Reconstructing the 3-D Methane Plume Image Using Portable Shipborne Sonar

Abstract

The methane plume is a sign of subsea natural gas leakage, which generally overflows from the seabed as a bubble plume. The methane plume is a complex 3-D structure that depends on the bubble rising path, which cannot meet the exploration and research needs only through a 2-D image. Based on the developed portable methane plume sonar and backscatter characteristics of the methane bubble overflowing from the methane plume, this article focuses on the 3-D image reconstruction method for the methane plume on the seafloor according to the image projection principle and 2-D measuring image of discrete survey lines in the sea trial. First, the bisliding window correction (BSWC) method is designed to correct the distorted methane plume contour under the beam open angle of the sonar transducer. Second, the geometric-constrained convergence method (GCCM) based on the steepest descent algorithm is proposed to estimate the location of the methane plume and converge the contour under each depth profile. Finally, the 3-D plume image can be formed. The reconstructed 3-D image of the plume has been obtained through the sea trail and data processing. The overlap area between the detection contour and the inversion contour was compared using the inversion algorithm, and the average overlap probability was 79.21%, verifying the effectiveness of the proposed reconstruction method.