JP2009293292A - Ground-gush suppressing system for natural gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a natural gas from being gushed to a ground surface by separably taking out the natural gas dissolved in a brine and reducing the brine separated toward the upper layer to form a seal layer. <P>SOLUTION: A ground-gush suppressing system comprises: a production well 2 which extends to a deep aquifer 7 containing the brine in which the natural gas is dissolved which is positioned above the ground layer for production and which is buried in the ground; a gas-water separator 16 for separating the natural gas from the brine pumped up by the production well 2, and a reduction well 3 for reducing the reduced water from which the natural gas is separated by the gas-water separator 16 to the deep aquifer 7. The production well 2 is 150-500 m deep, and the reduction well 3 is shallower than the production well 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a natural gas ground seepage suppression system for suppressing natural gas existing underground.

  Natural gas is a flammable gas produced in nature mainly composed of hydrocarbons, and is attracting attention as a new energy source. In particular, this natural gas does not generate sulfur oxides and dust that pollute the atmosphere, and there is little generation of nitrogen oxides, which have problems with acid rain and the human body. In particular, the amount of carbon dioxide generated by combustion, which is a cause of global warming, is much smaller than other fossil fuels such as coal and oil. For this reason, natural gas can be said to be a more effective underground resource from the viewpoint of preventing environmental pollution.

  Natural gas produced in Japan includes water-soluble natural gas. This water-soluble natural gas is a natural gas produced together with groundwater (brine) from an aquifer as a water-soluble natural gas deposit. In the water-soluble natural gas deposit, natural gas is dissolved in brine by high pressure, but when this is pumped to the ground, natural gas and brine are separated.

For this reason, in the conventional water-soluble natural gas collection system, as shown in Patent Documents 1 and 2, for example, the brine contained in the aquifer is pumped to the ground, and the natural gas is separated and collected from this. It was going back to the water layer.
JP-A-6-146257 Japanese Patent Laid-Open No. 6-50080

  By the way, in a water-soluble natural gas deposit, natural gas often springs from the ground surface. Such gas that flows out is also called upper gas, and rises from the underground gas reservoir to the surface of the earth through faults in the formation and the surrounding fissures. Since the main component of natural gas is hydrocarbons, it is a greenhouse gas in addition to cases where natural gas springed from the ground has an adverse effect on agricultural products, or enters and accumulates in buildings to cause fires or explosions. Therefore, it is necessary to suppress the release to the atmosphere. For this reason, in areas where such water-soluble natural gas exists underground, it is necessary to prevent natural gas from flowing out to the ground surface. There was a problem that no consideration was given.

  Therefore, the present invention has been devised in view of the above-mentioned problems, and the object of the present invention is natural gas upwelling that can prevent economic damage due to natural gas outflow to the ground surface. It is to provide a suppression system.

  In order to solve the above-mentioned problem, the invention according to claim 1 of the present application is a pumping well that is extended to an aquifer containing brine containing dissolved natural gas and buried in the ground, and is pumped by the pumping well. A gas separation means for separating natural gas from the culm water, and a reduction well for reducing the reduced water from which natural gas has been separated by the gas separation means to the aquifer, wherein the pumping well has a depth of 150 to 500 m. And the said reduction | restoration well is comprised shallower than the said pumping well, It is characterized by the above-mentioned.

  The invention according to claim 2 of the present application is characterized in that, in the invention according to claim 1, the reducing well is injected into a formation shallower than the pumping well.

  The invention according to claim 3 of the present application is the invention according to claim 1 or 2, wherein the reducing well forms a sealing layer with the reducing water immediately above the upper end of the strainer casing part of the pumping well. It is characterized by suppressing the rise of natural gas from the underground through a sealing layer.

  In the present invention having the above-described configuration, natural gas contained in brine can be separated and removed. Moreover, in this invention which consists of an above-described structure, it becomes possible to form the sealing layer by reduced water in the ground. As a result, it is possible to suppress the natural gas generated from the fault in the formation and the surrounding cracks from the underground gas reservoir to the ground by this sealing layer. In particular, since the main component of natural gas is hydrocarbons, there are adverse effects on agricultural products caused by natural gas that has sprung from the ground surface, and there are cases of fire and explosion accidents in buildings. Since it can be blocked by the sealing layer, it is possible to remove such an adverse effect.

  Hereinafter, as a best mode for carrying out the present invention, a separation and collection system 1 capable of separating and collecting natural gas dissolved in brine will be described in detail with reference to the drawings.

  FIG. 1 shows an overall view of a separation and sampling system 1 to which the present invention is applied. This separation and sampling system 1 is a ground in which a shallow aquifer 6 and a deep aquifer 7 including groundwater (brine) in which natural gas is dissolved, and a natural gas reservoir 8 below the ground aquifer are formed in the ground. Built in. The shallow aquifer 6 and the deep aquifer 7 are located in the uppermost layer of a so-called water-soluble natural gas deposit. The reservoir for gas sampling is at a depth where the brine is at a salinity level almost the same as seawater. The shallow aquifer 6 is formed at a shallower depth than the deep aquifer 7. The natural gas contained in the brine filled in the shallow aquifer 6 and the deep aquifer 7 is mainly composed of methane, but may contain a very small amount of ethane or propane. The natural gas reservoir 8 stores natural gas to be operated.

  Moreover, as shown in FIG. 1, the salinity concentration is lowest in the shallow aquifer 6. That is, the shallow aquifer 6 is composed of almost fresh water. On the other hand, in the deep aquifer 7, the salt concentration gradually increases as the depth increases. When the depth becomes deeper than that of the deep aquifer 7, the salinity concentration is approximately the same as that of seawater, and the reservoir for collection is obtained.

  The depth of the shallow aquifer 6 is 150 m from the ground surface, and the depth of the deep aquifer 7 is 150 m or less. However, the depths of the shallow aquifer 6 and the deep aquifer 7 vary depending on the excavation area. In particular, the depth of the deep aquifer 7 is often 250 to 500 m.

  The separation / collection system 1 includes a pumping well 2 and a reduction well 3. The pumping well 2 is buried in the ground with its lower end 2a extending to the deep aquifer 6. Further, the reduction well 3 reduces the reduced water from which natural gas has been separated on the ground to the deep aquifer 6. By constructing the pumping well 2 and the reduction well 3 in the vicinity of each other and operating them simultaneously, the total amount of brine contained in each of the shallow aquifer 6 and the deep aquifer 7 can be made unchanged. It becomes possible. As a result, ground subsidence can be reduced.

  A press-fit pipe 11 is connected to the pumping well 2. The brine is pumped from the pumping well 2 through the press-fitting pipe 11 based on the power of the compressor 12 that plays a role as a so-called pump. Valves 13 and 14 are arranged at the upper end of the pumping well 2 and the tip of the branch pipe, respectively, so that the flow rate can be adjusted. Further, the brine pumped up by the pumping well 2 is sent to the gas-water separator 16. The gas-water separator 16 includes a so-called gas-liquid separation tank or the like, and the separated gas is extracted through the gas pipe 20. The flow rate adjustment to the gas pipe 20 is executed via the valve 15. The separated brine is sent to the reduction well 3, and this flow rate is controlled by valves 18 and 19. Then, the brine from which the natural gas has been separated is sent to the underground through the reduction well 3.

  Strainer casings 23 and 24 are formed at the lower part of the pumping well 2 and the lower part of the reducing well 3, respectively. The strainer casings 23 and 24 are pipes configured by a large number of holes that penetrate from the outside to the inside. Brine water flows in and out through the strainer casings 23 and 24. Further, brine may flow in and out from the bottom of the pipe without passing through the strainer casings 23 and 24.

  In the separation and sampling system 1 having such a configuration, the pumping well 2 is configured with a depth of 150 to 500 m. This corresponds to the depth of the deep aquifer 7. The reduction well 3 is configured to be shallower than the pumping well 2. That is, the lower end 3 a of the reduction well 3 is buried so as to be shallower than the lower end 2 a of the pumping well 2.

  The reason why the pumping well 2 is configured to have a depth of 150 to 500 m is that a large amount of hydrocarbons are contained in the brackish water staying at the depth, and this is pumped up through the pumping well 2 for gas-water separation. Separation of hydrocarbons in the vessel 16 makes it possible to separate and extract natural gas with a higher yield.

  Moreover, as shown in FIG. 1, the sealing layer 31 by reduced water will be formed in the ground by the reduced water reduced from the reduction well 3 comprised shallower than the pumping well 2. As shown in FIG. The sealing layer 31 made of reduced water is a layer mainly containing reduced water with a high density, and has a higher water pressure than other layers.

  By forming the sealing layer 31 based on such reduced water, the following effects can be obtained.

  As shown in FIG. 2, the natural gas 35 rises from the underground gas reservoir to the fault in the formation and the surrounding cracks to the ground surface, in addition to being contained in the brine. The rising natural gas 35 is prevented from rising to the ground surface by the sealing layer 31. In particular, since the sealing layer 31 has a higher water pressure than the other layers, it is possible to effectively block the gas such as the natural gas 35 from rising. In particular, since the main component of natural gas is hydrocarbons, the natural gas boiled off the ground surface may adversely affect crops. In the present invention, such leaking natural gas is blocked by the sealing layer 31. Therefore, it is possible to remove such harmful effects.

  The reduction well 3 is preferably formed at a depth immediately above the pumping well 2. That is, it is desirable that the lower end 3 a of the reduction well 3 is configured above the lower end 3 b of the pumping well 2. The reason for this is to suppress the liberation and rise of gas by increasing the pressure of the upper reservoir.

1 is an overall view of a separation and collection system to which the present invention is applied. It is a figure for demonstrating the effect by forming the sealing layer by reduced water in the ground.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Separation and extraction system 2 Pumping well 3 Reduction well 6 Shallow aquifer 7 Deep aquifer 8 Natural gas reservoir 11 Press-in pipe 12 Compressors 13, 14, 15, 18, 19 Valve 16 Gas-water separator 23, 24 Strainer casing 31 Sealing layer 35 Natural gas

Claims (3)

A pumping well that is extended to an aquifer containing brine containing dissolved natural gas and buried underground;
Gas separating means for separating natural gas from the brine pumped up by the pumping well;
A reduction well for reducing the reduced water from which natural gas has been separated by the gas separation means to the aquifer,
The pumping well is 150 to 500 m deep,
The above-mentioned reducing well is configured to be shallower than the above-mentioned pumping well, and is a natural gas ground seepage suppression system. The above-described reduction well is injected into a formation shallower than the above-mentioned pumping well. The reducing well is characterized in that a sealing layer is formed by the reducing water immediately above the upper end of the strainer casing part of the pumping well, and the natural gas is prevented from floating from the underground through the formed sealing layer. The natural gas ground seepage suppression system according to claim 1 or 2.

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