Micro-Raman structural responses of nano-mechanical properties of different coal grades

Abstract

The mechanical properties of coal are heterogeneous and in multi-scale. Understanding the coal mechanical properties and structure in nano-scale is the key to know the fracturing transformation and crack expansion mechanisms of coal reservoirs. AFM and micro-Raman were used to obtain the mechanical and molecular structure parameters of the coal samples. The results showed that the elastic modulus of vitrinite ranged from 0.66 GPa to 7.58 GPa, and the elastic modulus increased with the increase of the maximum reflectance Ro of vitrinite. It is shown that with the increase of Ro, the Raman structure parameters change regularly. The relationship between elastic modulus E and Raman structural parameters was established. It was found that the peak difference（Ｇ－D） and the relative content of PAHs were positively correlated with the induced elastic modulus. There is a negative correlation between FWHM-G and E, which reflects that the increase of structural order will lead to the increase of elastic modulus, indicating that with the increase of maturity, the structure of macromolecules will be closely arranged and the intermolecular force will increase, leading to the increase of elastic modulus.

Keywords

• fracturing of coal reservoir
• coal structure
• atomic force microscope（ａｆｍ）
• micro-raman
• nanomechanical property