WO2024042850A1 - Procédé de stockage souterrain de dioxyde de carbone - Google Patents

Procédé de stockage souterrain de dioxyde de carbone Download PDF

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Publication number
WO2024042850A1
WO2024042850A1 PCT/JP2023/023959 JP2023023959W WO2024042850A1 WO 2024042850 A1 WO2024042850 A1 WO 2024042850A1 JP 2023023959 W JP2023023959 W JP 2023023959W WO 2024042850 A1 WO2024042850 A1 WO 2024042850A1
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carbon dioxide
pressure
shielding layer
hydrate
stratum
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PCT/JP2023/023959
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English (en)
Japanese (ja)
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洋二郎 池川
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電源開発株式会社
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/50—Carbon dioxide

Definitions

  • the present invention relates to a method for storing carbon dioxide underground.
  • Carbon dioxide capture and storage (hereinafter simply referred to as "CCS") is attracting attention as an innovative technology that can suppress carbon dioxide (CO 2 ) emissions while generating electricity using fossil fuels. . Furthermore, with regard to methods of storing carbon dioxide underground using CCS technology, verification tests and surveys of suitable storage sites are being actively carried out.
  • carbon dioxide exists in one of four phases: gas, liquid, solid, and supercritical, depending on pressure and temperature conditions. Also, carbon dioxide becomes solid dry ice under conditions of normal pressure and temperature below 194K (-79.15°C), but when mixed with water, it becomes hydrate (solid) under different temperature and pressure conditions. It is known to do. Note that carbon dioxide hydrate is produced by mixing liquid carbon dioxide with water at a temperature of 10°C or lower and a pressure of 4.5 MPa or higher. overlaps with a part of the phase region).
  • Carbon dioxide hydrate as described above is a solid having a crystal structure similar to that of methane hydrate, and has a structure in which gas molecules are trapped within a steric lattice made up of water molecules.
  • Such carbon dioxide hydrate is also generally called gas hydrate, and the following non-patent document 1 describes the first research report that carbon dioxide becomes hydrated and causes clogging in natural gas transfer lines. Confirmed. Furthermore, carbon dioxide hydrate has been confirmed as a clogging substance in plant piping for oil and gas processing, and research is progressing in the scientific field related to the earth and planets.
  • Non-Patent Document 2 reports that in 1990, natural carbon dioxide hydrate was discovered rising up from the sea floor in a columnar shape.
  • the density of carbon dioxide changes due to a gas-liquid phase change when the pressure increases, but since it becomes supercritical at a temperature of 31°C or higher and a pressure of 7.4 MPa or higher, the density change due to a further pressure increase is comparatively It's slow. Since the density of carbon dioxide in a liquid or supercritical state is lower than that of seawater, for example, when trying to store carbon dioxide in a geological layer beneath the ocean floor, buoyancy occurs due to the density difference, causing carbon dioxide to float to the surface. Some kind of sealing function is required to contain it.
  • aquifer storage (DSA; Deep Saline Aquifer) has been under consideration since the 1990s under the initiative of the government and administrative agencies.
  • Commercial storage locations and storage capacity have not yet been determined. This is because Japan's lack of oil and natural gas production suggests that Japan's geological formations contain natural caprock (shielding layers such as mudstone) that are commonly found in the Middle East, Europe, America, Asia, etc. (Caprock)) is thought to be a contributing factor.
  • the hydrated carbon dioxide shielding layer as described above has the advantage of not requiring a cap rock such as mudstone.
  • the underground storage target layer for carbon dioxide hydrate storage is, for example, a Quaternary sedimentary layer (geological age is (approximately 2.58 million years ago), and is widely distributed in the seas surrounding Japan.
  • methane gas exists deep underground.
  • this methane gas is not trapped in the cap rocks mentioned above, but is trapped as methane hydrate in the shallow strata several hundred meters below the seafloor, so it is present in large quantities in the seas surrounding Japan. It can be considered that
  • Non-Patent Document 4 The basic concept of carbon dioxide hydrate storage as described above is shown in, for example, the following non-patent documents 3 and 4, but the reality is that research on the specific mechanism has not progressed. On the other hand, in the United Kingdom (Scotland), research results from laboratory experiments have been reported as a government-led project, as shown in Non-Patent Document 4 below.
  • Patent Document 1 proposes a method that achieves both carbon dioxide fixation and methane gas production without relying on a methane hydrate layer.
  • Patent Document 1 describes a step of forming a methane gas production layer 4 by adding a group of microorganisms containing at least methane-producing bacteria to the interstices of the stratum under temperature and pressure conditions where the methane-producing bacteria produce methane gas; Carbon dioxide hydrate is produced by injecting an emulsion in which fine particles of liquid carbon dioxide smaller than the gaps are dispersed in water into the gaps in the strata that are shallower than the layers and under temperature and pressure conditions where carbon dioxide becomes hydrate.
  • a method includes a step of recovering the material.
  • Patent Document 1 discloses that a carbon dioxide shielding layer that exists from the ocean floor to a predetermined depth and that satisfies the pressure and temperature conditions that are capable of producing carbon dioxide hydrate. Methods and devices for forming a carbon dioxide reservoir by injecting carbon dioxide have been proposed. According to the technology described in Patent Document 2, clogging when storing carbon dioxide underground can be prevented, and a large amount of carbon dioxide can be efficiently stored.
  • the present invention was made in view of the above circumstances, and by ensuring the strength of the carbon dioxide shielding layer made of carbon dioxide hydrate, carbon dioxide injected downward can be reliably contained, and a large amount of carbon dioxide can be contained.
  • the purpose of the present invention is to provide an underground carbon storage method that can efficiently store carbon dioxide.
  • a method of storing carbon dioxide alone or in a liquefied state as a mixed gas mainly composed of carbon dioxide in a sub-seafloor stratum made of sediment on an acoustic substrate or in a stratum on land comprising: A carbon dioxide reservoir is created by injecting the carbon dioxide below the carbon dioxide seal area, which exists from the seabed or ground to a predetermined depth and consists of a stratum that satisfies the pressure and temperature conditions capable of producing carbon dioxide hydrate.
  • a carbon dioxide shielding layer is formed in the carbon dioxide sealing region, and the strength of the carbon dioxide shielding layer at the initial stage of carbon dioxide hydrate generation is equal to the thickness of the carbon dioxide liquid layer formed above the carbon dioxide storage layer.
  • a method for storing carbon dioxide underground which corresponds to the pressure acting on the carbon dioxide shielding layer when the distance is from 10 m to 40 m.
  • the carbon dioxide shielding layer has a strength of 0.01 to 0.04 MPa in the pores of the carbon dioxide shielding layer at the initial stage of generation of the carbon dioxide hydrate, the carbon dioxide according to [1] above.
  • the strength of the carbon dioxide shielding layer formed by hydrated carbon dioxide can be ensured. This allows the carbon dioxide injected below the carbon dioxide shielding layer to be reliably contained, making it possible to efficiently store a large amount of carbon dioxide.
  • FIGS. 1(a) and 1(b) are diagrams illustrating a carbon dioxide underground storage method according to an embodiment of the present invention, and the schematic structure when carbon dioxide is stored in a geological layer under the seabed.
  • FIG. 1(a) is an image diagram showing each stratum in a wide area
  • FIG. 1(b) is an enlarged view of the main part in FIG. 1(a).
  • FIG. 2 is a diagram illustrating an underground storage method for carbon dioxide, which is an embodiment of the present invention, and shows isolines of carbon dioxide density in the temperature-pressure relationship and stable regions of carbon dioxide hydrate. This is a graph showing.
  • FIG. 1(a) is an image diagram showing each stratum in a wide area
  • FIG. 1(b) is an enlarged view of the main part in FIG. 1(a).
  • FIG. 2 is a diagram illustrating an underground storage method for carbon dioxide, which is an embodiment of the present invention, and shows isolines of carbon dioxide density in the temperature-pressure relationship and stable regions of carbon dioxide hydrate.
  • FIG. 3 is a diagram illustrating a carbon dioxide underground storage method according to an embodiment of the present invention, and is a graph showing a temperature-pressure phase diagram of carbon dioxide hydrate.
  • FIG. 4 is a diagram illustrating an underground storage method for carbon dioxide, which is an embodiment of the present invention. It is a graph showing pressure.
  • FIG. 5 is a diagram illustrating a carbon dioxide underground storage method that is an embodiment of the present invention, and is a schematic diagram showing the schematic structure of a pressure cell used in an indoor experiment to demonstrate the present invention. be.
  • FIGS. 6(a) to 6(c) are diagrams illustrating an underground storage method for carbon dioxide, which is an embodiment of the present invention. 2 is a graph showing the strength of a film made of carbon dioxide hydrate.
  • FIG. 7 is a diagram illustrating an underground storage method for carbon dioxide, which is an embodiment of the present invention. It is a graph showing the temperature rise due to the heat of formation of carbon dioxide hydrate when it permeates.
  • FIG. 8 is a diagram illustrating a carbon dioxide underground storage method that is an embodiment of the present invention, and the differential pressure obtained in an experiment using the pressure cell shown in FIG. It is a graph showing the relationship between holding time and differential pressure when holding for 17 days under the condition that the pressure is 2 m or less.
  • FIG. 9 is a diagram illustrating a carbon dioxide underground storage method that is an embodiment of the present invention, and the differential pressure obtained in an experiment using the pressure cell shown in FIG.
  • FIG. 10 is a diagram illustrating a carbon dioxide underground storage method according to an embodiment of the present invention, in which the differential pressure obtained in an experiment using the pressure cell shown in FIG. It is a graph showing the strength of a carbon dioxide shielding layer made of a film of carbon dioxide hydrate as the strength increases.
  • FIG. 11 is a diagram illustrating a carbon dioxide underground storage method that is an embodiment of the present invention, and shows the differential pressure in the opposite direction obtained in an experiment using the pressure cell shown in FIG.
  • FIG. 2 is a graph showing the strength of a carbon dioxide shielding layer made of a carbon dioxide hydrate film when activated.
  • FIG. 12 is a diagram illustrating a carbon dioxide underground storage method, which is an embodiment of the present invention, and shows isolines of the optimal volume ratio of ⁇ carbon dioxide/water ⁇ in the temperature-pressure relationship. This is a graph showing.
  • FIG. 13 is a diagram illustrating an underground storage method for carbon dioxide, which is an embodiment of the present invention. Based on the experimental results using the pressure cell shown in FIG. It is a diagram considering the shielding mechanism.
  • FIG. 12 is a diagram illustrating a carbon dioxide underground storage method, which is an embodiment of the present invention, and shows isolines of the optimal volume ratio of ⁇ carbon dioxide/water ⁇ in the temperature-pressure relationship. This is a graph showing.
  • FIG. 13 is a diagram illustrating an underground storage method for carbon dioxide, which is an embodiment of the present invention. Based on the experimental results using the pressure cell shown in FIG. It is a diagram considering the shielding mechanism
  • FIG. 14 is a diagram illustrating an underground storage method for carbon dioxide, which is an embodiment of the present invention, and shows the temperature conditions at a depth where the density of carbon dioxide and the density of seawater are in equilibrium in the geological layer below the seabed. It is a graph showing the relationship with pressure conditions.
  • FIG. 15 is a diagram illustrating a carbon dioxide underground storage method that is an embodiment of the present invention, and is a diagram schematically showing a storage method assuming an island, a seamount, and a sea plateau. It is a graph showing the relationship between water depth and water depth.
  • FIGS. 1(a) and 1(b) are diagrams illustrating a carbon dioxide underground storage method (hereinafter sometimes simply referred to as "storage method"), which is an embodiment of the present invention.
  • This is a schematic cross-sectional view showing a schematic structure when carbon dioxide is stored in a stratum U below the ocean floor F.
  • FIG. 1(a) is a diagram showing a wide area of the stratum U including each stratum.
  • b) is an enlarged view of the main part in FIG. 1(a).
  • the storage method of this embodiment is to store carbon dioxide (CO 2 ) alone or in a liquefied state as a mixed gas mainly composed of carbon dioxide (CO 2 ) in a stratum U under the ocean floor F consisting of deposits on an acoustic substrate B or in a liquefied state.
  • This is a method of storing it in geological formations on land (not shown). That is, in the storage method of the present embodiment, carbon dioxide hydrate is extracted from a geological formation that exists at a predetermined depth from the ground of the ocean floor (seafloor surface) F or a land area (not shown) that satisfies the pressure and temperature conditions capable of producing carbon dioxide hydrate.
  • a carbon dioxide storage layer G is formed by injecting carbon dioxide under pressure below the carbon dioxide sealing region S.
  • at least a portion of the carbon dioxide injected into the carbon dioxide storage layer G is naturally raised toward the carbon dioxide sealing region S side by the buoyancy of carbon dioxide to generate carbon dioxide hydrate.
  • a carbon dioxide shielding layer C is formed in the carbon dioxide sealing region S.
  • the method for underground storage of carbon dioxide is a method in which the storage location is either the stratum U below the ocean floor F or the stratum under the ground in the land area.
  • the storage location is either the stratum U below the ocean floor F or the stratum under the ground in the land area.
  • a case where carbon dioxide is stored in a stratum U below the seafloor surface F will be described as an example.
  • predetermined pressure conditions and temperature conditions are satisfied, it is also possible to use a geological formation under the ground in a land area as a storage location.
  • the carbon dioxide described in this embodiment includes not only pure carbon dioxide (CO 2 ) alone but also a mixture containing carbon dioxide as a main component as described above. That is, the carbon dioxide to be stored in this embodiment may contain water by using existing countermeasure techniques. Furthermore, in addition to carbon dioxide itself, the carbon dioxide to be stored in this embodiment includes other components other than carbon dioxide, such as carbon monoxide (CO), hydrogen (H 2 ), methane (CH 4 ), It also includes water (H 2 O), hydrogen sulfide (H 2 S), and the like.
  • CO carbon monoxide
  • H 2 hydrogen
  • H 2 S hydrogen sulfide
  • FIG. 1(a) shows an underground carbon dioxide storage device (hereinafter sometimes simply referred to as “storage device”) 1 of the present embodiment (enlarged main part of FIG. 1(b)). (see also figure).
  • the illustrated storage device 1 injects and stores carbon dioxide alone or in a liquefied state as a mixed gas containing carbon dioxide as a main component into a geological layer U below a seafloor surface F consisting of sediments on an acoustic substrate B. It is something.
  • the storage device 1 penetrates a carbon dioxide sealing region S, which is made of a stratum that exists from the seabed surface F to a predetermined depth and satisfies pressure and temperature conditions that are capable of producing carbon dioxide hydrate.
  • An injection well 2 extending to a carbon dioxide storage layer G below, a carbon dioxide supply source loaded on a ship (not shown), etc. above the sea surface M, and a carbon dioxide supply source loaded on a ship, etc., similar to the carbon dioxide supply source. It is generally configured to include a pumping facility (not shown) that pumps the carbon dioxide loaded and produced by the carbon dioxide supply source to the injection well 2 .
  • the storage device 1 is provided with a supply line (not shown) for supplying carbon dioxide from a pressure feeding facility installed on a ship to an injection well 2 provided starting from the seabed surface F. Furthermore, in the storage device 1 shown in FIGS. 1(a) and 1(b), when carbon dioxide is injected into the stratum U below the seabed surface F, at least one of seawater and water is used as pore water to seal the carbon dioxide. An artificial water sealing facility 6 is provided for increasing the pore pressure of the carbon dioxide sealing region S by artificial water sealing injected into the region S.
  • the stratum U below the seafloor F located below the seawater W is usually at the depth from the sea surface M to the seafloor F, and at any distance from the seafloor F to the stratum U.
  • the pressure changes depending on the depth.
  • the illustrated storage device 1 is located in a carbon dioxide storage layer G below a carbon dioxide sealing area S that exists from a seabed surface F to a predetermined depth and satisfies pressure and temperature conditions capable of generating carbon dioxide hydrate. Carbon dioxide is injected and stored.
  • the carbon dioxide supply source (not shown) supplies carbon dioxide stored in the carbon dioxide storage layer G in the geological layer U, as described above.
  • sources of carbon dioxide are not particularly limited, and include, for example, carbon dioxide derived from coal, oil, etc. discharged from power generation equipment that uses fossil fuels at various facilities such as offshore plants that extract oil and gas. Examples include devices that capture carbon dioxide, and devices that temporarily receive and store the carbon dioxide recovered by these devices from ships and pipelines that transport it.
  • the carbon dioxide supply source (not shown) is exposed above the sea level M, depending on the characteristics of the device, but it is recommended that the supply of materials such as fuel and carbon dioxide is improved. This is preferable from the viewpoint of maintainability, device life, etc.
  • an example of a configuration in which the carbon dioxide supply source is exposed above sea level M is to construct an offshore platform similar to those installed to extract resources such as oil and gas from the seabed. Examples include those with a carbon dioxide supply source installed on top.
  • Examples of the above-mentioned marine platforms include fixed types and floating types.
  • Examples of fixed marine platforms include those constructed by directly fixing structures assembled from high-strength steel materials to the seabed surface F, and the like.
  • examples of the floating marine platform include those consisting of semi-submersible vessels and the like.
  • the carbon dioxide supply source is not limited to one installed on an offshore platform such as a ship.
  • a configuration may be adopted in which carbon dioxide generated by a carbon dioxide supply source installed on land is transported to the injection well 2 via pressure feeding equipment and piping (pipeline).
  • the pumping equipment pumps carbon dioxide (CO 2 ) into the injection well 2, and as described above, is installed on an offshore platform such as a ship, for example.
  • the storage device 1 is configured such that carbon dioxide is supplied from pressure feeding equipment installed on a ship to an injection well 2 provided starting from the seabed surface F via a supply line (not shown). I can do it.
  • any pump or the like for pressure-feeding liquid that has been conventionally used in this field can be employed without any limitations.
  • a piping member made of a metal or resin material that can be used in seawater can be used without any restriction.
  • the pressure feeding equipment is not limited to those installed on a marine platform such as a ship as described above, and it is also possible to install the pressure feeding equipment on land or on the seabed surface F, for example.
  • the injection well 2 penetrates the carbon dioxide seal region S that exists from the seabed surface F to a predetermined depth, and extends to the carbon dioxide reservoir G below the carbon dioxide seal region S, and Carbon dioxide is injected into the carbon reservoir G.
  • the injection well 2 is, for example, a carbon dioxide injection/injection hole made of a well drilled by boring or the like.
  • the injection well 2 in the illustrated example is provided as a vertical well, but if necessary, it may be an inclined well, or a combination of a vertical well and a horizontal well (for example, an L-shaped cross section), a vertical well, It is also possible to have a structure that combines horizontal wells and inclined wells as appropriate. Moreover, it is also possible to install it as an inclined well directly from land, and in this case, the carbon dioxide supply source and pumping equipment (not shown) will be installed on land.
  • the storage device 1 of the illustrated example is provided with the artificial water sealing equipment 6 for increasing the pore pressure of the carbon dioxide sealing region S, and in the illustrated example, the artificial water sealing equipment 6 It is arranged so that a portion is exposed on the upper surface of the seal area S.
  • the artificial water sealing equipment 6 is comprised of multiple pipes provided in an annular shape so as to surround the injection well 2, as shown in the enlarged view of FIG. 1(b).
  • the artificial water sealing equipment 6 is composed of multiple pipes having a step-shaped cross section extending outward from the injection well 2 side.
  • the artificial water sealing equipment 6 injects carbon dioxide into the stratum U below the seafloor surface F, it injects at least one of seawater and water as pore water into the carbon dioxide sealing region S. As a result, the pore pressure of the carbon dioxide sealing region S increases, so that the strength of the entire carbon dioxide sealing region S including the carbon dioxide shielding layer C can be increased.
  • the storage device 1 used in this embodiment also has a carbon dioxide shielding layer C in which the state of carbon dioxide stored in the carbon dioxide storage layer G or carbon dioxide hydrate is generated.
  • Various monitoring devices may be provided for detecting the state of the carbon dioxide seal area S including the carbon dioxide sealing area S.
  • carbon dioxide (CO 2 ) alone or a mixed gas containing carbon dioxide as a main component is liquefied, and carbon dioxide (CO 2 ) is stored on the seafloor surface F made of sediments on the acoustic substrate B.
  • This is a method of storing it in the underlying stratum U or in a stratum on land (not shown).
  • a carbon dioxide seal area S exists at a predetermined depth from the ground of the seabed (seafloor surface) F or a land area (not shown), and is composed of a stratum that satisfies pressure and temperature conditions capable of producing carbon dioxide hydrate.
  • Carbon dioxide is injected under pressure to form a carbon dioxide storage layer G.
  • at least a portion of the carbon dioxide injected into the carbon dioxide storage layer G is naturally raised toward the carbon dioxide sealing area S by the buoyancy of the carbon dioxide to generate carbon dioxide hydrate.
  • a carbon dioxide shielding layer C is formed therein.
  • the strength of the carbon dioxide shielding layer C at the initial stage of carbon dioxide hydrate generation is 10 m or more when the thickness of the carbon dioxide liquid layer G1 formed on the upper part of the carbon dioxide storage layer G is 10 m or more. It is configured to correspond to the pressure acting on the carbon dioxide shielding layer C when the distance is 40 m.
  • the strength of the carbon dioxide shielding layer C made of carbon dioxide hydrate which will be explained in this embodiment, is the so-called threshold pressure, which is the pressure at which carbon dioxide starts permeating. That is, the strength of the carbon dioxide shielding layer C needs to be at least a threshold pressure below which carbon dioxide does not permeate (is shielded).
  • the threshold pressure explained in this embodiment is based on the "sub-seafloor disposal of specified carbon dioxide gas" in the DSA demonstration test based on the "Act on the Prevention of Marine Pollution, Etc. and Maritime Disasters" (Act No. 136 of 1971).
  • mercury intrusion is applied as the pressure at which carbon dioxide CO 2 starts permeating into the carbon dioxide shielding layer C. Measured by law etc. It should be noted that the carbon dioxide shielding layer C is thought to be formed mainly by carbon dioxide hydrate filling the pores of the strata, and the shielding mechanism is thought to be different from the threshold pressure in DSA described above, which is caused by capillary pressure. It will be done.
  • carbon dioxide (CO 2 ) exists in one of four phases: gas, liquid, solid, and supercritical within a predetermined temperature and pressure range. Also, carbon dioxide (CO 2 ) becomes solid (dry ice) under normal pressure and at temperatures below 194K (-79.15°C), but when mixed with water, it becomes solid (dry ice) under different temperature and pressure conditions. Turn into hydrate (solid).
  • carbon dioxide (CO 2 ) becomes supercritical when the temperature is 31° C. or higher and the pressure is 7.4 MPa or higher, and the density change becomes relatively slow.
  • Carbon dioxide (CO 2 ) has a density lower than that of seawater when the temperature is 35°C or lower and the pressure is 20MPa or lower, and it has a density lower than that of water unless the temperature is around 0°C and the pressure is 14MPa or higher. small. That is, in a liquid or supercritical state, carbon dioxide (CO 2 ) has a lower density than seawater, so carbon dioxide (CO 2 ) is deposited in the stratum U (see Figure 1) below the ocean floor F. In order to store carbon dioxide, a sealing function is required to contain the carbon dioxide that floats up due to the above density difference.
  • natural gas generally exists in geological formations in the form of conventional natural gas, shale gas, methane hydrate, or the like.
  • Conventional natural gas is stored in geological formations with highly airtight caprock such as mudstone that acts as a sealing layer.
  • Analysis of shale gas's DNA has revealed that it is produced from shale, which is considered to be the source rock of petroleum, at the same time as shale oil. It has been confirmed that methane hydrate exists as a solid in the sub-seafloor layer of the continental margins and in the permafrost layer, and although there is no cap rock like the one mentioned above, it is difficult to prevent methane hydrate from occurring due to the temperature and pressure conditions in which it becomes hydrated. , a sealing layer that performs a so-called sealing function is formed.
  • natural gas in its natural state can be viewed as a natural analogue (natural analogue phenomenon) of carbon dioxide storage. That is, in the underground storage (also called aquifer storage) of conventional natural gas and general carbon dioxide, the above-mentioned cap rock functions as a sealing layer. Furthermore, methane hydrate and carbon dioxide hydrate can be used as a sealing layer by setting the temperature and pressure conditions for hydration. Furthermore, shale gas exists when methane is adsorbed on shale or coal seams, and it is known that carbon dioxide is also adsorbed. As mentioned above, naturally occurring natural gas is confined within geological formations with different sealing functions. By utilizing such a sealing function, that is, natural conditions, it becomes possible to store carbon dioxide underground.
  • the inventor of the present invention has determined that, in forming the carbon dioxide shielding layer C by generating carbon dioxide hydrate as described above, the strength at the initial stage of carbon dioxide hydrate formation should be adjusted to It has been found that when the carbon dioxide liquid layer G1 formed on the upper part of G has a predetermined layer thickness, it is optimized so as to correspond to the pressure acting on the carbon dioxide shielding layer C. That is, the initial strength of carbon dioxide hydrate generation in the carbon dioxide shielding layer C is determined by determining the strength of the carbon dioxide shielding layer when the thickness of the carbon dioxide liquid layer G1 formed on the upper part of the carbon dioxide storage layer G is 10 m to 40 m. It has been found that by optimizing the carbon dioxide shielding layer C based on the pressure acting on the carbon dioxide shielding layer C, the carbon dioxide shielding layer C becomes a sealing layer with sufficient strength.
  • the carbon dioxide shielding layer C becomes a sealing layer with sufficient strength. It was discovered that this makes it possible to store large amounts of carbon dioxide more efficiently.
  • the present inventor has determined that the carbon dioxide shielding layer C can be formed with sufficient strength by optimizing the relationship between the time from the generation of carbon dioxide hydrate in the carbon dioxide shielding layer C and the strength. It was discovered that the carbon dioxide injected into the carbon dioxide reservoir G can be prevented from leaking, and a large amount of carbon dioxide can be efficiently stored without the need for a cap lock, and the present invention has been made. completed.
  • the strength at the initial stage of carbon dioxide hydrate production in the carbon dioxide shielding layer as defined in the present invention is, for example, the strength at a time of 0 to 40 hours from the start of carbon dioxide hydrate production.
  • the carbon dioxide seal area S below the seafloor surface F is a stratum that satisfies the pressure and temperature conditions that allow carbon dioxide hydrate to be produced, that is, the carbon dioxide hydrate is stable. This is the area where the pressure and temperature exist.
  • the carbon dioxide storage layer G located below the carbon dioxide sealing area S is an area with pressure and temperature conditions that allow carbon dioxide to be stored as a liquid (the temperature-pressure phase diagram of carbon dioxide hydrate in Figure 3 is also reference).
  • the acoustic base B under the carbon dioxide reservoir G is a base defined by the reflection method used to interpret submarine geological maps, etc., and for example, the existence of basalt, etc., which has a composition similar to that of magma is thought to exist. It is the foundation.
  • the carbon dioxide density contour line used for the trial calculation of the pressure acting on the carbon dioxide shielding layer C is shown in the graph of the temperature-pressure phase diagram of carbon dioxide hydrate in FIG. 2.
  • the region indicated by R1 in the graph of FIG. 2 is a region indicating pressure and temperature conditions under which carbon dioxide hydrate exists stably.
  • FIG. 3 shows a curve plotting the relationship between seawater temperature and pressure (water depth) in the Pacific Ocean and the Sea of Japan.
  • Figure 3 also shows the Span & Wagner equation of state (Reference 1: Span, R. and Wagner, W.
  • FIG. 3 also shows isovalue lines of the density difference ⁇ (carbon dioxide density ⁇ seawater density). Furthermore, in FIG. 3, the temperature and pressure of the stratum shown in the schematic cross-sectional view of FIG. ) ⁇ is also shown.
  • the region indicated by R2 in the graph of FIG. 3 is the carbon dioxide shielding layer when the thickness of the carbon dioxide liquid layer G1 formed above the carbon dioxide storage layer G is 10 m to 40 m. This is the area where the pressure acting on C can be read.
  • a region R2 shown in FIG. 3 is a region indicating the pressure and temperature of carbon dioxide stored in the carbon dioxide storage layer G.
  • the density of carbon dioxide is 850 to 970 kg/ m3
  • the density of seawater is is 1029 to 1035 kg/m 3 .
  • the region indicated by R3 in the graph of FIG. 3 indicates the range of the density of carbon dioxide stored by carbon dioxide hydrate storage (when the thickness of the carbon dioxide liquid layer G1 is 50 m). Looking at this region R3, the density of the stored carbon dioxide is about 900 to 950 kg/m 3 , which is equivalent to 90 to 95% of the density of seawater. This shows that when the density of carbon dioxide stored in the carbon dioxide storage layer G (carbon dioxide liquid layer G1) approaches the density of seawater, the pressure generated by the buoyancy acting on the carbon dioxide shielding layer C becomes smaller.
  • Line segments (a) - (b) - (c) shown in the graph of Fig. 3 represent the temperature and pressure at the bottom of the ocean floor F (a) and the temperature and pressure at the lower end of the carbon dioxide shielding layer C (b), respectively.
  • the case where the geothermal gradient is 30°C/km and the temperature at the carbon dioxide injection point is 15°C is shown. Since this temperature and pressure change depending on the water depth and geothermal gradient at the storage point, the line segment (a)-(b)-(c) differs from point to point.
  • GG geothermal gradient
  • the pressure (T, P) can be calculated using the following general formula (1) using Tsf, Psf, and GG as known inputs.
  • the above-mentioned supercooling is a phenomenon in which the liquid remains in the liquid state even at a temperature and pressure that would cause the phase to change to a solid. , is known as a phenomenon in which the whole turns into a solid at once.
  • freezing point depression is known as the fact that when ice is floated in salt water with a concentration of about 3%, the melting point of this ice drops to about -5°C, and as the concentration of salt increases, the melting point drops even further. is also known.
  • the range is within a certain width.
  • the freezing point depression is 2°C on average, and the range is about ⁇ 2°C.
  • this freezing point depression is shown by a plurality of line segments L3 to L8 parallel to the temperature axis (X axis).
  • the temperature at the upper end of the carbon dioxide shielding layer C is 2° C. lower on average than the temperature at the lower end, and has a width of approximately ⁇ 2° C. Furthermore, when the geothermal gradient is 30°C/km, a temperature change of 2°C is equivalent to a layer thickness of 66.7 m, which has a width of ⁇ 66.7 m, but this layer thickness and ⁇ range are close to the average value. There is a high probability that Therefore, it is considered that the carbon dioxide shielding layer C is formed on the lower end side of the carbon dioxide sealing area S, that is, between 0 and 133 m from the boundary with the carbon dioxide storage layer G. Note that this finding is based on a geothermal gradient of 30° C./km and a salinity of 35 ⁇ , so if these change, the above-mentioned layer thickness will also change.
  • the right end of the line segment for Case 1-3 shows the water depth (m) when the reservoir thickness is 0 m (top of the storage tank), and the pressure value when the reservoir thickness is 200 m. is shown as positive downward.
  • the pressure when the reservoir layer thickness is 20 m is about 1/10 of the pressure when the reservoir layer thickness is 200 m.
  • Cases 1 and 2 are carbon dioxide hydrate storage
  • Case 3 is aquifer storage. In aquifer storage, carbon dioxide becomes supercritical, the carbon dioxide density is small, and the buoyancy is large. It can be seen that the pressure increases.
  • FIG. 5 shows a schematic structure of a pressure cell 100 used in an indoor experiment to demonstrate the present invention.
  • the maximum pressure within this pressure cell 100 is 70 MPa, which corresponds to the pressure at a depth of 7000 m underwater.
  • No. 7 silica sand (fine sand) or No. 9 silica sand (silt) was set in the pressure cell 100 shown in Figure 5 to reproduce conditions that simulated the pressure and temperature in the strata beneath the ocean floor.
  • an experiment was conducted in which liquid carbon dioxide was permeated from the bottom of the pressure cell 100.
  • the measurement items at this time are the temperature measured by thermometers installed at a pitch of 100 mm from the bottom side, and the pressure at the upper and lower ends of the pressure cell 100.
  • each of the graphs in FIGS. 6(a) to (c) shows the strength of a film made of carbon dioxide hydrate obtained in an experiment using the pressure cell 100 shown in FIG. 5.
  • the flow rate of carbon dioxide indicated by a solid line in the lower graph is 0.006 mL/min in FIG. 6(a), 0.006 mL/min in FIG. 6(b):
  • the time interval at which the carbon dioxide hydrate film breaks is set to become longer. If this time interval is short, it can be considered that the carbon dioxide hydrate film is broken before it gains sufficient strength.
  • the above differential pressure is the pressure acting on the carbon dioxide hydrate membrane.
  • this pressure difference becomes higher than the strength of the carbon dioxide hydrate membrane, part of the membrane ruptures and carbon dioxide permeates, reducing the pressure difference to 0. After that, the permeation of carbon dioxide stops. , a carbon dioxide hydrate film is repeatedly produced.
  • the graph in FIG. 7 shows the temperature rise due to the heat of formation of carbon dioxide hydrate when carbon dioxide permeates into the geological formation, which was obtained in an experiment using the pressure cell 100 shown in FIG. In this experiment, the position of the penetration tip of liquid carbon dioxide into a sample (No. 7 silica sand) saturated with seawater was confirmed by temperature changes.
  • the graph in FIG. 8 shows the relationship between the holding time and the differential pressure when the differential pressure was held for 17 days under the condition that the pressure cell 100 shown in FIG. It shows a relationship. Furthermore, in this experiment, a sample (No. 9 silica sand) saturated with 40 ⁇ seawater was used. The initial conditions for the experiment whose results are shown in the graph of FIG. 8 were that carbon dioxide was infiltrated into the pores of the sand saturated with seawater to the position of the thermometer installed 400 to 500 mm from below. In Figure 8, the relationship between time and differential pressure shown by the solid line in the third graph from the top (third graph from the bottom) is the initial carbon dioxide hydride, which is assumed to be generated at the tip position where carbon dioxide has permeated. Regarding the rate membrane, the differential pressure was maintained at 0.02 MPa for 400 hours (about 17 days).
  • the graph in FIG. 9 shows the result obtained in an experiment using the pressure cell 100 shown in FIG. 5, which was maintained for 17 days under the condition that the differential pressure was approximately 2 m or less in water head, and then maintained for 24 hours at a differential pressure of 1 MPa. It shows the strength of the carbon dioxide shielding layer C made of a carbon dioxide hydrate film when
  • the differential pressure of 0.02 MPa mentioned above is the differential pressure that occurs when carbon dioxide is stored in carbon dioxide hydrate storage so that the thickness of the carbon dioxide storage layer G is about 20 m.
  • the thickness of the carbon dioxide reservoir G will gradually increase. It will be done.
  • the time required for the carbon dioxide storage layer G to reach a thickness of 0 to 20 m is two weeks or more, the amount of storage can be achieved using the effective shielding function of the carbon dioxide shielding layer C with a strength of 1 MPa or more. can be expected.
  • the graph in FIG. 10 shows the strength of the carbon dioxide shielding layer made of a carbon dioxide hydrate film when the differential pressure is increased stepwise, which was obtained in an experiment using the pressure cell 100 shown in FIG. It shows.
  • the strength shown in the graph of FIG. 10 is the strength of the carbon dioxide hydrate membrane (pressure at which permeation of carbon dioxide starts).
  • the data shown in FIG. 10 is the result after data on the carbon dioxide shielding layer C having a strength of 1 MPa or more was acquired three times in a row over a period of about two weeks.
  • the reason for conducting this experiment was that based on previous knowledge, it was predicted that the strength of the carbon dioxide shielding layer C would gradually increase over a period of about two weeks, and it was necessary to confirm this. What happened will be mentioned.
  • this experiment first, as an initial condition, sand saturated with seawater was maintained at a temperature of about 4° C. under water pressure (8 MPa) equivalent to a depth of 800 m. Then, various treatments were performed and progress observations were made at each of the timings shown in (1) to (6) below.
  • a graph with a pressure scale of 0 to 3 MPa is shown in the third graph from the top in Figure 10, and a graph with a pressure scale of 0 to 0.25 MPa is shown in Figure 10.
  • FIG. 11 is a graph showing the strength of the carbon dioxide shielding layer C made of a carbon dioxide hydrate film when a pressure difference in the opposite direction is applied, obtained in an experiment using the pressure cell 100 shown in FIG. It is.
  • the "reverse pressure differential" means that the relationship between the density of carbon dioxide ( ⁇ CO2 ) and the density of pore water ( ⁇ sw ), which will be described in detail later, is expressed by the following formula: ⁇ CO2 ⁇ sw ⁇ This refers to the case where the relationship is expressed as
  • the graph in FIG. 11 shows the results when the pressure of carbon dioxide was suddenly reduced after 15 hours. Due to this rapid decrease in the pressure of carbon dioxide, a remarkable temperature rise due to the heat of formation of carbon dioxide hydrate was observed at a location 400 mm from the bottom of the pressure cell 100, which indicates that a carbon dioxide shielding layer C was formed at this location. Conceivable. Moreover, this timing coincides with the timing when the pressure of carbon dioxide decreases from 20 MPa to about 17.5 MPa and then rises again to 20 MPa.
  • the carbon dioxide shielding layer C has sufficient strength and is not torn, so a pressure difference is generated.
  • the carbon dioxide shielding layer C was once broken.
  • water starts permeating into the vicinity of the carbon dioxide shielding layer C, and this permeation increases the pressure on the carbon dioxide side to 20 MPa.
  • a carbon dioxide shield made of a stronger carbon dioxide hydrate film is installed at this position. It is thought that layer C has been regenerated.
  • the graph in FIG. 12 shows contour lines of the optimal volume ratio of ⁇ carbon dioxide/water ⁇ in the temperature-pressure relationship.
  • the volume of water is required to be 2.3 times the volume of carbon dioxide. becomes. Therefore, in order for the pores into which carbon dioxide has permeated to become clogged, it is considered that a configuration in which there is insufficient water/seawater is likely to occur. In other words, it is considered that water has been used up (dry up) and carbon dioxide is in surplus.
  • FIG. 13 shows a schematic diagram in which the shielding mechanism of carbon dioxide hydrate by a film is considered based on the experimental results using the pressure cell 100 shown in FIG. That is, FIG. 13 is a diagram showing a partial cross section of the cylindrical pressure cell 100 shown in FIG. 5. As shown in FIG. As shown in the schematic diagram of Figure 13, near the interface between liquid carbon dioxide and water/seawater in the sand pores, the saturation level of water gradually decreases from 100%, indicating that the interface is never flat. . Further, as shown in FIG. 13, near the tip of carbon dioxide permeation, there is a region close to the volume ratio according to the above-mentioned molecular formula.
  • the carbon dioxide shielding layer C is not a horizontal one-sided film but a region having a thickness of a certain value or more.
  • the thickness is about 20 ⁇ m in the pores of the sand (Reference 5: Takehiko Yauchi, Yutaka Abe, Akiko Kaneko, Kenji Yamane, "Effect of flow field on CO 2 hydrate film thickness", Transactions of the Japan Society of Mechanical Engineers, B ed. , Vol. 78, No. 787, 2012) is generated in the shape of a straw, and further assumes that the average pore diameter is 60 ⁇ m, the 20 ⁇ m remaining in the center of the straw shape It is thought that liquid carbon dioxide exists in the region of . It takes about two weeks for the portion where this liquid carbon dioxide remains to turn into carbon dioxide hydrate, and it is thought that this portion will have a strength of 1 MPa or more. It is thought that carbon dioxide molecules and water molecules are supplied to the remaining portion of the liquid carbon dioxide by diffusion based on the concentration gradient, and this supply by diffusion takes time for the formation of the carbon dioxide shielding layer C. This is considered to be a factor.
  • the carbon dioxide shielding layer C has a strength of 0.01 to 0.04 MPa in the pores of the carbon dioxide shielding layer C at the initial stage of carbon dioxide hydrate generation. More preferably, the average value is about 0.02 MPa.
  • the strength of 0.02 MPa at the initial stage of carbon dioxide hydrate formation is an average value for the particle sizes of the above-mentioned No. 9 silica sand to No. 7 silica sand.
  • the initial strength of carbon dioxide hydrate generation in the carbon dioxide shielding layer C and the layer thickness of the carbon dioxide liquid layer G1 formed on the upper part of the carbon dioxide storage layer G are 10 m. ⁇ 40m, calculate the pressure acting on the carbon dioxide shielding layer C, and based on each calculated value, calculate the injection flow rate of carbon dioxide into the stratum U below the seafloor surface F, the number of injection wells 2 used, and , the implantation depth can be controlled.
  • Each of the above calculations can be performed using a calculation program on a computer, tablet terminal, etc., and based on the calculation results, the injection flow rate of carbon dioxide, the number of injection wells 2 used, and the depth. All you have to do is control. In this case, for example, by installing a plurality of injection wells 2 with different inner diameters and injection depths, it becomes easy to appropriately change the flow rate and the number of injection wells 2 used.
  • the carbon dioxide is Since the injection flow rate and injection position of carbon can be adjusted, efficient operation of the carbon dioxide storage facility becomes possible. Further, as described above, it becomes possible to reliably and effectively contain the carbon dioxide injected below the carbon dioxide shielding layer C, and therefore it becomes possible to store a large amount of carbon dioxide with high efficiency.
  • the carbon dioxide shielding layer C has a strength of 1 MPa or more after 10 to 20 days have passed from the start of carbon dioxide hydrate production.
  • the strength of the carbon dioxide shielding layer C can be ensured more reliably.
  • the carbon dioxide injected below the carbon dioxide shielding layer C can be more reliably contained, so that a large amount of carbon dioxide can be stored with higher efficiency.
  • the intensity of carbon dioxide hydrate in the carbon dioxide shielding layer C after 10 to 20 days have elapsed from the start of production of carbon dioxide hydrate is calculated, and based on the calculated value, carbon dioxide
  • a method of controlling at least any one of the injection flow rate of carbon into the stratum U below the seafloor surface F, the number of injection wells 2 used, and the injection depth can be adopted.
  • the above calculated value can be obtained using a calculation program on a computer, tablet terminal, etc., and similarly to the above, based on this calculation result, the injection flow rate of carbon dioxide, the number of injection wells 2 used, and the depth can be determined. It is possible to control.
  • the injection flow rate and injection position of carbon dioxide can be adjusted while monitoring the storage status of carbon dioxide in the carbon dioxide storage layer G and the strength of the carbon dioxide shielding layer C, etc. This will enable even more efficient operation of storage facilities. Further, as described above, it is possible to reliably and effectively contain the carbon dioxide injected below the carbon dioxide shielding layer C, and therefore it is possible to store a large amount of carbon dioxide with even higher efficiency.
  • the stratum thickness of the entire carbon dioxide seal area S is not particularly limited. However, in order to improve the sealing performance of the carbon dioxide seal area S, that is, to reliably prevent carbon dioxide (CO 2 ) stored in the carbon dioxide reservoir G from leaking into the seawater W, the carbon dioxide seal It is preferable to ensure that the stratum thickness of the region S is at least 100 m or more. In this way, the method of ensuring the desired thickness of the stratum in the carbon dioxide seal area S is, for example, by thoroughly understanding the temperature and pressure situation of the stratum U below the seafloor surface F through a preliminary survey. It is preferable to set the depth of the injection well 2 so that the stratum thickness of the carbon dioxide sealing region S has a predetermined dimension, and to optimize the injection depth of carbon dioxide (injection depth).
  • an artificial water seal equipment 6 such as that provided in the storage device 1 shown in FIGS. 1(a) and 1(b) can be mentioned.
  • the illustrated artificial water sealing equipment 6 is disposed on the upper surface side of the carbon dioxide sealing area S, and as described above, by injecting at least one of seawater and water as pore water into the carbon dioxide sealing area S, carbon dioxide is removed. It is possible to increase the pore pressure in the seal area S.
  • the pore pressure of the carbon dioxide sealing region S increases, so that the strength of the entire carbon dioxide sealing region S including the carbon dioxide shielding layer C is increased. Note that the detailed configuration of the artificial water seal equipment 6 is as already described.
  • Carbon dioxide hydrate storage targets the latest unconsolidated Quaternary sedimentary layer in geological time, as mentioned above.
  • the Quaternary sedimentary layers are unconsolidated, so deformation is allowed, and dilatancy (volume change caused by shear deformation) is thought to occur along with this deformation.
  • dilatancy volume change caused by shear deformation
  • the porosity of the Quaternary sedimentary layer increases due to the above-mentioned dilatancy, which increases the permeability, and it is necessary to consider how much of an impact this has on the risk of carbon dioxide leakage. For this reason, the present inventors conducted a demonstration experiment using the pressure cell 100 shown in FIG.
  • the density of carbon dioxide ( ⁇ CO2 ) and the density of pore water ( ⁇ sw ) in the stratum U below the ocean floor F are determined. After identifying a geological formation that satisfies the pressure and temperature conditions in which the carbon dioxide is in equilibrium, carbon dioxide can be stored in the depth region.
  • the depth of the stratum that satisfies the pressure and temperature conditions in which the density of carbon dioxide ⁇ CO2 and the density of pore water ⁇ sw are in equilibrium in the stratum U below the seafloor F or in the strata on land is determined. It is also possible to adopt a method of calculating and controlling the injection position of carbon dioxide into the stratum U under the ocean floor F or the strata on land based on the calculated value.
  • the graph in Figure 14 shows the calculation results of the relationship between temperature and pressure conditions at the depth where the density of carbon dioxide ( ⁇ CO2 ) and the density of seawater ( ⁇ sw ) are in equilibrium in the stratum U below the seafloor F. ing.
  • the calculation of the results shown in the graph of FIG. 14 was performed under the conditions of seawater salinity: 35 ⁇ psu and geothermal gradient: 30° C./km, and for the seawater temperature, an example of Argo data in the Pacific Ocean was used.
  • (1) is the generation (stable) region of carbon dioxide hydrate, where the density of carbon dioxide ( ⁇ CO2 ) and the density of seawater ( ⁇ sw ) are expressed by the following formula: ⁇ CO2 ⁇ sw ⁇ This is the region where the relationship is expressed as , and the temperature region deeper than this position is where carbon dioxide liquefies.
  • the conditions for applying the above calculation are such that the density of carbon dioxide ( ⁇ CO2 ) and the density of seawater ( ⁇ sw ) are expressed by the following formula ⁇ CO2 > ⁇ sw ⁇ in the relationship between seawater temperature and pressure (water depth) in the ocean area. This is the stratum U below the seafloor F at a depth of 2,700 m or deeper ( Pacific Ocean excluding the Sea of Japan), which has the relationship expressed by .
  • the hatched areas on the base points of the X and Y axes correspond to temperature conditions where the density of carbon dioxide ( ⁇ CO2 ) is greater than the density of seawater ( ⁇ sw ). Shows pressure conditions.
  • a method has also been proposed in which carbon dioxide is stored in areas of concave topography on the ocean floor by utilizing the environment where the relationship is expressed by the following equation ⁇ CO2 > ⁇ sw ⁇ (see reference 5 above). ), but in reality, this is not possible due to the ⁇ Act on the Prevention of Marine Pollution, Etc. and Maritime Disasters'' (Marine Pollution Prevention Act) based on international law.
  • the chain line in the graph of Figure 14 shows the density of seawater ( ⁇ sw ) calculated using the existing seawater equation of state, taking into account temperature (seawater/geological formation), pressure, and salinity of 35 ⁇ . .
  • the dashed-dotted line in the graph of FIG. 14 indicates the density of carbon dioxide ( ⁇ CO2 ) calculated using the existing equation of state for carbon dioxide and taking into account temperature (seawater/geological formation) and pressure.
  • the density of carbon dioxide ( ⁇ CO2 ) and the density of seawater ( ⁇ sw ) match (equilibrium) at around 2,700 m depth.
  • the density of carbon dioxide ( ⁇ CO2 ) is greater than the density of seawater ( ⁇ sw ).
  • the density of carbon dioxide ( ⁇ CO2 ) decreases as the temperature rises as it enters the stratum U below the ocean floor F, while at a depth of 4,000 m, the density of carbon dioxide ( ⁇ CO2 ) decreases again.
  • CO2 ) and the density of seawater ( ⁇ sw ) match.
  • the density of seawater ( ⁇ sw ) is greater than the density of carbon dioxide ( ⁇ CO2 ).
  • the seawater transitional zone, water depth 2500 in the stratum U below the seafloor F, the seawater transitional zone, water depth 2500, described in the 2005 IPCC report (15, p. 280, Fig. 6, 9/p. 286) is shown. ⁇ 3000m).
  • the temperature of the seabed surface F is generally less than 2°C. Furthermore, considering the geothermal gradient underground, it is possible to draw an isothermal line parallel to the F plane of the ocean floor.
  • the graph of FIG. 15 shows a storage method assuming an island, a seamount, and a sea plateau, and shows the relationship between horizontal distance and water depth with an aspect ratio of 1:10. In areas shallower than the above isopycnal lines, the relationship is expressed by the following equation ⁇ CO2 > ⁇ sw ⁇ , as shown in FIG. Since the area has the relationship expressed by do.
  • the depth of this isopycnal line can be determined by In order to store carbon dioxide nearby, it is necessary to drill a well below the ocean floor F to a depth of more than 3000 m. As described above, in order to drill a well below the seabed F at a depth of 3000 m or more, it is essential to use the latest drilling technology, and a significant increase in construction costs is expected. Therefore, as shown in Fig.
  • islands, seamounts, and sea platforms made of volcanic rock are the result of the shape of the airways of volcanic gas emitted from lava spewed out on the ocean floor surface F being rapidly cooled by seawater.
  • volcanic rocks such as Mt. Fuji have cavities (pores) that are continuous with lava paths (vents) and fine continuous pores (airtight for volcanic gas), and carbon dioxide is stored in these cavities. be done.
  • the term "island” mentioned above refers to a land area surrounded on all sides by water bodies such as oceans and lakes.
  • the above-mentioned “sea mount” is a type of submarine topography, and refers to a relatively isolated high place with a relative height of 1000 m or more above the sea floor, and whose peak diameter is not large. say.
  • the above-mentioned “sea plateau” is a plateau-like terrain with a relatively flat top on the ocean floor, which is 100 km2 or more in area, and is raised by 200 m or more from the surrounding sea floor.
  • "volcanic gas” is a mixed gas such as water vapor, CO 2 , hydrogen sulfide, and carbon monoxide.
  • the underground storage method for carbon dioxide of the present invention can reliably contain carbon dioxide injected downward by ensuring the strength of the carbon dioxide shielding layer formed by hydrated carbon dioxide. This is a method that allows for efficient storage of Therefore, the present invention is very suitable for use in various plants, for example, in which carbon dioxide is recovered while generating electricity using fossil fuels, and this carbon dioxide is stored underground to reduce emissions. .

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Abstract

L'invention concerne un procédé de stockage souterrain de dioxyde de carbone. La résistance d'une couche de blocage de dioxyde de carbone permet de garantir un confinement fiable lors de l'injection descendante de dioxyde de carbone, ce qui permet de stocker de manière efficace une grande quantité de dioxyde de carbone.
PCT/JP2023/023959 2022-08-25 2023-06-28 Procédé de stockage souterrain de dioxyde de carbone WO2024042850A1 (fr)

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