组合射流PDC钻头试验研究

为了将不同射流方式应用于PDC钻头以改变井底流场,并给钻头提供设计依据,通过数值模拟和室内试验分析了反向射流对井底流场的影响规律,并对旋转射流的破岩能力进行了评价。结果表明:PDC钻头加装反向射流喷嘴之后,钻头破岩部位压力降低,并且压降随着反向射流喷嘴距钻头底部距离的增大而减小,随反向射流流量的增大而增大,上部钻井液液柱压力对压降影响不大;在相同压降或排量下,旋转射流较普通直射流有更好的破岩能力。根据试验结论研制出了反向射流与旋转射流组合的PDC钻头,并在坨747井进行现场试验。结果表明,坨747井采用组合射流PDC钻头后,与采用普通PDC钻头的邻井相比,钻速提高40%以上。这表明,将反向射流和旋转射流组合应用于PDC钻头,可以明显提高机械钻速。 

Experimental Study of Combined-Jet PDC Bit

In order to apply different jet modes to PDC bits,numerical simulation and laboratory tests had been done to study the bottom-hole flow field affected by reverse jet.Rock breaking ability of swirling jet in the laboratory was evaluated,which could provide basis for bit design.The results showed that obvious pressure declined at rock breaking with backward jet nozzles on PDC.As the distance between reverse jet nozzle outlet and bit bottom decreased,and reverse flow rate increased and the degree of pressure drop increases at bottom holes.The pressure of drilling fluid column pressure had little effect on the pressure drop.Compared with conventional jet,swirling jet had better rock breaking ability at the same pressure drop and flow rate.According to the test results,a new combined-jet PDC bit,joining reverse jet and swirling jet,was developed and used on Well Tuo 747.The test results showed that it could improve ROP by more than 40% compared with the neighboring wells using conventional PDC bits.It was proved that the combination of reverse jet and swirling jet on PDC bit can improve ROP remarkably.