Institute of Petroleum Engineering

Centre for Gas Hydrate Research Publications

Abstract 044
A Consistent Thermodynamic Model for Predicting Combined Wax-Hydrate in Petroleum Reservoir Fluids
Tabatabaei, A.R., Danesh, A., Tohidi, B., and Todd, A. C.
Annals of the New York Academy of Sciences, 912, 392-402 (2000).
Low oil prices and competitive nature of the oil industry worldwide demands more cost-effective techniques in development and operation of offshore reservoirs. Extended-reach gathering networks and transportation of unprocessed wellstreams by subsea pipelines are two attractive options, which could have significant impact in the development of marginal oil/gas fields. These subsea pipelines are prone to wax and/or hydrate formation which could potentially block the pipelines and lead to serious safety and operational problems. Wax and hydrate formations are both solid deposition. They are conventionally modelled and studied independently. In this work a wax model has been developed based on regular solution theory. The wax model was then successfully coupled with an existing hydrate model. The integrated wax-hydrate model is capable of predicting five phase equilibria (i.e., water, liquid hydrocarbon, vapour, wax and hydrate) as well as predicting the effect of wax formation on hydrates phase boundary and vice versa. The results showed that a reliable wax-hydrate model could minimise the risks involved in the transportation of fluids prone to wax and hydrates formation. The model could be used as a powerful tool in the design and operation of subsea and arctic pipelines and production facilities.

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