多级交替注入酸压温度场数值模拟

深层碳酸盐岩油气藏在全球油气生产中占据着非常重要的地位，但是由于储层高温导致酸岩反应速度较快，酸蚀有效作用距离短，这严重影响到储层酸压改造的效果。多级注入酸压技术通过交替注入低温的前置液与酸液，持续对储层进行降温，并形成酸液在前置液中指进的现象，大大提高了酸液有效作用距离，因此被广泛应用于现场。为探究交替注入酸压温度场与作用距离的关系以及不同参数对温度场的影响规律，基于有限元方法利用VOF模型和UDF方法模拟了交替注入的酸压温度场，分析了注入速度、黏度比及酸岩反应热对缝内温度场的影响并且优化了4级注入时酸液和前置液的用量比。结果表明，注入速度越大，裂缝壁面温度越低，液体对地层的降温作用越明显，速度提高2倍时，平均壁面温度下降幅度增加35.76%；黏度比越大，裂缝壁面温度越低，黏度比提高1.5倍时，平均壁面温度下降幅度增加5.18%；酸岩反应热越小，裂缝壁面温度越低，酸岩反应热每增加10 KJ/mol时，平均壁面温度下降幅度减少13.26%。从深层储层降温的角度，建议选择酸液与前置液用量比为0.8~0.9，以递减的方式注入，为交替注入施工参数优化提供了一种新思路。

Numerical Simulation of Temperature Field of Multistage Alternative Acid Fracturing

Deep carbonate reservoir plays a significant role in global oil and gas production. However, due to the high temperature, the acid-rock reaction speed is fast and the effective distance of acid etching is short, which seriously affects the effect of acid fracturing. The multistage alternative acid fracturing technology cool the reservoir continuously by injecting low-temperature pre-fluid and acid alternately. Otherwise, the phenomenon of acid advancing in the pre-fluid improves the effective distance of acid greatly. Therefore, it is widely used in the field. To verify the relationship between the temperature field and effective distance, and the influence of different parameters on the temperature field, the temperature field of multistage alternative acid fracturing was simulated by the VOF model and UDF method of the finite element method. The effects of injection velocity, viscosity ratio and acid-rock reaction heat on the temperature field in the fracture were analyzed, and the dosage ratio of acid and pre-fluid was optimized for 4rd injection round. The results indicate that the higher the injection velocity is, the lower the crack wall temperature is, and the more obvious the liquid cooling effect on the formation is. When the injection velocity increases by 2 times, the average wall temperature decreases by 35.76%. The larger the viscosity ratio is, the lower the crack wall temperature is. When the viscosity ratio increases by 1.5 times, the average wall temperature decreases by 5.18%. The smaller the reaction heat of acid-rock is, the lower the crack wall temperature is. When the reaction heat of acid-rock increases by 10 KJ/mol, the average wall temperature decreases by 13.26%. From the perspective of cooling deep carbonate reservoir, it is suggested that the dosage ratio of acid and pre-fluid is 0.8~0.9, and injection in a decreasing way, which provides a new idea for the optimization of construction parameters of alternative injection.