【作者】 艾飞；

【导师】 王瑞和；

【作者基本信息】 中国石油大学 ， 油气井工程， 2007， 硕士

【摘要】 优化井底水力特性是提高钻井速度的有效途径之一,基于这种认识,对旋转射流的结构特性进行了深入剖析,提出了将旋转射流引入到PDC钻头的技术设想,并采用理论分析和试验研究的方法探索了旋流PDC钻头井底流场辅助提高钻井速度的机制,为相关的实际应用寻求理论支持。首先,在分析旋转射流结构特性的基础上,基于较少假设,采用重整化群RNG k ?ε模型,对旋流PDC钻头井底流场进行数值模拟,结果发现,旋转射流和直射流的配合比常规的直射流可获得更大的漫流速度,有利于清除井底岩屑;钻头外围喷嘴采用旋流喷嘴时,可获得更好的清岩效果;钻头旋转和喷嘴旋转射流联合作用,会在井底形成有序的高压区和低压区分布,改善井底岩石和岩屑的受力状况,从而提高钻井速度。其次,开展了切向注入式旋流喷嘴的携岩实验,结果表明,切向注入式旋流喷嘴的携岩能力优于直射流喷嘴;随着喷距的增加,喷嘴携岩能力呈先增大后减小的趋势,本文实验条件下的最佳携岩喷距为(1-3)L/d;当切入孔个数为3个时,携砂量最大,是同样条件下直射流喷嘴携岩量的1.5倍。最后,依据理论分析和实验研究结果,以易于实现、可靠性高为主体技术思路,设计了切向注入喷嘴式旋流PDC钻头和钻头腔内定子调制式旋流PDC钻头,并探讨了实际应用的可行性。系统的理论分析和试验研究证实,调制井底旋转射流,优化井底水力特性确实有利于提高钻井速度,研究结果对新型、高效破岩工具的研制和应用具有重要的实际意义。更多还原

【Abstract】 Considering the fault of the traditional PDC bit, we import Swirl jet into PDC bit. On the basis of theoretical analysis to the stress of the rock and cuttings on the bottom hole, we simulate the flow field of swirl jet PDC bit and do experiment for testing the cuttings carrying capacity.In accord to the theoretical analysis of rock stress state in the bottom hole, cuttings actuation mechanism and the hypothesis that swirl jet make local low pressure in the bottom hole, the pressure difference between high and low pressure district can be used with the periodical actuation to bottom hole and ordinal swirl flow formed by it for decreasing rock strength, intensifying cuttings actuation, purifying and enhance drilling speed. The renormalization group RNG model is adopted, the results of the numerical simulation of swirl jet PDC bit’s flow field in the bottom hole which take the affection of PDC bit crown structure and cogging into account show that straight jet cooperating with swirl jet can be more valuable in cuttings carrying than common straight jet, bottom hole swirl jet formed by heterogeneity of bottom hole flow field and bit’s rotation develop the bottom hole swirl flow field which is useful for cuttings carrying and form ordinal distribution of high and low pressure district, improve stress station of rock or cuttings and enhance drilling speed. On detailed analysis, the main function of the nozzle near bit axle is carrying the cuttings away from broken surface while far from bit axle is carrying cuttings into annual, so the nozzle far from bit axle can be replaced by swirl nozzle in order to enhance the efficiency of cuttings cleaning.The result of cuttings carrying experiment of tangential injection swirl nozzle indicated that tangential injection swirl nozzle has stronger ability in cuttings carrying than common straight nozzle, with the same pump pressure and increase of jet distance, nozzle’s cuttings carrying ability increase and then decrease, there exists the optimum jet distance. The optimum jet distance of this paper is 1-3 L/d. Tangential injection bore’s nozzle with uneven number has stronger ability than that with even number in cuttings carrying and there exists the optimum number of tangential injection bore. Result showed that the optimum bore number is 3 and the ability of cuttings carrying is 1.5times stronger than common straight nozzle.On the basis of conclusion above, tangential injection swirl jet PDC bit and the conception of stator modulation swirl jet PDC bit have been proposed and developed. This job can be valuable for enhancing drilling speed.更多还原