Discussion of “Acoustic characteristics on clayey-silty sediments of the South China Sea during methane hydrate formation and dissociation” Liu et al. Energy 282 (2023) 128978

Discussers read with immense research interest the article published by Liu et al. [1] that describes the “Acoustic characteristics on clayey-silty sediments of the South China Sea (SCS) during methane hydrate formation and dissociation.” Authors have investigated the variations in P-wave and S-wave velocities during methane hydrate synthesis and dissociation under different effective stress conditions in artificially prepared clayey-silty sediments resembles the native soil samples of South China Sea. Further, mechanism that explains the influence of hydrate growth on acoustic velocities during its formation was proposed. Furthermore, an attempt has been made to define the dimensionless parameter Ψ in terms of the recorded S-wave velocities to characterize the anisotropy of the sediment with hydrate saturation (SH). Moreover, model that relates the SH with recorded P-wave velocities under different effective stress conditions has been developed. Though the study presented some fascinating results, discussers have observed important concerns pertaining to (i) the experimental setup & procedure adopted to calibrate the acoustic transducers, (ii) preparation & characterization of the sediments and experimental methodology, (iii) interpretation of results, and (iv) feasibility of the proposed model for practical applications. Hence, through this attempt, discussers seek to highlight the issues that will be useful for accurate estimation of SH & small strain stiffness of hydrate bearing sediments (HBS) and prediction of the hydrate morphology by employing P-wave and S-wave velocities which in turn will be helpful to alleviate potential dissociation induced geomechanical issues such as instability of submarine slopes, reservoir subsidence, sand migration, wellbore failure, etc., during methane gas extraction.