Research On The Logging Evaluation Method Of Medium–deep Reservoirs In The No.1 Pugu Zone Of Nanpu Sag

Affected by the margin and sedimentary environment,the deep and middle reservoirs in Pugu 1 area of Nanpu Sag have got diverse reservoir space,low permeability,complex pore structure,obvious phenomenon of non-Archie,and it is very difficult to model physical parameters.Productivity there is affected by many factors,and the accurate evaluation of its capacity is difficult to secure.According to the actual situation of the study area,four characteristics and their relationship of the reservoir are systematically analyzed.Three evaluation schemes for pore structure are constructed on the basis of the mercury pressure test and nuclear magnetic resonance experiment.The first is constructed by PCA and FCM,based on the characteristics of the mercury pressure.The second one is to characterize the pores by nuclear magnetic T2 spectrum based on fractal theory.Compared with the fractal characteristics of the mercury pressure and thin slices,it finds out the connected pores of the study area have fractal characteristics,thus determining the pore structure type according to the proportion of the reservoir connected pore.After classifying the pore structure of the reservoir through the establishment of a rendezvous plate with the YGXS and RQI,these three schemes conclude that there are four types of pore structures,which have a good correspondence to production capacity.Based on core calibration logging and pore structure classification,a reservoir porosity and permeability model is established.The fractal theory is used to characterize the pores: the small pores are not connected,the medium holes(transition holes)are partially connected,and the large ones are completely connected.Then,the effective pores making direct contribution to reservoir seepage are selected,and a new method of permeability modeling is provided.On the basis of the rock resistivity experiment,saturation parameter model of different degrees of mineralization pore structures is established,and the variable parameter model is effectively used to the non-Archie phenomenon in the cementation index.Three reservoir effectiveness evaluation models are established because of core analysis and production data test,and the minimum of effective physical property and its pore structure index corresponded are determined.According to characteristics of different fluid logging,the reservoir fluid is identified by graphic method and the mathematical method.For the differences in reservoir characteristics' sensitivity to productivity,the sensitive factors should be the first choice,and three reservoir productivity evaluation models,including the conventional productivity index rendezvous plate,the reservoir classification based oil volume rendezvous plate and the neural network method are established and interact for good effect.