烃源岩可溶烃、热解烃、总有机碳含量与光谱指数相关性研究

烃源岩的可溶烃含量(S1)、热解烃含量(S2)和总有机碳含量(TOC)是进行烃源岩研究和评价的重要指标,以往主要通过实验室分析方法获得,时效性得不到保证。为了探讨野外快速测量这些指标的可行性,采集了乌兹别克斯坦克孜勒库姆地块10件烃源岩样品,运用地面ASD光谱仪和碳硫分析仪,分别测定了样品的可见光-近红外-短波红外(Vis-NIR-SWIR)反射光谱和S1, S2和TOC含量参数。运用光谱拟合微分,获得了上述样品反射光谱的一阶导数、二价导数等微分数据;并运用线性回归方程拟合和拟合结果统计分析,研究了这些数据同S1, S2和TOC含量之间的相关性。结果表明:烃源岩S1含量与原始光谱、光谱一阶导数、二阶导数分别有1 973, 511和239个波段相关,相关系数绝对值最大值分别为0.612, 0.823和0.889,相关性程度分别为弱、较强、极强;烃源岩S2含量与原始光谱、光谱一阶导数、二阶导数分别有2, 144和205个波段相关,相关系数绝对值最大值分别为0.561, 0.867和0.926,相关性程度分别为弱、较强、极强;烃源岩TOC含量与原始光谱无相关性,与光谱一阶导数、二阶导数分别有18、 180个波段相关,相关系数绝对值最大值分别为0.882和0.879,相关性都极强。此外, S1含量与光谱二阶导数的2 012 nm波段拟合优度最高,达0.790;S2含量与光谱二阶导数的363 nm波段拟合优度最高,达0.858;TOC含量与光谱一阶导数的2 480 nm波段拟合优度最高,达0.777。结果说明,利用可见光-近红外-短波红外反射光谱反演烃源岩S1, S2和TOC含量具有比较好的效果。为研究野外烃源岩的原位检测奠定了重要的基础。

Study on Correlation Between Total Organic Carbon,Soluble Hydrocarbon,Pyrolytic Hydrocarbon Content and Spectral Index in Source Rocks

The total organic carbon content(TOC), soluble hydrocarbon content(S1) and pyrolysis hydrocarbon content(S2) of source rocks are important indicators for the study and evaluation of source rocks. In the past, they were mainly obtained through laboratory analysis, and the timeliness could not be guaranteed. In order to explore the feasibility of rapid measurement of these indicators in the field, this study collected 10 hydrocarbon source rock samples from the qilakum block in uzbekistan, and measured the visible light-near infrared-short wave infrared(vis-nir-swir) reflectance spectrum and content parameters of TOC, S1 and S2 of the samples respectively by using the ground ASD spectrometer and carbon and sulfur analyzer. The first derivative and second derivative of the reflectance spectrum of the sample were obtained by spectral fitting differential. The correlation between these data and the contents of TOC, S1 and S2 was studied by using linear regression equation fitting and statistical analysis of fitting results. The results show that S1 content of source rocks was correlated with the original spectrum, the first derivative of the spectrum and the second derivative of the spectrum in 1 973, 511 and 239 bands, respectively. The absolute value of the correlation coefficient was 0.612, 0.823 and 0.889, respectively. The correlation degree was weak, strong and strong, respectively. S2 content in source rocks was correlated with 2, 144 and 205 bands of the original spectrum, the first derivative of the spectrum and the second derivative, respectively. The absolute value of the correlation coefficient was 0.561, 0.867 and 0.926, respectively. The correlation degree was weak, strong and extremely strong, respectively. There was no correlation between the TOC content of source rocks and the original spectrum, and it was correlated with 18 and 180 bands of the first and second derivatives of the spectrum, respectively. The absolute value of the correlation coefficient was 0.882 and 0.879, respectively. The correlations were extremely strong. In addition, the best fitting degree of S1 content and the second derivative of spectrum at the band of 2 012 nm was 0.790. The best fitting degree of S2 content and the second derivative of spectrum at the band of 363 nm was 0.858. The best fitting degree of TOC content and the first derivative of spectrum at the band of 2 480 nm was 0.777. This study lays an important foundation for in-situ detection of source rocks in the field.