Experimental Study on the Gas Permeability of Marine Sediments with Various Hydrate Saturations and Effective Stresses

Abstract

Marine methane hydrate is considered to be one of the future energy sources with the most potential due to its tremendous reserves. Permeability is a key parameter affecting the recovery efficiency and gas recovery of gas hydrate. We studied the dependence of gas permeability on hydrate saturation and effective stress using remolded core from the South China Sea. The results show that, with increasing hydrate saturation, the gas permeability first decreases, then increases, and decreases finally, which may be due to the combined effect of the growth habit of hydrates in the pores, the interaction between hydrates and particles, and the effect of effective stress. The formation and decomposition of hydrates in the sediment will cause a decrease in gas permeability. When hydrate saturation is 40.66%, the gas permeability decreases by 13 times due to hydrate formation. The gas permeability presents an approximate linear negative relationship with effective stress. The presence of hydrate significantly reduces the stress sensitivity of the sediment. A stress-sensitive critical saturation between 36.60 and 40.66% makes the ratio of permeability change to effective stress change close to a constant. This work bridges the gap of gas permeability of marine sediments between laboratory samples and natural sediments, providing reliable seepage parameters for the numerical simulation of marine hydrate exploration.

The Impact of Gas Flow on Hydrate Reformation and Reservoir Seepage Characteristics in Clayey Silt Sediments

“…Schematic diagram of hydrate decompression mining process. Figure modified with permission from ref . Copyright 2021 American Chemical Society.…”

Experimental Study on Permeability of Methane Hydrate Clayey Interbedded Sediments Considering Effective Stress and Hydrate Dissociation

“…The results show that under unconsolidated (consolidation degree = 20%) and low effective stress (σ′ = 1.2 MPa) conditions, the gas permeability increases gradually with the decreasing methane hydrate saturation, indicating that hydrate saturation is the main factor dominating dynamic permeability at low hydrate saturation. This is crucial for understanding the permeability characteristics of hydrate sediments containing a large number of fine components in the muddy silt type. − Li et al studied the water-phase-effective permeability of silty sand soil and silty clay containing methane hydrate by the steady-state water injection method. The experimental results show that lower methane hydrate saturation also has a large effect on the absolute permeability of the water phase.…”

Effect of Hydrate Distribution on the Mechanical Response of Hydrate-Bearing Sand: Discrete Element Method Simulation

“…Second, NGHs have abundant reserves; conservative estimates suggest that the energy contained in NGHs is twice that of all other hydrocarbon sources. Third, NGHs possess an extremely high energy density, with one cubic unit of NGHs containing as much as 180 SCM (standard cubic meters) of gas. , Production of natural gas from NGH reservoirs requires breaking the thermodynamic equilibrium of NGHs. − However, hydrate-bearing sediment (HBS) exhibits a complex mechanical behavior due to the metastable structure of NGHs . In the exploitation of NGHs, the microstructure of HBS usually changes, such as cementation failure and local shear deformation, resulting in structural instability of the production well, seabed deformation, and even submarine landslides. , Therefore, a comprehensive mechanical study of HBS is required to ensure the safe exploitation of NGHs.…”