Abstract:

Biyang Depression covers an area of 1000 km².Within it,530 km² belongs to its north slope.The 4 oilfields discovered before 1985 are distributed in the south slope and the central deep subsided area.In recent years,5 oilfields have been discovered in the north slope,the prospected and controlled hydrocarbon reserves occupies above 40% ofthe total reserves of the depression,and this percentage may even rise as the explor ationcarrying on.Favourable conditions for hydrocarbon accumulation in the north slope are:1.Thesuccessional sedimentation-structure complex slopes are the target area for hydrocar bonmigration;2.Multiple sandbodies provide good reservoirs;3.A series of nose-structuresare in control of hydrocarbon accumulation;4.Two sets of faults provide the conditionof shelter for hydrocarbon accumulation;5.Cap rocks on regional unconformity makeswell preservation for shallow pools in slope.There are various kinds of oil pools,within which fault-nose,fault-block and uncon formity ones are the main types.