准噶尔盆地莫索湾地区断层控油作用

莫索湾地区三叠系以上地层整体近单斜形态,圈闭大都与断层相关,并且断层在纵向上可划分为深、浅2套断层系统。深部断裂发育在石炭系至二叠系中,为逆断层;浅部断裂发育在侏罗系中,为张性和张扭性断层。侏罗纪晚期,浅部断裂开始发育,并断至地表,导致油气散失。白垩纪至第三纪,随上覆地层增厚,断层封闭性增强。通过断面两侧岩性配置、泥岩涂抹因子等分析,莫北凸起断层封闭性好于莫索湾凸起,且J1s12砂层组的泥岩涂抹效应要好于J1s22砂层组。油气沿断层垂向运移过程中,将向两侧储层分流,分流系数与储层倾角、厚度、渗透率等有关。莫索湾地区沿断层运移的油气将优先进入厚度大、渗透率高的J1s22储层,厚度小、渗透率低的J1s12储层有利于捕获后期高成熟的油或气。

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 (J_1s~1_2) of the Second Member of the Lower Jurassic Sangonghe Formation is better than that of the second sandstone set (J_1s~2_2) 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 J_1s~2_2 reservoir;however,the thin and less permeable J_1s~2_2 reservoir prefers to entrap the late-stage highly mature hydrocarbon.