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.