Introduction to special section: China shale gas and shale oil plays - Jiang, Shu; Zeng, Hongliu; Zhang, Jinchuan; Fishman, Neil; Bai, Baojun; Xiao, Xianming; Zhang, Tongwei; Ellis, Geoffrey; Li, Xinjing; Richards-McClung, Bryony; Cai, Dongsheng; Ma, Yongsheng (Interpretation, 2015)