Method for testing sealing performance of casing string

The invention provides a method for testing the sealing performance of a casing string, and belongs to the technical field of oil and gas exploitation. According to the method, an oil pipe or a drill rod is tripped into a casing string, liquid in the oil pipe or the drill rod is replaced with low-density fluid, then inflow testing is carried out, and a relational graph of flow and a Hough time logarithm value is drawn so as to determine whether leakage exists or not. According to the method, after well cementation construction and before oil layer perforation, mud is contained in a casing string at the moment, negative pressure (Hough inflow) testing is conducted, and whether the casing string leaks or not is accurately determined by judging whether the inrush flow of a well is jointly caused by flowing into a shaft (leakage) and thermal expansion or only caused by thermal expansion. 本发明提供了一种套管柱密封性的检验方法，属于石油天然气开采技术领域。所述方法通过在套管柱内下入油管或钻杆，并将油管或钻杆内的液体替换为低密度流体，然后进行流入测试，绘制流量与霍纳时间对数值的关系图，以确定是否存在泄漏。本发明在固井施工后，油层射孔之前，此