井下涡流排液采气井筒临界携液量计算

CALCULATION OF THE CRITICAL LIQUID CARRY-OVER IN THE WELLBORE FOR DOWNHOLE VORTEX DEWATERING GAS RECOVERY

井下涡流排液采气是一项新技术,目前缺乏对井筒涡流场临界携液流量的理论研究。根据两相流体动力学理论,对井筒涡流场中的液滴进行受力分析,得到液滴沿轴向和径向的运动方程,然后通过量级比较,忽略虚拟质量力和Basset力,建立简化的液滴垂向受力平衡方程,推导出涡流场临界携液流速与流量公式。现场实例分析表明:理论计算的涡流场临界携液流量比常规流场的临界携液流量平均降低26.4%;随着螺旋角增大,临界携液流量先增大后减小,存在一个使临界携液流量最小的螺旋角。井下涡流排液技术可使临界携液流量大幅降低,有效提高气井携液能力,排除井筒积液。

Downhole vortex dewatering gas recovery is one of the new techniques. However,at present,the theoretical researches on the critical liquid carry-over in the wellbore vortex field are still absent. According to the theory of two-phase fluid dynamics,the force analysis was conducted for the liquid droplets in the wellbore vortex field,and then the axial and radical equations of the motion were established. With the help of the magnitude comparison and neglecting the mutual mass force and Basset force,the simplified vertical force equilibrium equation was established,finally the equations of the critical liquid carry-over velocity and flow rate were deduced. The field case analysis shows that comparing with the calculated critical liquid carry-over in the general wellbore flow field,the corresponding liquid carry-over in the vortex flow field by means of the theoretical calculation is decreased averagely by26. 4%; with the rise of the helical angle,the critical liquid carry-over increases at first then decreases,there exits the minimal helical angle which can minimized the liquid carry-over. The downhole vortex liquid-discharging technique can decrease the critical liquid carry-over to a great deal,thus the fluid-carrying capability of the gas well can be effectively improved,and furthermore the borehole liquid loading can be discharged.