钻遇多压力系统气层溢漏同存规律研究

Research on well kick accompanied with lost circulation during drilling of gas formation with multi-pressure system

钻遇多压力系统气层,多个不同地层压力系数的漏层、喷层常同存于一个裸眼中,钻进过程极易发生溢漏同存的复杂情况。目前国内外对多压力系统气层溢漏同存的研究,往往局限于现场堵漏压井处理工艺技术。文中阐述了多压力系统气层溢漏同存时的物理规律,并根据井筒环空多相流的理论建立了数学模型,系统总结了气液两相流型转换准则和不同流型的压降计算公式,得出了不同工况下多压力系统气层溢漏同存时的井筒环空压力曲线,以及气液两相流型沿井深的分布。计算结果表明:溢漏同存时井筒环空压力迅速下降,溢流态势更加严重;井筒环空的液体流量急剧减少,气体迅速向上滑脱和运移,导致气液两相流型分布变化较大,模拟结果对现场溢漏同存处理技术具有重要的指导意义。

The complex situation of well kick accompanied with lost circulation is very prone to happen during drilling the gas formation with multi-pressure system because many leakage zones and overflow zones with different formation pressure coefficient are always in a bare hole.The domestic and overseas researches on well kick accompanied with lost circulation are often confined to the treatment technologies of sealing and killing well at present.This paper elaborates the physical law and establishes the mathematical model of well kick accompanied with lost circulation on the basis of the annulus multi-phase flow.The transition criteria and pressure drop model of gas-liquid flow are systematically summarized and then the annulus pressure curves and the pattern distribution of gas-liquid flow along the well depth are obtained.Calculation result indicates that wellbore annulus pressure drops quickly and well kick is more serious.Annulus liquid flow rates reduce sharply and gases slip and migrate upward rapidly,resulting in the large transform of distribution pattern of gas-liquid flow.Simulation results have important guiding significance to field treatment technologies of well kick accompanied with lost circulation during drilling the gas formation with multi-pressure system.