforementioned disadvantages are avoided by continuously extracting the natural gas cushion gas from selected wells and decomposing it into hydrogen and carbon in a methane pyrolysis (or steam reforming) process. The hydrogen is then reinjected into the reservoir via selected wells.

[0038] This method maintains a consistently high pressure in and out of the reservoir, greatly facilitating the movement of the volume. Furthermore, it eliminates the need to modify the conveying equipment.

[0039] The drilling of any new storage wells also benefits from the invention, since higher pressure is associated with less damage to the area near the well and thus with an improvement in the well performance.

[0040] From a point in time, which can be modeled numerically in particular because the gas flow paths and volumes are known, pure natural gas is no longer produced because the hydrogen breaks through to the production wells and thus the natural gas share decreases.

[0041] According to the invention, however, operation continues until either the plants are no longer technically capable of handling the extracted gas mixture or until a point in time defined by reservoir simulation is reached at which sufficient hydrogen volume has been introduced so that the remaining natural gas volume can be separated in H2 storage operation with reasonable effort.

[0042] Due to the effect that the gas volume is doubled during methane pyrolysis, half of the extracted natural gas or the hydrogen produced from it can be used for other purposes, since this is not required for pressure maintenance. Methane steam reforming (SMR) can quadruple the gas volume.

[0043] In addition, this method preferentially flows through the areas of the reservoir that are then also effective during ongoing storage operations. Thus, the natural gas content is specifically reduced in these areas, further reducing subsequent purification costs.

[0044] Since the pressure does not drop in this variant, it is possible to use existing storage facilities for cushion gas exchange. In the case of extraction, new technical facilities would have to be built.

[0045] Compared to non-combustible cushion gas variants (nitrogen, CO2), when hydrogen is used as a cushion gas, the cushion gas can be extracted and recycled when the storage facility is decommissioned. This completely eliminates the need for final storage or aftercare for CO2, for example.

[0046] During later H2 storage operation, it is expected that the wells used to produce natural gas during the cushion gas exchange will produce even higher amounts of natural gas.

[0047] In contrast, the injectors will probably quickly provide hydrogen of the desired quality.

[0048] This effect can be used, if the above-ground facilities are appropriately equipped, to provide a uniform gas mixture for the storage facility and its processing. The wells containing more natural gas or the wells containing more hydrogen are subjected to greater loading. This means that, based on the gas analyses of the respective wells, the respective production gases are mixed together in such a way that the gas mixture remains as consistent as possible. This allows the storage facility and its processing to be designed and operated more efficiently and cost-effectively. The monitoring data provided by the observation wells, particularly regarding pressure, gas composition, and gas distribution, can be used to adjust the operation of the injection wells and production wells to replace as much natural gas as possible with hydrogen and to ensure efficient gas exchange in the shortest possible time.

[0049] The invention thus relates in particular to a method for operating natural gas deposits or natural gas storage facilities which are converted into a hydrogen storage facility, wherein cushion gas natural gas is withdrawn from the gas reservoir or gas storage facility and the withdrawn natural gas is subjected to splitting so that hydrogen is generated, wherein the hydrogen is injected back into the deposit or storage facility, wherein the splitting of the natural gas takes place before or when the cushion gas pressure is reached, wherein the injection of the hydrogen takes place in such a way that at least the cushion gas pressure is maintained.

[0050] Further development provides for the pressure to be kept high enough to prevent potential aquifer impacts from increasing.

[0051] A further development provides that the cushion gas content is maintained between 30 vol% and 60 vol% of the total volume.

[0052] Further development provides for the gas contained in a reservoir or storage facility to be extracted to an economically viable point, which is also defined by the technical specifications of the available facilities.

[0053] A further development provides that in continuous operation the natural gas cushion gas is extracted from selected first wells and decomposed in a methane pyrolysis or steam reforming process to produce hydrogen, whereby a portion of the hydrogen, which corresponds to or slightly exceeds the withdrawal volume, is reinjected into the reservoir via selected first or second wells, so that in this way the pressure in as well as the rate out of the reservoir is kept evenly at a high level, which greatly facilitates the movement of the volume.

[0054] A further development provides that if no more pure natural gas is produced because the hydrogen breaks through to the production wells and thus the natural gas share decreases, the operation will continue until either the plants are no longer technically able to handle the produced gas mixture or until a point in time defined by reservoir simulation is reached at which sufficient volume has been introduced so that the remaining natural gas volume can be removed during storage operation.

[0055] A further development provides that by doubling the input volume of natural gas during methane pyrolysis, half of the extracted gas is used outside the storage facility, as this is not necessary for pressure maintenance.

[0056] A further development provides that by increasing the input volume of natural gas by up to four times during steam reforming, significantly more than half of the extracted gas is used outside the storage facility, as this is not necessary for pressure maintenance.

[0057] A further development provides that in later hydrogen storage operation, the probes that were used to produce the natural gas-hydrogen mixture will produce higher proportions of natural gas, while the injectors essentially provide hydrogen, with either the probes containing more natural gas or the probes containing more hydrogen being subjected to a greater load, so that based on the gas analyses of the respective probes, the respective production gases are mixed with each other in such a way that the gas mixture remains as constant as possible and fluctuations in the gas composition are compensated.

[0058] A further development provides for the use of observation probes in addition to storage probes to monitor the development and distribution of hydrogen in the reservoir in order to observe the mean pressure development and the composition of the gas distribution.

[0059] A further development proposes that the data provided by the observation probes regarding pressure, gas composition, and gas distribution be used to adjust the operation of the injection probes and production probes so that as much natural gas as possible is replaced with hydrogen and efficient gas exchange occurs in the shortest possible time. A further development proposes that after the hydrogen breakthrough in the gas reservoir or gas storage facility, the mixture of hydrogen and natural gas is separated in a gas separation plant, and the natural gas is then split.

[0060] Further training provides for the recycling of all or part of the extracted hydrogen.

[0061] Further development provides for the recycling of extracted hydrogen or hydrogen from natural gas cracking or hydrogen from both sources.

[0062] A further development provides that at least the volume of hydrogen is pumped into the gas storage facility / gas reservoir as is the volume of gas pumped out of the reservoir in order to keep the production pressure / reservoir pressure constant or that more is pumped in to increase the pressure.

[0063] A further development provides that after the conversion and in a hydrogen storage phase, the extracted hydrogen is cleaned of any remaining natural gas or TOC in the gas separation plant.

[0064] A further development provides for the hydrogen to be supplied to the gas storage facility from outside or for the hydrogen that has already been supplied and separated in the gas separation plant to be returned to the gas storage facility or for both to be carried out.

[0065] Process according to one of the preceding claims, characterized in that the hydrogen separated in the gas separation plant is completely or partially returned to the deposit or is completely or partially used for further purposes.

[0066] A further development provides for the extracted hydrogen to be fully used and new hydrogen to be fed into the reservoir for storage.

[0067] A further development provides that the gas reservoir is operated with at least one probe through which gas is supplied or discharged.

[0068] A further development provides for the hydrogen extracted during the hydrogen storage phase to be purified of natural gas residues and TOC using a gas separation plant or other suitable equipment. A further development provides for the separated natural gas to be fed into a suitable grid or stored and further processed in some other way outside the gas storage facility.

[0069] A further development provides for the hydrogen to be supplied from outside and fed via the probe to the gas deposit in order to displace the natural gas there through appropriate physico-chemical processes.

[0070] A further development provides that the separation of the extracted gases takes place in the gas separation plant, whereby hydrogen is separated from the natural gas and is discharged via a line, whereby the line is divided into two lines, which can be selected by means of a valve or slide, whereby the separated hydrogen is discharged from the plant and used via one line and the hydrogen is fed back into the reservoir via the probe.

[0071] A further development provides that after the separation plant, at least one suitable device is used to set a desired pressure for feeding into the reservoir, extracting, further processing of the extracted gas mixture or for returning to the gas reservoir or for the aforementioned measures.

[0072] A further development provides for the use of at least one compressor as a device, which can be selected for the respective purpose via appropriate pipes and valves.

[0073] A further development provides for a separate facility for feeding into the reservoir, extracting, further processing of the extracted gas mixture or returning it to the reservoir, which is connected to the respective pipelines.

[0074] A further development provides for at least a second probe to be used in addition to the first probe.

[0075] A further development provides for the probes to be arranged at distant locations relative to the reservoir and, if necessary, at different elevations. A further development provides for hydrogen to be supplied to the gas reservoir from outside via the second probe, or hydrogen separated in the separation plant to be supplied to the reservoir, while the natural gas / hydrogen mixture is extracted via the first probe and the hydrogen is extracted during the hydrogen storage phase.

[0076] A further development provides for the probes to be operated alternately with regard to the feed-in or withdrawal.

[0077] The invention is explained by way of example using a drawing.

[0078] They show:

[0079] Figure 1: the pressure-time curves and the volume fraction of hydrogen and natural gas at the production well;

[0080] Figure 2: the pressure time courses related to the injected hydrogen volume in the

[0081] Relationship to the volume of natural gas produced and the volume share of hydrogen at the production well.

[0082] Figure 1 shows the pressure-time curves and the volume fraction of hydrogen and natural gas at the production well. This applies equally to reservoirs and storage facilities during conversion to hydrogen operation.

[0083] The time axis shows a hydrogen breakthrough after 50% of the injection time. This time point is designated 1. At the end of the time axis, the required natural gas volume is replaced by hydrogen volume to ensure an efficient and cost-effective purification design.

[0084] 2 denotes the technically maximum hydrogen concentration that can be processed in a fictitious cushion gas extraction system.

[0085] Figure 2 shows the pressure-time curves based on the injected hydrogen volume relative to the produced natural gas volume and the volume fraction of hydrogen at the production well. It also shows that the hydrogen injection begins slightly earlier than the cushion gas production in order to achieve a differential pressure between the injection well and the production well. This ensures that the injected hydrogen flows from the higher-pressure injection well to the lower-pressure production well.

[0086] Here, 1 again denotes the hydrogen breakthrough, and 3 schematically represents the technically maximum hydrogen concentration that can be processed in a fictitious hydrogen extraction plant. The discrepancy between the injected hydrogen volume and the produced natural gas volume results from the fact that the hydrogen breakthrough to the production well occurs at 1, which is why hydrogen is also produced from this point onward.

[0087] The invention is advantageous in that a gas reservoir can be optimally exploited and also used as an additional storage facility for energy carriers without contamination by inert displacement gases. Furthermore, the efficient separation of energetically usable displacement gas and natural gas is facilitated, both during the EGR phase and during the secondary use of the deposit or reservoir.

Claims

Claims 1. A method for operating natural gas deposits or natural gas storage facilities which are converted into a hydrogen storage facility, natural gas is withdrawn from the gas reservoir or gas storage facility and the withdrawn natural gas is subjected to splitting so that hydrogen is produced, the hydrogen being injected back into the deposit or storage facility, characterized in that the splitting of the natural gas takes place before or when the cushion gas pressure is reached, the injection of the hydrogen taking place in such a way that at least the cushion gas pressure is maintained.

2. Method according to claim 1, characterized in that the pressure is kept high enough so that the aquifer influence does not increase.

3. A method according to claim 1 or 2, characterized in that the cushion gas content is maintained between 30 vol.% and 60 vol.% of the total volume.

4. A method according to any one of the preceding claims, characterized in that the gas located in a reservoir or storage facility is extracted to an economically viable point which is defined by the pressure limits of the available facilities.

5. A method according to any one of the preceding claims, characterized in that in continuous operation the natural gas cushion gas is extracted from selected first wells and is decomposed in a methane pyrolysis or steam reforming so that hydrogen is produced, wherein a portion of the hydrogen which corresponds to or is slightly larger than the withdrawal volume is reinjected into the reservoir via selected first or second wells, so that in this way the pressure in as well as the rate out of the reservoir is kept uniformly at a high level, which greatly facilitates the movement of the volume.

6. Method according to one of the preceding claims, characterized in that when no more pure natural gas is produced because the hydrogen breaks through to the production wells and thus the natural gas proportion decreases, operation continues until either the plants are no longer technically able to handle the produced gas mixture or until a point in time defined by reservoir simulation is reached at which sufficient volume has been introduced so that the remaining natural gas volume can be removed during storage operation.

7. A process according to any one of the preceding claims, characterized in that, since the input volume of natural gas is doubled during methane pyrolysis, half of the extracted gas is used outside the storage facility, since this is not necessary for maintaining the pressure.

8. A method according to any one of claims 1 to 6, characterized in that during steam reforming the input volume of natural gas is increased up to four times, and significantly more than half of the extracted gas is used outside the storage facility, since this is not necessary for maintaining the pressure.

9. Method according to one of the preceding claims, characterized in that in the subsequent hydrogen storage operation, the probes which were used to produce the natural gas-hydrogen mixture also produce higher proportions of natural gas, while the injectors essentially provide hydrogen, wherein either the probes containing more natural gas or the probes containing more hydrogen are subjected to a greater load, so that on the basis of the gas analyses of the respective probes, the respective production gases are mixed with one another in such a way that the gas mixture remains as constant as possible and fluctuations in the gas composition are compensated.

10. Method according to one of the preceding claims, characterized in that, in addition to the storage probes, observation probes are also used to observe the development and distribution of hydrogen in the reservoir in order to observe the mean pressure development and the composition of the gas distribution.

11. Method according to one of the preceding claims, characterized in that the data supplied by the observation probes, in particular with regard to the pressure, the gas composition and the gas distribution, are used to adapt the operating modes of the injection probes and the production probes so that as much natural gas as possible is replaced by hydrogen and an efficient gas exchange takes place in the shortest possible time.

12. The method according to claim 1, characterized in that after the breakthrough of the hydrogen in the gas deposit or the gas storage, the mixture of hydrogen and natural gas is separated in a gas separation plant and the natural gas is subsequently split.

13. A process according to claim 2, characterized in that the extracted hydrogen is recycled in whole or in part.

14. A process according to claim 2 or 3, characterized in that the extracted hydrogen or hydrogen from natural gas cracking or hydrogen from both sources is recycled.

15. Method according to one of the preceding claims, characterized in that at least the volume of hydrogen is pumped into the gas storage / gas deposit which is pumped out of the deposit in order to keep the production pressure / reservoir pressure constant or more is pumped in in order to increase the pressure.

16. The method according to claim 1, characterized in that after the conversion and in a hydrogen storage phase, extracted hydrogen is purified from any remaining natural gas or TOC in the gas separation plant (4).

17. The method according to claim 1 or 2, characterized in that the hydrogen is supplied from outside to the gas storage facility (2) or the hydrogen which has already been supplied and separated in the gas separation plant (4) is returned to the gas storage facility (2) or both are carried out.

18. A process according to any one of the preceding claims, characterized in that the hydrogen separated in the gas separation plant (4) is completely or partially recycled into the deposit (2) is returned or is put to further use in whole or in part.

19. Method according to one of the preceding claims, characterized in that the extracted hydrogen is completely used and new hydrogen is fed into the reservoir (2) for storage.

20. Method according to one of the preceding claims, characterized in that the gas reservoir (2) is operated with at least one probe (3) through which gas is supplied or discharged 21. A process according to any one of the preceding claims, characterized in that the hydrogen extracted in the hydrogen storage phase is purified from natural gas residues and TOC by means of the gas separation plant or other suitable devices.

22. A method according to any one of the preceding claims, characterized in that the separated natural gas is fed into a corresponding network or is stored and further processed in some other way outside the gas deposit.

23. Method according to one of the preceding claims, characterized in that the hydrogen is supplied from outside and is fed via the probe (3) to the gas deposit (2) in order to displace the natural gas there by corresponding physico-chemical processes.

24. A method according to any one of the preceding claims, characterized in that the separation of the extracted gases takes place in the gas separation plant (4), hydrogen being separated from the natural gas and being discharged via a line (6), the line (6) being divided into two lines (7, 8) which can be selected by means of a valve (9) or slide (9), the separated hydrogen being discharged from the plant and being used via one line (7) and the hydrogen being fed back into the reservoir (2) via the probe (3, 11) via the other line (8).

25. Method according to one of the preceding claims, characterized in that after the separation plant (4) with at least one suitable device a desired Pressure is set for feeding into the reservoir, extraction, further processing of the extracted gas mixture or for returning to the gas reservoir (2) or for the aforementioned measures.

26. Method according to one of the preceding claims, characterized in that at least one compressor 12 is used as the device 12, which can be selected for the respective purpose via corresponding pipes and valves.

27. Method according to one of the preceding claims, characterized in that a separate device (12) is provided for the feeding into the reservoir (2), the discharge, the further processing of the discharged gas mixture or for the return to the reservoir (2), which device is connected to the respective lines (7, 8, 3, 11).

28. Method according to one of the preceding claims, characterized in that in addition to the first probe (3) at least one second probe (11) is used.

29. Method according to one of the preceding claims, characterized in that the probes (3, 11) are arranged at locations distant from one another and optionally also at different height levels with respect to the reservoir (2).

30. Method according to one of the preceding claims, characterized in that hydrogen is supplied from outside to the gas deposit (2) via the second probe (11) or hydrogen which has been separated in the separation plant (4) is supplied to the reservoir (2), while the natural gas / hydrogen mixture is withdrawn via the first probe (3) and the hydrogen is withdrawn in the hydrogen storage phase.

31. Method according to one of the preceding claims, characterized in that the probes (3, 11) are operated alternately with respect to the feed or withdrawal.

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