1. State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development, Beijing 1100083, China
2. State Center Research and Development of Oil Shale Exploitation, Beijing 1100083, China
3. School of Mines, China University of Mining and Technology, XuZhou 221116, China
4. Department of Electrical Engineering and Energy Technology, University of Vaasa, P.O. Box 700, Vaasa FIN-65101, Finland
5. Department of Civil Engineering, Aalto University, P.O. Box 11000, Espoo FIN-02130, Finland