塔中奥陶系碳酸盐岩地层漏失压力统计分析

塔中Ⅰ号坡折带奥陶系碳酸盐岩段在钻井施工时常遇到不同程度的井漏,确定漏失层段的漏失压力是防漏堵漏的依据。通过对奥陶系碳酸盐岩地层漏失井漏失的井深分布、工况、井漏发生率、漏失通道进行统计分析,表明奥陶系碳酸盐岩裂缝和溶洞发育、钻井过程中激动压力过大与地层压力敏感是引起井漏的主要原因。依据漏失压差与漏失速度分布规律,建立了相应的启裂压力模型,确定了地层漏失压力当量密度的计算方法,计算结果与实际情况相符,为防漏堵漏提供了依据。

Statistic analysis of leakage pressure of Ordovician carbonate formation in middle Tarim Basin

While drilling,well leakage often occurs in the Ordovician carbonate formation of No.1 slope-break zone in middle Tarim Basin.So it is vital to determine the leakage pressure to prevent leakage.Based on the statistic analysis of leakage of absorption wells of the formation such as well depth distribution,working conditions,incidence of well leakage,and leakage path,it is revealed that the main causes of well leakage are the development of Ordovician carbonate cracks and caves,the high actuated pressure of drilling,and the sensitive formation pressure.According to the distribution law of leakage pressure differences and leakage velocity,corresponding initiation pressure models are established,as well as the method for calculating the equivalent density of formation leakage is developed.The calculation result is identical with the actual conditions,laying a solid basis for leakproof and lost circulation.