Research Of Favorable Reservoir Based On High-resolution Sequence Stratigraphic Framework In The A'si Member Of Bayindulan South Subsag

The Bayindulan sag is one of the earliest and largest oil-rich sags in Erlian Basin.With the development of exploration,the subsag has become the key areas for "secondary exploration".The target area studied in this paper is the Bayindulan south subsag,focusing on A'Si member that is rich in oil in the A'ershan group.Previous study on sedimentary reservoirs at the level of sand formations is not sufficient,and there are different views on dividing the sedimentary facies in the study area.Besides,the distribution laws of effective reservoirs are not clear.Through the study of macroscopic and microscopic characteristics of sedimentary facies,this paper summarizes the distribution characteristics of sedimentary systems and favorable reservoirs in this area.Then the author makes a comprehensive evaluation on reservoirs and selects favorable areas,providing geological basis for finding favorable exploration targets and improving oil production.According to classical sequence stratigraphic theory,this paper makes a three-level sequence division of Cretaceous strata in the Bayindulan sag at first.Then referring to high-resolution sequence stratigraphic theory,the author divides the A'Si member into three submembers and establish the sequence framework,including upper A'Si,middle A'Si and lower A'Si.Furthermore,the source entrances can be determined when the source direction is gotten through the comorehensive analysis of ancient landform,seismic data and heavy mineral.In the macroscopic view,the type of sedimentary facies can be decided through the analysis of core facies,logging facies and seismic facies.Based on the facies interpretation of single well and foundation of connected well-section,further research on lateral distribution characteristics and vertical evolution laws of sedimentary sand bodies can be conducted.While in the macroscopic view,this paper analyzes the petrology characteristics,space type and physical properties of reservoirs,and then discusses the main controlling factors of the physical properties,based on core data,thin section data and other materials.After that,favorable areas can be selected according to some parameters,such as basic characteristics and physical properties of reservoirs,sedimentary facies,and indication of hydrocarbon.According to research results,the main sediment source in research area is the eastern steep belt with two big source entrances.The western and northern belts contribute less with three secondary source entrances.The deposition systems are fan delta-lake facies here,and Niyunping develops in the shallow lake of Structure Ba?.Sediments here are influenced by the close and multiple sources and fast sedimentary environment,as a result of which the maturity of components and structure is low.It is reflected through the low porosity and permeability.The main factor affecting physical properties is sedimentation,followed by diagenesis.In addition,sand bodies of fan delta front,especially those of subaqueous distributary channels have best physical properties.Among diagenesis,cementation and compaction can deteriorate physical properties,while dissolution in later stage has the opposite effect.According to all analysis above,the paper divides the reservoirs into three categories,including?,? and ?,among which ? and ? are effective reservoirs for exploration.