The ability to rapidly and accurately evaluate the variability of distillation yield curves of opportunistic crudes and crudes from currently producing fields has increasingly important economic considerations in refining margins. Recent advances in the analytical laboratory using gas chromatography techniques have allowed the method of High Temperature Simulated Distillation (HTSD) to be successfully used in place of the laboratory method of Crude Assay Distillation (ASTM D2892 and D5236). This paper presents a brief description of the HTSD analysis (including detailed precision data) and the HTSD yield curve correlations to Crude Assay distillations for a variety of crudes. By knowing the statistical significance of the HTSD data generated and the correlation to existing crude assay, marginal values of various crudes can be derived and the economics evaluated.
In this study, approximately 100 crudes were analyzed by Crude Assay Distillation and HTSD. To allow a meaningful comparison of the yield curves obtained by Crude Assay Distillation and HTSD, the crudes were grouped into light, intermediate, and heavy categories by API gravity. The yield curves are compared at 10 distillation cutpoints. At each cutpoint, the average percent weight (%weight) differences between Crude Assay Distillation and HTSD are summarized for each API Gravity grouping. In addition, the estimated precision of the correlation between Crude Assay Distillation and HTSD at each distillation cutpoint is presented.
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