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| Comparisons of pore structures of oil shale upon conduction and convection heating |
| KANG Zhiqin1，LI Xiang1，YANG Tao2，ZHAO Jing3，ZHAO Yangsheng3，YANG Dong1 |
| (1. Key Laboratory of In-situ Property-improving Mining of Ministry of Education，Taiyuan University of Technology，Taiyuan，Shanxi 030024，China；2. School of Safety Engineering，North China Institute of Science and Technology，Sanhe，Hebei 101601，China；3. College of Mining Engineering，Taiyuan University of Technology，Taiyuan，Shanxi 030024，China) |
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Abstract In-situ pyrolysis is the mainstream trend of oil shale exploitation in the future. The in-situ heating methods are mainly divided into conduction and convection heating modes. In the process of in-situ pyrolysis of oil shale，the pores are the main channel for oil and gas seepage. The connection characteristics of the pore structure affect and control directly the production process of pyrolytic oil and gas. Therefore，in this paper，the cylindrical oil shale samples of ? 8 mm×25 mm are heated through conduction and convection with muffle furnace and steam boiler respectively. The maximum heating temperature is 550 ℃. With the micro-CT and 3D digital core reconstruction technology，the size，distribution and evolution of pores of oil shale before and after heating were studied comprehensively，and the differences of different heating modes on pore structure of oil shale were analyzed. The results show that the porosity is 2.90 times of the original porosity after the conduction heating. However，after the steam convection heating，the porosity is 3.51 times of the original porosity. The convection heating heats the oil shale evenly and the area of heat exchange is larger，so that the pyrolysis of the solid organic matter in the oil shale is more thoroughly，prompting the pores in the oil shale to expand rapidly and to connect into the large-scale connected pore groups. In addition，the convection heating steam quickly carries away the shale oil that adheres to the pore wall and remains in the dead-end of pores，which improves the connectivity between the pores and increases the pore diameter effectively and forms a better connected pore structure than in the conduction heating. The steam carries away oil and gas together simultaneously，which increases the recovery ratio of oil and gas. Therefore，convection heating is the preferred heating mode for in-situ pyrolysis of oil shale.
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2018, Vol. 37 
