川东北地区飞仙关组圈闭含油气性的主控因素

岩心和薄片镜下观测及利用有机地球化学和统计学分析等方法研究表明,飞仙关组古油藏的含油性和现今气藏的含气性均存在很大的差异。沉积微相对古油藏的含油性起主要控制作用,金珠坪等圈闭孔隙度小于或接近于古油藏储层的物性下限(3.5%),这是造成这些圈闭不含油或含油性很差的主要原因。含沥青的鲕滩气藏的现今圈闭充满度受古油藏的含油丰度和热化学硫酸盐还原作用(TSR)反应程度的共同控制,并且TSR产物对储层的溶蚀-扩容效应及H₂S等气体的消耗作用是造成飞仙关组大多数气藏圈闭充满度较低的主要原因。晚期构造运动导致了气藏内部流体的再次调整和气、水的重新分布,这是造成飞仙关组有些原油裂解型气藏储层内部原来含油性好的部位而现今的含气性不好的主要原因。

Main controlling factors for hydrocarbon-bearing quality of traps in Feixianguan Formation in the northeastern Sichuan Basin

The observation of core and thin section and analyses of organic geochemistry and statistics showed that oil bearing quality of paleo oil reservoirs and gas bearing quality of present gas reservoirs in Feixianguan Formation were different.The micro facies were very important factors for controlling oil bearing quality of paleo oil reservoirs.The traps in Jinzhuping Field had bad oil bearing or no oil at all,because the porosity was close to the petrophysical threshold limit of 3.5%.The present gas fullness degree of bituminous oolitic beach deposit trap was controlled by the oil richness of paleo oil reservoirs and thermochemical sulfate reduction (TSR).The corrosion volume depression effectiveness for the reservoirs and the consumption of H₂S resulted from TSR production were the main reasons for making the gas bearing fullness of reservoirs lower in Feixianguan Formation.The tectonic movement in the later period resulted in the readjustment of fluid and the redistribution of gas and water in the pools,which made the parts of the oil cracking gas pools with good oil bearing into the reservoir with bad gas bearing property at present.