Simplified traditional bubble-motion equation and air-gun wavelet simulation based on a Van der Waals gas model

• Published in: Applied geophysics Vol. 18; no. 4; pp. 537 - 544
• Main Authors: Bing-Shou, He, Hao, Guo, Nan, Hu
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.12.2021; Springer Nature B.V
• Subjects: Acoustic waves; Air; Air flow; Bubbles; Coordinate systems; Earth and Environmental Science; Earth Sciences; Equations of motion; Excitation; Far fields; Geophysics/Geodesy; Geotechnical Engineering & Applied Earth Sciences; Heat exchange; Ideal gas; Methods; Modelling; Movement; Offshore; Seismic data; Seismic exploration; Seismic Modeling and Wave Propagation; Seismological data; Simulation; Spherical coordinates; Spherical waves; Wave equations; Van der Waals gas wave; bubble-motion equation; air-gun source; wavelet simulation
• DOI: 10.1007/s11770-021-0916-0
• ISSN: 1672-7975

An air-gun source is the most commonly used excitation method in offshore seismic exploration. The excitation characteristics of an air-gun source affect seismic data quality. Far-field wavelet simulation is an important approach to study these characteristics. Compared to the measured wavelet, far-field wavelet simulation based on a traditional bubble-motion equation and ideal gas wavelet model has some disadvantages, such as a greater amplitude and smaller pulse attenuation velocity. Here, we start from the linear acoustic wave equation in the spherical coordinate system to deduce an improved, simpler bubble-motion equation and develop a Van der Waals gas wavelet model based on this equation. Unlike the existing methods, our method considers the high-pressure environment during actual excitation, heat exchange between the bubble and outside water, and change in the air flow at the muzzle. The results show that the far-field wavelet simulated using this model is closer to the measured wavelet than that of the ideal gas wavelet model. At the same time, our method has a more succinct equation and a higher calculation efficiency.