准噶尔盆地哈山地区下二叠统风城组泥页岩优势岩相与页岩油富集模式

Shale dominant lithofacies and shale oil enrichment model of Lower Permian Fengcheng Formation in Hashan area,Junggar Basin

相较于准噶尔盆地玛湖凹陷,与之紧邻的哈山地区经历了多期推覆改造,油气形成演化过程复杂,页岩油勘探面临优势岩相不明、富集规律不清等诸多挑战。为落实哈山地区下二叠统风城组页岩优势岩相,总结页岩油富集模式,以该区的哈山5井、哈深斜1井等8口探井200余块样品为基础,基于岩心、普通薄片观察等手段,在沉积环境及沉积相研究的基础上系统开展页岩岩相类型划分;结合XRD、扫描电镜、低温氮气吸附、热解等实验方法分岩相综合开展了储层物性及含油性评价;基于页岩矿物组成及有机质丰度和含油性的相关性分析,初步建立了哈山地区风城组页岩油富集模式。哈山地区风城组页岩可分为陆源碎屑岩相、白云质混积岩相、含碱性矿物混积岩相和含火山碎屑混积岩相4种岩相类型。陆源碎屑岩相中的(泥质)粉砂岩、白云质混积岩相中的白云质砂岩及含火山碎屑混积岩相储层物性及含油性较好,为有利的页岩油储集岩。页岩油富集模式可分为3类:在三角洲外前缘的陆源碎屑岩相中,主要为邻层运移的页岩油富集模式;在滨浅湖—半深湖发育段,白云质混积岩相发育段主要为同层裂缝运移以及邻层运移的页岩油富集模式;在含火山碎屑混积岩相发育的层段,为自生自储的基质型页岩油富集模式。

Compared with the Mahu Sag in the Junggar Basin,the adjacent Hashan area has undergone multi⁃stage napping and complicated oil-gas formation and evolution process,making its shale oil exploration facing many challenges,such as unclear dominant lithofacies and enrichment law.In order to optimize the dominant lithofacies of the Lower Permian Fengcheng Formation shale in Hashan area and summarize the enrichment model of shale oil,by taking more than 200 samples from 8 exploration wells in the area,including Hashan 5 and Hashen X1 wells,and using methods such as core and ordinary thin section observation,a systematic classifica⁃tion of shale lithofacies types was carried out based on the study of sedimentary environment and facies.A comprehensive evaluation of reservoir physical properties and oil content was conducted based on lithofacies by combining experimental methods such as XRD,scanning electron microscopy,low⁃temperature nitrogen adsorp⁃tion,and pyrolysis.The enrichment law of the Fengcheng Formation shale oil in Hashan area was preliminarily revealed based on the correlation analysis of shale mineral composition,organic matter abundance and oil content.The results show that the Fengcheng Formation shale in Hashan area can be divided into four lithofacies types:terrigenous clastic,dolomitic diamict,alkaline mineral diamict and volcanic clastic diamict.The(argilla⁃ceous)siltstone in terrigenous clastic lithofacies,the dolomitic sandstone in dolomitic diamict lithofacies,and the volcanic clastic diamict lithofacies have good physical properties and oil content,which are good shale oil reservoirs.The shale oil enrichment patterns can be divided into three types:in the terrigenous clastic lithofacies of the outer delta front,the shale oil enrichment patterns are mainly migrated from adjacent strata.In the shallow⁃semi⁃deep lake section,the dolomitic mixed⁃deposit lithofacies are mainly the shale oil enrichment model of the same layer fracture migration and adjacent layer migration,while the volcaniclastic mixed⁃deposit lithofacies are mainly the self⁃generated and self⁃stored matrix shale oil enrichment model.