Mechanical Characteristics of Gas Hydrate-Bearing Sediments: An Experimental Study from the South China Sea

Abstract

Clarifying the mechanical characteristics of gas hydrate-bearing sediments (GHBS) from a mechanical perspective is crucial for ensuring the long-term, safe, and efficient extraction of natural gas hydrates. In this study, seabed soft clay from the northern South China Sea was utilized to prepare clayey silt samples, aligning with gradation curves related to hydrate extraction projects in the Shenhu area of the South China Sea. Utilizing the high-pressure low-temperature hydrate triaxial testing system (ETAS), twelve sets of triaxial shear tests were conducted. The results highlight that increases in hydrate saturation and confining pressure significantly enhance GHBS’ strength and stiffness, with more pronounced volume expansion observed during shearing. These tests have elucidated the mechanical responses of GHBS. Subsequently, empirical formulas were developed to characterize their properties under varying conditions. Additionally, based on the experimental data, the micro-mechanisms of GHBS were analyzed, suggesting that hydrates notably contribute to the filling and cementing effects in GHBS, with these effects varying with changes in hydrate saturation and confining pressure. This study contributes to a deeper understanding of the fundamental mechanical properties of GHBS.

Pore Water Conversion Characteristics during Methane Hydrate Formation: Insights from Low-Field Nuclear Magnetic Resonance (NMR) Measurements

“…To sum up, the conversion ratio of pore water (C w ) during the methane hydrate formation can be obtained by Equation (15).…”

“…Hydrate saturation is an essential indicator for evaluating hydrate resources through hydrate volume percentage in hydrate-bearing sediments (HBS). Different levels of hydrate saturation cause significant differences in the response of physical parameters such as acoustic velocity [11,12], resistivity [13,14], mechanical properties [15][16][17], and permeability [18,19] of HBS. Therefore, accurately obtaining hydrate saturation is essential for the accuracy of hydrate resource evaluation and the rationality of exploitation program formulation.…”