Study On NMR Permeability Models Of Complex Lithology Reservoir

Permeability is one of the important parameters of logging reservoir evaluation,which would influence the quality of the reservoir and the mining measures.Nuclear magnetic resonance?NMR?logging is almost not affected by the influence of the rock skeleton and can directly reflect the pore structure,which has a comparative advantage in the estimation of permeability.The complex lithology reservoir of Y reservoir in Bohai bay has the characteristics of changeable lithology,varied pore type and strong heterogeneity,which leads to the poor application effect of commonly used porosity and permeability regression model and classical NMR permeability model.In this paper,with the collected core analysis data and logging data,the new NMR permeability model suitable for rock physical evaluation in the target region is proposed.Firstly,the reservoir characteristics and logging response characteristics in the target region are introduced.Then with the consideration of the permeability direct influence factor,pore structure,and the reference of mercury injection experiment characteristic parameters,the reservoir pore structure quantitative research based on NMR T₂ spectrum is carry out.In order to explore the influence of pore size,shape,distribution and connecting relation on permeability,T₂ spectrum information is adequately extracted and the characteristic parameter set is established.Finally,the parameter optimization according to the set is implemented,according to which new NMR permeability model suitable for the complex lithology reservoir in the target region is set up.By comparing the application effect of the new model with the Coates model and the SDR model,it turns out that the accuracy of NMR logging permeability is improved by the new model.