Solids Deposition from Paraffinic Mixtures: Investigation of 'Cold Flow' in Pipelines

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Most energy consumption forecasts suggest a continued growth in the worldwide petroleum demand. However, new crude oil reservoirs are deep, located offshore and contain heavy oils, with complex and costly infrastructure and operations. One serious challenge with deep-water petroleum production is the solids or wax deposition, which is known to cause plugging of pipelines and process equipment, requiring hundreds of millions of dollars annually for its control and remediation. Pipelines are known to have been abandoned because of becoming plugged with wax deposit. Wax deposition is a complex process, involving liquid-to-solid phase transformation of paraffins, which is influenced by cooling or crystallization rates, shear stress, the rate of heat transfer, and the oil composition.      The long-term objective of this research program is to develop simulation models and a novel software for solids deposition during pipeline flow and processing of 'waxy' (paraffinic) crude oils. The heat-transfer based approach developed in this research program is unique. Building on recent innovative accomplishments, the proposed research will focus on developing the 'cold flow' technology, which offers the benefit of much reduced levels of solids deposition. In the 'cold flow' regime, however, the fluid is actually a two-phase solid-liquid suspension created by the precipitated wax crystals, which would be expected to cause increased pressure drop across the pipeline.      A number of experimental and theoretical activities are proposed that involve phase transformation, solids deposition and thermophysical and transport properties of systems comprising heavy hydrocarbons. The research will involve experimentation, statistical analysis, and model development. Over the next 5 years, NSERC DG will be used to provide training to at least 10 HQPs (2 PhD, 3 MSc and 5 BSc students).      The research methodology involves experiments with defined mixtures to provide improved understanding of the basic processes, which will aid in the validation of new mathematical models. A rigorous heat-transfer based solids deposition model will be developed for simulating both laminar and turbulent flow under a wide range of operating conditions as well as for pipeline start-up and shutdown. The model development research will be augmented by experimental and theoretical studies, including solid deposition in bench-scale flow loop and cold finger apparatus (operated at temperatures below the wax appearance temperature), phase transformation, rheological behavior of the deposit, alternate mechanisms for deposit aging and sloughing phenomena, deposit thermal conductivity, etc. The developed software, incorporating validated mathematical models, will be used by the flow assurance groups of petroleum companies for tackling major challenges associated with solids deposition in a sustainable and cost-effective manner.