Controlling Factors of Overpressure Formation in the Yinggehai Basin

Abstract

There are many previous studies on the formation mechanism of overpressure in sedimentary basins. The Yinggehai Basin is a typical strike-slip extensional basin with obvious overpressure phenomenon. Yinggehai Formation begins to appear overpressure in Central Diapir Zone with the depth of less than 2000 m. Undercompacted, hydrocarbon generation are the two main mechanisms for the formation of overpressure in Yinggehai Basin. Controlled by tectonic movements, Yinggehai Basin develops four kinds of structure-sedimentary patterns, and has a large deposition/subsidence rate formed thick mudstone layers. The thick mudstone layers not only form the undercompacted sedimentary background, also are good source rocks. Affected by Cenozoic lithospheric thinning, the Red River strike-slip fault activity and magmatic activity of local areas, Yinggehai Basin has high geo-temperature and high heat flow values which are conducive to hydrocarbon generation. This paper's study shows that tectonic movements control sedimentary facies types and distribution, deposition/subsidence rate, and geothermal field. Both of the two main mechanisms (undercompaction, hydrocarbon generation) of overpressure in Yinggehai Basin are all controlled by the tectonic movements. Therefore, the tectonic movements are the main controlling factor of overpressure formation in Yinggehai Basin.