Experimental study of solid deposition and vapor pressure in gas-to-liquid and crude oil mixtures for trasportation through the Trans Alaska Pipeline System

Abstract

Chemical conversion of Alaska North Slope (ANS) gas to liquid and subsequently transporting it through the Trans Alaska Pipeline System (TAPS) is a means of bringing the ANS gas to the market. However, transporting the gas-to-liquid (GTL) product with ANS crude oil through the Trans Alaska Pipeline System (TAPS) may pose some operational challenges. The major issue of concern relates to the asphaltene and wax deposition problems in the pipeline, as well as the vapor pressure of GTL and GTL/crude oil blends. In this study, experiments were carried out to determine the degree to which GTL is a flocculant of asphaltene. The stability/instability of the ANS crude to asphaltene deposition, as well as the wax appearance temperature of various cuts of GTL and GTL/crude oil blends were also determined. The results show that GTL is a possible flocculant of asphaltene, however, ANS is stable to asphaltene deposition. The results also show that GTL has a high wax appearance temperature, which raises a concern under arctic conditions. The Reid vapor pressure test results from this study show no consistent trend. This is because the GTL samples used have been flashed already as a result of sample withdrawal from the container by previous researchers. Thus the sample did not meet both the ASTM and IP requirements for Reid vapor test.