A prediction method of pore pressure in clay formation based on liquid sensitivity and loading unloading mechanism
Pore pressure is an important parameter for wellbore stability analysis.In abnormally high pressure clay formation,the high pressure mechanism is complex,and clay formation has strong liquid sensitivity,which is not conducive to predicting pore pressure and leads to high risk of drilling.Based on this problem,the clay of Anjihaihe in southern Junggar basin has been taken as an example.Considering the interference of fluid on rock physical parameters of clay,a logging correction method for the physical parameters of mudstone formation is established.By combining the sonic velocity-density chart method and comprehensive compaction curves,the mechanism of abnormal high pressure in clay formation has been illustrated.According to high pressure mechanism,a prediction method of pore pressure in clay formation of southern margin has been established based on the loading and unloading theory and effective stress principle.Results indicate that due to high content of clay mineral and lipophilicity-hydrophilia,water and oil phase both have great impact on clay physical parameters.Thus,calibration has to be done.After the calibration of logging physical parameters,the high pressure mechanism of loading and unloading in clay is determined by loading and unloading mode.The correlation between effective stress of clay and its rock physical properties under loading and unloading conditions is clarified.Compared with pore pressure prediction method of Eaton,equivalent depth method,loading and unloading method,multi-parameter comprehensive method,the method proposed in the paper has higher accuracy.The pore pressure prediction method established in this paper has been successfully applied to the pore pressure prediction in the southern margin of Junggar basin.The predicted pore pressure is in good agreement with the measured one,which can provide a reference for the pore pressure prediction of clay formation with abnormal pressure and the safe and efficient drilling in clay formation.
liquid sensintivityclayanomalous high pressurepore pressurewellbore stabilityprediction method
万方数据
维普
