准噶尔盆地吉木萨尔凹陷陆相页岩油地质特征与聚集机理

Geological characteristics and accumulation mechanism of continental shale oil in Jimusaer sag,Junggar Basin

综合利用岩心、测井、烃源岩热解、铸体薄片、场发射扫描电镜、激光共聚焦显微镜与高压压汞等分析测试的结果,对准噶尔盆地吉木萨尔凹陷芦草沟组陆相页岩油地质特征与聚集机理进行了研究。结果表明:吉木萨尔凹陷咸化湖盆型沉积地层富含有机质,是烃源岩层也是储层,页岩油藏具有"源储一体"的地质特征,存在粉砂岩类与泥岩类和白云岩类与泥岩类两类岩性组合类型。芦草沟组大面积整体含油、"甜点"富集且原油成熟度较低。页岩油赋存岩石的润湿性为亲油性,生烃增压是页岩油运聚的主要动力。微纳米孔喉、层理缝与构造裂缝形成页岩油的有利储集空间与渗流通道。页岩油整体为源内或近源聚集,并以游离态和吸附态赋存于芦草沟组"甜点"段与泥页岩层段中。

We studied the geological characteristics and accumulation mechanism of continental shale oil in Jimusaer sag,based on the data collected from core and casting thin section observation,well log,Rock-Eval pyrolysis,field emission scanning electron microscopy (FE-SEM),laser-scanning confocal microscopy and high pressure mercury injection.The results show that the Lucaogou Formation in Jimusaer sag is originated from the organic-rich sediments in saline lacustrine basins,which serve as both source rocks and reservoirs,and the shale oil reservoirs herein are geologically characterized by “indigenous accumulation”.There are two types of lithologic associations:one is siltstone-mudstone,and the other is dolomite-mudstone.Oil is pervasive in the Lucaogou Formation,enriches in “sweet spots”,and has lower maturity.The shale oil reservoir is oil-wet,and pressurization caused by hydrocarbon generation is the main driving force for its shale oil migration and accumulation.The micro- and nano-pore throats,bedding-parallel fractures and tectonic fractures are favorable reservoir space and vadose channels for the Lucaogou shale oil in Jimusaer sag.The shale oil accumulates within or close to the source rocks as a whole,and occurs in the “sweet spots” and shale intervals in free or absorbed phases.