Integrated method for layout design of LNG FPSO based on optimization technique and expert system

Abstract

The LNG FPSO is a large structure on the sea with facilities for gas and oil production, and it can be divided into hull and topside. Such facilities are grouped into several units called modules and distributed on the topside. Also, many kinds of storage tanks are arranged in the hull. The design for the offshore platform is an elaborate and difficult task because it requires many considerations such as international codes and standards, owners requirements, operation and maintenance philosophy, and so on. At the beginning of the design, it depends heavily on designer's experience and reference projects. In this study, the integrated design framework for LNG FPSO is proposed to obtain the optimal hull sizing, tank arrangement in the hull, module layout in the topside, and equipment layout in the topside modules that satisfy many requirements regarding safety, economics, operability, and stability. The proposed framework consists of four components. First, the expert system is applied to computerize experts knowledge and experience systematically and to evaluate the feasibility of alternatives for the overall design of the offshore platform. Second, the optimization method is used to yield a better design by formulating the design problem as an optimization problem with a single stage. Third, an arrangement template model is used to store the arrangement data of offshore platform. Fourth, the user interface is developed to the integrated design of the offshore platform by executing the proposed framework. A prototype program is developed to evaluate the applicability of the proposed framework. This method was applied to the example of an LNG FPSO to verify the method, and the result shows that the proposed framework could be used for finding a better arrangement and improve the work efficiency of the design process for the offshore platform at the initial design stage.