Application of Logging-ratio Characteristic Parameters to Productivity Evaluation in Daniudi Gas Field in Northern Ordos Basin

Started from the geological and lithological characteristics of the tight sandstone reservoir of Upper Palaeozoic in northern Ordos Basin,Daniudi Gas Field,and based on fine interpretation of reservoir parameters,a research on method for analyzing and evaluating potential productivity of gas reservoir has been completed.This method firstly distills some classified groups of local logging-ratios as characteristic parameters of the reservoir,including lithological parameters(ratio of relative Gamma Ray,ratio of caliper);resistivity parameters(ratio of relative spontaneous potential,ratio of deep to shallow resistivity);porosity parameters(ratio of acoustic slowness,ratio of density);then integrates these parameters weighted by local empirical values to form a integrated ratio of potential productivity of the gas reservoir(K);fits the product KH of K and the layer thickness H of the reservoir,named as logging characteristic index for the potential of the reservoir(KH),to data measured in non-resistance flux test of the gas reservoir,and gets corresponding empirical regression relation.Finally,in evaluation of gas reservoir,the K is used to grade the gas reservoir as its criterion,and the KH to predict potential productivity of the reservoir.Good effects of the method have been shown by test results,and its applications have been extended to reservoir productivity evaluation of new-drilled wells and re-analysis of old-drilled wells in Daniudi gas field.