Pore Pressure Calculation Method for Deepwater Shallow Layers with Log Data

摘要

Deepwater drilling practice faces numbers of geological hazards which happen in shallow area due tornabnormal pore pressure, and these phenomenon go worse, even affect the drilling process, combining withrnshallow flow, shallow gas, and gas hydrate conditions. However, applicable pore pressure calculationrnmethods were not established in last decades.rnFormation pore pressure change closely with SDT, especially the reaction more obvious mudstonernformation. In this paper, based on shallow soil attributes, two kinds of logging-based calculation methodsrnare put forward. One is a comprehensive interpretation method, in which porosity, shaliness and effectivernstress are taken into account. The other is a multi-regression method with the consideration of P-wavernvelocity, affected by shallow gas velocity and shallow flow velocity, and mathematical model isrnestablished by multi-regression.rnTwo wells in Yingqiong basin are exampled to verify above two methods. Meanwhile, calculationrnresults are consistent with testing data, and geological hazards can be detected. Results shows that thernmulti-regression method is more suitable for fast prediction, and the comprehensive interpretation methodrnis more accurate.rnPore pressure calculation in deepwater is different from the shallow case due to soil attributes. How tornaccurately analyze it still has a long way to go. The methods proposed in this paper have been applied inrnmany wells in the South China Sea, and provide reasonable references to drilling practice.