Numerical Investigation into Freak Wave Effects on Deepwater Pipeline Installation

Abstract

Freak waves are an extreme marine environment factor in offshore structure design and become a potential risk, particularly for laying oil-gas pipelines in deep waters. The objective of this study was to reveal the freak wave effects on dynamic behaviors of offshore pipelines for deepwater installation. Thus, a dedicated finite element model (FEM) for deepwater pipeline installation by the S-lay method was developed with special consideration of freak waves. The FEM also took pipelay vessel motions, pipe–stinger roller interactions, and the cyclic contacts between the pipeline and seabed soil into account. Real vessel and stinger data from an actual engineering project in the South China Sea were collected to obtain an accurate simulation. Moreover, an effective superposition approach of combined transient wave trains and random wave trains was introduced, and various types of freak wave trains were simulated. Extensive numerical analyses of a 12 inch gas pipeline being installed into a water depth of 1500 m were implemented under various freak wave conditions. The noticeable influences of freak waves on the pipeline and seabed responses were identified, which provides significant awareness of offshore pipelines for deepwater installation design and field operation monitoring.

Numerical Investigation into the Dynamic Responses of Floating Photovoltaic Platform and Mooring Line Structures under Freak Waves

“…The mechanical properties and motion states, such as the mass, buoyancy, and displacement of the mooring line, are concentrated on the adjacent mass nodes, while the tensile properties of the mooring line are characterized by the spring segment. To analyze the tension behavior of each spring segment, the force equilibrium equation can be established to calculate the effective tension of the spring segment for the mooring line, which is given by [15] T e = T w (ε…”

“…Li et al [14] investigated the influences of freak waves on semi-submersible platform motion and mooring stiffness. Xu et al [15] and Xu and Gong [16] numerically generated a series of freak waves and obtained the response behaviors of offshore pipelines for the installation stage under a freak wave. Pan et al [17] experimentally explored the influence of freak waves on the response characteristics of mooring square columns in the frequency domain.…”

Proper Use of Technical Standards in Offshore Petroleum Industry

“…Instead, through the product safety directives, drilling ships and oil and gas equipment onboard has been covered through the International Convention for the Safety of Life at Sea (SOLAS) and more specifically through the Code for the construction and equipment of Mobile Offshore Drilling Units of the International Maritime Organization (the MODU code). The MODU code has been developed to protect any ship as a vessel, and its integrity and stability in the first place in terms of navigation [32][33][34][35], emphasizing the additional requirements caused by drilling activities [36], but does not include requirements for the drilling of subsea wells or the procedures for their control (such drilling operations are subject to control by the coastal state). The MODU code is used in relation to the EU/EEA product safety directives as follows: (1) Protection against explosions; (2) Protection of pressure equipment; (3) Protection of personnel who works with machinery:…”

The Optimization of a Subsea Pipeline Installation Configuration Using a Genetic Algorithm

“…Subsea pipeline resilience can be defined as the pipeline's capacity to withstand manmade and natural hazards, and this resilience plays a significant role in the design process [3]. These hazards could include accidental pulling with fishing gear, damages caused by terrorist activity, earthquakes, extreme climate and environmental conditions and unforeseen installation or operational loads [4][5][6]. The increasing demand and growth of energy consumption affect the design and installation of ever-longer subsea pipelines at increasing depths.…”