Analysis on Prediction Methods for Formation Pore Pressure under Multiple Pressure Formation Mechanisms

Abstract

There is abnormal fluid pressure widely distributed in Yinggehai-Qiongdongnan Basin, with abnormal zones extending from different depths, and the formation causes of abnormal pressure here are complicated. It is one of the three HTHP offshore regions in the world at present. Hence, drilling in this region is very difficult. It is discovered in drilling practices in recent years that, due to the multiple formation mechanisms of abnormal formation pressure in this region, the conventional pressure prediction model based on under-compaction theory is insufficient to explain the abnormal high pressure suddenly occurring in the middle shallow layer in diapiric structure of Yinggehai-Qiongdongnan Basin, which causes very large deviation of pore pressure prediction before drilling. Based on the basic principle of improved Fillippone method and with the three-dimensional high precision seismic velocity field of geologic modeling inversion, the authors build a three dimensional pore pressure model of target block, extract the pressure slice of horizon and across the target well, analyze the other source pressure transmission possibly caused by formation connectivity, and import them into the mathematical model of pore pressure prediction, so as to attain the purpose of improving the precision of pore pressure prediction. This method has been well applied in pre-drilling pressure prediction for the HTHP block in the South China Sea, reaching a prediction precisi on above 95%.

Features of forecasting abnormally high reservoir pressures when drilling wells in areas of south-western Turkmenistan

“…It is important to note that in order to perform this analysis and final prediction, it is important to always have up-to-date data, which may not always be possible due to the hazardous terrain, which was not considered in the study. Y. Jiao (23) published a study that analyses different methods of pore pressure prediction for multiple mechanisms of formation pressure generation. In the paper, the authors proceed from the fundamental principle of the improved Fillippone method using a high-precision 3D seismic velocity field from geological model inversion.…”