Sediment Compaction and Pore Pressure Prediction in Deepwater Basin of the South China Sea: Estimation from ODP and IODP Drilling Well Data

摘要

Overpressure in deepwater basins not only causes serious soft sediment deformation,but also significantly affects the safety of drilling operations.Therefore,prediction of overpressure in sediments has become an important task in deepwater oil exploration and development.In this study,we analyze the drilling data from ODP Leg 184 Sites 1144,1146,and 1148,and IODP Leg 349 Sites U1431,U1432,U1433,and U1435 to study the sediment compaction and controls in the northern South China Sea.Sedimentation rate,sediment content,distribution area,and buried depth are the factors that influence sediment compaction in the deepwater basin of the South China Sea.Among these factors,the sediment content is the most important.The fitted normal compacted coefficients and mudline porosity for an interval of 50m shows disciplinary variation versus depth.The pore pressure predicted from different fitted results shows varying overpressure situations.The normal compaction trend from Site 1144 reflects the porosity variation trend in stable deposition basins in the northern South China Sea.The predicted pore pressure shows overpressure at Site 1144,which is attributed to compaction disequilibrium.Nevertheless,the mixed lithology column may influence the predicted overpressure at Site 1148,which is responsible for the confusing result.Above all,we find that sediment compaction should serve as a proxy for pore pressure in the deepwater basin of the South China Sea.