Comparative Compositional Study of Crude Oil Solids from the Trans Alaska Pipeline System Using High-Temperature Gas Chromatography

Abstract

Wax precipitation and deposition in crude oils can produce problems in production and transportation operations. To gain an understanding of deposits formed in a pipeline transporting an intermediate type crude oil in an arctic/subarctic environment, comparisons of several types of crude oil solid deposits from the Trans Alaska Pipeline System (TAPS) and precipitated waxes present in the TAPS mix crude oil were developed. An extended high-temperature gas chromatography (HTGC) method was used for the determination of the solids composition, and is described in this paper. The HTGC method uses a longer capillary column to obtain improved resolution of higher carbon number groups. The method also provides quantification of n-alkane and non-n-alkane content within each single carbon number group. A comparison of the ratio of n-alkane: non-n-alkane for each single carbon number (SCN) between the parent crude oil and the crude oil solids is used to identify the amount of liquid crude oil occluded in the crude oil solid. A reference wax is analyzed using the described method to demonstrate the precision and accuracy of the method.

Gas Chromatograph Applications in Petroleum Hydrocarbon Fluids

“…A longer capillary column was used to achieve an improved resolution of high carbon number groups. The n-alkane/non-n-alkane ratio was used to distinguish between certain types of crude oil solids (Roehner et al, 2002).…”

Experimental and Modeling Studies of Wax Deposition in Crude-Oil-Carrying Pipelines

“…A HTGC-SIMDIS procedure [2] developed at PERC, University of Utah based on the ASTM D-5307 test method [3] was used to obtain a carbon number distribution of the model oil.…”

“…Wax particle size distribution (PSD) was not measured in this study. Reported median wax particle diameters measured under static conditions are of the order of a micron [6,7]. However, smaller particles in the 'tail' of the PSD can be expected and be held responsible for Brownian diffusion.…”

Comparison of Motor Oils Using High‐Temperature Gas Chromatography‐Mass Spectrometry

“…A combination of HTGC, IR, and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) was used to differentiate oil-based lubricants for weapons (13). Roehner et al (14) used HTGC to compare crude oil samples. HTGC has also been used to distinguish between commercial waxes (15), waxes in artificial fireplace logs (16), and process oils in Composition C-4 (17).…”