Introduction to Flexible Risers

What is/are Flexible Risers?

Flexible Risers - This paper presents the development of an automated inspection system for flexible risers that are used to connect wellheads on the seafloor to the offshore production and storage facility. ^[1] Failure of flexible risers can occur, among several factors, due to their cold drawn carbon steel tensile armor wires collapse. ^[2] During the installation of marine flexible pipelines, components, such as flexible risers, umbilicals, and cables, subject to wave motion and ship yaw can cause torque on such pipelines. ^[3] Purpose The inspection of flexible risers is a critical activity to ensure continuous productivity and safety in oil and gas production. ^[4] Flexible risers are designed with strong anti-collapse capacities which enable them to operate in deep-water reservoirs. ^[5] A real-time understanding of the structural integrity of flexible risers is critical to avoiding failures as well as unnecessary and costly replacements. ^[6] The flexible risers, usually installed in lazy wave configurations at such water depths, were optimized reducing the total buoyancy necessary. ^[7] Flexible risers have been widely utilized for the transfer of oil and gas products from a well to production units. ^[8] Flexible risers are widely employed in deep-sea oil and gas development. ^[9] In recent years, the dynamic responses of flexible risers have been the focus of many researchers. ^[10] For flexible risers, this competitiveness will become even more prominent. ^[11] Fatigue life of flexible risers is a critical design factor in offshore riser system design. ^[12] Calculating the wet collapse pressure of flexible risers is always challenging since the layers within risers are different in geometries and materials. ^[13] The helically wound structure is widely applied in ocean and civil engineering as load-bearing structures with high flexibility, such as wire ropes, umbilical cables and flexible risers. ^[14] Apart from the vortex-induced vibration (VIV) caused by flow over flexible risers, internal slug flow-induced vibration (FIV) is extensively encountered in practice as risers are conveying oil–gas two-phase flow. ^[15] The storm-based probabilistic analysis is applied to responses of flexible risers with the objective to develop their distributions in a storm and to determine their most probable maximum (MPM) values. ^[16] In this study, numerical models of two kinds of flexible risers, namely, catenary riser and lazy wave riser, are established in OrcaFlex software. ^[17] In this study, an efficient time-domain prediction model is developed to predict unsteady flow vortex-induced vibrations (VIV) of flexible risers. ^[18] The complexity of these flexible risers and the hostile conditions in a deep-water environment present major challenges for non-intrusive, in-service inspection. ^[19] Flow-induced pulsations in flexible risers and flowlines (FLIP) has been the subject of ongoing research roughly over the last two decades. ^[20] A dynamic analysis of flexible risers in large-scale domain remains the offshore industry’s most challenging problems. ^[21] This paper presents a two-dimensional parametric analysis of the influence of an internal slug flow on the structural dynamic response of flexible risers. ^[22] As water depths for oil and gas exploration and extraction increase, structures such as flexible risers, mooring lines, and umbilical cables are increasingly being used for subsea environments. ^[23]

vortex induced vibration

Under the actions of ocean currents and/or waves, deep-sea flexible risers are often subject to vortex-induced vibration (VIV). ^[1] As an important component transporting resources such as oil and mineral ores mixture from the seabed to the surface in ocean engineering, vortex-induced vibration (VIV) of flexible risers can be encountered when the risers are subjected to the external environmental conditions. ^[2]

Unbonded Flexible Risers

Interlocked armor layers of unbonded flexible risers may crush when risers are being launched. ^[1] Nevertheless, detailed understanding of local armor wire stresses and the related fatigue phenomena is of paramount importance as unbonded flexible risers are often operated close to their mechanical limits. ^[2] ABSTRACT Unbonded flexible risers have been applied in the harsh environment for several decades, and structural failure sometimes appears. ^[3]

Sea Flexible Risers

With the development of deep-sea oil and gas resources, the aspect ratio of deep-sea flexible riser has reached the order of 102–103, which makes the experimental model of the equal scale of deep-sea flexible risers challenging to achieve under typical experimental conditions. ^[1] Under the actions of ocean currents and/or waves, deep-sea flexible risers are often subject to vortex-induced vibration (VIV). ^[2]