FAULT CONTROLS ON OIL AND GAS IN THE MOSUOWAN AREA,JUNGGAR BASIN

The strata overlying the Triassic in the Mosuowan on the whole occur as a monocline and the traps are mostly related to faults,which may fall into the deep and shallow fault systems.Deep faults are reversed ones developed in the Carboniferous to Permian,while shallow faults are tensional and tenso-shear ones developed in the Jurassic.In the Late Jurassic,shallow faults were initiated and extended upward to the surface,thus causing dissipation of hydrocarbon.From the Cretaceous to Tertiary,fault sealing built up with thickening of the overlying strata.According to an analysis of the lithological combination and mudstone smear factor,the fault sealing properties of the Mobei uplift is better than those of the Mosuowan uplift,and the smear effect of mudstone in the first sandstone set (J₁s₂¹) of the Second Member of the Lower Jurassic Sangonghe Formation is better than that of the second sandstone set (J₁s₂²) of the Second Member of the Lower Jurassic Sangonghe Formation.The hydrocarbon is diverted toward the reservoirs on two sides of the fault when it moves vertically along the fault,and the coefficient of diversion is related to the obliquity,thickness and permeability of the reservoirs.The hydrocarbon will preferentially enters the thicker and more permeable J₁s₂² reservoir;however,the thin and less permeable J₁s₂² reservoir prefers to entrap the late-stage highly mature hydrocarbon.