Objective/Goal: The goal of this project was to develop acoustic techniques to measure the droplet size distribution for subsea release of crude oil and dispersants in the presence of natural gas. It built off of the results of ARA's previous proof-of-concept study for using ultrasound to assess dispersant efficacy by measuring oil droplet sizes. In this project, ARA added the additional variable of natural gas to advance their measurement technology to separate the responses from oil droplets and natural gas bubbles in a subsea plume.
ARA performed measurements in their lab, at SINTEF and at Ohmsett. ARA identified specific frequency ranges for improving dispersant effectiveness monitoring. During this work ARA developed acoustic measurements utilizing the complete waveform and frequency response of the attenuation and backscattering. The measurements of acoustic attenuation and backscattering over specific frequency ranges correlated well the percentage of dispersed oil. ARA also tested a commercial sonar instrument and an Acoustic Doppler Velocimeter (ADV) to determine if these devices could be used to measure the effectiveness of dispersants and if they were compatible with the measurements developed during this project. While commercial sonar and ADV instruments are useful for imaging and measuring current flow, respectively, they were too limited in their data collection and interpretation to allow the detailed analysis of the frequency response to measure the droplet size or the amount of oil that was dispersed.
Update project initiatiton date to
September 10, 2012.