关键词: 西太平洋, 湖相沉积, 油气聚集带, 盆地类型, 板块构造

Abstract:

The Western Pacific oil-bearing belt where source rocks and reservoir rocks are do-minated by lacustrine deposits extends longitudinally across the whole globe.The forma-tion of the belt is related to the subduction and collision between the oceanic plate and the continent plate,the disintegration of the ancient continent,the influence of the ancient Pa-cific Ocean(and the Indian Ocean in the southern hemisphere) on the paleoclimate of thesedimentary basins and the promotion of high geothermal value for the formation of hy-drocarbon.The lakes located in the north and the south of the belt are older (mostlyformed in the Mesozoic) than those in the central part (mostly formed in the Cenozoic),and are older in the west than in the east.Lacustrine facies have changed into marine fa-cies from west to east.The evolutionary history of the lake basins consists of three stages:faulted-subsidence stage,faulted-depressive stage and depressed subsidence stage.The ini-tial phase was dominated by filled-deposition,evaporation associated with source beds.Inthe middle phase,very thick source bed,sandstones and conglomerates derived from riverdelta,diluvial and turbidite phases as well as lacustrine carbonate were formed.The latephase was characterized by extensive and very thick sandstones and conglomerates which were deposited in fluvial environment.The duration scale and feature of each stage is alldifferent in distinct types of the basins.The Western Pacific oil-bearing belt mostly com-prises five types of hydrocarbon bearing basins which can be divided generally into threesubbelts.The first is non-marine subbelt(including near-inland depression basin,near-ocean depression basin and near-ocean faulted-subsidence basin),where both source bedsand reservoir beds (except for basement rock reservoirs) are lacustrine deposits.Big-andmedium-sized oil and gas pools are mostly bed rock pools,anticline (including drape-anticline)pools,plus small amount of faulted block pools,stratigraphic pools and lithologicpools.The second is transitional facies subbelt (including the faulted subsidence and de-pression composite basins on active and passive continent margin).This subbelt is charac-terized by the source beds of lacustrine facies which were formed in the early stage ofbasin evolution,and the reservoir beds of marine facies which were formed in the latestage.The big-and medium-sized oil and gas pools are composed of anticline (includingdrape-anticline) pools,reef pools and stratigraphic pools.The third is the Western Pacificisland arc subbelt basically consisting of marine deposits.The oil and gas pools in eachsubbelt are distributed around the hydrocarbon generation depressions.