Gas Seepage Detection and Gas Migration Mechanisms

Abstract

Gas seepages are often observed at the seafloor and can form cold seep systems, which are important for climate change, geohazards, and biogeochemical cycles. Many kinds of methods have been used to detect gas seepages, e.g., video imaging, active acoustic, passive acoustic, and direct gas sampling. In this chapter, we introduce the characteristics of these methods and show their applications in the South China Sea (SCS). Particle image velocimetry (PIV) technology is used here to quantitatively detect gas seepage in the northwestern SCS and visualize the seepage flow field. The gas migration mechanisms are also discussed. With the development of technologies, long-term, three-dimensional, and comprehensive observations is permitted to quantitatively characterize gas seepages, which can help us understand the formation and mechanism of gas seepages further in the future. Physical and numerical simulations of gas migration and geohazard processes would also be helpful in the future for understanding the fate of gas seepages.

Contrasting Methane Seepage Dynamics in the Hola Trough Offshore Norway: Insights From Two Different Summers

“…The SBES survey performed during CAGE 18-2 revealed 43 clusters with flow rates ranging from 0.2 to 64 mL min 1 , an average of 14.4 (SD, 19.9) mL min 1 and a median of 6.4 mL min 1 (Figure 1). These values are smaller than other areas such as, for example, in the shallow Dutch Dogger Bank in the North Sea (from 0.43 to 2,148.5 mL min 1 , Römer et al, 2017 corrected after Veloso et al, 2019), near the gas hydrate stability limit offshore Svalbard (2.3-1,852 mL min 1 , Ferré et al, 2020), or in the South China Sea (94.8 mL min 1 in average per flare, Zhang et al, 2023). Flares were emitted in the three main areas from an average depth of 206 m (median depth of 216 m ranging from 82 to 244 m), in agreement with the MBES data.…”