Full Approximation Scheme for Reservoir Simulation

Simulation of multiphase flow and transport in porous rock formations give rise to large systems of strongly coupled nonlinear equations. Solving these equations is computationally challenging because of orders of magnitude local variations in parameters, mixed hyperbolic-elliptic governing equations, grids with high aspect ratios and strong coupling between local and global flow effects. The state-of-the-art solution approach is to use a Newton-type solver with a algebraic multigrid preconditioner for the elliptic part of a linearized system. Herein, we discuss the use and implementation of a Full Approximation Scheme (FAS) in which algebraic multigrid is applied on a nonlinear level. By use of this method, global and semi-global nonlinearities can be resolved on the appropriate coarse scale. Improved nonlinear convergence is demonstrated on standard benchmark cases from the petroleum literature. The method is implemented in the solver framework of the open-source Matlab Reservoir Simulation Toolbox (MRST).&nbsp

Transitioning from child to adult: safeguarding practice for young people who have experienced child sexual exploitation: systematic review

Child Sexual Exploitation is a pressing issue of social injustice about which professional learning is urgently needed. It is now recognised that sexual exploitation can continue beyond the age of 18 and that its impact can stay with young people well after they turn 18. Many welfare services are organised in response to the perceived needs of either children or adults, and this can mean that the needs of young people of a ‘transitional’ age fall between the two. It is timely to draw together what is currently known about safeguarding children, young people and young adults aged 16-25, from the past 20 years of research on sexual exploitation. The voices of children and young people who have experienced CSE and recognition of the complexity of their lives needs to be central to understanding what are appropriate responses and interventions from services, communities and support networks

Source of oceanic magnetic anomalies and the geomagnetic polarity time scale

Marine magnetic anomalies provide the framework for the geomagnetic polarity timescale for the Late Jurassic to Recent (since 160 Ma). Magnetostratigraphic records confirm that the polarity reversal sequence interpreted from magnetic anomalies is complete to a resolution of better than 30 ky. In addition to this record of polarity reversals, magnetic anomalies also appear to preserve information on geomagnetic intensity fluctuations. The correspondence of coherent near-bottom anomaly variations with independent estimates of field intensity provides strong evidence that geomagnetic intensity modulates the magnetization of the ocean crust. Indeed, many short wavelength anomaly variations in sea-surface magnetic profiles over fast-spreading ridges are likely attributable to geomagnetic intensity variations. Although longer-term geomagnetic field behavior may also be reflected in anomaly amplitudes, documenting such a signal requires a better understanding of time-dependent changes in the magnetic source (e.g., from low-temperature alteration) that may also affect magnetic anomalies. The extrusive layer, with an average remanence of ∼ 5 A m−1, is the largest contributor to magnetic anomalies. However, enhanced sampling of oceanic gabbros (average remanence ∼ 1 A m−1) and, to a lesser extent, dikes (average remanence ∼ 2 A m−1) reveals that these deeper (and thicker) layers likely generate anomalies comparable to those from the lavas. Lava accumulation at intermediate- and fast-spreading ridges typically occurs over a narrow (1–3 km) region and dike emplacement is even more narrowly confined, resulting in a relatively high fidelity record of geomagnetic field behavior. The slow cooling of the gabbroic layer, however, results in gently dipping polarity boundaries that significantly affect the skewness of the resulting anomalies, which is also a sensitive measure of net rotations of the source layer(s). The magnetizations of the dikes and gabbros are characterized by high stability and are not expected to significantly change with time, although there are insufficient data to confirm this. The lavas, however, typically show evidence of low-temperature alteration, which has been long regarded as a process that progressively reduces the magnetization (and degrades the geomagnetic signal) in the extrusive layer and reduces the amplitude of magnetic anomalies. Sufficient data have become available to examine this conventional wisdom. There is a substantial (∼ 4x) reduction in magnetization from on-axis samples to immediately off-axis drillsites (∼ 0.5 My), but little further change in half-dozen or so deep crustal sites to ∼ 160 Ma. High paleointensity that characterizes the last few thousand years may contribute significantly to the high on-axis magnetization. The task of evaluating changes in remanence of the extrusive layer is made more difficult by substantial cooling-rate-dependent changes in magnetic properties and the systematic variation in remanence with iron content (magnetic telechemistry). The commonly cited magnetic anomaly amplitude envelope is in fact not systematically observed – the Central Anomaly is elevated at slow-spreading ridges but is not as prominent at faster spreading rates. Nonetheless, magnetic anomaly amplitudes are consistent with magnetization change is poorly constrained. Direct determinations of the degree of low-temperature oxidation reveal the presence of highly oxidized titanomagnetite in samples less than 1 My old, suggesting a short (∼ 105 years) time constant though the effects of low-temperature oxidation are quite heterogeneous. While low-temperature oxidation does have some affect on lava magnetization and anomaly amplitudes, there is increasing evidence that marine magnetic anomalies are capable of recording a broad spectrum of geomagnetic field behavior, ranging from millennial-scale paleointensity variations to polarity reversals to apparent polar wander to, more speculatively, long-term changes in average field strength. Several emerging tools and approaches – autonomous vehicles, oriented samples, absolute paleointensity of near-ridge lavas, and measurements of the vector anomalous field – are therefore likely to significantly advance our understanding of the geomagnetic signal recorded in the oceanic crust, as well as our ability to utilize this information in addressing outstanding problems in crustal accretion processes

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Urban blue: A global analysis of the factors shaping people's perceptions of the marine environment and ecological engineering in harbours.

Marine harbours are the focus of a diverse range of activities and subject to multiple anthropogenically induced pressures. Support for environmental management options aimed at improving degraded harbours depends on understanding the factors which influence people's perceptions of harbour environments. We used an online survey, across 12 harbours, to assess sources of variation people's perceptions of harbour health and ecological engineering. We tested the hypotheses: 1) people living near impacted harbours would consider their environment to be more unhealthy and degraded, be more concerned about the environment and supportive of and willing to pay for ecological engineering relative to those living by less impacted harbours, and 2) people with greater connectedness to the harbour would be more concerned about and have greater perceived knowledge of the environment, and be more supportive of, knowledgeable about and willing to pay for ecological engineering, than those with less connectedness. Across twelve locations, the levels of degradation and modification by artificial structures were lower and the concern and knowledge about the environment and ecological engineering were greater in the six Australasian and American than the six European and Asian harbours surveyed. We found that people's perception of harbours as healthy or degraded, but not their concern for the environment, reflected the degree to which harbours were impacted. There was a positive relationship between the percentage of shoreline modified and the extent of support for and people's willingness to pay indirect costs for ecological engineering. At the individual level, measures of connectedness to the harbour environment were good predictors of concern for and perceived knowledge about the environment but not support for and perceived knowledge about ecological engineering. To make informed decisions, it is important that people are empowered with sufficient knowledge of the environmental issues facing their harbour and ecological engineering options

A General Nonlinear Reservoir Simulator with the Full Approximation Scheme

Simulation of multiphase flow and transport in porous rock formations gives rise to large systems of strongly coupled nonlinear equations. Solving these equations is computationally challenging because of orders of magnitude local variations in parameters, mixed hyperbolic-elliptic character, grids with high aspect ratios, and strong coupling between local and global flow effects. The state-of-the-art solution approach is to use a Newton-type solver with an algebraic multigrid preconditioner for the elliptic part of the linearized system. Herein, we discuss the use and implementation of a full approximation scheme (FAS), in which algebraic multigrid is applied on a nonlinear level. By use of this method, global and semi-global nonlinearities can be resolved on the appropriate coarse scale. Improved nonlinear convergence is demonstrated on standard benchmark cases from the petroleum literature. The method is implemented in the solver framework of the open-source Matlab Reservoir Simulation Toolbox (MRST). With this framework, the implemented FAS method can be applied on a broad range of classes of discrete reservoir and fluid models

Full Approximation Scheme for Reservoir Simulation

Simulation of multiphase flow and transport in porous rock formations give rise to large systems of strongly coupled nonlinear equations. Solving these equations is computationally challenging because of orders of magnitude local variations in parameters, mixed hyperbolic-elliptic governing equations, grids with high aspect ratios and strong coupling between local and global flow effects. The state-of-the-art solution approach is to use a Newton-type solver with a algebraic multigrid preconditioner for the elliptic part of a linearized system. Herein, we discuss the use and implementation of a Full Approximation Scheme (FAS) in which algebraic multigrid is applied on a nonlinear level. By use of this method, global and semi-global nonlinearities can be resolved on the appropriate coarse scale. Improved nonlinear convergence is demonstrated on standard benchmark cases from the petroleum literature. The method is implemented in the solver framework of the open-source Matlab Reservoir Simulation Toolbox (MRST)