Mechanical properties of methane hydrate-bearing sandy sediments under various temperatures and pore pressures

Abstract

According to the marine geological survey, marine hydrate reservoir's temperature (T) and pore pressure (P.P) conditions change with water depth and burial depth. Besides, the change in T and P.P conditions would also occur during the exploitation of hydrate. It is meaningful to study the combined effects of T and P.P on mechanical behaviors of methane hydrate-bearing sediments (MHBSs) to evaluate the hydrate reservoir's stability. In this work, a set of mechanical experiments were carried out to study the effect of T and P.P on the mechanical properties of MHBSs. With decreasing T and increasing P.P, the samples' strength increased, and the stress-strain behaviors also changed. Moreover, with decreasing T and increasing P.P, the samples' dilatant volumetric strain increased. The mechanical properties of MHBSs were affected by the ‘distance’ between the test condition point and the phase equilibrium curve. With increasing ‘distance’, the sample s' strength increased; simultaneously, the stress-strain behaviors also changed. A shift line was introduced in temperature-pressure space, which was the boundary between the hardening and softening behaviors of the MHBSs. Furthermore, we established the numerical relation between strength, T and P.P in this paper. The results of this study can be used for the studies of reservoir stability during methane hydrate productions.