Geothermal power generation system

Abstract

This geothermal power generation system, which generates power using thermal energy in a geothermal zone, comprises: at least two wells; a power generation facility that extracts a geothermal fluid generated in the geothermal zone from any one of the at least two wells and generates power using thermal energy contained in the geothermal fluid; and a geothermal heat exchanger that performs heat exchange on the fluid circulating in a flow path configured as a closed loop-type flow path in the geothermal zone. The geothermal heat exchanger is provided at any one point between the at least two wells.

Description

Geothermal Power Generation System

[0001] The present invention relates to a geothermal power generation system.

[0002] Geothermal power generation, which uses geothermal steam from geothermal zones and geothermal heat from hot dry rocks, uses the Earth's high-temperature magma layers as a heat source and is a means of generating electricity without consuming fuel or emitting greenhouse gases during the power generation process. For this reason, geothermal power generation is attracting attention as a renewable energy source from the perspectives of energy self-sufficiency and global warming countermeasures.

[0003] As a related technology for geothermal power generation, Patent Document 1 discloses a flash geothermal power generation system that generates electricity by drilling a production well in a geothermal field and utilizing thermal energy contained in geothermal fluids such as high-temperature, high-pressure hot water and steam obtained from a geothermal reservoir. Patent Document 2 also discloses a closed-loop geothermal power generation system that generates electricity by recovering underground heat by installing a closed-loop circulation flow path consisting of a double pipe with an inner and outer pipe underground and circulating fluid such as water from above ground. Patent Document 3 also discloses a geothermal power generation system that achieves more efficient geothermal power generation by providing production wells for other geothermal power generation facilities around a closed-loop geothermal well for heat exchange liquid.

[0004] JP 2022-037982 A JP 2014-202149 A JP 2016-164395 A

[0005] For geothermal power generation systems, it is desirable to recover more thermal energy from the geothermal zone to increase the amount of power generated.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to improve the amount of heat recovered from geothermal zones and increase the amount of power generation.

[0007] One aspect of the present invention is a geothermal power generation system that generates electricity using thermal energy contained in a geothermal zone, comprising at least two or more boreholes, a power generation facility that extracts geothermal fluid produced in the geothermal zone from one of the two or more boreholes and generates electricity using the thermal energy contained in the geothermal fluid, and a geothermal heat exchanger that exchanges heat in the geothermal zone with a fluid circulating in a closed-loop flow path, the geothermal heat exchanger being located somewhere between the two or more boreholes.

[0008] According to one aspect of the present invention, by installing a geothermal heat exchanger having a closed-loop flow path between two or more boreholes, the amount of heat recovered from the geothermal zone can be improved, thereby increasing the amount of power generation.

[0009] Another aspect of the present invention is a geothermal power generation method that generates electricity by utilizing thermal energy in a geothermal zone, in which geothermal fluid produced in the geothermal zone is extracted from one of at least two or more boreholes and the thermal energy contained in the geothermal fluid is used to generate electricity, and a geothermal heat exchanger is provided at a point between the two or more boreholes to exchange heat in the geothermal zone with fluid circulating in a closed-loop flow path, and electricity is generated by utilizing the thermal energy contained in the heated fluid obtained by heat exchange in the geothermal heat exchanger.

[0010] According to another aspect of the present invention, by installing a geothermal heat exchanger having a closed-loop flow path between two or more boreholes, the amount of heat recovered from the geothermal zone by the geothermal heat exchanger can be improved, thereby increasing the amount of power generation.

[0011] FIG. 1 is a block diagram showing a schematic configuration of the entire geothermal power generation system according to a first embodiment of the present invention. FIG. 2 is an explanatory diagram showing a schematic configuration of a main part of the geothermal power generation system according to the first embodiment of the present invention. FIG. 3 is an explanatory diagram showing an example of the arrangement of temperature sensors provided in a geothermal heat exchanger of the geothermal power generation system according to the first embodiment of the present invention. (A) to (D) are explanatory diagrams showing an example of the arrangement of geothermal heat exchangers in the geothermal power generation system according to the first embodiment of the present invention. FIG. 4 is an explanatory diagram showing another example of the arrangement of geothermal heat exchangers in the geothermal power generation system according to the first embodiment of the present invention. FIG. 5 is a flow chart showing an example of the heat exchange operation flow of the geothermal heat exchanger in the geothermal power generation system according to the first embodiment of the present invention. FIG. 6 is a block diagram showing the functional configuration of a modified example of the geothermal power generation system according to the first embodiment of the present invention. FIG. 7 is an explanatory diagram showing a schematic configuration of main parts of another modified example of the geothermal power generation system according to the first embodiment of the present invention. FIG. 8 is an explanatory diagram showing a modified example of a well in which a geothermal heat exchanger is installed in the geothermal power generation system according to the first embodiment of the present invention. FIG. 9 is a block diagram showing a schematic configuration of the entire geothermal power generation system according to a second embodiment of the present invention. FIG. 10 is an explanatory diagram showing a schematic configuration of main parts of the geothermal power generation system according to the second embodiment of the present invention.

[0012] A preferred embodiment of the present invention will be described in detail below. Note that the embodiment described below does not unduly limit the content of the present invention as defined in the claims, and not all of the configurations described in the embodiment are necessarily essential as means for solving the problems of the present invention.

[0013] In the following description, terms indicating directions such as "upper," "lower," "left," and "right" are used for convenience of explanation and do not limit the method or manner of use. Terms such as "first" and "nth" (n is an integer) following "first" in this specification and claims are used as identifying terms to distinguish different elements and do not indicate a particular order or superiority or inferiority.

[0014] [First embodiment] The schematic configuration of a geothermal power generation system according to one embodiment of the present invention will be described with reference to the drawings. Fig. 1 is an explanatory diagram showing the schematic configuration of the entire geothermal power generation system according to the first embodiment of the present invention, and Fig. 2 is a block diagram showing the schematic configuration of a main part of the geothermal power generation system according to the first embodiment of the present invention.

[0015] The geothermal power generation system 100 of this embodiment generates electricity using thermal energy contained in a geothermal reservoir GR1 or the like in a geothermal field. As shown in FIG. 1 , the system includes a production well 101, a reinjection well 102, a first geothermal power generation facility 110, a second geothermal power generation facility 120, and a geothermal heat exchanger 130. As shown in FIG. 2 , the production well 101 is a borehole that extracts geothermal fluids such as high-temperature, high-pressure hot water and steam that are stored in the geothermal reservoir GR1 in the geothermal field. The reinjection well 102 is a borehole that uses the geothermal fluid extracted from the production well 101 for power generation in the first geothermal power generation facility 110 and then returns reinjection water, which contains condensed water from the steam after power generation and other water, underground. In other words, the reinjection well 102 is a borehole that returns the reinjection water discharged after heat exchange with the geothermal fluid in the first geothermal power generation facility 110 to the ground.

[0016] The first geothermal power generation facility 110 is a facility for taking in geothermal water containing high-temperature steam of approximately 100 to 400°C as a geothermal fluid and generating electricity from this geothermal water, and as shown in Figure 1, it mainly comprises a first flasher 111, a second flasher 112, a turbine 113, a generator 114, a condenser 115, a high-pressure circulation pump 116, etc.

[0017] The first geothermal power generation facility 110 takes in geothermal water heated by geothermal energy and separates it into steam using a first flasher 111, which is a steam-water separator. The separated steam is sent to a turbine 113. Optionally, the water is further separated into steam and water using a second flasher 112 to obtain secondary steam, which is also sent to the turbine 113, and the rotation of the turbine 113 generates electricity in a generator 114. The steam consumed by the turbine 113 is condensed in a condenser 115, and the condensed geothermal water is either discharged as a cooling water or cooled and used as cooling water for the condenser 115, or is used for injecting into the geothermal zone via an injecting well 102. The hot water obtained by steam-water separation using the second flasher 112 is sent to the injecting well 102 by a high-pressure circulation pump 116.

[0018] The first geothermal power generation facility 110 is not limited to the above-described configuration, and other components may be replaced with other components or additional components may be installed. In this embodiment, the first geothermal power generation facility 110 is illustrated as a double-flash system as shown in Figure 1 , but it may also be applied to a single-flash system in which hot water separated from steam in the first flasher 111 is directly returned to the geothermal zone from the return well 102.

[0019] Furthermore, as described above, the geothermal power generation system 100 employs a flash power generation geothermal power generation facility as the first geothermal power generation facility 110, which generates electricity using high-temperature, high-pressure steam contained in the geothermal fluid extracted from the production well 101. The geothermal power generation system 100 of this embodiment is not limited to a flash power generation geothermal power generation facility as the first geothermal power generation facility 110, but can also be applied to a binary power generation facility that generates electricity using steam obtained by boiling a medium with a boiling point lower than that of water using the geothermal fluid extracted from the production well 101.

[0020] The second geothermal power generation facility 120 is a binary geothermal power generation facility that uses a closed-loop geothermal heat exchanger 130, which exchanges heat in a geothermal zone with a heat exchange fluid circulating in a closed-loop flow path. Unlike the first geothermal power generation facility 110, the second geothermal power generation facility 120 does not need to discharge the heat exchange fluid that receives heat from underground into a geothermal zone or to extract hot water from the geothermal zone. The heat exchange fluid used in the geothermal heat exchanger 130 preferably has a boiling point of 150°C or less at atmospheric pressure, such as, but not limited to, water or water containing dissolved ammonia.

[0021] The geothermal heat exchanger 130 includes an outer pipe 131 buried underground facing the geothermal zone and an inner pipe 132 disposed inside the outer pipe 131. As shown in FIG. 2 , the geothermal heat exchanger 130 has a double-pipe structure with no opening in the geothermal zone. The space between the outer pipe 131 and the inner pipe 132 forms a descending flow path 131a for descending the heat exchange fluid, and the interior of the inner pipe 132 forms an ascending flow path 132a for ascending the heat exchange fluid. The inner pipe 132 has an open lower end below the outer pipe 131. At the lower end, the ascending flow path 132a in the inner region inside the inner pipe 132 and the descending flow path 131a in the outer region between the inner pipe 132 and the outer pipe 131 are connected. This allows the heat exchange fluid descending through the descending flow path 131a in the outer region to be transported to the ascending flow path 132a in the inner region and ascended.

[0022] The geothermal heat exchanger 130 has the double-pipe structure described above, thereby forming a closed-loop flow path, in which a fluid serving as a heat exchange medium is pressurized into the descending flow path 131a between the outer pipe and the inner pipe, and the fluid is heated in the geothermal zone as it flows down the descending flow path 131a, and the resulting heated fluid is transported while rising up the ascending flow path 132a inside the inner pipe 132. In other words, the geothermal heat exchanger 130 has the function of transporting the heat exchange fluid to the geothermal zone, and then transporting the heat exchange fluid that has been heat exchanged and heated in the geothermal zone to the ground as a heated fluid.

[0023] As shown in FIG. 3, the geothermal heat exchanger 130 has a temperature sensor 133 (133) on at least one of the outer surface of the outer pipe 131 and the outer surface of the inner pipe 132, which is capable of measuring the underground temperature. ｉｎ , 133 ｏｕｔ ) can be provided. Operation of the geothermal heat exchanger 130 requires technology for monitoring the recovery of the formation temperature in real time, and in geothermal fields, the temperature of the formation can become as high as 250 to 300°C or higher. For this reason, in this embodiment, it is preferable to use a fiber sensor that can withstand high temperatures as the temperature sensor 133 attached to the geothermal heat exchanger 130.

[0024] A temperature sensor 133 is attached to the outer surface of the outer pipe 131 of the geothermal heat exchanger 130. ｏｕｔ By permanently installing the temperature sensor 133, it becomes possible to measure the temperature change during and after the circulation of the heat exchange fluid in real time. ｉｎ When the temperature of the geological formation is monitored by installing a temperature sensor 133 on the outer periphery of the inner pipe 132, it is preferable to construct the outer pipe 131 from a material with high thermal conductivity such as copper, since this makes it possible to monitor the temperature of the geological formation even if it is not on the back side of the outer pipe 131. Details of the operation control of the geological heat exchanger 130 based on the measurement results of the temperature sensor 133 of the geological heat exchanger 130 will be described later.

[0025] In this embodiment, a double-pipe structure is used as the closed-loop geothermal heat exchanger 130, but other configurations may be used as long as the heat exchange fluid is circulated within a closed-loop flow path formed underground and heat is exchanged in the geothermal heat zone. For example, a closed-loop geothermal heat exchanger may be constructed by digging a mesh-like loop connecting the surface and the underground several thousand meters, and circulating water through the loop to extract underground heat.

[0026] 1 and 2, the second geothermal power generation facility 120 includes an evaporator 121, a tank 122, a turbine 123, a generator 124, a condenser 125, a high-pressure circulation pump 126, etc. In the second geothermal power generation facility 120 having these devices, a heat exchange medium circulating in a geothermal heat exchanger 130 is heated by geothermal heat to produce a heat exchange medium, which is then heated and evaporated by heat exchange in the evaporator 121, which functions as a steam generator. The heat exchange medium heated and evaporated by heat exchange in the evaporator 121 is then sent to the turbine 123, and electricity is generated by the generator 124 due to the rotation of the turbine 123.

[0027] The steam consumed in the turbine 123 is condensed in the condenser 125, and the condensed heat exchange medium is used as cooling water for the condenser 125 after being cooled or is returned to the evaporator 121 where it is boiled under reduced pressure and used to generate high-temperature, high-pressure steam. After being used for heat exchange in the evaporator 121, the heat exchange medium is temporarily stored in a tank 122 and then sent to the geothermal heat exchanger 130 by a high-pressure circulation pump 126. The second geothermal power generation facility 120 is not limited to the configuration described above, and other components may be replaced with other components or additional components may be provided.

[0028] In the geothermal power generation system 100 of this embodiment, the geothermal heat exchanger 130 is provided at a location between the production well 101 and the reinjection well 102. Specifically, as shown in FIG. 4A , the geothermal heat exchanger 130 is provided on a line L1 connecting the production well 101 and the reinjection well 102. The location of the geothermal heat exchanger 130 is not limited to being provided on the line L1 connecting the production well 101 and the reinjection well 102. As shown in FIG. 4B , the geothermal heat exchanger 130 may be provided near the line L1 connecting the production well 101 and the reinjection well 102. For example, if the distance between the production well 101 and the reinjection well 102 is D (= the length of the line L1), and the shortest distance between the line L1 and the geothermal heat exchanger 130 (the length of a perpendicular line from the geothermal heat exchanger 130 to the line L1) is d, it is preferable that d<D. Note that d may be the length of a perpendicular line from the center of the geothermal heat exchanger 130 to the line L1.

[0029] Furthermore, the number of geothermal exchangers 130 installed on the line L1 connecting the production well 101 and the reinjection well 102 is not limited to one, and may be two or more. For example, as shown in FIG. 4(C), two geothermal exchangers 130 may be installed on the line L1 connecting the production well 101 and the reinjection well 102. As shown in FIG. 4(D), two geothermal exchangers 130 may be installed near the line L1 connecting the production well 101 and the reinjection well 102.

[0030] Here, the two geothermal heat exchangers 130 are arranged symmetrically with respect to the line L1 (line symmetry). When providing two geothermal heat exchangers 130 in this manner, the arrangement may be the same as described above. For example, one geothermal heat exchanger 130 may be provided within a radius r1 from the center of the production well 101, and the other geothermal heat exchanger 130 may be provided within a radius r2 from the center of the reinjection well 102 (see FIG. 4(D)). The geothermal heat exchangers 130 must be arranged within two perpendicular lines drawn through the centers of the production well 101 and the reinjection well 102 relative to the line L1.

[0031] Next, referring to FIG. 5 , an example of the arrangement of the geothermal exchanger 130 in a location where multiple production wells 101a-101d and multiple reinjection wells 102a-102d exist in one area will be described. The production wells 101a-101d and the reinjection wells 102a-102d are paired with each other. Geothermal exchangers 130a-130e are arranged between each pair. The geothermal exchanger 130a is arranged between the production well 101a and the reinjection well 102a. Two geothermal exchangers 130b and 130c are arranged between the production well 101b and the reinjection well 102b. Similarly, the geothermal exchanger 130d is arranged between the production well 101c and the reinjection well 102c, and the geothermal exchanger 130e is arranged between the production well 101d and the reinjection well 102d.

[0032] Here, the geothermal exchanger 130d is positioned between the production well 101c and the reinjection well 102c, but can also be seen as positioned between the production well 101d and the reinjection well 102d. In this manner, for example, one geothermal exchanger 130d may be shared by multiple production wells 101c, 101d and reinjection wells 102c, 102d. The number of shared geothermal exchangers is not limited to one, and may be multiple. For example, two geothermal exchangers 130d, 130e may be shared by multiple production wells 101c, 101d and reinjection wells 102c, 102d. Also, FIG. 5 shows an example in which the production wells 101a-101d and the reinjection wells 102a-102d are paired with each other. However, for example, there are cases where one reinjection well is provided for multiple production wells, so this is not limited to embodiments in which production wells and reinjection wells are necessarily paired, and can also be applied to embodiments in which the number of production wells and reinjection wells is different.

[0033] In particular, in the geothermal power generation system 100 of this embodiment, the geothermal heat exchanger 130 is applied when installed at a location between the production well 101 and the reinjection well 102 of an existing first geothermal power generation facility 110 (hereinafter also referred to as the existing geothermal power generation facility 110). When the existing geothermal power generation facility 110 is constructed, a geological survey of the strata at the installation site is conducted in advance, and the geothermal reservoir GR1 in the geothermal zone is monitored even during operation of the geothermal power generation facility, resulting in the accumulation of strata data around the existing geothermal power generation facility 110. For this reason, in this embodiment, the geothermal heat exchanger 130 is installed at a location between the production well 101 and the reinjection well 102 based on the accumulated analysis results of the strata data around the existing geothermal power generation facility 110.

[0034] Next, the operational flow of heat exchange in the geothermal heat exchanger of the geothermal power generation system according to the first embodiment of the present invention will be described with reference to the drawings. Figure 6 is a flow chart showing an example of the operational flow of heat exchange in the geothermal heat exchanger of the geothermal power generation system according to the first embodiment of the present invention.

[0035] When the geothermal heat exchanger 130 to which the closed-loop system is applied is operated, the temperature of the formation near the well where the geothermal heat exchanger 130 is installed drops due to fluid circulation from above ground. Therefore, if the temperature of the formation drops below a predetermined threshold, it may become impossible to sufficiently recover thermal energy. For this reason, as described above, in this embodiment, the geothermal heat exchanger 130 is provided with a temperature sensor 133 (133) on at least one of the outer surface side of the outer pipe 131 and the outer surface side of the inner pipe 132, which is capable of measuring the underground temperature. ｏｕｔ , 133 ｉｎ ) is provided, and the underground temperature is detected by the temperature measured by the temperature sensor 133 (step S1).

[0036] In this embodiment, the temperature of the underground formation near the borehole where the geothermal exchanger 130 is installed is monitored, but the temperature measurement is not limited to underground monitoring. That is, the temperature on the ground may be measured as the temperature of the formation near the borehole where the geothermal exchanger 130 is installed, and the temperature of the formation may be monitored based on the measured temperature.

[0037] When the temperature sensor 133 detects that the outlet temperature of the circulating fluid has fallen below a threshold value (e.g., 200°C or less) that is the minimum value required for heat recovery in the geothermal exchanger 130 (step S2), heat exchange by the geothermal exchanger 130 is stopped (step S3). To stop the heat exchange by the geothermal exchanger 130, for example, the operation of the high-pressure circulation pump 126 is turned off to stop the heat exchange operation by the geothermal exchanger 130. In this way, when the supply of fluid from the tank 122 is stopped and the circulation of the fluid is stopped, the temperature of the formation near the well of the geothermal exchanger 130 is reheated by a heat source such as a magma chamber deep in the formation and is restored.

[0038] Thereafter, when the temperature sensor 133 detects that the underground temperature has reached or exceeded a threshold value (e.g., 300°C or higher) that is the minimum value required for the geothermal exchanger 130 to resume heat recovery (step S4), heat exchange by the geothermal exchanger 130 is resumed (step S5). To resume heat exchange by the geothermal exchanger 130, for example, the high-pressure circulation pump 126 is turned on to resume the heat exchange operation by the geothermal exchanger 130. Then, by resetting and repeating steps S1 to S5, the temperature sensor 133 monitors the formation temperature near the well where the geothermal exchanger 130 is installed in real time, and switching control is performed to restart or stop the heat exchange operation by the geothermal exchanger 130. When multiple geothermal exchangers 130 are installed, the heat exchange operation is similarly switched on and off.

[0039] As a countermeasure against a drop in the formation temperature, other measures are possible besides stopping the fluid circulation by the high-pressure circulation pump 126, stopping the heat exchange by the geothermal heat exchanger 130, and waiting for the formation temperature to recover, as described above. For example, as shown in FIG. 7 , when the temperature sensor 133 detects that the underground temperature has fallen below a threshold value, which is the minimum value required for heat recovery by the geothermal heat exchanger 130 (step S10), hot water (a fluid having a predetermined temperature or higher), such as wastewater from a flash-type geothermal power generation system, may be introduced into the descending flow path 131a of the geothermal heat exchanger 130 and circulated (step S11) to promote the recovery of the formation temperature. By introducing and circulating the hot water (step S11), once the temperature measured by the temperature sensor 30 has recovered to a desired threshold value or higher (step S12), the introduction of hot water is stopped and heat exchange is resumed (step S13).

[0040] In this manner, in this embodiment, when controlling the operation of heat exchange by the closed-loop geothermal heat exchanger 130, the temperature sensor 133 monitors the formation temperature near the well of the geothermal heat exchanger 130 to control the on / off of heat exchange by the geothermal heat exchanger 130. However, if there is only one geothermal heat exchanger 130 installed between the production well 101 and the reinjection well 102, there will be periods when heat recovery is not performed.

[0041] Therefore, in the geothermal power generation system 100 of this embodiment, multiple geothermal heat exchangers 130 may be installed between the production well 101 and the reinjection well 102, and the temperature of the formation near the well of each heat exchanger 130 may be monitored by a temperature sensor 133, and the heat exchange may be controlled on and off for each geothermal heat exchanger 130.

[0042] Next, a case where the geothermal power generation system 100 of this embodiment has multiple geothermal heat exchangers 130 will be described with reference to the drawings. Fig. 8 is a block diagram showing the schematic configuration of a modified geothermal power generation system according to the first embodiment of the present invention. Note that Fig. 8 focuses only on the sensors and controllers provided in each heat exchanger in the geothermal power generation system, and describes in detail the functions of each sensor in each heat exchanger and the controller of the geothermal power generation system. Fig. 8 also describes a case where there are three geothermal heat exchangers.

[0043] In the geothermal power generation system 100 of this embodiment, a control unit 140, which serves as a system management computer, is connected to each of the heat exchangers 130a, 130b, and 130c via a network 150. Note that Fig. 8 shows, as an example of the geothermal power generation system 100, a distributed control system (hereinafter also referred to as "DCS") in which the control devices of the devices constituting the system are connected via a network to communicate with and manage each other. In this embodiment, the geothermal power generation system 100 is not limited to a DCS, and other control systems such as a programmable logic controller (PLC) may also be used.

[0044] The control unit 140 incorporates a computer and a microprocessor in a control device called a controller and is configured to perform process control using these functions. As shown in Figure 8, the control unit 140 has a receiving unit 141, a determining unit 142, and a transmitting unit 143.

[0045] The receiving unit 141 has a function of controlling the reception of detection data from the sensors 133a, 133b, 133c, 134a, 134b, 134c, 135a, 135b, and 135c of the heat exchangers 130a, 130b, and 130c.

[0046] The determination unit 142 has a function of performing determination operations required when executing various operations of the geothermal power generation system 100. For example, the determination unit 142 has a function of determining whether various data is being transmitted and received to and from the heat exchangers 130a, 130b, and 130c. In this embodiment, the determination unit 142 has a function of determining whether detection data from the sensors 133a, 133b, 133c, 134a, 134b, 134c, 135a, 135b, and 135c of the heat exchangers 130a, 130b, and 130c reaches a predetermined threshold, and a function of controlling various operations of the heat exchangers 130a, 130b, and 130c based on this detection data.

[0047] The transmitting unit 143 has a function of controlling the transmission of various data to each of the heat exchangers 130 a, 130 b, and 130 c. The transmitting unit 143 has a function of transmitting various operation control commands to each of the heat exchangers 130 a, 130 b, and 130 c based on the determination result of the determining unit 142.

[0048] Each heat exchanger 130a, 130b, 130c is equipped with a temperature sensor 133a, 133b, 133c, an acoustic sensor 134a, 134b, 134c, and a strain sensor 135a, 135b, 135c. As described above, the temperature sensors 133a, 133b, 133c function to measure the temperature of the formation near the wells of each heat exchanger 130a, 130b, 130c. The acoustic sensors 134a, 134b, 134c measure and monitor the behavior of the formation near the wells of each heat exchanger 130a, 130b, 130c, such as friction, collision, and stress waves generated by turbulence and cavitation of geothermal fluid, as well as measuring minute vibrations. The strain sensors 135a, 135b, and 135c have the function of measuring changes in dynamic and quasi-static surface strains and strains in the formations near the wells of the geothermal exchangers 130a, 130b, and 130c.

[0049] Since each component of the geothermal power generation system 100 has the functional configuration described above, it is able to receive detection data from the temperature sensors 133a, 133b, 133c, acoustic sensors 134a, 134b, 134c, and strain sensors 135a, 135b, 135c received from each heat exchanger 130a, 130b, 130c, and to perform various operational controls, including heat exchange, of each heat exchanger 130a, 130b, 130c, based on the detection data.

[0050] In this embodiment, the formation temperatures near the wells of each heat exchanger 130a, 130b, 130c are monitored by temperature sensors 133a, 133b, 133c, and the heat exchange operation of each of the geothermal heat exchangers 130a, 130b, 130c is switched to generate power through closed-loop heat exchange in the geothermal power generation system 100. Therefore, even if the detection data of one of the geothermal heat exchangers 130a falls below a threshold and the heat exchange operation is stopped, as long as the detection data of the other geothermal heat exchangers 130b, 130c are above the threshold, the heat exchange operation can be maintained, thereby enabling continuous heat recovery and power generation from the perspective of the geothermal power generation system 100 as a whole.

[0051] Furthermore, in this embodiment, by reflecting data actually acquired from the temperature sensor 133 in the temperature simulation model near the well, it becomes possible to perform a more accurate simulation. As a result, the behavior of the strata near the well of each heat exchanger 130 can be predicted, enabling optimized operation of each heat exchanger 130. For example, by simulating future production and power generation amounts while monitoring the temperature data acquired by the temperature sensor 133 in real time, it becomes possible to optimize the on / off switching of the heat exchange fluid circulation and the production method of the multiple geothermal heat exchangers 130 throughout the field where the geothermal power generation system 100 is applied.

[0052] Furthermore, in this embodiment, in addition to data acquired on the surface, data is acquired underground and used to evaluate each heat exchanger 130 a, 130 b, 130 c, thereby improving the accuracy of behavior evaluation of both the geothermal reservoir and the closed-loop well, thereby improving operational efficiency. In previous geothermal developments, there were few sensors suitable for high temperatures that could withstand geothermal temperatures, so continuous underground monitoring was not usually performed. However, the fiber sensors that make up the temperature sensors 133 a, 133 b, 133 c can be used at high temperatures.

[0053] Furthermore, the acoustic sensors 134a, 134b, 134c and the strain sensors 135a, 135b, 135c are used to monitor underground conditions as sensors that detect supplementary information such as micro-vibration data of geothermal fluids and strain data of geological formations in addition to the data detected by the temperature sensors 133a, 133b, 133c. In this way, by using the temperature sensors 133a, 133b, 133c, the acoustic sensors 134a, 134b, 134c, and the strain sensors 135a, 135b, 135c alone or in combination, it becomes possible to easily grasp underground conditions that cannot be confirmed directly with the naked eye.

[0054] In this embodiment, the heat exchange medium, which is a fluid circulating in the closed-loop flow path of the geothermal heat exchanger 130, is described as being high-temperature, high-pressure hot water or steam. However, it is also possible to use carbon dioxide gas (CO ), which is a fluid with excellent fluidity and heat transfer properties and high thermal conductivity, as the circulating fluid. ２ The heat exchange efficiency may be improved by using a gas such as CO ２ When gas is used as the circulating fluid of the geothermal heat exchanger 130, due to its properties, it is essentially in a gas phase or supercritical state within the loop of the geothermal heat exchanger 130.

[0055] When the circulating fluid used in the geothermal heat exchanger 130 is liquid, its heat must be exchanged with another substance such as a low boiling point fluid to evaporate it and then sent to the turbine. ２When gas is used as the circulating fluid in the geothermal heat exchanger 130, the fluid is basically in a gas phase or supercritical state within the loop of the geothermal heat exchanger 130. Therefore, the circulating fluid that serves as the heat exchange medium in the geothermal heat exchanger 130 can be sent directly to the turbine 123 as shown in Figure 9, eliminating the need to pass it through the evaporator 121, and improving energy efficiency is expected.

[0056] Furthermore, the shape of the well in which the geothermal exchanger 130 is installed is not limited to a straight, vertical shape. For example, as shown in FIG. 10(A), the well 103' of the geothermal exchanger 130' may be an L-shaped horizontal well. Furthermore, as shown in FIG. 10(B), the well 103'' of the geothermal exchanger 130'' may be an inclined well that is vertical from the ground to partway and then becomes oblique halfway. By applying this to a horizontal or inclined well, the surface area of ​​the loop in contact with the high-temperature stratum can be increased, allowing for the recovery of more thermal energy.

[0057] Next, the operation and effects of the geothermal power generation system according to this embodiment will be described.

[0058] The present inventors have conducted extensive research to solve the problem of recovering thermal energy from geothermal fields more efficiently and increasing power generation efficiency, and have discovered the following phenomenon: In a geothermal power generation system that generates power using thermal energy contained in geothermal fluid collected from a production well and retained in a geothermal reservoir, the hot water returned underground from a reinjection well is heated by an underground heat source such as a magma chamber as it moves, and the inventors have discovered that by installing a closed-loop geothermal heat exchanger between the reinjection well and the production well, the geothermal heat exchanger can continuously recover heat.

[0059] Specifically, by installing a closed-loop geothermal heat exchanger between the production well and the injecting well of a flash or binary geothermal power plant, which extracts geothermal fluid trapped in a geothermal reservoir from a production well and generates electricity using the high-temperature, high-pressure steam contained in the geothermal fluid, the geothermal formations near the geothermal heat exchanger well are continuously heated by the heat flow associated with the movement of hot water returned from the injecting well. Therefore, by placing the closed-loop geothermal heat exchanger well at the destination of the fluid injected from the injecting well, which absorbs heat and moves, heat convection is promoted near the closed-loop geothermal heat exchanger well as the fluid injected from the injecting well moves while being heated, enabling continuous heat recovery. This improves the heat recovery capacity of the closed-loop geothermal heat exchanger, potentially leading to increased power generation.

[0060] In addition, in this embodiment, by utilizing existing geothermal power generation equipment, it is possible to improve the heat recovery amount of the closed-loop geothermal heat exchanger and thereby increase the amount of power generation, making it possible to increase the amount of power generation of the closed-loop geothermal heat exchanger at relatively low cost.

[0061] Furthermore, in this embodiment, a temperature sensor capable of measuring underground temperature is provided in the geothermal heat exchanger, enabling temperature changes in the strata near the geothermal heat exchanger's well to be monitored. This makes it easy to control the heat exchange operation of the geothermal heat exchanger on and off based on the detection results of the temperature sensor. In particular, by providing multiple geothermal heat exchangers between two wells and controlling their operation separately, continuous heat exchange and associated power generation by the geothermal heat exchangers in a closed-loop system throughout the entire geothermal power generation system are possible.

[0062] [Second embodiment] The schematic configuration of a geothermal power generation system according to another embodiment of the present invention will be described with reference to the drawings. Fig. 11 is an explanatory diagram showing the schematic configuration of the entire geothermal power generation system according to the second embodiment of the present invention, and Fig. 12 is a block diagram showing the schematic configuration of the lower part of the geothermal power generation system according to the second embodiment of the present invention.

[0063] The geothermal power generation system 200 of this embodiment is a geothermal power generation system applied to an EGS (Enhanced Geothermal System) type geothermal power generation facility that generates power by utilizing thermal energy contained in a hot dry rock mass HR1 in a geothermal field, high-temperature strata, etc. In other words, the geothermal power generation system 200 is a system configured by combining a geothermal power generation facility using a closed-loop geothermal heat exchanger 230 with an EGS type geothermal power generation facility.

[0064] As shown in Fig. 11 , the geothermal power generation system 200 includes a production well 201, an injection well 202, a first geothermal power generation facility 210, a second geothermal power generation facility 220, and a geothermal heat exchanger 230. As shown in Fig. 12 , the injection well 202 is a borehole through which a fluid is injected into a hot dry rock mass HR1 or a high-temperature stratum located underground in a geothermal field. The production well 201 is a borehole through which geothermal fluid produced by heating the fluid injected from the injection well 202 with thermal energy in the hot dry rock mass HR1 or the high-temperature stratum is extracted.

[0065] The first geothermal power generation facility 210 generates electricity by utilizing thermal energy contained in geothermal fluid produced by heating fluid injected from an injection well 202 with thermal energy from a hot dry rock mass HR1 extracted from a production well 201 or from a high-temperature geological formation. As shown in Figure 11, the first geothermal power generation facility 210 mainly includes a first flasher 211, a second flasher 212, a turbine 213, a generator 214, a condenser 215, a high-pressure circulation pump 216, etc. The first geothermal power generation facility 210 recovers heat from an artificial geothermal reservoir created or expanded in the hot dry rock mass HR1 or the like by hydraulic fracturing or the like. Therefore, fluid such as water is injected into an artificial reservoir from an injection well 202, the fluid heated in the artificial reservoir is recovered from a production well 201 as geothermal fluid, the thermal energy contained in the artificial geothermal fluid is used to generate electricity, and then the used geothermal fluid is injected underground from the injection well 202, and the heat from the bedrock is extracted by the circulation of water.

[0066] The first geothermal power generation facility 210 takes in geothermal water heated by artificial means and separates it into steam in a first flasher 211, which is a steam-water separator. The separated steam is sent to a turbine 213. Optionally, steam is further separated in a second flasher 212 to obtain secondary steam, which is also sent to the turbine 213, and electricity is generated by the rotation of the turbine 213 in a generator 214. The steam consumed in the turbine 213 is condensed in a condenser 215. The condensed artificial geothermal water is either cooled and discharged, or cooled and used as cooling water for the condenser 215, or injected into the geothermal zone via an injection well 202. The hot water obtained by steam-water separation in the second flasher 212 is sent to the injection well 202 by a high-pressure circulation pump 216.

[0067] The first geothermal power generation facility 210 is not limited to the above-described configuration, and other components may be replaced with other components, or additional components may be installed. In this embodiment, the first geothermal power generation facility 210 is illustrated as a double-flash system as shown in Figure 1 , but it may also be applied to a single-flash system in which hot water separated from steam in the first flasher 211 is directly injected into the geothermal zone from the injection well 202.

[0068] Furthermore, as described above, the geothermal power generation system 200 employs, as the first geothermal power generation facility 210, a geothermal power generation facility of the flash power generation type that generates electricity using high-temperature, high-pressure steam contained in the artificial geothermal fluid extracted from the production well 201. The geothermal power generation system 200 of this embodiment is not limited to a geothermal power generation facility of the flash power generation type as the first geothermal power generation facility 210, but can also be applied to a geothermal power generation facility of the binary type that generates electricity using steam obtained by boiling a medium with a boiling point lower than that of water using the artificial geothermal fluid extracted from the production well 201.

[0069] The second geothermal power generation facility 220 is a binary geothermal power generation facility that uses a closed-loop geothermal heat exchanger 230, which exchanges heat in a geothermal zone with a heat exchange fluid circulating in a closed-loop flow path. Unlike the first geothermal power generation facility 210, the second geothermal power generation facility 220 does not need to discharge the heat exchange fluid that receives heat from underground into the geothermal zone or to extract hot water from the geothermal zone. The heat exchange fluid used in the geothermal heat exchanger 230 is preferably a low-boiling-point liquid with a boiling point of 150°C or less at atmospheric pressure, such as water or water with dissolved ammonia, but is not limited to these.

[0070] The geothermal heat exchanger 230 includes an outer pipe 231 buried underground facing the geothermal heat field, and an inner pipe 232 disposed inside the outer pipe 231. The geothermal heat exchanger 230 of this embodiment is identical in configuration and operation to the geothermal heat exchanger 130 of the first embodiment, and therefore a detailed description thereof will be omitted. In this embodiment, a double-pipe structure is used as the closed-loop geothermal heat exchanger 230. However, other configurations may be used as long as the heat exchange fluid is circulated within a closed-loop flow path formed underground and heat is exchanged in the geothermal heat field. For example, a closed-loop geothermal heat exchanger may be configured by excavating a mesh-like loop connecting the surface and the underground several thousand meters, and circulating water through the loop to extract underground heat.

[0071] 11 and 12, the second geothermal power generation facility 220 includes an evaporator 221, a tank 222, a turbine 223, a generator 224, a condenser 225, and a high-pressure circulation pump 226. Note that the second geothermal power generation facility 220 of this embodiment is identical in configuration and operation to the second geothermal power generation facility 120 of the first embodiment, and therefore detailed description thereof will be omitted.

[0072] In the geothermal power generation system 200 of this embodiment, a geothermal heat exchanger 230 is provided at a point between the production well 201 and the injection well 202. That is, in the EGS geothermal power generation facility 210, thermal energy is recovered by injecting a fluid such as water from the injection well 202 into an artificial reservoir and recovering the geothermal fluid heated in the artificial reservoir from the production well 201. In the artificial reservoir, the injected fluid gradually moves through the stratum, so the well of the closed-loop geothermal heat exchanger 230 is provided at the destination of this heated geothermal fluid.

[0073] As described above, in the geothermal power generation system 200 of this embodiment, the geothermal heat exchanger 230 is applied when installed at any point between the production well 201 and the injection well 202 of an existing first geothermal power generation facility 210 (hereinafter also referred to as the existing geothermal power generation facility 210). When the existing geothermal power generation facility 210 is constructed, a geological survey of the strata at the installation site is conducted in advance, and the geothermal reservoir GR1 in the geothermal zone is monitored even during operation of the geothermal power generation facility, resulting in the accumulation of strata data around the existing EGS-type geothermal power generation facility 210. Therefore, in this embodiment, the geothermal heat exchanger 230 is installed at any point between the production well 201 and the reinjection well based on the results of an analysis of the strata data around the existing geothermal power generation facility 210.

[0074] Next, the operation and effects of the geothermal power generation system according to this embodiment will be described.

[0075] The present inventors have conducted extensive research to solve the problem of recovering thermal energy from geothermal fields more efficiently and increasing power generation efficiency, and have discovered the following phenomenon: In other words, the present inventors have discovered that in EGS geothermal power generation facilities, fluid injected underground from an injection well is heated by an underground heat source such as a magma chamber as it moves, and therefore, by installing a closed-loop geothermal heat exchanger between the injection well and the production well, the geothermal heat exchanger can continuously recover heat.

[0076] That is, by installing a closed-loop geothermal heat exchanger between the production well and the injection well of an EGS geothermal power generation facility that extracts geothermal fluid generated in an artificial geothermal reservoir, such as a hot dry rock mass in a geothermal field, and uses the high-temperature, high-pressure steam contained in the geothermal fluid to generate electricity, the geological formations near the geothermal heat exchanger well are continuously heated by the heat flow accompanying the movement of hot water returned from the injection well. Therefore, since the closed-loop geothermal heat exchanger well is located at the destination of the fluid injected from the injection well, absorbing heat and moving, heat convection is promoted near the closed-loop geothermal heat exchanger well as the fluid injected from the injection well moves while being heated, enabling continuous heat recovery. As a result, an increase in power generation can be expected as the heat recovery capacity of the closed-loop geothermal heat exchanger is improved.

[0077] Furthermore, in this embodiment, by utilizing existing EGS geothermal power generation facilities, it is possible to improve the heat recovery amount of the closed-loop geothermal heat exchanger and increase the amount of power generated, which makes it possible to increase the amount of power generated by the closed-loop geothermal heat exchanger at a relatively low cost.

[0078] Furthermore, in this embodiment, a temperature sensor capable of measuring underground temperature may be provided in the geothermal heat exchanger, allowing temperature changes in the strata near the geothermal heat exchanger's well to be monitored. In this case, the heat exchange operation of the geothermal heat exchanger can be easily controlled on and off based on the detection results of the temperature sensor. In particular, by providing multiple geothermal heat exchangers between two wells and controlling their operation separately, continuous heat exchange and associated power generation by the geothermal heat exchangers in a closed-loop system throughout the entire geothermal power generation system are possible.

[0079] Although each embodiment of the present invention has been described in detail above, it will be readily apparent to those skilled in the art that many modifications are possible without substantially departing from the novel features and effects of the present invention. Therefore, all such modifications are intended to be included within the scope of the present invention.

[0080] For example, a term that is described at least once in the specification or drawings together with a different term having a broader or similar meaning can be replaced with that different term anywhere in the specification or drawings. Furthermore, the configuration and operation of the geothermal power generation system are not limited to those described in each embodiment of the present invention, and various modifications are possible.

[0081] According to the present invention, the amount of heat recovered from the geothermal zone can be improved, thereby increasing the amount of power generation.

[0082] 100, 200 Geothermal power generation system 110, 210 Power generation equipment (first power generation equipment) 111, 211 First flasher 112, 212 Second flasher 113, 213 Turbine 114, 214 Generator 115, 215 Condenser 116, 216 High-pressure circulation pump 120, 220 Power generation equipment (second power generation equipment) 121, 221 Evaporator 122, 222 Tank 123, 223 Turbine 124, 224 Generator 125, 225 Condenser 126, 226 High-pressure circulation pump 130, 230 Geothermal heat exchanger 131, 231 Outer pipe 131a Downward flow path 132, 232 Inner pipe 132a Upward flow path 133, 133a, 133b, 133c, 133in, 133out Temperature sensors 134a, 134b, 134c Acoustic sensors 135a, 135b, 135c Strain sensors 140 Control unit 141 Receiving unit 142 Determination unit 143 Transmitting unit GR1 Geothermal reservoir HR1 Hot dry rock

Claims

1. A geothermal power generation system that generates electricity by utilizing thermal energy in a geothermal zone, comprising: at least two or more boreholes; power generation equipment that extracts geothermal fluid generated in the geothermal zone from any of the two or more boreholes and generates electricity by utilizing the thermal energy contained in the geothermal fluid; and a geothermal heat exchanger that exchanges heat in the geothermal zone with fluid circulating in a flow path configured in a closed loop, wherein the geothermal power generation system is provided at a point between the two or more boreholes.

2. The geothermal power generation system of claim 1, wherein the geothermal heat exchanger comprises an outer pipe buried in the ground toward the geothermal zone and an inner pipe disposed inside the outer pipe, forming a closed-loop flow path with a double-pipe structure, and a fluid is pressurized between the outer pipe and the inner pipe, and the fluid is heated in the geothermal zone, resulting in a heated fluid that is transported while rising up the inner pipe.

3. A geothermal power generation system as described in claim 2, wherein the geothermal heat exchanger is provided with a temperature sensor capable of measuring the underground temperature on at least one of the outer surface side of the outer tube or the outer surface side of the inner tube.

4. A geothermal power generation system as described in claim 3, wherein the geothermal heat exchanger is controlled to stop heat exchange operation when the temperature measured by the temperature sensor is below a predetermined threshold, and to resume heat exchange operation when the temperature measured by the temperature sensor recovers to above another predetermined threshold.

5. A geothermal power generation system as described in claim 4, wherein the geothermal heat exchangers are provided at any point between the two or more boreholes, and each of the multiple geothermal heat exchangers has its heat exchange operation switched on and off based on the measured temperature of the temperature sensor.

6. A geothermal power generation system as described in claim 3, wherein the geothermal heat exchanger is further equipped with at least one of an acoustic sensor or a strain sensor, and the heat exchange operation of the geothermal heat exchanger is controlled based on detection data from either the temperature sensor, the acoustic sensor or the strain sensor.

7. A geothermal power generation system as described in claim 3, wherein the geothermal heat exchanger circulates the fluid having a predetermined temperature or higher through the flow path when the temperature measured by the temperature sensor is equal to or lower than a predetermined threshold value.

8. A geothermal power generation system as described in claim 1, wherein the geothermal heat exchanger uses carbon dioxide gas as the fluid circulated within the flow path.

9. The geothermal power generation system according to claim 1, wherein the well in which the geothermal heat exchanger is installed includes either a deviated well or a horizontal well.

10. The geothermal power generation system of claim 2, wherein the power generation equipment comprises: a first geothermal power generation equipment that generates power by utilizing the thermal energy contained in the geothermal fluid extracted from any of the two or more wells; and a second geothermal power generation equipment that generates power by utilizing the thermal energy contained in the heating fluid transported from the geothermal heat exchanger.

11. A geothermal power generation system as described in any one of claims 1 to 10, wherein the two or more boreholes include a production well that extracts the geothermal fluid from a geothermal reservoir formed underground in the geothermal zone, and a reinjection well that returns reinjected water discharged from the geothermal fluid after heat exchange in the power generation equipment to the ground, and the power generation equipment generates electricity by utilizing the thermal energy contained in the geothermal fluid extracted from the production well and retained in the geothermal reservoir.

12. A geothermal power generation system as described in any one of claims 2 to 10, wherein the two or more boreholes include an injection well for injecting a fluid into a hot rock mass or a high temperature stratum underground in the geothermal zone, and a production well for extracting the geothermal fluid produced by heating the fluid with the thermal energy in the hot rock mass or the high temperature stratum, and the power generation facility generates power by utilizing the thermal energy contained in the geothermal fluid produced by heating the fluid with the thermal energy in the hot rock mass or the high temperature stratum extracted from the production well.

13. A geothermal power generation method for generating electricity by utilizing thermal energy in a geothermal zone, comprising: a power generation facility that extracts geothermal fluid produced in the geothermal zone from one of at least two or more boreholes and generates electricity by utilizing the thermal energy contained in the geothermal fluid; a geothermal heat exchanger that exchanges heat in the geothermal zone with fluid circulating in a flow path configured in a closed loop at a point between the two or more boreholes; and a geothermal power generation method that generates electricity by utilizing the thermal energy contained in the heated fluid obtained by heat exchange in the geothermal heat exchanger.

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