JP4006884B2 - Groundwater status logging method and device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a logging method and apparatus for exploring the flow path of groundwater in a formation, and an object thereof is to enable significant shortening of logging time and highly accurate logging.
[0002]
[Prior art]
The groundwater in the formation does not always flow uniformly in the ground, but often flows in a specific zone. Such zones are generally referred to as “water roads”, and the groundwater problem is complicated by the fact that pollutants arrive earlier than expected, especially in fractured rocks and gravel grounds. Grasping the groundwater flow paths, such as understanding the flow of concrete components due to construction work and predicting landslides, that is, logging work to investigate and clarify the existence of water paths is an important issue. Yes.
[0003]
Well-known logging means include, for example, a salt logging method in which a boring hole is filled with salt water, and the water resistivity is identified by the location where the electrical resistivity value at each site in the hole has decreased, or boring There is known a warm water logging method or the like that fills a hole with warm water and identifies a water channel at a point where the water temperature drops at each part in the hole.
[0004]
[Problems to be solved by the invention]
However, in general, even if a drilling hole or observation hole is drilled and investigated, there is a fluidized layer of water at any depth in the depth direction as well as a specific location in the drilled borehole or observation hole. It is extremely difficult to specify exactly. That is, for example, in order to log a bedrock layer having multiple cracks per meter along the long excavation hole of about 500 to 1000m underground, the presence of a flowing water layer (water path) in the entire formation (rock layer) The conventional means for detecting the water flow velocity / flow direction in the area partitioned by the two packers with the packers at both ends within the unit of 50 cm to 1 m in the hole is too inefficient. In addition, accurate measurement logging is impossible.
[0005]
[Means for Solving the Problems]
Accordingly, the present invention has solved the above-mentioned problems in the prior art and has developed an accurate and efficient logging method and apparatus over the depth direction in a borehole. When an internal water-flowing type sonde with a built-in flow sensor is inserted into the underground hole and the change in water flow along the depth direction of the hole is measured, the outer wall of the intermediate part of the water flow of the sonde A ground water condition logging method characterized in that a slidable elastic packer is attached between the two and a constant amount of groundwater is pumped from the hole or a constant amount of water is supplied into the hole. .
[0006]
The present invention also relates to a groundwater condition logging method in which a borehole television (BTV) camera is attached to the tip of the above-mentioned sonde, and the wall surface condition in the hole can be observed with a monitor installed on the ground. Related. Furthermore, the present invention provides an internal water flow type sonde with a built-in water flow sensor, a logging cable connected to the sonde, a data processing device for performing data processing via the logging cable, and a constant amount from the inside of the hole. Of groundwater or water supply means for constantly supplying a fixed amount of water into the hole. It also relates to a groundwater logging system characterized by a movable elastic packer. The present invention further relates to a groundwater status logging device in which a television camera is attached to the tip of the above-described sonde and the wall surface condition in the hole can be observed with a monitor installed on the ground.
[0007]
In the above configuration, a sonde is inserted into the excavated hole, and the elastic packer on the outer peripheral surface is brought into contact with the entire peripheral surface of the hole wall. Next, the groundwater accumulated in the hole is continuously pumped up to the ground by a certain amount per unit time. New groundwater flows into the sonde by pumping the borehole water, and the flow rate in the sonde per unit time is continuously measured by the water flow sensor built in the sonde. After that, the elastic packer on the outer peripheral surface is slidably contacted with the hole wall surface, while the passage of groundwater on the outer periphery of the sonde is restricted, the sonde is lowered along the hole in the depth direction, and the flow rate in the groundwater is increased. By continuously measuring, the presence of water path due to the flow rate change is logged.
[0008]
In this case, if the measurement position in the hole is shallow and there is no or little groundwater, conversely, a fixed amount of water per unit time is supplied into the hole and passed through the sonde to enter the ground from the wall surface of the hole. By measuring the change in the flow rate of invading water, it is also possible to log the presence of a water channel. Further, in this case, when a borehole television (BTV) camera is attached to the tip of the sonde, the wall surface state of the groundwater flow rate changing portion in the above-mentioned sonde can be visually confirmed simultaneously by the ground monitor.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In the following, the specific contents of the present invention will be described based on the embodiment shown in FIGS. 1 and 2, wherein 1 is a sonde, 7 is a logging cable, 10 is a data processing device, and 17 is a pumping means. . As shown in detail in FIG. 2, the sonde 1 is formed in a vertically long cylindrical body having a diameter of about 50 mm and a length of about 3 m. A through hole 2 is provided at the lower side, and the upper side is provided. Are provided with through-holes 3, and a flow meter using an ultrasonic sensor 4 as a water flow rate sensor is provided near the through-hole 3 inside the cylindrical body.
[0010]
Specifically, this ultrasonic sensor uses a phenomenon in which a reflected wave reflected by a launch wave and a fine particle in water varies depending on the moving speed of the particle. The flow velocity in the vertical direction is obtained by utilizing the Doppler effect by ultrasonic waves, and this makes it possible to measure the flow velocity of spring water in the range of 1 mm / sec to 3000 mm / sec. can do. Further, an elastic packer 5 is attached to the outer peripheral surface of the sonde 1 between the above-described through holes 2 and 3 (water passing intermediate portion) over the entire circumference. The elastic packer 5 used here is formed of, for example, foamed rubber, urethane or other sponge-like material in an annular shape (doughnut shape), and this is adhered to the outer peripheral surface of the sonde 1 while It is configured so that it can expand and contract freely outwardly in accordance with the unevenness. A borehole television (BTV) camera 6 is attached to the tip (lower end) of the sonde 1.
[0011]
The logging cable 7 is fastened to the upper end of the above-described sonde 1, and has an information communication line built in the ultrasonic sensor 4 and the TV camera 6 inside, and is installed on the ground directly above the excavation hole H. The cable drum 9 is wound or unwound through the pulley 8a of the depth measuring instrument 8. Further, the data processing apparatus 10 includes a logging controller 11 such as a pumping pump controller and a water level indicator, a pumping amount indicator, a BTV monitor, a BTV video deck 16, a data logger 15 such as a personal computer, and the like.
[0012]
The pumping means 17 includes a pumping pump 17a and a pumping pipe 18 suspended to a certain depth in the excavation hole H, a pumping amount measuring flowmeter 18a, and the like. The pumping pump 17a used in this case is a small pump having a diameter of about 50 mm so that it can be inserted into the small-diameter excavation hole H. Reference numeral 20 denotes a water level gauge, which is connected to the water level indicator of the logging controller 11 via the cable 13, and connected to the logging controller 11 from the depth measuring instrument 8 via the cable 12. Similarly, the cable drum 9 is connected to the logging controller 11 via the cable 14, and the pumping pipe is connected to the water level indicator of the logging controller 11 via the cable 19.
[0013]
In the above configuration, the sonde 1 is inserted into the excavation hole H having a diameter in the range of 60 mm to 280 mm, and the elastic packer 5 on the outer peripheral surface is brought into contact with the entire peripheral surface of the hole wall. Next, the borehole water accumulated in the excavation hole H is continuously pumped up to the ground via the pumping pipe 18 by a fixed amount per unit time by the pumping pump 17a. When the groundwater is pumped up, new groundwater flows into the sonde 1 from the through-hole 2 and then flows out of the through-hole 3 into the excavation hole H again. Thus, the flow rate in the sonde 1 per unit time is continuously measured, and the measurement result is sequentially transmitted to the logging controller 11 via the logging cable 7 and the cable 14.
[0014]
Thereafter, the cable drum 9 is rotated to sequentially feed out the logging cable 7, thereby restricting the passage of groundwater on the outer peripheral side of the sonde 1 while sliding the elastic packer 5 on the outer peripheral surface against the hole wall surface of the excavation hole H. Sequentially measure the flow rate in the sonde of the groundwater while descending the sonde 1 along the hole H in the depth direction, and send this to the logging controller 11 to check the presence of the water channel due to the change in flow rate. Logging. In this case, the pulley 8a of the sounding instrument 8 measures the feeding length of the logging cable 7 described above, transmits it to the logging controller 11 via the cable 12, and sequentially determines the depth position of the sonde 1 from the ground. Can be confirmed.
[0015]
In this case, in the case where the measurement position in the excavation hole H is shallow and there is no or little water in the hole, conversely, a fixed amount of water per unit time is injected into the hole artificially to be perpendicular to the hole. The presence of a water channel can also be logged by generating a flow and measuring the change in the flow rate of water passing through the sonde 1 and entering the ground from the hole. Further, in this case, when a borehole television (BTV) camera 6 is attached to the tip of the sonde, the logging wall 7 and the cable 14 indicate the hole inner wall surface state at the location where the spring water flow rate changes in the sonde 1 described above. Are simultaneously transmitted to the data processing apparatus 10 such as a monitor on the ground, and the part is visually confirmed, and video recording is performed as necessary.
[0016]
In the embodiment described above, a compact ultrasonic sensor is used as the water amount sensor, but an electromagnetic flow meter may be used. The electromagnetic flow meter is more preferable than the ultrasonic sensor because it is less affected by the water temperature and water quality in the borehole.
[0017]
【Example】
〔Measurement condition〕
In logging with a flow meter, the location of a water channel is specified by continuously measuring the flow velocity of groundwater in the bore axis direction. The excavation hole used as an example is a 500 m long A hole excavated at 45 degrees, and a B hole with a diameter of 76 mm and a length of 60 m excavated vertically. In a separately conducted water permeability test, a water permeability coefficient of about 10 ⁻⁸ to 10 ⁻⁴ cm / s is obtained. The measurement was conducted in a natural state and in a pumped state.
[0018]
〔Measurement result〕
No clear flow rate change in the natural state was observed in both the A and B holes. On the other hand, in the pumped state, there were several changes in flow velocity in both holes. That is, as shown in FIG. 3, in the hole A, significant changes in the flow velocity were observed at the depths of 239 m, 263 m, 282 m, and 303 m, respectively, and in comparison with the separately conducted water permeability test results (water injection method). As shown in FIG. 4, it was confirmed that the hydraulic conductivity in the 5 m section was approximately 10 ⁻⁴ cm / sec or more and the correspondence with the flow velocity change portion was confirmed. Further, in the comparison in the 25 m section, it was recognized that the permeability coefficient and the flow velocity difference in the section (flow velocity at the upper end of the section−flow velocity at the lower end) coincided. In other words, the slope of the profile of the section seems to indicate the magnitude of the hydraulic conductivity.
[0019]
As for the change of the flow velocity in the B hole, as shown in FIG. 5, the change of the flow velocity is recognized at the locations of 32 m and 59 m. As is apparent from the recorded photographs by the BTV monitor in FIGS. 6 and 7, the presence of an opening crack having a width of 1 to 2 mm was confirmed at this location, and the water channel could be identified as a crack (see FIG. 7). Moreover, in the comparison with the water permeability test in a 5 m section, the correspondence with the flow velocity change location was confirmed in the location where the water permeability coefficient was 10 ⁻⁴ cm / sec or more.
[0020]
[Discussion 1] Detection of water path Many cracks were observed by the borehole television (BTV) camera mounted on the sonde, but only a small portion of the actual flow velocity changes were observed. For example, in the B hole, the presence of 191 cracks was confirmed in the section from 15 m to 61 m, but only 9 cracks having an opening width of 1 mm or more were found. However, it is actually possible to judge only water cracks in FIG. 6 showing the portion A in FIG. 5 and in FIG. 7 showing the portion B in FIG.
[0021]
This is clear from the fact that the highly permeable part of the separately conducted permeability test and the flow velocity change part by the flow meter logging by the sonde were consistent, and the crack that became the water channel could be accurately identified. It can be said that it shows. At the same time, it was found that the presence of a crack in the hole wall image inside the borehole and the opening phenomenon alone cannot be immediately determined as a water channel. This is because the main water channels are very limited for many cracks, so it is important to screen from the hydraulic side in order to accurately detect the water channels. It can be said that it also suggests.
[0022]
[Discussion 2] Estimating the hydraulic conductivity of the water path For locations where significant changes in flow velocity are observed in both the A and B holes described above, water permeability is determined from the amount of groundwater at that location, the amount of head change due to pumping, and the width of the crack. Coefficients can be calculated. In the case of two water crevices in the B hole, if the opening width is 1 mm and 1.5 mm respectively measured by BTV, the water permeability coefficient is 1.0 cm / sec and 2.6 cm / sec, respectively. In addition, there are no other open cracks in the 5m section corresponding to the permeability test, and the matrix is also considered to have a relatively small permeability coefficient, so it is considered that the permeability coefficient of these two sections is brought about by each crack. be able to.
[0023]
At this time, the hydraulic conductivity of the 5 m section is 2.0 × 10 ⁻⁴ cm / sec and 7.8 × 10 ⁻⁴ cm / sec, respectively. This value is close to the value obtained from the water permeability test, and it is considered that the water permeability coefficient of the water path was evaluated with a reasonable value. In addition, although no clear change in flow velocity is observed, if the flow velocity profile has a slope, the permeability of individual cracks is small, but the presence of a large number increases the permeability of the section. It is thought that there is. In such a case, it is not possible to obtain the permeability coefficient of each crack, but it is possible to estimate the permeability coefficient from the flow velocity difference before and after the section.
[0024]
For example, when the permeability coefficient of the same section as the permeability test of the 25 m and 5 m sections is obtained from the flow velocity profile of the A hole, 10 ⁻⁴ respectively. ^{-10 −6} cm / sec, 10 ⁻⁴ A hydraulic conductivity of the order of -10 ⁻⁵ cm 2 / sec was obtained. When this is compared with the results of the permeability test conducted in the same section, it can be seen that the difference in the permeability coefficient between the two is within one order if it is 10 ⁻⁵ cm / sec or more. On the other hand, for the section where the permeability coefficient of less than 10 ⁻⁵ cm / sec was obtained in the permeability test, the permeability coefficient could not be calculated because there was no flow velocity difference in the section, or a difference of one order or more occurred. became.
[0025]
This depends on the water head difference between the natural state and the pumped state, and the amount of pumped water, but the estimated limit of the permeability coefficient by the flow meter logging using the sonde of this embodiment is about 10 ⁻⁵ cm / sec. It is shown that. On the other hand, it is considered that the permeability coefficient in the section can be evaluated from the slope of the flow velocity profile for the section having a permeability coefficient higher than this.
[0026]
【The invention's effect】
As described in detail above, the present invention inserts an internal water flow type sonde with a built-in water flow sensor such as an electromagnetic flow meter and an ultrasonic flow meter into the underground hole, and measures changes in water flow over the depth direction of the hole. In some cases, an elastic packer that is slidable with the hole wall surface is attached to the outer peripheral surface of the water passage intermediate part of the sonde, and a fixed amount of groundwater is pumped from the inside of the hole, or a fixed amount of water is constantly put into the hole. Even if there is a slight change in the inner diameter of the drilling hole in the length direction due to the unevenness of the inner wall surface of the drilling hole due to the supply of water, the outer circumference of the outer surface of the drilling hole will be affected by the elasticity of the elastic packer. The edge part can always be in contact with the wall surface of the hole, which enables continuous logging in the depth direction in the drilling hole, and can be applied even when the logging depth is 500 m or more. Compared to the case by Not only it is possible to increase the measurement range, the presence of water conducting can be confirmed accurate and quickly, the logging of an efficient and low cost can be implemented.
[0027]
In addition, when conducting ground shallow logging, which is relatively close to the ground surface, especially during winter when the groundwater level drops, water is supplied to the cracked portion of the shallow layer by always supplying a fixed amount of water into the hole. Since the flow rate of the feed water can be easily measured in the sonde, the logging operation is further facilitated when the groundwater is decreasing or when logging is performed in a shallow formation. In addition, when a borehole television (BTV) camera is attached to the tip of the sonde, and the wall surface condition in the hole can be observed with a monitor installed on the ground, the logging location due to changes in the flow rate of groundwater in the hole Since it can be visually confirmed by the terrestrial BTV monitor, it is possible to detect the water channel more reliably.
[Brief description of the drawings]
FIG. 1 is a principle explanatory diagram showing an outline of a groundwater status logging system according to an embodiment of the present invention.
2 is an enlarged cross-sectional view of a main part showing a schematic structure of a sonde in FIG. 1;
FIG. 3 is a chart showing a flow velocity profile of an A hole.
FIG. 4 is a chart showing a flow velocity profile (depth: 190 m to 320 m) of the A hole and a water permeability test result.
FIG. 5 is a chart showing a flow velocity profile of a B hole and a 5 m section permeability test result.
FIG. 6 is a monitor drawing showing an enlarged crack portion at a portion A in FIG. 5;
FIG. 7 is a monitor drawing showing an enlarged crack portion at a portion B in FIG. 5;
[Explanation of symbols]
1 Sonde 2 Through-hole 3 Through-hole 4 Ultrasonic sensor 5 Elastic packer 6 TV camera (borehole BTV camera)
7 Log logging cable 8 Measuring instrument 8a Pulley 9 Cable drum 10 Data processing device 11 Logging controller 12 Cable 13 Cable 14 Cable 15 Data logger 16 BTV video deck 17 Pumping means 17a Pumping pump 18 Pumping pipe 18a Flow rate for measuring pumped amount 19 cables 20 water level gauge

Claims (8)

When an internal water flow type sonde with a built-in water flow sensor is inserted into the underground excavation hole and the change in water flow is measured along the depth of the hole, the outer wall of the sound passage is located on the outer circumferential surface of the hole. A ground logging method for groundwater conditions, in which a slidable elastic packer is attached between the two and a constant amount of groundwater is pumped from the hole or a constant amount of water is supplied into the hole . The groundwater status logging method according to claim 1, wherein the water flow sensor is a flow meter using an electromagnetic flow meter. The groundwater level logging method according to claim 1, wherein the water flow rate sensor is a flow meter using an ultrasonic flowmeter. A borehole television (BTV) camera is attached to the tip of the sonde, and the wall surface in the hole can be observed with a monitor installed on the ground. Running water logging method. An internal water flow type sonde with a built-in water flow sensor, a logging cable connected to the sonde, a data processing device that performs data processing via the logging cable, and a fixed amount of groundwater pumped from the inside of the hole Or a groundwater or water supply means for supplying a constant amount of water into the hole at all times. A groundwater logging system that is equipped with a packer. 6. The groundwater status logging apparatus according to claim 5, wherein the water flow sensor is a flow meter using an electromagnetic flow meter. 6. The groundwater status logging apparatus according to claim 5, wherein the water flow sensor is a flow meter using an ultrasonic flowmeter. The borehole television (BTV) camera is attached to the tip of the sonde, and the wall surface condition in the hole can be observed with a monitor installed on the ground. Running water logging equipment.

Images