氮气钻井圆弯管排放流量效率预测研究

Prediction Study on Discharge Flow Efficiency of Round Elbows in Nitrogen Drilling

在氮气钻井中,当钻遇高压高产气层,圆弯管的排放流量效率直接关系到整个钻井过程中的作业施工安全,而现场技术人员很难用试验来验证圆弯管的最大排放流量效率。针对上述问题,在计算流体动力学理论基础上,针对现场布局建立10寸圆弯管CFD模型,重点研究流量从20×10~4m^3/d突然增加到300×10~4m^3/d或500×10~4m^3/d时的流体在圆弯管中的流动状态,根据圆弯管内压以及管线所受的瞬时冲击作用力来预测圆弯管的最大排放流量效率。研究结果表明,圆弯管所受瞬时冲击力造成的轴向应力远远小于钢材强度240MPa,不会对圆弯管造成失效。而圆弯管承受的内压由于排放量的增加而逼近圆弯管的承压极限4MPa,预测得出此类排砂管线布局的圆弯管极限排放流量效率约500×10~4m^3/d。上述预测可对现场生产提供理论指导,保证氮气钻井安全。

In nitrogen drilling,when drilling in high pressure and high yield gas,the discharge flow efficiency of round elbows is directly related to the whole drilling operation in the process of construction safety.However,technicians in the field can hardly use experiment to verify the maximum discharge flow efficiency of round elbows.For the above problem,based on computational fluid dynamics,a CFD model of 10-inch round elbow is established according to the layout in well site.The flow state of gas in round elbow is studied when flow rate suddenly increases from 20 × 10^4 m^3/d to 300× 10^4 m^3/d and 500× l04 m^3/d,respectively.According to inner pressure distribution and instantaneous impact force,the maximum discharge flow of the round elbow is predicted.The results show that the axial stress caused by instantaneous impact force is far less than the steel strength 240MPa.With the increase of flow rate,inner pressure is approaching the burst limit （4MPa） of round elbow.The predicted discharge flow limit of round elbow is about 500×10^4 m^3/d.The proposed method can provide theoretical guidance on the safety of the nitrogen drilling.