Measurements of methane bubble size distribution from a remotely operated platform in the presence of oil

Subsurface releases of crude oil and methane gas may occur naturally or due to manmade, sometimes catastrophic, events. To determine the quantity of oil and gas being released, measurements can be performed on both the crude oil droplets and methane bubbles to determine their sizes and concentration in the water column. An acoustic backscatter measurement, in the 20–110 kHz range, was developed using transducers mounted on a commercial ROV insonifying an intentional subsurface oil and gas release in a large wave tank. Bubble size distributions for methane mixed in a plume of crude oil were obtained by performing an inversion on acoustic backscattering measurements after accounting for transducer properties and sound transmission through the water column. Due to the rapid nature of the measurements, monitoring of the evolution of the plume in time was also possible. Distributions were consistent with independent measurements using laser scattering techniques.