Experimental Study on the Pore Shape Damage of Shale Samples during the Crushing Process

Using crushed shale samples to obtain pore information from the gas adsorption experiments is a widely used method. Previous studies have evaluated the impact of the particle size on the pore size distribution, but potential pore shape damage during the crushing process has not been thoroughly investigated. In this paper, we crushed and sieved the same shale samples into five different particle sizes and studied their pore structures using nitrogen adsorption. The results demonstrate that, as the particle size decreases, the shape of the hysteresis loop changes from H2 type (ink-bottle pore shape) to H3 type (slit pore shape). The hysteresis index decreases as the particle size decreases, indicating potential damage of the ink-bottle pores during crushing. As the particle size becomes smaller, the pore complexity first decreases and then remains steady. We, therefore, conclude that crushing shale samples into smaller particle sizes could damage the ink-bottle-shaped pores, which needs to be considered in sample preparation protocols for the gas adsorption analysis.