Hydrocarbon generation potential of residual kerogens in high-over matured shale rocks and its contribution to shale gas reserves

A low matured shale rock from Lucaogou Formation in the Santanghu Basin was thermally simulated using semi-open system pyrolysis experiment in attempt to evaluate its late gas generation potential. The Rock-Eval results showed that the residual kerogen in the high-over matured shale rocks still possess some hydrocarbon generation potential. The amount of the pyrolyzable hydrocarbons (S2) generated from the residual kerogen ranged from 0.57 to 1.02 mg HC/g rock. The S2 and hydrogen index (HI) values began to diminish at EasyR_o > 1.45%. About 1 m³/t rock of methane was estimated from Lucaogou Formation at high-over maturity stage. This indicates that the hydrocarbon generation potential of residual kerogens in the high-over matured shale rocks have a significant contribution to shale gas reserves.