龙女寺构造须家河组天然气成藏主控因素

龙女寺构造须家河组天然气藏为较典型的岩性油气藏,其圈闭闭合高度低、储层致密、气水分布关系复杂。分析了须家河组气藏的烃源岩、储集岩、盖层和圈闭条件,认为其成藏条件优越;利用磷灰石裂变径迹技术和Easy%Ro化学动力学模拟技术重建了烃源岩的生烃演化史,结合构造演化再现了须家河组气藏的充注过程,将其分为3个成藏阶段,中侏罗世末期的油气初次充注期,白垩纪末的大规模充注期和喜马拉雅期的气藏改造和重新定位阶段。指出了须家河组岩性气藏成藏的主控因素:优质烃源岩的发育是物质基础,古今构造均处于油气运移的有利指向区,储集物性和圈闭闭合高度控制了气水的分布,局部裂缝发育带则是成藏及高产的关键因素。

Control Factor of Natural Gas Accumulation in Xujiahe Formation, Longnüsi Structure,Sichuan Basin

The natural gas reservoir in Xujiahe Formation of Longnüsi structure is a typical lithologic gas reservoir,with the low trap closure,the tight reservoir,and the complicated gas-water contact. The paper analyzes the source rocks,reservoir rocks, cap rocks and trap conditions of gas reservoir of Xujiahe Formation,and conculdes that the Xujiahe Formation is advantageous play. The Apatite Fission Track and Easy%Ro Chemical Kinetics Simulatiom are both used to reconstruct the hydrocarbongeneration history of source rock. Combined with the structural evolution,the charging process of Xujiahe Formation gas reservoir was reproduced. The accumulation process is divided into three phases:early hydrocarbon charging at the end of middle Jurassic,the dominant hydrocarbon charging period at the end of Cretaceous,and the final accumulation of gas pools during Himalayan. The main controlling factors of gas accumulation in Xujiahe Formation are analyzed in the paper. Highquality hydrocarbon source rock is the primary material,the ancient and present structural high are the available zones for the hydrocarbon migration,the reservoir physical property and the trap closure control the gas-water distribution in the gas reservoir,and the fractures developed locally is a key factor of gas accumulation and high productivity in the Xujiahe Formation.