定量计算酸预处理降低破裂压力模型研究

酸化预处理是降低地层破裂压力行之有效的方法。对于特定地层，预处理酸液类型、酸液浓度、用酸强度及酸化后储层破裂压力降低程度往往依赖于经验，亟需理论指导。通过分析酸化引起的岩石力学性质变化，建立砂岩酸化损伤模型，在此基础上定量计算了酸化后破裂压力值。通过现场2口井酸化前后的破裂压力降低值与模拟计算结果对比认为：所建模型合理，可以用于指导现场酸化施工，降低施工风险。研究对于推动深层储层水力压裂理论的发展具有重要意义和参考价值。

QUANTITATIVE CALCULATION MODEL OF DECREASING FRACTURE PRESSURE AFTER ACID PRETREATMENT

Whether wellhead Construction pressure could be effectively reduced is the bottleneck of restricting the safe and efficient development of deep tight or ultradeep reservoir with abnormal fracture pressure. Acid pretreatment is an effective method of decreasing formation fracture pressure. But for a specific formation, acid type, acid concentration, acid strength of acid pretreatment and how much the fracture pressure can be reduced after acid pretreatment often depend on experience, and theoretical guidance is badly required. In this paper, a sandstone acid injury model is established through analysis of changes in rock mechanical properties caused by acid pretreatment, and the value of fracture pressure is quantitatively calculated after acidification on the basis of the injury model. Through the comparison of the decreased fracture pressure of two wells before and after the acidification and the simulation results, the model can be regarded as to be reasonable and can be used to guide the onsite acidzing operation, decrease operation risks. This study has important significance and reference value for promoting theoretic development of hydraulic fracturing in deep reservoir.