HYDROCARBON ACCUMULATIONS SOURCED FROM GAS HYDRATE-AN IMPLICATION TO PETROLEUM EXPLORATION IN PALEOPLATFORMS

The free gas,formed by biogenic methane and pyrolysis hydrocarbon,was sealed under gas hydrate stable zone in the ocean(geosyncline) before orogenic movement.It was migrated upward with crustal uplift and thermo-pressure change,and could been accumulated passing through reservoirs.It was proved that the various maccalubers,gas seepage and hydrocarbon reservoirs were formed by gas hydrate in southwestern Taiwan sea area.Therefore,it might be inferred that the overmatured source rocks in orogenic belt provided hydrocarbon to the platform area(late cratonic basin),which could explain the formation of "oil pole" in Middle East and solve the problem of mismatch of gas reserve with hydrocarbon generation amount of source rocks in the Sichuan Basin.