Investigation on gas migration in saturated materials with low permeability

Abstract

International audienceInvestigation of the hydro-mechanical effects on gas migration in saturated materials with low permeabilityis of great theoretical and practical significances in many engineering fields. The conventional two-phaseflow (visco-capillary flow) theory, which regards the capillary pressure as the only controlling factor in gasmigration processes, is commonly adopted to describe the gas flow in geo-materials. However, formaterialswith lowpermeability, the conventional two-phase flow theory cannot properly describe the gasmigration.In this work, hydro-mechanical coupled gas injection tests were conducted. The volumetric variation of theliquid for applying the confining pressure in the specimen cell and the gas flow rate were monitored. Testresults indicate that gas migration is influenced by the capillary pressure and the mechanical stress simultaneously.The two key parameters of the gas entry pressure Pentry and the gas induced-dilatancy pressurePdilatancy are introduced for description of gas migration with respect to the capillary pressure and the mechanicalstress effects, respectively. When the gas injection pressure is smaller than the Pentry and thePdilatancy, the balance between the gas injection pressure and the confining pressure will lead to an intermittentgas flow. Sudden increase of gas flow rate could be observed once the gas injection pressure approachesthe Pentry or the Pdilatancy. For higher gas injection pressures, the mechanical stress effects on gas migrationcould not be neglected. The sudden increase of gas flux under high gas injection pressures could be causedby the mechanical induced-dilatancy of channels, capillary pressure induced-continuous flow pathways, aswell as the failure of sealing-efficiency. The failure of sealing-efficiency is closely related to the differencebetween the gas injection pressure and the confining pressure rather than the properties of the materialtested. Monitoring the volume of liquid for applying confining pressure is helpful for detecting the failureof sealing efficiency and the mechanism of gas breakthrough

The Origin of Non-thermal Fluctuations in Multiphase Flow in Porous Media

“…Wettability heterogeneity may also impact the magnitude of fluctuations due to the associated energy dissipation (Murison et al, 2014). Also, fluctuations are stronger for a gas-liquid system and more often reported explicitly (Alkan and Müller, 2008;Reynolds and Krevor, 2015;Xu et al, 2015;Spurin et al, 2020), which suggests that viscosity ratio may be an important factor, which has been also reported in (Spurin et al, 2019).…”

Investigating Soil Desiccation Cracking Using an Infrared Thermal Imaging Technique

“…This results in the presence of weathered soil fragments, a potential sediment resource for wind transportation and the subsequent formation of dust storms (Pye & Tsoar, 2008; Style et al., 2011; Yesiller et al., 2000; Zielinski, et al., 2014). For environmental sites, such as landfills and reservoirs of radioactive nuclear waste, clay‐based soils establish multiple barriers that separate the waste from the biosphere (Ng et al., 2015; Xu et al., 2015). Owing to the repeated drying‐wetting paths, the formation of soil cracks impairs the long‐term protection functionality of the barrier, causing the possible leakage of toxic volatile gases and liquids, as reported in previous studies (Albrecht & Benson, 2001; Du et al., 2022, 2021; Kalkan, 2009; Ma et al., 2019; Rayhani et al., 2007; Seiphoori et al., 2014; Ye et al., 2020).…”

Prediction Method for Hydraulic Conductivity considering the Effect of Sizes of Ellipsoid Soil Particles from the Microscopic Perspective

“…Hydraulic conductivity is one of the most important and useful parameters in the study of the seepage process of porous media [1] and plays a vital role in the research of consolidation, settlement of soils and foundation, rheology [2][3][4][5], dewatering design [6][7][8], migration of gas and liquid [9][10][11], sandstone storage [12][13][14][15], storage of CO 2 and nuclear waste [16][17][18][19][20], and other geological and geotechnical engineering problems. Generally, it is difficult to measure dynamic variation of the hydraulic conductivity by experimental means.…”