P-wave of hydrate-bearing sand under temperature cycling

Abstract

P-wave velocity was used to study the formation of gas hydrates that were formed from methane, [Formula: see text], and propane in the pores of sand particles under temperature cycling. During the temperature-cycling tests, additional hydrate or ice formation can be demonstrated by investigating the velocities and amplitude of the P-wave. The experiments indicated that temperature cycling can accelerate hydrate accumulation in the pore space of sediments. Although most of the water in the pore space of sand can transform into gas hydrate after several temperature cycles, the formation of propane hydrate was slower than that of methane hydrate or [Formula: see text] hydrate. To estimate the hydrate saturation, an effective-medium theory was used. The results corroborated the validity of the contact model that the hydrate acted as a mineral grain to support the sediment frame. According to the calculation results, the methane-hydrate saturation can be up to 0.85 after three temperature cycles. The evaluation results accord with those of some natural hydrates in sand layers.