Novel Design, Hydrodynamics and Mechanics of Marine Hoses in Oil/Gas Applications

Amaechi, Chiemela Victor and Ye, Jianqiao (2022) Novel Design, Hydrodynamics and Mechanics of Marine Hoses in Oil/Gas Applications. PhD thesis, Lancaster University.

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Abstract

Due to recent challenges in oil exploration, there has been an increase in oil exploration from shallow waters to deep waters. This requires more length of the risers and thus an increase in the weight of the risers on the offshore structure. Secondly, there is the need for the application of more flexible structures like marine hose systems. Marine hoses are unique marine riser systems which are utilised as conduits to transport fluid from the oil well to the offshore platform of the transport vessel. Marine hoses are also a type of bonded flexible risers that are connected to buoys and other offshore structures but have short service periods. Three types of marine hoses are researched-submarine hoses, floating hoses and reeling hoses. The design for some load cases on the marine hoses is presented. The advantages and brief on state-of-the-art of marine hose structures for deep water applications are presented. Increasing energy needs has also led to advances in ocean monitoring, offloading and loading operations based on the use of Catenary Anchor Leg Moorings (CALM) buoys. However, variations in the soil stiffness and environmental conditions necessitates the investigation on the behaviour of marine hoses, based on the mechanics, structural and hydrodynamic behaviour. In this study, the local design and global design analysis of marine hoses layers were designed. In the numerical modelling, comparisons were made using two (2) configurations- the Lazy-S and Chinese-lantern configurations. However, a new hybrid hose riser configuration was also proposed for the application of marine hoses. Also, some parametric studies on the effect of the buoy shape, and buoy skirt were conducted. A novel coupling model was also proposed whereby hydrodynamic simulation using ANSYS AQWA was first conducted and later coupled into the dynamic models in Orcaflex. Based on the case study with marine hoses, the dynamic analysis was carried out based on the design of the submarine hoses attached to a CALM buoy using six (6) mooring lines. Experimental work conducted in Lancaster University Wave Tank was also presented using a CALM buoy model. In the wave tank, the motion response of a scaled hull model was investigated using two (2) novel underwater Bluetooth MIT motion sensors, two (2) underwater Akaso 4K cameras, and the Imetrum Digital Image Correlation (DIC) system. A series of hydrodynamic models were created in ANSYS AQWA using environmental conditions specified by API, ABS and DNV to further examine its application for additional ocean depths and support systems. The Imetrum system results from the wave tank experimental test were used to validate the AQWA model. Results on the effect of wave height, flow angles, soil stiffness and hydrodynamic loads on the structural behaviour of the submarine hoses and composite risers were presented with recommendations. The global analysis carried out on a CALM buoy using these configurations, could be considered in (WA) Weight-added risers, Top Tension Risers (TTR) and a lazywave riser (LWR) formations. The research result shows novel numerical modelling approaches for the design, hydrodynamics and mechanics of marine hoses for oil and gas applications.