(755e) Crude Evaluation for Refinery Planning Using a Molecular-Based Assay Characterization

Refineries take crude oils, or hydrocarbons, as feedstocks and convert them into products, or finished gasolines.  Refinery planning systems determine what crudes to buy for a refinery in order to make a set of gasolines while optimizing the profit potential for that refinery.  An assay is a set of data which represents a laboratory analysis of a crude oil and is used to define the distillation behavior and other properties of the crude oil.  Assay data contains cuts, which are defined by boiling point ranges, and the properties for each of those cuts.  A crude evaluation is a common refinery planner’s workflow which aims to calculate the breakeven price for a given crude within a base crude basket for the refinery.  Conventional assay data typically consists of only a few boiling points, densities, and other property measurements for some selected cuts or for the whole crude.  Thus it is often necessary for crude oil assay experts to predict or estimate the missing properties in order to perform an accurate evaluation of a new crude in a refinery crude basket.  Many refiners use assay characterization tools to manage their lab assay data before evaluating it in their refinery planning and scheduling models.  The usage of accurate assay data in refinery models is critical since it affects the selection of crudes for purchase.  Selecting the right crudes can have a massive impact on refinery profits. 

Traditional approaches for assay data management use statistical-based methods to characterize the crude assay.  These methods present significant limitations related to accurately predicting property values outside the lab data as well as inconsistencies due to the lack of physical connections across inter-related properties.  Conventional characterization methods also perform poorly in predicting properties with sparse lab data, which is the case for the heavy components of crude oils, or bottom-of-barrel predictions.  In this work, we highlight a new molecular-based crude assay characterization methodology that provides for practical correlation and prediction of assays and properties for crude oils and petroleum fractions.  This new approach ensures consistency between the properties and is able to provide more accurate and reliable property predictions for crude assays with limited lab information.  The new molecular-based crude assay characterization methodology is incorporated inside of a refinery planning system.  Together, these tools provide the refinery planner with the confidence to make quick and accurate decisions for assessing the profitability of an available spot crude for a refinery.