Influence of soluble organic matter on mechanical properties of coal and occurrence of coal and gas outburst

Abstract

Coal is a complex organic rock. A large number of soluble organic matters (SOMs) existing in pores of the coal matrix and even in the macromolecular network structure will inevitably have some impact on the coal seam gas occurrence, migration and outburst risk. From the perspective of structure and composition of coal, a series of experiments were carried out to reveal the mechanism of SOMs on the gas outbursts. The results show that SOMs can improve the coal adsorption ability due to the strongly adsorbent groups. Compared with the raw coal, the SOMs-extracted residual coal undergoes a decrease in specific surface area and an increase in total pore volume, average pore diameter and porosity. Furthermore, compressive strength, tensile strength and elastic modulus of the residual coal are all higher than that of the raw coal, while gas content, gas emission initial velocity, drill cuttings desorption indexes (K1 and Δh2) of the residual coal are all lower than that of the raw coal. In summary, the SOMs in coal can promote coal and gas outbursts. Research results of the project provide a new way of promoting gas extraction and outburst prediction.