The characteristics of sandstone on the pore type, pore size distribution, pore connectivity, porosity and permeability with temperature were analyzed by scanning electron microscope, nuclear magnetic resonance and low pressure nitrogen adsorption. The pore size, pore size distribution, pore connectivity, porosity and permeability of sandstone in 25-800℃ range were analyzed. The SEM results showed that， when the temperature of <200℃, cracks along the grain boundaries are extended, 200℃ ~400℃, mineral crystal particles began to appear part of the boundary damage zone with smooth edges, 400℃-500℃, wear crystal crack, pore volume increased significantly 500~700℃, resulting in a large number of transgranular fracture crack formation, coalescence, fracture network, 700℃ ~800℃, cracks continue to expand and clay corrosion, part of carbonate mineral decomposition. Show that the N2 adsorption experiment: 25- 200 ℃, water loss has more pores, and the porosity increased with temperature rising, 200℃ -500℃, when the thermal stress is greater than the yield strength of clay minerals and clay minerals in the contraction of 450 ℃, and the water escape structure of minerals, promote increase of micropore and transition pore; more than 500℃, some minerals (such as carbonate) led to the increase in the sample hole and the transition pore content of rupture or thermal decomposition. However, the melting of some minerals leads to the collapse of the mineral skeleton, resulting in a decrease in the content of the micropores. Show that the NMR experiment: less than 200℃, increasing the micro hole content increased with the increase of temperature, medium and large pore content also increased slightly, 200-400℃, with the increase of temperature, the connectivity between medium and large pore fissure and the content increased, the temperature of 500-800℃ period, hole crack connectivity enhanced high temperature lead to the formation of internal network is a sandstone channel for fluid migration.
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