ObjectivernReversed isotope series of alkanes(δ13C and δ2H)are widely reported in many prolific shale plays across the world,with many researchers having proposed that isotope reversal of alkanes can be used to identify the'sweet spot'of shale gas(Tilley et al.,2011).Although heightened research emphasis has been focused on the mechanism responsible for isotope reversal,it remains controversial.Tilley et al.(2011)proposed that reversed isotope series of alkanes indicated a completely closed shale gas system and that it could thereby be used to identify the sweet spot of shale gas,although to date the mechanism by which isotope reversal could indicate a high yield of shale gas is still not fully understood.