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This study investigates the transport of methane released from gas hydrate decomposition through sedimentary layers to quantify its flux into the atmosphere, a critical process given methane's role as a major greenhouse gas. A novel methodology was developed to model two-phase, unsteady gas flow in regions of hydrate decomposition, incorporating key factors such as relative permeability curves, capillary pressure, hydrostatics, and gas diffusion. Numerical simulations revealed that to achieve a gas front rise rate of 7 m/year, the gas accumulation rate must not exceed 10−8 kg/m3·s. At higher accumulation rates (10−6 kg/m3·s), gas diffusion has minimal impact on the saturation front movement, whereas at lower rates (10−8 kg/m3·s), diffusion significantly affects the front's behavior. The study also established that the critical gas accumulation rate required to trigger sediment blowout in the hydrate decomposition zone is approximately 10−6 kg/m3·s, several orders of magnitude greater than typical bubble gas fluxes observed at the ocean surface. The proposed model improves the ability to predict the contribution of Arctic shelf methane hydrate decomposition to atmospheric methane concentrations. [ABSTRACT FROM AUTHOR]

The work is aimed at the research of the nonlinear effects of the rock toughness on the hydraulic fracturing process and hence at the necessity of knowledge of rock fracture toughness. Fracture toughness characterizes the rock's ability to resist the cracking process. Numerical models of the fracture propagation based on the postulates of failure mechanics. Fracture toughness is one of the determining parameters along with the elastic properties of the rock and the injection conditions. The aim of the paper is to study the nonlinear effects of the rock toughness and determine how much the fracture toughness affects the fracture length in the created numerical model describing the laboratory experiment. The laboratory setup made it possible to create conditions that determine the actual fracturing process. The strength parameters of the model material were measured. In particular the fracture toughness was measured too. The paper considers how strongly the fracture toughness of a medium affects the fracture length obtained with the help of a numerical model calibrated in the laboratory experiment. [ABSTRACT FROM AUTHOR]