Structural bulk analysis of heavy crude oil fractions n-d-M method

3 Structural Bulk Analysis of Heavy Crude Oil Fractions n-d-M Method 

The main idea of structural bulk analysis of heavy crude oil fractions is based on the existence of the so-called average molecule. The average molecule describes the chemical and structural properties of all molecules present in the sample mixture. It means that the result of structural bulk analysis is not the determined amount of compounds or compound groups, but it is the amount of carbon in certain structural groups, for example in aromatic groups, naphthenic groups and paraffinic groups. 

The most popular and simple method for structural bulk analysis for heavy crude oil fractions is called n-d-M analysis. The main idea behind this method is the linear dependence of aromatic, naphthenic and paraffinic carbon in heavy fraction on refractive index, density and value reverse to the molecular weight. This dependence is described by equation (2.23). 

Ad - density difference between sample density and hypothetical paraffin density 

An - refraction index difference between sample refraction index and hypothetical paraffin refraction index 

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