Sustainable seabed mining: guidelines and a new concept for Atlantis II Deep

The feasibility of exploiting seabed resources is subject to the engineering solutions, and economic prospects. Due to rising metal prices, predicted mineral scarcities and unequal allocations of resources in the world, vast research programmes on the exploration and exploitation of seabed minerals are presented in 1970s. Very few studies have been published after the 1980s, when predictions were not fulfilled. The attention grew back in the last decade with marine mineral mining being in research and commercial focus again and the first seabed mining license for massive sulphides being granted in Papua New Guinea’s Exclusive Economic Zone.Research on seabed exploitation and seabed mining is a complex transdisciplinary field that demands for further attention and development. Since the field links engineering, economics, environmental, legal and supply chain research, it demands for research from a systems point of view. This implies the application of a holistic sustainability framework of to analyse the feasibility of engineering systems. The research at hand aims to close this gap by developing such a framework and providing a review of seabed resources. Based on this review it identifies a significant potential for massive sulphides in inactive hydrothermal vents and sediments to solve global resource scarcities. The research aims to provide background on seabed exploitation and to apply a holistic systems engineering approach to develop general guidelines for sustainable seabed mining of polymetallic sulphides and a new concept and solutions for the Atlantis II Deep deposit in the Red Sea.The research methodology will start with acquiring a broader academic and industrial view on sustainable seabed mining through an online survey and expert interviews on seabed mining. In addition, the Nautilus Minerals case is reviewed for lessons learned and identification of challenges. Thereafter, a new concept for Atlantis II Deep is developed that based on a site specific assessment.The research undertaken in this study provides a new perspective regarding sustainable seabed mining. The main contributions of this research are the development of extensive guidelines for key issues in sustainable seabed mining as well as a new concept for seabed mining involving engineering systems, environmental risk mitigation, economic feasibility, logistics and legal aspects

Reducing carbon footprint of deep-sea oil and gas field exploitation by optimization for Floating Production Storage and Offloading

Deep-sea oil and gas fields are acting as a vital role by providing substantial oil and gas resource, and Floating Production Storage and Offloading is an indispensable tool for the development of offshore oil and gas fields effectively. Here, Life Cycle Assessment is applied to evaluate environmental loads in the whole life cycle of the deep-sea oil and gas production. This paper explores the carbon footprint of Floating Production Storage and Offloading as the time axis. It is found that Floating Production Storage and Offloading is a conceptual product at the design stage and does not generate carbon emission, while the operational stage releases considerable emission by the fuel combustion process, accounting for 88.2% of the entire life cycle. To decrease this part of carbon emission, distributed energy system is considered as a promising choice because it integrates different energy resources and provides an economic and environmental energy allocation scheme to meet the energy demand. For the operation stage, this paper establishes a Multi-objective Mathematical Programming model to determine the selection and capacity of facilities with minimum annual total cost and carbon emissions by considering the energy balance and technical constraints. The model is validated by an example and solved by the weight method. According to designer's demand, distributed energy system can optimize economic objectives in a maximum range of 14.6%, and a maximum emission reduction of 4.53% can be expected compared with the traditional scheme. Sensitivity analysis shows that cost is more sensitive to natural gas price

A review of test protocols for assessing coating performance of water ballast tank coatings

Concerns on corrosion and effective coating protection of double hull tankers and bulk carriers in service have been raised especially in water ballast tanks (WBTs). Test protocols/methodologies specifically that which is incorporated in the International Maritime Organisation (IMO), Performance Standard for Protective Coatings for Dedicated Sea Water ballast tanks (PSPC) are being used to assess and evaluate the performance of the coatings for type approval prior to their application in WBTs. However, some of the type approved coatings may be applied as very thick films to less than ideally prepared steel substrates in the WBT. As such films experience hygrothermal cycling from operating and environmental conditions, they become embrittled which may ultimately result in cracking. This embrittlement of the coatings is identified as an undesirable feature in the PSPC but is not mentioned in the test protocols within it. There is therefore renewed industrial research aimed at understanding this issue in order to eliminate cracking and achieve the intended coating lifespan of 15 years in good condition. This paper will critically review test protocols currently used for assessing and evaluating coating performance, particularly the IMO PSPC

Ultra-Deep Water High Pressure Riser Concept Offshore Brazil

Master's thesis in Offshore technology : subsea technologySince the 1950s, risers have continued to be an important part of an oil and gas producing field. As the primary equipment that conveys fluids to and from the topside vessel, it is important that a riser is designed to withstand all conditions it will be subjected to during its lifetime. With hydrocarbon exploration activities moving into ultra-deep water, research related to the structural integrity of a riser deployed in ultra-deep water has become necessary. The ultra-deep water region considered in this thesis work is the Santos Basin located about 300 km offshore Brazil. The Santos Basin is a benign environment that is not characterized by hurricanes, typhoons or extreme weather conditions. However, oil producing activities in this region would require a vessel that has storage capabilities due to the distance the region is from shore. With this requirement in mind, different floaters were evaluated and a spread-moored Floating Production, Storage and Offloading (FPSO) vessel was selected for this thesis work. The selection of the spread-moored FPSO presented a new challenge; high motion sensitivity. Since FPSOs are high motion vessels, risers connected to them will experience fatigue damage in their touchdown zone. However, after evaluation of different riser concepts, the Steel Lazy Wave Riser (SLWR) was selected because it has the ability to decouple its touchdown zone from vessel motions due to the presence of buoyancy modules fitted along the lower section of the riser. With the selection of spread-moored FPSO and a SLWR, material selection for the SLWR was carried out. For ultra-deep water deployment, a riser’s material should posses ultra-high strength, good weldability, high collapse resistance, high operating pressure and excellent low-temperature toughness. These material properties are found in the API 5L X65,X80 and X90 carbon steel grade material. Hence, they were the selected material used for the SLWRs in this thesis work. Dynamic and fatigue response analysis was conducted on the SLWRs made of each material and it was observed that all the three materials met the requirements of the DNV-OS-F201 reference standard with the X65 riser having the worst dynamic response, followed by the X80 riser, followed by the X90 riser. Also in past SLWR deployments with spread-moored FPSOs, risers were usually connected to hang-off points along the port side of the vessel. In this thesis work the SLWRs were connected to hang-off points both along the port side of the vessel and along the middle of the vessel. The purpose of doing this was to investigate if buoyancy can be saved by connecting a riser along the middle of the vessel rather than the along the port side. From the results of the investigation, it was observed that about 7.5% of buoyancy could be saved by connecting a riser to the middle of the vessel rather than to the port side of the vessel. In addition, it was observed that risers connected to the middle of the vessel showed an increase of at least 246% in the minimum fatigue life observed. Overall, all the riser materials considered in this study all meet the dynamic and fatigue response criteria. Therefore, further work should be carried out as given in the recommendations of this thesis work to select the most suitable material for deployment in the ultra-deep water region of the Santos Basin, offshore Brazil

Collision Damage Analysis of FPSO Hull Caisson Protection Structure

The protection structures for the Floating Production Storage and Offloading (FPSO) caissons should be sufficiently strong to avoid contact with the caisson pipes even when the protection structure is damaged by the impact of the accompanying vessels. Collision events of protectors of appurtenances such as risers, mooring lines, and seawater lift caissons with supply vessel may cause structural damage to protection structures and even to the appurtenance structures and hull structures. This study introduces the collision impact analyses on three protective structures of FPSO against striking supply vessel whose displacement is 7,500 tons. The capacity of protection structures in view of strain energy has been assessed with simple beam FE models. The striking vessel has been modelled as a small rigid body, and impact simulation has been performed including material and geometric nonlinearities where ABAQUS Explicit tool, which is a commercial explicit code, has been used for non-linear collision analyses with protection structures. The results from the current work will be a guide to understanding the impact response of offshore structures and evaluation approaches, and will provide useful indications for the FPSO hull caisson protection design and operation. In addition, the findings obtained by the current study will be informative in the safe design of FPSO facilities

Material degradation in mooring chains for floating structures in deep waters

There is a dire need for an efficient, trustworthy, and financially feasible positioning technique for offshore large floating structures. Of all the methods of positioning the offshore structures, the mooring chains play a significant role. There is a need for explicit knowledge of the properties of mooring systems so that the design, operation, and analysis of large floating structures, particularly in deep water, should be reliable. Experts from the oil and gas industry have experienced actual corrosion loss rates data for mooring systems that they get are different from those allowed for in traditional design guidance and have long been a recognized challenge. The corrosion allowances from the codes are sometimes very conservative leading to an over design (thicker); this could be the other way round, in some cases. Recently, as long as corrosion has been tolerated with an 'allowance', thicker and heavier chains have been the only way to extend the life of these mooring chains. On the other hand, Corrosion rates can be unpredictable and vary greatly around the world due to the diverse marine environments. As a worst-case scenario, this results in significantly shortened chain lifespans and, at the very least, increased failure rates and integrity issues in the mooring systems. The findings of this study will result in a practical equation function from previous studies that can be used to estimate corrosion loss in deep water based on parameters that have a significant impact on the corrosion, such as temperature, and dissolved inorganic nitrogen (nitrates, nitrites, and ammonia) usually measured together as DIN concentration levels. Data may be unavailable in some regions, or finding them may be difficult, and using the allowances during design from the standards without considering the parameters may lead to inappropriate allowances, and as a result failure may occur. Thereafter, estimating the rest life of inservice degraded mooring chains is another issue and how can this be done through FEM analysis. Finally, although Cathodic Protection has long been a part of corrosion prevention strategies for offshore steel structures, the mooring lines have never been successfully protected in deep waters. Finding a method of protection to extend the lifetime of these degraded chains is another challenge. Following extensive research, a new sacrificial anode cathodic protection system technology has been found in recent years. Considering this method has guaranteed efficiency and a cathodic protection calculation has been made using these anode types

Suction Anchors for Deepwater Moorings at Nkossa and Girassol in 200 and 1,400M of Water

A new type of anchor, composed of steel caissons installed into the soil by suction under-pressure, presently finds a strong interest in the offshore oil industry, in particular for deepwater sites because of its vertical loading capability in taut-leg moorings, and the reduced installation equipment required. Two case histories are presented in the paper, describing the installation of the moorings for the Nkossa barge in Congo in 1995 and for the Girassol FPSO in Angola in 2001. In both cases, the paper gives the general soil conditions and design assumptions, together with the results of the installation operations, with a comparison between the predictions and the monitored site installation results. For the Nkossa barge anchors in about 200m of water, the results obtained in soft normally consolidated clays were in perfect agreement with the predictions, thus demonstrating the reliability of the design installation procedure. For the Girassol FPSO anchors in 1,400m of water, the measured anchor penetration resistance in soft highly plastic clays was lower than predicted, raising concern about the actual anchor holding capacity in a taut-leg mooring system with a significant vertical loading component. Following a third party review of the design assumptions, the holding capacity of the FPSO anchors was validated, and an improved installation prediction method was proposed

Microbiologically Influenced Corrosion in Floating Productions Systems

Microbiologically influenced corrosion (MIC) represents a serious and challenging problem in Floating, Production, Storage and Offloading vessels (FPSOs), one of the most common type of offshore oil production facilities in Australia. Microorganisms can attach to metal surfaces, which under certain conditions, can result in corrosion rates in excess of 10 mm per year (mmpy) leading to equipment failure before their expected lifetime. Particularly, increasing water cut (ratio of water vs. total fluids produced), normally resulting from the age of the assets, results in an increased risk of MIC. This paper provides an overview of causative microorganisms, their source of contamination and the areas within FPSOs that are most prone to MIC. Although mitigation practices such as chemical treatments, flushing and draining and even cathodic protection are effective, MIC can still occur if the systems are not properly monitored and managed. A case study is presented that describes the microorganisms identified in a FPSO operating in Australia suspected of having MIC issues