JP5748985B2 - Gas hydrate production promotion method and gas resource enhanced recovery method - Google Patents

Description

The present invention relates to a method for promoting the generation of gas hydrate and a method for enhancing recovery of gas resources. In more detail, the present invention is, for example, carbon dioxide (CO ₂₎ of immobilized using a technique for generating a suitable gas-hydrate, and, for example, carbon dioxide (CO ₂₎ was immobilized and parallel The present invention relates to a technique for recovering gas resources in parallel with the generation of gas hydrate suitable for use in mining / recovery of methane (CH ₄ ) gas.

In this specification, a gas resource that is hydrated is referred to as a gas hydrate resource. Specifically, for example, for the CH ₄ hydrate CH ₄ gas is hydrate of a CH ₄ gas is a gas resources Gas Hydrate Resources.

To prevent global warming caused by the massive release of CO _2, hydrate of to e.g. seabed strata recovered CO ₂ without releasing to the atmosphere, lake bottom strata, be secured to the permafrost, etc. have been studied . On the other hand, as a new energy resource, CH ₄ hydrate, which is buried in a large amount in the seabed and the like, has attracted attention, and the mining of CH ₄ hydrate has also been studied. Moreover, it is also studied to mine CH ₄ fixes the CO ₂ by replacing the CH ₄ molecules in the CH ₄ hydrate to CO ₂ molecules.

A research paper (Non-patent Document 1) on the replacement of CH ₄ molecules in CH ₄ hydrate with CO ₂ molecules has been published. In this paper, under the condition where CH ₄ gas, CO ₂ , water, CH ₄ hydrate, and CO ₂ hydrate are mixed, the guest molecule CH ₄ in the hydrate lattice does not decompose the hydrate lattice, It has been thermodynamically discussed that it is replaced by CO ₂ .

  Then, as a method of replacing the gas molecules in the gas hydrate with other gas molecules, the temperature and pressure at which the first guest molecule hydrates in the gap in the formation where the hydrate of the first guest molecule exists A second guest molecule hydrate is produced by injecting an emulsion in which the liquid of the second guest molecule that becomes hydrated at higher temperatures and pressures is made finer than the gaps in the formation and dispersed in water. There is one that decomposes the hydrate of the first guest molecule by the exothermic heat (Patent Document 1).

WO2007 / 023943

Kazunari Ogaki et al. “Use of CH4hydrate and CO2 storage in Nankai Trough”, Chemical Engineering Papers 20 (1), p121-123, January 1994

As assumed in the gas hydrate replacement method of Patent Document 1, in the formation where gas hydrate such as CH ₄ hydrate exists, the existing gas hydrate in the formation is the core, The presence of water (fluid) and CO ₂ (fluid) promotes the production of CO ₂ hydrate (solid).

However, as shown in FIG. 7, the environment where the depth is deep (ie, the pressure P is high and the ground temperature T is high) is a temperature / pressure condition close to the boundary of the stable region of CO ₂ hydrate (gray portion in the figure). It is a condition that it is difficult to generate CO ₂ hydrate. If laboratory experiments, easily CO ₂ hydrate is produced by stirring the surfactant in the impeller or the like in the case of CO ₂ hydrate it will not be generated CO ₂ hydrate even in the temperature and pressure conditions to be stable Become. Here, as because CO ₂ hydrate is easily generated, CO ₂ hydrate will reduce the time from when the stable is obtained temperature and pressure conditions until the CO ₂ hydrate generation is started That is.

  However, it is very difficult to perform stirring using an impeller or the like used in laboratory experiments in the formation. And since the method of patent document 1 utilizes the heat_generation | fever when gas hydrate is produced | generated, if the production | generation of gas hydrate cannot be artificially controlled and accelerated, operativity will be. It's not good, and as a result it's not universal.

  Then, an object of this invention is to provide the production | generation promotion method of the gas hydrate which can artificially control and accelerate | stimulate the production | generation of gas hydrate. Furthermore, the present invention can artificially control and accelerate the generation of gas hydrate and decompose the other gas hydrate by the heat generated during the generation to save the other gas hydrate resources. It is an object of the present invention to provide an enhanced recovery method of gas resources in combination with a gas hydrate generation promotion method that can be efficiently mined and recovered.

In order to achieve such an object, the method for promoting the formation of gas hydrate according to claim 1 is characterized in that a guest molecule liquid is placed in a gap in the formation under temperature and pressure conditions where the guest molecule can be hydrated. in the smaller particles than the gap injected emulsion dispersed in water, an opening of the container is positioned in the open d by the fact that sucked the container surrounding fluid Marushon into the formation in the vacuum The effect of stirring is given.

Therefore, according to the generation method for promoting the gas-hydrate, artificial hydrate of in emulsion gives the effect of agitation as a trigger and Serco was sucked rapidly the fluid opening an opening of a container in a vacuum state The hydrate can be generated quickly by controlling and promoting the control.

  According to this gas hydrate generation promotion method, the liquid of guest molecules is injected into the formation in the form of emulsion dispersed in water as fine particles smaller than the gaps in the formation. Easily enter the gap while displacing seawater and water filling the gaps in the formation without hindering movement, or diffuse into seawater and water, and remain in an emulsion state in which fine particles of guest molecules and seawater are mixed It is distributed uniformly in the formation. And since it inject | pours in a formation after making it into an emulsion state previously, it can be made to disperse | distribute in the ratio of water and a guest molecule suitable for hydrate production | generation.

  The invention according to claim 2 is the method for promoting the formation of gas hydrate according to claim 1, wherein the heat generation per unit amount of the emulsion is achieved by changing the mixing ratio of the guest molecule liquid and water in the emulsion. I try to control the amount. In this case, the temperature of the formation is controlled so as to be a temperature at which gas hydrate is generated.

According to a third aspect of the present invention, in the gas hydrate production promotion method according to the first aspect, the guest molecule is CO ₂ . In this case, it is possible to fix the CO ₂ causing the global warming in the formation by generating hydrates in the gaps in the formation using guest molecules as CO ₂ .

Further, the enhanced recovery method of the gas resource according to claim 4 is a method in which the first guest molecule is hydrated at a temperature / pressure lower than the temperature / pressure at which the first guest molecule is hydrated in the gap in the formation where the hydrate of the first guest molecule exists. Inject an emulsion in which the liquid of the second guest molecule that can be hydrated is made into fine particles smaller than the gap in the formation and dispersed in water, and open the opening of the container placed in the formation under vacuum the first guest reaction heat at the time in parallel as facilitating production of a hydrate of the second guest molecules giving the effect of stirring by the fact that sucked the container surrounding fluid et Marushon and The hydrate of the molecule is decomposed, and the gas of the first guest molecule is recovered while replacing the hydrate of the first guest molecule with the hydrate of the second guest molecule.

Therefore, according to the enhanced recovery method of this gas resources, replacement of hydrate of and guest molecules emulsion giving the effect of agitation as a trigger and Serco was sucked rapidly the fluid opening an opening of a container in a vacuum state In addition, the recovery of the gas can be artificially controlled and promoted, and the hydrate can be generated quickly.

According to this enhanced recovery method of gas resources, the decomposition of the gas hydrate incorporating the first guest molecule proceeds rapidly in parallel with the generation of the gas hydrate incorporating the second guest molecule. Gas hydrate replacement without causing weakening or collapse of the formation. In addition, the atomization of the second guest molecule increases the reaction area necessary for promoting the chemical reaction, and the heat required for the decomposition of the gas hydrate is efficiently generated by the heat generated during the generation of the gas hydrate. Given, the generation of CO ₂ to obtain heat is suppressed.

  The invention according to claim 5 is the enhanced recovery method of gas resources according to claim 4, wherein the mixing rate of the liquid of the second guest molecule in the emulsion and water is changed to change the amount per unit amount of the emulsion. The calorific value is controlled. In this case, the temperature of the formation is controlled so as to be a temperature at which gas hydrate is generated.

The invention according to claim 6 is the gas resource enhanced recovery method according to claim 4, wherein the first guest molecule is CH ₄ and the second guest molecule is CO ₂ . In this case, CH ₄ embedded in the hydrate generation reaction heat is collected while CO _{2 on the} ground that causes global warming is fixed as a stable hydrate in the formation.

Further, enhanced recovery method of gas resources according to claim 7 is, CO ₂ over CH ₄ hydrate layer in the gap between the formation temperature and pressure conditions which can be a hydrate, the CO ₂ liquid in the formation in the smaller particles than the gap injected emulsion dispersed in water, an opening of the container is positioned in the open d by the fact that sucked the container surrounding fluid Marushon into the formation in the vacuum After the formation of a CO ₂ hydrate seal layer with the effect of stirring, the emulsion is injected into the gap between the CH ₄ hydrate layers, and the opening of the container placed in the formation is opened under vacuum. CH ₄ hydrate existing in the gap in parallel with the vessel giving fluid the effect of agitation et Marushon by the bringing drawn near to promote the formation of hydrate of CO ₂ in the reaction heat at the time Te The It is solution, so that to recover the CH ₄ gas while replacing the CH ₄ hydrate to CO ₂ hydrate.

Therefore, according to this enhanced recovery method of gas resources, while the ground CO ₂ that causes global warming is quickly fixed as a stable hydrate in the formation, the heat generated by the hydrate generation reaction at that time Buried CH ₄ can be collected. Moreover, since the mining of the CH ₄ hydrate proceeds while replacing the CH ₄ hydrate with the CO ₂ hydrate, the formation is not weakened or collapsed. In addition, energy for decomposing the CH ₄ hydrate necessary mining CH ₄ hydrate is obtained from the reaction heat of CO ₂ to be fixed to the formation of as waste.

According to this enhanced recovery method of gas resources, a CO ₂ hydrate seal layer is formed in the formation above the CH ₄ hydrate layer to be mined by the gas hydrate generation promotion method of the present invention. The gap between the formations is filled with CO ₂ hydrate and the solid phases are connected to each other and stabilized.

According to this enhanced recovery method of gas resources, the CO ₂ hydrate seal layer is further formed on the formation above the CH ₄ hydrate layer to be mined by the gas hydrate generation promotion method of the present invention. An exothermic layer of CO ₂ hydrate is formed in this formation.

  According to the gas hydrate generation promotion method of claim 1, the hydrate generation start timing can be artificially controlled by using the opening operation of the opening of the container as a trigger.・ It becomes possible to improve operability and improve convenience and versatility. In addition, since hydrates can be generated quickly, a large amount of guest molecules can be fixed in the formation, and the liquid of guest molecules can move and diffuse by groundwater flow and buoyancy. Can be suppressed. In addition, it can be distributed homogeneously in the formation in an emulsion state in which fine particles of guest molecules and seawater are mixed, and it can be dispersed at a ratio of water and guest molecules suitable for hydrate formation. It becomes possible to produce hydrate uniformly and efficiently.

  Furthermore, according to the method for promoting the generation of gas hydrate according to claim 2, it is possible to control the formation so that the temperature of the formation becomes a temperature at which the generation of gas hydrate occurs. It is possible to avoid the hydrate from becoming unstable due to the accompanying rise in the temperature of the formation, and it is possible to reduce the cost because a mechanism for lowering the temperature is not required.

Furthermore, according to the method for promoting the generation of gas hydrate according to claim 3, CO ₂ that causes global warming can be fixed in the formation as a hydrate in a large amount. It becomes possible to contribute to the suppression of global warming.

  According to the gas resource enhanced recovery method of claim 4, since the start timing of hydrate generation and the like can be artificially controlled using the opening operation of the opening of the container as a trigger, hydrate generation and the like It is possible to improve convenience and versatility by improving the controllability and operability of the system. In addition, gas hydrate replacement can be performed without causing weakening or collapse of the formation, so even if a large submarine landslide occurs due to an earthquake during the gas hydrate replacement work, The gas of the second guest molecule injected into it and the gas of the first guest molecule obtained by decomposition leak into the atmosphere, or gas hydrate rises by buoyancy and gasifies and is released into the atmosphere There is almost no danger, and it becomes possible to improve the safety of the recovery operation of the gas resource.

  Further, according to the enhanced recovery method of gas resources according to claim 5, since the temperature of the formation can be controlled to a temperature at which the generation of gas hydrate occurs, the formation associated with the generation of gas hydrate This makes it possible to prevent the hydrate from becoming unstable due to the temperature rise, and it is possible to reduce the cost because a mechanism for lowering the temperature is not required.

Furthermore, according to the enhanced recovery method of gas resources according to claim 6, CO ₂ causing global warming is fixed in the formation as a hydrate in a large amount, and the hydrate generation reaction heat Since embedded CH ₄ can be collected, CH ₄ gas can be collected while contributing to the suppression of global warming.

Further, according to the enhanced recovery method of gas resources according to claim 7, CH ₄ reaction heat of CO ₂ to be fixed to the formation of energy for decomposing the CH ₄ hydrate necessary mining hydrate as waste Therefore, it is possible to give added value to CO ₂ which is waste, and it is possible to effectively use energy. In addition, since the gap between the formations can be filled with CO ₂ hydrate and the solid phases can be connected and stabilized, even if a large-scale submarine landslide occurs due to an earthquake or the like, the decomposition of CH ₄ hydrate There is less risk that the obtained CH ₄ gas leaks into the atmosphere, or CH ₄ hydrate, which has a lower density than seawater, rises by buoyancy and is gasified and released into the atmosphere. It becomes possible to improve safety. In particular, the marine sedimentary layer in which CH ₄ hydrate is buried is beneficial because it is concentrated in the sand layer. In addition, CO ₂ can be fixed as a stable hydrate to both the CH ₄ hydrate layer and the seal layer.

It is a schematic block diagram which shows an example of embodiment of the production | generation promotion method of the gas hydrate of this invention. It is a diagram showing a state of degradation of the product and CH ₄ hydrate of CO ₂ hydrate in the case where the liquid CO ₂ into the gap in the formation and injected atomized. CH ₄ is a schematic diagram showing the mechanism of substitution of the hydrate and the CO ₂ hydrate. It is a figure which shows the schematic structure of the upper end part of an injection well. It is a figure which shows schematic structure of the lower end part of an injection well. It is a schematic block diagram which shows the whole structure of the enhanced recovery method of the gas resource combined with the production | generation promotion method of the gas hydrate of this invention. It is a diagram illustrating the relationship between the CO ₂ hydrate of the stable region and the CH ₄ hydrate of the stable region. The permafrost is generated schematic diagram of the assumed CO ₂ hydrate. Is a diagram showing a state of degradation of the product and CH ₄ hydrate of CO ₂ hydrate in the case where the liquid CO ₂ into the gap in the formation by injecting without atomization. An embodiment of a gas hydrate mining method of the present invention is a schematic view showing an example of a mining CH ₄ hydrate.

  Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings.

  FIG. 1 to FIG. 10 show an example of an embodiment of the method for promoting the generation of gas hydrate of the present invention and the method for enhancing recovery of gas resources in combination with the method for promoting the generation of gas hydrate.

  The method for promoting the generation of gas hydrate of the present invention is such that the guest molecule liquid 4 is placed in the gap 3 in the formation 2 under temperature and pressure conditions where the guest molecules can become the hydrate 6 than in the gap 3 in the formation 2. By injecting the emulsion 5 in the form of small fine particles 23 and dispersing in the dispersion medium 24, by making a vacuum state and opening the opening 20a of the container 20 positioned in the formation 2 to suck in the fluid around the container 20 Alternatively, a fluid and compressed gas are injected to open the opening 20a of the container 20 positioned in the formation 2 and push the fluid from the container 20 to give the emulsion 5 a stirring effect.

  Further, the enhanced recovery method of gas resources combined with the gas hydrate generation promotion method of the present invention increases the temperature of the formation by artificially promoting the formation of gas hydrate within the formation. In this method, a guest molecule is replaced by decomposing a natural gas hydrate generated in the inside, and the first guest is placed in the gap 3 in the formation 2 where the hydrate 1 of the first guest molecule exists. Emulsion in which the liquid 4 of the second guest molecule that can be hydrated at a temperature higher and lower pressure than the temperature / pressure at which the molecule becomes hydrate is dispersed in the dispersion medium 24 as fine particles 23 smaller than the gap 3 in the formation 2 5 and injecting the fluid around the container 20 by opening the opening 20a of the container 20 placed in the formation 2 in a vacuum state, or by fluid and compressed gas The opening 20a of the container 20 that has been injected and positioned in the formation 2 is opened and the fluid is pushed out of the container 20, thereby giving the emulsion 5 an agitation effect and generating the hydrate 6 of the second guest molecule. In parallel with the promotion, the hydrate 1 of the first guest molecule is decomposed by the heat of reaction at that time, and the hydrate 1 of the first guest molecule is replaced with the hydrate 6 of the second guest molecule. The guest molecule gas is collected.

(1. Injection of emulsion in which second guest molecule is dispersed in water)
Reference numeral 25 in FIG. 2 for explaining the mechanism of the present invention is sand particles in the formation 2. The formation 2 is, for example, the formation of the seabed, and the dispersion medium 24 of the emulsion 5 uses water or seawater that generates crystals (or hydrates) that confine guest molecules. Here, the gap 3 in the formation 2 is a gap between solid phases (sand particles, gas hydrate), and is substantially a liquid phase (liquid gas, water, seawater) and gas phase (gas gas) portion. Means the area occupied by That is, liquid guest molecules are ejected as an emulsion in which fine particles 23 smaller than the gaps between solid phases in the formation where gas hydrate is formed are dispersed in a dispersion medium 24 such as seawater or water. In the present invention, the emulsion 5 that enters the gap 3 of the formation 2 is more suitable for hydration as the distribution of the fine particles 23 of the guest molecules is uniform and in a better state.

Here, in the present embodiment, as shown in FIG. 6, an example will be described in which CO ₂ hydrate is generated and CH ₄ hydrate resources (specifically, CH ₄ gas) are mined and recovered. . That is, in the following, the first guest molecule is CH ₄ , the hydrate 1 of the first guest molecule is CH ₄ hydrate, the second guest molecule is CO ₂ and the second guest molecule The case where the hydrate 6 is CO ₂ hydrate and the liquid 4 of the second guest molecule is liquid CO ₂ will be described as an example.

FIG. 7 is a diagram showing a stable region of methane (CH ₄ ) hydrate 1 (shaded portion in the drawing) and a stable region of carbon dioxide (CO ₂ ) hydrate 6 (grey portion in the drawing). As is apparent from FIG. 7, when the temperature T is 283 [K] or lower, and the same pressure P [MPa], the CO ₂ hydrate 6 is higher than the upper limit temperature at which the CH ₄ hydrate 1 exists stably. The upper limit temperature at which is stably present is higher. When the temperature T is 283 [K] or less, the lower limit pressure at which the CO ₂ hydrate 6 exists stably is lower than the lower limit pressure at which the CH ₄ hydrate 1 exists stably if the temperature T is the same. Is low pressure. That is, the temperature T and the pressure P at which the CO ₂ hydrate 6 is stably present are higher than the temperature T and the pressure P at which the CH ₄ hydrate 1 is present stably.

Then, indicated by the symbol X in FIG. 7, CH ₄ stable region (hatched portion) of the hydrate 1 stable region (in the figure gray portion) of CO ₂ hydrate 6 not overlap, CO ₂ hydrate 6 Is a region of temperature and pressure conditions in which the generation of CH ₄ and decomposition of CH ₄ hydrate 1 occur simultaneously. In the present invention, this region is used to replace CH ₄ hydrate 1 with CO ₂ hydrate 6. Then, by replacing CH ₄ hydrate 1 with CO ₂ hydrate 6, CH ₄ is mined and recovered while CO ₂ is fixed.

Here, the place where natural CH ₄ hydrate concentrates in the ocean ground is a sand layer, and when collecting CH ₄ hydrate resources, this concentrated area is usually targeted for mining. Then, there is CH ₄ hydrate in a gap that forms a three-dimensional reticulated structure of about 50% sand, it is known that up to 60% of the gap is CH ₄ hydrate. Therefore, in the present embodiment, the seabed formation 2 is described as a CH ₄ hydrate mining target and a CO ₂ hydrate fixing target.

As shown in FIG. 3, the lower ends of the injection well 7 and the production well 8 reach the formation 2 where the CH ₄ hydrate is generated. A platform 9 is provided on the sea, and an injection well 7 and a production well 8 are lowered from the platform 9 to the seabed. The upper end of the production well 8 is connected to a pump (not shown), and pumps CH ₄ gas together with the seawater 24 filling the gap in the formation 2. The CH ₄ gas pumped up by the production well 8 is separated from the seawater 24 and then used for power generation at, for example, a thermal power plant 26.

For example, as shown in FIG. 4, the injection well 7 has a double tube structure in which an inner tube 11 is arranged in an outer tube 10. The upper end of the inner pipe 11 is connected to the liquid CO ₂ tank 12, and the inner pipe 11 serves as a passage through which the liquid CO ₂ 4 flows. Liquid CO ₂ 4, which is stored in liquid CO ₂ tank 12, for example, thermal power plant 26, steelworks, in which liquefied recovered been CO ₂ emissions from cement plants and the like.

As shown in FIG. 5, liquid CO ₂ 4 is injected into the flow path surrounded by the outer tube 10 as fine particles 23 (see FIG. 2) smaller than the gap 3 in the formation 2 at the tip of the inner tube 11. A spray nozzle 13 is provided. A high-speed flow of liquid CO ₂ 4 is created in the spray nozzle 13 and the liquid CO ₂ 4 is atomized by the effects of shearing and collision. As a method of atomizing the liquid by the nozzle, a general method used also in spraying can be applied. Specifically, for example, the pressure difference of the liquid CO ₂ 4 before and after the spray nozzle 13 is set to 1 [MPa] to several By setting the pressure to 10 [MPa], the flow rate of the liquid CO ₂ 4 in the spray nozzle 13 is made to be about the speed of sound, and thereby the particle size of the fine particles 23 of the liquid CO ₂ 4 ejected from the spray nozzle 13 can be reduced to the order of μm or less. Is possible.

Here, the average particle diameter of the fine particles 23 (see FIG. 2) of the liquid CO ₂ at the time of spraying needs to be smaller than the gap in the formation where the gas hydrate is formed, that is, the gap between the solid phases. For example, it is preferable that the thickness be several [μm] to 30 [μm]. In this case, it is considered that the fine particles have a particle diameter sufficiently smaller than the gap in the formation where the hydrate is generated.

The upper end of the outer tube 10 is connected to a discharge port of a pump 14 that pumps and discharges seawater 24 from the ocean 31, and a passage through which the seawater 24 flows is provided between the outer tube 10 and the inner tube 11. By injecting the fine particles 23 of the liquid CO ₂ 4 from the nozzle 13 into the flow of the sea water 24 between the outer tube 10 and the inner tube 11, the liquid CO ₂ 4 becomes fine particles 23 smaller than the gap 3 and enters the sea water 24. A dispersed CO ₂ / water emulsion 5 can be produced immediately before jetting into the formation 2. The pumping of the seawater 24 from the ocean 31 is performed from an arbitrary depth up to the seabed by adjusting the length of the suction pipe 14a. The outer tube 10 is, for example, a drill rod, for ejecting the generated CO ₂ / water emulsion 5 evenly into the formation 2 before the tip of the inner tube 11 equipped with the spray nozzle 13. A large number of jet nozzles 10a are provided on the peripheral surface.

Thus, the water / CO ₂ mass ratio of the emulsion 5 can be adjusted to a suitable ratio in accordance with the purpose of generating hydrate in the injection well 7 before being injected into the formation 2. For example, in the case where the objective is to generate hydrate in the target formation 2 and to stably fix guest molecules, the replacement of the gas hydrate guest molecules already present in the formation with the supplied guest molecules Hydrate generation for the purpose, or when it is intended to use the heat of reaction at the time of hydrate generation as a heat source when mining and recovering natural resources existing in the formation in the form of hydrate It can be adjusted to a water / CO ₂ mixing ratio according to the purpose.

For example, as in the present embodiment, to decompose CH ₄ hydrate in parallel with and fixed to the CO ₂ in the hydrate into the formation 2 CH ₄ hydrate is Enrichment into water and CH ₄ gas When CH ₄ hydrate is mined and recovered by replacing CH ₄ hydrate in the formation with CO ₂ hydrate by recovery, water / CO ₂ suitable for the generation and stability of CO ₂ hydrate It is preferable to adjust so that it may become mass ratio.

In addition, by adjusting the temperature of seawater or water used as the dispersion medium of emulsion 5 or the temperature of liquid CO ₂ , it is possible to prevent the formation of gas hydrates from the temperature conditions of the formation and the temperature rise conditions of the formation. It is also possible to inject as emulsion 5 at the optimum temperature to produce and stabilize the rate. For example, if the depth at which the seawater 24 is collected is changed, water / seawater at a required temperature can be easily obtained.

The emulsion 5 sprayed from the injection well 7 enters the gap while pushing away the seawater filling the gap 3 of the CH ₄ hydrate layer 2, and liquid CO ₂ (fine particles 23) and seawater (dispersion medium 24) at a uniform ratio. And go to the gap 3.

(2. Method for promoting hydrate formation of second guest molecule)
The CH ₄ hydrate 1 is stably present in the gap 3 into which the emulsion 5 has entered (seawater temperature is 283 [K] or less). That is, the gap 3 is a temperature / pressure condition in which CO ₂ hydrate can exist stably.

In the present invention, the hydrate formation of the CO ₂ / water emulsion 5 that has entered the gap 3 is promoted using the pressure vessel 20.

Boring holes at a depth where the CH ₄ hydrate 1 exists stably and the CO ₄ / water emulsion 5 reaches the CH ₄ hydrate layer 2 toward the CH ₄ hydrate layer 2 supplied to the gap 3. 30 is formed. Then, the pressure vessel 20 attached to the lower end of the cable 28 is suspended in the boring hole 30 and positioned at a depth in the CH ₄ hydrate layer 2.

  The pressure-resistant container 20 has an opening 20a provided with at least an opening operable valve on the side wall. The opening operation of the valve of the opening 20a may be started automatically by providing a timer in the pressure vessel 20 or by using the cable 28 itself as an electric signal cable or along the cable 28. The electric signal may be transmitted by the arranged electric signal cable so that it can be remotely operated by the electric signal. The pressure vessel 20 may be provided with a plurality of openings 20a. In that case, the plurality of openings 20a simultaneously perform the opening operation.

  The pressure vessel 20 is depressurized and evacuated. The pressure vessel 20 may be depressurized in advance at sea or on the ground, or a pressure reducing mechanism may be provided in the pressure vessel 20 and the pressure reducing mechanism 20 may be used in the borehole 30. In addition, the valve of the opening 20a has a sealing property to such an extent that the vacuum state can be maintained in a state where the inside of the pressure-resistant container 20 is vacuum.

  In the present embodiment, an upper packer 21A is provided above the pressure vessel 20 and a lower packer 21B is provided below. The upper and lower packers 21A and 21B are made of, for example, a resin that expands with air and exhibits a sealing property that restricts the flow of fluid in the boring hole 30.

The pressure vessel 20 with the upper and lower packers 21A and 21B is positioned at a predetermined depth in the CH ₄ hydrate layer 2, and both the packers 21A and 21B are expanded so that the bore holes 30 are formed above and below the pressure vessel 20. Seal. Since the pressure vessel 20 is located in the CH ₄ hydrate layer 2, at least the periphery of the pressure vessel 20 has temperature and pressure conditions in which the CO ₂ hydrate is stable.

The valve of the opening 20a is opened at a predetermined depth. Then, the CO ₂ / water emulsion 5 and the seawater 24 in the portion sandwiched between the upper packer 21A and the lower packer 21B of the boring hole 30 (that is, around the side wall of the pressure vessel 20) rapidly and suddenly enter the pressure vessel 20. Inhaled.

At this time, since the fluid flow is restricted by the upper and lower packers 21A and 21B in the upper and lower sides of the pressure vessel 20 in the boring hole 30, the water above and below the pressure vessel 20 in the boring hole 30 is the pressure vessel 20 The CO ₂ / water emulsion 5 and the seawater 24 around the borehole 30 at a depth where the pressure vessel 20 is located flow instantaneously and rapidly into the borehole 30 and into the pressure vessel 20. As a result, a rapid flow occurs in the CO ₂ / water emulsion 5 around the bore hole 30.

Further, in the pressure vessel 20 is in when momentarily filled with CO ₂ / water emulsions 5 and sea water 24, (also known as water hammer) CO ₂ / flow water emulsion 5 and sea water 24 is stopped abruptly water hammering Occurs. Thereby, an impact and vibration are given to the CO ₂ / water emulsion 5 around the boring hole 30.

By such an instantaneous and rapid flow due to the opening of the opening 20a of the pressure vessel 20, the stirring effect is given to the CO ₂ / water emulsion 5 that has entered the gap 3 of the CH ₄ hydrate layer 2. Furthermore, the stirring effect is enhanced by the impact and vibration caused by the water hammer action. Here, the effect of stirring is that the area of the interface (contact surface) between CO ₂ and water increases, in other words, a CO ₂ / water emulsion in which fine droplets are present. And, by the effect of this stirring, the hydrate is reliably generated and promoted even under the temperature and pressure conditions where the CO ₂ hydrate is stable, but under the condition where the CO ₂ hydrate is hardly generated.

By the effect of the agitation is provided to the CO ₂ / water emulsion 5 by momentary and rapid flow, CO ₂ hydrate is induced CO ₂ hydrate formation in the temperature and pressure conditions can be stable. The CO ₂ hydrate formation of the CO ₂ / water emulsion 5 first occurs in the immediate vicinity of the boring hole 30, and the hydrate formation range (in other words, the spillover range of the stirring effect) gradually propagates concentrically around the periphery. Proceed by spreading as you do. In addition, the generation of CO ₂ hydrate proceeds rapidly due to the effect of stirring.

The size of the pressure vessel 20 and the degree of pressure reduction (in other words, the size of the pressure difference caused by the opening of the opening 20a) take into account the amount of CO ₂ / water emulsion 5 to be hydrated and the range of its entry. Is set appropriately.

In the present invention, as described above, the hydrate of the emulsion 5 is provided by supplying a trigger for hydrate formation using the pressure vessel 20 after supplying the CO ₂ / water emulsion 5 to the gap 3 of the CH ₄ hydrate layer 2. Is started. Therefore, according to the present invention, generation of gas hydrate can be artificially controlled and promoted. Incidentally, hydrate formation triggering by pressure vessel 20 can cause CO ₂ / CO ₂ hydrate of the water emulsion 5 within a certain range be given once, it is not necessary to provide continuous in the same place.

  According to the above contents of the present invention, it is possible to promote the generation of gas hydrate in a predetermined formation.

(3. Decomposition of hydrate of first guest molecule and recovery of hydrate resource)
The formation of hydrate is an exothermic reaction, and the decomposition of hydrate is an endothermic reaction. Due to the heat generated when the CO ₂ hydrate 6 is generated, the temperature of the formation 2 including the solid and liquid phases around it rises, and the CH ₄ hydrate 1 is decomposed. For example, if the temperature from the state of point P1 in FIG. 7 shifts to the state of rising to the point P2, the gap 3 is CH ₄ stable region while belonging to the CO ₂ stability region of Fig. 7 (figure gray area) Deviates from (shaded area in the figure). Therefore, the CH ₄ hydrate 1 in the gap 3 is decomposed while the CO ₂ hydrate 6 is stably present, and the hydrate existing in the gap 3 is changed from the CH ₄ hydrate 1 to the CO ₂ hydrate 6. Is replaced by Although wherein substitution at the phenomenon CH ₄ hydrate 1 is decomposed with in CO ₂ hydrate 6 is produced is mainly not occur decomposition of CH ₄ hydrate 1 guest molecule Part of the phenomenon in which certain CH ₄ is replaced by CO ₂ has also occurred.

Since the heat generated during the generation of the CO ₂ hydrate 6 is absorbed when the CH ₄ hydrate 1 is decomposed, the temperature of the gap 3 and the formation 2 exceeds the temperature at which the CO ₂ hydrate is generated and stable. It will not rise. For this reason, the produced CO ₂ hydrate 6 remains stable.

CH ₄ gas 27 is generated by the decomposition of CH ₄ hydrate 1. The CH ₄ gas 27 becomes bubbles and floats in the seawater 24 flowing through the gap 3. A part of the generated CH ₄ gas 27 is dissolved in the seawater 24. On the other hand, since the emulsion 5 is discharged from the injection well 7 and the production well 8 sucks up the seawater 24, the seawater 24 from the injection well 7 to the production well 8 is inserted in the gap 3 of the CH ₄ hydrate layer 2. There is a flow. Therefore, the CH ₄ gas 27 dissolved in the bubble and the seawater 24 of CH ₄ gas 27 generated is recovered from a production well 8 with seawater 24.

In this way, CO ₂ is injected into the seabed formation to produce CO ₂ hydrate, and the temperature of the formation 2 is raised by the hydrate formation reaction heat at that time, and CH ₄ hydrate, which is an effective resource in the seabed ground. By substituting CO ₂ hydrate while decomposing rate 1, fixation of CO ₂ , mining and recovery of CH ₄ hydrate 1, and restoration and stabilization of formation strength can be performed simultaneously. It is also possible to simply use a guest molecule (for example, CO ₂ in the present embodiment) to generate and fix a gas hydrate as a warming agent.

Since the liquid CO ₂ in the emulsion 5 is made into fine particles 23 smaller than the gap 3 in the formation 2, the liquid CO ₂ can easily enter the gap 3 in the formation 2 without being disturbed in movement like water. , Disperse with uniform distribution without hindering movement. Therefore, it is possible to uniformly disperse the liquid CO ₂ over a wide range in the gap 3 in the formation 2 at a rate or in proportion close to that of water and CO ₂ suitable for hydrate formation, CO ₂ hydrate 6 can be produced uniformly over a wide range.

Further, since the liquid CO ₂ is made into fine particles, the contact area between the liquid CO ₂ (fine particles 23) and seawater (dispersion medium 24) increases. For example, when the liquid CO ₂ fine particles 23 are spherical, when the radius is 1/10, the number of particles per unit volume is 1000 times, the surface area of each fine particle 23 is 1/100, and the sum of the surface areas per unit volume is 10 times. For example, on the basis of the surface area when the radius of the fine particles 23 is 1 [mm], when the diameter of the fine particles 23 is 0.01 [mm] or 0.001 [mm], the sum of the surface areas per unit volume is respectively 100 times or 1000 times. Thus, the contact area between the liquid CO ₂ (fine particles 23) and the seawater 24 can be increased, so that the contact area between the two can be increased and the production of CO ₂ hydrate 6 can be ensured. .

Incidentally, in FIG. 9 show a case where the liquid CO ₂ 4 in the gap 3 in the formation 2 was injected remained concentration close to 100% without the particles of the liquid CO _2. In this case, in order to enter the seawater 24 that fills the gap 3 into the gap 3 while pushing away with liquid CO ₂ 4, and the liquid CO ₂ 4 and seawater 24 contact only at the boundary, the liquid CO ₂ at its inner side Therefore, it is almost impossible to uniformly distribute water and CO _{2 in} a proportion suitable for the hydrate production reaction in the gap 3.

In the present invention, since the liquid CO ₂ is made into fine particles smaller than the gap 3 of the formation 2 and supplied in advance as an emulsion, the emulsion 5 injected from the injection well 7 into the gap 3 of the CH ₄ hydrate layer 2. By changing the mixing ratio of liquid CO ₂ (fine particles 23) and water (dispersion medium 24), the amount of heat generated per unit amount of the emulsion 5 can be controlled. For example, the mixing ratio of the liquid CO ₂ (fine particles 23) and the sea water (dispersion medium 24) in the emulsion 5 is changed by adjusting the ratio between the flow rate of the liquid CO ₂ 4 in the injection well 7 and the flow rate of the sea water 24. The amount of heat generated per unit amount of the emulsion 5 can be controlled.

The ratio of the number of guest molecules constituting the hydrate to the number of water molecules is determined for each type of guest molecule. The mixing ratio of liquid CO ₂ in the emulsion 5 (the fine particles 23) and seawater (dispersion medium 24), CO ₂ hydrate 6 number of molecules CO ₂ constituting the water molecules number and percentage close when the emulsion 5 The amount of hydrate produced per unit amount increases and the calorific value also increases. Conversely, the mixing ratio of liquid CO ₂ in the emulsion 5 (the fine particles 23) and seawater (dispersion medium 24), moved away from the ratio of the CO ₂ hydrate 6 number of molecules of CO ₂ constituting the water molecules Number The amount of hydrate produced per unit amount of the emulsion 5 decreases, and the calorific value also decreases. Therefore, by changing the mixing ratio of the liquid CO ₂ (fine particles 23) and the seawater (dispersion medium 24) in the emulsion 5, the calorific value per unit amount at the time of CO ₂ hydrate generation can be controlled. By controlling the amount of heat generated per unit amount of the emulsion 5 during CO ₂ hydrate formation, it is possible to control the temperature rise of the formation 2. By controlling the temperature of the formation 2, it is possible to maintain the temperature at which gas hydrate is generated, or to adjust the decomposition amount of the hydrate to be replaced, mined or recovered, for example, CH ₄ hydrate 1.

FIG. 8 shows a schematic diagram of CO ₂ hydrate generation assuming a permafrost layer. Specifically, a CO ₂ emulsion is injected into the permafrost layer so as to surround the CH ₄ hydrate in the permafrost layer, and the CO ₂ emulsion is stirred using the above-described method for promoting the formation of gas hydrate. An effect is provided to quickly produce CO ₂ hydrate artificially, and the temperature of the permafrost is increased by the heat of hydrate formation reaction at that time, and the CH ₄ hydrate is decomposed and replaced with CO ₂ hydrate. In this way, it is possible to promote the production of artificially CO ₂ hydrate CH ₄ in permafrost in the hydrate is present at a temperature and pressure conditions as the CO ₂ hydrate of the stable region.

(4. Formation of seal layer)
When mining and collecting gas hydrate, a gas / hydrate seal layer that is stable even at a higher temperature and lower pressure than the gas hydrate to be mined is previously placed on the gas hydrate layer to be mined. It is preferable to form it. For example, in the mining of CH ₄ hydrate of the present embodiment, hydrate replacement is performed after the formation of the CO ₂ hydrate seal layer 22 on the formation 2 where the CH ₄ hydrate is generated. Is preferred. CO ₂ is stable as a hydrate under conditions of high temperature and low pressure as compared with CH _4, and is therefore suitable as the seal layer 22 formed on the formation 2 where the CH ₄ hydrate is generated.

Specifically, first, an injection well 29 that penetrates the formation 2 under the temperature and pressure conditions where CO ₂ can be hydrated is formed on the formation 2 where CH ₄ hydrate is generated, and the solid of the formation is formed. A CO ₂ / water emulsion 5 in which liquid CO ₂ having fine particles smaller than the gap is dispersed in seawater is injected into the gaps between the particles, and the sealing layer 22 is formed by giving a stirring effect by the pressure vessel 20. Thereafter, the above-mentioned CO ₂ / water emulsion 5 is injected into the gap 3 between the solid particles of the formation 2 where the CH ₄ hydrate is generated, and a CO ₂ hydrate is formed by giving a stirring effect by the pressure vessel 20. On the other hand, the CH ₄ hydrate present in the gap 3 is decomposed using the reaction heat at that time. CH ₄ gas 27 produced by the decomposition of CH ₄ hydrate is recovered from the production well 8 without leaking is trapped in the seal layer 22 to the sea and air. Thus, CH ₄ hydrate is embedded into the formation 2 while being replaced by CO ₂ hydrate CH ₄ gas is recovered.

In the case where the seal layer 22 is formed by the generation of gas hydrate, when natural gas hydrate is formed in a formation that is not buried, heat absorption due to decomposition of the gas hydrate cannot be expected. It may be necessary to adjust the temperature by adjusting the temperature of the emulsion 5 or the average particle size of the liquid guest molecular fine particles so that the temperature at which the gas hydrate forming the layer 22 is generated is obtained. For example, when CO ₂ is used as a guest molecule, the amount of seawater mixed with the liquid CO ₂ fine particles 23 of the CO ₂ / water emulsion is increased, or the seawater to be mixed is changed to a lower temperature seawater. Some ideas may be required. Further, the heat generation amount per unit amount of the emulsion 5 may be controlled by changing the mixing ratio of the liquid CO ₂ 4 and the water 24 in the emulsion 5.

FIG. 10 shows an embodiment of another gas hydrate mining method. In this gas hydrate mining method, a CO ₂ hydrate dome-shaped seal layer 22 is first formed on a CH ₄ hydrate layer 32 to be mined, and then further under the CH ₄ hydrate layer 32. The CO ₂ hydrate layer 33 for fixing CO ₂ to the formation is formed, and the temperature of the formation 33 into which the CO ₂ emulsion is injected is raised using the heat of reaction at that time to raise the CH ₄ hydrate on the formation 33 The CH ₄ hydrate of the layer 32 is decomposed into water and CH ₄ gas from the bottom.

CH ₄ gas 27 generated by the decomposition of CH ₄ hydrate layer 32 is recovered to the ground by the production well 8 are collected in the seal layer 22 of the dome-shaped. Then, the CO ₂ / water emulsion 5 is injected into the formation after the CH ₄ hydrate mining by raising the injection well 7 or installing another injection well penetrating the CH ₄ hydrate layer 32. CO ₂ hydrate is generated, and solid phases such as unconsolidated sand particles are connected with CO ₂ hydrate to restore the strength of the formation. As a result, a large amount of CO ₂ can be immobilized on the three layers 22, 32, and 33 as a stable hydrate in the seabed sedimentary layer while safely mining and collecting methane gas from the CH ₄ hydrate 32.

Incidentally, CH ₄ since the upper hydrate layer 32 is stabilized solid phase coupled strata by the generation of CO ₂ hydrate constituting the sealing layer 22 prior to mining of CH ₄ hydrate, large by an earthquake When a large-scale submarine landslide occurs, CH ₄ gas obtained by decomposition of CH ₄ hydrate leaks into the atmosphere, or CH ₄ hydrate with a density lower than seawater rises by buoyancy to gasify the atmosphere There is little risk of being released inside.

According to the gas resource enhanced recovery method of the present invention configured as described above, the start timing of hydrate generation and the like can be artificially controlled using the opening operation of the opening 20a of the container 20 as a trigger. In addition, it is possible to improve convenience and versatility by improving controllability and operability such as hydrate generation. In addition, according to the present invention, gas hydrate can be generated quickly, so that not only substitution with other gas hydrates or mining of resource hydrates, but guest molecules are hydrated in the formation. It is also suitable for immobilization and storage. For example, it is suitable as a technique for fixing CO ₂ gas.

In addition, although the above-mentioned form is an example of the suitable form of this invention, it is not limited to this, A various deformation | transformation implementation is possible in the range which does not deviate from the summary of this invention. For example, (in particular CH ₄ gas) substituted and CH ₄ hydrate resources and fixed, CO ₂ hydrate and CH ₄ hydrate by hydrate of CO ₂ in the embodiment described above as an example the recovery of As described mainly, the target guest molecules are not limited to CO ₂ and CH ₄ . It is clear that the gas hydrate formation promotion method of the present invention can be applied to any guest molecule that generates gas hydrate, and the stable temperature and temperature of the enhanced recovery method of the gas resource of the present invention by hydrate replacement This is established between combinations of two types of guest molecules having different pressure conditions. For example, natural gas hydrate guest molecules include methane (CH ₄ ), ethane (C ₂ H ₆ ), propane (CH ₃ CH ₂ CH ₃ ), carbon dioxide (CO ₂ ), hydrogen sulfide (H ₂ ). S) and air (nitrogen (N ₂ )) are known, and it is clear that the present invention can be applied to the production and replacement of these gas hydrates and the recovery of gas hydrate resources.

In the embodiment described above, the method of generating the gas hydrate in submarine sedimentary sand is centered, has been mainly described recovery method of replacement method and gas hydrate resources, of course, lake of CH ₄ It can be applied to formations such as hydrate formations and formations such as permafrost CH ₄ hydrate formations, and it is injected into the formation gaps as emulsion 5 containing water necessary for hydrate formation. It is also possible to carry out fixation, displacement and recovery of gas hydrate resources by generating hydrates of guest molecules in the formation where water is not present.

Further, in the above-described embodiment, liquid CO ₂ is injected into water / sea water before being injected into the formation to obtain an emulsion. However, depending on the situation of the formation, the formation in which CH ₄ hydrate exists Liquid CO ₂ may be directly ejected from the spray nozzle to disperse the fine particles of liquid CO _{2 in} seawater or the like in the formation to form an emulsion, which may be further diffused into the formation using the energy of the ejection. .

Further, in the above-described embodiment, the opening portion 20a of the pressure-resistant vessel 20 that has been depressurized and evacuated is opened, and the CO ₄ / water emulsion 5 and the seawater 24 are instantaneously aspirated into the vessel 20 to CH _4. Although a stirring effect is given to the CO ₂ / water emulsion 5 in the hydrate layer 2, a pressure vessel in which a compressed gas such as CO ₂ / water emulsion or seawater or other fluid and compressed air is injected. The opening 20a of 20 may be opened, and the CO ₂ / water emulsion or seawater in the container 20 may be pushed out instantaneously and suddenly. Also in this case, the stirring effect is given to the CO ₂ / water emulsion 5 by the rapid vibration and flow.

In addition, the valve of the opening 20a of the pressure vessel 20 can be remotely operated, and the pressure vessel 20 is provided with a container content discharging mechanism and a pressure reducing mechanism. After opening the opening 20a, the opening 20a is closed and the pressure vessel is closed. It is possible to discharge the contents sucked into the inside 20 and decompress the inside of the boring hole 30, and to continuously set the vacuum state of the pressure vessel 20 and the opening operation so that the depth in the CH ₄ hydrate layer 2 is increased. The stirring effect may be continuously given to the CO ₂ / water emulsion 5 while changing.

  In the above-described embodiment, the packers 21A and 21B are provided on both the upper and lower sides of the pressure vessel 20. However, the packers 21A and 21B seal the boring holes 30 on the upper and lower sides of the pressure vessel 20. Therefore, when the pressure vessel 20 is used while being grounded to the bottom of the boring hole 30, the lower packer 21B is not provided. Also good.

1 CH ₄ hydrate (hydrate of the first guest molecule)
2 Formation in which CH ₄ hydrate is generated 3 Gap in formation 4 Liquid CO ₂ (Liquid of second guest molecule)
5 CO ₂ / water emulsion 6 CO ₂ hydrate (hydrate of second guest molecule)
20 Pressure-resistant container 21A Upper packer 21B Lower packer 23 Fine particles of liquid CO ₂ (liquid fine particles of second guest molecule)
28 Cable 30 Boring hole

Claims (7)

An emulsion in which the guest molecule liquid is made into fine particles smaller than the gap in the formation and dispersed in water is injected into a gap in the formation under temperature and pressure conditions where the guest molecule can be hydrated, and a vacuum state is established. generating method for promoting gas-hydrate, characterized in that to provide the effect of agitation before Symbol emulsion by the making sucked the container around the fluid by opening the opening of the container is positioned in the strata Te .   The generation promotion of gas hydrate according to claim 1, wherein a heat generation amount per unit amount of the emulsion is controlled by changing a mixing ratio of the guest molecule liquid and the water in the emulsion. Method. The method for promoting the generation of gas hydrate according to claim 1, wherein the guest molecule is CO ₂ . In the gap in the formation where the hydrate of the first guest molecule exists, the liquid of the second guest molecule that can be hydrated at a higher temperature and lower pressure than the temperature and pressure at which the first guest molecule hydrates. Injecting emulsion that is made into fine particles smaller than the gap in the formation and dispersed in water, and opening the opening of the container located in the formation under vacuum to suck in the fluid around the container depending by decomposing the hydrate of the first guest molecule in the case of reaction heat in parallel with the previous SL giving effect of agitation to the emulsion to facilitate the formation of hydrate of the second guest molecule, wherein A method for enhanced recovery of a gas resource, wherein the gas of the first guest molecule is recovered while replacing the hydrate of the first guest molecule with the hydrate of the second guest molecule.   5. The gas resource enhancement according to claim 4, wherein a heat generation amount per unit amount of the emulsion is controlled by changing a mixing ratio of the liquid of the second guest molecule in the emulsion and the water. Recovery method. 5. The method for enhanced recovery of a gas resource according to claim ₄ , wherein the first guest molecule is CH ₄ and the second guest molecule is CO ₂ . An emulsion in which the CO ₂ liquid is dispersed in water as fine particles smaller than the gaps in the formation in the gaps of the formation under temperature and pressure conditions where CO ₂ on the CH ₄ hydrate layer can become hydrates. injected, hydrate of the CO ₂ to give the effect of agitation before Symbol emulsion by the opened opening of the container is positioned to allow sucked the container surrounding fluid in said formation in the vacuum After the sealing layer is formed, the emulsion is injected into the gap between the CH ₄ hydrate layers, and a vacuum is applied to open the opening of the container positioned in the formation to suck in the fluid around the container. It said to decompose the CH ₄ hydrate present in the gap in the reaction heat at the time in parallel as facilitating production of a hydrate of the CO ₂ to give the effect of agitation before Symbol emulsion by that Enhanced recovery method of gas resources and recovering the CH ₄ gas while replacing the CH ₄ hydrate the CO ₂ hydrate.