Research On Logging Evaluation Of Water-flooded Zone In XX Oilfield

XXPA block in XX oilfield was put into development in 2003.Water production rate has exceeded 90%due to complicated geological conditions and the feature of significant heterogeneity.At present the oilfield has stepped into high water-cut period and some wells have been closed.There are two water-flooded methods including edge water propulsion and bottom water coning,which consist in reservoir.The relationship is extremely complicated between oil and water in reservoir.In view of the current situation,it is imperative to carry out logging evaluation research of water-flooded layers,which is conducive to finding remaining oil accumulation areas,guiding new wells to tap potential and comprehensive management of old wells,and adjusting oil field development layers.The research of oil reservoir in Yabus formation is this article’s emphasis.Firstly,on the basis of actual geological characteristics,logging response characteristics(Resistivity,GR,SP,DT)of water-flooded layers are analyzed and summarized by comparison of old and new wells data,oil layers and water-flooded layers data.We found that resistivity curves rapidly descend and natural gamma,interval transit time slightly reduced after oil layers were water-flooded.Secondly,on the basis of logging response characteristics,the crossplot method and curve overlap method can effectively identify water-flooded layers.In addition,water-flooded layers can be identified by using formation pressure change data.Thirdly,through coring analysis of laboratory data and logging curve characteristics,two water-flooded modes of positive rhythm and compound rhythm are analyzed.Finally,on the basis of establishing reservoir model of shale content,porosity,permeability and saturation,the criterion of water-flooded classification is established through water productivity formula and relative permeability data.In order to classify water-flooded grade more accurately,the standard of water-flooded grade under different irreducible water saturation is established by fitting the permeability data and combining with the formula of water-cut.This paper completes the logging evaluation of water-flooded layers in XXPA block of XX oilfield.According to the practical application results,the effect is good.