Abstract
Gas-to-Liquid (GTL) conversion is an emerging technology that will very likely reach widespread commercialization within the next decade. Given the vast natural gas resources of the Alaskan North Slope (ANS), it will be one of the first areas in the United States to exploit this new technology. Conversion of natural gas to liquid products on a commercial scale will also facilitate potential transportation of such liquids through the existing infrastructure, namely, the Trans Alaska Pipeline System (TAPS). This could very well obviate the need for developing costly alternatives for transportation of the remote ANS gas.
The objective of this study is to evaluate the technical and economic feasibility of transporting GTL products through TAPS. The extreme arctic environment surrounding TAPS creates the unique transportation issue of cold restart of the pipeline following an extended winter shutdown. Fluid property measurements including low temperature gel strength of GTL and GTL-crude oil blends were conducted to assess the feasibility of cold restart for a varying range of throughput types. Several of the GTL samples exhibited rather high gel strengths at temperatures relatively warm by arctic standards. Thus, the results of the study can be used to provide initial guidelines for the type of GTL to be produced at ANS.
There are two possible modes of transporting GTL products through TAPS: (i) batch mode, where GTL and crude oil flow as alternate slugs, and (ii) commingled mode, where GTL and crude oil are mixed to form a single phase. A preliminary economic analysis of the two modes of transportation, including hydraulic modeling of batch and commingled flow modes, indicated that the batch mode would be more economical than the commingled mode.
