Pore structure evolution of tar-rich coal with temperature-pressure controlled simulation experiments

Tar-rich coal, with a tar yield of 7-12%, has significant potential for hydrocarbon resources. In this study, typical tar-rich coal samples from Daliuta mining area were selected as the research object to conduct temper-ature-pressure controlled simulation experiments that simulated stratigraphic conditions. The pore character-istics of the tar-rich coal during coal metamorphism were studied, and the pore evolution law of the tar-rich coal was revealed. The findings demonstrate that this experiment successfully simulates all coal ranks, from low coal rank to high coal rank. Tar-rich coals contain pores of five different genetic types. Gas pores and fissures exhibit a tendency toward growth, while cellular pores are gradually broken and collapsed by compaction, showing a tendency to reduce pores. Mold pores and intergranular pores remain basically unchanged. According to the quantitative analysis of pore structure, each pore has a different evolutionary pattern. Macropores are the pri-mary source of pore volume, micropores are the most active pore component in evolution, and mesopores exhibit a diminishing and then growing U shape characteristic. Three phases of tar-rich coal pore evolution-Ro, max < 0.9%, R-o,R- max = 0.9-3%, and R-o,R- max> 3%-can be distinguished, and there is a strong correlation between these stages and the coalification jumps.

Automated summary

This study investigates the pore characteristics and evolution of tar-rich coal during coal metamorphism through temperature-pressure controlled simulation experiments. The findings reveal that tar-rich coals have five different genetic types of pores, with a tendency of growth for gas pores and fissures, reduction for cellular pores, and no significant change for mold pores and intergranular pores. Quantitative analysis shows that macropores are the primary source of pore volume, micropores are the most active in evolution, and mesopores exhibit a U-shaped characteristic. Three phases of pore evolution in tar-rich coal can be distinguished, which are closely related to coalification jumps.