Research On High-Quality Reservoirs Of Shallow-water Delta Of Chang 6 Member In Southern Danba Area

Based on drilling core and logging data,the characteristics of low permeability reservoirs of Chang 6 Member in southern Danba area are systematically studied.The main content of the article involves sedimentary characteristics and reservoir characteristics.Core and thin section observation,physical property testing,scanning electron microscope,mercury injection and other technical methods were used to analyze the main controlling factors of high-quality reservoirs.The results show that Chang 6 is thought to reflect the shallow-water delta front subfacies,mainly including underwater distributary channel and inter distributary bay.While the mouth bars were damaged by the frequently changeable channel.On the whole,it showed the characteristics of far-source and fine-grain shallow-water delta sedimentary system.The sandstone formed by the multi-subaqueous distributary channel is the most important sandbody,and it controlled by the sedimentary microfacies in the palne.The sandbodies of the Chang 6~1 and Chang 6~2 are well developed,which are vertical superimposition and transverse cut each other.The reservoirs in southern Danba area are typical low porosity-extra-low to ultra-low permeability reservoir.The rocks mainly consist of arkose and lithic arkose.Diagenesis is intense and complex.The pores of the reservoir are primarily intergranular pores,secondary erosion pores and mixed pores,which are belonged to micro-fine throat strctures.The porosity and permeability of the reservoir is low.The development of high-quality reservoirs is governed by the combined effects of deposition,diagenesis and tectonics.Underwater distributary channel and estuary dam are favorable sedimentary facies for high-quality reservoir development.The basis is the dominant rock fabric.Strong compaction and cementation are important reasons for the formation of low permeability reservoirs.But the dissolution and chlorite cladding are the keys to the development of high quality reservoirs.In addition,the late tectonism promotes the development of high-quality reservoirs to some extent.What's more,The reservoir is divided into four categories according to the preferred parameters,among which the high-quality reservoirs are?and?.At last,this paper explores the distribution rule of high-quality reservoirs of Chang 6 member within southern Danba area.