准噶尔盆地吉木萨尔凹陷芦草沟组湖相混合沉积中缝合线发育与有机质富集研究

Stylolite occurrence and organic matter enrichment of the mixed sediments in the Lucaogou Formation of the Jimusaer Sag in Junggar Basin

准噶尔盆地吉木萨尔凹陷芦草沟组湖相混合沉积中有机质富集并且有缝合线分布。通过Jy74等井的岩心观察发现,沉积岩中有较多的微裂缝与缝合线,缝合线发育程度低,其中的锯齿状缝合线变化幅度较大,主要与单纯的压溶作用有关,往往延伸范围大,可以切穿层理;波状缝合线一般变化幅度小,主要在层面基础上通过压溶作用形成,延伸范围可大可小。缝合线有利于有机质富集,并与微裂缝组合利于油气运移。通过Jy74井有缝合线与无缝合线发育的岩石有机质丰度对比认为,缝合线的形成与有机质丰度和碳酸盐含量的关系不明显。通过不同岩性有机质丰度与矿物成分的相关分析可见,芦草沟组混合沉积的有机质富集受多种因素控制,砂岩、云岩与灰岩以运移烃为主,泥岩主要为残留烃,但部分云岩、砂岩与灰岩不同程度地含有原始固体有机质,具有生烃潜力,以泥岩类的生烃能力最强。

There are a large number of organic matter and stylolites in the mixed sediments of the Lucaogou Formation in the Jimusaer Sag of Junggar Basin.Based on the core observation of the Lucaogou Formation in the Well Jy74 etc. ,there are not only fractures but also stylolits in the rock,but the stylolits are distributed at a lower degree.The saw-toothed stylolites have bigger variation amplitude,relation with pure pressure solution,larger distribution scope and can cut across rock bedding;and the undulating stylolites have smaller variation amplitude, longer or shorter strengthen scope, and are formed by pressure solution role on the basis of rock bedding plane.It is advantageous of the combination of stylolite and fracture to petroleum migration.Based on the contrast of organic matter abundance with mineral composition and the rock distri- bution with stylolites and without stylolites in Well Jy74, there are not obvious relation between stylolite formation and organic matter abundance, and carbonate content; there are more factors to control organic matter enrichment of the mixed sediments,more migrated hydrocarbons in the sandstones,dolomites,and limestones, and more residual hydrocarbons in the shales; a part of dolomites, sandstones and limestones contain original organic matter of different degrees and have hydrocarbon-generating potential, but the shales have the strongest hydrocarbon generation capacity.