RU97101683A - METHOD FOR HIGH RESOLUTION SEISMIC EXPLORATION METHOD BY GENERAL DEPTH POINT METHOD USING CHARGE EXPLOSION - Google Patents

Claims (5)

1. The method of high-resolution seismic exploration by the common depth point method (MOGT) using a blast of charges, which consists in the fact that before the start of profile observations in the study area, the geological and geophysical data determine the conditions of occurrence of rocks in the zone and below the low-velocity zone (ZMS) carry out preliminary seismic surveys to select the optimal conditions for the excitation and reception of seismic vibrations and, under selected conditions, conduct the main seismic surveys of the MOGT, characterized in that at the stage of preliminary seismic exploration, the minimum charge mass with a high detonation velocity is determined, which ensures the formation of an informational seismic signal with the minimum possible useful wavelength and with an intensity sufficient to isolate useful waves against irregular interference waves by detonating single wells in wells charges with increasing TNT equivalent from 1 g to 1000 g at the initial depth under the ZMS, equal to 1 / 8-1 / 4 of the prevailing value of the apparent useful wavelength, register of the seismic signal by positioning the seismic receivers and / or accelerometers and analyzing the obtained seismograms, after which the depth of the charge is lower than the ZMS, which ensures the stability of the shape of the informational seismic signal with the smallest possible useful wavelength, and isolating it against the background of irregular interference waves by pre-charging the charge of the selected mass at distances of 0.5 - 3.0 m from the initial depth of immersion of the charge in at least one well with subsequent registration of the positional race the installation of seismic receivers and / or accelerometers of the information seismic signal and its analysis, while during the main seismic surveys, the maximum distance of the blasting device X _{max is} chosen from the ratio

,
where Z is the depth to the target reflecting horizon,
N = f ^vrc / f ^csc - coefficient of increase in the prevailing frequency of the information seismic signal,
f ^arp - the prevailing frequency for high-resolution seismic exploration,
f ^csc - the predominant frequency in the mid-frequency seismic survey,
the distance between the centers of the groups of geophones, which should not exceed the Nyquist wave number, is chosen from the relation
ΔX ≤ λ _min / 2 ≤ π / κ,
where κ is the Nyquist wave number,

minimum wavelength of the information seismic signal,
ΔX is the distance between the centers of the groups of geophones,
recording a registered seismic signal at seismic stations is carried out with a quantization step Δt selected from the relation
Δt ≤ 1 / f _max ,
where f _max is the maximum width of the spectrum of the useful wave.  2. The method according to p. 1, characterized in that when selecting the minimum charge mass, from 1 to 20 detonators are used as single charges.  3. The method according to p. 1, characterized in that when selecting the minimum charge mass, single explosive charges weighing from 20 to 1000 g are undermined 4. The method according to p. 1, characterized in that when specifying the depth of immersion of the charge control the shape of the direct wave according to the recording of a single geophone, immersed in a neighboring well with a blast hole to a depth determined from the condition,
Δh ≥ h _sms + λ,
where h _zms is the power of the ZMS;
λ is the predominant value of the apparent useful wavelength.  5. The method according to p. 1, characterized in that they use single charges with a detonation speed of more than 5.5 km / s.