A laboratory study of acoustic behaviors of bubbles caused by oil leakages

A laboratory study to simulate oil leakages was conducted under controlled conditions, such as pressures, flow rates, jet velocities, and crack sizes. Two types of oil leakages, a few bubble cases and the constant flow bubble cases, were tested to simulate oil seepages either from seafloors or from oil well and pipe-line breaches. Two gases, nitrogen and methane, were used for the investigation. The bubble sounds were recorded by hydrophones. It was found that (1) the resonant frequency decreased nonlinearly with the needle diameter and (2) the sound intensity in terms of the total energy increased with both the flow rate and jet velocity. For acoustic bubble modeling, we implemented the theory of bubble dynamics to analyze the bubble sounds. We considered (1) the dependence of the resonant frequency on the size of crack, and (2) the dependence of the sound intensity in terms of the total energy on the flow rate and jet velocity. Several correlations between the oil leakage properties and acoustic responses were established and interpreted. The outcome of the observations and modeling enhanced our understanding of the mechanisms of bubble-induced sounds and will be applied to guide the assessment of the features of oil.