A Time-difference Correction Method for Variable Offset vsp Data

Abstract

The invention provides a variable-offset VSP data time difference correction method and belongs to the field of earthquake data processing. The method includes the following steps: (1) decompiling acquired original variable-offset VSP data so that three-component wave field data is obtained; (2) inputting a shallow replacement speed V<replacement> and an earthquake processing base level elevation Z<base level>, which are used in processing of ground earthquake data of an area which a VSP observation well is in; (3) picking up first-arrival times of direct waves on vertical components z of offsets so that time-depth data T<0> (n, L<K>) is obtained; (4) calculating a time difference in a single offset; (5) calculating inter-offset time differences; (6) correcting a total time difference; (7) analyzing correction error; (8)ending. The method improves the original wave field quality of the variable-offset VSP data and provides accurate basic data for further effective application of the variable-offset VSP data.

Description

Technical field [0001] The invention belongs to the field of seismic data processing, and specifically relates to a time difference correction method for variable offset VSP data. Background technique [0002] The actual non-zero offset VSP observation is limited by the number of receiver geophone stages in the well. VSP observation requires multiple lifting of the geophone and group shot excitation to complete the entire well section observation. Multiple (variable) offset VSP data are obtained by the method of explosive source and multiple well group shots. The wavefield time difference correction mainly involves two aspects: ①Within a single offset: due to group shots excited well depth, excited lithology, excitation Influenced by factors such as the height of the well and the offset of the excitation well, there is a time difference between the depth points of the received wave field; ② Between different offsets: with the change of the offset, the surface excitation elevation...

AI Technical Summary

Problems solved by technology

Due to many geological and non-geological factors, no time difference correction or insufficient time difference correction accuracy for variable offset VSP data will distort the original wave field information to varying degrees, which will affect the subsequent variable offset VSP wave field. The effective use of information such as reflected waves and converted waves affects the reliability of identifying structural details around the wellbore and reservoir problems

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