Control device, control method, and control program for geothermal power plant

Abstract

The present invention provides a control device, a control method, and a control program for a geothermal power plant, with which it is possible to accurately obtain the steam production amount of a well. Provided is a control device (50) for controlling a geothermal power plant that generates electricity, the geothermal power plant including a plurality of wells from which a geothermal fluid is ejected, and one separator that separates the geothermal fluid ejected from each well into steam and hot water. The control device (50) comprises an acquisition unit (51) that acquires information regarding each well, and an estimation unit (52) that estimates, for each well, a function expression indicating a correlation, from the wellhead pressure of the well, the pressure of the separator, the valve opening degree of a flow control valve of the well, and the flow rate of steam separated by the separator. The control device (50) activates a first well among the plurality of wells, the acquisition unit (51) acquires information regarding the first well, and the estimation unit (52) estimates a first function expression indicating the correlation of the first well. The control device (50) activates a second well while the first well is being activated, the acquisition unit (51) acquires information regarding the second well, and the estimation unit (52) estimates a second function expression indicating the correlation of the second well.

Description

Geothermal power plant control device, control method, and control program

[0001] The present disclosure relates to a control device, a control method, and a control program for a geothermal power plant.

[0002] In geothermal power plants, steam separated from geothermal fluid (mainly a mixture of steam and hot water) spouting from wells is introduced into a steam turbine to generate electricity. Therefore, when geothermal fluid spouting from multiple wells is combined and utilized, well management is performed to maximize the power generation by controlling the flow rate of the spouting geothermal fluid based on the well characteristics (pressure and flow rate characteristics of the spouting fluid) of each well. In well management, changes in well characteristics are identified and the flow rate of the geothermal fluid spouting from the wells is optimized (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2020-176590

[0004] The invention of Patent Document 1 grasps the well characteristics when a separator corresponding to each well is installed, but in general geothermal power plants, one separator is often installed for multiple wells in order to reduce equipment costs.

[0005] Patent Document 1 discloses a method for estimating well characteristics for each well when one separator is installed for multiple wells. However, it requires the installation of both a steam flow meter and a hot water flow meter, or the installation of a two-phase flow meter that measures the flow rate of a gas-liquid two-phase flow consisting of steam and hot water. While the use of a two-phase flow meter can reduce the number of flow meters, it is difficult to accurately measure the flow rates of steam and hot water in a two-phase flow state using existing general-purpose technology.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to provide a control device, control method, and control program for a geothermal power plant that can accurately grasp the steam production volume of a borehole while keeping costs down.

[0007] In order to solve the above problems, the present disclosure provides a geothermal power plant control device, control method, and control program, which employ the following means: The present disclosure provides a geothermal power plant control device that controls a geothermal power plant that includes a plurality of wells from which geothermal fluid gushes out and a separator that separates the geothermal fluid gushes out from the plurality of wells into steam and hot water, and generates power using the steam separated by the separator, the control device including an acquisition unit that acquires the wellhead pressure of each of the wells, the pressure of the separator, valve apertures of a plurality of flow control valves provided between each of the wells and the separator, and the flow rate of the steam separated by the separator, and calculates, for each of the wells, a function expression that indicates a correlation between the wellhead pressure of the well, the pressure of the separator, the valve apertures of the flow control valves of the wells, and the flow rate of the steam separated by the separator. and an estimation unit that estimates the above, wherein a first well among the plurality of wells is started up, and the acquisition unit acquires the wellhead pressure of the first well, the pressure of the separator, the valve opening of the flow control valve of the first well, and the flow rate of the steam separated by the separator, and the estimation unit estimates a first function equation that indicates the correlation of the first well and the steam flow rate of the first well, and a second well is started up while the first well is kept started up, and the acquisition unit acquires the wellhead pressure of the second well, the pressure of the separator, the valve opening of the flow control valve of the second well, and the flow rate of the steam separated by the separator, and the estimation unit estimates a second function equation that indicates the correlation of the second well and the steam flow rate of the second well.

[0008] The control method of the present disclosure is a control method for a geothermal power plant comprising a plurality of wells from which geothermal fluid gushes out, and a separator that separates the geothermal fluid gushes out from the plurality of wells into steam and hot water, and which generates power using the steam separated by the separator, the control method comprising: an acquisition step of acquiring the wellhead pressure of each of the wells, the pressure of the separator, valve apertures of a plurality of flow control valves provided between the wells and the separator, and the flow rate of the steam separated by the separator; and an estimation step of estimating, for each of the wells, a function expression indicating a correlation between the wellhead pressure of the well, the pressure of the separator, the valve apertures of the flow control valves of the wells, and the flow rate of the steam separated by the separator, a first acquisition step of acquiring the wellhead pressure of the first well, the pressure of the separator, the valve opening of the flow control valve of the first well, and the flow rate of the steam separated by the separator; a first function formula showing the correlation of the first well, and a first estimation step of estimating the steam flow rate of the first well; a second startup step of starting up a second well while keeping the first well in operation; a second acquisition step of acquiring the wellhead pressure of the second well, the pressure of the separator, the valve opening of the flow control valve of the second well, and the flow rate of the steam separated by the separator; and a second function formula showing the correlation of the second well, and a second estimation step of estimating the steam flow rate of the second well.

[0009] The control program of the present disclosure causes a computer to execute the above-described control method.

[0010] According to the present disclosure, it is possible to accurately grasp the steam production volume of each well, which has not previously been possible to measure accurately.

[0011] 1 is a diagram illustrating a geothermal power plant including a control device according to some embodiments of the present disclosure; 2 is a diagram illustrating an example of a hardware configuration of a control device according to some embodiments of the present disclosure; 3 is a diagram illustrating an example of a function of a control device according to some embodiments of the present disclosure; 4 is a diagram illustrating a relationship between a differential pressure and a steam flow rate of a geothermal power plant according to some embodiments of the present disclosure; 5 is a diagram illustrating a control flow of a control device according to some embodiments of the present disclosure; and 6 is a diagram illustrating a time course of a steam flow rate of a geothermal power plant according to some embodiments of the present disclosure.

[0012] An embodiment of a control device, a control method, and a control program for a geothermal power plant according to the present disclosure will be described below with reference to the drawings. The control device 50 can be widely applied to any geothermal power plant 1 that generates electricity using geothermal fluid ejected from a well 10, and is not limited to the geothermal power plant 1 having the configuration described below.

[0013] FIG. 1 is a diagram illustrating a geothermal power plant equipped with a control device according to some embodiments of the present disclosure. In this disclosure, a case where a plurality of boreholes 10 are provided, for example, two boreholes 10, will be described. The geothermal power plant 1 shown in FIG. 1 is, for example, a flash cycle type geothermal power plant 1, but the control device 50 can be similarly applied to geothermal power plants 1 of other configurations, such as a binary cycle type. In FIG. 1, for example, two boreholes 10 are provided and one separator 60 is provided, but the present disclosure can be applied as appropriate without being limited to the above configuration and the number of components.

[0014] As shown in FIG. 1 , the geothermal power plant 1 includes a borehole 10, a pressure gauge 20, an on-off valve 30, a flow control valve 40, a separator 60, a separator pressure gauge 70, a flow meter 80, and a control device 50.

[0015] The geothermal power plant 1 includes a plurality of wells 10, each of which is provided with a pressure gauge 20, an on-off valve 30, and a flow control valve 40. This disclosure and FIG. 1 describe a case in which two wells 10 (a first well 10a and a second well 10b) are included, but the number of wells 10 may be three or more, and there is no restriction on the number.

[0016] In the present disclosure, the plurality of boreholes 10 are referred to as a first borehole 10a and a second borehole 10b. A pressure gauge 20a, an on-off valve 30a, and a flow control valve 40a are provided corresponding to the first borehole 10a, and a pressure gauge 20b, an on-off valve 30b, and a flow control valve 40b are provided corresponding to the second borehole 10b.

[0017] The flow control valve 40 is provided on a geothermal fluid transport pipe that guides the geothermal fluid spouted from the borehole 10 to the separator 60, and adjusts the total flow rate (spouting amount, total flow rate of steam and hot water) of the geothermal fluid flowing from the borehole 10 to the separator 60. The wellhead pressure of the borehole 10 can also be adjusted by adjusting the flow control valve 40.

[0018] A pressure gauge 20 for measuring wellhead pressure (ejection pressure) is provided on the geothermal fluid transport pipe, upstream of the flow control valve 40 in the direction of the geothermal fluid flow. The pressure gauge 20 measures the pressure of the geothermal fluid ejected from the borehole 10. An on-off valve 30 may be provided on the geothermal fluid transport pipe upstream of the geothermal fluid flow (near the outlet of the borehole 10; for example, between the pressure gauge 20 and the flow control valve 40) to control the conduction state (conduction state or non-conduction state) of the geothermal fluid.

[0019] The separator 60 is a device (water-steam separator) that separates the geothermal fluid, which is a two-phase mixed fluid supplied through a geothermal fluid transport pipe, into steam and hot water. The hot water separated by the separator 60 is led to a hot water pipe, and the steam separated by the separator 60 is led to a steam pipe. The flow rate of the steam led to the steam pipe is measured by a flow meter 80 installed on the steam pipe. A separator pressure gauge 70 is installed in the separator 60 and measures the pressure of the separator 60.

[0020] The hot water pipe is a pipe that guides the hot water separated by the separator 60 to an injecting well (not shown). By returning the hot water to the underground geothermal reservoir through the injecting well, depletion of geothermal fluid in the underground geothermal reservoir is prevented. The hot water separated by the separator 60 may be pumped to the injecting well via a pump (not shown). If the hot water can be pumped to the injecting well by its own pressure, the pump may be omitted or may have a small capacity. The flow rate of the hot water sent to the injecting well is measured by a flow meter (not shown) installed on the hot water pipe.

[0021] In the following description, when distinguishing between each borehole 10, pressure gauge 20, on-off valve 30 and flow control valve 40, either a or b is added to the end, and when not distinguishing between each borehole 10, pressure gauge 20, on-off valve 30 and flow control valve 40, a or b is omitted.

[0022] 2 is a diagram illustrating an example of a hardware configuration of a control device according to some embodiments of the present disclosure. As shown in FIG. 2, the control device (Controller) 50 is a computer system including, for example, a CPU (Central Processing Unit: Processor) 1100, a secondary storage device (ROM, Secondary storage: Memory) 1200, a main storage device (RAM, Main Memory) 1300, a hard disk drive (HDD) 1400 as a large-capacity storage device, and a communication unit 1500 for connecting to a network or the like. A solid-state drive (SSD) may also be used as the large-capacity storage device. These units are connected via a bus 1800.

[0023] The CPU 1100 controls the entire control device 50 using, for example, an operating system (OS) stored in a secondary storage device 1200 connected via a bus 1800, and executes various processes by executing various programs stored in the secondary storage device 1200. One or more CPUs 1100 may be provided, and they may cooperate with each other to realize processes.

[0024] The main memory device 1300 is composed of writable memory such as cache memory or RAM (Random Access Memory), and is used as a working area for reading out programs executed by the CPU 1100 and writing data processed by the programs.

[0025] The secondary storage device 1200 is a non-transitory computer-readable storage medium. The secondary storage device 1200 is, for example, a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, or a semiconductor memory. Examples of the secondary storage device 1200 include a read-only memory (ROM), a hard disk drive (HDD), a solid state drive (SSD), and a flash memory. The secondary storage device 1200 stores, for example, an OS for controlling the entire information processing device, such as Windows (registered trademark), iOS (registered trademark), or Android (registered trademark), a BIOS (Basic Input / Output System), various device drivers for operating peripheral devices, various application software, and various data and files. The secondary storage device 1200 also stores programs for implementing various processes and various data required for implementing the various processes. A plurality of secondary storage devices 1200 may be provided, and the above-mentioned programs and data may be stored separately in each secondary storage device 1200.

[0026] The control device 50 may also include an input unit such as a keyboard or a mouse, a display unit such as a liquid crystal display device that displays data, etc. The control device 50 may also include a notification unit such as a speaker that includes the display unit and outputs a lamp, sound, especially an alarm sound.

[0027] 3 is a diagram illustrating an example of the functions of a control device according to some embodiments of the present disclosure. As shown in FIG. 3, the control device 50 includes an acquisition unit 51 and an estimation unit 52.

[0028] A series of processes for realizing the functions of the control device 50 is stored in the form of a program in the secondary storage device 1200 (see FIG. 2), for example. The CPU (processor) 1100 (see FIG. 2) reads this program into the main storage device 1300 (see FIG. 2) and executes information processing and arithmetic processing to realize various functions. Note that the program may be pre-installed in the secondary storage device 1200, provided in a state stored in another non-transitory computer-readable storage medium, or distributed via wired or wireless communication means. Examples of non-transitory computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

[0029] 3 acquires various information related to each well 10 and separator 60 of the geothermal power plant 1. Specifically, the acquisition unit 51 acquires the wellhead pressure of each well 10, the pressure of the separator 60, the valve opening degree of each flow control valve 40, and the steam flow rate of each well 10.

[0030] The estimation unit 52 estimates a function formula indicating the correlation between each well 10 based on the information acquired by the acquisition unit 51.

[0031] The function equation indicating the correlation between each well 10 estimated by the estimation unit 52 may be output to the output device 55.

[0032] The estimation unit 52 derives a function formula indicating the correlation between each well 10 as follows: For example, consider a case where two wells 10 (a first well 10a and a second well 10b) are connected to one separator 60 (see FIG. 1 ).

[0033] 1 , the measured value of the wellhead pressure by the pressure gauge 20a of the first well is denoted as p1, and the measured value of the wellhead pressure by the pressure gauge 20b of the second well is denoted as p2. The measured value of the pressure of the separator 60 by the separator pressure gauge 70 is denoted as ps. The valve opening of the flow control valve 40a of the first well is denoted as X1, and the valve opening of the flow control valve 40b of the second well is denoted as X2. If the steam flow rate of the first well 10a is denoted as G1 and the steam flow rate of the second well 10b is denoted as G2, then the following relationship between equations (1) and (2) is established.

[0034] G1=f1 (p1, ps, X1)...(1) G2=f2(p2, ps, X2)...(2)

[0035] In equation (1), f1 is a first function that indicates the correlation between the values ​​(G1, p1, ps, and X1) in the first well 10a. In equation (2), f2 is a second function that indicates the correlation between the values ​​(G2, p2, ps, and X2) in the second well 10b.

[0036] Geothermal fluids that gush out from a typical well 10 are often saturated gas-liquid two-phase flows. Therefore, equations (1) and (2) should normally consider the hot water flow rate in addition to the steam flow rate. However, as a result of data analysis, the inventors discovered that the relationships between equations (1) and (2) are independent of the hot water flow rate (the effect is so small that it can be ignored). This is thought to be because the specific enthalpy of the geothermal fluid does not change in the short term, i.e., the state of the geothermal reservoir does not change in the short term, so the ratio of hot water to steam remains constant or changes only slightly.

[0037] In reality, the pressure loss increases due to the presence of hot water compared to the case of steam alone, but since the ratio of hot water to steam is uniquely determined, the function fn is determined taking into account the influence of hot water.

[0038] It is generally known that if the fluid in the well 10 is an incompressible fluid such as water, the pressure loss is proportional to the dynamic pressure. Therefore, using the apparent pressure loss coefficient ζ, the following relationship in equation (3) can be derived for the first well 10a, for example, from Bernoulli's theorem. Here, the pressure loss coefficient ζ is a characteristic value that combines the pressure losses of the piping and valves, and also depends on the valve opening Xn (it is a function of the valve opening Xn).

[0039]

[0040] In equation (3), ρ represents the fluid density (vapor density). When equation (3) is solved for G1, the following equation (4) is obtained.

[0041]

[0042] Specifically, equation (1) is expressed as equation (4). Equation (2) can be expressed in a similar manner. As mentioned above, the apparent pressure loss coefficient ζ is affected by the ratio of hot water to steam. Because the ratio of hot water to steam depends on the state of the reservoir, it is difficult to determine the pressure loss coefficient ζ in advance from the design data of the geothermal power plant 1. Equation (4) ignores the compressibility of steam, but in practice, the apparent pressure loss coefficient ζ is determined by including a correction coefficient based on the compressibility of steam. Therefore, in the present disclosure, the function formula f, i.e., the first function formula f1 in equation (1) and the second function formula f2 in equation (2), is determined using operational data.

[0043] FIG. 4 is a diagram illustrating the relationship between differential pressure and steam flow rate in a geothermal power plant according to some embodiments of the present disclosure. In FIG. 4, the vertical axis represents the steam flow rate G1, and the horizontal axis represents the differential pressure ps-p1. In the present disclosure, the horizontal axis represents the differential pressure between the pressure ps of the separator 60 and the wellhead pressure p1 of the first well 10a. In FIG. 4, triangles (△) represent values ​​for a valve opening Z1 of the flow control valve 40a of the first well, and circles (◯) represent values ​​for a valve opening Z1' of the flow control valve 40a of the first well. Here, the valve opening Z1' is a value greater than the valve opening Z1. In FIG. 4, the dashed line represents the trend of values ​​for a valve opening Z1, and the solid line represents the trend of values ​​for a valve opening Z1'.

[0044] 4, it can be seen that the steam flow rate G1 has a relationship that approximates the 1 / 2 power of the differential pressure ps-p1, which also coincides with the above-mentioned equation (4).

[0045] As shown in Figure 4, the steam flow rate G1 corresponding to the pressure difference p-p1 when the valve opening is Z1 is higher than the steam flow rate G1 corresponding to the pressure difference p-p1 when the valve opening is Z1'. Figure 4 shows that the steam flow rate increases as the valve opening increases.

[0046] 5 is a diagram showing a control flow of a control device in some embodiments of the present disclosure. The control device 50 activates any of the multiple wells 10 that can be activated. In the present disclosure, the first well 10a is activated (S101). The activated well 10 may be any well 10 that can be activated.

[0047] In the geothermal power plant 1, when restarting production after a periodic inspection or other such shutdown, it is common to start up the wells 10 one by one. This control flow can be implemented by taking advantage of such an opportunity.

[0048] Next, in step S102, the acquisition unit 51 of the control device 50 acquires data on the first well 10a. The acquisition unit 51 acquires the following data on the first well 10a: the wellhead pressure of the first well 10a, the pressure of the separator 60, the valve aperture of the flow control valve 40a of the first well, and the steam flow rate of the first well 10a. The wellhead pressure of the first well 10a is acquired from the pressure gauge 20a of the first well. The pressure of the separator 60 is acquired from the separator pressure gauge 70. The valve aperture of the flow control valve 40a of the first well is acquired from the flow control valve 40a of the first well or the control device 50 that controls the flow control valve 40a of the first well.

[0049] The steam flow rate of the first well 10a is obtained from a flow meter 80. The flow meter 80 is installed downstream of the separator 60 and detects the total flow rate of all wells 10. When only the first well 10a is activated, the steam flow rate measured by the flow meter 80 can be interpreted as the steam flow rate of the first well 10a.

[0050] In acquiring data on the first well 10a by the acquisition unit 51, the control device 50 performs an operation to appropriately change the valve opening X1 of the flow control valve 40a of the first well and the pressure pS of the separator 60, and acquires the corresponding wellhead pressure p1 and steam flow rate G1 of the first well 10a. The pressure pS of the separator 60 can be changed, for example, by operating an atmosphere release valve (not shown) of an atmosphere release facility (not shown) provided between the separator 60 and the turbine (not shown) of the geothermal power plant 1, or a governor valve (not shown) at the turbine inlet.

[0051] Next, in step S103, the estimation unit 52 of the control device 50 estimates a first function formula f1 using equation (1) from the data of the first borehole 10a acquired by the acquisition unit 51. Once the first function formula f1 is identified for the first borehole 10a, the steam flow rate G1 of the first borehole 10a can be estimated from the wellhead pressure p1 of the first borehole 10a, the valve opening X1 of the flow control valve 40a of the first well, and the pressure ps of the separator 60.

[0052] The estimation unit 52 estimates the first function formula f1 using data acquired by appropriately changing the valve opening X1 of the flow control valve 40a of the first well and the pressure ps of the separator 60 as described above.

[0053] The estimation unit 52 may estimate the first function formula f1 by machine learning the data of the first well 10a acquired by the acquisition unit 51.

[0054] Next, in step S104, the control device 50 determines whether or not there is a next well 10 that can be activated. If it is determined that there is a next well 10 that can be activated, the process proceeds to step S105. On the other hand, if it is determined that there is no next well 10 that can be activated, the process ends.

[0055] In step S105, the control device 50 starts up the second well 10b. In this case, any well 10 that can be started up may be used. The second well 10b may also be started up manually by an operator.

[0056] Next, in step S106, the acquisition unit 51 of the control device 50 acquires data on the second well 10b. The acquisition unit 51 acquires the following data on the second well 10b: the wellhead pressure of the second well 10b, the pressure of the separator 60, the valve aperture of the flow control valve 40b of the second well, and the steam flow rate of the second well 10b. The wellhead pressure of the second well 10b is acquired from the pressure gauge 20b of the second well. The pressure of the separator 60 is acquired from the separator pressure gauge 70. The valve aperture of the flow control valve 40b of the second well is acquired from the flow control valve 40b of the second well or the control device 50 that controls the flow control valve 40b of the second well.

[0057] The steam flow rate of the second well 10b is calculated by subtracting the steam flow rate of the first well 10a obtained from function formula f1 from the measurement value of the flow meter 80. The flow meter 80 is installed downstream of the separator 60 and detects the total flow rate of all wells 10. When only the first well 10a and the second well 10b are activated, the steam flow rate measured by the flow meter 80 can be interpreted as the sum of the steam flow rate of the first well 10a and the steam flow rate of the second well 10b.

[0058] 6 is a diagram showing the time course of the steam flow rate of a geothermal power plant according to some embodiments of the present disclosure. In FIG. 6, each vertical axis represents the steam flow rate, and each horizontal axis represents time. In FIG. 6, the solid line represents the steam flow rate of the geothermal power plant 1 detected by the flow meter 80, and the dashed line represents the steam flow rate of the first well 10a.

[0059] 6A, only the first well 10a is in operation between times t0 and t1, so the steam flow rate indicated by the flow meter 80 is the steam flow rate of the first well 10a.

[0060] At time t1, the second well 10b is activated in addition to the first well 10a. Between times t1 and t2, the first well 10a and the second well 10b are in operation. Therefore, the steam flow indicated by the flow meter 80 is the sum of the steam flow rate of the first well 10a and the steam flow rate of the second well 10b.

[0061] At time t2, the second well 10b is shut down. After time t2, only the first well 10a is in operation. Therefore, the steam flow rate indicated by the flow meter 80 is the steam flow rate of the first well 10a.

[0062] By executing steps S101 to S103 in Fig. 5, the steam flow rate of the first well 10a is derived from the first function formula f1. The derived steam flow rate of the first well 10a is indicated by the dashed line in Fig. 6(b).

[0063] As described above, the first well 10a and the second well 10b are in operation between times t1 and t2. The steam flow rate indicated by the flow meter 80 is the sum of the steam flow rate of the first well 10a and the steam flow rate of the second well 10b. The steam flow rate of the second well 10b can be calculated by subtracting the steam flow rate of the first well 10a from the steam flow rate indicated by the flow meter 80.

[0064] 6(b) is the steam flow rate of the second well 10b, which is obtained by subtracting the steam flow rate of the first well 10a from the steam flow rate indicated by the flow meter 80. The steam flow rate of the activated well 10 can be calculated by subtracting the total steam flow rates of the already activated wells 10 from the steam flow rate indicated by the flow meter 80.

[0065] When the acquisition unit 51 acquires data on the second borehole 10b, the control device 50 performs operations to appropriately change the valve opening X2 of the flow control valve 40b of the second borehole and the pressure ps of the separator 60, and acquires the corresponding wellhead pressure p2 and steam flow rate G2 of the second borehole 10b.

[0066] 5 , the estimation unit 52 of the control device 50 estimates the second function formula f2 using equation (2) from the data of the second well 10b acquired by the acquisition unit 51. When the second function formula f2 is identified for the second well 10b, the steam flow rate G2 of the second well 10b can be estimated from the wellhead pressure p2 of the second well 10b, the valve opening X2 of the flow control valve 40b of the second well, and the pressure ps of the separator 60.

[0067] Next, the process proceeds to step S104, where it is again determined whether or not there is a well 10 that can be activated next. If a third or subsequent well 10 exists and can be activated, steps S105 to S107 can be executed by successively replacing "second" with "third" or subsequent wells. This makes it possible to predict the steam flow rates of all wells 10 that merge into the separator 60. If there is no next well 10 that can be activated, the process ends.

[0068] In this disclosure, the use of terms such as "first," "second," "third," etc. does not imply a particular order, and the inclusion of these terms is to identify individual elements. Furthermore, the use of terms such as "first," "second," "third," etc. does not imply any order or importance; rather, terms such as "first," "second," "third," etc. are used to distinguish one element from another. Terms such as "first," "second," "third," etc. are used herein and elsewhere for illustrative purposes only and are not intended to imply a particular spatial or temporal order. Furthermore, the reference to a first element does not imply the presence of a second element, or vice versa.

[0069] <Additional Notes> The control device, control method, and control program for a geothermal power plant described in the above-described embodiment can be understood, for example, as follows.

[0070] A control device (50) according to a first aspect of the present disclosure is a control device for controlling a geothermal power plant (1) that includes a plurality of wells (10) from which geothermal fluid gushes out, and a separator (60) that separates the geothermal fluid gushes out from the plurality of wells into steam and hot water, and that generates power using the steam separated by the separator. The control device includes an acquisition unit (51) that acquires the wellhead pressure of each of the wells, the pressure of the separator, the valve openings of a plurality of flow control valves (40) provided between the wells and the separator, and the flow rate of the steam separated by the separator, and for each of the wells, deduce a function expression showing a correlation from the wellhead pressure of the well, the pressure of the separator, the valve openings of the flow control valves of the wells, and the flow rate of the steam separated by the separator. and an estimation unit (52) for estimating a pressure of the first well among the plurality of wells, wherein the first well (10a) is started up, and the acquisition unit acquires the wellhead pressure of the first well, the pressure of the separator, the valve opening of the flow control valve (40a) of the first well, and the flow rate of the steam separated by the separator, and the estimation unit estimates a first function equation showing the correlation of the first well and the steam flow rate of the first well, and while the first well is still started up, a second well (10b) is started up, and the acquisition unit acquires the wellhead pressure of the second well, the pressure of the separator, the valve opening of the flow control valve (40b) of the second well, and the flow rate of the steam separated by the separator, and the estimation unit estimates a second function equation showing the correlation of the second well and the steam flow rate of the second well.

[0071] This makes it possible to grasp the steam production volume of each well, which was previously impossible to measure accurately. When the amount of power generated by a steam-driven turbine declines, it is possible to determine which well is declining, even if the separator is shared.

[0072] In the control device of the second aspect of the present disclosure, in the first aspect, the acquisition unit may calculate and acquire the steam production rate of the second well by subtracting the steam production rate of the first well obtained by the first function formula from the value of a flow meter (80) provided at the steam outlet of the separator.

[0073] Even when only one separator is provided for multiple wells, the steam production rate of each well can be obtained from the total steam flow rate by using a function formula.

[0074] The control device of the third aspect of the present disclosure may, in the first or second aspect, adjust the valve opening of the flow control valve of the first well to change the pressure of the separator, and the acquisition unit may link the adjusted valve opening of the flow control valve of the first well to the changed pressure of the separator, and the valve opening of the flow control valve of the first well to the wellhead pressure of the first well corresponding to the change in the pressure of the separator and the steam flow rate of the first well, and the estimation unit may estimate the first function equation based on the adjusted valve opening of the flow control valve of the first well acquired and linked by the acquisition unit, the changed pressure of the separator, the corresponding wellhead pressure of the first well, and the flow rate of the steam separated by the separator.

[0075] By estimating the first function equation for the first well from the variously changed valve opening of the flow control valve, the separator pressure, and the corresponding wellhead pressure and steam flow rate, it is possible to predict the steam flow rate of the first well.

[0076] The control device of the fourth aspect of the present disclosure may be configured in the third aspect to adjust the valve opening of the flow control valve of the second well to change the pressure of the separator, and the acquisition unit may link the adjusted valve opening of the flow control valve of the second well to the changed pressure of the separator, and the valve opening of the flow control valve of the second well to the wellhead pressure of the second well corresponding to the change in the pressure of the separator and the steam flow rate of the second well, and the estimation unit may estimate the second function equation based on the adjusted valve opening of the flow control valve of the second well acquired and linked by the acquisition unit, the changed pressure of the separator, the corresponding wellhead pressure of the second well, and the flow rate of the steam separated by the separator.

[0077] By estimating a second function equation for the second well from variously changed valve openings of the flow control valve, separator pressure, and the corresponding wellhead pressure and steam flow rate, it is possible to predict the steam flow rate of the second well.

[0078] In the control device of a fifth aspect of the present disclosure, in the third or fourth aspect, the estimation unit may use machine learning to estimate the first function formula and the second function formula.

[0079] By using machine learning, highly accurate estimations can be made in a short period of time.

[0080] A control method of a sixth aspect of the present disclosure is a control method for a geothermal power plant including a plurality of wells from which geothermal fluid gushes out, and a separator that separates the geothermal fluid gushes out from the plurality of wells into steam and hot water, and generating power using the steam separated by the separator, the control method including: an acquisition step of acquiring the wellhead pressure of each of the wells, the pressure of the separator, valve apertures of a plurality of flow control valves provided between the wells and the separator, and the flow rate of the steam separated by the separator; and an estimation step of estimating, for each of the wells, a function expression indicating a correlation between the wellhead pressure of the well, the pressure of the separator, the valve apertures of the flow control valves of the wells, and the flow rate of the steam separated by the separator; The method includes a first startup step of starting up the first well, a first acquisition step of acquiring the wellhead pressure of the first well, the pressure of the separator, the valve opening of the flow control valve of the first well, and the flow rate of the steam separated by the separator, a first function equation showing the correlation of the first well, and a first estimation step of estimating the steam flow rate of the first well, a second startup step of starting up a second well while keeping the first well running, a second acquisition step of acquiring the wellhead pressure of the second well, the pressure of the separator, the valve opening of the flow control valve of the second well, and the flow rate of the steam separated by the separator, and a second function equation showing the correlation of the second well, and a second estimation step of estimating the steam flow rate of the second well.

[0081] A control program according to a seventh aspect of the present disclosure causes a computer to execute the control method according to the sixth aspect.

[0082] DESCRIPTION OF SYMBOLS 1 Geothermal power plant 10 Well 10a First well 10b Second well 20 Pressure gauge 20a Pressure gauge of first well 20b Pressure gauge of second well 30, 30a, 30b Opening and closing valve 40 Flow control valve 40a Flow control valve of first well 40b Flow control valve of second well 50 Control device 51 Acquisition unit 52 Estimation unit 55 Output device 60 Separator 70 Separator pressure gauge 80 Flow meter 1100 CPU 1200 Secondary storage device 1300 Main storage device 1500 Communication unit 1800 Bus

Claims

1. A control device for controlling a geothermal power plant comprising a plurality of wells from which geothermal fluid gushes out, and a separator for separating the geothermal fluid gushes out from the plurality of wells into steam and hot water, and for generating electricity using the steam separated by the separator, the control device comprising: an acquisition unit for acquiring the wellhead pressure of each of the wells, the pressure of the separator, the valve openings of a plurality of flow control valves provided between each of the wells and the separator, and the flow rate of the steam separated by the separator; and an estimation unit for estimating, for each of the wells, a function expression showing a correlation between the wellhead pressure of the well, the pressure of the separator, the valve openings of the flow control valves of the well, and the flow rate of the steam separated by the separator; and starting up a first of the plurality of wells; The control device includes: the acquisition unit acquires the wellhead pressure of the first well, the pressure of the separator, the valve opening of the flow control valve of the first well, and the flow rate of the steam separated by the separator; the estimation unit estimates a first function equation indicating the correlation of the first well and the steam flow rate of the first well; the control device starts up a second well while keeping the first well running; the acquisition unit acquires the wellhead pressure of the second well, the pressure of the separator, the valve opening of the flow control valve of the second well, and the flow rate of the steam separated by the separator; and the estimation unit estimates a second function equation indicating the correlation of the second well and the steam flow rate of the second well.

2. The control device described in claim 1, wherein the acquisition unit calculates and acquires the steam production rate of the second well by subtracting the steam production rate of the first well calculated by the first function formula from the value of a flow meter provided at the steam outlet of the separator.

3. The control device described in claim 1, wherein the valve opening of the flow control valve of the first well is adjusted to change the pressure of the separator, the acquisition unit links the valve opening of the flow control valve of the first well after adjustment to the changed pressure of the separator, and the valve opening of the flow control valve of the first well, the wellhead pressure of the first well corresponding to the change in the pressure of the separator, and the steam flow rate of the first well, and the estimation unit estimates the first function equation based on the valve opening of the flow control valve of the first well after adjustment acquired and linked by the acquisition unit, the changed pressure of the separator, the corresponding wellhead pressure of the first well, and the flow rate of the steam separated by the separator.

4. The control device described in claim 3, wherein the valve opening of the flow control valve of the second well is adjusted to change the pressure of the separator, the acquisition unit links the valve opening of the flow control valve of the second well after adjustment to the changed pressure of the separator, and the valve opening of the flow control valve of the second well, the wellhead pressure of the second well corresponding to the change in the pressure of the separator, and the steam flow rate of the second well, and the estimation unit estimates the second function equation based on the valve opening of the flow control valve of the second well after adjustment acquired and linked by the acquisition unit, the changed pressure of the separator, the corresponding wellhead pressure of the second well, and the flow rate of the steam separated by the separator.

5. The control device according to claim 3 or 4, wherein the estimation unit uses machine learning to estimate the first function formula and the second function formula.

6. A control method for a geothermal power plant comprising a plurality of wells from which geothermal fluid gushes out, and a separator that separates the geothermal fluid gushes out from the plurality of wells into steam and hot water, and which generates power using the steam separated by the separator, comprising: an acquisition step of acquiring the wellhead pressure of each of the wells, the pressure of the separator, the valve openings of a plurality of flow control valves provided between the wells and the separator, and the flow rate of the steam separated by the separator; an estimation step of estimating, for each of the wells, a function expression showing a correlation between the wellhead pressure of the well, the pressure of the separator, the valve openings of the flow control valves of the wells, and the flow rate of the steam separated by the separator; and a first startup step of starting up a first of the plurality of wells; A control method executed by a computer, comprising: a first acquisition step of acquiring the wellhead pressure of the first well, the pressure of the separator, the valve opening of the flow control valve of the first well, and the flow rate of the steam separated by the separator; a first estimation step of estimating a first function equation showing the correlation of the first well and the steam flow rate of the first well; a second startup step of starting up a second well while keeping the first well running; a second acquisition step of acquiring the wellhead pressure of the second well, the pressure of the separator, the valve opening of the flow control valve of the second well, and the flow rate of the steam separated by the separator; and a second estimation step of estimating a second function equation showing the correlation of the second well and the steam flow rate of the second well.

7. A control program for causing a computer to execute the control method according to claim 6.

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