Cold Flow Technical and Cost Efficiency Analysis
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Nowadays, subsea multiphase pipelines are commonly used in the deepwater oil-gas fields all over the world. However, when operating at such complex deepwater conditions, the problem of solid precipitation arises due to increased pressures and lower temperatures, as well as the increased distances between processing units. Thus, deepwater flow assurance has become a major focus of the international oil and gas field developments. Hydrates are one of the major precipitates which have to be controlled in order to assure deepwater flow assurance. There are several methods for hydrate control in the industry today. However, as the industry is moving towards more remote areas, many of these methods have proven to be impractical in one way or the other. Hydrate risk management is a newer approach for dealing with hydrates, which allows for hydrate formation under carefully controlled circumstances. One of the most recent ideas for hydrate risk management is the dry cold flow technology developed by SINTEF. By simple design and installation, this innovative technology could potentially change the way of dealing with hydrates, especially when considering a financial point of view. In order to achieve optimal design, it is essential to understand how different factors influence the efficiency of the cold flow technology. SINTEF's SATURN cold flow simulator was applied in order to simulate different scenarios realistic for the Barents Sea and the Goliat field. The influencing factors studied included well stream and recirculation stream temperature, water cut and flow velocity for different pipe diameters. An economical study of common hydrate control and risk management methods was performed in order to illustrate the potential financial benefits of cold flow technology. From this, a sensitivity analysis with respect to tieback distance and expected field life was completed. It was found that the potential cost savings associated with cold flow are significant, especially for long tieback distances and when the expected field life is long. From this study, it was found that a system of six 8 inch pipes was the most cost effective solution for the base case. However, considering a technical perspective, a system of forty-one 3 inch pipes was preferred.