Temperature Effect on Undrained Mechanical Properties of Hydrate-Bearing Clayey Silts in the South China Sea

Nearly90% of hydrate resources are found in low-permeability andfine-grained soils, which requires investigation on the undrainedmechanical characteristics of hydrate-bearing fine-grained soils (HBFGSs)to accomplish safe and efficient hydrate exploitation. Additionally,factors such as hydrothermal and geothermal gradients of the marinesediments and hydrate extraction by heat injection method simultaneouslyrequire an understanding of the temperature effect on the stabilityof HBFGSs and overburden hydrate-free sediments. For these reasons,this study conducted consolidated undrained (CU) triaxial experimentson water-saturated hydrate-free and hydrate-bearing clayey silts inthe South China Sea (SCS) at different temperatures and presentedresults of temperature effects on undrained mechanical properties.This paper reveals the following and analyzes the reasons accordingly:(1) the failure strength of the hydrate-free clayey silts increaseswith temperature, whereas the failure strength of hydrate-bearingclayey silts decreases with temperature; (2) the temperature has almostno effect on the fitting line of end-of-test data for undrained shearof hydrate-free clayey silts in p & PRIME;-q space; and (3) the presence of hydrates has a considerableinfluence on the excess pore pressure response and effective stresspaths of clayey silts. The results will contribute to the understandingof the influences of environmental changes and hydrate extractionby thermal injection on the stability of hydrate reservoirs in theSCS.

Automated summary

This study focuses on the investigation of undrained mechanical characteristics of hydrate-bearing fine-grained soils in order to achieve safe and efficient hydrate exploitation. The results show that temperature has a significant influence on the failure strength of clayey silts, both with and without hydrates. The presence of hydrates also affects the excess pore pressure response and effective stress paths of clayey silts. These findings contribute to a better understanding of the stability of hydrate reservoirs in the South China Sea under environmental changes and thermal injection for hydrate extraction.