Abstract:

Pearl River Mouth Basin,an epicontinental sea and marginal sea basin,is one of depositional basins abundant in oil and gas in China.Its formation and evolutive process could be divided into three phases:rifting phase from Late Cretaceous to Early 0ligocene,thermal subsidence phase from Late Oligocene to Mid-Miocene,faulted block uplifting and sagging from Late Miocene to the present,forming three assemblages of depositional system,such as continental facies,semi-closed marine facies and open marine facies respectively.On the basis of the seismic data,a Cenozoic depositional model of this basin has been established.At the initial rifting phase,filling patterns of the basin were characterized by fluvial and lacustrine facies;in the meantime,Wenchang Formation,the most important source strata,had been formed.At the thermal subsidence phase,the transitional facies and marine facies were the typical depositional systems in this basin,so that the favorable combinations of reservoir and seal were provided.At this phase,three major oil-bearing systems were formed in Zhuhai Formation,Zhujiang Formation and Hanjiang Formation,which belong to a coastal and delta depositional system.At the third phase,faulted block uplifting and sagging,the subsidence of the basin occurred and the regional seals were formed.The sedepositional assemblages reflected the features of extensional marginal sea basin's evolution.Basin evolution and resource effect represent the match of seals,reservoirs and source rocks in these three phases.Therefore,the favorable strata for hydrocarbon exploration are the clastic rocks of delta and the continental shelf carbonate rock formed in thermal subsidenc phase.

Key words: Pearl River Mouth Basin, marginal sea, genetic evolution, depositional filling model