JPH0152706B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a groundwater logging method and apparatus for analyzing geological structure from the state of groundwater flow in a borehole.

By drilling a borehole in the ground and measuring the flow of groundwater within this borehole,
There is a groundwater logging method that analyzes geological structures. As devices for measuring the flow velocity in a borehole, a micro resistivity meter and an in-hole microcurrent meter are conventionally known.

The method using a microresistivity meter involves injecting salt water into a borehole, then stirring it using an air pump etc. so that the salt water concentration is uniform with respect to depth, and measuring changes in the depth distribution of this salt water concentration over time inside the borehole. This method estimates the spring point of groundwater by detecting the specific resistance value of water. However, with this method, it is not only difficult to uniformly stir the salt water, but also because the salt water concentration (i.e., resistivity value) changes over time, it is not possible to obtain a degree of dilution proportional to the amount of spring water. The error in determining the points became large, and it was also very difficult to detect the points where groundwater entered the ground.

In the method using an in-hole microcurrent meter, a tachometer with a small propeller is installed on a logging sonde hanging into a borehole, and the vertical flow velocity in the borehole is measured by the rotation of this propeller. Accordingly, well logging is conducted. However, with this method, due to the characteristics of the tachometer, it is impossible to detect very small flow velocities, and the error is large.
Additionally, since only the velocity of laminar flow in the vertical direction is normally measured, turbulent water flow near groundwater spring points or inflow points into the ground cannot be detected, making accurate logging difficult. Ta.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a groundwater logging method and apparatus that can significantly improve the accuracy of geological structure analysis.

In order to achieve this purpose, this invention
While measuring the depth distribution of groundwater temperature in a borehole, multiple temperature-sensing elements are installed in the water flow section of the logging sonde, and these temperature-sensing elements measure the flow velocity and depth distribution in the flow direction. Measure these water temperatures,
It is designed to analyze geological structures by comparing flow velocity and depth distribution in the flow direction. The present invention will be explained in detail below based on the drawings.

FIG. 1 is a diagram showing the state of measurement according to the present invention;
FIG. 2 is a perspective view showing one embodiment of the logging sonde used in the present invention, FIGS. 3 and 4 are longitudinal sectional views of a reservoir forming tube and a vertical component measuring tube, respectively. Moreover, FIG. 5 is a main circuit diagram.

In Fig. 1, reference numeral 1 denotes a borehole drilled approximately perpendicular to the ground, 2 a support installed at the opening of the borehole 1, 3 a wire, and 10 a wire inserted into the borehole 1 by means of the wire 3. The logging sonde is suspended, and 50 is a measuring instrument. Thermistors as various temperature-sensing elements to be described later are attached to the well-logging sonde 10, and these temperature-sensing elements and the measuring device 50 are electrically connected via wires 3. Note that 4 in the figure indicates the water level in the borehole 1.

As shown in Figs. 1 and 2, the logging sonde 10 is
Four wire materials 12a, 12b, 12c, 12d connecting the wire 3 and the weight 11, and an upper ring 13 fixed between these wire materials 12a to 12d so as to push open these wire materials 12a to 12d. A reservoir forming body is attached to the lower ring 14 and the upper ring 13 by four wire-like connecting members 15 (only three are shown in FIG. 2) so as to be located approximately in the center of the upper ring 13. 20, and the wire materials 12a to 12a located between the upper ring 13 and the lower ring 14.
A vertical component measuring tube 40 is attached to 12d by four wire-like connecting members 16 (only three are shown in FIG. 2), and a vertical component measuring tube 40 that crosses the lower ring 14
A book wire material 17 is provided.

As shown in FIG. 3, the reservoir forming body 20 includes an outer cylinder 21 and an inner cylinder 22. The outer cylinder 21 is open at the lower end, and a lid plate 24 in which a number of small holes 23 are formed is fixed to the upper end. A cover plate is fixed to the upper and lower ends of the inner cylinder 22, respectively, and is held within the outer cylinder 21 by a member (not shown) so as to be spaced apart from the inner wall of the outer cylinder 21. A plurality of water passage openings 25 are formed in the pipe wall of the inner cylinder 22 and the lid plate at the upper end. A temperature detection thermistor 26 as a temperature sensing element is held in the upper part of the inner cylinder 22, and a sensitivity compensation thermistor 27 is held in the lower part so as to be located substantially on the center line of the inner cylinder 22.

Therefore, when the well logging sonde 10 is gently lowered into the borehole 1, the inside of the reservoir forming body 20 is filled with groundwater. Even if underground water flows vertically or is disturbed, the flow is suppressed within the outer cylinder 21 and the inner cylinder 22, and the ground water accumulates there. Note that since the outer tube 21 is formed with a small hole 23, the groundwater in the outer tube 21 is gradually replaced with the groundwater in the outer tube 21, but the inner tube 22
Since the flow of water inside the inner cylinder 22 is smaller, the temperature detection thermistor 26 inside the inner cylinder 22 can detect the water temperature almost unaffected by the flow of water.

As shown in FIG. 4, the vertical component measuring tube 40 consists of a tube 41 with open upper and lower ends, and this tube 41 is attached to the logging sonde 10 by the connecting member 16 so as to be perpendicular to the well logging sonde 10. . Inside this cylinder 41, there is a thermistor 42 for detecting flow velocity in a constant direction as a heat radiation detection type temperature sensing element located on the center line of the cylinder 41, and a thermistor 42 located above this thermistor 42 for detecting the direction of flow together with this thermistor 42. A detection thermistor 43 is held, respectively.

Reference numeral 45 denotes a maximum flow velocity detecting thermistor as a heat radiation detecting type temperature sensing element, and this thermistor 45 is attached to the substantially central position of the wire material 17 of the lower ring 14 (FIG. 1).

Each thermistor 26, 27, 42, 43 and 45 is connected to a measuring device 50 as shown in FIG. This measuring device 50 is connected to each of these thermistors to form a Wheatstone bridge. In this figure, 51 is a DC power supply;
A variable resistor 52 is connected in series with this DC power source, and a resistor 53 and a variable resistor 5 are connected to both ends A and B of the series circuit of the DC power source 51 and the variable resistor 52.
4 and a resistor 55 are connected in parallel. Reference numerals 56, 57, and 58 are interlocking type changeover switches, each having terminals a, b, c, and d.

When terminal a of each switch 56, 57, 58 is connected, the series circuit of the temperature detection thermistor 26 and the fixed resistor 59 is connected in parallel to the points A and B, while the intermediate point between the thermistor 26 and the fixed resistor 59 is connected in parallel to the points A and B. and the middle tap of the variable resistor 54 are the galvanometer 60 and the sensitivity compensation thermistor 27.
connected by a series circuit with That is, a Wheatstone bridge for detecting the temperature of underground water is formed, and the temperature of the water depth where the thermistor 27 is located can be detected from the scale of the galvanometer 60.

When the terminals b of the switches 56, 57, and 58 are connected, the thermistor 45 for maximum flow rate detection is connected in place of the resistor 59 in the Wheatstone bridge for temperature detection. Since this thermistor 45 is disposed in a flowing part of the water flow, the amount of heat dissipated changes depending on the speed of the water flow, and the temperature of the thermistor 45 changes. There is a certain relationship between this temperature and the flow rate, and on the other hand, the resistance value changes greatly depending on the temperature, so the flow rate can be measured from the change in the resistance value. That is, a Wheatstone bridge for detecting the maximum flow velocity is formed.

When the terminals c of the switches 56, 57, and 58 are connected, the thermistor 42 for detecting a constant direction flow velocity is connected in place of the thermistor 45 for detecting the maximum flow velocity. This thermistor 42 is connected to the vertical component measuring tube 40.
Since the measuring tube 40 is disposed inside the measuring tube 40, the flow velocity of the water flow passing through the measuring tube 40 can be measured. That is, a Wheatstone bridge is formed for measuring the vertical component of the flow velocity.

The temperature detection thermistor 26 in each of the Wheatstone bridges for detecting the maximum flow velocity and vertical component has the function of compensating for fluctuations in the measured value of the flow velocity due to changes in water temperature.

When the terminals d of the switches 56, 57, and 58 are connected, the direction detection thermistor 43 is connected in place of the vertical component measurement thermistor 26. Therefore, based on the temperature difference caused by interference between the thermistors 42 and 43, the direction of the needle of the galvanometer 60 changes depending on whether the direction of the water flow is upward or downward. In other words, a Wheatstone bridge is formed for detecting the direction of water flow.

In order to perform well logging with the well logging device configured as described above, the logging sonde 10 must be set at various depths within the borehole 1 by switching the changeover switches 56, 57, and 58. The water temperature T, maximum flow velocity Vm, vertical component velocity Vv of the flow velocity, and flow direction of the water flow at that depth may be measured by switching.

Figure 6 shows an example of measurement when there is no groundwater flow. In this case, since there is no water flow, the water temperature T is approximately the ground temperature, and this water temperature T increases monotonically with depth, while the maximum flow velocity Vm and The vertical component Vv is zero.

FIG. 7 shows an example of measurement when there is a flow, and it is clear from the temperature distribution that groundwater at a constant temperature is flowing vertically inside the borehole 1. In the same figure, the vertical component of the flow velocity Vv
The direction of flow is indicated by an arrow. That is, an upward arrow indicates an upward flow, and a downward arrow indicates a downward flow. Near point A in the figure, there is a large difference between the maximum flow velocity Vm and the vertical component Vv, so it can be determined that there is a spring layer and the water flow is turbulent.The groundwater at a constant temperature in this spring layer is The flow rises in the borehole 1 as a laminar flow.
It can be seen that near point ro, where the water temperature changes, the difference between the maximum flow velocity and the vertical component increases again, and the groundwater flows into the ground in a turbulent flow.

Figure 8 shows the groundwater flow situation based on the measurement results shown in Figure 7.

FIG. 9 shows another measurement example where there is groundwater flow, and a plurality of spring water layers exist in the ground in this measurement example. That is, it is clear from the depth distribution of water temperature T that there are spring water layers with different water temperatures near point C and point D in the figure. In this measurement example, the area near the point near the water surface is the inflow layer to the ground.

In the embodiment described above, the maximum flow velocity Vm and the vertical component Vv are measured as the flow velocity, so depending on the difference between the two velocities Vm and Vv, the magnitude of the horizontal component of the flow velocity, in other words, the water flow. It is now possible to determine the degree of disturbance, making it possible to perform more accurate well logging. However, it goes without saying that in this invention, the desired effect can be obtained even if only one of the flow velocities, for example, the maximum flow velocity, is measured.

In addition, in this embodiment, the vertical component forming pipe 40 disposed approximately vertically allows the vertical component Vv of the flow velocity to be
However, by changing the inclination of this tube 40, it is also possible to measure the flow velocity component in the desired direction of inclination, and by measuring components of the flow velocity in various directions in this way, more detailed information can be obtained. Well logging is also possible.

Furthermore, in the apparatus of this embodiment, a thermistor for detecting temperature, flow velocity, and flow direction is attached to one well logging sonde, so it is possible to perform measurements efficiently in a short time. This method also includes cases in which geological structures are analyzed by measuring these separately using separate well logging sondes and comparing the results.

Further, the reservoir forming body 20 of this embodiment has an outer cylinder 21.
Although the inner cylinder 22 is used as the inner cylinder 22, the structure may be as shown in FIGS. The reservoir forming body 20A shown in FIG. 10 has a plurality of small holes 72 formed in the upper end cover 71 of a cylindrical body 70 whose lower end is open, and a porous elastic body 74 such as urethane foam having a cavity 73 inside. is loaded into this cylindrical body 70, and the thermistors 26 and 27 are arranged within this cavity 73. Note that the aperture ratio of the porous elastic body 74 is determined so that it has an appropriate water flow resistance that does not suppress the flow of water within the cavity 73.

The reservoir forming body 20B shown in FIG. Thermistors 26 and 27 are disposed at.

The reservoir forming body 20c shown in FIG.
was buried.

As shown in FIGS. 10 to 12, the porous elastic body 7
By using No. 4, 76, 77, and 80, it becomes possible to sufficiently suppress the flow of water with a very simple structure.

As described above, this invention sequentially measures the depth distribution of groundwater temperature, the flow velocity, and the depth distribution in the direction of flow using thermosensors, and compares these measurement results to determine geological structure. Since the configuration is configured to perform analysis, analysis accuracy can be significantly improved.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the state of measurement using an apparatus according to an embodiment of the present invention, Fig. 2 is a perspective view of the logging sonde, Fig. 3 is a longitudinal cross-sectional view of the reservoir forming body, and Fig. 4 is A vertical cross-sectional view of the vertical component measuring pipe, Figure 5 is a main circuit diagram, Figure 6 is a diagram showing a measurement example when there is no flow of groundwater, Figure 7 is a diagram showing a measurement example when there is flow, FIG. 8 is a diagram showing the groundwater flow situation based on the measurement results of FIG. 7, and FIG. 9 is a diagram showing another example of measurement when there is flow. Also, 10th to 1st
FIG. 2 is a sectional view showing another embodiment of the reservoir forming body. 1... Borehole, 10... Logging sonde, 20
...Retention part forming body, 26...Temperature detection thermistor,
42... Thermistor for detecting flow velocity in a constant direction, 43... Thermistor for detecting direction, 45... Thermistor for detecting maximum flow velocity, 50... Measuring instrument.

Claims (1)

[Claims] 1. While measuring the depth distribution of groundwater temperature in a borehole, a plurality of temperature-sensing elements installed in the water flow section of a logging sonde measure the flow velocity and depth of the groundwater in the flow direction. A groundwater logging method that is characterized by analyzing the geological structure by measuring the water temperature, flow velocity, and depth distribution in the flow direction. 2. Consisting of a logging sonde suspended into a borehole and a measuring instrument, the logging sonde includes a stagnation part forming body that forms a stagnation part of the water flow, and a stagnation part forming body disposed within the stagnation part forming body. and a heat radiation detection type temperature sensing element for detecting flow velocity and a direction detection temperature sensing element disposed in the water flow section of the well logging sonde, and the measuring instrument comprises: A groundwater logging device characterized by comprising a bridge circuit that detects water temperature, flow velocity, and flow direction based on the outputs of these temperature sensing elements.