Deepwater drilling riser system together constitute the channel connecting the drilling platform and underground reservoir, which plays an important role in the offshore oil and gas development. A coupling strength analysis model for drilling riser and subsea wellhead was proposed under extreme environment condition. A stack-up for drilling riser system under 3000m water depth is established and safety operation criteria for the drilling riser system is proposed. The global dynamic analysis under extreme wave and current environmental load is conducted. The results of effective tension, bending moment, and equivalent stress of the riser system under different waves and currents are discussed and an operation window for the drilling rise is presented. The research for 3000m WD deepwater drilling riser system can provide valuable reference for ultra-deepwater drilling engineering in the development of oil and gas fields.
Although the exploration and development of offshore oil and gas have brought huge benefits, there are also enormous risks in the development process (Mao et al, 2020; Wang et al, 2021; Wang, 2022). The deepwater oil and gas drilling in the ultra deep water field, ranging from 1500m to 3000m deep, has brought enormous challenges to ultra deep water drilling. Under ultra deep water conditions, due to harsh environment conditions, high construction difficulty, complex equipment, and uncontrollable factors such as sea winds, waves, and currents, deepwater oil development has become a high investment, high-tech, and high-risk industry (Sheng et al, 2019). The drilling riser is the throat connecting the offshore drilling platform and the subsea wellhead, and the ultra deepwater drilling riser faces more complex environmental load conditions. In deepwater or even ultra deepwater at depths of over 1.5 kilometer in the ocean, the diameter to length ratio of the riser reaches the range of slender flexible elastic bodies. The movement of the riser is manifested as flexible elastic motion rather than rigid body motion, resulting in a significant increase in the amplitude of the riser, which is prone to a series of problems such as fatigue damage, fracture, and leakage. The riser system with ultra length-diameter ratio faces more complex environmental loads and working conditions, with prominent nonlinear problems, complex coupling response mechanisms with subsea wellhead and conduit, and high operational risks.
