井下喷射孔结构压降计算中流量系数的探讨

石油钻采工程中有大量喷嘴、射孔孔眼等喷射孔结构，在复杂工程流体下，其喷射压降计算流量系数选取范围大，严重影响工艺设计和施工安全。为此，基于钻采、压裂和套管射孔中常见的喷射孔结构压降计算公式，分析了影响喷射孔压降计算的主要因素，采用数值模拟方法，得出了圆锥、圆弧带圆柱出口的喷射孔结构流量系数计算公式，并考虑流体物性对流量系数的影响，给出了流量系数的统一计算公式。经实验和数值仿真计算，验证了该流量系数公式的可靠性，为石油钻采工程中喷嘴、射孔孔眼等喷射孔结构的压降计算提供了理论依据。

Discussion on flow rate coefficient used for the calculation of downhole jet orifice pressure drop

Jet orifices (e.g.nozzle and perforation) are abundantly applied in petroleum drilling and production engineering.In the case of complex engineering fluid, the flow rate coefficient calculated from jet pressure drop is selected in the large range, so technological design and construction safety are impacted seriously.In this paper, the main factors influencing the calculation of jet orifice pressure drop were analyzed based on the calculation formula of jet orifice pressure drop which is commonly used for drilling, production, fracturing and casing perforation.Then, the formula for calculating the flow rate coefficient of jet orifice at cylinder outlet of taper or arc belt was established by means of numerical simulation.Finally, the identical calculation formula of flow rate coefficient was provided by taking into consideration the effects of physical properties on flow rate coefficient of fluids.And its reliability was verified by virtue of experiments and numerical simulation.It provides the theoretical basis for calculating the pressure drop of jet orifices (e.g.nozzle and perforation) in oil drilling and production engineering.