A method and device for identifying gas layers using longitudinal waves and Stoneley waves

Abstract

The invention discloses a method and device for recognizing a gas layer by using a longitudinal wave and a stoneley wave. The method comprises the steps of S1: acquiring a longitudinal wave waveform and a stoneley wave waveform after wave filtering, a head wave arrival time curve of the longitudinal wave, and a head wave arrival time curve of the stoneley wave; S2: respectively conducting Fouriertransformation to the longitudinal wave and the stoneley wave; S3: acquiring amplitudes in a preset time window length of the longitudinal wave and the stoneley wave; S4: transforming the amplitude ofthe longitudinal wave into a longitudinal wave energy, and transforming the amplitude of the stoneley wave into a stoneley wave energy; S5: acquiring a recognition curve of the gas layer according tothe longitudinal wave energy and the stoneley wave energy. According to the method, by using the longitudinal wave energy of an array acoustic wave and the stoneley wave energy, an indicative curve of stratum gas content is calculated, response characteristics of natural gas to the longitudinal wave attenuation and the stoneley wave attenuation are amplified, the influence of only the longitudinal wave attenuation response or the stoneley wave attenuation response in some gas layers is eliminated, sensitivity can be effectively improved, and the position of a gas-bearing stratum is accuratelyjudged.

Description

technical field [0001] The invention relates to the technical field of geophysical well logging, in particular to a method and a device for identifying gas layers by using longitudinal waves and Stoneley waves. Background technique [0002] In formations such as dolomite and limestone, due to the high resistivity of the rock skeleton, the background value of the conventional resistivity curve obtained from well logging is relatively high. At this time, if the formation contains natural gas, the conventional resistivity curve is often difficult to reflect the Changes in natural gas content; in addition, because dolomite and limestone reservoirs generally have complex pore structures, the excavation effect of neutron logging and the cycle jumping phenomenon of acoustic logging curves in gas-bearing formations are not obvious. Conventional logging identification of high-resistivity gas layers is difficult. [0003] In the prior art, since array acoustic logging may attenuate t...

AI Technical Summary

Problems solved by technology

However, complex phenomena such as simultaneous attenuation of longitudinal waves and Stoneley waves, separate attenuation, and different attenuation sizes may occur in natural gas layers, resulting in low sensitivity of existing methods and possible gas layer leakage

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