THE EXPLORATIONAL PROSPECTS OF NON-STRUCTURAL OIL/GAS POOLS IN MARINE FACIES STRATA OF SICHUAN PROVINCE

The source potential (productivity) of hydrocarbons estimated for the marine facies strata of Sichuan Province differs greatly from the hydrocarbon reserves calculated in respect of the structural oil/gas pools.Therefore,the amount of migrated hydrocarbons can be hundreds times of that of commercial hydrocarbons in the present structural trap.Obviously,though a part of hydrocarbons generated has been dispersed through outcrops and destroyed structural traps,other parts of the hydrocarbons would be preserved in non-structural traps.It is believed that the following types of oil/gas pools would be promising.1.Ancient burial hills and stratigraphic overlaps in Leshan-Longnuzhi Ancient Upheaval (Lower Paleozoic systems);2.Structural-lithologic (stratigraphic) complex in Longmenshan Tran-sitional Zone (Devonian System);3.Stratigraphic overlaps and relic hills in the eastern part of Sichuan Province (Carbonifeous System);4.Non-structural traps in Permian dolomites of reef and reef bank facies formed due to mixing of fresh and brackish water;5.Reef facies dolomites of Changxing Formation.6.Reef bank facies dolomites of Yangxing Series for which much attention should be paid to erosional surface at the top of Yangxing Series;7.For Triassic systems,not only lithologic traps in the oolite limestones of Feixiangan Formation,the coarsely textured carbonates of Jialinjiang Formation,and the oolite and algal dolomites in Leikoupo Formation are petroliferous,but also the stratigraphic overlaps in Luzhou-Kaijiang Ancient Upheaval Zone is important.As viewed from the methodology of petroleum explorations,both the precision and reliability of seismic exploration should be improved and integrated interpretation should be carried out.In addition,the drilling and geological researches should be reinforced.