Abnormal High Pore Pressure Prediction and Cause Analysis of Salt and Anhydrite Formation of Fauqi Oilfield in Iraq

Abnormal high pressure exists in Lower Fars formation of Fauqi oil field in Iraq and lead to many complicated problems during drilling. There are salt, anhydrite and shale in Lower Fars formation through lithology analysis. Through the crossplot of sonic velocity vs. density data, it can be identified that the high pressure of Lower Fars is cause by the undercompaction of shale. Through composite analysis of different prediction methods of pore pressure, Eaton model is used to calculate the pore pressure of Lower Fars. The pore pressure begins to increase at the MB4 layer and declines to normal value at MB2 layer, and the peak is about 2.20 g/cm(3). The calculated results are in conformity with field situation, which can be applid to guide drilling practice in Fauqi oil field.