液氮循环冷冲击作用下砂岩铀矿储层孔隙结构演化及分形特征研究OA

Investigating the evolution of sandstone pore structure under cyclic cold shock is of great significance for evaluating the feasibility of permeability enhancement in sandstone-type uranium reservoirs treated with low-temperature liquid nitrogen.In this paper,sand-stone specimens were subjected to cyclic liquid nitrogen cold shock treatment,and scanning electron microscopy,low-temperature nitrogen adsorption,automatic mercury in-trusion porosimetry,and fractal theory were employed to comprehensively characterize the microscopic pore structure of the treated rock specimens.The results indicate that:1)Cy-clic liquid nitrogen cold shock can effectively weaken the intergranular cementation strength of sandstone,and even cause fracture of mineral grains,and increase the number of intergranular pores and microcracks.2)After the shock treatments,the pore size distri-bution of the sandstone specimens exhibits a bimodal pattern.The volumes of both micro-pores and macropores increase significantly,which improves pore structure.3)Fractal di-mension results show that the surface of micropores in the treated specimens become smoot-her.The structural complexity of smaller pores(50 nm≤d<5 000 nm)increases,whereas the complexity of larger pores(d≥5 000 nm)decreases,leading to an enhanced pore connectivity.These findings provide theoretical and technical support for permeability enhancement of low-permeability sandstone uranium reservoirs through cyclic liquid nitrogen cold shock fracturing.