双循环钻井携岩系统CFD-DEM仿真及工具优化

摘要

To further improve the drilling efficiency of double-circulation drilling technology in CBM drilling, a double-circulation whole well simulation model has been established based on the particle motion equation and Hertz-Mindlin contact model.CFD-DEM coupled model was used to show the double-circulation drilling technology and demonstrate the mechanism of the assistant circulation.The assistant circulation nozzle was optimized according to the simulation results.The results show that the combined effect of the double circulation system is significant for the improvement of the cutting carrying performance with the positive effect of assistant circulation.The double circulation system could provide the best cutting carrying capacity and the assistant circulation has the best effort under the nozzle angle of 40°±10°.The study results could provide references for the field application of double circulation drilling system.%为了进一步提高双循环钻井技术在煤层气钻井中的钻进效率,在介绍颗粒运动方程及Hertz-Mindlin接触模型的基础上,建立了双循环全井仿真模型,利用CFD-DEM耦合模型对双循环钻井技术进行了再现,展示了辅助循环的作用机理,并依据仿真结果对辅助循环喷嘴进行了优化.分析结果表明:双循环系统的共同作用对携岩效果的改善非常明显,辅助循环对改善钻井携岩效果具有正作用,喷嘴入射角度在40°±10°范围时双循环系统携岩效果最好,辅助循环工作效果最佳.所得结论可为双循环钻井系统的现场应用提供参考.