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Belfroid S.P.C.,TNO | Nennie E.,TNO | Lewis M.,Xodus Group
BHR Group - 10th North American Conference on Multiphase Technology 2016 | Year: 2016

Piping structures are generally subjected to high dynamic loading due to multiphase fluid forces. In particular subsea structures are very vulnerable as large flexibility is required to cope for instance with thermal stresses. The forces due to multiphase flow are characterized by a broadband spectrum with high amplitudes. These forces differ with flow regimes and are still difficult to predict. Therefore a joint industry project was setup to perform both large scalc (6") How tests and to qualify CFD procedures and settings to calculate these forces with sufficient accuracy. In various publications [1- 12| forces on bends due to multiphase flow has been published. The measurement set-ups in these publications range from small size piping of 6mm up to large size piping of 100mm diameter. Most publications report the measured force for different liquid void fractions, as different results are obtained for low or high liquid void fractions. Different scaling rules are proposed with respect to hold-up, mixture momentum and Weber-number. The amplitude (root-mean-square of transient part of the force), combined with predictions of the power spectral density (PSD) function and centre frequency give a basis for a good force prediction. In general for multiphase conditions, the PSD shows a top-hat configuration. With the PSD, the force on a bend can be estimated. However, bends are never present isolated from the rest of the piping. For a complete structure, the forces on all bends (and valves, reducers, '[joints, ...) need to be defined. At each bend the force spectrum must be known. That is, the total dynamic force amplitude (root means squarc( RMS)), the frequency spectrum, the phases between the frequencies and finally, the phase relation between the forces at the difference bends. The question is therefore how representative the PSD measured at a single bend is for a bend in larger structures. Focus in this paper is on showing and discussing the differences in behaviour between a single bend compared to the behaviour of a bend with an upstream disturbance. This is done by installing a Ubend configuration upstream of the measurement bend. Measurements have been performed with the Ubend configuration in both the horizontal and vertical position. © BHR Group 2016.

Luna-Ortiz E.,Xodus Group | Healey M.,Xodus Group | Anderson R.,Heriot - Watt University | Sorhaug E.,Talisman Norge AS
Energy and Fuels | Year: 2014

One of the methods to control the formation of hydrates in oil and gas pipelines is the injection of kinetic hydrate inhibitors (KHIs). The accepted understanding is that KHIs slow down or interfere with hydrate nucleation, forcing an extended "induction time" (time to emergence of viable hydrate crystals) at a given subcooling. As a result, KHIs are commonly evaluated by measuring induction times in the laboratory. However, this experimental approach has some limitations, notably in that data can be stochastic due to the nucleation element, raising questions over reliability/transferability, with multiple repeats often required to establish clear trends. As KHIs also exhibit powerful growth inhibition properties, a new crystal growth inhibition (CGI) method for the evaluation of KHIs has been previously developed with the aim of providing a means to more rapidly evaluate KHIs in a robust manner. This method shows that KHIs induce a number of well-defined hydrate CGI regions with different growth rates as a function of subcooling, and these can be used to reliably evaluate inhibition performance on quite short time scales. In this work, we present the results of an experimental program for the qualification of a commercial KHI to be used in a greenfield development using this CGI method. The aim of the laboratory work was to determine required inhibitor dosage, investigate the effects of a corrosion inhibitor (CI) on KHI performance, and evaluate the potential for KHI inhibition during shut-in/restart, in addition to flowing conditions. The program focused on CGI methods for evaluation in addition to standard induction time measurements. A methodology to recreate pipeline flowing, shut-in, and restart conditions was also developed and used. The CGI approach was found to offer advantages in the speed of KHI assessment and provides a useful decision-making tool with respect to KHI field deployment. Data also correlate with and compliment traditional induction time results which still provide valuable information on the degree of "nucleation" inhibition offered on top of crystal growth inhibition. In addition to offering excellent hydrate inhibition under flowing conditions, results suggested the KHI could readily offer good protection for long periods of shut-in (e.g., >168 h at up to 15 °C subcooling) followed by restart, reducing or negating the need for depressurization procedures in the event of shut-in. © 2014 American Chemical Society.

Gooding S.,UTEC Geomarine | Allan P.,UTEC Geomarine | Errington P.,Cathie Associates | Hunt J.,Xodus Group
Frontiers in Offshore Geotechnics III - 3rd International Symposium on Frontiers in Offshore Geotechnics, ISFOG 2015 | Year: 2015

In the past, a ‘burial protection index’was used to provide a framework for selecting appropriate burial depths; however, this approach was relatively crude and did not take into account the probability of threats. This paper presents the results of a research study funded by the developers of offshore windfarms to provide a probabilistic framework for selecting a depth of lowering with an acceptable degree of risk. This can then lead to significant savings in installation costs. The methodology presented provides models for penetration of typical ship anchors and fishing gear into the seabed, and assesses the probability of them being deployed on a cable route. This then allows a statistical assessment of the relative benefits of increasing depth of lowering, and reducing probability of damage to be made. Thus an informed decision can be made when selecting appropriate depths. © 2015 Taylor & Francis Group, London.

Neill S.P.,Bangor University | Lewis M.J.,Bangor University | Hashemi M.R.,Bangor University | Slater E.,British Oceanographic Data Center | And 2 more authors.
Applied Energy | Year: 2014

The waters surrounding the Orkney archipelago in the north of Scotland are one of the key regions in the world suitable for exploitation of both wave and tidal energy resources. Accordingly, Orkney waters are currently host to 1.08. GW of UK Crown Estate leased wave and tidal energy projects, with a further 0.5. GW leased in the southern part of the adjacent Pentland Firth. Although several wave resource models exist of the region, most of these models are commercial, and hence the results not publicly available, or have insufficient spatial/temporal resolution to accurately quantify the wave power resource of the region. In particular, no study has satisfactorily resolved the inter-annual and inter-seasonal variability of the wave resource around Orkney. Here, the SWAN wave model was run at high resolution on a high performance computing system, quantifying the Orkney wave power resource over a ten year period (2003-2012), a decade which witnessed considerable inter-annual variability in the wave climate. The results of the validated wave model demonstrate that there is considerable variability of the wave resource surrounding Orkney, with an extended winter (December-January-February-March, DJFM) mean wave power ranging from 10 to 25. kW/m over the decade of our study. Further, the results demonstrate that there is considerably less uncertainty (30%) in the high energy region to the west of Orkney during winter months, in contrast to much greater uncertainty (60%) in the lower energy region to the east of Orkney. The DJFM wave resource to the west of Orkney correlated well with the DJFM North Atlantic Oscillation (NAO). Although a longer simulated time period would be required to fully resolve inter-decadal variability, these preliminary results demonstrate that due to considerable inter-annual variability in the NAO, it is important to carefully consider the time period used to quantify the wave power resource of Orkney, or regions with similar exposure to the North Atlantic. Finally, our study reveals that there is significantly less variability in the practical wave power resource, since much of the variability in the theoretical resource is contained within relatively few extreme events, when a wave device enters survival mode. © 2014 The Authors.

Zanganeh M.N.,Xodus Group | Kraaijevanger J.F.B.M.,Royal Dutch Shell | Buurman H.W.,Royal Dutch Shell | Jansen J.D.,Technical University of Delft | Rossen W.R.,Technical University of Delft
Computational Geosciences | Year: 2014

We apply adjoint-based optimization to a surfactant-alternating gas foam process using a linear foam model introducing gradual changes in gas mobility and a nonlinear foam model giving abrupt changes in gas mobility as function of oil and water saturations and surfactant concentration. For the linear foam model, the objective function is a relatively smooth function of the switching time. For the nonlinear foam model, the objective function exhibits many small-scale fluctuations. As a result, a gradient-based optimization routine could have difficulty finding the optimal switching time. For the nonlinear foam model, extremely small time steps were required in the forward integration to converge to an accurate solution to the semi-discrete (discretized in space, continuous in time) problem. The semi-discrete solution still had strong oscillations in gridblock properties associated with the steep front moving through the reservoir. In addition, an extraordinarily tight tolerance was required in the backward integration to obtain accurate adjoints. We believe the small-scale oscillations in the objective function result from the large oscillations in gridblock properties associated with the front moving through the reservoir. Other EOR processes, including surfactant EOR and near-miscible flooding, have similar sharp changes and may present similar challenges to gradient-based optimization. © 2014 Springer International Publishing Switzerland.

Stephenson S.,Xodus Group
Acoustics Bulletin | Year: 2013

The combination of directivity and noise propagation effects which can potentially lead to high levels of noise at distances away from the exhaust stack is examined. Exhaust stacks, and other open ducts, have a relatively high degree of directivity. The sound power level of a stack can either be calculated or measured. There are several methods to do this, but each method will depend on the type of project. ISO 10494 presents a method for determining the sound power level of a stack exit. The standard is based on taking measurements at a defined angle of 20° above and below the lip of the stack (horizontal axis), integrating over an assumed surface area and then summing the upper and lower surfaces to derive a sound power level. Once the sound power level of the stack has been determined, it is then necessary to apply corrections to this level to account for directivity, as seen from the receiver position. Once this imission angle has been determined, it is then possible to attribute the correct directivity corrections to the stack exit sound power level.

Tissen J.,Xodus Group | Buchan I.,GDF SUEZ
Society of Petroleum Engineers - SPE Offshore Europe Conference and Exhibition, OE 2013 | Year: 2013

In this paper, we will report on the development of an environmental case approach for GDF SUEZ E&P UK. As one of the now adopted recommendations of the Maitland report following the Deepwater Horizon disaster, OGUK is taking forward its Environmental Assurance Plan concept. In support of this, GDF SUEZ E&P UK commissioned Xodus to develop a number of environmental management plans for its Cygnus Field Development that could reduce the administrative burden, ensure compliance and enhance internal and external dialogue about the management of environmental issues. The resulting E-cases are central to the company's environmental management system, bridge the gap between operational objectives and stakeholder expectations and provide an audit trail between these high level objectives and individual tasks and responsibilities as depicted in the figure below. The E-cases mirror the intent of Lord Cullen's Safety Case approach in that they offer a way to maximise the benefits of both prescriptive and goal setting regulation. They do this by creating a platform for open dialogue about these important issues, and achieve full integration of environmental management into the operation and maintenance of offshore E&P operations. The E-cases are fully aligned with the international standard on environmental management systems ISO 14001. (Graph Presented) Copyright 2013, Society of Petroleum Engineers.

Jewell S.,Xodus Group
Hart's E and P | Year: 2010

Europe's oil and gas industry is undergoing a marked transition with the potential of unconventional gas being realized by oil companies. The upstream business is turning to unconventional sources as a means of securing long-term future supplies and also to provide the scale of resources needed to balance reserve portfolios and to protect corporate balance sheets. The primary target is unconventional gas, which is derived from shale or CBM extraction and accounts for more than 10% of US domestic gas supply. Australia also is an established producer, with emerging nations including China, India, and Indonesia, all of which have seen pilot developments spring up in the wake of significant drilling in the last few years. The US Department of Energy estimates shale gas will provide 50% of the country's demand within 20 years. It is often said that what happens in the US today will be repeated in Europe tomorrow.

Tissen J.,Xodus Group | Buchan I.,GDP Suez e and P UK
Offshore Engineer | Year: 2014

Experts inform that a new approach to manage environmental issues aims at delivering increased alignment, engagement, transparency, and assurance in relation to managing environmental issues at the Cygnus gas field in he southern North Sea. This approach offers a better alignment with other business objectives and increased confidence in compliance with the existing existing legislative framework. It is being applied by GDF SUEZ E&P UK for the drilling program and operational phase of the southern North Sea Cygnus gas development project. The approach plays a key role in maximizing the benefits of prescriptive and goal setting regulation. This is done by creating a platform for open dialogue around important issues, which aims to achieve full integration of environmental management into the operation and maintenance of offshore exploration and production operations.

Thomas N.,Xodus Group | Stephenson S.,Xodus Group
Institution of Chemical Engineers Symposium Series | Year: 2015

Petrochemical and process sites are required to ensure best available techniques are employed to control noise. This can be as a result of permitting requirements, occupational noise exposure, addition of new plant, or changes in operating conditions. Identifying noise control mitigation options for existing industrial sites and demonstrating best available techniques can present engineering challenges and come at a high cost. This paper presents a roadmap for identifying effective noise control mitigation measures at the lowest cost to industry. It includes considerations for a combined approach to sound power determination and cost-benefit analysis. Techniques include sound power estimation, sound intensity and vibration velocity. Case studies from recent work on process sites will be presented and include auralisation examples, to demonstrate the real world benefit of the techniques under discussion. © 2015 Amec Foster Wheeler.

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