| In the current large-scale development and application of highly-deviated wells and horizontal wells in China,hole cleaning has received a lot of attention and research as a problem affecting drilling and increasing potential safety risks.Among them,the spiral flow generator,as a tool to change the flow field state through physical form to overcome the formation of cuttings bed,has great research value in the field of wellbore cleaning.When the drill pipe is stationary,the influence factors and working mechanism of the spiral flow generator on the annulus flow field and bottom cuttings bed are not clear.Therefore,it is of great significance to analyze the influence law of the spiral flow generator on the horizontal well annulus flow field and bottom cuttings bed when the drill pipe is stationary,and to analyze its operation mechanism,and design a new tool structure with stronger purification effect.Based on literature research,by analyzing the influence of spiral flow on cuttings particles,the geometric physical model of spiral flow generator in horizontal wellbore was established,the three-dimensional transient numerical simulation of two-phase flow was carried out.It also reveals the vortex flow and rock-carrying characteristics produced by the spiral flow generators with spiral and V-shaped blades.According to the simulation results,particle Reynolds number Re_p and the established Intensity of Swirl Flow Pulsation(ISFP)have been analized to discuss the hydrodynamic mechanism of the spiral flow to remove the cuttings bed.According to the swirling function of the spiral flow generator,the Swirling Index of Tool(SIT),which characterizes the influence of structural parameters,was established and used to analyze and evaluate the influence of the spiral flow generator on the spiral flow.The numerical simulation results show that in the spiral flow field,the cuttings are mainly concentrated on the lower edge of the shaft wall in the cross section,and the concentration of cuttings particles decreases rapidly at a certain height from the lower edge of the shaft wall.The particle Reynolds number Re_p also peaks at a certain height from the lower edge of the well wall,and the ISFP gradually increases with the radial height,both of which are related to the concentration distribution of cuttings particles.At the same time,it is concluded that within the axial flow distance of the spiral flow field within 6 times the borehole diameter(d_o),the overall accumulation height of the cuttings in the lower edge of the shaft wall in the flow field model of the spiral and V-shaped tool is significantly lower than that of the pure drill Rod model,spiral flow can remove and purify cuttings bed within a certain distance.By comparison,the spiral flow generator of the V-shaped blade has greater flow resistance than the spiral blade tool,and the swirl effect is also poor.The axial action distance of the spiral flow on the cuttings bed can be judged by Re_p.According to the change of Re_p value and ISFP value,the influence of spiral structure parameters is obtained.When the SIT of the spiral flow generator is near 0.4,the ability of the spiral flow to remove the cuttings bed is more prominent.For the 215.9 mm wellbore,when the outer diameter of the blade is 188 mm and the spiral angle is 40°(SIT=0.395),the swirling flow has the best purification effect on the rock cutting bed,and the maximum effective distance is12d_o. |
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