应力和侵蚀性溶液渗透耦合作用下碳酸盐岩渗透特性试验研究

为研究不同应力及溶液组合下碳酸盐岩渗流特性演化规律,选择H2SO4溶液、蒸馏水作为渗透流体,使用岩石耦合渗透试验装置对碳酸盐岩试样分别进行较长时间的渗透试验,得到三种不同工况下岩石试样渗透率和渗出液中矿物离子浓度随时间变化的曲线,分析了试验中围岩、渗透压、溶液等影响因素与渗透率、岩石内部矿物质溶解规律之间的内在联系。结果表明,试验初期阶段,围压对岩样渗透率有较大影响,恒定围压施加后使得岩样孔隙受到压缩从而影响渗透率。试验过程中,渗透压的增大会导致岩样渗透率产生短时间的上升,随后岩样渗透率逐渐回落。不同渗透溶液则有不同的影响,H2SO4溶液对岩样内部的侵蚀性较强,在岩样上游段产生较强溶解,当溶解的矿物离子浓度达到过饱和后,可能在下游段产生沉淀,使得岩样整体渗透率不断降低;而蒸馏水对岩样的侵蚀作用较弱,沿程产生均匀溶解,不能对孔隙结构造成较大改变,整体渗透率保持稳定。岩样整体渗透率的变化是应力、渗透溶液的溶蚀作用和矿物沉淀共同作用的结果。研究成果可用于指导工程实践。

Experiment Study on the Permeability Evolution of Carbonate Rocks under the Coupling Effect of Stress Conditions and Aggressive Solutions

For the study of permeability evolution of carbonate rocks under different stress and solutions, H2SO4 solution and distilled water were used to conduct rock permeation experiment in rock permeability experimental system for a long time. The curves of carbonate permeability versus time and the variation of mineral ion concentration in leachate with time corresponding to the design conditions were obtained. The relationship among the law of permeability change, the law of mineral dissolution inside the rock, confining pressure, osmotic pressure, solutions and various influencing factors were analyzed. The results indicate that the significant changes in the permeability of carbonate rocks in early stage are caused by confining pressure, the constant confining pressure results in the shrinkage of pore structure inside rock sample and the seepage process is affected. The increase of osmotic pressure leads to a short rise in permeability of rock samples, then the permeability returns gradually. Different solutions have different effects. The dissolution of H2SO4 solution is relatively strong, and the upper reaches of the rock sample are strongly dissolved. When the dissolved mineral ion concentration reaches the supersaturation, the sediment may be precipitated at the downstream, the permeability of the sample decreases constantly; The corrosion effect of distilled water on rock sample is weak, and the dissolution is uniform along the seepage path. The pore structure changed slightly, and the overall permeability is stable. The whole change of rock permeability is the result of the joint action of stress conditions, the corrosion and mineral precipitation of the osmotic solution. The research results can be used to guide engineering practice.