Fluvial Sedimentary Characteristics And Favorable Facies Zone Prediction Of The Second Member Of Jurassic Toutunhe Formation In Fudong Slope

The second member of Toutunhe Formation(J₂t₂)of Middle Jurassic is one of the most important oil-bearing series in the slope area of Fudong.However,the following large-scale rolling exploration is seriously restricted by the lack of data accuracy and complex sedimentary evolution law.Therefore,it is of great significance to clarify the favorable sedimentary facies belt,predict the favorable reservoir distribution,and summarize the sand body scale,distribution range and superimposed relationship of different types and periods,which can provide theoretical basis for the next exploration and development of Fudong slope.In this study,combined with previous research results and existing data,we have carried out researches on small layer division,single well microfacies identification,well connected microfacies characterization,sand body correlation,plane distribution law and vertical evolution of sedimentary facies,and comprehensive prediction of favorable facies zones(1)Based on the sedimentary facies law of the study area,combined with the characteristics of cuttings logging and logging curve,all single wells are divided into medium-term cycle and short-term cycle,and the division standard of small layer is established.The first two members are divided into J₂t₂?1?J₂t₂?2?J₂t₂?3 layers.(2)Through the analysis of core structure and structure in the study area and the comparison of logging curve characteristics,the well logging facies template and microfacies division scheme table are established,and four subfacies are determined,i.e.meandering river deposition,riverbed,embankment,river overtopping and abandoned channel filling.The riverbed subfacies are subdivided into two microfacies,i.e.channel detention and beach,and the embankment subfacies are subdivided into natural dike and crevasse fan,flood plain and abandoned channel are the two main microfacies.(3)According to the characteristics of provenance system in the study area,ZTR index,stable unstable heavy mineral ratio and rock composition characteristics are analyzed.Combined with regional geological background,seismic profile and sediment grain size,provenance system of Fudong slope is comprehensively analyzed.It is determined that the provenance area of the first two members of Fudong slope is Beisantai uplift.(4)Study area J₂t₂?3 the most developed microfacies are the bank microfacies in the deposition period of the third sublayer,and the most developed microfacies are at J₂t₂?2 the material supply of the second layer decreased and remained stable until J₂t₂?1 after the end of the deposition,the northern river changed from east to west to northeast to southwest.(5)Based on the distribution range and scale of sandbodies,combined with the physical property characteristics,heterogeneity and thickness of sandbodies,according to the different conditions of each small layer,the reservoir evaluation and classification standards of three small layers in the first two member of Fudong slope are formulated.The reservoirs are divided into class I(dominant reservoir),class II(medium reservoir)and class III(poor reservoir),and the favorable facies zones are predicted.