Sedimentary Evolution Characteristics Of Different Type Basins-A Quantitative Evaluation Using Stratigraphic Forward Modelling

Passive continental margin basins,rift basins,and cratonic basins are three major types of petroliferous basins in mid-east China.The sedimentary filling processes and the stratigraphic configurations produced are unique for each basin type and the main controlling geological factors may differ significantly.Adequate understanding of the temporal and spatial differences in the stratigraphic architecture and sedimentation filling process of different types of basin,as well as the main controlling geological factors that cause the differences,will help revealing the evolution of the sequence formation and changes in the sedimentary filling patterns in the basins.and thus has important theoretical and practical significances on petroleum exploration.The Pearl River Mouth Basin,the Bohai Bay Basin,and the Ordos Basin were selected as three representative basin types to investigate their sedimentary and sequence characteristics based on the data accumulated during scientific research and exploration practice over the past decades.Three-dimensional stratigraphic architectures and sedimentary facies of these basins are established using a quantitative stratigraphic modelling program.The temporal and spatial differences of sedimentary filling characteristics of the three types of basin are also comparatively modelled and quantitative evaluated.By varying the input geological parameters,the characteristics of the sequence stratigraphic development and sedimentary evolution are quantitatively evaluated.The main controlling factors are also determined by a quantitative examination of responses of the sedimentation and filling process to various controlling factors.The research results show that the filling of the Pearl River Mouth Basin is mainly controlled by the supply of sediments and the fluctuations of sea level.In the case of insufficient sediment supply,the filling of the basin is dominated by the change of sea level;when the sediment supply is sufficient,the supply of the provenance is the main controlling factor for the basin filling.The steep slope segment(side)and the gentle slope segment of the Dongying Sag in the Bohai Bay Basin have different sedimentation filling characteristics and are controlled by different factors.For the gentle slope segment,sequence development is mainly determined by the amount of the accommodating space formed by the fluctuations of the lake level and the sediment supply.The sediment filling of the steep slope segment is mainly controlled by the rate of tectonic subsidence,in contrasting to the gentle slope segment,and its sedimentary filling is less sensitive to lake level fluctuations.In the Ordos Basin,the changes in lake level and sediment supply are equally important parameters that affect the filling of the basin.The filling pattern of the basin is exceptionally sensitive to the changes of the lake level due to its very gentle topography.Fluctuations of the lake level can affect a wide range areally;even minor fluctuations may cause large-scale changes in the sedimentary facies shift.Comparative simulations and quantitative evaluation of the sedimentary filling and evolution characteristics of the three-type basins under the control of tectonics,sea(lake)level changes,and provenance supply indicate:(1)rift basins appear to be most significantly affected by the tectonic subsidence/uplift;(2)The fluctuation amplitudes and frequencies of sea(lake)levels have obvious impacts on the sedimentary facies variabilities of the cratonic basin and the passive continental margin basins;(3)Rift basins are most significantly impacted by changes in sediment supply,followed by cratonic basins,while the passive continental margin basins are leastly affected.