Mechanical Analysis For Ultra-deep Water Drilling Risers Based On Numerical Simulation With ANSYS

The Ocean accounted for nearly3/4of the surface area of the Earth.The amount of proven marine oil resources has reserves of about34%of total global oil resources,and marine proven rate was only30%.The statistics also shows that the80%proven marine oil and gas Stored in the depth of more than1000meters. Therefore, to get the oil and gas resources from the ocean, we have to face the complex deepwater and ultra-deepwater marine environment. Drilling riser is the connection catheter system between the offshore oil and gas drilling platform and subsea wellheads. Its main function is to isolate the sea water, to provide a channel for circulation of drilling fluid,,to support auxiliary pipe line and so on. At present,deepwater drilling riser system design and analysis techniques is mastered only by a few companies, such as OPR, INTEC, Saipem, IP Kenny, Technip, MCS, Hoffshor,etc. Only several large marine engineering company in the United States, Norway, Japan,Brazil have the ability make the drilling riser. In order to speed up the development of China’s marine industry and to improve Chinese deepwater and ultra-deepwater drilling riser design capabilities, the current studies on marine drilling riser system is very blooming in china.Based on the research results at home and abroad,this paper has studied the mechanical response of the ultra-deepwater drilling riser system.The research contents include:marine environmental loads; the geometry non-linear characteristics of the ultra-deepwater drilling riser; the establishment of the geometric nonlinear Finite Element static and dynamic analysis model;static analysis with ANSYS software; the main environmental load parameter sensitivity analysis based on Static model; modal analysis and VIV profile. From the research we get the following results:the maximum of the ultra-deepwater drilling riser deformation and internal force locate near the surface of the water, so that,the bending, shear, tensile carrying capacity should be increased near the surface of the water; the carrying capacity of drilling riser close to the seabed should also be increased due to the increase of the internal forces at the riser; the riser displacements and internal forces increase with the increase of surface fluid velocity, wave height or wave period, and the influence of surface velocity is the most obvious;with the increase of initial value of the platform displacement(-30m to30m), riser displacement increases, but the internal force decreases; with the increase of water depth, riser displacements and internal forces both increase, and the influence of ocean currents is more and more important. These results can help us to achieve a better understanding of riser system and can provide reference for the stiffness and strength design of ultra-deepwater drilling risers. This research is important to the development of marine oil and gas industry.