NEOTECTONICS AND THE ACCUMULATION OF OIL AND GAS ATTRIBUTED TO THE EXPULSION ACTIVITY OF GEOPRESSURED SYSTEM IN THE YINGGEHAI BASIN

The Yinggehai basin is a transform-extension basin that is dominated by the extension and formed by the combination function of the extension and thinning of lithosphere and the right-lateral movement of the Red River Fault in the basin. Under this tectonic stress,the neotectonic movement of the basin is active. The main manifestations of the neotectonics include the formation of unconformities at the end of the Miocene,the Pliocene and Quaternary within the sequences,the shift of sedimentation centers,the strong fault activities,echelon pattern of diapir structures,mud volcanoes and earthquakes. The neotectonic movement in the Yinggehai basin not only controlled the formation and evolution of the basin,the shifting of subsidence and sedimentation centers and the formation of diapir structure belts and their echelon arrangement,but also dominated the petroleum accumulation and distribution. The Yinggehai basin is a strong geopressured basin,the multiphasic fault activities and the multiphasic diapirism dominated by the fault activity in the neotectonic age formed the transport passage system for the geopressured system and petroleum,and induced the episodic expulsion and accumulation of oil and gas. The geopressured system containing the mature hydrocarbon emitted along active fault and diapir structure as the liquid pressure of geopressured system exceeded the rupture strength of the sealed layer of the geopressured system,the oil and gas generally accumulated in the transition zone of pressure and normal pressure zone with upward and lateral geopressured fluid release,and then the fault closed with the pressure of geopressured fluid descending. This expulsion process of geopressured system is episodic and generally forms big oil field or gas field in the transition zone of pressure and normal pressure zone in geopressured basin.