Thermal maturity of the Permian Lucaogou Formation organic-rich shale at the northern foot of Bogda Mountains, Junggar Basin (NW China): Effective assessments from organic geochemistry
Thermal maturity of the Permian Lucaogou Formation organic-rich shale at the northern foot of Bogda Mountains, Junggar Basin (NW China): Effective assessments from organic geochemistry
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DOI：
10.1016/j.fuel.2017.09.069
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发表时间：
2018
期刊：
影响因子：
7.4
通讯作者：
Mingming Zhang;Z. Li
中科院分区：
文献类型：
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作者：
Mingming Zhang;Z. Li
中国位于准噶尔盆地博格达山北麓，二叠系芦草沟组蕴藏着厚厚的富含有机质页岩。芦草沟组由下段和上段组成。为评价该区芦草沟组富有机质页岩的热成熟度，对JZK井24个样品的有机地球化学成熟度参数进行了分析。分析结果表明，芦草沟组已经达到了含油窗口。对芦草沟组进行的分析表明，芦草沟组已达到了含油窗口。但这些参数不能区分芦草沟组上、下段的成熟度差异。芳香烃如烷基萘比(MNR)、三甲基萘比-2(TNR-2)、二甲基萘比-1(DNR-1)、三甲基-萘比(TMNr)、四甲基-萘比(TeMNr)、四甲基-1比(TeMNr-1)、烷基菲比(MPI)、甲基菲分配分数(MPDF)、甲基菲比(MPR)和烷基联苯比(MBpR)、二甲基联苯比x(DMBR-x)、二甲苯联苯比y(DMBPy)等也被用来评价芦草沟有机页岩的热成熟度。这些芳烃指标表明，下段主要处于早期成熟阶段(早期石油窗口)，这与岩石-演化热解和Ro的结果一致。但烷基菲比例(MPI、MPDF、MPR)和烷基联苯比例(MBpR、DMBpR-x、DMBpR-y)的评价效果并不清楚，因此不如烷基萘比例(TMNr、TeMNr、TeMNr-1)有用。上述分析结果表明，烷基萘比值(TMNr、TeMNr和TeMNr-1)可以作为评价准噶尔盆地芦草沟组富有机质页岩的有效成熟度指标。此外，根据在JZK井观察到的有机地球化学和页岩能量现象的热成熟度证据，可以得出结论：富含有机质的页岩在上段未成熟，在下段(早期石油窗口)已经生油。然而，芦草沟组由于成熟度尚未达到生气阶段，页岩气不是可采资源。
The northern foot of Bogda Mountains in Junggar Basin, Northwest China hosts thick organic-rich shale deposits in the Permian Lucaogou Formation. The Lucaogou Formation consists of the lower member and upper member. To assess the thermal maturity of Lucaogou Formation organic-rich shale in this area, the maturity parameters from organic geochemistry of twenty-four samples selected from JZK well are analyzed. The analytical results from hopanoids (Ts/(Ts + Tm), 29Ts/(29Ts + norhopane), C31–C3222S/(22S + 22R) homohopanes, C29–C30αβ/(αβ + βα) hopanes) and steroids (C27diasterane/ααα sterane, C29αββ/(αββ+ααα) sterane and C29ααα20S/(20S + 20R) sterane) indicate that the Lucaogou Formation has reached the oil window. But these parameters can not distinguish the maturity differences between the lower and upper members of Lucaogou Formation. The aromatic hydrocarbons such as alkylnaphthalene ratios (methylnaphthalene ratio (MNR), trimethylnaphthalene ratio-2 (TNR-2), dimethylnaphthalene ratio-1 (DNR-1), trimethylnaphthalene ratio (TMNr), tetramethylnaphthalene ratio (TeMNr), tetramethylnaphthalene-1 ratio (TeMNr-1)), alkylphenanthrene ratios (methylphenanthrene index (MPI), methylphenanthrene distribution fraction (MPDF), methylphenanthrene ratio (MPR)) and alkylbiphenyl ratios (methylbiphenyl ratio (MBpR), dimethylbiphenyl ratio-x (DMBpR-x), dimethylbiphenyl ratio-y (DMBpR-y)) are also used to assess the thermal maturity of Lucaogou Formation organic-rich shale. These aromatic indicators show that the lower member is mainly in the early mature stage (early oil window), which is consistent with the results from Rock-Eval pyrolysis and Ro. But the evaluation effects of alkylphenanthrene ratios (MPI, MPDF, MPR) and alkylbiphenyl ratios (MBpR, DMBpR-x, DMBpR-y) are not as clear and therefore not as useful as alkylnaphthalene ratios (TMNr, TeMNr, TeMNr-1). Above analytical results suggest that the alkylnaphthalene ratios (TMNr, TeMNr and TeMNr-1) can act as effective maturity indicators to assess the Lucaogou Formation organic-rich shale in Junggar Basin. Additionally, with the evidences of thermal maturity from organic geochemistry and shale energy phenomena observed in the JZK well, it can be concluded that the organic-rich shale is immature in the upper member and has generated oil in lower member (early oil window). However, shale gas is not a producible resource in the Lucaogou Formation, because the maturity hasn’t reached the gas generation stage.