The Description Of The Characteristics And The Comprehensive Evaluation Of The Reservoirs Of Shahejie Formation In The South-west Region Of Shanan Depression

Shahejie Formation in the South-west Region of Shanan Depression is an ordinary sandstone reservoir.Shahejie Formation reservoir experiences complex diagenesis and sedimentary processes but it has great potential for petroleum exploration.In recent years,although the research around Shahejie Formation in study area is a lot,there are still many problems left now,like the lack of details in description of the features of the reservoirs,the obscurity of the knowledge in the mechanism of the reservoir origins and the incomprehension of the distribution of the high quality reservoir.Principles of sedimentology and geophysics analysis are utilized when analyzing reservoir features in this study.Regional geological background information,sedimentary condition,physical property tests and logging data are also utilized in this paper to study the features of the reservoir.Specifically,the main features of the reservoir in Shahejie formation include the lithologic characters,the structures of pores and the diagenesis characters.The study shows that lithical arkose and debris feldspar sandstone are the main sandstone type in this area.The reservoir has meso-pore and meso-throat pore structure.The average porosity of the reservoir is 17.2%,and the average permeability is 86.7m D Moreover,Shahejie formation is on the stage of Middle B diagenesis stage.The main diagenesis is compaction,cementation and dissolution.Dissolution can improve the physical property of reservoir to a certain extent and improve the flow capacity of the reservoir.Compaction and cementation has a certain degree of damage to the reservoir.Consequently,five kinds of diagenesis facies are classified utilizing indexes of reservoir characteristics and pore structure characteristics,filling characteristics and diagenetic characteristics.These five diagenesis facies are compaction face?residual intergranular pore face?carbonate cementation face?feldspar dissolution face and carbonate cementation dissolution face.Residual intergranular pore face?feldspar dissolution face and carbonate cementation dissolution face are areas of high quality reservoirs in the study area.In the end,controlling mechanism of sedimentary process and diagenesis that are responsible for the reservoir formation of Shahejie Formation are analysed.This mechanism reveals that physical properties of the front part of the braided river delta and fan delta reservoir are the best.Underwater distributary channel and delta-front sand bar is the most favorable sedimentary microfacies of high quality reservoirs.Shahejie Formation reservoir is classified into four groups: type I,II,III and IV utilizing indexes of micro structures of pores,diagenesis characteristics and sedimentary microface types.Regulations of favorable reservoir distribution of Shahejie Formation in the south-west region of shanan depression are identified.