SARA Heavy Oil Analysis

SARA oil testing measures saturates, asphaltenes, resins, aromatics in heavy crude oil, distillates and feedstocks.

Intertek tests hydrocarbon samples for Saturates, Asphaltenes, Resins and Aromatics (SARA). SARA analysis of heavy crudes is done for heavy oils, including vacuum distillates, atmospheric and vacuum residues, bitumens, and asphalts, so that material losses from light ends (volatiles) are minimal.

Conventional crude oils can be topped (>300 degC) prior to SARA to reduce light end losses in the subsequent separation and allow the <300 degC distillate to be analysed by other methods. Heavy or biodegraded crudes with few light ends can be analysed directly.

SARA analysis is used for many components of crude oil. Asphaltenes can be pentane or heptane insolubles. Resins may be classified as a solubility fractions, such as heptane soluble and pentane insoluble or heptane soluble and acetone or ethyl acetate insoluble, or as the polar fraction eluted from a polar adsorbent with a polar solvent, such as pyridine, toluene or methanol.

Saturates and Aromatics are determined by adsorption chromatography, typically from silica or silica/alumina. Saturates are eluted with a paraffinic solvent, such as pentane or heptane. Aromatics are eluted either with paraffinic or moderately polar solvents, such as toluene or DCM.

If the SARA test sample is a heavy oil with minimal light ends, it is worth considering Iatroscan TLC-FID for which there is a standard method (IP-469). IP-469 determines all four compound classes by adsorption chromatography, so the asphaltenes content may differ numerically to that determined by IP-143. Typically, Iatroscan asphaltenes are about 80 % of the IP-143 asphaltenes.

Measuring Asphaltenes by IP-143 and then determine SAR by IP-469 is possible. IP-469 does not involve a gravimetric finish, and light ends are still lost during the analysis, so this method works best with >300 degC distillates or residues.

Other SARA analysis alternatives including IP 143 followed by preparative HPLC (IP-368), or Clay-Gel (ASTM D-2007), which may be appropriate. SARA is also described as Asphaltene/Wax/Hydrate Deposition analysis.

Contact us to see how Intertek can help your organization with SARA Heavy Oil Analysis.