Analysis and Design of Wallhead Jacket Offshore Plateform

Abstract

Offshore structures are used worldwide for a variety of functions and in a variety of water depths, and environments. Offshore platforms serve artificial bases, supporting drilling and production facilities above the elevation of waves for oil extraction. The most commonly used offshore platforms are made of steel, and are used for oil/gas exploration and production. The Primary aim of study is to understand the loading conditions for the offshore structures and to carry out the analysis of jackets subjected to various loads like non generated load, wave load, wind load, earthquake load, and current load. The present study is concerned with the structural analysis and design of a fixed offshore steel jacket platform that is to be deployed in the Western offshore of India, for a chart datum water depth of 73.75 m. The platform is a Wellhead Platform (WHP), with six conductors. A wellhead jacket platform is designed for the western offshore condition and its jacket part is analyzed for its structural integrity based on the offshore oil industry standards and requirements under various load conditions. The analysis includes check for stability, yield, punching shear and fatigue life, based on the soil–pile–structure interactive analysis. The study includes comparative study of wave force computation by Morison equation based on Stokes fifth order wave theory. The process of selection of a wave theory for a particular location is worked out; a discussion is made on their applicability and suitability, and based on this the selection of Stokes fifth order wave theory for the analysis of the above mentioned platform is justified. Modeling and analysis of the jacket portion is done in SAP-2000 considering environmental & non generated load. The project consists of the static analysis including the fatigue analysis for checking the structural integrity of the Wellhead platform (WHP). The in-place static analysis including fatigue analysis based on working stress method is carried out using SAP-2000 software. All the joints of the platform are welded joints which are designed for fluctuating loads. The pile foundation of the wellhead jacket platform is designed for the western offshore soil conditions under axial and lateral load.