Simulation experiment on acoustic characteristics of shallow water flow and model application in deepwater drilling

In deepwater drilling, major accidents such as well leakage or even blowout are likely to occur once drilling encounters shallow water flow. The accuracy qualitatively predicted by shallow water flow with conventional seismic sections is low. Therefore, a method based on simulation experiments to quantitatively predict shallow water flow pressure and evaluate the risk level is proposed. According to the propagation velocity characteristics of sound wave in water and saturated rock medium, the acoustic simulation experiment on shallow water flow was carried out. The research shows that: the propagation velocity of longitudinal wave in deep water and shallow water flow formations increases with the increase of formation pressure, the larger the formation porosity, the slower the sound wave propagation velocity. Through data fitting it is found that that the longitudinal wave and shallow water formation pressure, porosity shows a power exponential function relationship. Based on the experimental results, a dual-parameter model of sound velocity and shallow water flow formation pressure, porosity was established, so as to achieve the purpose of predicting shallow water flow formation pressure according to sound velocity. By using the finite element software, the geological modeling and blowout simulation of the shallow water flow formation were performed, and the pressure coefficient range of different risk levels upon to drilling because of the shallow water flow was defined. The acoustic prediction of shallow water flow and the risk assessment method has been applied in the deepwater area in the South China Sea, which verifies the feasibility of the sound wave recognition and prediction technology for shallow water flow in deepwater drilling.