四川盆地川西坳陷东坡沙溪庙组油气成藏关键时刻研究

Key moments for hydrocarbon accumulation in Shaximiao Formation on the eastern slope of West Sichuan Depression,Sichuan Basin

四川盆地川西坳陷是印支期以来龙门山挤压推覆所形成的前陆盆地,中段东坡地区包含合兴场—高庙子、丰谷、永太、中江—回龙和知新场—石泉场共计5个三维地震勘探区块,涉及3个构造区带。通过研究烃源岩生烃演化史并对研究区6口井22块流体包裹体样品进行荧光观察、显微测温、测盐等系统分析,结果表明:上三叠统须家河组五段烃源岩于151~145 Ma进入生烃门限,130 Ma达到生烃高峰;研究区侏罗系沙溪庙组砂岩储层发生过3期与油气成藏有关的流体活动,分别发生在距今141~128 Ma(J_3-K_1),105~88 Ma(K_1-K_2),83~68 Ma(K_2),成藏关键时刻主要在烃源岩的生烃高峰期130~68 Ma(K_1-K_2)。

The West Sichuan Depression in the Sichuan Basin is a foreland basin formed under the compressional thrusting of the Longmen Mountain. 3D seismic was obtained on five exploration blocks on the eastern slope of the central depression,including Hexingchang-Gaomiaozi,Fenggu,Yongtai,Zhongjiang-Huilong and Zhixinchang-Shiquanchang,covering three tectonic belts. The hydrocarbon evolution history of source rocks was studied,and 22 fluid inclusion samples from 6 wells were analyzed using fluorescence,homogenization temperature and salinity measurements. Source rocks in the fifth member of the Upper Triassic Xujiahe Formation entered the hydrocarbon generation threshold at 151-145 Ma,and reached a peak at 130 Ma. Three stages of fluid activities related to hydrocarbon accumulation took place in sandstone reservoirs in the Jurassic Shaximiao Formation at 141-128 Ma（ J3-K1）,105-88 Ma（ K1-K2） and 83-68 Ma（ K2）,respectively. The peak of hydrocarbon generation of source rocks at 130-68 Ma（ K1-K2） is the key moment for hydrocarbon accumulation.