Modeling and development of insulation materials in subsea pipelines

Ahmed, Ibrahim Masaud (2018) Modeling and development of insulation materials in subsea pipelines. Masters thesis, Memorial University of Newfoundland.

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Abstract

Flow assurance is a major issue in subsea pipelines that transport crude oil and gas. Thermal insulation is crucial in preventing and controlling the formation of hydrates, asphalt or wax that can block flowlines. Heavy components of crude oil begin to form as hydrates, asphalt and wax at low flow temperature. In addition, high pressure and low temperature start the formation of hydrates, asphalt and wax in gas pipelines. When the temperature of crude oil decreases due to increase in its viscosity in a flowline, this causes an increase in pump power consumption. This research includes analysis of heat loss, temperature profiles in steady state flows, and temperature profiles in transient flows of the startup mode for transporting crude oil in deep water pipelines. The research focuses on temperature profiles that use several thicknesses of materials. The methodology used is a Matlab program. Firstly, the program validates the results for the unchanging geometry and thermal properties of the materials, to investigate temperature profiles during the start-up of crude oil along the length of the pipeline. The calculation has achieved approximate results. Then the model uses new insulation materials, crude oil, temperature, inner diameter and outer diameter for the same length of the pipeline. Moreover, this research has investigated the cool down time for flow shutdown of crude oil in pipelines, which is a primary issue in the production of offshore oil and gas. Cool down time is considered for two cases, which are exposed insulation pipelines in seawater and insulated pipeline buried under seawater. The research uses ANSYS Fluent CFD for sample runs of the models to validate the Matlab program output. The ANSYS Fluent focuses on steady state and transient flow temperature profiles during crude oil start-up, and examines the effects of several insulation thicknesses and the low thermal conductivity of materials.

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