芳烃参数在湖相烃源岩成熟度评价中的适用性——以银根—额济纳旗盆地中生界烃源岩为例

芳烃参数在烃源岩和原油成熟度的研究中有广泛应用,但不同地区的应用效果不一,芳烃参数的影响因素及参数对不同地区、不同类型烃源岩成熟度评价的适用性争议很大。基于银根—额济纳旗盆地中生界湖相烃源岩的大量测试分析数据,通过系统分析各芳烃参数与镜质体反射率(R_o)的相关关系,探讨了芳烃参数在湖相烃源岩成熟度评价中的适用性。研究结果表明,对于甲基萘参数(MNR)、三甲基萘参数(TMNr3)和五甲基萘参数(PMNr),成熟度和沉积环境均不是其主要影响因素,因而其对成熟度也无指示意义,在评价湖相烃源岩成熟度时需慎用。三甲基萘参数(TMNr、TMNr1和TMNr2)以及四甲基萘参数(TeMNr)在R_o<1.00%时分布较为分散,在R_o>1.00%时对烃源岩的成熟度有很好的指示作用。二甲基萘参数DNR-1和二甲基菲参数DPR、DPR2与成熟度的关系较为相似。其中,DNR-1在R_o<1.00%时对烃源岩的成熟度无指示作用,在R_o>1.00%时随着R_o的增...

Applicability of aromatic parameters in maturity evaluation of lacustrine source rocks: a case study of Mesozoic source rocks in Yingen-Ejinaqi Basin

Aromatic parameters are widely applied in research of the maturity of source rocks and crude oil, but the application effect varies in different regions. There are great disputes on the influencing factors of aromatic parameters and their applicability to the evaluation of the source rock maturity in different regions and types. Based on plenty of test and analysis data of the Mesozoic lacustrine source rocks in Yingen-Ejinaqi Basin and systematic analysis of the correlation between each aromatic parameter and vitrinite reflectance (R_o), this paper explores the applicability of aromatic parameters in the evaluation of the lacustrine source rock maturity. The research results indicate that for the methylnaphthalene parameter (MNR), the trimethylnaphthalene parameter (TMNr3) and the pentamethylnaphthalene parameter (PMNr), neither maturity nor sedimentary environment is the main influencing factor, so that both have no indication of maturity. It needs to avoid using them when evaluating the lacustrine source rock maturity. The trimethylnaphthalene parameters (TMNr, TMNr1 and TMNr2) and the tetramethylnaphthalene parameter (TeMNr) are scattered when R_o<1.00%, and are good indicators of the source rock maturity when R_o>1.00%. The dimethylnaphthalene parameter (DNR-1) and the dimethylphenanthrene parameters (DPR and DPR2) have similar relationships with maturity. Among them, DNR-1 has no indication on the source rock maturity when R_o<1.00%; when R_o>1.00%, the maturity increases first and then decreases with the increasing of R_o. A turning point occurs when the R_o is about 2.00%; DPR and DPR2 have no indication of maturity when R_o<1.50%; when R_o>1.50%, the maturity increases first and then decreases with the increasing of R_o, and a turning point occurs when R_o is about 2.20%. The methylphenanthrene parameters (MPI1, MPI2, MPI3, MPR, F1 and F2) are good indicators of the source rock maturity when R_o is beween 0.52% and 2.35%. The parameters MDR and MDBI of methyl dibenzothiophene (MDBT) are not controlled by maturity, but are greatly affected by the sedimentary environment. The stronger the reducibility of the sedimentary paleoenvironment is, the more likely 4-MDBT enrichment may occur. The parameters of dimethyldibenzothiophene (DMDBT)[e.g. 4,6-DMDBT/1,4-DMDBT ratio; 2,4-DMDBT/1,4-DMDBT ratio; 2,6-DMDBT/1,4-DMDBT ratio; 4,6-DMDBT/(1,4-DMDBT+1,6-DMDBT) ratio; (2,6-DMDBT+3,6-DMDBT)/(1,4-DMDBT+1,6-DMDBT) ratio] have good indication of source rock maturity, and are applicable for lacustrine mudstones. The methylchrysene (MCH) parameter, 3-MCH/1-MCH ratio, can be used to evaluate the lacustrine source rock maturity with R_o>1.00%. The triaromatic steroid parameter, C₂₈20S/(20S+20R) ratio, does not change much during the thermal evolution of organic matter, and has no indication of the lacustrine source rock maturity.