CN110865246B

CN110865246B - Porous monitoring system and method for fracture diffusion electric field intensity

Info

Publication number: CN110865246B
Application number: CN201910970108.6A
Authority: CN
Inventors: 陈国能; 曾强
Original assignee: Guangdong Zhongda Institute Of Geosciences Co ltd
Current assignee: Guangdong Zhongda Institute Of Geosciences Co ltd
Priority date: 2019-10-12
Filing date: 2019-10-12
Publication date: 2022-02-11
Anticipated expiration: 2039-10-12
Also published as: CN110865246A

Abstract

The invention relates to a porous monitoring system and a porous monitoring method for the strength of a fracture diffusion electric field. The porous monitoring system for the fracture diffusion electric field intensity comprises a plurality of reference electrodes, a plurality of superficial electrodes, a monitoring instrument and computing equipment, wherein each reference electrode and at least two superficial electrodes form a plurality of groups of monitoring channels; the reference electrode is arranged in a fracture zone below the surface of the bedrock, the superficial electrodes are arranged in superficial soil layers in the fracture upper plate or the fracture lower plate, and the monitoring instrument detects the electro-physical quantity difference between the reference electrode in each group of monitoring channels and the electro-physical quantity detected by each superficial electrode and sends the electro-physical quantity difference to the computing equipment; and the computing equipment performs interpolation of the equal difference points of the electro-physical quantities on each group of monitoring measuring channels, and outlines equipotential lines of the fracture diffusion electric field in the superficial soil layer according to the equal difference points of the electro-physical quantities. The porous monitoring system for the fracture diffusion electric field intensity can accurately monitor the intensity change of the fracture diffusion electric field.

Description

Porous monitoring system and method for fracture diffusion electric field intensity

Technical Field

The invention relates to the field of ground electric field detection, in particular to a porous monitoring system and method for the electric field intensity of fracture diffusion.

Background

The fracture electric field refers to an electric field distributed in and near a fracture zone, and as shown in fig. 1, a prerequisite for the formation of the fracture electric field is the existence of compressive stress, and the compressive stress is the interaction force of two fractured disk blocks, which can be clarified from the origin of an earthquake. The stress concentration is used for explaining the pressure source in the piezoelectric effect forming the fracture electric field, and then the piezoelectric minerals which are orderly arranged are needed. The fact that the depth of the continental earthquake source is more than 5-25km in the so-called continental earthquake layer shows that the stress concentration point on the fracture surface mainly appears in the deep part of the crust 5-25km below the surface, and the depth is the distribution range of the granite layer. Therefore, when the fracture is cut to the depth range, orderly arranged quartz minerals are necessarily present, and the piezoelectric effect is naturally generated when stress concentration occurs on the two disks of the fracture, namely the source of an electric field in the fracture. According to the principle, the broken piezoelectric part is an obstruction part which is on the section and is used for preventing the two broken discs from moving relatively, and is a potential earthquake-generating source, namely a pregnant earthquake part. The intensity of the fracture electric field is therefore only related to the stress of this obstacle, while the size of the obstacle depends on the roughness of the fracture, independently of the mechanical and kinematic properties of the fracture.

As shown in fig. 2, the piezoelectric effect of the pregnant part can be regarded as a "power source", however, the power source may exist under the earth's surface for several kilometers or even tens of kilometers, and a human must have a "wire" for observing the power source on the earth's surface, and the "wire" is a fracture itself. According to the existing ultra-deep drilling data, the deep part of the land crust still has water, and the water can be used as a current carrier in the fracture of crack development, and the piezoelectric current generated in the deep part of the fracture can reach a shallow area due to the good conductivity of the current carrier, so that a fracture electric field is formed.

The strength of different parts of the fracture electric field is different, and the electric field strength is larger as the fracture electric field is closer to a power supply. Relative to the interior of the fractured zone, the upper and lower discs have a much lower water content than the fractured zone itself due to the failure of the fracture to develop, so that the two discs are substantially insulated. When the piezoelectric current in the fracture zone is conducted to the surface, it will contact with the superficial water to generate "leakage phenomenon". In other words, the pre-earthquake electrical anomaly measured by the above methods is essentially a "leakage electric field" (see fig. 2) formed by the radiation effect of the fracture electric field in the shallow aquifer, and the "leakage electric field" is essentially the extension of the fracture electric field at the surface region. We will refer to this as the shallow earth diffusion electric field of the fracture electric field, hereinafter referred to as the fracture diffusion electric field. The existing natural electric field method cannot accurately detect the strength change of the fracture diffusion electric field.

Disclosure of Invention

Accordingly, an object of the present invention is to provide a porous monitoring system and method for fracture diffusion electric field strength, which can monitor the strength variation of fracture diffusion electric field relatively accurately.

In a first aspect, an embodiment of the present invention provides a porous monitoring system for fracture diffusion electric field intensity, including:

the device comprises a plurality of reference electrodes, a plurality of superficial electrodes, a monitoring instrument and a computing device, wherein each reference electrode and at least two superficial electrodes form a plurality of groups of monitoring channels;

the reference electrodes are respectively installed in a fracture zone below the bedrock surface through detection drill holes;

the at least two superficial electrodes in a group of monitoring channels are jointly installed in a superficial soil layer in the upper fracture disc or the lower fracture disc, the at least two superficial electrodes are not located on a straight line consistent with the fracture breaking and carrying direction at the same time, or the magnitude of the electrical physical quantity difference between each superficial electrode and the reference electrode is different but the variation trend is consistent;

the monitoring instrument is respectively connected with the reference electrode and each superficial electrode in each group of measuring channels, detects the electro-physical quantity difference between the reference electrode and the electro-physical quantity detected by each superficial electrode in each group of monitoring measuring channels, and sends the electro-physical quantity difference to the computing equipment;

And the computing equipment performs interpolation of equal difference points of the electro-physical quantity on each group of monitoring measuring channels from the fracture surface of the earth surface along the arrangement direction of the at least two superficial electrodes in each group of monitoring measuring channels by adopting an interpolation method according to the electro-physical quantity difference, and connects the equal difference points of the electro-physical quantity of different groups of monitoring measuring channels with each other, so that equipotential lines of fracture diffusion electric fields in superficial soil layers are drawn.

Further, in the same group of monitoring channels, the vertical projection of each superficial electrode on the ground and the vertical projection of the reference electrode on the ground are positioned on the same straight line;

the computing equipment computes the electrical physical quantity difference between every two adjacent superficial electrodes on the same straight line according to the physical quantity difference between the reference electrode and each superficial electrode in the monitoring channel; calculating a unit distance electro-physical quantity attenuation value between the vertical projections of the two superficial electrodes on the ground according to the electro-physical quantity difference between the two adjacent superficial electrodes and the distance between the vertical projections of the two superficial electrodes on the ground; and performing interpolation of equal difference points of the electro-physical quantities between the vertical projections of the two superficial electrodes on the ground according to the unit distance electro-physical quantity attenuation value;

The computing device also interpolates the difference point of the electric physical quantity between the fracture-fracture surface of the earth surface and the superficial electrode closest to the fracture-fracture surface of the earth surface on the line according to the attenuation value of the electric physical quantity of the unit distance between the two superficial electrodes closest to the fracture-fracture surface of the earth surface, and interpolates the difference point of the electric physical quantity in the direction of the superficial electrode farthest from the fracture-fracture surface of the earth surface away from the fracture-fracture surface on the line according to the attenuation value of the electric physical quantity of the unit distance between the two superficial electrodes farthest from the fracture-fracture surface of the earth surface.

Further, the vertical projection of each superficial electrode on the ground in different groups of monitoring traces and the vertical projection of the reference electrode on the ground are positioned on a straight line which is parallel to each other.

Further, the monitoring traces in different groups comprise a common superficial electrode, and in the monitoring traces comprising the common superficial electrode, the vertical projection of each superficial electrode in at least one group of monitoring traces on the ground is not on the same straight line as the vertical projection of the reference electrode on the ground;

for the same group of monitoring channels, the vertical projection of each superficial electrode on the ground and the vertical projection of the reference electrode on the ground are not on the same straight line simultaneously, the computing equipment projects the vertical projections of the superficial electrodes in the group of monitoring channels on the ground to a straight line along the direction consistent with the fracture and fragmentation directions, wherein the straight line passes through the vertical projection of one of the superficial electrodes on the ground and the vertical projection of the reference electrode on the ground; calculating the electro-physical quantity difference between every two adjacent superficial electrodes projected to the same straight line according to the electro-physical quantity difference between the reference electrode and each superficial electrode in the group of monitoring channels; calculating a unit distance electro-physical quantity attenuation value of the two superficial electrodes projected on the straight line according to the electro-physical quantity difference between every two adjacent superficial electrodes and the distance of the two superficial electrodes projected on the straight line, and interpolating an electro-physical quantity equal difference point between the two superficial electrodes projected on the straight line according to the unit distance electro-physical quantity attenuation value;

The computing device also interpolates the difference point of the electric physical quantity between the fracture crushing surface of the earth surface and the superficial electrode closest to the fracture crushing surface of the earth surface on the straight line according to the unit distance electric physical quantity attenuation value between the two superficial electrodes closest to the fracture crushing surface of the earth surface after projection, and interpolates the difference point of the electric physical quantity in the direction of the superficial electrode farthest from the fracture crushing surface of the earth surface away from the fracture crushing surface on the straight line according to the unit distance electric physical quantity attenuation value between the two superficial electrodes farthest from the fracture crushing surface of the earth surface after projection.

In a second aspect, embodiments of the present invention provide a method for monitoring porosity of fracture diffusion electric field intensity, including the following steps:

acquiring an electro-physical quantity difference between the reference electrode in each group of monitoring channels and the electro-physical quantity detected by each superficial electrode from a monitoring instrument, wherein each reference electrode in a plurality of reference electrodes and at least two superficial electrodes in a plurality of superficial electrodes form at least one group of monitoring channels; the reference electrode is installed in a fracture zone below the bedrock face through a probe borehole; the at least two superficial electrodes in a group of monitoring channels are jointly installed in a superficial soil layer in the upper fracture disc or the lower fracture disc; the at least two superficial electrodes are not positioned on a straight line consistent with the direction of the fracture and fragmentation belt at the same time, or the magnitude of the difference of the electrical physical quantities between each superficial electrode and the reference electrode is different but the variation trends are consistent; the monitoring instrument is respectively connected with the reference electrode and each superficial electrode in each group of measuring channels and detects the electro-physical quantity difference between the reference electrode and the electro-physical quantity detected by each superficial electrode in each group of monitoring measuring channels;

Performing interpolation of equal difference points of the electrical physical quantity on each group of monitoring measuring channels from the broken fracture surface of the earth surface along the arrangement direction of the at least two superficial electrodes in each group of monitoring measuring channels by adopting an interpolation method according to the electrical physical quantity difference;

and connecting the electro-physical quantity equal difference points of different groups of monitoring and measuring channels with each other, thereby outlining an equipotential line of a fracture diffusion electric field positioned in a shallow soil layer.

Further, if the vertical projection of each superficial electrode on the ground and the vertical projection of the reference electrode on the ground are located on the same straight line in the same group of monitoring traces, the method further comprises:

calculating the electrical physical quantity difference between every two adjacent superficial electrodes on the same straight line according to the physical quantity difference between the reference electrode and each superficial electrode in the group of monitoring channels;

calculating a unit distance electro-physical quantity attenuation value between the vertical projections of the two superficial electrodes on the ground according to the electro-physical quantity difference between the two adjacent superficial electrodes and the distance between the vertical projections of the two superficial electrodes on the ground;

and performing interpolation of equal difference points of the electric physical quantity between the vertical projections of the two superficial electrodes on the ground according to the unit distance electric physical quantity attenuation value.

Further, still include:

interpolating an equal difference point of the electric physical quantity between the fracture surface of the earth surface and the shallow electrode closest to the fracture surface on the straight line according to the unit distance electric physical quantity attenuation value between the two shallow electrodes closest to the fracture surface of the earth surface;

and performing interpolation of the equal difference points of the electric physical quantity on the direction of the superficial electrode farthest from the fracture crushing surface of the earth surface away from the fracture crushing surface on the straight line according to the unit distance electric physical quantity attenuation value between the two superficial electrodes farthest from the fracture crushing surface of the earth surface.

Further, if the monitoring traces in the different groups include a common superficial electrode, and in the monitoring traces including the common superficial electrode, a vertical projection of each superficial electrode in at least one group of monitoring traces on the ground is not located on the same straight line simultaneously with a vertical projection of the reference electrode on the ground, the method further includes:

aiming at the same group of monitoring channels, wherein the vertical projection of each superficial electrode on the ground and the vertical projection of the reference electrode on the ground are not on the same straight line simultaneously, the vertical projections of the superficial electrodes in the group of monitoring channels on the ground are projected to the same straight line along the direction of the fracture and fragmentation, wherein the straight line passes through the vertical projection of one superficial electrode on the ground and the vertical projection of the reference electrode on the ground;

Calculating the electro-physical quantity difference between every two adjacent superficial electrodes projected to the same straight line according to the electro-physical quantity difference between the reference electrode and each superficial electrode in the group of monitoring channels;

calculating the unit distance electro-physical quantity attenuation value of the two superficial electrodes projected on the straight line according to the electro-physical quantity difference between every two adjacent superficial electrodes and the distance of the two superficial electrodes projected on the straight line,

and interpolating equal difference points of the electric physical quantity between the projections of the two superficial electrodes on the straight line according to the unit distance electric physical quantity attenuation value.

Further, still include:

according to the unit distance electro-physical quantity attenuation value between two shallow electrodes which are closest to the fracture surface of the earth surface after projection, interpolation of the electro-physical quantity equal difference points is carried out between the fracture surface of the earth surface and the shallow electrode closest to the fracture surface on the straight line;

and performing interpolation of difference points such as the electro-physical quantity on the direction of the superficial electrode farthest from the fracture surface of the earth surface far away from the fracture surface on the straight line according to the unit distance electro-physical quantity attenuation value between the two superficial electrodes farthest from the fracture surface of the earth surface after projection.

In the embodiment of the application, at least one group of monitoring channels are arranged in a fracture fragmentation zone and a fracture upper disc or lower disc, a monitoring instrument detects an electro-physical quantity difference between a reference electrode and a plurality of superficial electrodes in the fracture fragmentation zone, a computing device draws equipotential lines of a fracture diffusion electric field of the fracture upper disc or fracture lower disc superficial soil layer by an interpolation method according to the electro-physical quantity difference, the equipotential lines are perpendicular to electric field lines, the density degree of the equipotential lines can reflect the speed of potential change in the electric field, and the denser the equipotential lines are, the electric potential in the electric field is reduced to the next level by a shorter distance, and the electric field intensity is smaller; the more sparse the equipotential lines are, the more the potential in the electric field is reduced to the next level through a longer distance, and the larger the electric field intensity is, so that the intensity change of the fracture diffusion electric field of the upper fracture disk or the lower fracture disk shallow soil layer can be monitored by monitoring the density degree of the equipotential lines in real time in the application of earthquake monitoring, the monitoring of the intensity of the fracture electric field generated by the piezoelectric effect of the pregnant and earthquake part is indirectly realized, and the accuracy of fracture stability evaluation is improved.

For a better understanding and practice, the invention is described in detail below with reference to the accompanying drawings.

Drawings

FIGS. 1 and 2 are schematic diagrams illustrating the principle of the formation of the breaking electric field;

FIG. 3A is a schematic diagram of the structure of a porosity monitoring system of the present invention showing the strength of fracture-diffusion electric field in one exemplary embodiment;

FIG. 3B is a schematic diagram of the structure of a porosity monitoring system of the present invention showing the strength of fracture-diffusion electric field in an exemplary embodiment;

FIG. 4 is a schematic illustration of the internal connections of a porosity monitoring system of the present invention showing the strength of fracture-diffusion electric field in an exemplary embodiment;

FIGS. 5A and 5B are schematic views of drill placement locations for monitoring a borehole shown in an exemplary embodiment;

FIG. 6 is a schematic illustration of interpolation of electrical physical quantity isodyne points in a fractured fracture zone shown in an exemplary embodiment;

FIG. 7 is a schematic structural view of a porosity monitoring system of the present invention showing the strength of fracture-diffusion electric field in an exemplary embodiment;

FIG. 8 is a schematic structural view of a porosity monitoring system of the present invention showing the strength of fracture-diffusion electric field in an exemplary embodiment;

FIG. 9 is a flow chart of a porosity monitoring method of the present invention for fracture diffusion electric field strength shown in one exemplary embodiment;

FIG. 10 is a schematic diagram of fracture diffusion electric field equipotential lines of a stable electric field region delineated according to the principles of an embodiment of the present application;

fig. 11 is a schematic diagram of fracture diffusion electric field equipotential lines of an unstable electric field region delineated according to the principles of an embodiment of the present application.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some but not all of the relevant aspects of the present invention are shown in the drawings.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

It is to be understood that although the terms first, second, third, etc. may be used herein to describe various information, these information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present invention. The word "if" as used herein may be interpreted as "at … …" or "when … …" or "in response to a determination", depending on the context.

The existing natural electric field method is essentially to observe the 'electric leakage phenomenon' which is a fracture diffusion electric field, when the measuring channel of the natural electric field method is obliquely cut or vertically fractured and spread, the electrical abnormity occurs, so that the careless arrangement of the earth electric channel on the earth surface is the root cause of unreliable earth electric observation.

Since the conductivity of the intact rock is very low, much smaller than the fracture zone rich in free water, the conductor of the current in the fracture zone can be considered as free water. From the basic principle of electricity and the model shown in fig. 2, it can be known that the fracture electric field has two main characteristics: firstly, in a fracture zone, the farther a place is away from a piezoelectric point in a space position, the smaller the field intensity is, the smaller the current value is, and the smaller the voltage is; secondly, in the ground surface fracture diffusion electric field, the intensity of the fracture electric field is attenuated from the fracture zone to the two disks, and the attenuation speed of the two disks in the fracture zone is greater than that in the fracture zone.

Based on the principle, when the stress of the pregnant earthquake area is accumulated, the power of the power supply is increased. Therefore, the power of the power supply, namely the stress accumulation condition, can be calculated back by observing the change amplitude (voltage difference or current difference) of the electric field in the fracture zone and on the disk and combining various geological physical quantities to compare the background electric field. However, this method can only do detection, and cannot do true monitoring.

The application provides a porous monitoring system of fracture diffusion electric field intensity can monitor the intensity variation of fracture diffusion electric field.

Fig. 3A, fig. 3B and fig. 4 are schematic structural diagrams of a porous monitoring system of fracture propagation electric field intensity in an embodiment of the present application, in the present embodiment, the porous monitoring system of fracture propagation electric field intensity includes reference electrodes a, a ', superficial electrodes B, c, B', c ', a monitoring instrument e and a computing device f, the reference electrodes a and a' are used for detecting the electrophysical quantity in fracture and fracture zones, and the superficial electrodes B, c, B ', c' are used for detecting the electrophysical quantity in a superficial soil layer.

In fig. 3 and the following drawings, the connection line between the two monitoring electrodes indicates that the two monitoring electrodes form a group of monitoring channels, and does not mean that the two monitoring electrodes are directly communicated through a wire.

The porous monitoring system for the fracture diffusion electric field intensity in the embodiment is suitable for construction of a single monitoring station. The range of interest for a single monitoring station should be limited to the visual range of the naked eye in open space, such as a school, or a building.

The fracture zone corresponding to the porous monitoring system for fracture propagation electric field strength in the embodiment is not only a tensile fracture zone, but also the same for reverse fracture and slip fracture (corresponding to compressive fracture zone and torsional fracture zone), because the fracture electric field is generated regardless of the mechanical property and the kinematic property of fracture and only related to the roughness of fracture surface (explained in the foregoing theory). The fracture zone is a regional deep fracture for controlling landform, old stratum dislocation can be seen by naked eyes, or small ore control fractures or filling dikes are not considered, because the fractures, fractures or faults can not cause large-scale tectonic earthquakes.

The vertical projection of the reference electrode a on the ground and the vertical projections of the superficial electrodes b and c on the ground are positioned on the same straight line, and a group of monitoring traces abc is formed, wherein the group of monitoring traces specifically comprises a trace ab formed by the reference electrode a and the superficial electrode b and a trace ac formed by the reference electrode a and the superficial electrode c; the vertical projection of the reference electrode a ' on the ground and the vertical projections of the superficial electrodes b ' and c ' on the ground are positioned on another straight line and form another group of monitoring traces ab ' c ', which specifically comprise a trace a ' b ' formed by the reference electrode a ' and the superficial electrode b ' and a ' c ' formed by the reference electrode a ' and the superficial electrode c '.

In other examples, the monitoring traces may also be a plurality of groups, each group of monitoring traces includes different reference electrodes, the number of the superficial electrodes in each group of monitoring traces may also be a plurality of more than two, the vertical projection of the superficial electrodes in each group of monitoring traces on the ground may also be different from the vertical projection of the reference electrodes on the ground, as long as it is ensured that each superficial electrode is not simultaneously located on a straight line consistent with the fracture and fracture direction or the magnitude of the difference in the electrical physical quantity between each superficial electrode and the reference electrode is different, but the variation trend is consistent.

In this embodiment, a straight line where the vertical projection of the reference electrode a on the ground and the vertical projections of the superficial electrodes b and c on the ground are located is parallel to a straight line where the vertical projection of the reference electrode a ' on the ground and the vertical projections of the superficial electrodes b ' and c ' on the ground are located, so that porous monitoring of the fracture diffusion electric field strength in the region can be uniformly achieved.

As shown in fig. 3A, the reference electrodes a and a' are installed in the fracture zone below the bedrock face through different probe boreholes. In order to prevent the collapse of the fourth tied stratum and the weathered base stratum and the influence of the change of the shallow water layer on the detection drill holes A and B, the detection drill holes A and B are provided with casings for preventing collapse and water separation at corresponding hole sections of the fourth tied stratum and the weathered base stratum.

In some examples, the sleeve includes a steel layer and a PVC layer, the steel layer being wrapped around the PVC layer. As shown in fig. 5A and 5B, the drill placement position of the monitor drill hole depends on the shape of the fractured zone, and the higher the fracture shape, the closer the opening position is to the fractured zone.

The shallow electrodes b, c, b 'and c' are installed in a shallow soil layer in one of the upper fracture disc and the lower fracture disc, the shallow electrodes b, c, b 'and c' have no installation depth requirement, in some examples, the shallow electrodes b, c, b 'and c' only need to be simply buried in the soil layer, but the electrodes are prevented from being exposed on the ground surface, and the isolation of artificial electromagnetic radiation is better if the isolation can be achieved.

As shown in fig. 5, the monitoring instrument e is respectively connected to each reference electrode and each superficial electrode through a cable, and a voltage or current detection circuit is disposed in the monitoring instrument e, and is configured to detect, in real time, an electro-physical quantity difference between an electro-physical quantity detected by the reference electrodes a and a' in a fracture and fragmentation zone and an electro-physical quantity detected by each superficial electrode in a corresponding monitoring and detection zone in a superficial soil layer, and send the electro-physical quantity difference to the computing device f.

And the computing equipment f performs interpolation of equal difference points of the electro-physical quantity on each group of monitoring measurement channels from the fracture surface of the fracture zone on the earth surface along the arrangement direction of the at least two superficial electrodes in each group of monitoring measurement channels by adopting an interpolation method according to the difference of the electro-physical quantity, namely performs interpolation of equal difference points of the electro-physical quantity along the directions of the superficial electrodes b and c and along the directions of the superficial electrodes b 'and c', and draws out an equipotential line of the fracture diffusion electric field in the superficial soil layer according to the equal difference points of the electro-physical quantity of each group of monitoring measurement channels. The dotted lines along the fracture zone in fig. 3B are equipotential lines of the fracture diffusion electric field outlined in the embodiment of the present application.

The computing equipment f can be a computer or a server or special experimental equipment, analysis software is installed in the computer, and interpolation of the electro-physical quantity and drawing of the fracture diffusion electric field equipotential lines of the superficial soil layer can be completed.

The electrophysical quantity equipartition point may be a point in each group of monitoring traces where the electrophysical quantity difference between the fracture surface is the same, if the number of the monitoring traces is 2, for example, two groups of monitoring traces, abc and a ' b ' c ' in this embodiment, the computing device f connects the electrophysical quantity equipartition points of the two groups of monitoring traces in this embodiment or the other embodiments with each other, so as to draw out an equipotential line of the fracture diffusion electric field in the superficial soil layer, and in an area outside the connection range of the electrophysical quantity equipartition points, an equipotential line of the fracture diffusion electric field in the superficial soil layer may be drawn out in a direction consistent with the fracture zone. If the distances of the different electrical physical quantity equiphase difference points are far, when the electrical physical quantity equiphase difference points are connected, the equipotential lines of the fracture diffusion electric field positioned in the superficial soil layer between the two electrical physical quantity equiphase difference points can be additionally drawn along the direction consistent with the fracture breaking away direction, that is, the computing equipment f connects the electrical physical quantity equiphase difference points of the two groups of monitoring measuring channels in the embodiment or other embodiments with each other along the direction consistent with the fracture breaking away direction.

The equipotential lines are vertical to the electric field lines, the density degree of the equipotential lines can reflect the speed degree of potential change in the electric field, and the denser the equipotential lines are, the potential in the electric field is reduced to the next level by a shorter distance, which indicates that the electric field intensity is smaller; the more sparse the equipotential lines, the more the potential in the electric field decreases over a longer distance to the next level, indicating a greater electric field strength.

The electrical physical quantity in the present application may be a current and/or a voltage, and the following description will be made with reference to the voltage, that is, the electrical physical quantity difference is a voltage difference between the reference electrode and each superficial electrode, and the difference point of the electrical physical quantity is a difference point of the voltage.

As shown in fig. 6, fig. 6 is a schematic diagram of interpolation of difference points such as an electrophysical quantity by an interpolation method according to an electrophysical quantity difference between an electrophysical quantity detected by a reference electrode in a fractured fracture zone and an electrophysical quantity detected by each superficial electrode in a superficial soil layer in an embodiment of the present application, a superficial electrode b, a superficial electrode c and a reference electrode a are projected in a straight line in a vertical direction on the ground, a voltage difference Δ Uab and Δ Uac between a measured ab and a measured ac can be obtained by a monitoring instrument, and Δ Ubc, that is, a voltage difference between the superficial electrodes b, c can be obtained by subtracting the two values, and since distances (l1, l2) between the superficial electrodes b, c and the reference electrode a in the vertical projection on the ground are known, the distance between the electrode b and the electrode c in the vertical projection on the ground is also known and is denoted as l 3; in an ideal situation, if the voltage is varied at regular intervals, the variable can be represented by Δ Ubc/l3, and the attenuation variable dU of the voltage difference, which is the attenuation value of the electro-physical quantity per unit distance, is obtained in millivolts/meter (mV/m). Since Δ Ubc is a vector, all voltage changes in the fracture boundary, i.e. the fracture surface of the earth's surface, in the (bc) direction can be determined by the product of dU and l leaving the fracture boundary. Therefore, the interpolation is not a direct potential line of the electric field, but a difference point of the electric physical quantity, that is, a difference point of the voltage.

The interpolation can be interpolation of set voltage difference, namely, the voltage difference between two adjacent interpolation points is the set voltage difference, interpolation is carried out in a sequence that the voltage difference between each interpolation point and the fracture crushing surface is increased, if a plurality of groups of monitoring channels exist, the interpolation points which are the same in voltage difference with the fracture crushing surface in each group of monitoring channels are connected, and equipotential lines of the fracture diffusion electric field in the superficial soil layer can be drawn.

In other examples, the interpolation may also be a set distance interpolation, that is, the set distance between two adjacent interpolation points is the same, and the interpolation is performed in an order that the set distance between each interpolation point and the fracture and crush surface increases, if there are multiple sets of monitoring channels, after interpolation is performed between each set of monitoring channel and the fracture and crush surface by the set distance, the interpolation points with the same voltage difference are connected to draw the equipotential lines of the fracture and diffusion electric field in the shallow soil layer.

In fig. 6, interpolation is performed between the superficial electrodes bc by setting the interpolation distance l, and since the interpolation distance l is controllable, the size of each segment of voltage isodyne is directly dependent on Δ Ubc, i.e., the measured values of Δ Uab and Δ Uac. dU-573 mV-422 mV)/10 m-15.1 mV/m; and (6) interpolation. Taking the interpolation at intervals of 2m as an example, the voltage difference of the first interpolation point between the superficial electrodes b and c is 422mV +15.1mV/m × 2 m-452.2 mV.

And (b) excluding bc, using extrapolation, for example, the voltage difference of the first interpolation point between the superficial electrode b and the fractured fracture surface is 422mV-15.1mV/m × 2 m-391.8 mV; the voltage difference of the superficial electrode c away from the first interpolation point outside the fracture surface is 573mV +15.1mV/m 2 m-603.2 mV.

In other examples, there may be other superficial electrodes between the superficial electrode b with the smallest voltage difference with the reference electrode a and the superficial electrode c with the largest voltage difference with the reference electrode a, so that the computing device calculates the voltage difference between each two adjacent superficial electrodes on the same straight line according to the voltage difference between the reference electrode and each superficial electrode in the group of monitoring traces; calculating a unit distance electro-physical quantity attenuation value between the vertical projections of the two superficial electrodes on the ground according to the voltage difference between the two adjacent superficial electrodes and the distance between the vertical projections of the two superficial electrodes on the ground; and interpolating equal difference points of the electric physical quantity between the vertical projections of the two superficial electrodes on the ground according to the unit distance electric physical quantity attenuation value.

The computing device also interpolates a voltage isodyne point between the fracture-fracture surface of the earth surface and the superficial electrode closest to the fracture-fracture surface of the earth surface on the line according to the unit distance electro-physical quantity attenuation value between the two superficial electrodes closest to the fracture-fracture surface of the earth surface, and interpolates a voltage isodyne point in a direction in which the superficial electrode farthest from the fracture-fracture surface of the earth surface is far away from the fracture-fracture surface on the line according to the unit distance electro-physical quantity attenuation value between the two superficial electrodes farthest from the fracture-fracture surface of the earth surface.

In other examples, the attenuation variable dU may also be a function of the distance l, i.e. a non-uniform variation. Then dU can be calculated more accurately by differentiation, which is basically consistent with the concept of acceleration differentiation, except that the latter is the change in velocity over time.

In some application scenarios, due to the limitation of the terrain or the saving of the drilling cost, it may not be possible to arrange all the vertical projections of the superficial electrodes in one group of monitoring traces to be on the same straight line with the vertical projection of the reference electrode, or to have the condition of burying the superficial electrodes, and in this condition, the present application also proposes another solution, in which a common superficial electrode may be included in different groups of monitoring traces, and in the monitoring traces including the common superficial electrode, the vertical projection of each superficial electrode in at least one group of monitoring traces on the ground and the vertical projection of the reference electrode on the ground may not be on the same straight line at the same time.

In another embodiment, as shown in fig. 7, the fracture-diffusion-electric-field porous monitoring system of the present application includes reference electrodes a, a' and superficial electrodes b, c. The superficial electrodes b and c are used as common electrodes to form two groups of monitoring channels with the reference electrodes a and a' respectively.

In other examples, only one superficial electrode may be used as the common electrode, or a greater number of superficial electrodes may be used as the common electrode.

In fig. 7, the superficial electrodes b and c are not located on the same straight line with the fracture-breaking direction at the same time, and the magnitude of the difference in the electrical physical quantity between each superficial electrode and the reference electrode is different, the superficial electrodes b and c in this embodiment are located on the same straight line with the detecting electrode a installed in the borehole a, and the superficial electrode b is not located on the same straight line with the reference electrode a' and the superficial electrode c. In other examples, the superficial electrode b may not be co-located on the same straight line with the reference electrode a and the superficial electrode c at the same time.

When the voltage equal difference point in the embodiment is interpolated, the computing device projects the vertical projection of the superficial electrode in the group of monitoring measurement on the ground to a straight line along the fracture and fracture zone to a consistent direction, wherein the straight line passes through the vertical projection of one of the superficial electrodes on the ground and the vertical projection of the reference electrode on the ground. In fig. 7, the computing device projects the superficial electrode b onto a line where the reference electrode a 'and the superficial electrode c are located, forming a virtual electrode b'.

The computing equipment computes the electro-physical quantity difference between every two adjacent superficial electrodes projected to the same straight line according to the electro-physical quantity difference between the reference electrode a ' and each superficial electrode in the group of monitoring measuring channels a ' b ' c; and calculating the unit distance electro-physical quantity attenuation value of the two superficial electrodes projected on the straight line according to the electro-physical quantity difference between every two adjacent superficial electrodes and the distance of the two superficial electrodes projected on the straight line, and interpolating the equal difference point of the electro-physical quantities between the two superficial electrodes projected on the straight line according to the unit distance electro-physical quantity attenuation value.

In an exemplary embodiment, as shown in fig. 8, the porous monitoring system for fracture propagation electric field intensity in the present embodiment monitors not only one of the upper fracture disk or the lower fracture disk but also both of the upper fracture disk and the lower fracture disk. In this embodiment, a plurality of reference electrodes are arranged in the fracture and fragmentation zone, and a plurality of superficial electrodes are respectively arranged on the fracture upper plate and the fracture lower plate, wherein the arrangement requirements and the number of the reference electrodes and the superficial electrodes are the same as those of the plurality of superficial electrodes in the previous embodiment when one of the fracture upper plate and the fracture lower plate is monitored. Preferably, the superficial electrodes on which the upper and lower rupture discs are arranged are symmetrically arranged as shown in fig. 8. The computing device performs interpolation of the electrical physical quantity equipoise points on each group of monitoring traces from the fracture surface of the earth surface along the arrangement direction of the at least two superficial electrodes in each group of monitoring traces, and outlines the equipotential lines of the fracture diffusion electric field in the superficial soil layer according to the electrical physical quantity equipoise points of each group of monitoring traces, which is also the same as the implementation manner in the above embodiment, and therefore, the implementation manner is not repeated.

Based on the same principle as the porous monitoring system of fracture propagation electric field strength in the above embodiment, the present invention also provides a porous monitoring method of fracture propagation electric field strength, as shown in fig. 9, which is executed by the computing device in the above embodiment and includes the following steps:

Step S101: acquiring an electro-physical quantity difference between the electro-physical quantities detected by the reference electrode and each superficial electrode in each group of monitoring channels from a monitoring instrument;

each reference electrode in the plurality of reference electrodes and at least two superficial electrodes in the plurality of superficial electrodes form at least one group of monitoring channels; the reference electrode is installed in a fracture zone below the bedrock face through a probe borehole; the at least two superficial electrodes in a group of monitoring channels are jointly installed in a superficial soil layer in the upper fracture disc or the lower fracture disc; the at least two superficial electrodes are not positioned on a straight line consistent with the direction of the fracture and fragmentation belt at the same time, or the magnitude of the difference of the electrical physical quantities between each superficial electrode and the reference electrode is different but the variation trends are consistent; the monitoring instrument is respectively connected with the reference electrode and each superficial electrode in each group of measuring channels and detects the electro-physical quantity difference between the reference electrode and the electro-physical quantity detected by each superficial electrode in each group of monitoring measuring channels;

step S102: performing interpolation of equal difference points of the electrical physical quantity on each group of monitoring measuring channels from the broken fracture surface of the earth surface along the arrangement direction of the at least two superficial electrodes in each group of monitoring measuring channels by adopting an interpolation method according to the electrical physical quantity difference;

Step S103: and connecting the electro-physical quantity equal difference points of different groups of monitoring and measuring channels with each other, thereby outlining an equipotential line of a fracture diffusion electric field positioned in a shallow soil layer.

In an alternative embodiment, if the vertical projection of each superficial electrode on the ground and the vertical projection of the reference electrode on the ground are located on the same straight line in the same group of monitoring traces, the method further comprises:

In an optional embodiment, further comprising:

In an alternative embodiment, the vertical projection of each of the superficial electrodes on the ground in the different sets of monitoring traces and the vertical projection of the reference electrode on the ground are parallel to each other.

In an alternative embodiment, if the monitoring traces including the common superficial electrode in the different groups include a plurality of monitoring traces, and in the monitoring traces including the common superficial electrode, a vertical projection of each superficial electrode in at least one group of monitoring traces on the ground is not located on the same straight line simultaneously with a vertical projection of the reference electrode on the ground, the method further includes:

In an optional embodiment, further comprising:

As for the method embodiment, since it is basically similar to the system embodiment described above, the description is simple, and the relevant points can be referred to the partial description of the system embodiment.

In the system and the method for monitoring the fracture diffusion electric field intensity, at least one group of monitoring channels are arranged in a fracture zone and an upper fracture disc or a lower fracture disc, a monitoring instrument detects the electro-physical quantity difference between a reference electrode and a plurality of superficial electrodes in the fracture zone, a computing device draws equipotential lines of a fracture diffusion electric field of the upper fracture disc or the lower fracture disc by adopting an interpolation method according to the electro-physical quantity difference, the equipotential lines are vertical to electric field lines, the density degree of the equipotential lines can reflect the speed of electric potential change in the electric field, and the denser the equipotential lines are, the electric potential in the electric field is reduced to the next level by a shorter distance, and the electric field intensity is smaller; the more sparse the equipotential lines are, the more the potential in the electric field is reduced to the next level through a longer distance, and the larger the electric field intensity is, so that the intensity change of the fracture diffusion electric field of the upper fracture disk or the lower fracture disk shallow soil layer can be monitored by monitoring the density degree of the equipotential lines in real time in the application of earthquake monitoring, the monitoring of the intensity of the fracture electric field generated by the piezoelectric effect of the pregnant and earthquake part is indirectly realized, and the accuracy of fracture stability evaluation is improved.

Fig. 10 and 11 are schematic diagrams of fracture diffusion electric field equipotential lines outlined in a monitoring region by a fracture diffusion electric field strength porous monitoring system and method according to an embodiment of the present application. The fracture electric field and the diffusion electric field are different in size between the fractures in the monitored area, depending on the geological background. However, if the fracture electric field or the diffusion electric field of each fracture in the monitored region does not continuously increase the electric indexes (electric field intensity, electric potential intensity, current magnitude, etc.) such as the field intensity for a certain period of time, we can judge that the region is basically stable as far as now. In FIG. 10, the fracture electric field and the fracture propagation electric field are referred to as normal electric fields. As shown in fig. 11, when the monitored value of a certain fracture in a certain area is continuously strengthened in duration and non-human disturbance is confirmed, it can be said that the fracture has activity as far as present and the activity is continuously increased with the time. According to the principle of formation of the fracture electric field and the fracture diffusion electric field, the activity is mainly shown in that when the electrical indexes (electric field intensity, electric potential intensity, current magnitude and the like) for monitoring the fracture diffusion electric field are used, the magnitude of the electrical indexes is increased or the electric field range is increased (the potential line in the electric field in fig. 11 is enlarged or the value is increased continuously). This phenomenon in which the intensity of the breaking electric field increases with time is called an abnormal electric field. Second, the anomalous electric field of a fracture may only occur in one segment of a certain fracture, since the fractures in the region are cut from each other.

According to the principle, a fracture electric field monitoring station comprising a plurality of real-time monitoring electrodes can be arranged at different positions of each fracture in the area. A monitoring network is formed by a large number of monitoring stations, the fracture diffusion electric field of each fracture in a monitoring area is obtained, the equipotential lines of the fracture diffusion electric field are sketched on a fracture layout in a monitoring system in real time, and then which fracture electric field is stronger and weaker in the area and the real-time change of the field intensity can be known. The activity of the fracture in the zone is thus evaluated and the stability of the crust of the zone is obtained.

Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

It will be understood that the invention is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.

Claims

1. A porous monitoring system for the strength of fracture propagation electric field, comprising:

the device comprises a plurality of reference electrodes, a plurality of superficial electrodes, a monitoring instrument and a computing device, wherein each reference electrode and at least two superficial electrodes form at least one group of monitoring channels;

The computing equipment performs interpolation of equal difference points of the electro-physical quantities on each group of monitoring measuring channels from the fracture surface of the earth surface along the arrangement direction of the at least two superficial electrodes in each group of monitoring measuring channels by adopting an interpolation method according to the electro-physical quantity difference, and connects the equal difference points of the electro-physical quantities of different groups of monitoring measuring channels with each other, so that equipotential lines of fracture diffusion electric fields in superficial soil layers are drawn;

in the same group of monitoring channels, the vertical projection of each superficial electrode on the ground and the vertical projection of the reference electrode on the ground are positioned on the same straight line;

2. The porous monitoring system of fracture propagation electric field strength of claim 1, characterized in that:

the vertical projection of each superficial electrode on the ground in different groups of monitoring measuring channels and the vertical projection of the reference electrode on the ground are positioned in a straight line which is parallel to each other.

3. The porous monitoring system of fracture propagation electric field strength of claim 1, characterized in that:

the monitoring channels comprising the common superficial electrodes are arranged in different groups, and in the monitoring channels comprising the common superficial electrodes, the vertical projection of each superficial electrode in at least one group of monitoring channels on the ground is not on the same straight line with the vertical projection of the reference electrode on the ground;

4. A porous monitoring method for the electric field intensity of fracture diffusion is characterized by comprising the following steps:

Connecting the electrical physical quantity equal difference points of different groups of monitoring and measuring channels with each other, thereby outlining an equipotential line of a fracture diffusion electric field positioned in a shallow soil layer;

wherein, if the vertical projection of each superficial electrode on the ground and the vertical projection of the reference electrode on the ground are located on the same straight line in the same group of monitoring channels, the method further comprises:

performing interpolation of equal difference points of the electro-physical quantities between the vertical projections of the two superficial electrodes on the ground according to the unit distance electro-physical quantity attenuation value;

5. The method for monitoring porosity of fracture propagation electric field intensity according to claim 4, wherein:

6. The method of claim 4, wherein if the monitoring traces in different groups include a common superficial electrode, and in the monitoring traces including the common superficial electrode, a vertical projection of each superficial electrode in at least one group of monitoring traces on the ground surface is not located on the same straight line as a vertical projection of the reference electrode on the ground surface, the method further comprises:

7. The method for monitoring porosity of fracture propagation electric field intensity according to claim 6, further comprising: