Study on Effect of Insulation Design on Thermal-Hydraulic Analysis: An Important Aspect in Subsea Pipeline Designing

Abstract

The most imperative and challenging operational hazards for oil and gas pipelines are the risks associated with the transportation of fluids. When water, oil and gas flow simultaneously inside the pipeline, there are quite high chances that, water and hydrocarbon fluids can form and deposit hydrate such as wax and asphaltene on the inner surfaces of the pipeline and gradually blocking it. In this paper we explore and compare the various types of insulation and to find the optimum thickness of insulation required to maintain the temperature of the fluid inside the pipeline, above the hydrate/wax formation temperature to ensure smooth flow.  Presence of high water cut, changes in pressure and temperature along the pipeline leads to internal corrosion. Also because of incompatible water mixing, scales may form and get deposited inside the pipeline and restrict the flow hence, causing operational problems to downstream processing facilities. The key challenge faced by engineers is how to design a pipeline to assure that multiphase fluids are be safely and economically transported from the reservoir all the way to the downstream processing plants and the end users. The complete knowledge of dynamic fluid properties and a proper thermal-hydraulic analysis of the system are required to develop strategies for controlling the solids such as hydrates, wax and asphaltenes, and sometimes scale and sand. The practice of identifying, quantifying, and mitigating of most of the flow risks associated with pipelines, specifically subsea systems, is called flow assurance. The knowledge of fluid properties and thermal-hydraulic analysis of the system is utilized is essential  to develop a concept or strategies for controlling the formation of solids such as hydrates, wax, asphaltenes, and scale from the system. Flow assurance refers to ensuring the flow of produced hydrocarbons from the reservoir to the processing facility or to the point of sale. In this work, an Excel spreadsheet calculation comparison has been done to see the effect of various insulation material with different thicknesses on the temperature profile of the fluid in deep water environment. The hydrate and wax formation temperatures is first known and critical radius of insulation is calculated to obtained the required thickness of insulation in order to mitigate cool down of the fluid.

Keywords: Flow assurance, Hydrates, Wax, Asphaltenes, Thermal insulation thickness