GEOMECHANICAL BEHAVIORS OF LABORATORY-FORMED NON-CEMENTING HYDRATE-BEARING SEDIMENTS

Abstract:

Natural hydrate-bearing sediments (HBS) have been known to exist with non-cementing pore habits, i.e., pore-filling, load-bearing, or patchy type. However, few laboratory studies have been conducted to characterize geomechanical behaviors of non-cementing CH₄-HBS, which are of great importance in engineering the process of drilling and gas production in natural hydrate reservoir. In this study, we conducted multi-stage drained triaxial tests on laboratory synthesized CH₄-HBS samples, which were formed in sand-clay mixtures (5%wt kaolinite) to have non-cementing habits. Three different effective confining stresses, σ₃′ = 0.69, 1.38, and 2.76 MPa, were applied on the HBS with the hydrate saturation, S_h, in the range of 0 to ~ 40%. The result confirms that the strength and stiffness of HBS increases with effective confining stress and hydrate saturation. It is also demonstrated that when compared to the cementing HBS, the non-cementing HBS has lower strength and cohesion, owing to less inter-particle adhesion effects from non-cementing hydrate.