碳酸盐岩酸化压裂力学性质劣化效应试验

Experiments on the Deterioration Effects of Carbonate During Acid Fracturing

为了模拟井下压裂作用下胶凝酸和清洁酸作用时的碳酸盐岩破裂机制,了解两种酸液体系作用后的强度劣化效应,进行了拟三轴岩石力学试验以及3-D扫描。试验结果表明:与胶凝酸反应后,碳酸盐岩弹性模量、泊松比和抗压强度均呈降低趋势,其中泊松比降低幅度明显,酸蚀90 min时,降幅达到18.15%;与清洁酸反应后,碳酸盐岩弹性模量、抗压强度在酸蚀初始阶段小幅提高,当酸蚀时间达到90 min后,两者降幅分别为21.04%及23.55%,泊松比降幅为4.36%,岩石力学性质劣化效应明显,脆性指数升高12.09%;与胶凝酸反应90 min后,碳酸盐岩的脆性指数提高58.56%,破裂压力呈下降趋势;与清洁酸反应后,裂缝壁面粗糙程度明显降低,裂缝导流能力呈降低趋势。酸压后的力学性质劣化特征可为酸化压裂设计及参数优化提供基础数据。

In order to simulate the fracture mechanism of carbonate rock under the action of gelling acid and clean acid under the condition of downhole fracturing,the effects of strength degradation after the action of two acid systems were studied,and the pseudo-triaxial rock mechanics test and 3-D scanning were carried out.The experimental results show that the elastic modulus,Poisson’s ratio and compressive strength of carbonate rock decrease with the reaction of gelling acid,and the Poisson’s ratio decreases obviously.When the acid etching is 90 min,the decrease reaches 18.15%.After reacting with the clean acid,the elastic modulus and compressive strength of the carbonate rock increase slightly in the initial stage of acid etching.When the acid etching time reaches 90 min,the reduction is significantly reduced by 21.04%and 23.55%,respectively.For 4.36%,the degradation effect of rock mechanics is obvious,the brittleness index increases by 12.09%;after reacting with gelling acid for 90 min,the brittleness index of carbonate rock increases by 58.56%,and the fracture pressure shows a downward trend;after reacting with clean acid The roughness of the crack wall is significantly reduced,and the fracture conductivity is reduced.The deterioration of mechanical properties after acid pressure can provide basic data for acid fracturing design and parameter optimization.