Application of Laser Raman Spectroscopy to the Evaluation of the High-and Overhigh-maturity of Shale and Coal
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摘要:
激光拉曼光谱参数可以反映有机质成熟度信息, 但在高-过成熟页岩及煤有机质中研究较少。本文通过激光拉曼、有机岩石热解和镜质组反射率实验, 对南方海相筇竹寺组、龙马溪组页岩及沁水盆地、比德-三塘盆地无烟煤进行了有机质成熟度研究。利用拉曼图谱分峰拟合及前人的公式计算出拉曼计算反射率(RmcRo), 并与热解峰温(Tmax)、实测镜质组反射率(Ro)进行相关性拟合。结果表明:页岩及无烟煤拉曼图谱楔形峰带、一级峰带(D峰和G峰)、二级峰带(S2、S3、S4峰)明显, RmcRo与Tmax、Ro相关性好, 相关系数分别为0.9173和0.9614, RmcRo在成熟度评价中与Tmax、Ro评价结果具有一致性; 与前人单点测试相比, 激光拉曼多点测试可有效揭示页岩有机质成岩时期发生的不均等变化, 对非均质性的反映更加准确, 可靠性更高; 页岩的RmcRo变异系数比煤的更大, 表现出更强的有机质非均质性。研究成果可为高-过成熟页岩及煤有机质成熟度评价提供依据。
Abstract:The parameters of Laser Raman Spectra can reflect the maturity of organic matter, but there are few related studies on the organic matter in high-and overhigh-maturity of shale and coal. The maturity of shale from Southern China and anthracite from the Qinshui and Bide-Santang Basin have been determined by Laser Raman Spectroscopy, rock eval pyrolysis and vitrinite reflectance for maturity analysis and are reported in this paper. The reflectance equation proposed previously, was applied and the reflectance gained by Raman (RmcRo) was calculated. The correlation fitted regressed with the pyrolysis peak temperature (Tmax) and measured vitrinite reflectance (Ro). The results show that the wedge-shaped bands/peaks, first order bands/peaks (D and G) and second order bands/peaks (S2, S3 and S4) of shale and anthracite spectra are clear. The Raman reflectance (RmcRo) shows good correlations with pyrolysis peak temperature (Tmax, R2=0.9173) and vitrinite reflectance (Ro, R2=0.9614). The Raman reflectance (RmcRo) shows consistency and reliability with Tmax and Ro in the maturity evaluation. The multi-point test of Raman can reveal the heterogeneous variation of shale during diagenesis and has more accuracy and higher reliability in heterogeneity reflecting than the previously carried-out single-point test. The shale has a larger variation coefficient of RmcRo than that of coal and shows stronger organic matter heterogeneity. The organic matter of shale shows heterogeneous variation during diagenesis, causing a larger variation coefficient of RmcRo than that of coal and stronger organic matter heterogeneity than those of coal. The research results provide a basis for the evaluation of the organic matter maturity of the high-over mature shale and coal.
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表 1 激光拉曼光谱参数与实测Tmax、Ro数值
Table 1. Parameters of laser Raman spectroscopy, Tmax and Ro
样品 采样点 层位 峰间距
vG-vD(cm-1)鞍高
H(a.u.)鞍高比
SG峰半高宽
FWHMG (cm-1)D峰半高宽
FWHMD (cm-1)RmcRo
(%)Ro(%)或
Tmax(℃)CG-1 织金县城关镇 P2l 265.5 1974.88 5.367 158 43 2.96 3.20 CG-2 P2l 267.5 965.45 4.835 168 47 2.79 3.12 CG-3 P2l 269.0 647.07 6.000 149 42 3.09 3.39 SH-1 寺河矿 P>1s 270.0 387.24 5.308 157 44 2.99 3.28 FHS-1 凤凰山矿 C>2-P>1t 272.0 1204.09 6.373 134 42 3.25 3.52 CQ-2 重庆綦江 S>1l 267.5 345.70 4.453 192 45 2.69 380 NJ-26 曲靖会泽 ∈>1q 273.0 189.26 5.766 129 41 3.36 404 ZK2-15 曲靖麒麟区 ∈1q 268.5 270.67 11.484 80 45 3.69 423 ZK2-17 ∈1q 265.0 1210.28 4.436 210 47 2.49 384 ZK2-18 ∈1q 267.5 2466.34 6.039 162 44 2.90 395 ZK2-20 ∈1q 263.5 165.126 41.732 103 45 3.14 405 注：表格中的拉曼计算反射率公式为RmcRo=7.432*log(vG-vD)-0.306*log(S)-2.935*log(FWHMG)-3.118*log(FWHMD)-3.291[5]。 
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