Sedimentary Characteristics And Distribution Of Paleogene Glutenite In The Southeast Of Shaleitian Uplift Bozhong Sag

In order to seek for the distribution of glutenite in low exploration area,using three-dimensional seismic,drilling/logging,core data,the paper analyzes sedimentary characteristics and distribution of paleogene glutenite in the southeast of Shaleitian Uplift,Bozhong Sag.On the basis of seismic reflection characteristics,logging and core identification,three second-order sequence interfaces(T8,T5,T2)and three third-order sequence interfaces(T3,T3 M,T3U)are identified.The Paleogene isochronal stratigraphic framework is established by single well sequence stratigraphic analysis,sequence stratigraphic analysis of connecting wells and well-seismic combination analysis in the southeast of Shaleitian Uplift,Bozhong Sag.Four types of glutenite,i.e.fan delta,braided river delta,mixed beach and sublacustrine fan,are identified by using conventional geological methods(core observation,well logging)and seismic methods(seismic attributes,seismic facies and pre-accumulation reflection),and the horizontal distribution characteristics of glutenite are depicted.The parent rocks of Shaleitian Uplift are Proterozoic mixed granite,Cambrian-Ordovician limestone and Mesozoic volcanic rock.Mixed granite is mainly developed on the southern slope of Shaleitian Uplift,which has a strong ability to provide detrital material,while carbonate rocks are developed in the northern slope,which has a weak ability to provide detrital material.According to the different levels of water divide,Shaleitian Uplift is divided into two primary catchment units.The catchment area on the south slope is larger than the catchment area on the north slope.Fourteen secondary catchment units are identified and classified according to the difference of tectonic subsidence and structural style at the edge of the uplift.These catchment units have the characteristics of stability and strong inheritance.Through the fine description of the top structure of the basement(T8),four kinds of transportation channels are identified: palaeo-channel,single fault trough,double fault trough and transfer belt.According to the geometric shape of palaeo-channel in seismic profiles,they can be divided into V,U and W types.Under similar geological conditions in provenance areas,the larger the catchment area,the larger the area and volume of glutenite.Mixed granite rocks on the southern slope of Shaleitian Uplift are well developed and have strong ability to provide detrital material.The area and volume of glutenite are large,and they have the characteristics of large catchment area-large fan.There is a carbonate rock development area on the north slope.The carbonate rock has a weak ability to provide detrital material.The area and volume of the glutenite are small,and it has the characteristics of large catchment area-small fan.Paleoclimate can affect the weathering mode of provenance area,physical weathering or chemical weathering,and then affect the amount of glutenite deposits.The larger the length,width-depth ratio and cross-section area of the transport channel,the stronger the transport capacity and the larger the amount of glutenite in the sedimentary area.Fault activity rate is high,fan delta is the main type of glutenite,while braided river delta is the main type when fault activity rate is low.The fault activity rate is directly proportional to the thickness of glutenite,the pinch-out angle of glutenite and the supply rate of provenance,and inversely proportional to the extension distance of glutenite.