Study On Sedimentary And Reservoir Features Of The Third Member Of Shahejie Formation In The Western Boxing Sag

The Boxing sag was one of the secondary tectonic unit in the west of Dongying Sag in Jiyang depression.Study area was in the west of Boxing sag,with rich structural framework.In the south was the Luxi uplift,and Qingcheng raised was in the west.The most important fault here was Gaoqing fault,it was the boundary fault which controlled the sedimentary features and the reservoir characteristics here.Full use of previous research and on the basis of geological data,in the guide of sedimentology and sequence stratigraphy theory,focus on logging facies and sedimentary facies research,comprehensive utilization of logging and seismic data, we identified four third-order sequences,9 system tracts,established the sequence stratigraphic framework in the area.Sequence1,sequence2 and sequence3 can be devided into two system tracts as lacustrine transgressive system tract and the lacustrine regressive systems tract,sequence4 developed lowstand systems tract, transgressive systems tract and highstand systems tract.At the same time,we revealed the sediment filling sequences and sedimentary facies belts features,defined delta, turbidite,lakes and their distribution characteristics.Delta here can be divided into underwater distributary channel,mouth bar,distal bar etc.The extremely thick sandy body here has been much concerned,the source of it was always the focus of debate between scholars.But now we found that,during the time of this sand body’s deposition,Qingcheng raised was already an underwater Heights,which accepted Shahejie deposition,then because of the activity of Gaoqing fault during Dongying time,the heights was lifted out of the water,and subjected to erosion.So at that time Qingcheng raised didn’t provide source material.Combined with other analysis,we can find that,during that time,the main resources was mainly derived from a further uplift in the direction of Qingcheng raised,but not the Qingcheng raised directly.Upon completion of the sequence and deposition system research,based on the microscopic slice observation and analysis of geochemical data,we make a research of the reservoir characteristics of the area.The results showed that characteristics of the reservoir are more single,they are mainly of debris-feldspar sandstones,followed by feldspar-debris sandstone,porosity was mainly between 10%-25%,and the Permeability concentrated in 1×10^-3μm² to 15×10^-3μm².Between the different sedimentary,the physical properties varied little,In contrast,the underwater distributary channel had better reservoir properties,turbidite reservoir performance was followed.According to the above research,turbidite here was the advanced region for exploring.