Research On Interpretation Method Of Water-flooded Layer In Low Resistivity Reservoir

YY27 block was put into production in 1997.After long-term water injection development,the comprehensive water cut of some well areas has reached as high as 85.6%.Oil and gas reserves are gradually depleted,and the focus of development is gradually shifting to the evaluation of remaining oil.But the geological conditions and water flooding of the reservoir are complicated.As a result,it is difficult to exploit the remaining oil.The block has several difficulties in evaluation water flooded layers.First,the thickness of the developed oil layer is thin,and the layer less than 2 m thick accounts for more than70% of the effective layer.Second,the relationship between the primary oil and water is complicated,and the low resistivity oil layer and Oil-water Layer are widespread.Third,the shale content of some part of block is high,and there are calcareous interlayer distribution.It affects resistivity logs that are sensitive to residual oil.In view of these difficulties,first to carry out research on the relationship between lithology,physical property,oiliness and electrical property of reservoir based on well data,production and development data,core data.Point out that the high shalness is an important reason for the low resistivity of rock strata.Secondly,use the Archie formula and dual lateral finite element theory,find out the main reason of low resistivity response to reservoir.From this build layer thickness correction chart and mud correction formula to restore the normal value of reservoir resistivity.Thirdly,Summarize the response characteristics of logging curves under different water flooding conditions.Using the response of 95 layers,like interval acoustic transit time,deep lateral direction,deep response,natural gamma ray and density,to establish a qualitative identification chart of water-flooded layer.The chart conformity rate reached 83.7%.Fourthly,calculate the reservoir parameters such as porosity,shale content and median grain size.Optimize the coefficient about saturation model of mixed argillaceous sandstone.To realize quantitative interpretation of saturation of water-flooded layer.Using the comprehensive discrimination method of water-flooded layer,interpreted the newly drilled infill Wells in the research area.The interpretation was carried out according to the discrimination of high flooding,medium and low flooding and no flooding.The interpretation results are accurate,it can distinguish low resistivity oil layer and water flooded layer and got a good application results.