Borehole measurement system

Abstract

This invention provides a borehole measurement system that measures boreholes using a borehole measurement cable that protects optical fibers and other components, securely fixes the borehole measuring instrument to the borehole, allows for easy release, and has a structure that prevents entanglement with optical fibers and other components. [Solution] The borehole measurement cable comprises an inner tube in which an optical fiber for transmitting and receiving signals between the observation equipment and the borehole measuring instrument is arranged inside the tube, and an outer tube in which the inner tube is arranged inside the tube. The outer tube consists of one or more layers and is composed of a metal tube optical fiber in which liquid is filled into the gaps between one tube and some or all of the layers of the outer tube. A pump is connected to the end of the cable, and a connection part for a measuring instrument to introduce liquid is provided at the end on the measuring instrument side. A piston mechanism equipped with a measuring instrument that is operated by the liquid is connected to the end on the measuring instrument side, and the liquid is pressurized and depressurized by the pump, and the measuring instrument is fixed to and released from the borehole via the piston mechanism.

Description

Technical Field

[0001] The present invention relates to a borehole measurement system for measuring a borehole using a borehole measurement cable that integrally incorporates signal lines, power lines, optical fibers, etc. between a borehole measuring instrument in a borehole (shaft) used for seismic measurement, geological survey, etc. and an observation instrument at an observation site. In particular, the present invention relates to a borehole measurement system that can firmly fix a borehole measuring instrument in a borehole without providing a separate pressure transmission pipe from the cable and perform accurate and stable observations.

Background Art

[0002] A borehole measurement system is widespread in which a measuring instrument such as an accelerometer is placed and fixed in a borehole (shaft) opened deep underground, and seismic measurement, geological survey, etc. are performed using an observation instrument at a ground observation site (including an observation section, etc.). FIG. 1 schematically shows this state. A borehole 1 is opened deep underground, and the depth H1 is generally about 50 m to 5000 m. A borehole measuring instrument 20 connected to a ground observation site 10 by a cable CB is placed and fixed (height H2 from the bottom) in this borehole 1, and information and signals detected by sensors in the borehole measuring instrument 20 are transmitted to the observation site 10 by the cable CB as electrical signals or optical signals and measured by an observation instrument installed in the observation site 10.

[0003] Due to such an arrangement relationship, in the vicinity of the observation site 1, the cable CB is horizontally wired, and in the borehole 1, it is necessary to insert and hang down the cable CB. Problems include the structure and resistance strength of the cable CB, the accuracy of signal and information transmission, and the resistance strength and stability of the fixed position (height H2) of the borehole measuring instrument 20.

[0004] Figure 2 shows the detailed configuration. Figure 2(A) shows the open state of the borehole measuring instrument 20 (a state in which it can move freely up and down), and Figure 2(B) shows the fixed state of the borehole measuring instrument 20 (the state during observation). Observation station 10 is equipped with observation equipment 11, including a computer and control unit, as well as a pump 12 for pressurizing and suctioning (depressurizing) the liquid. The borehole measuring instrument 20, which is inserted into and fixed in the borehole 1, is integrally composed of a measuring unit 21 made up of sensors and a piston mechanism 22 of a hydraulic mechanism that fixes and releases using liquid. The measuring unit 21 is connected to the observation equipment 11 by a transmission line 2, and the piston mechanism 22 is connected to the pump 12 by a pressure supply pipe 3. The transmission line 2 consists of a power line that supplies power to the measuring unit 21, an electrical signal line that transmits and receives signals and information between the measuring unit 21 and the measuring unit 21 using electrical signals, and an optical fiber that transmits and receives signals using light. The piston mechanism 22 consists of a cylinder 22-1 connected to the pressure supply pipe 3, a piston 22-2 that slides and reciprocates inside the cylinder 22-1, and a spring 22-3 that provides elastic force (tensile force) to the piston 22-2. The cylinder 22-1 is filled with water (or silicone oil) via the pressure supply pipe 3.

[0005] In the normal state, the piston mechanism 22 of the borehole measuring instrument 20 is held in a state where the left end face of the piston 22-2 does not protrude from the side of the piston mechanism 22, as shown in Figure 2(A), due to the elastic action (tensile force) of the spring 22-3. In this state, the borehole measuring instrument 20 is lowered or raised into the borehole 1 via the transmission line 2 and the pressure supply pipe 3. When the borehole measuring instrument 20 reaches a predetermined position, it is stopped, and the pump 12 is activated via the observation equipment 11 to pressurize the pressure supply pipe 3. As a result, the cylinder 22-1 is pressurized, and the piston 22-2 slides to the left as shown in the figure, overcoming the tensile force of the spring 22-3, causing the left end face of the piston 22-2 to protrude from the side and contact the wall of the borehole 1, fixing it in place as shown in Figure 2(B).

[0006] Thus, with conventional cables, in addition to the transmission line 2, a separate pressure-transmitting pipe 3 is required, resulting in a complicated installation structure and the problem of the transmission line 2 and pressure-transmitting pipe 3 becoming entangled when power is applied.

[0007] Furthermore, as mentioned above, the depth H1 of borehole 1 can be as deep as 5000m, so for geological surveys and other measurements, measurement data may be required at multiple locations along the way. Figure 3(A) shows a case where borehole 1 is measured at three locations, with borehole measuring instruments 20A to 20C fixed at appropriate depths for measurement. When measurements are taken at many locations at different depths in this way, the number of cables increases, which further increases the problem of the transmission lines 2 and pressure transmission pipes 3 becoming entangled.

[0008] Furthermore, if the pressure supply pipe 3 is not used, the measuring instrument 20 is installed at the bottom of the borehole 1, as shown in Figure 3(B), and then the gap between the measuring instrument 20 and the borehole 1 is filled with sand (silica sand) 4 to fix the measuring instrument 20 in place for measurement. However, this measurement method has the problem of requiring effort to put the sand (silica sand) 4 at the bottom of the borehole 1, as well as limiting the measurement location. In addition, if the measuring instrument 20 malfunctions, if it is fixed with sand (silica sand), the sand (silica sand) must be removed before it can be lifted, which is an even more time-consuming problem.

[0009] Note that in Figures 2 and 3, the observatory 10 is shown above the borehole 1 for convenience, but in reality, it is located in a remote location on the ground, as shown in Figure 1. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2017-130376 [Patent Document 2] Japanese Patent Publication No. 2015-219220 [Patent Document 3] Japanese Patent Publication No. 2011-89790 [Overview of the project] [Problems that the invention aims to solve]

[0011] In addition to the problems mentioned above, conventional technology has the following further challenges. Specifically, the inside of borehole 1 is a high-temperature environment, and is generally filled with water or dissolved gases, creating a corrosive gas atmosphere, which causes the optical fiber to degrade. Conventional optical fiber cables are made by coating optical fiber strands with resin. However, such optical fibers degrade rapidly after being inserted into borehole 1, increasing the transmission loss of the optical fiber cable and potentially making optical communication impossible.

[0012] Furthermore, the optical fiber cable and electrical signal transmission lines connected to the borehole measuring instrument, and the pressure supply pipe 3 for remotely operating the borehole measuring instrument 20 hydraulically, are installed parallel to the ground from the ground to the borehole 1 at the tip. However, if the borehole measuring instrument 20 at the lower end rotates during the suspension descent operation inside the borehole 1, the transmission lines 2 and the pressure supply pipe 3 may become entangled, causing them to break or be damaged.

[0013] The present invention has been made in light of the circumstances described above, and the object of the present invention is to provide a borehole measurement system that effectively and economically measures boreholes using a borehole measurement cable that protects optical fibers and the like, can be firmly fixed to a borehole without the need for a separate pressure supply tube, can be released, and has a structure that does not entangle with optical fibers and the like. [Means for solving the problem]

[0014] The present invention relates to a borehole measurement system that performs observations using a borehole measuring instrument installed in a borehole via a borehole measurement cable connected to observation equipment installed at an observatory. The object of the present invention is that the borehole measurement cable comprises an inner tube in which optical fibers for the exchange of signals or information between the observation equipment and the borehole measuring instrument are arranged, and an outer tube in which the inner tube is arranged, wherein the outer tube consists of one or more layers, and a metal tube optical fiber cable in which liquid is filled in the gaps between one tube and some or all of the layers of the outer tube, and a power line covered with a metal conductor that supplies power from the observation equipment to the borehole measuring instrument. The cable is twisted together to form a single unit, a pump is connected to the observation equipment side end of the borehole measurement cable, a connection part for introducing the liquid to the borehole measuring instrument is provided at the borehole measuring instrument side end of the borehole measurement cable, a piston mechanism equipped with the borehole measuring instrument which is operated by the liquid is connected to the borehole measuring instrument side end of the borehole measurement cable via the connection part, and the pump applies pressure or depressurization to the liquid, thereby fixing the borehole measuring instrument in the borehole or releasing it from the borehole via the piston mechanism.

[0015] Furthermore, the present invention relates to a borehole measurement system in which observations are performed by a borehole measuring instrument installed inside a borehole via a borehole measurement cable connected to observation equipment installed at an observatory. The objective of the present invention is that the borehole measurement cable is constructed as an integral part by twisting together a metal tube optical fiber cable containing an optical fiber for transmitting and receiving signals or information between the observation equipment and the borehole measuring instrument, a power line cable covered with a metal conductor for supplying power from the observation equipment to the borehole measuring instrument, and a liquid-filled metal tube in which liquid is filled into the void portion of a metal tube having an air gap. This is achieved by connecting a pump to the observation equipment side end of the borehole measurement cable, providing a connection part for introducing the liquid to the borehole measuring instrument at the borehole measuring instrument side end of the borehole measurement cable, and connecting a piston mechanism equipped with the borehole measuring instrument, which is operated by the liquid, to the borehole measuring instrument side end of the borehole measurement cable via the connection part, thereby applying pressure or depressurization to the liquid by the pump, and fixing the borehole measuring instrument in the borehole or releasing it from the borehole via the piston mechanism. [Effects of the Invention]

[0016] The borehole measuring cable of the present invention allows the borehole measuring instrument to be firmly fixed and released at an appropriate position in the borehole without the need to separately provide a pressure supply pipe, simplifying the configuration and installation work. Furthermore, since the optical fiber is housed in a metal tube, it has the advantage of protecting the optical fiber from water and corrosive gas atmospheres. In addition, since the metal tube optical fiber cable and power line cable are integrated, damage to the cable and optical fiber caused by twisting and entanglement during borehole descent or ascent can be prevented.

[0017] By covering the outside of the cable for borehole measurement with an outer covering having a larger diameter, it is possible to prevent the aging deterioration of the metal pipe due to corrosive gas and the penetration of gas that causes fiber deterioration into the inside of the metal pipe, and it is expected to delay the aging deterioration of the optical fiber. In addition, when making a waterproof connection between the cable and the borehole measuring instrument, it is necessary to provide a connection interface with the pressure transmission pipe. According to the present invention, since the double or triple metal pipe optical fiber cable or the metal pipe optical fiber cable and the liquid-filled metal pipe are integrated, it contributes to the miniaturization of the borehole measuring instrument and has the advantage that the connection process can be simplified.

Brief Description of the Drawings

[0018] [Figure 1] It is a schematic diagram showing an example of measurement by a borehole. [Figure 2] It is a schematic cross-sectional view showing the state of fixing and releasing of a conventional borehole measuring instrument. [Figure 3] It is a schematic cross-sectional view showing another example of a conventional borehole measuring instrument. [Figure 4] It is a schematic cross-sectional view showing an example (First Embodiment) of the borehole measurement system of the present invention. [Figure 5] It is a cross-sectional view showing an example of the cable for borehole measurement according to the present invention. [Figure 6] It is a cross-sectional view showing another example of the cable for borehole measurement according to the present invention. <00​​​​​​​​​​​​​​​​​​ [Modes for carrying out the invention]

[0019] The borehole measurement cable used in this invention is a cable that connects a borehole measuring instrument installed inside a borehole to observation equipment at a ground observation station. It integrates a metal tube optical fiber cable for transmitting signals and information between the observation equipment and the borehole measuring instrument, and a power line cable for supplying power from the observation equipment to the borehole measuring instrument by twisting them together. In the case of measurement using only optical fibers, the sensors do not require power, so the power line cable is not necessary.

[0020] The central metal tube is surrounded by a concentric double metal tube with a gap between them, or by a concentric triple metal tube with an additional gap surrounding the double metal tube. In the case of a double tube, the gap between the metal tube and the double tube is filled with a liquid such as water or silicone oil. In the case of a triple tube, the gap between the metal tube and the double tube is filled with liquid, as is the gap between the double tube and the triple tube.

[0021] In the case of a triple-walled pipe, the structure may be such that liquid is filled in both the gap between the metal pipe and the double-walled pipe and the gap between the double-walled pipe and the triple-walled pipe, or the structure may be such that liquid is filled in either the gap between the metal pipe and the double-walled pipe or the gap between the double-walled pipe and the triple-walled pipe. According to the borehole measurement cable of the present invention, the piston mechanism at the tip can be driven by pressurizing or suctioning (depressurizing) a liquid with a pump at the observation station, thereby fixing and releasing the borehole measuring instrument, eliminating the need to lay a separate pressure supply pipe. The elastic action of the spring within the piston mechanism can also be used to fix and release the borehole measuring instrument.

[0022] Furthermore, the borehole measurement system of the present invention is a borehole measurement system using a borehole measurement cable. In the case of a double pipe, it is equipped with a reversible pump that performs pressurization and suction (depressurization), and the borehole measuring instrument is fixed or released by a piston mechanism attached to the tip of the borehole measurement cable. In the case of a triple pipe, it is equipped with two pressurization pumps, or one pump and a switching valve, and the borehole measuring instrument is firmly fixed or released by the piston mechanism attached to the tip of the borehole measurement cable by pressurizing (depressurizing) the double pipe or the triple pipe, or by pressurizing one or two built-in liquid-filled metal tubes with a pump.

[0023] By pressurizing or depressurizing the liquid with a pump, the borehole measuring instrument can be fixed in place and released at a predetermined location. This eliminates the need for a separate pressure supply pipe, prevents cable entanglement, and allows for accurate and stable seismic observation and geological surveys with a simple and durable configuration.

[0024] Embodiments of the present invention will be described below with reference to the drawings.

[0025] Figure 4 shows an overview of a borehole measurement system (first embodiment) using the borehole measurement cable 100 according to the present invention. An observation station 110 is installed near the borehole 100, and the observation station 110 is equipped with an observation instrument 111 with a control unit, as well as a reversible pump 112 capable of pressurizing and suction (depressurizing). The reversible pump 112 is controlled by the observation instrument 111, and the borehole measurement cable 300, which will be described later, is connected to the observation instrument 111 and the reversible pump 112, and a borehole measuring instrument 120 is connected to the tip of the borehole measurement cable 300.

[0026] The borehole measuring instrument 120 is inserted into the borehole 100, lowered, and fixed in a predetermined position. The borehole measuring instrument 120 consists of a measuring unit 121 equipped with sensors and a power supply, and a piston mechanism 122 that fixes or releases the borehole measuring instrument 120 by the sliding of a piston 125. The cylinder 124 of the piston mechanism 122 is connected to the borehole measuring cable 300 via a connecting pipe 123. The cylinder 124 is also provided with a piston 125, and a spring 126 having elastic force (tensile force) is engaged with one end of the piston 125.

[0027] The cross-sectional structure of the X1-X2 wires of the borehole measurement cable 300 is shown in Figure 5 or Figure 6, for example. In Figure 5, a double and triple conduit are shown, and in Figure 6, a liquid-filled metal conduit is also shown. In the center of the borehole measurement cable 300 in Figure 5, metal conduits 301, 302, and 303 of different diameters are arranged concentrically, and the power line cable 304 on the outside is twisted together to form a composite cable 300. An optical fiber is housed in the metal conduit 301. In this example, the outside of the twisted wires is double-covered with a cable outer sheath 312 and outer iron wires 320 and 321. The gap 310 between metal pipe 301 and metal pipe 302, and the gap 311 between metal pipe 302 and metal pipe 303 are filled with silicone oil, which prevents rust. A reversible pump 112 is connected to the upper end of each gap 310 and 311, and the lower end is connected to a piston mechanism 120. Although Figure 5 shows a triple pipe, the double pipe used in this example can be obtained by removing either metal pipe 302 or metal pipe 303.

[0028] The larger the gaps 310 and 311, the easier it is for the silicone oil to pass through. However, the size of these gaps is determined by a balance between the amount of silicone oil to be injected, the overall cable diameter, the ease of handling due to the cable's weight, and the allowable bending diameter. In this example, the material of the metal tubes 301, 302, and 303 is steel (e.g., SUS316L), with metal tube 301 having an outer diameter of 1.8 mm and a thickness of 0.2 mm, and metal tube 302 having an outer diameter of 3.0 mm and a thickness of 0.2 mm.

[0029] Note that the silicone oil may be replaced with water, and in Figure 4, the sensors and other components of the measurement unit 121 are omitted from the display. Also, the piston mechanism 122 is shown schematically, and any mechanism that operates in response to the pressurization and depressurization of the liquid will suffice.

[0030] Furthermore, Figure 6 shows the borehole measurement cable 350 used in the present invention, which is a composite cable formed by twisting together a metal tube optical fiber cable 354, a power line cable 351, and liquid-filled metal tubes 353-1 and 353-2 filled with silicone oil. The outside is double-coated with a cable outer sheath 355 and an outer iron wire 356. In this example, a single-layer metal tube optical fiber cable 354 is used, so the liquid-filled metal tubes 353-1 and 353-2 embedded in the cable are used.

[0031] In this configuration, an example of its operation will be explained with reference to the flowchart in Figure 7. Since this example is a double-tube design, in the case of Figure 5, for example, the metal tube 302 is removed, and in the case of Figure 6, only the liquid-filled metal tube 353-1 is provided.

[0032] First, the upper end of the borehole measurement cable 300 (or 350) is connected to the observation equipment 111 and the reversible pump 112, and the lower end is connected to the borehole measuring instrument 120 (step S1), and the borehole measuring instrument 120 is lowered into the borehole 100 (step S2). In the lowered state when the cable 300 (or 350) is laid, the pump 112 is not driven, and as shown in Figure 8(A), the left end face of the piston 125 is flush with the side surface due to the tensile force of the spring 126, so the borehole measuring instrument 120 is in an open state and can descend (ascend) freely inside the borehole 100.

[0033] The lowering position of the borehole measuring instrument 120 is constantly measured by the observation instrument 111. The borehole measuring instrument 120 is lowered to a predetermined depth (step S3), and when it reaches that depth, the lowering stops. At the same time, the observation instrument 111 activates the reversible pump 112 (step S4), pressurizing the silicone oil or liquid-filled metal tube 353-1 that is filled in the void 310 (step S5). This pressurizes the cylinder 124, and the pressurized force causes the piston 125 to slide to the left in Figure 4. The left end face of the piston 125 comes into contact with the wall of the borehole 100 as shown in Figure 8(B), and the borehole measuring instrument 120 is fixed inside the borehole 100 (step S6).

[0034] Since the sensors attached to the measurement unit 121 are powered by power line cables, measurements by the sensors begin as soon as the borehole measuring instrument 120 is fixed in place, and unpowered measurements are also performed using optical fibers (step S7). The measured information and data are transmitted to the observation equipment 111 via power lines and optical fibers, where analysis and other processing are performed. Such measurements are performed periodically and continuously over a predetermined period.

[0035] Subsequently, if it becomes necessary to release the fixed borehole measuring instrument 120 at the end of the scheduled measurement period (step S10), for example, when the measurement period has ended, the observation instrument 111 switches the reversible pump 112 to suction operation or pressure release (step S11). As a result, the cylinder 124 is depressurized, and the piston 125 slides to the right in Figure 4 due to the pulling force of the spring 126, and as shown in Figure 8(A), the left end face of the piston 125 is released from the wall surface of the borehole 100, making the borehole measuring instrument 120 movable (step S12), and the borehole measuring instrument 120 is further lowered or raised (step S13), and the process returns to step S3.

[0036] Although the above description refers to it as a reversible pump 112, if the borehole measuring instrument 120 is to be released by releasing the liquid pressure, a regular pressure pump will suffice. In other words, the pump should be operated when the borehole is fixed and stopped when it is released.

[0037] Furthermore, while the above describes an example where metal tube optical fiber cables and power line cables are bundled together, if the borehole measuring instrument 120 is an optical fiber sensor, only optical fiber is needed, and power line cables become unnecessary.

[0038] Next, a borehole measurement system (second embodiment) in which the borehole measurement cable is a triple-tube will be explained with reference to Figure 9. Since this example is an example of operation of a triple-tube, in the case of Figure 5, the structure is provided with metal tubes 301 and 302, and in the case of Figure 6, the structure is provided with both liquid-filled metal tubes 353-1 and 353-2. The cross-sectional structure of Y1-Y2 in Figure 9 is the same as that described in Figure 5 or Figure 6.

[0039] As shown in Figure 9, an observation station 210 is installed near the borehole 200. The observation station 210 is equipped with an observation instrument 211 with a control unit, as well as two pumps 212 and 213. Pumps 212 and 213 are controlled by the observation instrument 211. The observation instrument 211 and pumps 212 and 213 are connected to a triple-tube borehole measurement cable 300 (or 350) according to the present invention, and a borehole measuring instrument 220 is connected to the tip of the borehole measurement cable 300 (or 350). The borehole measuring instrument 220 is inserted into and fixed inside the borehole 200. The borehole measuring instrument 220 consists of a measuring section 221 and a piston mechanism 222. One cylinder 225 of the piston mechanism 222 is connected via a connecting pipe 223 to the gaps 310 and 311 of the borehole measuring cable 300 (or 350) or to the liquid-filled metal tubes 353-1 and 353-2.

[0040] In this configuration, an example of its operation will be explained with reference to the flowchart in Figure 10.

[0041] First, the upper end of the borehole measurement cable 300 (or 350) is connected to the observation equipment 211 and pumps 212 and 213, and the lower end is connected to the borehole measuring instrument 220 (step S20), and the borehole measuring instrument 220 is lowered into the borehole 200 (step S21). In this lowered state during cable laying, the pump 213 is activated and the cylinder 226 is pressurized via the connecting pipe 224, so the left end face of the piston 227 is flush with the side surface as shown in Figure 11(A), and the borehole measuring instrument 220 can freely descend (ascend) inside the borehole 200.

[0042] The lowering position of the borehole measuring instrument 220 is constantly measured by the observation instrument 211. The borehole measuring instrument 220 is lowered to a predetermined depth (step S22), and when it reaches the predetermined depth, the lowering stops, and the pump 213 is stopped and the pump 212 is started (step S23). As a result, the void 310 or 311 of the borehole measuring cable 300 (or 350), or the silicone oil filled in the liquid-filled metal tube 353-1 or 353-2 is pressurized, and the cylinder 225 is pressurized via the connecting pipe 223 (step S24). The piston 227 slides to the left in Figure 9, and the left end face of the piston 227 comes into contact with the wall of the borehole 200 as shown in Figure 11(B), fixing the borehole measuring instrument 220 in place (step S25).

[0043] In this fixed state, power is supplied to the measurement unit 221 via force lines, so measurements are performed by the attached sensors, as well as powerless measurements by the optical fiber sensor (step S26). The above measurements are performed continuously for a predetermined period or periodically. In the case of powerless measurements by the optical fiber sensor, for example, acceleration measurement for earthquake detection, power lines and signal lines are not required.

[0044] Subsequently, if it becomes necessary to release the fixed borehole measuring instrument 220, for example, when the measurement period has ended (step S30), the observation instrument 211 stops pump 212 and starts pump 213 to pressurize the silicone oil in the gap 311 or 310 of the triple tube or the liquid-filled metal tube 353-2 or 353-1 (step S31), pressurizes cylinder 226 to slide piston 227 to the right, and as shown in Figure 11(A), the left end face of piston 227 is released from the wall of the borehole 200, the borehole measuring instrument 220 becomes movable (step S32), the borehole measuring instrument 220 is further lowered or raised (step S33), and the process returns to step S22.

[0045] In this example, two pumps 212 and 213 are provided, and the silicone oil in the borehole measurement cable 300 (or 350) is pressurized by switching between pumps 212 and 213. However, the communication relationship between pumps 212 and 213 and the triple pipe and the liquid-filled metal pipe may be reversed. Alternatively, as shown in Figure 12, one pump 214 and a switching valve 215 may be provided, and the switching valve 215 may be switched by the observation equipment 111.

[0046] In the example above, metal tube optical fiber cables and power line cables are bundled together, but when measuring with an optical fiber sensor that does not require power, power line cables are not necessary.

[0047] As optical fiber sensors, for example, those disclosed in Japanese Patent Nos. 5118004, 5702623, 6002329, and 6763567 can be used. Optical fibers have strong lightning resistance, which is a major advantage for systems that do not use electricity in the observation system. In reality, equipment failures due to lightning strikes are frequent in outdoor earthquake measurements using electrical signals. [Explanation of symbols]

[0048] 1 borehole 2 transmission lines 3 Pressure supply pipe 4. Sand (silica sand) 10 Observatory 11. Observation equipment 12 pumps 20 Borehole measuring instrument 21 Measurement Unit 22 Piston mechanism 100, 200 boreholes 110, 210 Observatory 111, 211 Observation equipment 112 Reversible pump 120, 220 Borehole Measuring Instrument 121, 221 Measurement section 122, 222 Piston mechanism 212,213 pumps 300, 350 Borehole Measurement Cable

Claims

1. In a borehole measurement system, observations are performed by a borehole measuring instrument installed inside a borehole via a borehole measurement cable connected to observation equipment installed at an observatory, The aforementioned borehole measurement cable, The cable comprises an inner tube in which an optical fiber for transmitting and receiving signals or information between the observation instrument and the borehole measuring instrument is arranged, and an outer tube in which the inner tube is arranged, wherein the outer tube consists of one or more layers, and is configured as a metal tube optical fiber cable in which liquid is filled into the gaps between one tube and some or all of the layers of the outer tube. A pump is connected to the observation equipment side end of the borehole measurement cable, and the borehole measurement instrument side end of the borehole measurement cable is provided with a connection part to the borehole measurement instrument for introducing the liquid. A piston mechanism equipped with the borehole measuring instrument, which is operated by the liquid, is connected to the borehole measuring instrument side end of the borehole measuring cable via the connection part. A borehole measuring system characterized in that the pump applies pressure or depressurization to the liquid, and the piston mechanism is used to fix the borehole measuring instrument to the borehole or release it from the borehole.

2. The borehole measurement system according to claim 1, characterized in that the metal tube optical fiber cable is arranged in the central layer, and a power line cable covered with a metal conductor that supplies power from the observation equipment to the borehole measuring instrument is twisted and integrated around its outer circumference.

3. In a borehole measurement system, observations are performed by a borehole measuring instrument installed inside a borehole via a borehole measurement cable connected to observation equipment installed at an observatory, The aforementioned borehole measurement cable, The device is constructed by twisting together a metal tube optical fiber cable containing an optical fiber for transmitting and receiving signals or information between the observation equipment and the borehole measuring instrument, and a liquid-filled metal tube in which liquid is filled into the voids of a metal tube having voids. A pump is connected to the observation equipment side end of the borehole measurement cable, and the borehole measurement instrument side end of the borehole measurement cable is provided with a connection part to the borehole measurement instrument for introducing the liquid. A piston mechanism equipped with the borehole measuring instrument, which is operated by the liquid, is connected to the borehole measuring instrument side end of the borehole measuring cable via the connection part. A borehole measuring system characterized in that the pump applies pressure or depressurization to the liquid, and the piston mechanism is used to fix the borehole measuring instrument to the borehole or release it from the borehole.

4. The borehole measurement system according to any one of claims 1 to 3, wherein the liquid is water or silicone oil.

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