Geo-electrical prospecting method

FIELD: physics; measurements.

SUBSTANCE: present invention pertains to electrical prospecting using an electrical resistance technique. The invention can be used chiefly, for detecting tectonically crushed, water permeable rocks, detection of ore-bearing objects, covered by loose formations, studying the spread of industrially contaminated underground water in the geological environment etc. One supply ground connection is put at infinity. In a well, several supply ground connections are arranged at a given distance from each other. These connections are successively connected to a current source. For each connection, the potential drop between receiving ground connections are measured using a measurement grid. The apparent electrical resistance values are determined from the potential drop values. Isolines for electrical resistance for all depths where the supply ground connections are drawn up. Presence and position of geoelectric irregularities is determined from the layout of the isolines. Within the boundaries of the detected irregular regions, one of the receiving ground connections is moved around the other. The potential drop between them is measured. In the direction of the receiving line, at maximum voltage value, the spread of linear-stretched irregularities or the position of local objects with increased electroconductivity can be determined.

EFFECT: increased efficiency of detecting irregularities in the geological environment.

2 cl, 2 dwg

 

The present invention relates to an electrical exploration method of electrical resistivity and improves the efficiency study of the upper part of the geological section, identify local variations in the bedrock.

The field of application of the proposed method: identification of tectonically fragmented, permeable rocks; the discovery of ore-bearing objects, covered with unconsolidated entities; the study of the distribution in the geological environment of human-contaminated groundwater and other

A known method of charge intended for exploration of ore deposits, in which one supply grounding refers to practical infinity, the other is placed in the ore of undercutting opened by the well, and on the earth surface system profiles traced the lines of equal potential, or studied the potential distribution or gradient. According to the plan configuration of the lines of equal values, or by changing the profile of the values of the potential and its gradient is judged on the distribution of the surveyed area of the ore-bearing zone [1].

The known method has significant drawbacks: first, the results depend on changes in the power and electrical resistivity overlying unconsolidated formations, secondly, experimental graphics capabilities and the and its gradient are compared with theoretical designed for homogeneous environments, although the geological environment is heterogeneous in both the horizontal and vertical direction [2].

There is a method of small-scale charge intended for examination of large ore fields and selection within individual ore objects. As in the method of the charge, one supply grounding refers to practical infinity, and the second is arranged in the ore undercutting opened by the well. Because the tablets using the method of small-scale charge are of considerable size, with two receiving grounding system profiles measured the distribution of electrical potential less potential gradient [2].

The known method has significant drawbacks: first, when measuring the electric potential is necessary to use a long measuring lines that in areas with a high level of noise makes it difficult works, secondly, the interpretation of the experimental data is extremely complex and subjective, as it requires a great amount of geological and geophysical information.

The closest in technical essence to the present invention is a method of submerged electrodes, in which one supply grounding refer to practical infinity, another place well even in the absence of the ore undercutting, and the and the surface of the earth, using two receiving ground system profiles study the distribution of the gradient of electric potential.

Prototype method has significant drawbacks: the distorting influence of inhomogeneous both in capacity and electric resistance of a coating of loose formations; the influence of vertical contacts of rocks [2].

The aim of the proposed method is to increase the efficiency of detection tectonically fragmented, permeable rocks; the discovery of ore-bearing objects, covered with unconsolidated entities; the study of the distribution in the geological environment of human-contaminated groundwater.

This goal is achieved by the fact that in the proposed geoelectroprospecting that uses the first power supply ground reserved in practical infinity and connected to one of terminals of the electric current, and the second feeding ground, placed in the borehole and connected to the other terminal of the source of electric current, and two foster grounding, connected to the measuring device for measuring on the surface of the electrostatic voltage between the profile system, which consists in the fact that it uses several feeding ground, placed in the borehole at a given distance from each other, are alternately connected to terminal East is cnica electric current, and each time you connect the downhole power supply grounding measure the voltage drop between the receiving ground along profile observations, determine the values of the apparent electrical resistance and the distribution of the apparent resistivity on the area of observations and the incisions are judged on the presence and position of the geoelectric inhomogeneities. Within the identified anomalous areas one of the receiving ground move circumferentially relative to the second receiving ground at a given angle up until the absolute value of the measured voltage reaches the maximum value, and in the direction of the suction line in the area of maximum measured voltage is judged on the stretch of the geoelectric inhomogeneities.

Figure 1-2 shows the schematic of the proposed installations. The first supply earthing (included in the practical infinity. Figure 1 is a feeding ground A1-Anplaced at a given distance from each other in the borehole; M and N foster grounding; ΔUMN1- drop voltage, measured along the profile of observations; 1 - switch unit supply grounding; 2 - source of electrical current; 3 - measuring device. The arrows in figure 2 is shown moving along the circle foster SATELLINE the N 2-Ni; ΔUMniposition the suction line when the maximum absolute value of the measured voltage drop.

The proposed method is carried out with commercially manufactured equipment ERA, ERA-MARK as follows. In the presence of the surveyed area of the earth surface of the well, not even uncovered ore undercutting, placing in the borehole a series of supply grounding (A1-An), located at a specified distance (depth) from each other and connected to the switching unit, which connects each of the supply ground to one terminal of a source of electric current. Another feeding ground (In) refer to practical infinity, i.e. at such a distance, to conform to the condition: AB 10-15 times larger than the distance between the receiver ground. Supply grounding is connected to the other terminal of the source of electric current. Receiving the grounding of M and N is attached to a measuring device. When connecting the terminals of a source of electric current to the supply grounding A1measure the drop in voltage ΔUMN(A1). Then to the terminal of the electrical power source is connected to ground And2And3...Andnand measure the voltage drop ΔUMN(A2)...ΔUsub> MN(An). After performing the above measurements foster grounding moved along the profile with a step equal to MN and all operations will be repeated. According to the obtained results are the values of the apparent electrical resistance ρto(A1)...ρto(An) by the well-known expression ρto=to·|ΔUMN|/I. Here is a geometric factor setup; |ΔUMN| is the absolute value of the voltage between the receiving ground; I is the current flowing from the supply ground.

Performing such measurements in the survey area, make plans contours of apparent electrical resistance for different depths, the relevant provisions of the supply grounding A1...An. Each heterogeneity, which has a higher electrical conductivity compared to the host rocks, will be noted on these plans by the region of low values of apparent electrical resistance of the geological environment.

When performing research on individual profiles, given the different depth of placement of supply grounding A1...Anbuild the distribution of apparent electrical resistance of rocks in the context of and judge the position of heterogeneity depending on the depth.

On the anomalous areas identified as at areal studies and works on the nutrient profiles, one of the receiving ground, located along the observation profile, move on a circle whose center is the second power supply ground, and the radius is equal to MN. Moving exercise at a given angle in one direction (figure 2). At each position of the movable receiving ground measure the drop in voltage. The rolling movement of the receiving ground to produce the maximum absolute value of the voltage drop. Obtained in this case, the direction of the line MN indicates the position of the geoelectric inhomogeneities. For example, if the presence in the geological cross section linearly elongated heterogeneity with, compared with the host environment increased conductivity, the direction of the selection line MN, which is fixed to the maximum value of the electrostatic voltage between foster grounding corresponds to the strike zone of increased conductivity and receiver lines obtained at different observation points, will indicate the position of heterogeneity in the geological environment.

Thus, the advantage of the proposed method is to increase the efficiency of detection of inhomogeneities as the upper part of the section, and in the bedrock in various geological conditions, discovery of ore-bearing zones and local is bjectiv, so as an end result of research based on obtaining views on the major parameters of the geological environment - its electrical characteristics.

1. Geoelectroprospecting that uses the first power supply ground reserved in practical infinity, is connected to one terminal of a source of electric current, and the second feeding ground, placed in the borehole and connected to the other terminal of the source of electric current, and two foster grounding, connected to the measuring device for measuring on the surface of the electrostatic voltage between the profile system, characterized in that it uses multiple feeding ground, placed in the borehole at a given distance from each other, are alternately connected to the terminal of the source of electric current, and at each connection borehole supply grounding measure the drop in voltage between the receiving ground along profile observations, determine the values of the apparent electrical resistance, and the distribution of the apparent resistivity on the area of observation and the incisions are judged on the presence and position of the geoelectric inhomogeneities.

2. The method according to claim 1, characterized in that it is one of the receiving ground move in the environment and the activity related to the second receiving ground at a given angle until while the absolute value of the measured voltage reaches the maximum value, and in the direction of the suction line in the area of maximum measured voltage clarify the position of the geoelectric inhomogeneities.



 

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