Abstract: Plunger lift has been the key technology of liquid flowback after fracking in shale gas reservoirs. In order to enhance the seal effect of fluid lift with solid plunger, the Fluent software was employed to set up the two-dimensional geometric model with a single flow channel, and turbulent flow model was adopted to simulate the flow field condition of groove with movement of solid plunger. Based on optimizing the shapes of groove (straight angle trapezoid groove, isosceles trapezoid groove, inverse isosceles trapezoid groove, inverse right angle trapezoid groove, and rectangular groove), this paper contrasts and analyzes the flow field condition with different groove width and depth, and then carries out the physical simulation experiment to contrast the dual pad plunger commonly and optimized solid plunger. Based on the above numerical simulations and experiments, we conclude that there is a low speed zone in the center of the groove when the plunger running, in which eddies appear constantly and interfere with the normal flow of the fluid. In that case, the flow rate is reduced to achieve the sealing effect. Through the comparison of groove type, it can be seen that the seal effect of trapezoidal groove with straight angle is the best. Accounting to the common situation on site, with wider and deeper groove, the sealing effect would be better (the performance of groove with the width as 20 mm and the depth as 6 mm is much better than the others'). Physical simulation experiment proved that under the same condition of low gas velocity, the liquid lifting effect of rod plunger is better than that of liner plunger. In this study, a reliable physical model was established in combination with CFD, and the optimized solid plunger had a good lift effect, which could guide the field application.

Key words: solid plunger, removing liquid, seal, Fluent, groove, turbulence