SU1520462A1 - Method of seismic logging - Google Patents

Abstract

The invention relates to geophysical exploration methods and can be used in the exploration of oil, gas and other minerals to measure the velocity of seismic waves in rocks. The purpose of the invention is to improve the accuracy and detail of determining the speed of propagation of seismic waves. The seismic logging method involves exciting a seismic wave, registering it at three or more points at a distance ΔZ from each other shorter than the wavelength, and calculating the velocity of propagation of the seismic wave from the derived wave field from the time and coordinate of the receiving point.

Description

The invention relates to geophysical exploration methods and can be used in the exploration of oil, gas and other minerals to measure the velocity of seismic waves in rocks.

The purpose of the invention is to improve the accuracy and detail of determining the propagation speeds of seismic waves.

The method is carried out as follows.

On the surface of the well excite a seismic wave. Seismic receivers are located in the well at depths Z ,, z, ЕЗ with a step

utv uz 6--,

where it is the sampling step of the seismic station;

V is the average prior value of the speed at the work site; f is the dominant oscillation frequency,

n is the number of samples per period required to describe the signal. The data obtained is subjected to an ovacidal treatment to determine the speed. To do this, calculate the derivatives

- | rfl-- u (z,, t) t-u (zj, t) -2u (z2, t);

Vu (

9t

., t-i-2 & t + u (zj, t) -2u (zg,),

where .i {, z, t) is a floor}) new field;

t - sampling step at

records, for example, 0.001 s. To perform the calculations, the time t is determined using the formula

15204624

Derivative 3u / 9z. determined by reading

Hey 1

5 3z 2

by

Hey 1

5 3z 2

t ,. t; ,

- magnetic recording time

tape;

- time delay formed by multiplexing during recording by digital seismic stations

,)

20

where T,, T2 - initial and final registration m direct

Claims (1)

the waves. Formula invented where & t is the sampling step, N - the number of registering seismic channels; i is the death of the channel on which A recording is made of the seismic attached to it. 25 Method of seismic logging, receiver. The basis for determining the speed is the differential ratio including the excitation of seismic waves, their registration in three and large points, which is different, in order to increase the accuracy and accuracy of determining the propagation speeds of seismic waves, the receiving points are placed in the well at a distance (z, t J (zjtt) n d z V 9 t right at any point in space at any time. The seismic velocity is calculated by the formula one ) . l 9zla t yp iiirpi; about where T is the time interval of registration of the wave field; Z - spatial coordinate (depth), t is the time coordinate, u (z, t) is the wave field. The result of determining the scraper refers to the point where the middle seismic receiver is located. Another treatment option is possible in which only the first arrivals of the direct wave are used on a time interval equal to the wave period. In this case, use the ratio iyiSiil 1 9 Z V Oe 1 uCz.t + ut) - u (z ,, t). Velocity V is determined using the formula t. V tG 1 iu () 9.U 13t z Miiin -; - ii- .. j where T,, T2 is the initial and final registration time direct the waves. Invention Formula Seismic logging method including the excitation of seismic waves, their registration at three or more points, characterized in that, in order to increase the accuracy and detail of determining the speed of propagation of seismic waves, the receiving points are located in the well at a distance  - | -, where bt is the sampling step of the seismic station during recording, V is the average prior value of the speed in the work area} n is the number of samples per period of oscillation necessary to describe the signal, f is the dominant frequency, and the speed of propagation of seismic waves is determined by the formula one . afyiz tl dt i one nSilil dt J time interval of registration of the wave field of the spatial coordinate depths; time coordinate; wave field.