CHARACTERISTICS AND GENETIC MECHANISM OF FORMATION PRESSURE IN THE WUYANG SALT-LAKE BASIN

Based on the particularity of stratigraphic structure for the salt-mud interbeds of the Wuyang Continental Salt-lake Basin,the authors discussed the genetic mechanism of anomalous fluid pressure in the basin starting with its destributive characteristics combined with the burial history and thermal evolutionary history of the basin.The calculated results of pressure reveal that the anomalous fluid pressure in the salt-lake basin can be classified into shallow,middle and deep three sets of pressure-sealing systems,that is the gradational and transitional moderately anomalous high pressure system in shallow beds,the mutiple sets of low-degree anomalous high pressure system in middle salt-mud interdeveloping members and the abrupt high-degree anomalous pressure system in deep beds.The formation of anomalous pressure is mainly related to the undercompaction that the fluid in nonpenetrative beds cannot drain off due to non-isostatic compaction result from rapid subsidence.It also has something to do with hydrothermal pressure-enhancement,organic matter converting into hydrocarbon,tectonic compression,etc.