Method for calculating velocity ratio of longitudinal wave to transverse wave by using non-zero wellhead distance data

Abstract

The invention belongs to a petroleum exploration data processing technology, and in particular relates to a method for calculating a velocity ratio of a longitudinal wave to a transverse wave by using non-zero wellhead distance data. The method comprises the following steps of: acquiring a three-component earthquake record subjected to static correction, performing first arrival pickup, synthesis and reverse convolution, sequentially arranging coordinate parameters of pickup points obtained from an in-phase shaft of up converted waves from shallow to deep, and calculating the velocity ratio of the longitudinal wave to the transverse wave between adjacent shot points and between detection points by acquiring the time when the in-phase shaft is reflected by a wave field of the up converted waves. By the method, the velocity ratio of the longitudinal wave to the transverse wave is calculated by directly using the up PSv wave pickup time of a non-zero wellhead distance without a transverse wave hypocenter; almost all the VSP data of the three-component non-zero wellhead distance are provided with up converted waves and can be obtained more easily than down converted waves; the velocity ratio of the longitudinal wave to the transverse wave has a low requirement on the precision of the time parameters of the up converted waves; and therefore, the method is easy to implement.

Description

technical field [0001] The invention belongs to the field of petroleum seismic exploration, and uses the vertical seismic profile method (VSP) non-zero well-source spacing data to calculate the velocity ratio of longitudinal and shear waves. Background technique [0002] The VSP data collected in the field needs to use the P-to-S wave velocity ratio in the non-zero well-to-source converted wave imaging processing. At present, there are three main methods for calculating the P-to-S wave velocity ratio by VSP. One is based on the VSP field data: using the VSP zero-well source The P-wave layer velocity is calculated from the first arrival time of the P-wave (P) wave data, and then the shear-wave layer velocity is calculated by using the first-arrival time of the pure shear wave data with zero well-source spacing, and the ratio of the P-wave and S-wave velocity is obtained by comparing the two. The disadvantage of this method is that it needs to use a pure shear wave source, whi...

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Problems solved by technology

[0006] c) Regardless of the strength of the reflected wave, for the horizon to be calculated, the first arrival time of the upconverted wave must be picked up, but it is difficult to pick up the first arrival time of the weak upconverted wave accurately

[0007] d) The equivalent velocity span is large, and the calculation method itself is not designed precisely enough

[0008] At present, there is no method that can accurately and completely solve the problem of the P-to-S wave velocity ratio used in converted-wave imaging of VSP non-zero well-to-source spacing, and it is basically a rough estimate

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