Bubble Plume Detection Technology For Submarine Cold Seep Based On Acoustic Characteristics

Submarine cold seep is a kind of marine geological phenomena widely developed in active and passive continental margins,which have been found in the oceans around the world.Potential energy factors and environmental effects have attracted much attention in the study of submarine cold seep.The research of submarine cold seep is of great significance in marine engineering safety,gas hydrate development,conventional oil and gas exploration,global climate change,carbon cycle and extremophile communities.Bubble plumes in cold seep are closely related to the distribution of gas hydrates in the seabed.Rich depositional reservoirs in gas hydrates can be usually found at the bottom of bubble plumes.In recent years,studies have found that the distribution of bubble plumes in seawater has a good indication for the boundary of hydrate stabilization zone.In this paper,the present situation of bubble plumes detection in cold seep has been reviewed.The acoustic scattering characteristics of bubble plumes in cold seep are analyzed,and the related ideas of acoustic detection of bubble plumes in cold seep are clarified,and the gas output of bubble plumes in cold seep is estimated.Based on the experimental data of water tank and the theory of acoustic detection,the effects of three parameters of CW acoustic pulse signal on the detection imaging of submarine cold seep bubble plume,namely,the acoustic frequency,the transmitted power and pulse duration are analyzed.At the same time,the principles and scope of selecting these parameters are further clarified based on the data of the cold seep investigation and artificial cold seep experiment at the Lao Tie Shan sea area in Bohai and Yellow Sea.Aiming at the abnormal interference zone in the acoustic water profile,a method of changing the time delay of pulse emission to eliminate the interference zone in the acoustic water profile is proposed,this can further optimize the acoustic imaging effect of the submarine cold seep bubble plume.In addition,this paper on the basis of the previous research,Several geophysical model using the high accuracy finite difference method was employed to simulate the responses from the seismic wave field of the submarine cold seep bubble plume;wave impedance and acoustic scattering characteristics were also analysed in this study.The results obtained from this research might be useful for further studies in this field.