An Absorption Method for Detecting Oil and Gas in Formation

Abstract

The invention provides an absorption method used for detecting an oil-gas possibility of a stratum and belongs to the seismic data reservoir prediction field in oil and gas field exploration and development. The method comprises the following steps: firstly, using a generalized S to convert and obtain a time-frequency spectrum of each seismic record in seismic data; then according to the time-frequency spectrum, calculating an instantaneous amplitude of each time point in different frequencies on the each seismic record; and then using the instantaneous amplitude to obtain an absorption coefficient corresponding to the each time point, wherein the absorption coefficients corresponding to all the seismic records form one absorption coefficient body; finally, using the absorption coefficient body to detect an oil-gas-bearing character of the stratum. According to the method of the invention, the generalized S with high precision is used to convert and obtain an instantaneous amplitude spectrum on the each time point in a seismic signal so that inconsistency of a wavelet transformation scale and the frequency is avoided; a attenuation maximum peak gradient method is used to calculate the absorption coefficient, which can accurately describe the oil-gas-bearing character of the stratum.

Description

technical field [0001] The invention belongs to the field of seismic data reservoir prediction in the exploration and development of oil and gas fields, and in particular relates to an absorption method for detecting the oil-gas content of formations. Background technique [0002] Time-frequency analysis is a traditional method for analyzing non-stationary signals. It can transform a one-dimensional time-domain or frequency-domain signal into a two-dimensional time-frequency plane, obtain the time-frequency spectrum of the signal, and extract and distinguish signal components in the time-frequency domain. , to understand the characteristics of the signal more clearly. The traditional Fourier transform only decomposes the signal on a single frequency, and its frequency resolution can be arbitrarily good, but it loses the time resolution. The length of the original function and kernel function of the Fourier transform is the entire interval, which is essentially a global tran...

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Problems solved by technology

This attenuation total energy gradient method is also called the attenuation gradient method, and it also has certain problems: when the formation contains oil and gas, the energy in the low-frequency part will increase, and the energy in the high-frequency part will decrease, so the main frequency will be close to the high frequency end

When the oil and gas features are very obvious, the energy at the high frequency end is less, and the frequency when the total energy calculated by the attenuation gradient method reaches 65% is likely to be at the low frequency end of the main frequency, and the calculated gradient at this time will be greater than the oil and gas features. If the gradient is so obvious, the absorption coefficient at this time cannot accurately reflect the oil and gas characteristics of the formation.

In addition, both the spectral ratio method and the attenuated total energy gradient method involve the setting of low cut-off frequency and high cut-off frequency. Improper parameter setting will affect the calculated absorption coefficient, so its application is also limited.

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