Due to the complex geological conditions in the polar regions, more than 80% of the polar regions have shallow geological hazards, and most drilling accidents are related to shallow geological hazards. The research on shallow geological hazards at home and abroad mainly focuses on the description and response to shallow geological hazards. In terms of measures, prediction methods are mainly geophysical methods. The existing technology is difficult to achieve quantitative and accurate prediction of shallow geological disasters, so related work is urgently needed. Natural gas hydrate is one of the main risks of shallow geological hazards in polar drilling. The thesis has carried out acoustic identification and prediction technology for shallow natural gas hydrates. According to the principle of different propagation speeds of sound waves in different propagation media, since natural gas hydrates are filled in the pores of rock particles, different saturation and porosity constitute different media. Therefore, the outdoor cryogenic sound wave measurement experiment scheme is used. Under the experimental conditions of low temperature, the influence of gas hydrates with different saturation and porosity on the acoustic wave velocity in the polar low temperature environment is simulated.
The results show that the longitudinal wave velocity will change significantly when passing through the gas hydrate-bearing formation. The wave speed of the material increases with the increase in saturation, and decreases with the increase in porosity. The curve of the wave speed under different experimental conditions is obtained by fitting, and a prediction technology for polar shallow geological disasters is obtained, and polar drilling is established. The risk assessment chart of natural gas hydrate can quantitatively describe the degree of geological disasters, thereby providing theoretical support for drilling operations in the polar cold sea and reducing the risks of drilling operations. It can also provide a theoretical reference for the follow-up polar shallow drilling technology to predict gas hydrate.
