JPH04234576A - Hot dry rock heat extractor - Google Patents

Abstract

PURPOSE:To provide a hot dry rock heat extractor which can reduce power of a sealing water pump for injecting water and hold down the quantity of filling water to the minimum in flooding an underground hot dry rock and extracting heat from the rock as hot water. CONSTITUTION:A hot dry rock heat extractor of the present invention is constructed so that the pressure temperature of a geothermal fluid of each production well outlet is detected, and control valves 21, 22 provided on each filling well 2 and each production well 3 outlet are controlled to control the quantity of filling water to each filling well 2 and the extract quatity from each production well 3 so that the condition of the geothermal fluid may become superheated steam or saturated steam.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-temperature rock extraction device for extracting heat from underground high-temperature rock.

0002

[Prior Art] The conventional method of utilizing geothermal energy is to drill a well into high-temperature steam or groundwater that exists underground (this underground area is called a geothermal reservoir), and then use it to generate geothermal steam or geothermal energy. It was supposed to be extracted and used in the form of water.

However, there are places underground where there are hot rocks but no water veins, and in such places heat cannot be extracted in the form of geothermal steam or geothermal water. Therefore, in order to utilize such geothermal resources, several wells are drilled in the high-temperature rock body, and after creating cracks between the wells using water pressure or other means, water is drained from one well. Techniques are being developed to create so-called engineered geothermal reservoirs by injecting, heating in cracks and extracting from other wells.

[0004] This technology has not yet been established;
Therefore, although there is no fixed method, the general concept is that water injected into an injection well is extracted from a production well in the form of pressurized hot water and used as a high value-added It is power generation.

FIG. 2 shows such a power generation system. As shown in FIG. 2, a plurality of injection wells 2a, 2b and production wells 3a, 3b are dug toward the high-temperature rock body 1 existing underground, and measures such as applying high water pressure to the production wells 3a, 3b are used. Each well is connected by a large number of cracks 4.

[0006] The water injected by the water injection pumps 5a and 5b is
While flowing in this crack 4, it is warmed by the heat of the high-temperature rock and comes out from the production wells 3a, 3b as high-temperature hot water. This hot water is put into a flasher 6, and the saturated steam 7 obtained by flashing is led to a turbine 8 to generate power. A generator 9 is coupled to the turbine 8 to generate electricity.

[0007] The exhaust gas of the turbine 8 flows into a condenser 10;
It is cooled by the cooling water 11 and returns to water. This condensate 12 is sent by a condensate pump 13 to water injection pumps 5a and 5b. Most of the hot water that has not been turned into steam by the flasher 6 is lowered in temperature and becomes low-temperature hot water 14, which is circulated to the water injection pumps 5a and 5b without being particularly utilized.

If all of the cracks 4 in the high-temperature rock body 1 are completely sealed, the entire amount of injected water should circulate to the ground, but some of the cracks 4 are in the high-temperature rock body 1. Usually, some of the injected water flows somewhere underground, and some percentage is lost to the outside of the system. Therefore, since the water in the system will decrease if left as is, an amount of make-up water 15 commensurate with the amount flowing out of the system is replenished into the system from a water source (not shown) using the make-up water pump 16. Actually, there are many devices in the apparatus other than those mentioned above, but descriptions of those not directly related to the present invention are omitted.

[0009] In this way, in order to use the pressurized hot water extracted from the production well for power generation, the pressurized hot water is led to the flasher,
A portion of the water is flashed (boiled under reduced pressure) and converted into steam, which is then used to generate power in a steam turbine to drive a generator.

0010

[Problem to be solved by the invention] However, in that case,
Most of the extracted pressurized hot water remains as hot water with a lower temperature, so it will be injected into the injection well again and circulated between the flasher and the high-temperature rock body. Since a considerably large amount of pump power is required for this hot water circulation, it is important to reduce this power.

[0011] Furthermore, not all of the water injected from the injection well can be recovered from the production well. If a crack exists that reaches the outer edge of the rock, water that flows into the crack will seep out of the rock, reducing the amount of water in the system. Therefore, it is necessary to replenish the amount for this phenomenon, but geothermal areas like this are not necessarily blessed with a source of replenishment water, so in areas where water is scarce, procuring replenishment water is a problem. However, there may be cases where extraction of heat from high-temperature rock bodies is abandoned because there is no prospect of replenishment water. An object of the present invention is to provide a high-temperature rock heat extraction device that can reduce the power of a water injection pump and the amount of make-up water. [Structure of the invention]

0012

[Means for Solving the Problems] In the present invention, the amount of water injected into each injection well and the amount extracted from each production well are controlled so that the state of the geothermal fluid at the outlet of each production well becomes superheated steam or saturated steam. By controlling, the above purpose is achieved.

[0013]

[Effect] If the amount of water injected into each injection well is controlled so that the state of the geothermal fluid at the outlet of each production well becomes superheated steam or saturated steam, compared to a method in which it is circulated as hot water, it is possible to The water injection amount will be significantly reduced. As a result, the power required for the water injection pump is reduced, and the flow rate from the hot rock body is also reduced in accordance with the decrease in the flow rate inside the hot rock body.

[0014]

[Example] An example of the present invention will be shown. In the present invention, detectors 17a and 17b for measuring the pressure and temperature of the geothermal fluid are provided at the exits of the production wells 3a and 3b, and the output signals are sent to the calculator 1.
Send to 8. In the computing unit 18, each production well 3a, 3b
The relationship between the state of the geothermal fluid and saturated steam is calculated for each, and the controller 19 is used to adjust each regulating valve 20a, 20b, 21a, 2 so that saturated steam is produced at the outlet of the production wells 3a, 3b.
Controls the opening degree of 1b.

At this time, the computing unit 18 calculates the positional relationship of the injection wells 2a, 2b and the production wells 3a, 3b within the high-temperature rock body 1, the state of the cracks 4 between them, the temperature situation within the high-temperature rock body 1, etc. The calculation is executed based on a calculation program using the information as judgment material, and a signal is output to the controller 19.

As described above, in the present invention, since saturated steam is obtained from the high-temperature rock body 1, this steam is passed through the steam-water separator 22 to remove unexpected mixed moisture before flowing into the turbine 8. The water separated by the steam-water separator 22 is received by a drain pot 23, and then combined with condensate 12 and make-up water 15 and circulated to the water injection pumps 5a and 5b.

In the present invention, since the geothermal fluid obtained from the production wells 3a and 3b is saturated steam 7, almost the entire amount of the obtained fluid is passed to the turbine 8 and is not used, but is sent to the injection well 2a.
, 2b. This relationship varies depending on temperature conditions, but as a typical example, production well 3
1000 t/h of geothermal fluid at 240°C was obtained from a and 3b at a pressure of 35ata, and the temperature was 150°C with flasher 6.
If saturated steam 7 with a pressure of 4.9 ata is generated, the amount of saturated steam 7 generated is only 192 t/h,
The remaining 808 t/h, in fact 80.8%, circulates to the injection wells 2a and 2b without being utilized.

Furthermore, the leakage loss of water in the high-temperature rock body 1 is related to the amount of water flowing inside the high-temperature rock body 1, and if it is proportional to the amount of water injected into the injection wells 2a and 2b. If it is 20% of the injection volume, use 1000 as above.
t/h, the amount of water injected into the injection wells 2a and 2b is 1250 t/h, and the amount of makeup water 15 is 250 t/h.
It also goes up to t/h.

On the other hand, when compared under the same conditions, in the present invention, 192 t/h of saturated steam can be obtained directly from the production wells 3a and 3b, so the amount of water injected into the injection wells 2a and 2b is 240 t/h.
t/h, and the amount of makeup water 15 is only 48 t/h.

Since the required power of the water injection pumps 5a and 5b is approximately proportional to the discharge amount, it can be reduced to 1250:240, ie, 1/5.2 in the calculation example of steam. Further, the amount of make-up water 15 is 250:48, which can also be reduced to 1/5.2.

[0021] Conventionally, there have been experimental examples in which hot water was extracted from the production wells 3a and 3b in a state where it was mixed with steam, and in such a state, the above-mentioned reduction rate would decrease by the amount of steam; In the experimental example shown in FIG. 2, the situation was just that the steam was mixed in at the end, but it was not actively controlled as in the present invention. Injection well 2a in Figures 1 and 2
, 2b, and two production wells 3a and 3b, but any number of wells may be used and the number does not have to be the same. Although the power generation plant has been described using an example of a single flash type with one flash, the same applies to a case of a double flash type with two flashes.

The state of the geothermal fluid coming out of the production wells 3a and 3b may be superheated steam instead of saturated steam. In addition, wells that produce saturated steam and wells that produce superheated steam may coexist, and in some cases, such operating conditions may be intentionally set in order to efficiently extract heat from the high-temperature rock body 1. It is also possible to create Furthermore, each injection well 2a,
The amount of water injected into 2b is not necessarily controlled by the water inlet valves 20a and 20.
It is not necessary to control the opening degree of b, and it is also possible to use the rotation speed control of the water injection pump or the like.

[0023]

According to the present invention, by controlling the amount extracted from each production well outlet, the amount injected into a hot rock body can be significantly reduced compared to a method in which hot water is circulated. As a result, the power required for the water injection pump is reduced, and the amount of leakage from the hot rock body, ie, the amount of make-up water into the system, is also reduced.

[0024] This effect also produces the secondary effect of reducing the scale of the water injection system and make-up water system equipment, and also contributes to increasing the number of locations where high-temperature rock power generation can be constructed and improving the economic efficiency of the system.

[Brief explanation of the drawing]

[Fig. 1] A block diagram showing an embodiment of a high-temperature rock heat extraction device using the present invention.

[Figure 2] Block diagram showing an example of a conventional high-temperature rock heat extraction device

[Explanation of symbols]

1...High-temperature rock body 2...Injection well
3...Production well 4...Crack 5...Water injection pump 6...Flasher 7
...Saturated steam 8...Turbine 9...Generator 10...Condenser
11...Cooling water 12...Condensate water 13...Condensate pump 14...Low temperature hot water 15...Makeup water 16...Makeup water pump 17...Pressure temperature detector 18...Calculator 19...Controller 20, 21...Adjustment valve

Claims (1)

[Claims] Claim 1: In an artificial geothermal reservoir consisting of a plurality of injection wells, production wells, and cracks connecting the wells in the hot rock body underground, the state of geothermal fluid at the outlet of each production well. A high-temperature rock heat extraction device characterized by controlling the amount of water injected into each injection well and the amount extracted from each production well so that the water becomes superheated steam or saturated steam.