川中—川东地区侏罗系大安寨段古环境及油气地质意义  

Paleoenvironment and Its Petroleum Geological Significance of the Jurassic Da'anzhai Member in the Central-Eastern Sichuan Basin

作　　者：郭奕浩 曾德铭[1,2] 张芮 王兴志[1,2] 黄董 张本健 谢圣阳 GUO YiHao;ZENG DeMing;ZHANG Rui;WANG XingZhi;HUANG Dong;ZHANGBenJian;XIE ShengYang(School of Geoscience and Technology,Southwest Petroleum University,Chengdu 610500,China;Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University,Chengdu 610500,China;PetroChina Southwest Oil&Gasfield Company,Chengdu 610041,China)

机构地区：[1]西南石油大学地球科学与技术学院,成都610500 [2]油气藏地质及开发工程国家重点实验室·西南石油大学,成都610500 [3]中国石油西南油气田分公司,成都610041

出　　处：《沉积学报》2024年第3期1016-1031,共16页Acta Sedimentologica Sinica

基　　金：中国石油—西南石油大学创新联合体项目(2020CX050000)。

摘　　要：【目的】四川盆地侏罗纪大安寨期不同地区古环境特征差异较大,探讨其演化特征及地质意义将有助于加快油气勘探的步伐。【方法】利用四川盆地中部和东部侏罗系大安寨段钻井岩心和野外剖面等地质资料,结合元素地球化学分析方法,对大安寨期古气候、古氧化还原、古盐度等古环境进行恢复和对比分析。【结果】川中—川东地区大安寨段岩性可划分为页岩、介壳页岩、泥岩、粉砂质泥岩、泥质粉砂岩、介壳灰岩和泥质介壳灰岩;大安寨第三亚段沉积期气候为干燥—半干燥,水体为亚还原条件的淡水—半咸水,处于浅湖—半深湖环境;大安寨第二亚段沉积期气候为半干燥—半潮湿,降水量较多,气温较低,水体为亚还原条件的淡水,处于半深湖环境;大安寨第一亚段沉积期气候为干燥—半干燥,水体为氧化—亚还原条件的半咸水—咸水,处于滨湖—浅湖环境;RA1井与YT1井大安寨时期均具有气候干燥→潮湿→干燥、降水量少→多→少、气温高→低→高、水体还原性弱→强→弱、古盐度高→低→高的规律;大安寨第三亚段沉积期至大安寨第二亚段沉积早期,湖盆沉积中心由川东地区往川中地区迁移,大安寨第二亚段沉积晚期至大安寨第一亚段沉积期,湖盆沉积中心则由川中地区往川东地区迁移;大安寨第二亚段TOC平均值为1.70%,孔隙度平均值为4.93%,荧光显示强烈,是大安寨段页岩油的主要生油层和储集层;古环境因素对源储配置具有较大影响,较潮湿的气候、较多的降水、较低的气温、还原性的水体和较低的盐度有利于泥页岩沉积、有机质富集和孔隙发育。【结论】川中—川东地区大安寨段古环境控制泥页岩沉积和有机质富集规律,影响页岩孔隙发育程度,这一认识可为明确四川盆地页岩油有利勘探区提供理论依据。[Objective]We attempted to determine the cause of the large difference in paleoenvironment characteristics during the Jurassic Da'anzhai period and the unclear distribution law of the shale source and reservoir in the Sichuan Basin.[Methods]Based on the geological drilling cores and field profiles of the Jurassic Da'anzhai member in the central and eastern Sichuan Basin,combined with elemental geochemical analysis methods,we performed a comparative analysis of the paleo-climate,paleo-redox conditions,and the paleo-salinity in the Da'anzhai period.[Results]The results show that the Da'anzhai member can be divided into shale,shell shale,mudstone,silty mudstone,argillaceous siltstone,shell limestone,and argillaceous shell limestone facies.The paleoenvironment of different sub-members in the Da'anzhai member is different to a certain extent.During the sedimentation period of the Third sub-member,the climate was dry to semi dry,and the water environment was fresh to semi-saline under subreducing conditions,located in a shallow to semi-deep lake environment.During the sedimentation of the Second submember,the climate was semi dry to semi humid,with more precipitation and lower temperatures,and the water environment was fresh water with sub-reducing conditions.It was a semi-deep lake environment.During the sedimentation of the First sub-member,the climate was dry to semi-dry,and the water environment was semi-saline to saline under oxidation sub-reduction conditions,located in a shallow lacustrine environment.Wells RA1 and YT1 both exhibited the following conditions:the climate was dry→wet→dry,the precipitation was less→more→less,the temperature was high→low→high,the reducibility of water was weak→strong→weak,and the paleo-salinity was high→low→high.From the sedimentation period of the Third sub-member to the early sedimentation period of the Second sub-member,the lacustrine basin depositional center migrated from the eastern to central Sichuan Basin.The middle sedimentation period of the Second sub-

关 键 词：古环境恢复 沉积中心迁移 源储配置 大安寨段 四川盆地 

分 类 号：P618.13[天文地球—矿床学]