Shipboard Acoustic Observations of Flow Rate From a Seafloor‐Sourced Oil Spill

Abstract

In 2004 a debris flow generated by Hurricane Ivan toppled an oil production platform in Mississippi Canyon lease block 20 (MC20). Between 2004 and the installation of a containment system in 2019 MC20 became an in situ laboratory for a wide range of hydrocarbon in the sea-related research, including different methods of assessing the volumetric flow rate of hydrocarbons spanning different temporal scales. In 2017 a shipboard acoustic Doppler current profiler (ADCP) and high-frequency (90 to 154 kHz) broadband echosounder were deployed to assess the flow rate of liquid and gas phase hydrocarbons. Measurements of horizontal currents were combined with acoustic mapping to determine the rise velocity of the seep as it moved downstream. Models of the rise velocity for fluid particles were used to predict the size of oil droplets and gas bubbles in the seep. The amplitude and shape of the broadband acoustic backscatter were then used to differentiate between, and determine the flow rate of, hydrocarbons. Oil flow rate in the seep was estimated to be 56 to 86 barrels/day (mean = 71 barrels/day) while the flow rate of gaseous hydrocarbons was estimated to be 98 to 359 m 3 /day (mean = 229 m 3 /day).

Underwater Acoustic Technology-Based Monitoring of Oil Spill: A Review

“…As shown in Table 2, acoustic instruments used in underwater oil spill detection include echo sounders, multibeam sensors, side-scan sonars, and acoustic Doppler current profilers. An echo sounder can identify underwater oil leaks by the changes in acoustic backscattering intensity [59][60][61]. Multibeam sensors have good target classification and recognition functions, and can provide a three-dimensional diffusion map of oil droplets in the water column [62][63][64].…”

“…Side-scan sonar can quickly monitor large areas of oil spills through the image of acoustic reflectivity [65,66]. The acoustic Doppler current profiler can obtain the dynamic characteristics of oil droplet targets and then estimate the oil spill leakage situation [60,67]. Some acoustic instruments use high-frequency sound waves to monitor underwater oil droplets.…”

“…Broadband acoustic backscatter has been used to identify fish species and plankton, among others [68,69]. By using the amplitude and shape of broadband acoustic backscatter, it is possible to differentiate hydrocarbons in leaked substances and determine the flow rate of hydrocarbons, and to estimate the distribution of leaked gas and oil droplets [60]. Acoustic technology has been experimentally verified to detect oil and gas in water columns, but subsequent sampling or fitting of oil droplet and bubble models are necessary to verify and estimate the acoustic characteristics of observed oil droplets, ensuring the accuracy of detection data and improving the sensitivity and reliability of underwater oil spill monitoring.…”

“…Mississippi River oil spill (2015) Mississippi MC20 oil spill Acoustic backscatter images of underwater oil droplets using side-scan sonar [65]. Shipboard acoustic observations with ADCP and high-frequency broadband echo sounder to assess liquid and gaseous hydrocarbon flow rates [60].…”

“…Various increasingly complex acoustic scattering studies have been reviewed, such as simplified spherical droplet acoustic scattering models, the effect of crude oil density and sound speed on acoustic scattering under ocean temperature and pressure, the final impact of the degree of deviation of oil droplets from spherical on acoustic scattering, and the prediction of the sizes of leaking oil droplets and bubbles through a fluid particle rising speed model, taking into account the reality of oil spill treatment, such as the status of oil droplets and bubbles under dispersants, and other chemical reagents. The oil droplet target calculation method has been optimized and the underwater oil droplet model has been improved [59,60,70,74].…”