Research on thermal behavior of ultra-deep horizontal well drilling with dual-channel drillpipe

The ultra-high temperature characteristics of ultra-deep formation pose a serious threat to the safety and efficiency of drilling. In this paper, we proposed a novel method of dual-channel drillpipe for drilling ultra-deep formation. A transient heat transfer model of dual-channel drillpipe drilling was established considering the different heat transfer mechanisms of different regions, combined with technological characteristics of dualchannel drillpipe drilling as well as the variable mass flow of fluid at the dual-channel valve. The validity of the model has been indirectly verified by the measured temperatures of a real case. Numerical simulation results showed that, compared with conventional drilling method, the dual-channel drillpipe drilling could reduce the bottom hole pressure to lower extent and reached a stable state in shorter time. Meanwhile, the insulation effect of the auxiliary fluid could slow down the reduction in the temperature of injected drilling fluid and the increase in the temperature of the returned fluid above the dual-channel valve. Furthermore, the formation transferred less heat to the wellbore than conventional drilling. Therefore, dual-channel drillpipe drilling has the potential to become an effective method for drilling in ultra-deep formation at ultra-high temperature.