RU1787275C - Method for seismic prospecting - Google Patents

Abstract

Usage: seismic exploration for the study of complex environments. SUMMARY OF THE INVENTION: As a result of fieldwork using a multiple profiling system, a velocity-angular analysis of seismograms is performed. Time sections are obtained with fixed angles of approach of the waves and the corresponding directivity characteristics used to select the optimal system of work.

Description

The invention relates to methods for seismic exploration of reflected waves and can be used to study complex media.

The reliability of the results of seismic exploration depends on the method of obtaining time sections. There is a method based on a single profiling technique. The disadvantage of this method is the low quality of cuts due to a large number of various kinds of interference.

The closest in technical essence to the invention is a seismic exploration method, including fieldwork using a multiple profiling system and processing of the obtained data for structural constructions using the common depth point method. In this case, the parameters of the observation system are selected based on considerations

maximum suppression of multiple waves.

In seismic surveys in ore regions, steeply dipping reflecting granites prevail and, therefore, steep-feeding in-phase axes should be present in seismic time sections. However, the CDP method has a limited scope, since at tilt angles of more than 12-15 °, seismic information is distorted due to the ambiguity of the image of complexly constructed media. In addition, the wave field in seismic time sections is difficult to interpret due to the destructive interference of a significant number of differently inclined in-phase axes. The choice of the parameters of the observation system under these conditions in a standard way is impossible due to the inappropriateness of approximating the medium by a plane-parallel model.

X | 00

VI th XI ate

with

The purpose of the invention is to expand the scope and increase the reliability of seismic data.

The goal is achieved by the following sequence of operations: excitation and registration by the interference system of seismic signals through a multiple profiling system and processing of the obtained data. In order to increase the efficiency of seismic exploration in complex structures based on seismograms obtained as a result of preliminary work, velocity-angle spectra are constructed from the relationship

2

Sin p) 2 + -J COS p - t,

V

where t is the time delay for the hodograph of the reflected wave;

t is the double travel time of the wave according to the norms to the reflecting boundary;

I - removal of the explosion device;

V is the effective velocity to the boundary, the main seismic waves with parameters {Vi, p} are identified from the spectra, where I is the current wave number, and subsequent seismic work is carried out on the profile for the selected parameters of the seismic waves by an interference recording system with an optimal directivity characteristic, the parameters of which are determined from the ratio. .

. n (V. V) ft / (2 slnTJTf Dg) 2 + (5) cos 2 l f Dg) 2,

de N - directional characteristic;

mp is the current angle;

N is the multiplicity of the interference system (the number of channels in the seismogram);

f is the reference signal frequency; Dg g () -t () is the delay between two hodographs for angles p and

 V

Practical testing of the proposed method showed that, in comparison with the OGT method, there are the following advantages; the field of application has been expanded and the reliability of the results of seismic exploration has been increased due to the dissection of the complex interference pattern in time sections; increased signal to noise ratio; parameter optimization possible

observation systems in the framework of multiple overlap techniques.

In addition, increasing the reliability of the results of seismic exploration allows to reduce the costs of exploration and search for mineral deposits due to a more specific location.

Claims (1)

- The claims A seismic reconnaissance method, including excitation and recording of seismic signals by the interference system using a multiple profiling system and processing the obtained data, characterized in that, in order to increase the efficiency of seismic exploration in complex environments, seismic data obtained as a result preliminary work on the site profile studies; they construct the velocity-angle spectra from the relation 25 .------, ------- I . | (t- sinpf + -Lcos2p-t v where C is the time delay for the telegraph of the reflected wave; t is the double travel time of the wave normal to the reflecting boundary; I - removal of the explosion device; V - effective speed to the border; p is the angle of inclination of the boundary, the main seismic waves with parameters {Vu p}, where i is the current wave number, are selected from the spectra, and subsequent seismic work is carried out on the profile for the selected parameters of seismic waves by an interference recording system with an optimal directivity characteristic, the parameters of which are determined from the relation 45 H (R. V) Xsln 2 L R) 2 + (Ј cos d7) Γ where H is the directivity characteristic; booths and corner; N-fold interference this-: topics The number of channels in a seismogram); f is the reference signal frequency; , Dg g (y) -t () is the delay between two hodographs for angles 1.