No abstract

Hull and propeller performance have a primary role in overall vessel efficiency. Vessel fouling is a common phenomenon where undesirable substances attach or grow on the ship hull. A clear understanding of the extent of the degradation of the hull will allow better management of assets and prediction of the best time for dry docking and hull maintenance work. In this paper, the authors investigate the problems of predicting the hull condition in real operations based on data measured by the on-board systems. The proposed solution uses an unsupervised Machine Learning (ML) modelling technique to eliminate the need for collecting labeled data related to the hull and propeller fouling condition. Two anomaly detection methods based on Support Vector Machines and k-nearest neighbour have been applied to predict the hull condition using the available parameters measured on-board. Data from the Research Vessel The Princess Royal has been exploited to show the effectiveness of the proposed methods and to benchmark them in a realistic maritime application.

No abstract

Offshore wind energy development has gained considerable momentum around the world as wind is stronger and steadier offshore compared to land. This has led to a significant increase in production in recent years, especially offshore wind turbine embedded in shallow waters, such as the recent large scale offshore wind farms in the Northern Europe region. Being at the offshore waters, the wind turbines are subjected to harsh environment. The pile supporting the wind turbine must be reliable and able to withstand such sea condition. It is an important part of the design to study the structural behaviour of the piles under the wave loads. Due to the significant capital cost associated with the fabrication of the large circular cylinders, a new recommended innovative design to overcome such problem is to substitute the circular cylinder with a vertical monopile of octagonal cross-sectional shape. This paper describes the development of an efficient numerical model for structural analysis of wave interaction with octagonal pile using a modified semi analytical Scaled Boundary Finite Element Method (SBFEM). In contrast to the existing solutions obtained using the traditional methods such as the Finite Element Method (FEM) which typically suffer from high computational cost and the Boundary Element Method (BEM) which faces limitation from fundamental equations and problems with singularities. The most prominent advantage that SBFEM has over the FEM is in terms of the number of elements used for calculation and hence a reduction in computational time. When compared with BEM, the SBFEM does not suffer from computational stability problems.

GTL (Gas-to-Liquid) drilling base fluids, such as Shell GTL Saraline™ 185V/NEOFLO™ 4633, are synthetic hydrocarbons produced via Fischer-Tropsch synthesis from natural gas. GTL Fluids are predominantly comprised of iso- and normal paraffins and contain virtually no aromatics or contaminants such as sulphur and amines. Saraline 185V is a Health, Safety, Security, and Environmental (HSSE)- advantaged base fluid for use in global exploration and production drilling operations onshore and offshore. Extensive terrestrial, freshwater and marine ecotoxicity testing with Saraline 185V and related GTL Fluids confirm a lack of acute or significant chronic toxicity to a wide range of environmentally relevant organisms. Saraline 185V is also readily biodegradable in aerobic freshwater, seawater, soil and sediments and will also degrade under anaerobic conditions. The biodegradability can be exploited to bioremediate drill cuttings, as has been demonstrated in both laboratory and field trials. Furthermore, when used offshore, marine benthic surveys have demonstrated that degradation also occurs and that there is a lack of any significant environmental impact associated with the discharge of Saraline 185V contaminated drill cuttings. Extensive mammalian toxicity testing of GTL Products indicates that Saraline 185V will exert very little, if any, toxicity in mammalian species. Saraline 185V is odourless, and vapour emission tests reveal that it has >7-fold lower gas emissions when compared to conventional diesel, thereby leading to better air quality on drilling locations. A recent study which assessed emission and personal exposure levels to various hydrocarbons at key phases of drilling operations confirmed that significantly lower hydrocarbon exposures occurred for mud systems based on Saraline 185V compared to conventional diesel. The drilling performance of GTL versus diesel based muds has also been assessed in an onshore drilling operations study. To enable a fair comparison all wells were drilled in the same formation (located in the Permian Basin of West Texas) using the same drilling rig, crews, bit, footage, fluid contractor, tools and directional driller. These field trial data indicated an overall drilling improvement for GTL over diesel mud. This paper provides an overview of the exposure, human health, environmental and performance studies conducted on GTL drilling fluids. In combination, these create a value proposition for GTL Fluids showing that better health management combined with reduced environmental footprint and improved drilling and equipment performance leads to lower total well costs.