Compared to the relatively high concentrations of nC10 - 20 in crude oils and gas condensates [analysed as unadulterated “Whole” sample] the concentrations of >nC30 can be relatively low and either close to or below the limit of detection / quantification of the HTGC system. This is especially true for >nC50 and means that the values reported for these heavier n-alkanes may not have the same degree of accuracy as lower molecular weight n-alkanes, or cannot be accurately determined at all.


To mitigate this problem the < nC15 fraction is typically removed through an evaporation “Topping” procedure which, in effect, concentrates the >nC20 fraction so that, even at the high end, peak areas can be more accurately determined.


Results for “Whole” and “Topped” samples are then merged by normalising the results from the “Topped” fraction based on the area of a peak present in sufficient quantities in the “Whole” sample for an accurate reading to be obtained (i.e., above the limit of detection).


T-SEP® is a proprietary, small scale, thermal separation technique that has been developed by KAT in partnership with the University of Plymouth, primarily as a novel “Topping” method for crude oil and condensate samples although it is also applicable to several other processes.


This technology enables precise control over the “Topping” process and is more reproducible and effective than the simple evaporation techniques employed by most laboratories, allowing on average an additional 20 carbon numbers to be observed and accurately measured.

n-Paraffin Weight Distributions With and Without T-SEP® Enhanced Sample Preparation

In addition to extending the analysis of the parent hydrocarbon fluids, T-SEP® is regularly used to enhance the analysis of associated deposits and has been used in the semi-quantitative fingerprinting of semi-solid tar-balls.