The effect of oil extraction on porosity and methane adsorption for dry and moisture-equilibrated shales

•Over 60% extractable oil from oil-window shale is stored in the micro-mesopores.•Oil extraction has limited impacts on overmature dry shales.•Moisture contents of wet shales reduce by 7–37% after oil extraction.•Extraction increases micropore and methane adsorption capacities up to 282%.•GIP for oil-window shale can be over-estimated up to 22% by extracting the oil.