Experimental and theoretical study on the formation of volatile sulfur compounds under gas reservoir conditions

•Short alkyl thiols and thiophenes are the main products of the pyrolysis of pentane and H2S at 360 °C.•Thiols and thiophens have distinct δ34S values at different stages of thermal maturation.•Thiophenes and aromatic fused thiophenes can preserve their original δ34S longer than thiols.•Thiophenes are not likely products form reactions of H2S and hydrocarbons under gas reservoir conditions.•The δ34S of thiols and thiophenes can be used to study their origin and alterations in natural gas reservoirs.