OVERPRESSURE CHARACTERISTICS IN THE JIYANG DEPRESSION, THE BOHAIWAN BASIN

Pressure evolution is controlled by geologic conditions.The Dongying and Zhanhua Sags of the Jiyang Depression in the Bohaiwan Basin are similar in tectonic characteristics and evolution,over-pressure vertical distribution,main distribution strata and origin mechanism,so their pressure evolutions also have some similarities.The Bonan sub-Sag is a typical overpressure sub-sag in the Zhanhua Sag of the Jiyang Depression.Based on quantitative analysis of pressure field evolution,it is discovered that overpressure in the Bonan sub-Sag developed late.The main strata of overpressure(the third member and the upper part of the fourth member of Shahejie Formation) developed after the Dongying episode.Overpressure in the whole Jiyang Depression developed late.