深水大尺寸井眼钻进钻井液双循环携岩方法

Method of double drilling fluid circulation for cuttings carrying in large-size wellbore during deepwater drilling

深水大尺寸井眼提高泵排量钻进时,易导致钻井液循环压耗增加、泵功率利用率低和井底压力增加等问题,提出一种通过在井筒变径处钻杆上安装分流短节,实现钻井液双循环的方法,基于钻井水力参数优化理论和数值模拟方法,研究分流短节对井筒变径处环空钻井液返速、钻井水力参数和钻杆结构安全性的影响。结果表明安装分流短节后井筒变径段环空钻井液的返速有明显提升;当分流喷嘴直径为14 mm时携岩效果最好;增大泵排量后,与未安装分流短节的常规钻井方法相比,分流短节不仅能有效提升井筒变径段环空钻井液返速,还可以降低钻井泵大排量引起的循环压耗;合理的结构设计可确保钻杆钻进的安全性;所得结论可为深水大尺寸井眼高效、安全钻进提供参考。

The application of large-size boreholein deepwater drilling can cause increase of circulating pressure loss of drilling fluid low utilization efficiency of pump power and increase of bottom hole pressure due to the increase of pump displacement.To mitigate this problem,a method using double drilling fluid circulation was proposed by installing a short shunt tube on the drill-pipe at where with large wellbore diameter.The effects of the short shunt circulation on the annular drilling fluid return rate,drilling hydraulic parameters and the structural safety of the drillpipe were investigated,based on drilling hydraulic parameter optimization theory and numerical simulation methods.The results show that the short shunt can significantly improve the return rate of drilling fluid in wellbore with variable cross-sections.When the diameter of the shunt nozzle is 14 mm,the cuttings carrying efficiency can be maximized using the double circulation.In comparison with the conventional method without installing the short shunt,the short shunt can not only increase the return rate of annular drilling fluid,but also reduce the circulating pressure loss caused by large pump discharges.Adopting a reasonable structure design of the shunt tube can ensure the safety of the drillpipein drilling.