【作者】 孙伟良；

【导师】 杨永印；

【作者基本信息】 中国石油大学 ， 油气井工程， 2010， 硕士

【摘要】 深井、超深井钻进过程中,机械钻速随井深增加明显下降。重要原因之一是由于井底压差的增大,岩屑不能及时清除,造成钻头的重复破碎,致使机械钻速迅速下降。从井底压差影响钻速的基本原理看,通过钻头分流降低井底压差,能起到减小“压持效应”,提高机械钻速的作用。通过理论分析,应用数值模拟方法,改变分流喷嘴、钻头体流道等结构参数和水力参数,分析井底围压、钻头体流道结构、喷嘴与喉管直径、分流流量比、分流喷嘴距井底的位置、钻头与井壁的间隙等各因素对钻头分流降低井底压力的影响规律,无因次压降最大可达到0.26。应用附壁式双稳射流元件进行协调式脉动分流,无因次压降可达0.5,降压效果优于连续性分流。根据数值模拟所用的钻头及井筒模型设计实验工具进行实验,分析围压、分流流量比、分流喷嘴距井底的位置、钻头与井壁的间隙等各因素对分流降压效果的影响,无因次压降最大可达到0.35,实验结论与数值模拟结果相一致。最后,应用PDC钻头设计软件,结合数值模拟和室内实验的结论,进行分流钻头结构和水力参数设计,为新型高效钻头的进一步研发奠定了基础。更多还原

【Abstract】 Penetration rate decreased obviously with the depth increased while drilling deep well and ultra deep well. Bottom hole pressure is one of the main factors affecting the drilling speed, cuttings can’t be cleared in time, causing duplication of broken rock, caused the rapid decline in ROP.In view of the basic principles of influence on ROP , reducing the bottom hole pressure by fluid shunt on bit can significantly reduce the“chip hold down effect”and increase drilling speed.Based on theoretical analysis, chang the structural parameters and hydraulic parameters of nozzle and bit flow structure to simulate the bottom flow field .Analyse of bottom hole confining pressure, flow structure of the bit , nozzle and pipe diameter, shunt flow ratio, the nozzle position, the gap of bit and hole ,and other factors on the effect of reducing the bottom hole pressure by fluid shunt, dimensionless pressure drop can reach 0.26 greatly. Attached to the wall bistable jet element is applicated to coordinate pulse jet, dimensionless pressure drop can reach 0.5,the effect of pressure drop is better than continuous shunt. Based on the simulation of the drill bit and wellbore model experimenta tools to experiment, and analyse confining pressure, shunt flow ratio, the position of nozzle , the gap of bit and hole, and other factors on the effect of reducing bottom hole pressure by fluid shunt, dimensionless pressure drop can reach 0.35.The conclusion is consistent with the numerical results. Finally, using PDC bit design software, combined with numerical simulations and laboratory conclusion to design the bit and hydraulic structure, and lay the foundation for the development of the new and high efficiency drill bit.更多还原