Gas outburst with sediments because of tetrahydrofuran hydrate dissociation

Abstract

SUMMARY Methane hydrate (MH) is a new energy resource in the 21st century. But the dissociation of MH from sediments during the MH exploration or oil/gas exploration under a hydrate layer accompanied by the softening of soils and formation of excess pore gas pressure may lead to ground failures and environmental disasters. In this study, experiments on modeling the weakening and failure of the sediment by heat-induced dissociation of tetrahydrofuran (THF) hydrate were presented. The failure mode of gas outburst was observed. Gas outbursts is a process where gas and soils in hydrate-dissociation zone burst out after the continuous skeleton of over-layer is fractured during the expansion of the dissociation zone and the formation of gas zone and excess pore gas pressure. An analytical method is presented by decoupling heat transfer and soil deformation. The geometrical and mechanical similarities for gas outburst are obtained. An empirical criterion for the occurrence of outburst is proposed using the theory of thermal conduction, rigid plastic mechanics, and the experimental data.

Recent Advances in Methods of Gas Recovery from Hydrate-Bearing Sediments: A Review

“…Furthermore, limited by the ultralow permeability of HBS and lower tensile strength in the NGH dissociation zone, local pore pressure rebound may emerge . When the pressure exceeds the shear stress of HBS, layered fractures and even outbursts will appear in HBS (Figure b), , which is not conducive to HBS stability. In addition to the vast energy input due to the ineluctable heat loss in HBS when using the thermal stimulation methods, the defect that the average daily gas production on- site is far lower than the commercial gas production threshold for a single well mainly results in the economic challenges.…”