Abstract: The deep strata in the Ledong area of the Yinggehai Basin have a complex pressure structure.As indicated by the surveyed pressure data,strata at different depths and horizons have greatly different pore pressure.Especially in the Huangliu Formation,the pore pressure shows a large transverse span.Moreover,it tends to reduce at the top but rises rapidly at the bottom,with a pressure coefficient of up to 2.3,indicating the presence of significant pressure mutation.Pressure prediction using only the undercompaction model yields large errors and thus is prone to induce engineering accidents.To effectively predict the formation pressure,it is necessary to determine the genetic mechanisms of overpressure.This study effectively identified the genetic mechanisms of the overpressure using the cross plots of vertical effective stress vs logging response.The identification results show that the genetic mechanisms of the deep overpressure in the Ledong area mainly include mechanical unbalanced compaction,chemical compaction,vertical pressure transmission along faults,and hydrocarbon-generating pressurization.A proper pressure prediction method was established based on the defined genetic mechanisms,thus improving the prediction precision and ensuring the smooth construction of drilling engineering.