JPH08165879A - Borehole flow velocity measuring device - Google Patents

Abstract

PURPOSE: To provide a borehole flow velocity measuring device measuring the velocity of a high-pressure high-temperature fluid in a boring hole with good accuracy. CONSTITUTION: A propeller 34 is arranged in the underground flowing water, the water current velocity is converted into the rotation of the propeller 34, and the rotation is transmitted to a slit disk 33. The slit disk 33 interrupts the light fed through the path constituted of the first optical fiber 12, the first lens 25, a glass window 29 provided on part of the wall of a pressure container 22, a reflector 30, the second lens 26, and the second optical fiber 15, coverts it into the intermittent modulating signal of light, and feeds it to a photodetector. The intermittent modulating signal of light is converted into the electrical pulse signal, and the water current velocity is measured by counting the pulse signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the flow velocity of groundwater in a borehole for hot rock mass power generation.

[0002]

2. Description of the Prior Art In hot rock power generation, two borings are carried out to a depth where the underground temperature is high around 3000m, and pressure is applied between both boring holes to make many small cracks in the bedrock. It is based on the principle that apparent heat exchangers can be formed in the bedrock if the boreholes are connected by cracks in the bedrock. That is, if water having a temperature lower than that of one of the boring holes is injected, extremely high temperature hot water is obtained from the other boring hole, and it becomes possible to generate electric power by using this thermal energy. Since the boiling point of water rises due to the high pressure at the depth where the heat exchanger is formed,
It does not become steam but exists as hot water.

The water injected under pressure from one of the boring holes is recovered above the ground by the other boring hole after passing through the heat exchanger in the bedrock, so that the flow velocity as a whole can be measured. However, regarding which part of the region where the cracks of the rock as a heat exchanger exist, the water could not be specified except by directly measuring the flow velocity at each depth.

[0004]

The velocity of a high temperature fluid can be measured on the ground by using a non-contact measurement method such as Doppler measurement. However, in order to measure the velocity in a high temperature fluid under high pressure such as in a deep boring hole, the temperature of ordinary electronic circuit components using semiconductors exceeds the operating limit, so there is almost no measurement method. It was a situation.

Therefore, an object of the present invention is to provide an in-hole flow velocity measuring device for accurately measuring the velocity of a high-pressure high-temperature fluid in a boring hole.

[0006]

According to the present invention, there is provided a first optical fiber for guiding light from a light source into a pressure vessel arranged in a borehole, and an output from one end of this first optical fiber. A first lens disposed in the pressure resistant container so as to expand the reflected light into parallel rays, and the pressure resistant container so as to guide the parallel light emitted from the first lens to the outside of the pressure resistant container. Of the pressure-resistant container so that the parallel light guided to the outside of the pressure-resistant container through the light-transmitting window is guided again into the pressure-resistant container through the light-transmitting window. A reflecting mirror arranged outside the container, and a second mirror arranged inside the pressure resistant container so as to receive and focus the parallel light guided by the reflecting mirror into the pressure resistant container.
Lens, a second optical fiber that receives the light converged by the second lens and guides the received light to a photodetector, and the first lens to the second optical fiber outside the pressure vessel. A turntable which is rotatably arranged across the optical path leading to the lens and in which light-transmitting parts and light-shielding parts are alternately arranged in the direction of rotation, and a basement which is fixed to the rotary shaft of the turntable and flows outside the pressure vessel. An impeller rotatably arranged by running water, wherein the photodetector measures the flow velocity of the groundwater downstream from an intermittent optical signal from the second optical fiber. The device is obtained.

The light transmission window is provided on the bottom wall of the pressure resistant container, and the reflecting mirror, the rotary disk and the impeller are housed in a cylindrical container connected to the lower part of the pressure resistant container. ing.

The photodetector compares the level of the pulsed signal with a predetermined reference voltage level, and a photoelectric conversion unit for converting the intermittent optical signal into an electrical pulsed signal. A comparator for outputting a signal when the level of the pulsed signal is higher than the reference voltage level,
The counter includes a counter that counts the signal from the comparison unit, a latch circuit that latches the count value of the counter at a predetermined cycle, and a display unit that displays the output of the latch circuit.

[0009]

According to the above hole flow velocity measuring device, the flow velocity of the fluid under high temperature and high pressure is converted into the rotation of the impeller, and this rotation is rotated by the light transmitting portion and the light shielding portion arranged alternately in the rotation direction. By transmitting to the board, by this rotating disk, the optical path from the one end of the first optical fiber to the one end of the second optical fiber is interrupted, and the intermittent change of light is detected by the photodetector on the ground. , It is possible to measure the velocity of high temperature fluid inside the borehole used for hot rock power generation.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing the overall configuration of the in-hole flow velocity measuring device of the present invention. Laser light source 11 placed on the ground
The laser light is made incident on the first optical fiber 12 from the above, and the laser light is supplied to the flow velocity detection unit 14 arranged in the boring hole 13. In the flow velocity detector 14, the laser light is intermittently modulated in proportion to the flow velocity, as will be described later, and the second optical fiber 1
5 is guided to the photodetector 16 on the ground. Photo detector 16
Determines the flow velocity from the intermittently modulated laser light, as will be described later.

FIG. 2 is a sectional view showing the structure of the flow velocity detecting section 14 arranged in the bore hole. The flow velocity detector 14 is housed in a cylindrical container 21. The upper part of the container 21 includes a closed pressure-resistant container 22. Pressure container 22
The ends of the first optical fiber 12 and the second optical fiber 15 are housed therein. These first and second optical fibers 12,
First and second lenses 25 and 26 are coupled to the one ends 23 and 24 of the lens 15, respectively. The first lens 25 is the first
The laser light emitted from the optical fiber 12 is expanded into parallel light, and the glass window 28 provided on the bottom wall 27 of the pressure-resistant container 22.
Through the pressure-resistant container 22.

A reflecting mirror 30 is arranged just below a glass window 28 in the container 21 which is continuously provided under the pressure-resistant container 22. The reflecting mirror 30 is adapted to turn back the parallel light 29 led out of the pressure resistant container 22 and introduce it again into the pressure resistant container 22 through the glass window 28. Pressure container 2
The parallel light 29 introduced into the inside of the second lens 2 is incident on the second lens 26 disposed inside the pressure resistant container 22. Second lens 26
Refocuses the parallel rays to generate a second optical fiber 15
The light from one end 24 thereof.

In the container 21 below the pressure resistant container 22,
A rotary shaft 32 extending rotatably and vertically is provided between a bottom wall 27 of the pressure-resistant container 22 and a bearing plate 31 provided at the lower end of the container 21. A disk 33 with a slit that is rotatable in the container 21 immediately below the pressure resistant container 22 is fixed to the rotary shaft 32. Disc with slit 33
Is partially present in the space between the bottom wall 27 of the pressure resistant container 22 and the reflecting mirror 30, and the first lens 25 to the second lens 2
It is arranged so as to rotate across the optical path of the collimated light ray 29 leading to 6. Although not shown, slits are formed in the portion of the disc 33 with slits that rotates across the parallel rays at regular intervals in the circumferential direction.

A propeller 34 rotatably arranged by groundwater is fixed to the lower part of the rotary shaft 32. As shown by the arrow 35, the groundwater flows in from the lower end of the container 21 and flows out of the container 21 through the through holes 36 formed in the peripheral wall of the container 21 below the pressure resistant container 22. The propeller 34 is rotated by the groundwater 35, and this rotation is transmitted to the slitted disk 33 via the rotary shaft 32. By rotating the disk 33 with slits, the first and second lenses 27,
The parallel light ray 29 passing between 28 is intermittently modulated. That is, when the disk 33 with slits crosses the optical path of the parallel light rays 29, the parallel light rays 29 pass through the slits (not shown) formed in the disk 33 with slits, and the parallel light rays are blocked between adjacent slits. Since the number of revolutions of the propeller 34 per unit time increases or decreases in proportion to the flow velocity of the groundwater 35, the number of revolutions of the disk 33 with slits also increases or decreases in proportion to the velocity of the groundwater 34. Therefore, the number of interruptions of the parallel rays interrupted by the disc 33 with slits per unit time increases or decreases in proportion to the flow velocity of the groundwater 34.

The slits (not shown) formed on the disc 33 with slits are provided from the first lens 25 to the reflecting mirror 3.
The second lens 2 from the parallel light ray 29 and the reflecting mirror 30 which go to 0
Although there are two optical paths of the parallel light rays 29 directed to 6, the structure may be such that these two optical paths are interrupted at the same time, or only one of them is interrupted and the other is simply passed. Furthermore, the interruption of the parallel rays 29 is not limited to the slit,
It may be composed of a portion that transmits light and a portion that blocks light.

In this embodiment, the disk with slit 3
3 is provided outside the pressure resistant container 22, and the pressure resistant container 2
Since the parallel rays 29 in 2 are guided to the external disk 33 with slits through the glass window 28, there is an advantage that the structure is simplified and there is no possibility that high pressure groundwater 35 will enter the pressure vessel 22.

FIG. 3 is a block diagram showing the configuration of the photodetector 16 provided on the ground shown in FIG. The intermittently modulated laser light obtained from the second optical fiber 15 enters a photoelectric conversion element 51 such as an avalanche phototransistor and is converted into an electric signal. This signal is an electric signal corresponding to the intermittently modulated laser light, amplified by the amplifier 52, and supplied to the comparison circuit 53. A reference voltage is supplied from the reference voltage source 54 to the comparison circuit 53, and this reference voltage is compared with the output of the amplifier 52. The comparison circuit 53
A shaped pulse signal is obtained by outputting a high level signal when the output of the amplifier 52 is larger than the reference voltage and outputting a low level signal when the output of the amplifier 52 is smaller than the reference voltage.

This pulsed signal is supplied to the counter circuit 55 and counted. The output of the counter circuit 55 is a binary signal indicating the count value and is supplied to the latch circuit 56.
The timer circuit 5 is provided in the counter circuit 55 and the latch circuit 56.
7, a clock pulse of a constant cycle is supplied, and the count value of the pulsed signal by the counter circuit 55 within the time of each cycle is latched by the latch circuit 56. Latch circuit 5
The count value of the pulsed signal latched by 6 is supplied to the D / A converter 58, converted into an analog signal, and displayed on the display 59 such as a meter. As a result, the display is updated on the display unit 59 at regular intervals determined by the timer circuit 57, so that the count value proportional to the groundwater flow velocity is sequentially displayed.

It is needless to say that the configuration of the photodetector shown in FIG. 3 is an example and can be changed by using other well-known techniques.

[0020]

According to the present invention, a propeller placed in the groundwater downstream converts a water flow velocity into a rotation velocity, which is then taken out as an intermittent modulation signal of light by an optical fiber, whereby a deep bore hole is formed. As described above, it became possible to measure the water flow velocity with high accuracy even in a high temperature fluid under high pressure.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of an in-hole flow velocity measuring device of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a flow velocity detector shown in FIG.

FIG. 3 is a block diagram showing a configuration of the photodetector shown in FIG.

[Explanation of symbols]

 21 Container 22 Pressure Resistant Container 23 One End of First Optical Fiber 24 One End of Second Optical Fiber 27 Bottom Wall 29 Parallel Rays 31 Bearing Plate 32 Rotating Shaft 35 Groundwater 36 Water Through Hole

Claims (3)

[Claims] 1. A first optical fiber that guides light from a light source into a pressure-resistant container disposed in a borehole, and light emitted from one end of the first optical fiber is expanded into parallel rays. A first lens disposed inside the pressure resistant container, and a light transmission window provided on a wall portion of the pressure resistant container so as to guide parallel light emitted from the first lens to the outside of the pressure resistant container. And a reflecting mirror arranged outside the pressure resistant container so that the parallel light guided to the outside of the pressure resistant container through the light transparent window is guided again into the pressure resistant container through the light transparent window. , A second lens arranged in the pressure-resistant container so as to receive and converge the parallel light guided into the pressure-resistant container by the reflecting mirror, and receive the light converged by the second lens And a second optical fiber that guides the received light to the photodetector A turntable that is rotatably disposed outside the pressure vessel across the optical path from the first lens to the second lens and in which light-transmitting portions and light-shielding portions are alternately arranged in the rotation direction; An impeller fixed to the rotating shaft of the rotating disk and rotatably arranged by groundwater flowing outside the pressure vessel, wherein the photodetector is provided with an intermittent optical signal from the second optical fiber. An in-hole flow velocity measuring device for measuring the flow velocity of the groundwater. 2. The hole velocity measuring device according to claim 1, wherein the light transmission window is provided in a bottom wall portion of the pressure resistant container,
The in-hole flow velocity measuring device, wherein the reflecting mirror, the rotary disk, and the impeller are housed in a cylindrical container that is continuously provided below the pressure-resistant container. 3. The hole velocity measuring device according to claim 1, wherein the photodetector converts the intermittent optical signal into an electric pulse signal, and the pulse signal. Of the pulsed signal is compared with a predetermined reference voltage level to output a signal when the level of the pulsed signal is higher than the reference voltage level, and a counter that counts the signal from the comparison unit, An in-hole flow velocity measuring device comprising: a latch circuit that latches the count value of the counter at a predetermined cycle; and a display unit that displays the output of the latch circuit.