Petroleum distribution characteristics and subtle reservoir exploration in South America

Forearc,compressed backarc,foreland,cratonic and passive margin basins have developed in South American ever since Paleozoic.The discovered subtle traps are mainly lithologic(tectonic-lithologic)and unconformity(basement-unconformity,lithologic-unconformity and structural-lithologic unconformity)ones.For the foreland basins,unconformity and lithologic reservoirs are the main reservoir types.For the passive margin basins,lithologic subtle reservoirs are contributive.In the latest decade of exploration,the subtle reservoirs(turbidite,pre-salt carbonate/reef and overlap reservoirs)in the passive margin basins have turned to be the main discoveries.Resource of the subtle reservoirs in South America is assessed to be over 89 billion Barrels Oil Equivalent,mainly as liquid,showing a good exploration prospect.