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

Abstract

This invention provides a control device, control method, and control program for a geothermal power plant that can accurately determine the amount of steam produced in a well. [Solution] A control device 50 for controlling a geothermal power plant that generates electricity, comprising a plurality of wells from which geothermal fluid is ejected, and a separator that separates the geothermal fluid ejected from each well into steam and hot water, wherein the control device 50 comprises an acquisition unit 51 that acquires information for each well, and an estimation unit 52 that estimates a function equation showing the correlation from the wellhead pressure, separator pressure, valve opening of the well flow control valve, and the flow rate of the steam separated by the separator for each well, wherein the first well among the plurality of wells is started, the acquisition unit 51 acquires information for the first well, and the estimation unit 52 estimates a first function equation showing the correlation of the first well, and while the first well is still running, the second well is started, the acquisition unit 51 acquires information for the second well, and the estimation unit 52 estimates a second function equation showing the correlation of the second well.

Description

Technical Field

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

Background Art

[0002] In a geothermal power generation plant, steam separated from geothermal fluid (mainly a mixed fluid of steam and hot water) ejected from a well is introduced into a steam turbine for power generation. Therefore, in order to combine and utilize the geothermal fluid ejected from a plurality of wells, well management is performed to control the flow rate of the ejected geothermal fluid based on the well characteristics (characteristics of the pressure and flow rate of the ejected fluid) in each well, and to maximize the generated electric power. In well management, changes in well characteristics are grasped, and the flow rate of the geothermal fluid ejected from the well is made appropriate (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the invention of Patent Document 1, the well characteristics are grasped when a separator corresponding to each well is provided. However, in a general geothermal power generation plant, one separator is often provided for a plurality of wells in order to reduce equipment costs.

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

[0006] This disclosure is made in view of these circumstances and aims to provide a control device, control method, and control program for a geothermal power plant that can accurately grasp the amount of steam produced in a well while keeping costs down. [Means for solving the problem]

[0007] To solve the above problems, the control device, control method, and control program for the geothermal power plant disclosed herein employ the following means. The control device for a geothermal power plant according to this disclosure comprises a plurality of wells from which geothermal fluid is ejected, and a separator that separates the geothermal fluid ejected from the plurality of wells into steam and hot water, and is a control device for controlling a geothermal power plant that generates electricity using the steam separated by the separator, wherein the control device includes an acquisition unit that acquires the wellhead pressure of each well, the pressure of the separator, the valve opening of a plurality of flow control valves provided between each well and the separator, and the flow rate of the steam separated by the separator, and for each well, a function equation showing the correlation between the wellhead pressure of the well, the pressure of the separator, the valve opening of the flow control valve of the well and the flow rate of the steam separated by the separator. The system includes an estimation unit that estimates the following: The system starts up the first of the plurality of wells, 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 functional equation showing the correlation of the first well and the steam flow rate of the first well. The system starts up the second well while the first well is still running, 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 functional equation showing 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 is ejected, and a separator that separates the geothermal fluid ejected from the plurality of wells into steam and hot water, wherein power is generated using the steam separated by the separator, the method comprising: an acquisition step of acquiring the wellhead pressure of each well, the pressure of the separator, the valve opening of a plurality of flow control valves provided between each well and the separator, and the flow rate of the steam separated by the separator; and an estimation step of estimating a function equation showing a correlation between the wellhead pressure of the well, the pressure of the separator, the valve opening of the flow control valve of the well, and the flow rate of the steam separated by the separator for each well, wherein among the plurality of wells, The system comprises a first starting step of starting the aforementioned 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, a first estimation step of estimating the steam flow rate of the first well, a second starting step of starting the second well while the first well is still 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, 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, and is executed by a computer.

[0009] The control program disclosed herein causes a computer to execute the control method described above. [Effects of the Invention]

[0010] According to this disclosure, it is possible to accurately determine the amount of steam produced in each well, which could not be measured accurately until now. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows a geothermal power plant equipped with a control device in some embodiments of the present disclosure. [Figure 2]This figure shows an example of the hardware configuration of a control device in some embodiments of the present disclosure. [Figure 3] This figure shows an example of the functions of a control device in some embodiments of the present disclosure. [Figure 4] This figure shows the relationship between differential pressure and steam flow rate in a geothermal power plant in some embodiments of the present disclosure. [Figure 5] This figure shows the control flow of a control device in some embodiments of the present disclosure. [Figure 6] This figure shows the time course of steam flow rate in a geothermal power plant in some embodiments of the present disclosure. [Modes for carrying out the invention]

[0012] Below, an embodiment of the control device, control method, and control program for a geothermal power plant according to this disclosure will be described with reference to the drawings. The control device 50 can be broadly 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 with the configuration described below.

[0013] Figure 1 shows a geothermal power plant equipped with a control device in several embodiments of the present disclosure. In this disclosure, a case in which multiple wells 10 are provided is described, for example, when two wells 10 are provided. The geothermal power plant 1 shown in Figure 1 is, for example, a flash cycle type geothermal power plant 1, but the control device 50 can be similarly applied to other configurations of geothermal power plants 1, such as a binary cycle type. In addition, in Figure 1, for example, two wells 10 are provided and one separator 60 is provided, but the present disclosure can be applied as appropriate, not limited to the above configuration and number of components.

[0014] As shown in Figure 1, the geothermal power plant 1 comprises a well 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] In the geothermal power plant 1, a plurality of wells 10 are included, and a pressure gauge 20, an on-off valve 30, and a flow control valve 40 are provided for each well 10. In the present disclosure and FIG. 1, the case where two wells 10 (the first well 10a and the second well 10b) are included is disclosed, but three or more wells 10 may be included, and the number thereof is not limited.

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

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

[0018] Also, on the geothermal fluid transport pipe, a pressure gauge 20 for measuring the wellhead pressure (ejection pressure) is provided on the upstream side of the geothermal fluid flow of the flow control valve 40. The pressure gauge 20 measures the pressure of the geothermal fluid ejected from the well 10. Note that an on-off valve 30 may be provided on the upstream side of the geothermal fluid flow on the geothermal fluid transport pipe (near the wellhead of the well 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 (gas-liquid separator) that separates the geothermal fluid, which is a two-phase mixed fluid supplied by the geothermal fluid transport pipe, into steam and hot water. The hot water separated by the separator 60 is guided to the hot water pipe, and the steam separated by the separator 60 is guided to the steam pipe. The flow rate of the steam guided to the steam pipe is measured by a flow meter 80 provided on the steam pipe. The separator pressure gauge 70 is provided on 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 a reduction well (not shown). By returning the hot water to the underground geothermal reservoir through the reduction well, depletion of the geothermal fluid in the underground geothermal reservoir is suppressed. The hot water separated by the separator 60 may be pumped to the reduction well via a pump (not shown). When it is possible to pump the hot water to the reduction well by its own pressure, the pump may be omitted or its capacity may be reduced. The flow rate of the hot water sent to the reduction well is measured by a flow meter (not shown) provided on the hot water pipe.

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

[0022] FIG. 2 is a diagram showing an example of the hardware configuration of a control device in some embodiments of the present disclosure. As shown in FIG. 2, the control device (Controller) 50 is a computer system, and for example, includes 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 mass storage device, and a communication unit 1500 for connecting to a network or the like. Note that a solid state drive (SSD) may be used as the mass storage device. These components are connected via a bus 1800.

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

[0024] The main memory 1300 consists of writable memory such as cache memory and RAM (Random Access Memory), and is used as a work area for reading the CPU 1100's executable program and writing processing data by the executable program.

[0025] The secondary storage device 1200 is a non-transitory computer-readable storage medium. Examples of secondary storage devices 1200 include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memory. Examples of secondary storage devices 1200 include ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), and flash memory. The secondary storage device 1200 stores, for example, an OS for controlling the entire information processing device such as Windows®, iOS®, and Android®, a BIOS (Basic Input / Output System), various device drivers for hardware operation of peripheral devices, various application software, and various data and files. Furthermore, the secondary storage device 1200 stores programs for implementing various processes and various data required to implement those processes. Multiple secondary storage devices 1200 may be provided, and the aforementioned programs and data may be divided and stored in each secondary storage device 1200.

[0026] Furthermore, the control device 50 may include an input unit consisting of a keyboard or mouse, and a display unit consisting of a liquid crystal display device or the like for displaying data. It may also include a notification unit that includes a display unit and outputs lights, sounds, and especially alarm sounds, such as a speaker.

[0027] Figure 3 is a diagram illustrating an example of the functions of a control device in several embodiments of the present disclosure. As shown in Figure 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 are stored in the form of a program in the secondary storage device 1200 (see Figure 2), for example. The CPU (processor) 1100 (see Figure 2) reads this program into the main memory 1300 (see Figure 2) and performs information processing and calculations to realize various functions. The program may be pre-installed in the secondary storage device 1200, provided stored in other non-temporary computer-readable storage media, or distributed via wired or wireless communication. Examples of non-temporary computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memory.

[0029] The acquisition unit 51 shown in Figure 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 of each flow control valve 40, and the steam flow rate of each well 10.

[0030] The estimation unit 52 estimates a functional equation that shows the correlation between each well 10 based on the information acquired by the acquisition unit 51.

[0031] The function expression showing 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 functional equation showing the correlation between each well 10 as follows: For example, consider the case where two wells 10 (the first well 10a and the second well 10b) are connected to one separator 60 (see Figure 1).

[0033] Let p1 be the measured wellhead pressure of the first well in Figure 1 as measured by pressure gauge 20a, and p2 be the measured wellhead pressure of the second well as measured by pressure gauge 20b. Let ps be the measured pressure of separator 60 as measured by separator pressure gauge 70. Let X1 be the valve opening of flow control valve 40a in the first well, and X2 be the valve opening of flow control valve 40b in the second well. At this time, if G1 is the steam flow rate of the first well 10a and G2 is the steam flow rate of the second well 10b, then the following relationships (1) and (2) will hold.

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

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

[0036] The geothermal fluid ejected from a typical well 10 is often a saturated gas-liquid two-phase flow. Therefore, equations (1) and (2) should ideally consider the hydrothermal water flow rate in addition to the steam flow rate. However, the inventor discovered through data analysis that the relationship between equations (1) and (2) does not depend on the hydrothermal water flow rate (or its influence is negligibly small). This is thought to be because the specific enthalpy of the geothermal fluid does not change in the short term, that is, the state of the geothermal reservoir does not change in the short term, so the ratio of hydrothermal water to steam remains constant or changes only slightly.

[0037] Normally, the presence of hot water increases the pressure loss compared to the case of steam alone. However, since the ratio of hot water to steam is uniquely determined, the function fn is determined including the effect of the hot water.

[0038] It is generally known that if the fluid in 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 (3) can be derived from Bernoulli's theorem for, for example, the first well 10a. 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]

number

[0040] In equation (3), ρ represents the fluid density (vapor density). Solving equation (3) for G1 yields equation (4).

[0041]

number

[0042] Equation (1) is specifically expressed as equation (4). Equation (2) can also be expressed in a similar form. The apparent pressure loss coefficient ζ is affected by the ratio of hot water to steam, as mentioned above. Since 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 geothermal power plant 1. Although equation (4) ignores the compressibility of steam, in practice, the apparent pressure loss coefficient ζ is determined by including a correction factor for the compressibility of steam. Therefore, in this disclosure, the function equation f, namely the first function equation f1 in equation (1) and the second function equation f2 in equation (2), is determined using the operating data.

[0043] Figure 4 shows the relationship between differential pressure and steam flow rate in a geothermal power plant in some embodiments of the present disclosure. In Figure 4, the vertical axis represents the steam flow rate G1, and the horizontal axis represents the differential pressure ps-p1. In this 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 Figure 4, the triangles (△) indicate the value when the valve opening of the flow control valve 40a of the first well is Z1, and the circles (○) indicate the value when the valve opening of the flow control valve 40a of the first well is Z1'. Here, the valve opening Z1' is a value greater than the valve opening Z1. In Figure 4, the dashed line shows the trend of values ​​when the valve opening is Z1, and the solid line shows the trend of values ​​when the valve opening is Z1'.

[0044] As shown in Figure 4, it can be seen that the steam flow rate G1 has a relationship that is close to the square root of the differential pressure ps-p1. This is also consistent with equation (4) mentioned above.

[0045] As shown in Figure 4, the steam flow rate G1 corresponding to the differential pressure ps-p1 when the valve opening is Z1 is higher than the steam flow rate G1 corresponding to the differential pressure ps-p1 when the valve opening is Z1. From Figure 4, it can be seen that the steam flow rate increases as the valve opening increases.

[0046] Figure 5 shows the control flow of a control device in some embodiments of the present disclosure. The control device 50 starts any of the multiple wells 10 that are able to be started. In this disclosure, the first well 10a is started (S101). The well 10 to be started may be any well 10 that is able to be started.

[0047] In geothermal power plant 1, it is common practice to start up the wells 10 one by one during the restart process after production has been stopped for periodic maintenance or other reasons. This control flow can be implemented by taking advantage of such opportunities.

[0048] Next, in step S102, the acquisition unit 51 of the control device 50 acquires data for the first well 10a. The acquisition unit 51 acquires the following data for the first well 10a: the wellhead pressure of the first well 10a, the pressure of the separator 60, the valve opening 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 opening of the flow control valve 40a of the first well is acquired from the flow control valve 40a of the first well or from 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 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 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 from the first well 10a by the acquisition unit 51, the control device 50 appropriately changes 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 atmospheric release valve (not shown) of an atmospheric release facility (not shown) installed 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 the first function equation f1 using equation (1) from the data of the first well 10a acquired by the acquisition unit 51. Once the first function equation f1 is determined for the first well 10a, the steam flow rate G1 of the first well 10a can be estimated using the wellhead pressure p1, the valve opening X1 of the flow control valve 40a of the first well, and the pressure ps of the separator 60.

[0052] As described above, the estimation unit 52 estimates the first function equation f1 using data obtained 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.

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

[0054] Next, in step S104, the control device 50 determines whether there is a well 10 that can be started next. If it is determined that there is a well 10 that can be started next, the process proceeds to step S105. On the other hand, if it is determined that there is no well 10 that can be started next, the process ends.

[0055] In step S105, the control device 50 starts the second well 10b. In this case, any well 10 may be used as long as it is startable. Alternatively, the operator may start the second well 10b manually.

[0056] Next, in step S106, the acquisition unit 51 of the control device 50 acquires data for the second well 10b. The acquisition unit 51 acquires the following data for the second well 10b: the wellhead pressure of the second well 10b, the pressure of the separator 60, the valve opening 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 opening of the flow control valve 40b of the second well is acquired from the flow control valve 40b of the second well or from 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 the function f1, from the value measured by 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] Figure 6 shows the time course of steam flow rate in a geothermal power plant in some embodiments of the present disclosure. In Figure 6, each vertical axis represents steam flow rate, and each horizontal axis represents time. In Figure 6, the solid line shows the steam flow rate of the geothermal power plant 1 detected by the flow meter 80, and the dashed line shows the steam flow rate of the first well 10a.

[0059] In Figure 6(a), only the first well 10a is in operation between time t0 and t1. Therefore, the steam flow rate shown by the flow meter 80 is the steam flow rate of the first well 10a.

[0060] At time t1, the second well 10b is started in addition to the first well 10a. Between time t1 and t2, both the first well 10a and the second well 10b are in operation. Therefore, the steam flow rate shown 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. From time t2 onward, only the first well 10a is in operation. Therefore, the steam flow rate shown by the flow meter 80 is the steam flow rate of the first well 10a.

[0062] Here, by performing steps S101 to S103 in Figure 5, the steam flow rate of the first well 10a is derived from the first functional equation f1. The derived steam flow rate of the first well 10a is shown by the dashed line in Figure 6(b).

[0063] As mentioned above, the first well 10a and the second well 10b are in operation between time t1 and t2. The steam flow rate shown 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. Therefore, 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 shown by the flow meter 80.

[0064] In other words, the shaded area in Figure 6(b), obtained by subtracting the steam flow rate of the first well 10a from the steam flow rate indicated by the flow meter 80, represents the steam flow rate of the second well 10b. Thus, 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] In acquiring data from the second well 10b by the acquisition unit 51, the control device 50 appropriately changes the valve opening X2 of the flow control valve 40b of the second well and the pressure ps of the separator 60, and acquires the corresponding wellhead pressure p2 and steam flow rate G2 of the second well 10b.

[0066] Next, in step S107 of Figure 5, the estimation unit 52 of the control device 50 estimates the second function equation f2 using equation (2) from the data of the second well 10b acquired by the acquisition unit 51. Once the second function equation f2 is determined for the second well 10b, the steam flow rate G2 of the second well 10b can be estimated using the wellhead pressure p2, 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 determined again whether there are any more wells 10 that can be started. If there are third and subsequent wells 10 that can be started, the "second" in steps S105 to S107 should be replaced with "third" and subsequent wells in sequence. This makes it possible to predict the steam flow rate of all wells 10 that are connected to the separator 60. If there are no more wells 10 that can be started, the process is terminated.

[0068] In this disclosure, the use of expressions such as “first,” “second,” and “third” does not suggest a particular order; these expressions are included solely to identify individual elements. Furthermore, the use of expressions such as “first,” “second,” and “third” does not indicate any arbitrary order or importance; more precisely, expressions such as “first,” “second,” and “third” are used to distinguish one element from another. Expressions such as “first,” “second,” and “third” are used solely to indicate purpose in this specification and elsewhere, and are not intended to indicate a particular spatial or temporal order. Moreover, the notation of the first element does not suggest the existence of the second element, and vice versa.

[0069] <Note> The control device, control method, and control program for the geothermal power plant described in the embodiments above 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) which includes a plurality of wells (10) from which geothermal fluid is ejected, and a separator (60) that separates the geothermal fluid ejected from the plurality of wells into steam and hot water, and which generates electricity using the steam separated by the separator, wherein the control device includes an acquisition unit (51) that acquires the wellhead pressure of each well, the pressure of the separator, the valve opening of a plurality of flow control valves (40) provided between each well and the separator, and the flow rate of the steam separated by the separator, and for each well, the acquisition unit that derives a function equation showing the correlation from the wellhead pressure of the well, the pressure of the separator, the valve opening of the flow control valve of the well, and the flow rate of the steam separated by the separator. The system includes an estimation unit (52) that determines the flow rate of the steam separated by the separator. The system starts up the first well (10a) among a plurality of wells, 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. The estimation unit estimates a first functional equation showing the correlation of the first well and the steam flow rate of the first well. With the first well running, the system starts up the second well (10b), 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. The estimation unit estimates a second functional equation showing the correlation of the second well and the steam flow rate of the second well.

[0071] This technology allows us to determine the amount of steam produced in each well, which was previously impossible to measure accurately. It also allows us to identify which wells are experiencing a decline in power generation from steam-driven turbines, even if the separators are 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 amount of the second well by subtracting the steam production amount of the first well, which is obtained by the first function equation, from the value of the 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 of each well can be obtained from the total steam flow rate by using a functional equation.

[0074] A control device according to a 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, the acquisition unit links the adjusted valve opening of the flow control valve of the first well with the changed pressure of the separator, and the wellhead pressure of the first well and the steam flow rate of the first well corresponding to the change in the valve opening of the flow control valve of the first well and the pressure of the separator, and the estimation unit estimates 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, and the corresponding wellhead pressure of the first well and the steam flow rate separated by the separator.

[0075] By estimating a first functional equation in the first well from the valve opening of the flow control valve and the separator pressure, which are varied in various ways, and the corresponding wellhead pressure and steam flow rate, it becomes possible to predict the steam flow rate in the first well.

[0076] A control device according to a fourth aspect of the present disclosure may, in the third aspect, adjust the valve opening of the flow control valve of the second well to change the pressure of the separator, the acquisition unit links the adjusted valve opening of the flow control valve of the second well with the changed pressure of the separator, and the wellhead pressure of the second well and the steam flow rate of the second well corresponding to the change in the valve opening of the flow control valve of the second well and the pressure of the separator, and the estimation unit estimates 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 steam flow rate separated by the separator.

[0077] By estimating a second function equation in the second well from the valve opening of the flow control valve and the separator pressure, which are varied in various ways, and the corresponding wellhead pressure and steam flow rate, it becomes possible to predict the steam flow rate in the second well.

[0078] In the control device according to the fifth aspect of this disclosure, the estimation unit may use machine learning in estimating the first and second functional equations, as in the third or fourth aspect of the disclosure.

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

[0080] A control method according to a sixth aspect of the present disclosure is a control method for a geothermal power plant comprising a plurality of wells from which geothermal fluid is ejected, and a separator that separates the geothermal fluid ejected from the plurality of wells into steam and hot water, wherein power is generated using the steam separated by the separator, the method comprising: an acquisition step of acquiring the wellhead pressure of each well, the pressure of the separator, the valve opening of a plurality of flow control valves provided between each well and the separator, and the flow rate of the steam separated by the separator; and an estimation step of estimating a function equation showing a correlation between the wellhead pressure of the well, the pressure of the separator, the valve opening of the flow control valve of the well, and the flow rate of the steam separated by the separator for each well, wherein among the plurality of wells The system comprises a first starting step of starting 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, a first estimation step of estimating the steam flow rate of the first well, a second starting step of starting the second well while the first well is still 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, 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, and is executed by a computer.

[0081] The control program of the seventh aspect of this disclosure causes a computer to execute the control method described in the sixth aspect. [Explanation of Symbols]

[0082] 1. Geothermal power plant 10 wells 10a First well 10b Second well 20 Pressure gauges 20a Pressure gauge for the first well 20b Pressure gauge for the second well 30, 30a, 30b Shut-off valves 40 Flow control valve 40a Flow control valve for the first well 40b Flow control valve for the second well 50 Control device 51 Acquisition Department 52 Estimation part 55 Output device 60 Separators 70 Separator pressure gauge 80 flow meter 1100 CPU 1200 Secondary storage 1300 Main storage 1500 Communications Department 1800 Bus

Claims

1. A control device for controlling a geothermal power plant comprising a plurality of wells from which geothermal fluid is ejected, and a separator that separates the geothermal fluid ejected from the plurality of wells into steam and hot water, wherein the steam separated by the separator is used to generate electricity, The control device is An acquisition unit that acquires the wellhead pressure of each of the aforementioned wells, the pressure of the separator, the valve opening of a plurality of flow control valves provided between each of the aforementioned wells and the separator, and the flow rate of the steam separated by the separator. For each of the aforementioned wells, the system includes an estimation unit that estimates a function equation showing a correlation between the wellhead pressure, the separator pressure, the valve opening of the flow control valve of the well, and the flow rate of the steam separated by the separator. The first of the multiple wells is started, 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 functional equation showing the correlation of the first wells and the steam flow rate of the first well. While the first well is running, the second well is started. 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. The estimation unit includes a second functional equation that shows the correlation of the second wells, and a control device that estimates the steam flow rate of the second well.

2. The control device according to claim 1, wherein the acquisition unit calculates and acquires the steam production amount of the second well by subtracting the steam production amount of the first well, which is obtained by the first functional equation, from the value of the flow meter provided at the steam outlet of the separator.

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

4. The valve opening of the flow control valve in the second well is adjusted to change the pressure in the separator, The acquisition unit links the valve opening of the flow control valve of the second well after adjustment with the pressure of the separator after the change, and the wellhead pressure of the second well and the steam flow rate of the second well corresponding to the change in the valve opening of the flow control valve of the second well and the pressure of the separator. The control device according to claim 3, wherein the estimation unit estimates the second function equation based on the valve opening of the flow control valve of the second well after adjustment, which has been acquired and linked by the acquisition unit, the pressure of the separator after change, 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 in estimating the first and second function equations.

6. A control method for a geothermal power plant comprising a plurality of wells from which geothermal fluid is ejected, and a separator that separates the geothermal fluid ejected from the plurality of wells into steam and hot water, wherein power is generated using the steam separated by the separator, An acquisition step to acquire the wellhead pressure of each of the aforementioned wells, the pressure of the separator, the valve opening of a plurality of flow control valves provided between each of the aforementioned wells and the separator, and the flow rate of the steam separated by the separator. For each of the aforementioned wells, the system includes an estimation step of estimating a functional equation showing a correlation between the wellhead pressure, the separator pressure, the valve opening of the flow control valve in the well, and the flow rate of the steam separated by the separator. A first starting step of starting the first well among the multiple wells, A first acquisition step for 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 functional equation showing the correlation of the first well, and a first estimation step for estimating the steam flow rate of the first well, A second starting step involves starting the second well while the first well is still running, A second acquisition step for 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, A control method performed by a computer, comprising a second functional equation showing the correlation of the second well, and a second estimation step for estimating the steam flow rate of the second well.

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

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