基于新型粒子群算法的泵送射孔井口压力预测方法研究

Research on Pump Down Treating Pressure Prediction Based on New Particle Swarm Optimization Algorithm

泵送射孔施工广泛应用于页岩气储层水力压裂技术中,但目前缺少有关泵送射孔井口压力计算的研究。基于间隙流的伯努利方程,提出了泵送摩阻模型,结合沿程摩阻和射孔摩阻建立泵送射孔井口压力数学模型,采用新型粒子群算法与最小二乘法,建立基于射孔炮眼特征及裂缝压力的泵送射孔井口压力自动拟合方法,并通过分析某井连续4段泵送射孔施工数据进行方法验证。研究发现,提出的井口压力历史拟合方法的拟合均方误差为1.29,摩阻模型计算得到泵送射孔时炮眼摩阻、沿程摩阻与泵送摩阻比例约为17∶3∶1;泵送射孔与压裂施工结束时间间隔长时,裂缝压力、流量系数及炮眼开启数量降低,炮眼摩阻、泵送压力增加。提出的方法可以有效预测泵送射孔时的井口压力,同时泵送射孔与压裂施工间隔时间长时,井下裂缝已闭合,而时间间隔短时井下裂缝仍然开启。因此,为避免射孔泵送过程中,闭合裂缝突然张开导致的压力突降,推荐压裂后立即进行泵送射孔施工。建立的泵送射孔井口压力模型可以为泵送施工提供更准确的压力预测,对指导泵送射孔施工具有重要意义。

Pumping down plug-and-perf technique is widely used in shale gas reservoir hydraulic fracturing,but there is currently a lack of research on the calculation of pump down treating pressure.This paper proposes a pump down friction model based on the Bernoulli equation of interstitial flow,and establishes a mathematical model of pump down treating pressure based on drag friction and perforation friction,and further uses a new particle swarm algorithm and the least squares method to establish an automatic history matching method for pump down treating pressure.Finally,this method is verified based on the pump down data of four consecutive sections of a well.The study found that the fitting mean square error of the wellhead pressure history matching method proposed in this article is 1.29.The friction model calculation shows that the ratio of perforation friction,drag friction and pump down friction is about 17:3:1.When the time interval between pump down construction and the end of hydraulic fracturing construction is long,the fracture pressure,flow coefficient and number of perforations decrease,and the perforation friction and treating pressure increase.The results show that the method proposed in this article can effectively predict the treating pressure during pump down.At the same time,when the time interval between pump down and hydraulic fracturing construction is long,the hydraulic fractures have been closed,while when the time interval is short,the hudraulic fractures are still open.Therefore,in order to avoid a sudden pressure drop caused by the sudden opening of closed fractures during the pump down process,it is recommended to carry out pump down construction immediately after hydraulic fracturing.The pump down treating pressure model established in this article can provide more accurate pressure prediction for pump down construction,and is of great significance in guiding pump down construction.