RU2363965C1 - Method designed to monitor local irregularities and geodynamic zones of geological section top part (gst) - Google Patents

Abstract

FIELD: instrument making.

SUBSTANCE: invention relates to geophysics, particularly, to electromagnetic LF methods intended for analysing GST. Proposed method comprises the following steps. Three antennas are used to measure mutually-orthogonal components Hx, Hy, Hz of natural Earth electromagnetic field in frequency range of f=1-200 kHz, as well as, at least, two transceivers and one master station, operated in synchronism. Note here that transceivers are arranged stationary at the GST surface, while the master station, identical to transceiver devices, is located outside the surface under analysis. Signals comprising data on Hx, Hy, Hz components are transmitted from transceivers and master station to data processing device, whereat the data is subjected to noise compensation processing. Parametres W and S are computed to decide on availability of local geological irregularities and geodynamic zones in GST zone.

EFFECT: higher validity, expanded performances.

2 cl, 2 dwg

Description

The invention relates to geophysics, in particular to low-frequency electromagnetic methods for studying the upper part of the geological section of the VChR, intended for monitoring and predicting the stress-strain state (VAT) of a rock mass based on the study of variations in the Earth’s natural electromagnetic field (EEMPZ). It can be used for revealing and contouring in profile surveys of local geoelectric heterogeneities (flooded troughs, karst cavities, landslide areas, areas of mine underworking, increased fracturing, intervals of weakened rocks, etc.). This invention can be specially used when organizing a monitoring network for operational control of VAT in the areas of gas transmission systems in areas of activation of dangerous geological and technological processes. The results of such monitoring find practical application for an objective assessment and forecasting of the degree of risk, ensuring the safety of operation of critical gas facilities and timely management decisions.

Since dynamically active zones, as a rule, are indicators of potential sources of accidents and disasters, constant monitoring in real time of changes in the VAT of the landslide massif, including, for example, gas pipelines, is an urgent task.

In rocks, under the action of mechanical stresses, electromagnetic pulses following one after another arise in a wide spectrum of frequencies. Impulse parameters depend on the efficiency of defect formation in rocks and determine the kinetics of latent crack formation. It has been established that changes in VAT lead to changes in pore fluid pressure, groundwater filtration mode, which is also accompanied by the appearance of an electrokinetic current, and hence a magnetic field. The fields induced in conductive inclusions are superimposed on the VAT fields caused by variations of the Earth's natural field. These, as well as other natural and technogenic fields, lead to inconstancy of the total magnetic components (Hz, Hx, Hy) in space and time (the Z axis is vertical, the X and Y axes are in the horizontal plane, orthogonal to the Z axis). Moreover, by Hz, Hx, Hy we mean the difference between the absolute values of the components at all ordinary measured i-th points of the surface and one reference point.

A known method of analyzing geodynamic processes, in which variational stations are placed, synchronously register signals of changes in the pulsed electromagnetic field in time, which are used to judge the geodynamic process. In this method, signals from artificial and natural non-geodynamic sources are pre-compensated, signals are recorded in a frequency band of ± 5 kHz in the range of 15-50 kHz, the signal intensities are averaged in the intervals from units of seconds to tens of minutes with a quantization step of the order of averaging time, and autocorrelation function of the difference of the signals of variational stations, determine its three-dimensional spectral power density, by which the energy of the difference of the signals is calculated (USSR copyright certificate 10888508, G01V 3/00, publ. 30.11.1982).

The limitations of this method are low accuracy, informativeness and reliability of the results obtained, limited operational capabilities. To implement this method, you must move one of the variational stations. The results between the first and last measurements are obtained after a significant period of time.

There is also a method of detecting geodynamic zones in a rock mass, which consists in the fact that with a given period of time, the stress-strain state of the rocks is studied, in which the flux density of the natural pulsed electromagnetic field of the Earth is measured by a radio wave indicator at observation points located in a given direction, with a given step, in a given frequency range (Ukrainian patent No. 8085, G01V 3/08, publ. 12/26/1995).

In this method, according to the measurement results, graphs of the values of the flux density of the magnetic component of the Earth’s natural pulsed electromagnetic field are plotted and the presence of abnormal zones in the rock mass is judged by the presence of regular changes in the signal level. Observations of the Earth’s natural pulsed electromagnetic field are repeated with a period equal to the stress relaxation time in the rock mass. In this case, the magnetic component of the signal of the intensity of the Earth’s natural electromagnetic field is measured along the axis of production in three mutually perpendicular directions: longitudinal, transverse and vertical with a step of 1-5 m in the frequency range 150-200 kHz, and judging by the position of the anomalous zones on the graphs the position of the unloading zones or high rock pressure of the massif, due to both natural and technogenic factors. Measurements are carried out by one antenna of a radio wave indicator, which is rotated alternately in three mutually perpendicular positions.

The disadvantages of this method are: low accuracy and reliability of the results, since the measurements are not carried out synchronously, but for a long time by one antenna in a narrow frequency range. This method is ineffective for interpreting field data, since the basis for judging the position of problem areas is the analysis of three separate graphs, and not the product of their joint processing.

As a result of the patent search, no sources of information were identified in which constant monitoring of local heterogeneities and geodynamic zones of the upper part of the geological section was carried out without moving the receiving devices - radio wave indicators or without rotating the antennas of these receiving devices.

The problem solved by the invention is the improvement of technical and operational capabilities.

The technical result that can be obtained by carrying out the invention is to increase the accuracy, reliability and informativeness, expand the functionality by real-time determination of local heterogeneities and geodynamic zones in the field of high frequency and evaluating their energy both in area and in depth.

и

для каждого из приемопередающих устройств,To solve the problem with the achievement of the technical result, a method for monitoring local inhomogeneities and geodynamic zones of the upper part of the geological section of the VChR includes the simultaneous measurement by three antennas in the frequency range f = 1 ÷ 200 kHz of mutually orthogonal components Hx, Hy, Hz of the earth's natural pulsed electromagnetic field (EEMPZ) at least two transceiver devices (magnetovariation stations) synchronously and one reference station, while transceiver the triples are installed stationary in the area of the studied surface of the VCR, and the reference station, identical to the transceiver devices, is outside the zone of the studied surface, signals with data on the components Hx, Hy, Hz are simultaneously transmitted from the transceiver devices and from the reference station to the processing device, in which they compensate for the effect interference by subtracting the corresponding data on the components Hx, Hy, Hz from the receiving devices and from the reference station, calculate the amplitude magnetovariational frequency parameters in the processing device - Wzx (x, y) = Hz / Hx and W zy (x, y) = Hz / Hy, determine the dependences W ₁ zx = F ₁ (f) and W ₂ zy = F ₂ (f) for each of the transceiver devices, these dependencies are integrated, obtaining the area

and

for each of the transceiver devices,

moreover, S ₁ and S ₂ are the generalized electrical characteristics of the VChR in depth, and by the extrema of W ₁ zx, W ₂ zy, S ₁ and S ₂ determine local inhomogeneities and geodynamic zones in the VChR region under the corresponding transceiver devices.

An additional embodiment of the method is possible, in which it is advisable that the acceleration α ~ 1 / s ^{2 of the} change in the parameters W ₁ zx, W ₂ zy, S ₁ and S ₂ be additionally determined in the processing device to assess the development or attenuation of the geodynamic zones of the RF.

These advantages, as well as features of the invention are illustrated by the best option for its implementation with reference to the accompanying drawings.

Figure 1 depicts an arrangement of transceiver devices and a reference station for a portion of a linear pipeline;

Figure 2 is the same as figure 1, for the investigated surface of a large area.

The method is implemented as follows.

On the profile or site of research (figures 1, 2), transceiver devices 1 are permanently installed, measuring the natural electromagnetic field of the Earth (EEMPZ). For ease of reading, figure 1 shows the connection of the transceiver devices 1 with the processing device 3 only for extreme magnetovariational stations of each row. The same transceiver devices 1 reference station (s) 2 are placed on the site, obviously free from geodynamic, geoelectric inhomogeneities, thereby compensating for the effects of natural and man-made interference. The inputs / outputs of the transceiver devices 1 can be connected to the inputs / outputs of the processing device 3 by a cable, a radio channel or satellite communications, etc.

Since the magnetic sensors of the transceiver devices 1 are three antennas with a narrowly directed radiation pattern, the shape of which sharply depends on the anisotropy of the rocks, the antenna located along the X axis for all transceiver devices 1 is sighted in space by a high-precision geodetic theodolite (accuracy not more than 1 minute strictly in one direction). This can be the axis of the preferential orientation of the tectonic elements, or the axis of the main pipeline. Any other methods of sighting antennas when studying the VChR by the ith electromagnetic field (eye, using a compass, compass, etc.) are incorrect, since a viewing error of more than 1 ° entails a measurement error of up to 50% or more.

Then, at a given j-oe time with a certain interval on the network of profile points or areas, the three components of the magnetic field Hx, Hy, Hz are monitored as the difference of signals at the ordinary ith points of the transceiver devices 1 and the reference station 2 in the interval f = 1 ÷ 200 kHz Compensate the influence of model and instrumental interference by the processing device 3 using the measured Hx, Hy, Hz from the reference station 2 to extract useful signals.

Processing device 3 is a server that calculates at least two relative amplitude magnetovariational parameters - Wzx (x, y) = Hz / Hx and Wzy (x, y) = Hz / Hy, which are found from the relationship between the vertical component Hz of the magnetic field and its horizontal components Hx and Hy. Next, graphs of these frequency parameters W ₁ zx = F ₁ (f) and W ₂ zy = F ₂ (f) of the field are constructed, i.e. frequency characteristics of a section of the VChR at one or i-th points. They are the parameters for the geoelectric interpretation, since due to the skin effect, with a decrease in frequency, the depth of the medium under study increases.

The processing device 3 then determines the area S ₁ and S ₂ , which are generalized in depth to the geoelectric characteristics of the medium at the i-th point. Observations by profiles or by area provide a horizontal description of the change in the geological environment.

Thus, by changing the parameters Wizx and Wizy, local heterogeneities and geodynamic zones are judged, and by changing the parameters S ₁ and S _2, lateral heterogeneity is judged. This gives information about the shape, properties, structure, intensity and location of local inhomogeneities, geodynamic zones of high frequency.

When studying these parameters at different times t, the medium is monitored, and by their increments in time Δt, we can estimate the rate of change of the parameters F and S - acceleration α ~ 1 / s ² (development-attenuation of the geodynamic process), which significantly increases the reliability of the forecast of activation of hazardous geological processes.

To increase the reliability of the results of studying VCHR, field measurements and their interpretation are carried out simultaneously using the software installed in the processing device 3, which controls the transceiver devices 1, reference stations 2, collects, transmits information via GSM or satellite radio channels, stores information, its processing and display on the server display in real time.

по формуле:To study low-contrast geoelectrical anomalies, one can use a statistical data processing method, for example, Friedman rank statistics, in which the processing procedure is reduced to ranking the number of pulses of the EIMPZ in the line of the analysis window, including N profiles and m transceiver devices 1 on each of them, summing the obtained ranks each column and calculating Friedman statistics

according to the formula:

- сумма рангов для i-го пикета окна;

- the sum of the ranks for the i-th window picket;

указывает на необходимость суммирования квадратов полученных сумм рангов по всем пикетам.

indicates the need to sum the squares of the obtained rank sums for all pickets.

не превышает величины порога. Использование ранговой статистики Фридмана позволяет повысить чувствительность за счет нелинейного накопления, выделяя слабые сигналы, например, геодинамического характера, а значит, увеличить тем самым и радиус их обнаружения.This value has a Pearson distribution (chi-square) at (m-1) degrees of freedom, when the signal in the window selected for analysis is absent, which allows us to find the threshold value for solving detection problems with a given probability of an unknown signal shape against the background of uncorrelated interference. The hypothesis of radiation from the source of the magnetovariational field is rejected if the found value

does not exceed the threshold value. The use of Friedman's rank statistics makes it possible to increase sensitivity due to nonlinear accumulation, highlighting weak signals, for example, of a geodynamic nature, and therefore, thereby increasing the radius of their detection.

According to the proposed algorithm, it is possible to process the obtained measurement results on one profile. At the same time, the number of profiles of the monitoring network N corresponds to the same number of cycles of parallel measurements along one profile, performed at certain time intervals, which is especially important when studying geodynamic processes.

The identification and contouring of local low-contrast and weak geodynamic anomalies is carried out taking into account the location of the transceiver devices 1 with anomalous Friedman statistics on the monitoring network or the distribution of the rate of change of pulses along the three coordinates Hx, Hy, Hz at different magnetovariational profile stations.

The monitoring technique is as follows.

During the field work, the following data is received:

1) graphs F _i (f) characterizing the change in the electrical resistivity of the rocks (ρ) or their longitudinal conductivity (s = h / ρ, where h is the thickness of the VChR layer with depth (the higher the frequency, the smaller the depth due to the skin effect) at different points (i = 1, 2, 3 ...);

2) graphs F _i (fextr) by profiles or maps (by area) at different points of study of the VChR section (i = 1, 2, 3 ...) by extreme values (max, min) on the graphs F _i (f);

3) graphs and maps S ₁ and S ₂ at all points (i = 1, 2, 3 ...) -S _i ;

4) the rate of change S _i during monitoring (when working at predetermined time intervals (t) - hours, days, months, seasons, etc.

Horizontally and gently sloping geoelectric sections, for example, the landslide body of a coastal slope containing gas pipelines, can be divided into graphs F _i (f), highlighting them with different ρ and s. To do this, use the methodology known in electrical exploration by methods of audio-magnetovariational and frequency studies.

The steeply layered sections of the HF, for example, zones of tectonic disturbances, faults, fracturing, flooding, etc., are divided on the graphs and maps F and S of extreme values (F = fext) or F (identical at all points (i = 1, 2, 3 ...) fconst), as well as those constructed according to S ₁ and S ₂ . The centers of these anomalies (local heterogeneities and geodynamic zones) will lie under the extrema on the graphs and maps, and their width and depth are comparable with the distances on the graphs and maps S ₁ or S ₂ between points (profile or map) at which S is equal to the extremum and half extremum. Further, their semi-quantitative interpretation can be carried out according to the rules known in electrical exploration by induction or radio wave profiling methods.

Since the claimed method for transforming the measured parameters (Hx, Hy, Hz) are normalized reference values of these parameters, synchronous and relative, their theory gives new approaches to interpretations both at characteristic points and using personal computers. To do this, it is necessary to compare experimental plots with theoretical plots for a priori known models of geological environments. Using complex geological and geophysical additional information about the area of work and high-precision measurements of components (Hx, Hy, Hz) by technical means using geophysical theodolites, this method can dramatically improve the information content of monitoring local heterogeneities and geodynamic zones in the upper part of the geological section.

The most successfully claimed method for monitoring local heterogeneities and geodynamic zones of the upper part of the geological section of the VChR is industrially applicable for identifying and contouring in profile surveying of geoelectric local inhomogeneities (karst cavities, old mine workings, basements, undercuts, ceramic pipes, flooded troughs, etc.) and for operational control of VAT in the areas of gas transmission systems in areas of activation of dangerous geological and technological processes (landslide sections of underwater passages, mining areas, landslides, etc.).

Claims (2)

1. A method for monitoring local inhomogeneities and geodynamic zones of the upper part of the geological section of the VChR, including the simultaneous measurement by three antennas in the frequency range f = 1-200 kHz of mutually orthogonal components Hx, Hy, Hz of the earth's natural pulsed electromagnetic field (EEMF) at least two transceiver devices synchronously and one reference station, while transceiver devices are installed stationary in the area of the studied surface of the VCR, and the reference station is identical to the transceiver for incoming devices — outside the area of the studied surface, signals with data on the Hx, Hy, Hz components are simultaneously transmitted from the transceiver devices and from the reference station to the processing device, which compensate for the effect of interference by subtracting the corresponding data on the Hx, Hy, Hz components from the receiving devices and from the reference station, they calculate the amplitude magnetovariational frequency parameters Wzx (x, y) = Hz / Hx and Wzy (x, y) = Hz / Hy in the processing device, determine the dependences W ₁ zx = F ₁ (f) and W ₂ zy = F ₂ (f) for each of the transceiver devices, these dependencies are tegrate, getting the area

and

for each of the transceiver devices, where S ₁ and S ₂ are the generalized electrical characteristics of the RF in depth, and the extremes W ₁ zx, W ₂ zy, S ₁ and S ₂ determine the local inhomogeneities and geodynamic zones in the RF region under the corresponding transceiver devices. 2. The method according to claim 1, characterized in that the processing device further determines the acceleration α ~ 1 / s ² changes in the parameters W ₁ zx, W ₂ zy, S ₁ and S ₂ to assess the development or attenuation of the geodynamic zones of the RF.

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