砂岩基质酸化中酸岩反应数学模型

Acid/sandstone reaction modeling for sandstone-matrix acidizing

建立了砂岩基质酸化时酸液沿井筒径向流动以及关井反应的数学模型,考虑温度对反应速度的影响,进行了数值求解,研究了酸岩反应规律,可以对酸化效果进行预测.计算结果表明:沿井筒径向HF酸浓度下降很快,其作用范围只有0.4m左右;次生H2SiF6与HF的溶解能力相当,并且是HF的有益补充,0.4～0.9m范围内快速反应矿物的消耗主要是由H2SiF6溶解,增加了土酸的穿透深度;硅胶Si(OH)4沉淀随着反应时间的增长而逐渐增加,酸化结束后一定时间内残酸必须彻底返排,否则容易形成2次沉淀,影响酸化效果;地层温度越高HF酸消耗越快,有效作用距离越短,生成的硅胶Si(OH)4浓度越大;提高注酸速度有利于提高酸化穿透距离,解除地层深部伤害.

Mathematical models for acid injection and shut-in reaction periods were established during acidization of sandstone-matrix by considering the effect of temperature on reaction rate. The models were solved by numerical method, and the reaction between acid and sandstone was studied. The results can predict the effect of the acid/sandstone reaction. The calculation re- sults show that the concentration of HF decreased quickly during the acidization of sandstone- matrix in radical direction with HF operating range of less than 0.4 m. The dissolving capacity of the secondary H2 SiF6 was equal to HF, which is a beneficial complement for HF. Rapid re- action mineral in the range of 0.4 to 0.9 m is mainly dissolved by Hz SiF6. It increases acidizing penetration depth. The deposition of Si（OH）4 increases with time, but a flowback of the reac- ted acid is needed after the reaction for some time, otherwise secondary precipitation will oc- cur, which affects the acidization of sandstone-matrix. The rate of HF consumption increases with the formation temperature, which reduces the operating range of HF. The concentration