SU940114A1 - Method of detecting local geological objects - Google Patents

Description

(54) METHOD OF SEARCHING FOR LOCAL GEOLOGICAL OBJECTS

Claims (2)

The invention relates to geophysical methods, in particular, to the search for as yet pny objects in the earth's crust, which differ from the surrounding rocks in thermal properties. There is a known method of searching for local objects based on measuring the temperature in a well at a depth that guarantees the absence of interference with daily and seasonal changes in the temperature of the earth's surface. The measurements are carried out some time after the drilling is carried out upon reaching thermal equilibrium between the well and the surrounding rocks. The studies are carried out with a temperature sensor such as a thermistor or flj thermocouple. The disadvantage of this method is the need to deepen the temperature fluctuations below the zone, which leads to the production of large volumes of drilling operations. The closest to the proposed technical essence and the achieved result is the method of searching local geological objects, based on the study of the thermal floor of rocks in the studied area. In this method, two temperature-sensitive sensors are placed in shallow wells vertically for a given distance l. From the temperature difference, the heat flux wise is judged / 2j. The disadvantage of this method is that the strong influence of temperature interference on the conductive measurements involves. The temperature difference at the points of ymeren (thermal flux) near the surface depends on the variation of solar radiation, weather conditions and the changes in the near-surface mode caused by it, which does not allow uniquely interpret the results. The goal of gaining money is to simplify the method and increase its accuracy. The goal is achieved by the fact that in the method of searching for local geological objects, based on the study of the thermal floor of rocks in the 394 follow-up area, observation points are measured. During a fixed period of time, the amount of heat generated by rocks and availability and locations of local objects. The method is implemented as follows,. At the observation points, measurements are simultaneously carried out of the amount of heat CQ / I) emitted by rocks for long periods of time approximately equal to each other for each observation point, then corrected for the deviation of the observation time and at 1 point. From the average t XB | 1i by multiplying by the dimensionless factor K - € I-1, and plotting the contour maps, Others exceed the value of the parameter Q over a certain background value OCP. The method is based on the weakening of the short-term and periodic component of the interference due to the long-term nature of the accumulation of the useful signal when measuring this thermal field parameter. FIG. Figure 1 shows the temperature change (K) of the heat flux (() And the amount of heat (dR) in response to one and the other: and the destabilizing factors depending on the time, where -fe / 1 is 12.- time interval of exposure; t is the current reference times l d The values of k, φ, and D Q in the time dimension are distorted by the action of thermal interference with a period T. If the values of temperature K and heat flux are distorted by interference with amplitude not depending on the reference time, then the magnitude of the amount of heat & Q is distorted by interference, the smaller the larger. elapsed from the moment of accumulation of Q Q compared with the period of pmeme T due to the accumulation of a constant useful signal and mutual compensation of the variable component of the noise. In the proposed method, the time of accumulation of signal scaling is chosen longer than the interference period. arising, for example, due to the infiltration of precipitation, acting at time t-. If the anachvi) H Wsv) can significantly 44 but deviate about the mean values of K and (Fig. 1 a and b), then the value of AQ (-ly less deviates from the true value of e (} (t ,; which, at any moment time i is equal to uQ atft, where a (cC is the angle of inclination of the straight line, shown in Fig. 1-p), if the start time of accumulation & Q is the counting time tj combined from the beginning of the coordinates. This is due to the short duration large amplitude thermal disturbance, caused, for example, by infiltration of atmospheric precipitation. Example: A site of work is selected in a flat terrain in medium shea During the measurement, the average temperature over the area under study at a depth of 0.75 m is 3 C. The site under study has an ore body of an isometric formj i, covered by an 80-meter thick shale layer (thermal conductivity coefficient 5, -7 Profile section, crossing the ore body. With a graph of increments of L O is shown “and Fig. 2. A map of the isolines L Q -C, the projections of the ore body on the day surface (shaded area) is shown in FIG. 2. The cross-section of the isolines — after 25 J. Dp. Of measuring the amount of heat released by rocks at the point of measurement over a long period of time, an isothermal calorimeter with thermal insulation based on foam is used. The calorimeter constant K is 6.2810 with the mass of the working fluid in 1OO g, which provides a signal accumulation time of 1.5.10 s. Consider the course of measurements using the example of pickets 32 and 36. A calorimeter with an ice mass of 100.075 g is installed on a picket (PC) 36 at a depth of 0.75 m, and on a PC of 32 - 100.032 g. The installation and removal of instruments is fixed with an error of 30 s and is −2,249510 s, 1.2465-105-s. The average observation time b i ,. Amendments K- | ifti is Kjfe 1, LLC56O2,, 1 (52 1.002968. The mass of melted ice (determined with an error O, O01 g) is W, 65.2OO t, 131 g. Amount of heat absorbed by the devices, taking into account; 1 multipliers 141 constants & 1 b, b 895 “10 J, 1, J. Background heat value R cf set over the area distribution of the parameter selected by 1 avny 1, O7 – B1 b J. Then AQ-5fe 195 J, .42 J. but operations are carried out on other pickets. Based on the obtained uQ values, graphICOB maps and isolines & p maps are constructed. As can be seen in Fig. 3, the аль 1fangled zones, in connection with a local geological object contrasting in the thermal field of the Earth, since QI, in the case of an isothermal calorimeter, is determined with rio to the formula Q 1,671О tv j where t is the average residence time of the isothermal calorimeter in contact with rocks, with; ti is the time it was in the station, s; the mass of melted ice, g, the ashsturih-methodical error of determining QI for this example is dQi si, 67.10H (4a Qi. (3-t is the corresponding errors. In our case, dQ is 2.8 J. So, the useful signal of 15O j can be characterized by 8-17 isolines, conducted through the CS or even 6 G, which fully satisfies the errors 4 shows the contour map of the KK temperature increments for the same section (cross-section of the isolines through 9 and 146.) Due to the high level of the lamek, the field K is more rugged than the field before. Anomalies field K over ore bodies, marked shaded on the map, splits into two .. In the absence of interference, it should be observed its localized anomalies with a maximum of about. In the DK field, several more weakly anomalous areas appear that are associated with distortions of the perforation field psjsehami - As a result, the position of the ore body is fixed uncertainly. Formula of an active breach A method of searching for local geological objects, based on a study of the thermal floor of rocks in the survey area, characterized in that, in order to simplify and improve accuracy, at the points of observation The days of the day measure the amount of heat emitted; rocks, and on the resulting judged on the presence and location of local objects. Sources of information taken into account in the examination 1. US Patent No. 24О37О4, cl. 73-432, 1946. 2. US patent number 3714832, cl. 73-432, 1973 (prototype). but ii B tix Uiz / V Tz | 4, Lg