多孔灰岩局部化变形过程的渗流演化机理

Localized deformation of rocks is a common geological phenomenon that plays a crucial role in areas such as underground carbon dioxide storage,oil and gas extraction,and groundwater management.In the process of oil and gas depletion production,the pressure of the downhole pore fluid decreases,resulting in the increase of the effective stress,causing localized deformation of reservoir rock,decreasing the permeability,which would affect production capacity.Currently,there is a well-known understanding of the macroscopic research on strain localization formation and transportation characteristics,but there is less research on the microscopic mechanisms of transportation characteristics during the strain localization formation.We conducted synchrotron in situ CT imaging during triaxial compaction in Leitha limestone.Based on CT data during strain localization formation stage,we adopted Lattice Boltzmann method to analyze transportation characteristics during strain localization formation.The preliminary research results show that the change in rock permeability is mainly influenced by the localized deformation of its internal pores.In the first yielding stage,the connected macropores collapse and the porosity significantly decreases,however,the permeability only slightly decreases,indicating that the connected porosity didn't show a good correlation with permeability.As the stress increases,some key throats of the pore network will be compacted,even with the phenomenon of channel blockag induced by grain crushing,resulting in a significant decrease in permeability.It indicates that the deformation of the key throat of pore network plays a dominant role in permeability changes.Further quantitative analysis will be conducted in the future.