Study On Interaction Between Steel Catenary Risers Touchdown Zone And The Seabed

With the rapid development of the global economy, the demand for fossil fuels such as oil and natural gas is growing, and the exploitation of land and offshore oil and gas has been unable to meet the growing demand for production and life. In recent years, the rapid reform of offshore oil and gas production technology, offshore oil and gas exploration gradually to deep water(500m-1500m), ultra deep water(water depth greater than 1500m)field. Steel catenary riser(SCR) as a chose of deepwater oil and gas development and has a good adaptability to environment and low cost.The typical SCR consists of a suspension section and a flow line segment. Due to the movement of the upper structure and the influence of the marine environment, the touchdown point of the riser is constantly moving, and interaction with the seabed repeated,which is easy to cause the fatigue failure of the vertical pipe contact area. The mechanism of the interaction between the soil and the area and the fatigue analysis is a hot issue in the engineering field.In this paper, the progress of SCR pipe soil interaction numerical analysis and experimental research in recent years and the achievements and shortcomings of the research are summarized. Analysis of the riser environment in which the sea condition,the action of the wave, current and other marine loads on the riser and floating body are introduced,the calculation method of different loads is described in detail; By using the ABAQUS and OrcaFlex simulation of the installation process to get an initial accuracy static riser installation form, and with through conventional catenary shape theoretical calculation comparing the various methods of analysis; By marine riser dedicated software for simple dynamic analysis, to get the riser fatigue region; Then introduced the pipe soil interaction numerical model, which of the various parameters are introduced. Based on,carry out riser overall dynamic analysis, analysis the effect of different parameters such the strength of soil, the wave height of the sea which the upper floating body in on riser penetration depth of seabed, the displacement history of penetration deepest node, the change of the bending moment and stress in the longitudinal direction of the riser; Finally,design two set of simple pipe-soil experimental facilities, carry out small-scale model test,more intuitive observation pipe-soil interaction. The first set of equipment for the global dynamic analysis of the riser, through the OrcaFlex software to verify the test results to prove the accuracy of the test equipment. Second sets of equipment in the area of the contact area for local analysis, analysis of different movement patterns, the movement cycle and other areas of the impact of the stress of the area.