SU1543357A1 - Method of spatial seismic prospecting according to multiple overlap method - Google Patents

Abstract

This invention relates to seismic exploration methods for mineral deposits. The purpose of the invention is to improve the performance of area seismic surveys. For each position of the receiving unit and a series of P excitation points, a sequence of P random numbers is generated. They are bounded to the left by the correlation radius of seismograms received from different points of excitation, and to the right by half the duration of one seismogram. These random numbers are used as trigger delays for sources located at P excitation points, and the oscillation from all these sources is recorded continuously. The trigger times of the sources are remembered and used to separate the wave fields when processing the results. When summing by the method of multiple overlaps, the results from one excitation source are summed in phase, and from different sources - out of phase, since the delays in starting the sources are random and independent. 2 Il.

Description

The invention relates to spatial seismic exploration of minerals.

The aim of the invention is to increase the productivity of work.

Figure 1 and 2 shows the scheme of implementation of the method.

Figure 1 shows the profiles 1 and 2, in which points 3.1 3 "P excitation, the profiles k and 5 of the recording of seismic vibrations, near which there are seismic stations 6 and 7 and

on which points 8.1 and 8.N are located for receiving seismic vibrations at a distance thereof. from each other. Recording profiles are located at a FRIEND distance from each other (/ is the length of the recorded seismic wave). The values of dx and lu are of the same order as the value of /. Clauses 8.1 - 8.N of the reception of each registration profile are connected to seismic stations 6 and 7. A receiving installation made up of several receiving points may occupy different positions 9 and 10 (for example) on the excitation profile 5.

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The receiver is installed at position 9 and the sources at the points of excitation on profile 1 form one position of the observation system, the receivers at position 10 and the sources on profile 2 form another position, etc. in accordance with the technique of multiple overlaps.

The device for implementing the method (FIG. 2) includes seismic stations 6 and 7, one of which (seismic station 7) is leading. Seismic station 7 is connected to the generator 11 of the pulse sequence starting sources 12.1 - 12.P excitation oscillations. The generator 11 has a random number sensor, such as a noise generator, based on the phenomenon of radioactive decay, on a gas discharge in a thyratron, etc.

The generator 11 is connected to a distributor 13, which is a conventional electronic switch consisting, for example, of a five-bit binary counter and a set of keys for unipolar voltage with the outputs. The five bits of the counter knowingly overlap the possible P values in practice. A constant voltage source is connected to the inputs of all the keys, and the starting drivers of the 12.1–12.P sources are connected to their outputs.

Shaper 1 of the source trigger signals is a differentiating amplifier with a sufficiently powerful, for example, thyristor output, the current of which is sufficient to undermine the electric detonator or to start a non-explosive source.

The connection of sources to the outputs of the formers 1 can be made in a random, but known order, i.e. the source numbers on profile 1 and the number of the output of the former to which they are connected may differ from each other randomly.

The master seismic station 7 is connected to the formation of the trigger points of all sources.

The method is carried out as follows.

Observations are carried out according to the multiple border tracking method, i.e. record seismograms for each position of the observation system. On command from the seismic station 7 in not

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which moment the work begins at this position of the observation system and the generator 11 is started.

For each position of the observation system, a generator 11 generates a sequence of random numbers equally distributed in the interval & t cor-T / 2, where At c0r is the correlation interval of the seismograms from different excitation points; T is the length of a seismogram record from one source. These random numbers are the dT3 start up delays of the sources. The ut3 delay is the time interval after which the excitation source is turned on, relative to a certain instant of the start of observations at a given position of the observation system. By delays At s, the generator generates P time delays for the RT (starting sources relative to each other:, - -tif, where fltj.i-M and fit h; are the adjacent values ut $. DT are already distributed according to Poisson's law.

Delay dT; from the generator 11 is fed to the distributor 13 and further to the drivers of the trigger signals of the sources. Each source receives one trigger pulse and starts this source. The response times of all sources (usually from receivers installed directly near the sources or onto them, or from the schemes of the moment of explosion) are transmitted to station 7 and stored there on the simultaneously recorded seismograms. The oscillation is recorded from all P sources 12 continuously since the start of observations at a given position of the observation system having P excitation points. P start-up pulses with delays / 9t3 are sent to the excitation sources in the time interval at akr i Ј CD.ЈT / 2. After the last time source is triggered, the registration time is still Tc, so that the total registration time is no more than 1.5 Tc. In this case, the wave fields of all P sources overlap in time and exist in the medium simultaneously. Due to this, a complex incoherent total field of duration RT is created in the medium, where k is the coefficient taking into account the record lengthening due to delays (, 5).

As a result, one complex gather is obtained for the first position of the sources and the receiving system. After that, the receiving system and the sources are shifted along profiles 4 and 5 by one step to the next position and the whole process of exciting and recording oscillations is repeated, etc.

Due to the incoherence of the summation of the wave fields, it is possible to separate the wave fields from different sources when processing data using the GBS method and building seismic images by the diffraction method. This is achieved when reproducing compressed recordings by introducing time delays equal in magnitude and opposite in sign to the delays applied and remembered when registering oscillations.

The generation of various realizations of random numbers (and time delays) for different positions of the excitation profiles of the oscillations (sources) provides an incoherent summation of the wave fields of adjacent receiving profiles of compressed seismograms of multiple boundary tracing and thus creates the possibility of separating all sources placed on the emitted area. If this is not observed, interference from sources located on other excitation profiles will be observed.

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Claims (1)

Invention Formula The method of spatial seismic exploration by the method of multiple overlaps, including placing points for receiving seismic vibrations on one or several parallel profiles x and points of excitation located on transverse profiles x on P points on each of them, launching sources, registering seismic vibrations sequentially in time from each point excitation and processing of seismograms, characterized in that, in order to improve the performance of work, they form a sequence of signals corresponding to tea numbers distributed independently and equally on a segment limited to the left by the correlation interval of the seismograms from different excitation points, and to the right by half the duration of the seismogram from one excitation point, start sources using groups of P sequence signals as source delays in P excitation points on each of the profiles, with registration of oscillations from all P points of each excitation profile being performed continuously, and the starting moments of the sources; memorized and used in processing. 8.1 .g T A A A A A L / Jx A a l 8.N l s s ten l figure 1 at L L A A A L L L L AAAAAAAAA L (rig 2