JP2018043176A - Gas injection system and storage method in carbon dioxide ground - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique to the residual gas in storage in the carbon dioxide ground.SOLUTION: High pressure water and carbon dioxide are fed to the lower part of a borehole 2 by a pump 6 and a compressor 7 from the surface, and the carbon dioxide micro-bubbled by a micro-bubble water generation part 15 is injected into an aquifer as micro-bubble water. On the other hand, the carbon dioxide (residual gas) not stored in the ground is generated. The residual gas rises through an exhaust line 16 and is recovered by an exhaust recovery tank 17. The carbon dioxide in the exhaust recovery tank 17 is fed to the ground once more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a carbon dioxide underground storage technology for preventing global warming and the like.

  Reduction of carbon dioxide (CO2) emissions has been strongly demanded to prevent global warming. As one of the measures for reducing the amount of carbon dioxide emitted into the atmosphere, a method of storing the discharged carbon dioxide in the ground without releasing it into the atmosphere is being studied.

  By storing carbon dioxide in a dissolved aquifer below the impermeable layer of clay or the like, leakage of carbon dioxide after injection to the ground can be prevented.

  Furthermore, in order to stably store carbon dioxide, a technique related to microbubble water has attracted attention. (For example, Patent Document 1 or Patent Document 2).

  Microbubble water is obtained by dissolving a gas into micro-sized fine bubbles (microbubbles).

  Since microbubbles have low buoyancy, they exist in the solution while performing Brownian motion, and are highly stable. In addition, by charging the same charge, the microbubbles are unlikely to coalesce and remain small. This point is also highly stable. Furthermore, the solubility of carbon dioxide is improved by the self-pressurizing effect of the microbubbles. In addition, it is extremely safe because it does not use highly toxic chemicals.

  That is, the carbon dioxide dissolved in the microbubble water is stably and efficiently stored in the aquifer.

Japanese Patent Application Laid-Open No. 2010-199962 JP 2006-016348 A

  However, the above technology is based on the premise that carbon dioxide is completely microbubbled and injected entirely into the ground, and it is not considered that surplus gas that has been stored underground is generated. It was.

  Therefore, the recovery of surplus gas and the problems at that time have not been studied.

  This invention solves the said subject, and it aims at providing the technique with respect to the surplus gas in carbon dioxide underground storage.

  The present invention that solves the above problems is a gas injection system that uses microbubble water as a gas, injects the gas into the aquifer below the impermeable layer, and recovers the gas that has not been injected into the aquifer from the ground. .

  The present invention that solves the above-described problems is a water blocking device that shields the inside of a borehole drilled from an impermeable layer to a lower aquifer, and water that supplies water to a space formed below by the shielding plug. From the supply line, a gas supply line that supplies gas to a space formed below by the shielding plug, a microbubble water generation unit that mixes and stirs the water and gas and generates microbubble water, and the space It is a gas injection system provided with the exhaust line which collect | recovers the gas which was not inject | poured from the ground among the microbubble water inject | poured into an aquifer.

  In this invention, Preferably, the control means which controls the pressure of the gas collect | recovered without being inject | poured into the said aquifer is provided.

  In the present invention, preferably, control is performed so that the pressure of the gas recovered without being injected into the aquifer is lower than the pressure injected into the aquifer and higher than the pore water pressure of the aquifer. Means.

  Thereby, it is possible to prevent the groundwater from being ejected from the exhaust line for collecting the gas that has not been injected.

  The present invention that solves the above-mentioned problems is to use carbon dioxide as microbubble water, inject the microbubble water into an aquifer below the impermeable layer, and collect carbon dioxide that has not been injected into the aquifer at the ground surface. This is a carbon dioxide underground storage method.

  According to the present invention, carbon dioxide (surplus gas) that could not be stored underground can be recovered.

It is a whole block diagram of this embodiment. It is a detailed block diagram in a boring hole lower end. It is a functional block diagram of a control device. It is explanatory drawing about the effect by microbubble formation.

~Overview~
First, an example of the configuration of the gas injection system according to the present embodiment will be described. Next, the operation and control when the gas injection system according to the present embodiment is applied to underground storage of carbon dioxide will be described. Further, as a remark, the background that led to the present invention will be described.

  Note that the microbubble water has a mixture of a gas dissolved in water and a fine bubble (microbubble) state. Further, the fine bubbles become finer and dissolve by self-crushing.

~System configuration~
FIG. 1 is an overall configuration diagram of a gas injection system according to the present embodiment. FIG. 2 is a detailed configuration diagram at the lower end of the boring hole.

  The gas injection system 1 is provided in the boring hole 2. The borehole 2 penetrates the impermeable layer 3 from the ground surface, and is drilled to the aquifer 4 below the impermeable layer 3.

  The impermeable layer is a ground layer through which groundwater does not permeate or is difficult to permeate, and is made of silt or clay. An aquifer is a stratum saturated with groundwater.

  The side surface of the borehole 2 that contacts the aquifer 4 is a strainer, and the borehole 2 and the aquifer 4 are in communication.

  The gas injection system 1 includes a pump 6, a compressor 7, a compressor 8, a shielding plug 11, a water supply line 12, a gas supply line 13, a microbubble water generator 15, an exhaust line 16, and exhaust recovery. A tank 17 and a valve 18 are provided.

  The shielding plug 11 is provided at the lower part of the boring hole 2. The shielding plug 11 is, for example, a rubber packer, which is inflated by air supplied from the ground surface via the packer extension line 31 and shields the inside of the borehole by air pressure. When the boring hole 2 is deep, the shield plug 11 lowered to a predetermined depth by the SUS wire 32 and inflated by the hydraulic pressure is suspended and supported.

  By the shielding plug 11, a space continuous to the aquifer 4 is formed at the lower part of the borehole 2.

  The water supply line 12 and the gas supply line 13 penetrate the shielding plug 11 from the ground surface and reach the lower part of the borehole 2. The water supply line 12 supplies water from the ground surface to the lower portion of the borehole 2 via the pump 6. The gas supply line 13 supplies gas from the ground surface to the lower portion of the boring hole 2 via the compressor 7.

  The water supply line 12 and the gas supply line 13 are connected to the microbubble water generator 15 at the ends. The pump 6 compresses water to a high pressure. The compressor 7 compresses the gas to a high pressure.

  The micro-bubble water generating unit 15 stirs and mixes water supplied via the water supply line 12 and gas supplied via the gas supply line 13, turns the gas into microbubbles, and injects microbubble water from the nozzle. To do.

  In addition, in this embodiment, since it is advantageous to generate | occur | produce microbubble water by using the high pressure of the underground deep part, using the water supply line 12 and the gas supply line 13, microbubble water is supplied to the deep underground part. Although generated, a microbubble water generation plant may be installed on the ground surface, and microbubble water may be supplied from the ground surface. When microbubble water is generated on the ground surface, a pressure tank is required.

  The exhaust line 16 penetrates the shielding plug 11 from the lower part of the borehole 2 and reaches the exhaust recovery tank 17 installed on the ground surface.

  Note that the lower end of the exhaust line 16 must be located immediately below the shielding plug 11 and above the lower ends of the water supply line 12 and the gas supply line 13 (or the microbubble water generator 15).

  A valve 18 is provided in the exhaust line 16. A compressor 8 is provided on the exhaust upstream side (lower exhaust line 16 side) of the valve 18 of the exhaust line 16. The valve 18 is closed and the exhaust line 16 can be set to a high pressure by the compressor 8.

  The gas injection system 1 includes sensors 21 to 28.

  The pressure sensor 21 is provided on the output side of the pump 6 and detects the water supply pressure P1. The pressure sensor 22 is provided on the output side of the compressor 7 and detects the gas supply pressure P1.

  The pressure sensor 23 is provided upstream of the valve 18 in the exhaust line 16 and detects the exhaust pressure P2.

  The pressure sensor 24 is suspended and supported from the shielding plug 11 and detects the pore water pressure Pw at the lower portion of the boring hole 2.

  The flow sensor 25 is provided on the output side of the pump 6 and detects the water supply amount. The flow sensor 26 is provided on the output side of the compressor 7 and detects the gas supply amount. The flow sensor 27 is provided in the exhaust line 16 and detects the exhaust amount.

  The gas / water detection sensor 28 is provided at a position corresponding to the lower end of the exhaust line 16 and detects whether the position is a gas state or a liquid state. The sensor 28 is used for confirming whether there is a problem in pressure control described later.

  Detection signals from the sensors 21 to 28 are input to the control device 30. The control device 30 controls the pump 6, the compressor 7, the compressor 8, and the valve 18 based on these input signals (details of control will be described later).

~ Underground storage of carbon dioxide ~
The operation and control when the gas injection system is applied to the underground storage of carbon dioxide will be described.

  The supply water is adjusted to a pressure slightly higher than the groundwater pressure Pw by the pump 6. The supply gas is adjusted to a pressure slightly higher than the groundwater pressure by the compressor 7. The supply water pressure and the supply atmospheric pressure are substantially the same P1. Therefore, the supply pressure of the microbubble water is almost the same as the pump pressure.

  From the ground surface, high pressure water and high pressure carbon dioxide are supplied to the lower part of the borehole 2, microbubble water is generated by the microbubble water generator 15, and the microbubble water is injected into the aquifer.

  By forming microbubbles, solubility and stability are improved. The aquifer 4 extends in the horizontal direction, and the injected water diffuses along this. Thereby, carbon dioxide can be stably and efficiently stored underground.

  If the aquifer 4 is a rock containing carbonate, the weakly acidic injected water is naturally neutralized.

  However, not all of the supplied carbon dioxide is stored in the ground as microbubbles by the microbubble water generation unit 15, and large bubbles are not stored in the ground, such as rising up the borehole 2. Carbon (surplus gas) is generated.

  Large bubbles that have not become microbubbles rise up the exhaust line 16 and are collected in the exhaust collection tank 17. The carbon dioxide in the exhaust recovery tank 17 is again supplied into the ground.

  Thereby, the malfunction accompanying surplus gas can be prevented.

  At this time, the difference between the carbon dioxide supply amount and the carbon dioxide exhaust amount is the carbon dioxide storage amount.

~ Pressure control ~
When the surplus gas is recovered, if the pressure Pw of the groundwater is high, it becomes difficult for the groundwater to move up the exhaust line 16 and recover the surplus gas.

  Therefore, in the present embodiment, control is performed so that the pressure P2 of carbon dioxide recovered without being injected into the aquifer is lower than the pressure P1 injected into the aquifer and higher than the pore water pressure Pw of the aquifer. .

  FIG. 3 is a functional block diagram of the control device 30. Hereinafter, the pressure control will be described.

  First, the control of P1 will be described. By making the pressure of P1 higher than Pw (P1> Pw), microbubble water is injected into the aquifer. When the outputs of the pump 6 and the compressor 7 are increased, the injection pressure P1 is increased.

  Note that, as the pressure of P1 is made higher than Pw, the adjustment range of P2 control described later becomes wider and P2 control becomes easier.

  Next, the control of P2 will be described. When the pressure P2 of the surplus gas is lower than the pore water pressure Pw (P2 <Pw), the control of P2 is performed.

  When the valve 18 is closed, carbon dioxide is accumulated in the exhaust line 16, and the excess gas pressure P2 increases accordingly. As a result, the pressure P2 of the surplus gas becomes higher than the pore water pressure Pw.

  If a sufficient increase in P2 cannot be expected simply by closing the valve 18, the pressure is further increased by the compressor 8. Along with this, the pressure P2 of the surplus gas also increases. As a result, the pressure P2 of the surplus gas becomes higher than the pore water pressure Pw. Thereby, the rise of groundwater can be prevented.

  At this time, the pressure of the compressor 8 is adjusted, and the state where the pressure P2 of the surplus gas is lower than the injection pressure P1 (P1> P2) is maintained.

  If the water head difference between the position of the microbubble water generator 15 and the lower end of the exhaust pipe 16 is secured, it is easy to maintain P1> P2.

  Furthermore, control during gas recovery will be described. At the time of gas recovery, the valve 18 is opened. At this time, monitoring is performed so that the pressure P2 of the surplus gas is maintained higher than the pore water pressure Pw (P2> Pw). When the pressure P2 of the surplus gas becomes lower than the pore water pressure Pw (P2 <Pw), the valve 18 is closed again and P2 is controlled via the compressor 8 as necessary.

  The signal from the gas / water detection sensor 28 is used to check whether there is a problem in the pressure control. The control device 30 determines that there is a problem with the pressure control based on the water detection signal from the gas / water detection sensor 28 and outputs an alarm.

~ Remarks ~
The inventor of the present application conducted a confirmation test of the effect of carbon dioxide microbubbles. FIG. 4 is an explanatory diagram of the result of the confirmation test.

  The upper side of the figure shows the state of dissolution of carbon dioxide that has not been microbubbled. The lower side of the figure shows the state of dissolution of microbubbled carbon dioxide.

  A test machine for the gas injection system 1 was created, and carbon dioxide was injected into water at a normal temperature (about 20 ° C) and water pressure at a depth of 2.5 m for a predetermined speed and for a predetermined time. .

  On the upper side of the figure, about 2/3 of carbon dioxide was exhausted, and dissolved carbon dioxide was about 1/3. On the other hand, on the lower side of the figure, almost all carbon dioxide was dissolved, and it was confirmed that the solubility was dramatically improved by microbubble formation.

  On the other hand, attention was paid to the generation of surplus gas (approximately 1% or more in the figure) that cannot be ignored even when microbubbles are formed. Even when the test machine is applied to the actual storage of carbon dioxide, an excessive amount of surplus gas may diffuse into the atmosphere.

  The inventor has inferred the cause of excess gas generation. By the way, generally, fine bubbles having a diameter of 50 μm or less are called microbubbles, but there is no strict definition. When microbubbles are formed, it is difficult to uniformly control the size of bubbles, and relatively large bubbles are generated at a certain rate. Larger bubbles rise in water and return to gas.

  In addition, when trying to push a large bubble into the ground, water permeability is hindered due to gas resistance. As a result, the efficiency of underground storage may be reduced.

  The inventor has conceived the present invention, considering that it is more practical to allow generation of excess gas and recover the excess gas than to generate microbubbles so as not to generate excess gas.

  Further, the present invention was conceived by paying attention to the fact that water rises in the exhaust line when recovering surplus gas.

DESCRIPTION OF SYMBOLS 1 Gas injection system 2 Borehole 3 Impervious layer 4 Aquifer 11 Shield plug 12 Water supply line 13 Gas supply line 14 Compressor 15 Micro bubble water generation part 16 Exhaust line 17 Exhaust collection tank and 18 Valves 21-24 Pressure sensor 25-27 Flow sensor 28 Gas / water sensor 30 Controller 31 Packer expansion line 32 SUS wire

Claims (5)

The gas is micro-bubble water and injected into the aquifer below the impermeable layer,
A gas injection system that collects gas that has not been injected into the aquifer from the ground. A shielding plug that shields the borehole drilled from the impermeable layer to the lower aquifer,
A water supply line for supplying water to a space formed below by the shielding plug;
A gas supply line for supplying gas to a space formed below by the shielding plug;
A microbubble water generating unit for mixing and stirring the water and gas to generate microbubble water;
A gas injection system comprising: an exhaust line that recovers, from the ground, a gas that has not been injected among gases contained in microbubble water injected into the aquifer from the space. 3. The gas injection system according to claim 1, further comprising a control unit that controls a pressure of a gas recovered without being injected into the aquifer. The control means includes
The pressure of the gas recovered without being injected into the aquifer is controlled so as to be lower than the pressure injected into the aquifer and higher than the pore water pressure of the aquifer. The gas injection system described. Carbon dioxide is made into microbubbles, dissolved in water to make microbubble water,
Injecting the microbubble water into the aquifer below the impermeable layer,
A carbon dioxide underground storage method characterized in that carbon dioxide not injected into an aquifer is recovered from the ground.