Hydrate-free zone for synthetic and real reservoir fluids in the presence of saline water

The application of extended-reach subsea gathering networks and transportation of unprocessed wellstreams are serious considerations for reducing field development costs. These lines will convey a mixture of gaseous and/or liquid hydrocarbons, condensed or saline water. A good knowledge of the hydrate phase boundary for the above systems is essential in the confident and economical design and operation of associated fields, pipelines and processing facilities. In this paper, experimental data for the hydrate-free zone of several pure and multicomponent systems in the presence of single and mixed electrolyte solutions are presented. The paper, which is a continuation of three previous communications, presents data on C-2, C-3, CO2, two synthetic multicomponent gas mixtures, and a black oil sample. The comparison of results with recent literature data shows some discrepancy at high salt concentrations, where a possible source of error is identified. An in-house numerical model has been used for predicting the experimental data with good results. (C) 1997 Elsevier Science Ltd.