Knowing what your crude is worth begins by having good crude assay data. The identification of chemical and physical properties of crude oil provides the basis for economic valuation, engineering design and refinery processing.
Why Characterize Crude Oils?
Crude grades vary considerably from each other - in yield and properties. Crude characterization is essential to estimate feedstock properties for refinery units, produce an optimal amount of finished products, meet product quality specifications and to provide an economic assessment for crude oils. The value of any particular crude depends upon the specific product slate and refinery configuration. Users can gain a competitive advantage utilizing the best quality information.
Crude oil data is utilized by:
Upstream Planning - to determine the economic viability of new fields / discoveries
Supply Organizations - to assign crude value for individual grades
Refinery Operations - to schedule crude receipts and determine product yields
Model Engineers - to optimize refinery crude slates
Research & Development - to design equipment and process planning
What is a Crude Assay?
A crude assay is a detailed report which describes the properties of the whole crude, as well as the major fractions into which a crude is distilled at the refinery - gasoline, naphtha, kerosene, jet fuel, middle distillates, gas oils and resid.

Typically, the data contained in a crude assay includes yields generated from the physical distillation or simulated distillation, specific gravity, gas chromatographic components, sulfur, nitrogen, viscosity, cold flow (pour point, cloud point, freeze point), conradson carbon, refractive index, aniline point, basic nitrogen, neutralization number, metals, and asphalt tests (e.g. penetration and softening point).

Having a laboratory conduct the tests detailed above is only the beginning of the evaluation process. Distillation and property balances need to be performed and re-prediction of measured data verified to allow accurate assessment of the crude's economic potential. Special situations, such as cracking, must be identified and data adjustments made. Not properly performing any of the critical assay correlation / validation steps may result in misleading assay results. Ensuring that the data is internally consistent is a crucial step - but not one that many oil companies perform!

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