Experimental study on CO2 storage in coal measure gas hydrates reservoirs in Muli Coalfield

Carbon Dioxide Geological Storage (CGS) is a promising technology for reducing the greenhouse gas emissions and mitigating the climate change. The hydrate-based CO2 storage in the abandoned gas hydrate reservoir can play a key role in CGS. In this paper, artificial cores of hydrate reservoir were prepared based on the basic physical properties of coal measure gas hydrate reservoir in Muli Coalfield, and the variations in density, porosity and permeability of the core with particle diameter of quartz sand were analyzed. The variations in CO2 hydrate saturation in core were analyzed based on the low-field Nuclear Magnetic Resonance (NMR) technology, and the pore characteristics of core during the generation of hydrates were also elaborated. The results show that the porosity and permeability of cores are firstly increased and then decreased with the decreased particle diameter of quartz sand. The core pores are mainly in the diameter between 0.004-0.050 μm, composed of small holes and micropores. The variations in CO2 hydrate saturation can be divided into four stages: initial phase, induction phase, generation phase and stable phase. The nuclear magnetic signal intensity is decreased in the generation phase, and thus the saturation of hydrate in core increases rapidly. During the generation of hydrate, the curve of core pore volume proportion gradually moves from both sides to the center, and the pore distribution range is gradually decreased. The ultra-large pores gradually disappear with the hydrate formation, and the micropores play a decisive role in the formation of hydrate. Generally, the larger the core porosity is, the higher the hydrate generation efficiency and saturation. The research results provide a scientific basis for mastering the CO2 storage mechanism and efficiency in gas hydrate reservoir. © The Author(s) 2023.