Study On Sedimentary Facies Of Guantao Formation In Linfanjia-Shangdian Area,Dongying Depression

This dissertation focuses on the sedimentary facies and favorable reservoir of Guantao Formation in Linfanjia-Shangdian area of Dongying Depression,through application of sequence stratigraphy and petroleum geology principles,analyses of well log,seismic,and core data,and review of related background literatures.The purposes of this dissertation aim to identify the sequence stratigraphic framework of Guantao Formation,correlate synchronous units,analyze the characteristics of the sedimentary facies,and delineate the sandstone distribution.Based on the aforementioned work,potential exploration targets can be predicted by integration of the physical features.The top bounding surface of the Guantao Formation corresponds to the T0 seismic reflection and the bottom surface corresponds to the T1 seismic reflection.One long-term,four medium-term,and thirteen short-term base level cycles are identifiable on seismic sections.Therefore,the Guantao Formation can be divided into four sandstone beds,named as Ng4,Ng3,Ng2,and Ng1,and thirteen single sandstone beds.The Guantao Formation is composed of graygreen siltstones,purple-brown-red mudstones,and gray gravely sandstones,showing a finingupward trend in vertical direction.The Ng3,Ng2,and Ng1 sandstone beds,as well as the Ng4-2 and Ng4-1 single sandstone beds have clear lenticular geometry as sandstone surrounded by mudstone,and the Ng4-4 and Ng4-3 single sandstone beds have flaser geometry as mudstone surrounded by sandstone.Sedimentary structures include bottom scour surface,planar bedding,and trough cross bedding.The sedimentary textural maturity of the rocks is moderate.The well log responses show box,bell,funnel,and serrated geometry.The Ng4-4 and Ng4-3 sandstone beds mainly develop braided stream depositional systems,including the mid-stream bar,braided channel margin,and interdistributary bay subfacies.The upper Guantao Formation develops meandering stream depositional systems,including point-bar,natural levee,crevasse splay,river floodplain,and oxbow lake subfacies.The sandstone bodies within Ng4-3 to Ng4-1 single sand bedstone are mainly distributed in the form of belt.The Ng4-4 single sandstone bed is continuous and the internal sandstone bodies are lenticular in geometry.The overall orientation is nearly north-south and the source is mainly derived from north.In the longitudinal direction,multiple sandstone bodies are developed and their thickness are generally thin and decrease rapidly away from the depocenters.According to the distribution pattern of sand bodies and the type of sedimentary microfacies,combined with the physical properties of the work area,the reservoirs in the area are dived into three types.The type of I and II are favorable reservoirs.The type I reservoirs are scattered in the working area,and the type II reservoirs are widely distributed in strips.