准噶尔盆地吉木萨尔凹陷二叠系芦草沟组不同源储结构页岩生排油实验研究

Experimental study on hydrocarbon generation and expulsion characteristics of shale with different source-reservoir structures in Lucaogou Formation,Jimsar Sag,Junggar Basin

准噶尔盆地东部吉木萨尔凹陷二叠系芦草沟组为中国典型陆相页岩油层系。为了探究不同源储组合对烃源岩生排油的影响,基于前人对芦草沟组源储组合类型的划分,利用半封闭热模拟体系,开展不同源储结构芦草沟组页岩生排油实验研究,为页岩油富集规律及“甜点”精细评价提供参考依据。实验结果显示,储夹源型组合模式更有利于排油,源储互层型略低,源夹储型排油效率最低。碎屑岩+烃源岩组合下,储夹源型、源储互层型和源夹储型排油效率分别为35.6%、30.7%、25.6%;碳酸盐岩+烃源岩组合下,储夹源型、源储互层型和源夹储型排油效率分别为27.4%、27.5%、12.3%。结合排出油、储层中接收油及烃源岩中滞留油的族组成特征,发现储集岩中的接收油主要来自邻源供烃,源储距离越远,供烃关系越不明显。储夹源型页岩主要为下部邻源供油的特点,上部碎屑岩储层接收油量为10.7 mg/g,而下部碎屑岩储层接收油量仅为1.4 mg/g;源夹储型页岩以自生自储为主,烃源岩的滞留油含量较高,碎屑岩储层接收油量为6.0 mg/g,烃源岩中滞留油量为21.1 mg/g;源储互层型页岩以邻源供烃为主,自生自储为辅,从烃源岩到储集岩,抽提物族组分变化差异并不大,饱和烃含量分布在22.8%~33.0%,芳烃含量分布在6.2%~15.1%,非烃和沥青质含量分布在28.5%~41.1%和21.0%~30.0%,且储层岩性不同对其生排油效率影响相对较弱,含油性非均质性弱。从不同源储结构页岩生排油效率来看,源储互层型和储夹源型是芦草沟组页岩油勘探的较为有利的配置组合。

The Permian Lucaogou Formation in the Jimusar Sag in the east of the Junggar Basin is a typical conti⁃nental shale oil series in China.Employing the semi⁃closed thermal simulation system,an experimental study on hydrocarbon generation and expulsion of shale with different source-reservoir structures was carried out to explore the efficiency and composition characteristics of hydrocarbon generation and expulsion of shale in the Permian Lucaogou Formation with different source-reservoir structures so as to provide reference for the enrichment rule of shale hydrocarbon and the fine evaluation of“sweet spots”.The experimental results show that thick reservoir interbedded with thin source rock is more conducive to hydrocarbon expulsion and features the highest hydrocarbon expulsion efficiency,while thin source rock interbedded with thin reservoir features slightly lower hydrocarbon expulsion efficiency,and thick source rock interbedded with thin reservoir features the lowest hydrocarbon expul⁃sion efficiency.When reservoir lithology is clastic rock,the hydrocarbon expulsion efficiency of thick reservoir interbedded with thin source rock,thin source rock interbedded with thin reservoir,and thick source rock inter⁃bedded with thin reservoir are 35.6%,30.7%,and 25.6%,respectively.When reservoir lithology is carbonate rock,the hydrocarbon expulsion efficiency of these three combinations are 27.4%,27.5%,and 12.3%,respec⁃tively.Combined with composition of expelled hydrocarbon,received hydrocarbon in reservoir,and retained hydrocarbon in source rock,it is found that received hydrocarbon in reservoir rock is mainly supplied by neigh⁃boring sources,and the farther away from source-reservoir interface,the less relevant relationship between source rock and hydrocarbon in reservoir.Hydrocarbon in reservoir is supplied by lower adjacent source rock in thick reservoir interbedded with thin source rock,and the received hydrocarbon in upper clastic reservoir is 10.7 mg/g,while received hydrocarbon in lower clastic reservoir is only 1.4 mg/g.The thick source rock interbedded with thin reservoir is mainly self⁃generated and self⁃stored,and the content of retained hydrocarbon in source rock is high,the received hydrocarbon in upper clastic reservoir is 6.0 mg/g,while retained hydrocarbon in source rock is 21.1 mg/g.Hydrocarbon in reservoir is mainly supplied by lower adjacent source rock and partly from its own source rock in thin source rock interbedded with thin reservoir.There is no significant difference between source rock and reservoir rock in the extraction family,with the content of saturated hydrocarbon in the range of 22.8%-33.0%,aromatics in the range of 6.2%-15.1%,and non⁃hydrocarbon and asphaltene in the range of 28.5%-41.1%and 21.0%-30.0%.Moreover,different reservoir lithology has relatively weak influence on hydrocarbon generation and expulsion efficiency,and the hydrocarbon⁃bearing heterogeneity is weak in thin source rock interbedded with thin reservoir.From the perspective of hydrocarbon generation and expulsion efficiency of shale with different source-reservoir structures,thick reservoir interbedded with thin source rock and thin source rock interbedded with thin reservoir are the favorable combinations for hydrocarbon exploration in the shale of the Lucaogou Formation.