A method for determining the composition of a material from a petroleum stream, comprising: obtaining a reference model of composition (MoC) for the material having a boiling point above 538°C (1000°F) at atmospheric pressure, the reference MoC including a combination of molecular lumps having determined reference percent for each of the molecular lumps, wherein the reference MoC of the material is based on a molecular formula distribution obtained by a method comprising: obtaining an initial molecular formula distribution within a predetermined threshold for a sample of the material; identifying a correlation between two or more molecular properties of the initial molecular formula distribution; extrapolating, using at least one processor, the initial molecular formula distribution beyond the predetermined threshold along the correlation to construct an extrapolated molecular distribution; and renormalizing the extrapolated molecular formula distribution based on renormalization data obtained from the sample to generate a renormalized molecular formula distribution; and reconciling, using at least one computer processor, the reference MoC to match at least one selected target property of the material to obtain a reconciled MoC representative of the composition of the material, wherein the reconciled MoC includes updated percent for each of the molecular lumps, wherein reconciling the reference MoC is carried out by constrained optimization which comprises adjusting the reference percent of each of the molecular lumps to the updated percent, wherein adjusting the reference percent to the updated percent comprises adjusting the reference percent on a coarse-grained basis relative to the reference MoC. obtaining a reference model of composition (MoC) for the material having a boiling point above 538°C (1000°F) at atmospheric pressure, the reference MoC including a combination of molecular lumps having determined reference percent for each of the molecular lumps, wherein the reference MoC of the material is based on a molecular formula distribution obtained by a method comprising: obtaining an initial molecular formula distribution within a predetermined threshold for a sample of the material; identifying a correlation between two or more molecular properties of the initial molecular formula distribution; extrapolating, using at least one processor, the initial molecular formula distribution beyond the predetermined threshold along the correlation to construct an extrapolated molecular distribution; and renormalizing the extrapolated molecular formula distribution based on renormalization data obtained from the sample to generate a renormalized molecular formula distribution; and reconciling, using at least one computer processor, the reference MoC to match at least one selected target property of the material to obtain a reconciled MoC representative of the composition of the material, wherein the reconciled MoC includes updated percent for each of the molecular lumps, wherein reconciling the reference MoC is carried out by constrained optimization which comprises adjusting the reference percent of each of the molecular lumps to the updated percent, wherein adjusting the reference percent to the updated percent comprises adjusting the reference percent on a coarse-grained basis relative to the reference MoC.