JPS58200188A - Bed-detecting method for detecting area and state of flow of underground water - Google Patents

Abstract

PURPOSE:To perform detection accurately and simply in a short time by a method wherein a water-intercepting hollow insulation pipe serving as a guide pipe for moving a sonde vertically is inserted into a well to separate water in the well completely from the inside of the pipe and measurement is conducted in the state wherein the turbulence of the water in the well is prevented completely. CONSTITUTION:On the outer surface of an insulation electrode pipe 5 made of polyvinyl chloride or the like and separating water in a well completely from the inside of the pipe, a number of electrodes in the shape of a screw or the like are arranged at symmetrical positions on the circumference and in the longitudinal direction at appropriate intervals for measurement. A contact measurement rod 9 is inserted into the insulation electrode pipe 5 and lowered down to the bottom of the pipe. Then, while a specified constant current is made to flow between current electrodes A and B from a measuring unit, the rod is pulled up sequentially and a potential generated at each position of the electrodes is measured as a potential difference between the potential M and the electrode N. By this method, the turbulence of the water in the well can be prevented completely, and thus the detection can be performed accurately and simply in a short time.

Description

[Detailed Description of the Invention] This invention provides a method for determining the location of groundwater flowing in a geological formation;
The present invention relates to a well logging method for measuring and detecting flow conditions such as flow range and flow velocity in a wellbore by an electrical resistivity method or an induced electromagnetic method without disturbing the flow of water in the borehole.

Construction of underground structures and foundations such as tunnels, dams, and bridges in civil engineering work, investigation and countermeasures for slope failure and ground damage in disaster prevention work, countermeasures against ground subsidence, and pumping of groundwater use underground water retention aquifers. It is extremely important to accurately understand the underground and groundwater flow conditions. Therefore,
Currently, various survey methods are considered, and in particular, after considering the survey target conditions, electrical logging, temperature logging, radioactivity logging,
Microflow-velocity logging, salt logging, etc. are being selectively implemented. However, although each of these methods has significant characteristics, it is difficult to directly investigate the flow of groundwater due to insufficient detection capabilities, cumbersome operation and handling, and time-consuming measurements. There are drawbacks such as too much.

In the normal logging method using a sonde that moves suspended inside a borehole,
The movement of the sonde and capsule disturbs the weak flow of groundwater flowing into and out of the borehole, making detection impossible. Salt logging, which is used when the amount of water is large, has excellent detection ability, but because it has a large number of electrodes, it requires multi-core wires, which makes the electrodes extremely heavy and limits the fixed length on multiple sides. There are disadvantages such as switching the electrodes is troublesome and time consuming.

The well logging method of the present invention eliminates the above-mentioned drawbacks and difficulties, and pushes inward the water-blocking hollow insulated tube that serves as a guide tube for moving the sonde up and down into the wellbore, thereby separating the borehole water and the inside of the tube. The feature is that it is possible to measure changes over time in electrical resistivity and conductivity associated with groundwater flow of electrolyte-dissolved water in the hole, while being isolated and completely preventing disturbance of the water in the hole due to the movement of sondes and cables. This means that exactly,
Moreover, it has the advantage of being able to be detected easily and in a short time.

The well logging method of the present invention will be described in detail below. There are two methods of measurement for the layer, depending on the arrangement of current electrodes (A, B) and potential types m (M, N): two-pole method (normal method) and three-pole method (lateral method), but in the present invention, The principle is exactly the same for the three-pole method, so we will explain the case where the two-pole method is adopted.In the two-pole method of electric logging, one of the current electrodes A is the hole electrode and the other B is the ground electrode. A rectangular wave current (I) is passed between these two electrodes, and as a result, the potential difference (V) in the stratum including the water in the hole is changed between the potential electrode M and the ground surface ground potential electrode separated by an electrode spacing of a from A. The specific resistance value P measured in this case is expressed as P-4x-a'. Therefore, the specific resistance value of the water in the hole when a constant current is passed is Changes can be detected by measuring V.

Therefore, an electrolytic substance 1, such as salt, is introduced into the borehole and dissolved in the borehole water to reduce its electrical resistivity (thus increasing the conductivity). The state of displacement and dilution over time due to local groundwater inflow and flow was measured using the above electric logging method11, and the specific resistance value P
By repeatedly tracking changes in groundwater at specific time intervals, it is possible to detect groundwater flow areas and flow conditions.

However, in the normal electrical logging method, the borehole electrode sonde and the cable line that suspends it are moved within the borehole water, which disturbs the borehole water and disrupts the weak inflow and flow of groundwater. Measurement and detection are almost impossible up to 1.

Therefore, in the present invention, an insulated tube with an electrode attached is inserted into the outside of the borehole, and electrical logging can be performed using a contact measurement frame that freely moves inside the tube without disturbing the water inside the borehole outside the tube. This can be explained with reference to the diagram as follows.

@1 In the figure, ■ indicates the outside of the drilled hole, and ■ indicates the hole where the electrical resistivity value has been lowered to 1/10 to 1/201 or more than the bank ground by dissolving electrolyte 1 such as salt. ↓ indicates groundwater flowing into and out of the borehole from the aqueous layer @.

(0 is an insulated electrode tube made of PVC or the like that isolates the borehole water from the inside of the tube. On its outer surface, screw-shaped electrodes are placed at symmetrical positions on the circumference as shown in Figure 2, and as shown in Figure 1. A large number of samples are arranged at appropriate measurement intervals (usually 5 to 10 cm) in the vertical direction shown.

■ is the contact terminal inside the tube of the electrode ■, and ■ is a disc made of silicone rubber or the like to prevent water leakage from the electrode part.

■ indicates a freely movable contact measurement rod that is inserted into the insulated electrode tube, and includes a spring-like contact [phase] that contacts the in-tube contact terminal of the electrode ■, and a weight @ at the bottom end of the insulated electrode tube. Equipped with

◎ is connected to the electrical resistivity measuring device @ on the earth's surface with take-out cables connected to contacts σ9 and 0, respectively. This measuring instrument can be powered from a power supply of 0 (normally 012V) to a voltage of 150V using a transistor, low frequency inverter, etc.
V~600V, 100~200m+1A.

A current generating part that flows a rectangular wave current of 10 to 40 Hz between the borehole current electrode [phase], that is, K, and the ground current electrode @, that is, 8, and the potential generated by this current is passed between the borehole potential electrode @, that is, M, and the ground surface. It consists of a potentiometer section that performs rectification and measurement using a ground potential electrode qψ, ie, N.

(f) is an appropriate interval for the insulated electrode tube (for example, 50" to 10"
A fin-like disk-shaped piece made of rubber etc. attached with
The purpose is to suppress and prevent the upward and downward flow of pressurized groundwater in the borehole as much as possible, and to accurately grasp the horizontal flow of groundwater. Do it like this.

1) Pour an electrolyte such as salt into the borehole water and stir to dissolve it, and check its electrical resistivity to 1/l of the ground.
O~1/20. v or less.

11) Insert the insulated electrode tube (2) continuously into the hole for the required length. □° 111
1) Insert the contact measuring rod into the insulated electrode tube and let it drop at the tube bottom 1, then raise it sequentially while passing a specified constant current between current electrodes A and B from the measuring device, and measure the generated potential at each electrode position M.

This is measured as the potential difference between N and this is the initial measured value (displayed as measured potential V value, v/I-R value).

In addition, the FOP-4xa.- value is appropriately selected).

iv) The above measurement in 111) is repeated several times at specific elapsed time intervals (for example, every 5 minutes) to measure the change in resistivity based on displacement dilution caused by groundwater inflow/flow of water in the electrolyte dissolution hole.

■) Display the above measurement results on a diagram, and analyze the flow area and flow state of groundwater from the locations where the resistivity value increases over time and the amount of change.

In addition, in measurements when the outside of the hole is deep, water with high resistivity that does not dissolve electrolyte substances is poured into the insulated electrode tube to prevent the tube from floating and water from entering the hole, but this does not affect the measurement. There is no inconvenience.

FIG. 3 is an example of tracking groundwater flow in an alternating clay/sand layer area of an alluvial layer using the well logging method of the present invention.
Changes over time in the specific resistance of electrolyte (salt) dissolving water in the pores
From the increase, the groundwater flow state within the sand layer can be easily determined.

(2) Well logging method using the induced electromagnetic method The induced electromagnetic method uses the principle of electromagnetic induction to measure the conductivity or specific resistance value of a stratum, and is also used as an in-hole logging method.

The measurement principle is that when a constant high-frequency alternating current is passed through the transmitter coil and the surrounding conductive strata are excited, vortices are created in the stratum and a so-called ground roof is formed, which in turn creates a secondary magnetic field that is directed to the receiver coil by mutual induction. It induces a voltage that is proportional to the electrical conductivity of the surrounding strata, so the structure and condition of the strata can be logged from changes in that voltage. In this case, the receiving coil has a resistance component proportional to the conductivity of the stratum and a resistance component of 90%.
Since an inductive component having a phase difference of ' is detected as a composite voltage, the inductive component is usually removed by a phase discrimination circuit.

Apparent conductivity σa measured by this induction electromagnetic method
is expressed by the following equation.

σa−aWIIFW101+FI10anllFn10σe
'Fe count Fw+Fl +Fn+Fs-1 here 1
σW, σ1. σn, J hole mud water, mud water infiltration hole mud water liquid mud water intrusion area electric rate, Fw, Fl, Fa.

Fei is a geometric coefficient of each.

Normal induction electromagnetic logging uses an auxiliary coil in addition to the two main coils, and is designed to minimize the influence of muddy water columns and adjacent layers, and the measured values are based on borehole water, muddy water, and muddy water. It is unique in that it targets the true conductivity of the strata, which is not affected by the infiltrated area.

In the case of the present invention, contrary to the above-mentioned characteristics, the conductivity σW of the borehole water itself is mainly measured. ), and equipment design such as selecting and setting the transmitter coil excitation frequency to a high frequency range (for example, 100,100 KHz-I) is necessary. Measures must be taken to prevent agitation of water in the borehole due to movement of the logging sonde and the cables connected to it. Therefore, in the present invention, equipment designed to meet the above conditions is used (7. An insulating guide tube is placed in which the inside of the tube is isolated from the water inside the hole where the electrolyte is dissolved outside the hole, and the inside of the tube is isolated from the inside of the tube. By inserting and moving a layer sonde, it is possible to measure changes and decreases in electrical conductivity over time due to the inflow and flow of groundwater without disturbing the water inside the borehole outside the pipe.

This can be explained with reference to the diagram as follows.

In Fig. 4, ■ indicates the area outside the drilled hole, and ■ indicates the electrical resistivity obtained by dissolving an electrolytic substance, such as salt, to 1/10 to 1/20 of the background. (4) schematically shows the underground water that flows into and out of the hole from the aqueous layer (2).

Separates the inside of the pipe from the water inside the electrolyte dissolution hole.
This is a submersible hollow insulated pipe made of λ/PVC, etc., which serves as a guide for the logging sonde 0, and its surface has a surface that prevents the upward and downward flow of pressurized groundwater into the borehole. Suppression and prevention E7: In order to accurately grasp the horizontal flow of underground water, fin Akita plate-shaped packers made of rubber or the like are arranged and installed at appropriate intervals.

♀Φ is a well logging sonde, which is equipped with a transmitter @ and a transmitting coil), a receiving coil [phase] and a preamplifier @ appropriately separated from this.

It is connected to a measuring device on the ground using a shielded signal extraction cable. This III regulator is equipped with necessary electric circuits such as an amplification circuit and a phase discrimination circuit, and the measured conductivity (or specific resistance display) value is recorded on the recorder@. It has become. In addition, [stock]
is the power supply.

The well logging method of the present invention with the above configuration is performed as follows.

I) Electrolytic substances such as common salt are poured into the borehole water, stirred, dissolved and filtered, and the electrical resistivity value is 1/10 of the pack ground.
- 1/2o or less to impart conductivity.

11) Insert an insulated tube [phase] equipped with a fin Akita plate packer to serve as a guide for the logging sonde into the outside of the hole.

111) After inserting the logging sonde [phase] inside the insulated tube and lowering it at the tube bottom 1, power is supplied from the power supply box and the measuring instrument [Co., Ltd.], the transmitter is operated, and a predetermined signal is emitted from the inside of the transmitting coil. An electromagnetic wave with an excitation frequency is emitted, and a voltage proportional to the conductivity of the surrounding water in the borehole is sent to the receiving coil [phase] based on the secondary magnetic field created by the ground loop [phase] caused by the eddy current generated in the borehole water and the stratum.
After amplification with a preamplifier [phase], the logging sonde is pulled up at hole 1 while measuring and recording with a measuring device on the ground surface, and this is taken as the initial measurement value.

+v) The measurement operation in 11:) above is repeated several times at specific elapsed time intervals (for example, every 5 minutes), and the conductivity (
or specific resistance value).

■) Display the above measurement results in a diagram, and analyze the flow area and flow state of groundwater from the area where the electrical conductivity decreases over time (or the area where the resistivity value increases over time) and the amount of change.

In addition, for measurements when the outside of the hole is deep, water with high resistivity that does not dissolve electrolytes is poured into the insulated tube inserted outside the hole to prevent the tube from floating and water from entering the hole. , there is no problem in measurement.

Figure 5 shows an example in which groundwater flow in weathered andesite with developed cracks was investigated using the logging method of the present invention.In order to make the measured values easier to see, the specific resistance value, which is the reciprocal of the electrical conductivity, is used as an indicator. As8. It is expressed in units of I. As can be seen from the figure, the flow area and flow state of groundwater can be easily determined in detail.

[Brief explanation of the drawing]

(1) Fig. 1 shows the configuration of each part and operating conditions regarding the well logging method using the resistivity method of the present invention, and Fig. 2 shows details of the cross section of the electrode part and the contact. FIG. 3 shows an example of the results obtained using the well logging method of the present invention. (2) Fig. 4 shows the configuration of each part and operation status of the well logging method using the induction electromagnetic method of the present invention, and Fig. 5 shows an example of the implementation results. Patent applicant: Toshio Yamaguchi, President of Meiji Consultant Co., Ltd., 3vA, 1, Figure 5

Claims (2)

[Claims] (1) An insulated tube made of PVC or other material is used to separate the inside of the tube from the water in the hole in which an electrolytic substance has been dissolved to lower the electrical resistivity. A large number of electrodes are arranged circumferentially or vertically to form an insulated electrode tube, and plate-shaped fins, ζ-shaped fins, etc. are placed at appropriate intervals on the outer surface of this tube to suppress the upward and downward flow of water in the hole. Attach a large number of
This is connected and inserted into a wellbore, and a contact measurement frame that moves freely while simultaneously contacting multiple electrodes is inserted into this tube, and moves continuously at a specific time, thereby detecting localized areas from within the stratum. Changes and increases in resistivity are measured without disturbing the flow of water in the borehole based on the time-dependent displacement and dilution of electrolyte dissolution water in the borehole due to the inflow and flow of groundwater, and the results are used to determine the flow area of groundwater. - Logging method to detect flow conditions. (2) The outer surface of an insulated pipe made of PVC or other material is used to isolate the inside of the pipe from the water inside the pipe, which has an electrolyte dissolved therein to reduce the electrical resistivity and increase the electrical conductivity, to suppress the upward and downward flow of the water inside the hole. A large number of fin and Akita board-shaped puff cars, etc., are arranged at appropriate intervals and inserted into the borehole, and an induction electromagnetic logging sonde equipped with a high-frequency transmitting coil and a receiving coil is inserted into this insulated tube. , the flow of water in the borehole continuously moves at specific time intervals, and describes the state of decrease in conductivity due to the replacement and dilution of electrolyte dissolving water in the borehole over time due to the inflow and flow of local groundwater from within the formation. By measuring without disturbing the
A logging method for detecting groundwater flow areas and flow conditions.