一种脉冲射流工具的携岩仿真研究

川南地区的大中斜度页岩气井因地层结构，在钻进过程中产生的岩屑极易沉积为岩屑床，使得钻杆摩阻增大，最终还会造成钻具断裂等重大井下事故。为了减少岩屑床的生成并提高井眼清洁度，提出一种新型脉冲射流工具，该工具既可以减少岩屑沉降，还可以破坏已存在的岩屑床。利用仿真分析软件ANSYS建立了新型脉冲射流工具与普通携岩钻杆的仿真模型，利用CFD-DEM(离散单元法)耦合对二者进行精确仿真，在改变岩屑粒径、钻井液密度、入口排量、井斜角等因素下，对比分析新型脉冲射流工具与普通携岩钻杆的岩屑运移能力。最终得出新型脉冲射流工具相比普通携岩钻杆可以更好地提高岩屑运移能力（利用脉冲高速流体对已沉降的岩屑进行搅动），并且其脉冲射流还可以破坏已存在的岩屑床的结论。该研究成果对减少井眼环空内岩屑总质量与提高钻井经济效益具有重要意义。

Simulation Analysis of Rock Carrying of a New Pulsed Jet Tool

Due to the formation structure of large and medium slope shale gas wells in southern Sichuan, the cuttings produced in drilling process are easily deposited as cuttings beds, which increases the friction resistance of drill pipe and eventually leads to major downhole accidents such as drilling tool fracture.In order to reduce the generation of cuttings bed and improve well cleanliness, a new type of pulse jet tool was put forward.This tool could be used to improve debris settlement, and damage the cuttings beds directly.The simulation software ANSYS was used to establish the simulation models of the new pulse jet tools and the common cuttings carrying drill pipe. CFD-DEM coupling was used to make precise simulation,the cuttings migration capacities within the annulus of the new tool and common drill pipe were contrasted through changing the cuttings diameter, drilling fluid density,entrance displacement and hole inclination angle.It is concluded that compare with the common drill pipe,the new pulse jet has better cuttings migration ability (smaller total cuttings in the annulus after stable quality),and the directional jet not only can destroy the existing cuttings bed, but also can prevent the formation of cuttings bed.The results of the study are of great significance on reducing total quality in borehole annulus and improving economic efficiency of drilling cuttings.