Hydrocarbon generation and expulsion caused by pressure difference between source rock and reservoir during basin subsiding and uplifting
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摘要: 含油气盆地石油地质演化史可划分为持续沉降加载增压、整体上升卸载减压和全面萎缩调整平衡3个阶段.通过不同演化阶段地层压力的调整,最终实现成烃成藏过程.利用地层孔隙热压生排烃模拟实验装置进行了4个系列不同源储压差下的生排烃模拟实验,研究表明:(1)盆地持续沉降阶段,烃类可以在与烃源岩直接互层的砂岩中聚集,有利于源内岩性圈闭的成藏,但难于远距离运聚成藏.(2)盆地抬升剥蚀阶段,源储压差促进了烃类的有效排出,有利于长距离运聚成藏,压差越大,排油效率越高;且存在源-储压差有效排烃门限值:3～6MPa,只有达到该门限值,即抬升剥蚀300～600m的厚度时烃类才能有效大量排出.(3)源储压差有利于烃类的排出和烃源转化.排烃次数和排烃动力(源储压差)具有互补性,在源岩能提供大量烃类的情况下,排烃次数越多,排烃动力越大,烃类产率越高.Abstract: The evolution history of hydrocarbon-bearing basins can be divided into 3 stages:subsiding (pressure increasing),uplifting (pressure decreasing) and withering (pressure balancing).Through different stages of energy adjustment,the process of hydrocarbon accumulation has been eventually realized.Hydrocarbon generation and expulsion simulations have been carried out with 4 different pressures between source rock and reservoir using formation pore thermocompression simulation instrument.1) During the subsiding stage,hydrocarbon accumulates in sandstones which interbed with source rocks.It is favorable for accumulation in lithologic traps,yet difficult to travel far away.2) During the uplifting stage,the pressure difference between source rock and reservoir promotes the effective discharge and the long-distance migration of hydrocarbon.The bigger the pressure difference is,the higher the discharge effect will be.3 to 6 MPa of pressure difference is the threshold for effective discharge.When uplift and erosion are 300 to 600 m thick,hydrocarbon discharges in large quantity.3) The pressure difference between source rock and reservoir is beneficial for hydrocarbon discharge and source transformation.Hydrocarbon expulsion frequency and power are complementary.If source rock can provide a large quantity of hydrocarbon,the more frequent the hydrocarbon discharges,and the greater the expulsion power is,the higher the hydrocarbon production rate will be.
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