基于近红外漫反射光谱的烃源岩生烃潜量的确定

The Evaluation of Hydrocarbon Potential Generation for Source Rocks by Near-Infrared Diffuse Reflection Spectra

对比了近红外光谱和中红外光谱对烃源岩样品生烃潜量的定量分析能力。由于近红外光谱受样品的颗粒度、密度、表面粗糙度等造成的光散射的影响更大,使得其漫反射光谱数据的信噪比很低,背景干扰很大,很难直接应用于定量分析。因此需要一种有效的方法对近红外漫反射数据进行预处理来消除散射的影响。本文对比了正交信号校正算法(OSC)及其两种改进算法(DOSC和WMDOSC)对原始光谱进行预处理,并结合间隔偏最小二乘(iPLS)建模的结果,发现用WMDOSC作为预处理方法时,近红外光谱所建模型能够达到与中红外一致的准确性,使得近红外漫反射光谱技术在石油录井中有了广阔的应用前景。

Near-infrared（NIR） and mid-infrared（MIR） diffuse reflection spectra were compared and evaluated for hydrocarbon potential generation of source rocks.Near-infrared diffuse reflectance often exhibits significant differences in the spectra due to the non-homogeneous distribution of the particles,so the signal-to-noise ratio of NIR is much lower than MIR.It is too difficult to get accurate results by NIR without using a strong spectral preprocessing method to remove systematic noise such as base-line variation and multiplicative scatter effects.In the present paper,orthogonal signal correction（OSC） and an improved algorithm of it,i.e.direct orthogonal signal correction（DOSC）,are used as different methods to preprocess both the NIR and MIR spectra of the hydrocarbon source rocks.Another algorithm,wavelet multi-scale direct orthogonal signal correction（WMDOSC）,which is a combination of discrete wavelet transform（DWT） and DOSC,is also used as a preprocessing method.Then,the calibration model of hydrocarbon source rocks before and after pretreatment was established by interval partial least square（iPLS）.The experimental results show that WMDOSC is more successfully applied to preprocess the NIR spectra data of the hydrocarbon source rocks than other two algorithms,and NIR performed as good as MIR in the analysis of hydrocarbon potential generation of source rocks with WMDOSC-iPLS pretreatment calibration model.