Static analysis of deep-water marine riser subjected to both axial and lateral forces in its installation

Abstract

In order to analyze riser stress and deformation in its installation, a static analysis model and equation have been established and the equation is solved by the finite difference method. In this model, the riser is regarded as a beam suspended in the floating drilling platform (ship) and subjected to both axial and lateral forces. In order to connect the Blowout Preventer Stack (BOPS) and the subsea wellhead, the floating drilling platform (ship) needs to move to drag the riser and BOPS. However, during the movement of floating drilling platform (ship), the riser stress distribution will change. The total stress variation with the movement speed of floating drilling platform (ship) has been figured out. Because riser deformation could be affected by several operational factors and environmental factors, the deformation variation with water depth, riser size, BOPS weight, sea surface wind velocity, sea surface tide velocity, wave height and wave period are discussed. Results show that there is a maximum movement speed of floating drilling platform (ship). If the actual speed is greater than the maximum value, the riser material will be in danger of damage. The riser deformation will increase as water depth, sea surface wind velocity and sea tide velocity increase and will decrease as riser size and BOPS weight increase. However, wave height and wave period almost have no impact on riser deformation. Since the analysis model established is a static one, the dynamic problem is not discussed in this paper.