Conceptual design and numerical analysis of a novel platform for marginal oilfields development

Abstract

Abstract A novel platform named Multi-Cylinder Concrete Production Storage and Offloading System (MCPSO) is proposed for the marginal oilfield development. It is constructed by multiple materials, including concrete and steel. The outer tank is constructed by concrete, and the steel is adopted for the internal tank, which is used for oil storage and water ballast. This design takes the advantages of the structure as well as the materials. The suction piles are adopted as the anchor foundation, which make the platform easy to install and reuse. Both structural and hydrodynamic models of MCPSO are established by finite element method (FEM). Firstly, the mesh independence study is performed to ensure the calculation accuracy. As the tensile strength of concrete is much lower than that of compressive strength, a series of return periods are selected to analyze the tensile stress of the structure. Then, the distributions and extreme value of stress are studied. Furthermore, adjustments of platform parameters are taken to illustrate and study influence factors of high stress distribution. Results show that there is no obvious interaction between the concrete outer tank and the steel internal tank, and the conceptual design of double layer tank ensures that the stress transmission of internal and external tanks is clear. According to the structural analysis, the wave load may induce increasing tension on the concrete tanks, while extension bar as well as waterline shape have influence on the distribution of high tensile stress. Therefore, reasonable adjustments of waterline shape should be taken to reduce the wave force pressure on platform.