Molecule-Based Characterization Methodology for Correlation and Prediction of Properties for Crude Oil and Petroleum Fractions

A molecule-based characterization methodology was developed for correlation and prediction of assays and properties for crude oil and petroleum fractions. From readily accessible crude oil, the assay data such as distillation curve, API gravity, and PNA contents, identifies an optimal set of chemical compositions of model hydrocarbon molecules that were designed to mimic measurable physical and chemical properties of crude oil. The model hydrocarbon molecules cover significant classes of hydrocarbon constituent molecules that are present in crude oil where each class is characterized by its molecular structural segments and segment distribution function parameters. The relative weights of the various classes of the hydrocarbon constituent molecules, the respective structural segment types, and the segment distribution function parameters together form a " molecular profile " of the crude oil. The chemical compositions of model hydrocarbon molecules, as derived from the " molecule profile " , are then used to interpolate, extrapolate, and predict crude oil assays and properties based on molecular thermodynamic models. The molecule-based methodology for crude oil assay characterization represents a superior alternative to the traditional statistics-based methodology and other empirical expressions used to interpolate between assay data points or extrapolate for heavy cuts. The " molecule profile " further offers a molecular insight into crude oil for planning, scheduling, and process simulation of oil production and petroleum refining operations. Each crude oil has unique molecular characteristics. A crude oil assay is the physical and chemical evaluation of crude oil feedstock by petroleum testing laboratories. Assays vary considerably throughout the industry—from just a handful of key properties for the whole crude, to a full set of physical, chemical, and chromatographic measurements on distilled or blended fractions and residues of the crude oil 2. Results of crude oil assay testing provide extensive hydrocarbon analysis data for refiners, oil traders, and producers. For example, assay data helps refineries determine if a specific crude oil feedstock is compatible for a particular petroleum refinery or if the crude oil could cause yield, quality, production, environmental, or other problems. The determination of crude oil assay is a lengthy, tedious, and costly process 3. The conventional approach to perform an assay consists of a set of measurements on the crude oil and its fractions. Depending on the time and cost involved, assay data can be very detailed or quite limited. Detailed assay data will generally include a full TBP analysis of the whole crude and various …