压裂过程中孔眼摩阻计算的改进模型及应用

MODIFIED MODEL AND APPLICATION OF CALCULATING PERFORATION PRESSURE LOSS DURING HYDRAULIC FRACTURING

在低渗透油气藏的加砂压裂施工中,经常出现实际井口施工压力比设计方案所预测的压力偏高,这很大程度上归因于井筒和裂缝间的连通性差,引起井筒和裂缝间的压力损失过大。孔眼摩阻计算的准确程度直接影响破裂压力的预测,裂缝扩展的几何形态,更是限流压裂的关键参数,对压裂施工的顺利实施和压后评估有重要的影响。文章在研究分析了目前孔眼摩阻计算公式适用性的基础上,提出了考虑不同压裂液类型、粘度、排量、砂浓度、孔眼直径等参数影响下孔眼摩阻的改进模型和算法。通过5 口压裂井应用结果表明,此模型和算法与实际更吻合且易于现场应用。

It happens usually the actual pump pressure is a little higher than that predicted in the design program when sand fracturing of low permeability reservoirs, which is mainly contributed from the extreme pressure loss caused by the poor connection between the borehole and the fractures. The accuracy of calculating perforation pressure loss influences the prediction of the cracking pressure as well as the geometrical configuration of fracture extending directly. Also, the perforation pressure loss is the key parameter of the limited-entry fracturing, which will affect the fracturing job and the evaluation after fracturing. Based on the analysis of the current calculating formula, the modified model and the calculation method are developed considering the influence of different parameters such as fracturing liquid type, viscosity, flow rate, sand concentration, perforation diameter, etc. The application results in 5 fractured wells show the modified model and the calculation method couple with the real situation more and are prone to the field application.