高效岩屑床清除钻杆作用机理

岩屑携带困难是大斜度、大位移定向井和水平井钻井普遍存在的问题，严重影响钻井安全和钻进效果。设计了高效岩屑床清除钻杆（EHCDP），并利用计算流体动力学(CFD)仿真模拟技术对EHCDP作用下环空流场的流动特性展开研究，从流线图、速度场、压力场等方面对数值模拟结果进行了分析，研究了EHCDP的作用机理，分析了螺旋槽道结构对环空流体流动特性的影响。研究结果表明，在EHCDP作用下，流体在槽道附近形成了涡流结构，改变了偏心环空中流体的流动特性，使流体从小环空往大环空运动，将岩屑输送到大环空，而槽道附近的涡则将岩屑卷入槽道中，并利用钻杆转动所产生的离心力将岩屑“甩入”大环空，达到有效清除井眼低边岩屑床的目的。

Mechanism of an effective hydroclean drill pipe for hole cleaning

The difficulty in carrying cuttings is a universal problem encountered in drilling of highly deviated and extended reach directional wells or horizontal wells,and it significantly affects the safety and efficiency of drilling operation.We developed an effective hydroclean drill pipe(EHCDP) and studied flow behaviors of the annulus flow field with EHCDP by applying a realistic model technique of the computational fluid dynamics(CFD).Numerical simulation data were analyzed in terms of flow diagrams,velocity field,and pressure field,and the EHCDP mechanism was studied by examining the effect of a spiral groove structure on flow behaviors of the annulus fluid.The results show that fluid can form a vortex cavity near spiral grooves with EHCDP,which can effectively change flow behaviors of fluid in an eccentric annulus,resulting in the annulus fluid to move from the low-side of an annulus to the up-side of that,which will transport cuttings to the up-side of an annulus as well.In addition,the vortex near grooves will swirl cuttings into spiral grooves,then cuttings will be thrown into the up-side of an annulus with centrifugal force produced by rotation of a drill pipe,therefore,cuttings beds at the bottom hole can be effectively removed.