Wood Group
  • Aberdeen, United Kingdom
Recent publications
Background The number of women of childbearing age with Type 2 diabetes(T2DM) is increasing, and they now account for > 50% of pregnancies in women with pre-existing diabetes. Diabetes pregnancies without adequate pre-pregnancy care have higher risk for poor outcomes (miscarriages, birth-defects, stillbirths) and are associated with increased complications (caesarean deliveries, macrosomic babies, neonatal intensive-care admissions). The risks and costs of these pregnancies can be reduced with pregnancy preparation (HbA1c, ≤ 6.5%, 5 mg folic acid and stopping potentially harmful medicines). However, 90% of women with T2DM, most of whom are based in primary care, are not adequately prepared for pregnancy. This study will evaluate a programme of primary care-based interventions (decision-support systems; pre-pregnancy care-pathways; pregnancy-awareness resources; professional training; and performance monitoring) to improve pregnancy preparation in women with T2DM. Methods The study aims to optimise the programme interventions and estimate their impact on pregnancy preparation, pre-pregnancy care uptake and pregnancy outcomes. To evaluate this multimodal intervention, we will use a multi-method research design following Complex Adaptive Systems (CAS) theory, refining the interventions iteratively during the study. Thirty GP practices with ≥ 25 women with T2DM of reproductive age (18–45 years) from two South London boroughs will be exposed to the intervention. This will provide > 750 women with an estimated pregnancy incidence of 80–100 to study. The research involves: a clinical audit of processes and outcomes; a process evaluation informing intervention feasibility, implementation, and behaviour change; and a cost-consequences analysis informing future economic evaluation. Performance data will be collected via audits of GP systems, hospital antenatal clinics and pregnancy outcomes. Following CAS theory, we will use repeated measurements to monitor intervention impact on pregnancy preparation markers at 4-monthly intervals over 18-months. We will use performance and feasibility data to optimise intervention effects iteratively. The target performance for the intervention is a 30% increase in the proportion of women meeting pre-pregnancy care criteria. Discussion The primary output will be development of an integrated programme of interventions to improve pregnancy preparation, pre-pregnancy care uptake, and reduce adverse pregnancy outcomes in women with T2DM. We will also develop an implementation plan to support the introduction of the interventions across the NHS. Trial registration ISRCTN47576591; February 8, 2022.
Objective: The objective of this study was to investigate how night work at low ambient temperatures affects cognitive performance (short-term memory and reaction time), skin- and core temperature, thermal comfort, sleepiness, and cortisol. We hypothesized that cognitive performance is reduced at night compared with daytime and worsened when exposed to low ambient temperatures. Method: Eleven male subjects were recruited to perform three tests in a climatic chamber at night and daytime: Night –2°C, Night 23°C and Day 23°C. Each test lasted 6 h. Cognitive performance (short-term memory and reaction time), skin- and core temperature, thermal sensation and comfort, cortisol levels and sleepiness were measured during the tests. Results: A lower mean skin temperature and corresponding lower thermal sensation were observed at Night –2°C compared to Day 23°C and Night 23°C. Night work caused increased sleepiness and lower cortisol levels, but was not affected by changes in ambient temperatures, thermal comfort, or skin temperatures. There was no effect of either day/night work nor ambient temperature on the short-term memory or reaction time test. Conclusion: Lower skin- and core temperature were observed at night when exposed to low ambient temperature (–2°C), but there was no effect on short-term memory or reaction time. Increased sleepiness and lower cortisol levels were observed at night compared to daytime and was not influenced by low ambient temperature at night. The result from this study suggests that cognitive performance (short-term memory and reaction time) is not adversely affected by night work when exposed to low ambient temperatures if adequate protective clothing is worn.
Background: Composite performance measures for STS Adult Cardiac Surgery Database participants (typically hospital departments or practice groups) are currently available only for individual procedures. To assess overall participant performance, STS has developed a composite metric encompassing the most common adult cardiac procedures. Methods: Analyses included 1-year (July 1, 2018-June 30, 2019) and 3-year (July 1, 2016-June 30, 2019) time windows. Operations included isolated CABG, isolated AVR, isolated mitral valve repair (MVr) or replacement (MVR), AVR+CABG, MVr/MVR+CABG, AVR+MVr/MVR, and AVR+MVr/MVR+CABG. The composite was estimated using Bayesian hierarchical models with risk-adjusted mortality and morbidity endpoints. Star ratings were based on whether the 95% credible interval of a participant's score was entirely below (1-star), overlapped (2-star), or was above (3-star) the STS average composite score. Results: The North American procedural mix in the 3-year study cohort was 448,569 CABG, 72,067 AVR, 35,708 MVr, 29,953 MVR, 45,254 AVR+CABG, 12,247 MVr+CABG, 10,118 MVR+CABG, 3,743 AVR+MVr, 6,846 AVR+MVR, and 3,765 AVR+(MVr/MVR)+CABG. Mortality and morbidity weightings were similar for 1- and 3-year analyses (76% and 24%, [3-year]), as were composite score distributions (median 94.7%, IQR 93.6% to 95.6%, [3-year]). The 3-year timeframe was selected for operational use because of higher model reliability (0.81 [0.78 - 0.83]) and better outlier discrimination (26% 3-star, 16% 1-star). Risk-adjusted outcomes for 1-, 2-, and 3-star programs were 4.3%, 3.0%, and 1.8% mortality, and 18.4%, 13.4%, and 9.7% morbidity, respectively. Conclusions: The STS participant-level, multi-procedural composite measure provides comprehensive, highly reliable, overall quality assessment of adult cardiac surgery practices.
Background: The original STS CABG composite measure uses a 1-year analytic cohort and 98% credible intervals (CrI) to classify better (3-star) or worse (1-star) than expected performance. As CABG volumes per STS participant (e.g., hospital or practice group) have decreased, it has become more challenging to classify performance categories using this approach, especially for lower volume programs, and alternative approaches have been explored. Methods: Among 990 STS Adult Cardiac Surgery Database participants, performance classifications for the CABG composite were studied using various analytic cohorts: single year (current approach, 2017); 3 years (2015-2017); last 450 cases within 3 years; most recent year (2017) plus additional cases to 450 total. We also compared 98% CrI with 95% CrI (used in other STS composite measures). Results: Using 3 years of data and 95% CrI's, 113 of 990 participants (11.4%) were classified 1-star and 198 (20%) 3-star. Compared with 1-year analytic cohorts and 98% CrI, the absolute and relative increases in the proportion of 3-star participants were 14 percentage points and 233% (n=198[20%] versus n=59[6%]). Corresponding changes for 1-star participants were 6.5 percentage points and 133% (n=113[11.4%] versus n=48[4.9%]). These changes were particularly notable among lower volume (<199 CABG/year) participants. Measure reliability with the 3-year, 95% CrI modification is 0.78. Conclusions: Compared with current STS CABG composite methodology, a 3-year analytic cohort and 95% CrI increases the number and proportion of better or worse than expected outliers, especially among lower-volume ACSD participants. This revised methodology is also now consistent with other STS procedure composites.
Cable ploughing is an important technique for burying and protecting offshore cables. The ability to predict the required tow force and plough performance is essential to allow vessel selection and project programming. Existing tow force models require calibration against full-scale field testing to determine empirical parameters, which may hinder their use. In this study the factors controlling the plough resistance were investigated using a series of dry and saturated 1/50<sup>th</sup> scale model cable plough tests in sand in a geotechnical centrifuge at 50g at a range of target trench depths, sand relative densities and plough velocities. An improved model for predicting cable plough tow force which separates out the key components of resistance and allows tow force prediction without the use of field-derived empirical coefficients is presented. It is demonstrated that the key parameters in this model can be easily determined from in-situ Cone Penetration Testing (CPT), allowing it to be used offshore where site investigation techniques may be more limited compared to onshore locations. The model is validated against the centrifuge cable plough tests, demonstrating it can correctly predict both the static (dry) and rate effect (saturated) tow forces.
Background: The longitudinal cost of treating patients with non-small cell lung cancer (NSCLC) undergoing surgical resection has not been evaluated. We describe initial and 4-year resource use and cost for NSCLC patients ≥65 years of age treated surgically between 2008 and 2013. Methods: Using clinical data for NSCLC resections from the Society of Thoracic Surgeons General Thoracic Surgery Database linked to Medicare claims, resource use and cost of preoperative staging, surgery and subsequent care through 4 years were examined ($2017). Cost of hospital-based care was estimated using cost-to-charge ratios; professional services and care in other settings were valued using reimbursements. Inverse probability weighting was used to account for administrative censoring. Outcomes were stratified by pathologic stage, and by surgical approach for Stage I lobectomy patients. Results: Resection hospitalizations averaged 6 days and cost $31,900. In the first 90 days, costs increased with stage ($12,430 Stage I to $26,350 Stage IV). Costs then declined towards quarterly means more similar among stages. Cumulative costs ranged from $131,032 (Stage I) to $205,368 (Stage IV). In the Stage I lobectomy cohort, patients selected for minimally invasive procedures had lower 4-year costs than thoracotomy patients ($120,346 versus $136,250). Conclusions: The 4-year cost of surgical resection for NSCLC was substantial and increased with pathologic stage. Among Stage I lobectomy patients, those selected for minimally invasive surgery had lower costs, particularly through 90 days. Potential avenues for improving the value of surgical resection include judicious use of post-operative intensive care and earlier detection and treatment of disease.
Background: Bovine digital dermatitis (BDD) is an infectious foot disease found commonly in dairy herds. Foot-trimming is an important husbandry procedure for reducing the ensuing lameness; however, epidemiological, and microbiological studies have identified this as a risk activity for transmitting BDD. Three disinfectants have previously been identified in laboratory work as effective for removing viable BDD-associated Treponema spp., from hoof knife blades. The present study enrolled 133 dairy cattle with BDD lesions, and swabbed hoof knife blades before and after foot-trimming, and after knife disinfection with one of three disinfectants (1:100 FAM30®, 2% Virkon® and 2% sodium hypochlorite) to assess their efficacy under field conditions. Results: Detection of BDD treponeme phylogroup DNA was undertaken by direct PCR of swabs, and viable treponemes were detected by PCR of swab cultures after 6 weeks' incubation. Where hoof knives did not contact the lesion, BDD-associated treponemes were detected after foot-trimming in 12/22 (54.5%) cases by direct PCR and 1/22 (4.5%) cases by PCR of cultured organisms. Where contact was made with the lesion, 111/111 (100%) samples taken after trimming were positive by direct PCR and 47/118 (39.8%) were positive by culture PCR. Viable organisms were identified in cultures from lesion stages M2, M3, M4 and M4.1. No viable organisms were detected after disinfection of hoof knives. Conclusions: Hoof knives post-trimming were frequently contaminated with BDD-associated treponeme DNA. Viable organisms were identified in cultures whether contact had been made between hoof knife and lesion or not, although contact clearly increased the frequency of detection of viable organisms. The three disinfectants tested were effective for removing viable organisms. The disinfection protocol used in this study should therefore be considered reliable for adoption as standard industry practice.
Controlling the spread of bovine digital dermatitis - Gareth J. Staton, Amy Gillespie, Nicholas J. Evans, Roger Blowey, Stuart D. Carter
Background Non-healing bovine foot lesions, including non-healing white line disease, non-healing sole ulcer and toe necrosis, are an increasingly important cause of chronic lameness that are poorly responsive to treatment. Recent studies have demonstrated a high-level association between these non-healing lesions and the Treponema phylogroups implicated in bovine digital dermatitis (BDD). However, a polymicrobial aetiology involving other gram-stain-negative anaerobes is suspected. Methods A PCR-based bacteriological survey of uncomplicated BDD lesions (n=10) and non-healing bovine foot lesions (n=10) targeting Fusobacterium necrophorum , Porphyromonas endodontalis, Dichelobacter nodosus and Treponema pallidum/T. paraluiscuniculi was performed. Results P. endodontalis DNA was detected in 80.0% of the non-healing lesion biopsies (p=<0.001) but was entirely absent from uncomplicated BDD lesion biopsies. When compared to the BDD lesions, F. necrophorum was detected at a higher frequency in the non-healing lesions (33.3% vs 70.0%, respectively), whereas D. nodosus was detected at a lower frequency (55.5% vs 20.0%, respectively). Conversely, T. pallidum/T. paraluiscuniculi DNA was not detected in either lesion type. Conclusion The data from this pilot study suggest that P. endodontalis and F. necrophorum should be further investigated as potential aetiological agents of non-healing bovine foot lesions. A failure to detect syphilis treponemes in either lesion type is reassuring given the potential public health implications such an infection would present.
Background Bovine digital dermatitis (BDD) is a painful infectious foot disease of cattle, and much evidence implicates a pathogenic role for treponemes. This study measured the survival of BDD treponemes on hoof knife blades and tested the efficacy of relevant disinfectants under laboratory conditions. Methods Two strains of BDD treponemes were applied to hoof knife blades under aerobic conditions. Swabs were taken at different time points (10 minutes, one hour, two hours, four hours and 18 hours) and again after 20-second disinfection time with one of five disinfectants. Swabs were used directly for nested PCR to detect treponemes or inoculated for anaerobic growth, and subsequently examined using phase contrast microscopy and PCR. Results BDD treponeme DNA was detectable by nested PCR at all survival time points, and these organisms were culturable from hoof knives for two hours after exposure under aerobic conditions in the laboratory. Three of the five disinfectants—1 per cent volume per volume (v/v) FAM30 ® , 2 per cent weight per volume (w/v) Virkon ® or 2 per cent (v/v) sodium hypochlorite—were effective at preventing visible growth of treponemes following 20-seconds contact, and 1 per cent (v/v) FAM30 ® also prevented detection of treponemes by PCR. Conclusion Treponeme viability of two hours under aerobic conditions suggests BDD treponemes could be transmitted between cows on hoof knives. It is therefore important to apply a disinfection protocol during foot-trimming; the authors have identified three common disinfectants that may be suitable.
Offshore industry has about three decades of experience with the development and deployment of floating and subsea technologies in deep (> 500 m) and ultra-deep (> 1,500 m) waters. Most of the ultra-deep water experience has been gained from fields in the Gulf of Mexico, Brazil, and West of Africa. Significant exploration and development activities undergoing in deep and ultra-deep waters of more than eight South American countries require low cost solutions to enable their development. This Panel will present and discuss the innovative initiatives undertaken by the industry for further development of solutions and technologies for deepwater production facilities (floating and subsea units, risers, umbilicals, flowlines and pipelines) to reduce their capital and operating costs. The innovative initiatives range from variations in the design and execution plans to qualification of specific new technologies. The digitalization of these facilities is also providing means to further reduce capital and operating costs and enhance productivity, safety, and reduce environmental impact. In addition, the potential value from renewable energy to subsea and field operations is being evaluated. These initiatives are in various stages of development and some are being implemented in deepwater fields in Brazil and Guyana. Several of these innovative technology initiatives will go from Technology Readiness Level (TRL) 5 to 7 in South American fields after operating for more than 3 years.
Aim To elicit the views and experiences of women with Type 2 diabetes and healthcare professionals relating to the pregnancy and pre‐pregnancy care they have received or provided. Methods A qualitative study using in‐depth semi‐structured interviews with women with Type 2 diabetes (n=30) and healthcare professionals (n=22) from primary and specialist care. Women were purposively sampled to include different experiences of pregnancy and pre‐pregnancy care. Data were transcribed verbatim and analysed thematically using framework analysis. Results The median age of the women was 37 years, and most were obese (median BMI 34.9 kg/m²), of black or Asian ethnicity (n=24, 80%) and from areas of high deprivation (n=21, 70%). Participating healthcare professionals were from primary (n=14), intermediate (n=4) and secondary (n=4) care. Seven themes expressing factors that mediate reproductive behaviour and care in women with Type 2 diabetes were identified at the patient, professional and system levels. Type 2 diabetes was generally perceived negatively by the women and the healthcare professionals. There was a lack of awareness about the pre‐pregnancy care needs for this population, and communication between both groups was unhelpful in eliciting the reproductive intentions of these women. The themes also reveal a lack of systemic processes to incorporate pre‐pregnancy care into the care of women with Type 2 diabetes, and, consequently, health professionals in primary care have limited capacity to provide such support. Conclusion If the current high levels of unprepared pregnancies in women with Type 2 diabetes are to be reduced, the reproductive healthcare needs of this group need to be embedded into their mainstream diabetes management. This article is protected by copyright. All rights reserved.
A series of engineering-scale multi-pass pipe girth weld mock-ups were manufactured using conventional manual metal arc techniques from Esshete 1250 austenitic steel. They were characterised in detail, in order to provide validation benchmarks for finite element prediction of weld residual stresses. The fabrication sequence comprised initial solution heat treatment and quenching, manufacture of five closely spaced girth welds in a single assembly, and then separation into five individual weldments. Detailed welding records were kept, to allow subsequent calibration of weld heat source models. Residual stresses were measured using diverse methods (incremental deep hole drilling and the contour method), in both the as-welded condition and after thermal ageing at 650 °C. The measurements showed good agreement, providing reliable validation targets for predicted residual stresses in both states. Detailed mechanical property characterisation was performed on both parent material and weld metal, comprising monotonic and isothermal cyclic testing over a range of temperatures from ambient up to 1000 °C. The test data were used to derive a range of Lemaitre-Chaboche mixed isotropic-kinematic model parameter sets for use in finite element simulation. These welds and their supporting characterisation comprise a reliable benchmark for weld residual stress simulation in an engineering-scale weldment.
Ocean currents are an important consideration throughout the life cycle of the many offshore projects. These currents are complex, three dimensional, dynamic and as yet poorly characterized in a statistical sense. Numerical ocean circulation models are increasingly sophisticated and are beginning to capture the structure and variability of complex ocean current systems. The starting point for model-based characterization of currents is a long time series of model outputs obtained at high spatial and temporal resolution. There are an ever-increasing number of model products, but it is not clear how to identify suitable products for a given application. Frequently, a familiar product is chosen that may not be the best choice. Here, we present an alternative approach wherein a collection of model runs, referred to as an ensemble, is used to estimate ocean current statistics at points of interest. Unlike other ensemble methods where the ensemble is used to estimate the statistics directly, we use the ensemble to construct a surrogate ocean model or an emulator using polynomial expansions. This emulator is computationally inexpensive to run and is used to sample the model outputs for large numbers of model inputs to generate full probability distributions of the model state, which can then be used to derive statistics required for design criteria. We have used the above technique to build an emulator for a numerical circulation model of the Gulf of Mexico. We present statistics of the Loop Current derived from this approach and briefly compare it with statistics obtained from measurements and other available long time-series of model outputs. Probability distributions for a sample point in the vicinity of the Loop Current are presented. It is shown that the technique can provide robust statistics and complements existing techniques.
Geometallurgy aims to improve mining project value by predicting the impact that ore and waste characteristics will have on mining and metallurgical processes. This requires integration of rich spatial models of orebody characteristics with validated process response models. These models have, until recently, been constrained by the spatial coverage and representativity of relevant data and the ability to validate predictions made. The revolution in the diversity and volume of data and computational power that is now becoming available for integrated geoscientific modelling of orebodies, and stochastic simulation of mining and mineral processes is accelerating. By embracing emergent integrated data analysis and simulation techniques, geoscientists and engineers can lead a transformation in the way the mining value chain, from orebody to recovery, can be conceived, evaluated, and operated by using the geometallurgical paradigm. This paper describes a methodology that is applied to an existing diamond operation. Analysis of spatial and process data is used to build an integrated geometallurgical value chain model (IGVCM). This IGVCM is used to generate geometallurgical options and evaluate their potential outcomes. The model facilitates the use of flexible, highly configurable, and potentially automated intelligent approaches to evaluate mining and mineral process configuration, and results in more robust design outcomes. The approach described here, and its successful implementation has potential to deliver step-changes in value.
Additional fatigue rules within the ASME Boiler and Pressure Vessel Code have been developed over the past decade or so, such as those in Code Case N-792-1 [1], which provides an acceptable method to describe the effects of BWR and PWR environments on the fatigue life of components. The incorporation of environmental effects into fatigue calculations is performed via an environmental factor, Fen, and depends on factors such as the temperature, dissolved oxygen and strain rate. In the case of strain rate, lower strain rates (i.e., from slow transients) aggravate the Fen factor which counters the long-held notion that step (fast) transients cause the highest fatigue usage. A wide range of other factors, such as surface finish, can have a deleterious impact on fatigue life, but their impact on fatigue life is typically considered by including transition sub-factors to construct the fatigue design curve from the mean behavior air curve rather than in an explicit way, such as the Fen factor. An extensive amount of testing and evaluation has been conducted and reported in References [2] [3] [4] [5] [6] [7] and [8] that were used to both revise the transition factors and devise the Fen equations contained in Code Case N-792-1. The testing supporting the definition of Fen was performed on small-scale laboratory specimens with a polished surface finish on the basis that the Fen factor is applicable to the design curve without any impact on the transition factors. The work initiated by AREVA in 2005 [4] [5] [6] suggested, in testing of austenitic stainless steels, an interaction between the two aggravating effects of surface finish and PWR environment on fatigue damage. These results have been supported by testing carried out independently in the UK by Rolls-Royce and AMEC Foster Wheeler (now Wood Group) [7], also on austenitic stainless steels. The key finding from these investigations is that the combined detrimental effects of a PWR environment and a rough surface finish are substantially less than the sum of the two individual effects. These results are all the more relevant as most nuclear power plant (NPP) components do not have a polished surface finish. Most NPP component surfaces are either industrially ground or installed as-manufactured. The previous studies concluded that explicit consideration of the combined effects of environment and surface finish could potentially be applicable to a wide range of NPP components and would therefore be of interest to a wider community: EDF has therefore authored a draft Code Case introducing a factor, Fen-threshold, which explicitly quantifies the interaction between PWR environment and surface finish, as well as taking some credit for other conservatisms in the sub-factors that comprise the life transition sub-factor used to build the design fatigue curve . The contents of the draft Code Case were presented last year [9]. Since then, other international organizations have also made progress on these topics and developed their own views. The work performed is applicable to Austenitic Stainless Steels only for the time being. This paper aims therefore to present an update of the draft Code Case based on comments received to-date, and introduces some of the research and discussions which have been ongoing on this topic as part of an international EPRI collaborative group on environmental fatigue issues. It is intended to work towards an international consensus for a final version of the ASME Code Case for Fen-threshold.
Background: The last published version of the Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database (ACSD) risk models were developed in 2008 based on patient data from 2002 to 2006 and have been periodically recalibrated. In response to evolving changes in patient characteristics, risk profiles, surgical practice, and outcomes, STS has now developed a set of entirely new risk models for adult cardiac surgery. Methods: New models were estimated for isolated coronary artery bypass grafting surgery (CABG, n = 439,092), isolated aortic or mitral valve surgery (n = 150,150), and combined valve + CABG (n = 81,588) procedures. The development set was based on July 2011 to June 2014 STS-ACSD data; validation was performed using July 2014 to December 2016 data. Separate models were developed for operative mortality, stroke, renal failure, prolonged ventilation, reoperation, composite major morbidity or mortality, and prolonged or short postoperative length of stay. Because of its low occurrence rate, a combined model incorporating all operative types was developed for deep sternal wound infection/mediastinitis (DSWI). Results: Calibration was excellent except for the DSWI model, which slightly underestimated risk due to higher rates of this endpoint in the more recent validation data; this will be recalibrated in each feedback report. Discrimination (c-index) of all models was superior to that of 2008 models except for the stroke model for valve patients. Conclusions: Completely new STS ACSD risk models have been developed based on contemporary patient data; their performance is superior to that of previous STS ACSD models.
Background: The Society of Thoracic Surgeons (STS) uses statistical models to create risk-adjusted performance metrics for Adult Cardiac Surgery Database (ACSD) participants. Because of temporal changes in patient characteristics and outcomes, evolution of surgical practice, and additional risk factors available in recent ACSD versions, completely new risk models have been developed. Methods: Using July 2011 to June 2014 ACSD data, risk models were developed for operative mortality, stroke, renal failure, prolonged ventilation, mediastinitis /deep sternal wound infection (DSWI), reoperation, major morbidity or mortality composite, and prolonged postoperative length of stay (PLOS) or short PLOS among patients who underwent isolated coronary artery bypass grafting (CABG; n = 439,092), aortic or mitral valve surgery (n = 150,150), or combined valve + CABG (n = 81,588). Separate models were developed for each procedure and endpoint except DSWI, which was analyzed in a combined model because of its infrequency. A surgeon panel selected predictors by assessing model performance and clinical face validity of full and progressively more parsimonious models. ACSD data (July 2014 to December 2016) were used to assess model calibration and to compare discrimination with previous STS risk models. Results: Calibration in the validation sample was excellent for all models except DSWI which slightly under-estimated risk and will be recalibrated in feedback reports. C-indices of new models exceeded those of the last published STS models for all populations and endpoints except stroke in valve patients. Conclusions: New STS ACSD risk models have generally excellent calibration and discrimination and are well suited for risk adjustment of STS performance metrics.
Drilling risers are an essential piece of equipment for drilling oil and gas wells offshore in water depths beyond those in which fixed offshore platforms can operate. Beyond these water depths, drilling can only be carried out from either specialized floating drilling units or floating production facilities. In either case, a drilling riser is typically employed to provide a conduit for running drilling tools and drill pipe from the floating unit to the seabed and to provide for well control and choke and kill operations. This article presents an introductory overview of drilling riser technology, describing the function and purpose of drilling risers, the main components of which they are comprised, and the main engineering and design issues that must be considered in their operation. The topic of well intervention, as it relates to drilling risers and more specialized workover riser systems, is also briefly discussed. Finally, some related technology developments that may help improve the economics of drilling offshore in deep and ultradeep waters are highlighted.
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Aberdeen, United Kingdom