The state of Kerala, located on the west coast of India, experienced a record 100‐year flood that resulted in major landslides from unprecedented prolonged and extremely heavy rainfall (50–480 ...mm·day−1) during August 1–19, 2018, causing extensive damage and about 500 causalities. Rainfall observations indicate that the heavy rainfall occurred over two spells (August 7–10 and 14–18) in association with an offshore trough, and a depression over the Bay of Bengal (BOB). High‐resolution 38‐year climatology data (5 km) and the ERA‐Interim reanalysis dataset show a strong low‐level jet over the Arabian Sea and a depression over the BOB with a southwestward tilt during the heavy rainfall. Very high‐resolution (2‐km) mesoscale model simulations suggest that this high convective instability due to the strong westerly jet along with the formation of offshore vortex, the transport of mid‐tropospheric moisture under the presence of conducive vertical shear of horizontal wind, and transport of mid‐tropospheric moisture from the BOB are the major factors (as shown in the schematic diagram) behind the extreme heavy rainfall over Kerala.
Schematic of flow patterns associated with the Kerala heavy rainfall event during August 14–17, 2018. Low/high pressure systems are represented by closed circles with L/H in red/white color. The mid‐tropospheric circulation is indicated by the yellow circle, and the thickness of the arrows indicates the strength of the wind speed.
Corrosion is the destructive chemical attack, abrasive action of tidal waves, and microbial attacks upon a metallic structure by its environment, and it is the commonest electrochemical phenomenon ...that is experienced in day-to-day activities of offshore oil and gas production. Corrosion control of metallic structures is an important activity in technical, economic, environmental and safety terms. The negative impacts of corrosion are so enormous, and it is therefore imperative for oil and gas industry, particularly offshore industry to have corrosion awareness in their daily activities with a view to providing corrosion protection of offshore structures, and ensure safe and productive drilling operations. This review discusses extensively multi-component synthetic organic compounds and phytochemicals of green inhibitors with S, N and O functionalities in their structure, for use as corrosion inhibitors against the corrosion of offshore oil and gas production facilities such as pipelines and storage containers in corrosive media, stressing specifically their synthesis (where applicable), properties and efficiency of inhibitors. Also addressed in this review are the future challenges in flow assurance due to the formation of gas hydrates in flowline, especially for offshore oil and gas production. The corrosion performance tests are extensively discussed.
•Organic compounds with N,S,O functionalities inhibit offshore oil and gas production facilities.•Inhibitory performance of organic inhibitors are concentration and temperature dependent.•Organic inhibitors exhibit inhibitory performance by adsorption on metal surface.•Organic inhibitors prevent anodic, cathodic or combination of the two in corrosive media.
The present work is of methodological nature, and represents an addendum to the guidelines for multivariate analysis and design in coastal and off-shore engineering recently presented in literature. ...The target of the paper is to provide a general framework for the multivariate assessment of the risk of failure by using a structural approach. Shortly, Monte Carlo procedures are adopted in order to estimate, for given Return Periods, the design structural variable(s) of interest, which may depend on a set of multivariate random inputs. As an advantage, the distribution of the structural variable(s) is computed by means of non-parametric techniques, which replace the fit of parametric distributions, an awkward task involving arbitrary choices. A practical case study is used to show the application of the procedures, and to compare the structural-risk approach proposed here with the strategies adopted in previous papers.
•Practical guidelines for a multivariate structural risk assessment are outlined.•Monte Carlo procedures are introduced to bypass possible analytical problems.•Strategies for coastal and off-shore structural multivariate design are shown.•Procedures for data randomization and scenario generation are discussed.•Comparisons with traditional strategies are presented.
The tectonic evolution of the Black Sea (BS) is a subject of debate, there are several unsolved questions: 1) the timing and the spatial progression of the BS basin opening and 2) the timing of ...Cenozoic shortening along the northern margin of the Eastern BS basin. The timing of the main compressional deformations, related to the inversion of the Greater Caucasus (GC) basin, is assumed to be Oligo-Miocene. However, Late Cretaceous/Early Paleocene shortening, linked to the final closure of the northern branch of the Neotethys, is also suggested. The Crimean Mountains (CM), to the north of the Eastern BS, is one of the key areas to investigate in order to fix the tectonic evolution of the BS. To precise the timing of the Cenozoic shortening of the Eastern BS, we focus on an integrated onshore/offshore transect from the Eastern CM to the Sorokin Trough (north of Eastern BS). We use newly collected stratigraphic and structural data from the Eastern CM, and a new interpretation of multichannel seismic lines. We define 1) the offshore seismic stratigraphy and constrain the relative chronology of deformations, 2) the age of seismic units by correlation of the seismic data with the Subbotina-403 well log, and 3) we construct an on-to-off shore transect of Eastern CM - northern Eastern BS region. Our results evidence a polyphased Cenozoic compression in the northern part of the Eastern BS: 1) Paleocene-Earliest Eocene and 2) Oligocene-Miocene (Maikopian). Normal faults appear to be related to a formation of the foreland basin, instead of evidencing the Eastern BS Cretaceous rifting. Finally, this study allows precising the shortening phases within Eastern CM and Eastern BS since the Early Paleocene, linking them to the Neotethys closure and the GC tectonic evolution.
•Land and marine based transects illustrate inversion of the Eastern Black Sea.•Evidence of a two phases Cenozoic compression•Normal faults are related to a foreland basin formation rather than Cretaceous rifting.
Offshore pile driving is a high-risk activity as delays can be financially punitive. Experience of pile driving for offshore jacket structures where pile diameters are typically < 2 m has led to the ...development of empirical pile driveability models with proven predictive capability. The application of these methods to larger diameter piles is uncertain. A major component of driveability models involves estimating the static resistance to driving, SRD, a parameter analogous to pile axial capacity. Recent research on axial capacity design has led to improved models that use Cone Penetration Test, CPT data to estimate pile capacity and include for the effects of friction fatigue and soil plugging. The applicability of these methods to estimating pile driveability for larger diameter piles is of interest. In this paper, recent CPT based axial capacity approaches, modified for mobilised base resistance and ageing, are applied to estimating driveability of 4.2 m diameter piles. A database of pile installation records from North sea installations are used to benchmark the methods. Accounting for factors such as pile ageing and the relatively low displacement mobilised during individual hammer blows improves the quality of prediction of pile driveability for the conditions evaluated in this study.
•Traditional pile driveability methods mainly underestimate predicted blow counts.•Stevens Plugged Approaches should not be used for large diameter piles.•Applying unmodified IC-05 and UWA-05 is mostly unsuitable for monopile driveability.•Adopting base-settlement model with UWA-05 improves the prediction.•The inclusion of residual base stresses leads to a further improvement with UWA-05.
The decommissioning of offshore structures around the world will be a persisting problem in the coming decades as many structures will exceed their shelf life, or when reservoirs are no longer ...productive. This paper examines an overview of the global offshore decommissioning legal regime, and a summary of regulations in countries that are deemed to be more experienced in decommissioning such as the UK, Norway and USA. Two oil-producing countries in South East Asia, Malaysia and Thailand are also reviewed to identify potential gaps in decommissioning legislation for countries in its infancy in decommissioning. The differences were identified in terms of decommissioning preparation, decommissioning technical execution, additional environmental requirements and financial security framework. In conclusion, the majority of the regulations covering the technical section are similar within all countries studied. Major differences lie in two overarching philosophies of the framework – a prescriptive regime versus a goal-setting regime. Other decommissioning aspects appear to attract increasing attention, such as in expanding clarity on in situ decommissioning, residual liabilities, optimising finance related issues of decommissioning and offshore to onshore waste movement. These gaps in the existing framework can be filled by taking an evidence-based stand in developing the framework.
•There are two overarching philosophies for the regulations: prescriptive and goal-setting.•The majority of the regulations covering the technical section are similar.•Both technical and non-technical decommissioning aspects appear to attract increasing attention from governments.•These areas of interest are in situ decommissioning, work optimisation, liability transfer mechanisms and waste movement.
Structural health monitoring of mechanical systems is essential to avoid their catastrophic failure. In this article, an effective deep neural network is developed for extracting the damage-sensitive ...features from frequency data of vibration signals to damage detection of mechanical systems in the presence of the uncertainties such as modeling errors, measurement errors, and environmental noises. For this purpose, the finite element method is used to analyze a mechanical system (finite element model). Then, vibration experiments are carried out on the laboratory-scale model. Vibration signals of real intact system are used to updating the finite element model and minimizing the disparities between the natural frequencies of the finite element model and real system. Some parts of the signals that are not related to the nature of the system are removed using the complete ensemble empirical mode decomposition technique. Frequency domain decomposition method is used to extract frequency data. The proposed deep neural network is trained using frequency data of the finite element model and real intact state and then is tested using frequency data of the real system. The proposed network is designed in two stages, namely, the pre-training classification based on deep auto-encoder and Softmax layer (first stage), and the re-training classification based on backpropagation algorithm for fine tuning of the network (second stage). The proposed method is validated using a lab-scale offshore jacket structure. The results show that the proposed method can learn features from the frequency data and achieve higher accuracy than other comparative methods.
This paper reports the findings from the 2016 Wind Energy Research Workshop held in Lowell, MA. The workshop examined the state-of-the-art in wind energy research within the following three core ...topic areas: (A) Wind Turbine Design and Manufacturing including: blades, towers/foundations and nacelle, (B) Wind Farm Development including: offshore installations/siting, flow characterization and loads/waves/wind characterization, and (C) Wind Farm Operations including: controls, power production, wind farms, sensing, diagnostics, testing, structural health monitoring, reliability, energy storage, the grid and power transmission. Research challenges and future directions were discussed and are reported for each sub-topic area.
•Wind Turbine Design and Manufacturing, o Wind Turbine Design and Manufacturing (Blades, Towers/Foundations, and Nacelle).•Wind Farm Development (Offshore Installations, Flow/Load/Wave Characterization).•Wind Farm Operations (Controls, Structural Health Monitoring, Energy Storage/Grid).
A frequent statistical problem in many coastal and off-shore engineering situations is to estimate the probability of structural failure expressed in terms of Return Period and Design Quantile. ...Usually, only the univariate approach is carried out to quantify the risk of failure. However, coastal and off-shore structures typically fail because of the occurrence of a critical combination of all the variables at play in a single sea storm: thus, it may be important to consider the joint occurrence of dangerous conditions. The present manuscript provides practical guidelines in order to carry out a sensible multivariate analysis of the available data, including a randomization procedure to cope with repeated observations. In addition, suitable strategies for performing multivariate design are presented and discussed. A practical case study is used to show the application of the techniques illustrated throughout the paper, and a preliminary rubble mound breakwater design is also carried out.
•Practical guidelines to carry out a sensible multivariate analysis are outlined.•A statistically consistent definition of multivariate return periods is presented.•Strategies for coastal and off-shore structural multivariate design are shown.•Critical multivariate design values of wave height and storm duration are calculated.•Procedures for data randomization and random scenarios generation are introduced.
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