Characteristics of Fault Developed in Jiyang Sag and Its Control Over Hydrocarbon Migration and Accumulation

The Jiyang sag is a Meso-Cenozoic faulting basin developed in the North China platform,whose stress field is of poly-phase,multi-direction and complexity because of strike-slip together with large-scale rifting basinogenesis in eastern China,as well as collision and subduction between the India-Eurasia continent and the paleo-Pacific plate since late Mesozoic Era.Faults in this basin are developed very well with a polyphased and long-termed active nature.Geometrically,there are four kinds of fault lateral combinations:parallel,echelon,brush and oblique faults.And the faults can be classified into reverse,negative and positive inversion and flower faults.According to the scale and its control over tectonic,sedimentary and hydrocarbon migration and accumulation,the faults can be orderly divided into five kinds:basin-controlling,subsag-controlling,depression-controlling,fans-controlling and sandbody-controlling faults.As a superimposed sagging basin,its major oil-gas reservoirs are anticlines or fault-nose structures,which are mainly composed of y and anti-y shapes of compound fault series.Faults of various scales play different roles in controlling depression,sedimentation and hydrocarbon accumulation.The syn-sedimentary fault plays a very important role in both formation of sag and migration and accumulation of oil and natural gas.