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Asymmetric gradient coils introduce zeroth- and first-order concomitant field terms, in addition to higher-order terms common to both asymmetric and symmetric gradients. Salient to compensation strategies is the accurate calibration of the concomitant field spatial offset parameters for asymmetric coils. A method that allows for one-time calibration of the offset parameters is described.A modified phase contrast pulse sequence with single-sided bipolar flow encoding is proposed to calibrate the offsets for asymmetric, transverse gradient coils. By fitting the measured phase offsets to different gradient amplitudes, the spatial offsets were calculated by fitting the phase variation. This was used for calibrating real-time pre-emphasis compensation of the zeroth- and first-order concomitant fields.Image quality improvement with the proposed corrections was demonstrated in phantom and healthy volunteers with non-Cartesian and Cartesian trajectory acquisitions. Concomitant field compensation using the calibrated offsets resulted in a residual phase errorlt;3% at the highest gradient amplitude and demonstrated substantial reduction of image blur and slice position/selection artifacts.The proposed implementation provides an accurate method for calibrating spatial offsets that can be used for real-time concomitant field compensation of zeroth and first-order terms, substantially reducing artifacts without retrospective correction or sequence specific waveform modifications.

Background Outcomes of patients admitted for acute heart failure (AHF) are generally poor, then it is important to recognize outcome predictors in order to better identify and manage patients at higher risk. Aims To identify independent predictors of 1-year all-cause death in AHF patients enrolled by Italian cardiology sites participating to the BLITZ-HF study. Methods BLITZ-HF was a prospective nationwide study based on a web based recording system used during two enrollment periods (08/03/2017 – 04/09/2017 and 24/12/2017 – 09/04/2018). Overall, 7218 patients with acute and chronic HF were enrolled by 106 sites, 58 were lost to follow-up. Patients were followed for a median of 370 days [IQR 339–395]. Cox proportional hazards models were used to identify the independent predictors of all-cause death from hospital admission to 1-year follow-up. Demographic variables and baseline characteristics statistically significant at univariate analysis were included in the multivariable models. Different Cox proportional models were fitted: 1) adjusted for age and gender, 2) model 1 + clinical variables, 3) model 2 + laboratory and instrumental examinations, 4) model 3 + therapy. Results The present analysis refers to the 1470 patients admitted for AHF not lost to follow-up. Mean age was 73±12, with nearly 50% having more than 75 years of age. Female gender accounted for about one third of cases. More than half were de novo HF patients and 43% had an ischemic aetiology. Nearly 40% had a history of atrial fibrillation (AF) and chronic kidney disease (CKD) and one fifth had a history of COPD and peripheral obstructive artery disease. Furthermore, mean systolic blood pressure (SBP) on admission was 131±28 and, heart rate (HR) was 91±25. The majority of HF patients had reduced EF (HFrEF) (58%), followed by HF with preserved EF (HFpEF) (24%) and HF with mid range EF (HFmrEF) (18%). One year all-cause mortality was 16.6%. Independent predictors of all-cause mortality are shown in the Table. In the final model adjusted for age, gender, clinical variables, laboratory and instrumental examinations and medical treatments, the following variables resulted as independent predictors of one-year all-cause mortality: age (HR 1.02), Confuse/obnubilate mental status (HR 2.07), creatinine >1.5 mg/dl (HR 1.54), BUN >43 mg/dl, (HR 2.74), aortic stenosis (HR 1.70), inotrope use (HR 1.43), IV furosemide >125 mg (HR 1.74), SBP (HR 0.99). Conclusions In our study several independent predictors of one-year all-cause mortality have been identified, confirming and reinforcing previous findings. Interestingly, our independent predictors derived from different domains (demographic, clinical, biohumoral, instrumental and treatment variables). These findings further underline the importance of a comprehensive assessment in the prognostic evaluation of AHF patients. Funding Acknowledgement Type of funding sources: Private company. Main funding source(s): The study was funded by Heart Care Foundation with a partial unrestricted support from Abbott, Daiichi Sankyo, Medtronic, Servier, Vifor.

Purpose Imaging gradients result in the generation of concomitant fields, or Maxwell fields, which are of increasing importance at higher gradient amplitudes. These time-varying fields cause additional phase accumulation, which must be compensated for to avoid image artifacts. In the case of gradient systems employing symmetric design, the concomitant fields are well described with second-order spatial variation. Gradient systems employing asymmetric design additionally generate concomitant fields with global (zeroth-order or B0) and linear (first-order) spatial dependence. Methods This work demonstrates a general solution to eliminate the zeroth-order concomitant field by applying the correct B0 frequency shift in real time to counteract the concomitant fields. Results are demonstrated for phase contrast, spiral, echo-planar imaging (EPI), and fast spin-echo imaging. Results A global phase offset is reduced in the phase-contrast exam, and blurring is virtually eliminated in spiral images. The bulk image shift in the phase-encode direction is compensated for in EPI, whereas signal loss, ghosting, and blurring are corrected in the fast-spin echo images. Conclusion A user-transparent method to compensate the zeroth-order concomitant field term by center frequency shifting is proposed and implemented. This solution allows all the existing pulse sequences—both product and research—to be retained without any modifications. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine.

A technique has been developed to allow for the comparison of scavenging rates and scavenging capacity of different hydrogen sulphide scavengers by continuously measuring the hydrogen sulphide concentration in the gas phase of a multiphase system. In addition, the stability of the scavenger reaction products has also been investigated. The methodology to assess the performance of the hydrogen sulphide scavenger is described. The scavenging rates of the hydrogen sulphide scavenger are compared by the contact time required to reduce the initial hydrogen sulphide concentration to a pre-determined value. In addition, the scavenging capacity of the scavengers can be calculated by recording the gaseous hydrogen sulphide concentration once the reaction has been allowed to run to completion. Finally, the stability of the scavengers and their reaction products, including carbon disulphide, are determined by treating a solution of the scavenger with excess hydrogen sulphide. It is known that hydrogen sulphide scavengers have the potential to form reaction products that can foul the refining process. More recently, it has been identified that carbon disulphide may be produced during the scavenging reaction of some commonly used triazine based chemistries, driving a desire to identify alternative products. These works describe a new method which is capable of differentiating between the hydrogen sulfide scavenging performance of different chemistries. It also allowed for the scavengers to be differentiated with respect to the formation of both solid and oil soluble by-products, with the presence / increase in carbon disulphide analysed by gas chromatography. By doing this, the method allows for improved scavenger selection on the basis of performance, compatibility and cost. This work presents a novel method for the assessment of relative reaction rates and scavenging capacity of hydrogen sulphide scavengers. In doing so, it allows the evaluation of cost performance and suitability of different treatments and scavenger chemistries to be evaluated. Additionally, the likelihood of a scavenger chemistry fouling the refining process due to the production of reaction by-products can be investigated.

Purpose To develop a gradient pre-emphasis scheme that prospectively counteracts the effects of the first-order concomitant fields for any arbitrary gradient waveform played on asymmetric gradient systems, and to demonstrate the effectiveness of this approach using a real-time implementation on a compact gradient system. Methods After reviewing the first-order concomitant fields that are present on asymmetric gradients, we developed a generalized gradient pre-emphasis model assuming arbitrary gradient waveforms to counteract their effects. A numerically straightforward, easily implemented approximate solution to this pre-emphasis problem was derived that was compatible with the current hardware infrastructure of conventional MRI scanners for eddy current compensation. The proposed method was implemented on the gradient driver subsystem, and its real-time use was tested using a series of phantom and in vivo data acquired from two-dimensional Cartesian phase-difference, echo-planar imaging, and spiral acquisitions. Results The phantom and in vivo results demonstrated that unless accounted for, first-order concomitant fields introduce considerable phase estimation error into the measured data and result in images with spatially dependent blurring/distortion. The resulting artifacts were effectively prevented using the proposed gradient pre-emphasis. Conclusion We have developed an efficient and effective gradient pre-emphasis framework to counteract the effects of first-order concomitant fields of asymmetric gradient systems. Magn Reson Med 77:2250–2262, 2017. © 2016 International Society for Magnetic Resonance in Medicine

Methods currently used to evaluate laboratory performance of asphaltenes inhibitors are non-optimal because the conditions used are so far from those prevailing in the field, leading to incorrect assessment of dose rates or even selection of chemicals that may not be beneficial at all. We present a dynamic flow test method for asphaltenes risk assessment and inhibitor qualification that uses field-representative temperature, pressure and fluid dynamics to enable successful correlation with field behaviour.This paper discusses the most commonly used laboratory test methods for asphaltenes testing and proposes a new dynamic flow method that offers a significant improvement over other widely-used techniques. Reconditioned dead crude oil is co-injected with n-heptane through a steel capillary and an inline filter. Differential pressures are recorded to monitor the extent of asphaltenes precipitation and deposition. We highlight key parameters that should be optimised to ensure that chemical performance is tested against the actual functionality required in the field and under conditions that are as representative as practicable.We present a case study describing the use of the dynamic flow test equipment to assess asphaltenes deposition risk and to qualify asphaltenes inhibitors for field application. We demonstrate that the method is able to rank chemicals for performance at inhibiting deposition under flowing conditions and at more field-representative temperature and pressure, with much lower percentages of n-heptane than required for conventional dispersancy testing.We discuss the effect of critical parameters affecting the extent of asphaltenes deposition. Fluid dynamics are recognised to play a key role in asphaltenes deposition in the field, not least, because at higher wall velocities the erosive force acting on field deposits is high enough to limit further growth and steady state can be reached. Flowing tests were conducted under a number of fluid-dynamic regimes in which asphaltenic crude oil was destabilised by addition of n-heptane. The effects of wall shear stress, wall velocity, residence time, and other factors were evaluated upon asphaltenes deposition in a steel capillary and upon bulk precipitation by subsequent filtration. The results obtained from laboratory tests correlate well with field observations and demonstrate that flow regimes in laboratory tests can approach those occurring in the field.This paper presents the development of a new laboratory test method utilising dead crude both for asphaltenes risk assessment and inhibitor qualification that offers significantly improved correlation with field behaviour over conventional dispersancy testing, yet remains much more cost effective than labour-intensive autoclave testing utilising live fluids. When considering asphaltenes risk analysis the approach also allows for deposition vs. precipitation to be examined under field realistic conditions, and we demonstrate how this can be of significant importance when, for example, introducing gas lift into asphaltenic crudes.

Accurate scale prediction modelling is only possible when reliable mineral solubility data are available under the required conditions. It is recognised that the relative paucity of high pressure, high temperature (HPHT) solubility data can result in inaccurate predictions as current models extrapolate from data obtained under more conventional conditions. This paper describes the generation of additional fundamental solubility data under HPHT conditions and comparison of the obtained values with several existing models. A purpose-built laboratory test rig capable of making mineral solubility measurements up to 250 °C (480 °F) and up to 30,000 psi has been used in this work. Experimental solubility data have been generated for calcium sulphate at different temperatures and the methodology has been investigated to ensure that equilibrium conditions have been reached. In this work, barium sulphate solubility data have also been generated at conditions up to 200 °C (390 °F) and 19,000 psi. Notably, the solubilities have been determined in the presence of relatively high concentrations of additional ions, e.g., calcium, as it was recognised that available data were limited for more oilfield-representative brine compositions from HPHT reservoirs. The data generated were also compared against solubility predictions for a range of industry models to assess their accuracy in these circumstances. The results obtained for calcium sulphate solubility indicate the importance of validating the test methodology, not just for each mineral, but also under the required temperature and pressure conditions, to verify that equilibrium solubility conditions have been achieved. Barium sulphate solubility increases with the addition of other divalent ions but the extent of the increase is at present not accurately predicted by existing scale prediction models at HPHT conditions. In some cases, the predicted barium sulphate solubility was up to three times greater than the experimentally determined value. It is apparent that there is considerable scope for improvement of scale prediction models under HPHT conditions particularly in complex brine systems and that further fundamental solubility data are required to facilitate this. This paper provides additional data for mineral solubility under HPHT conditions but, more importantly, shows data for complex brines that are more representative of those produced in oilfields. The work further demonstrates the limitations of existing scale prediction modelling software under HPHT conditions, particularly in the presence of other divalent ions, and illustrates areas where additional data and model development is critical to enable more accurate modelling of scale risk under these conditions.

Inflow Control Devices (ICDs) are being increasingly used in complex, heterogeneous reservoirs to make the inflow profile more uniform, delay breakthrough of water and/or gas and limit differential depletion, which can lead to crossflow and other detrimental phenomena. However, ICDs not only alter inflow behaviour: they also affect outflow of fluid during chemical treatments, such as scale squeezes, stimulation, etc., which may be applied periodically during well life. Methods to account for the additional flow resistance from ICDs when predicting placement of bullheaded treatments are discussed in this paper, in particular, to evaluate whether a theoretical approach based upon Bernoulli's Theorem leads to sufficiently accurate predictions in the absence of laboratory correlations between pressure drop across the ICD and flow rate. This approach may also become significant where the laboratory calibration might be expected to have changed during well life, such as, under the influence of erosion. The paper describes two analytical methods of simulating placement in a multi-zone well in a heterogeneous reservoir in the Middle East: the first is empirical and models the pressure drop using an equation derived from calibration data in the laboratory; the second uses the Bernoulli equation, and is theoretical. For the empirical approach, the laboratory-based pressure-drop/flowrate calibration data were fitted to an equation, with parameters that depended upon the nozzle dimensions. The theoretical approach calculated the pressure drop using the Bernoulli equation for a cylindrical ICD nozzle. Both methods were used to simulate placement of a generic scale-inhibitor squeeze treatment and the corresponding chemical returns for each zone in the well. In general, the differences in the predictions between the two models were found to be very minor, showing that a theoretical approach is sufficiently accurate to design and evaluate chemical treatments in wells fitted with ICDs in most cases. This means a very rapid analytical approach can be used to design and evaluate near-wellbore treatments in such wells without resorting to much more complex, numerical-based reservoir simulators, even when calibration data about the ICD performance are not available.

Selection of effective corrosion for use in high wall shear conditions is of increasing importance in oilfield production. Development of new oil and gas fields often requires the use of more sophisticated downhole equipment. As a result these production conditions can result in exceptionally high wall shear stress, for example in-flow control devices (ICDs) can reach shear stresses up to 10,000 Pa. To accommodate this, there is need for more representative high shear tests for material and production chemical selection. A jet impingement test procedure is shown that allows for the evaluation of products under such environments. Further to this the shear stresses generated in standard laboratory tests have been compared with a high flow pilot rig and comparative Computational Fluid Dynamics (CFD) modelling. A test system has been developed that allows routine laboratory evaluation of corrosion processes at moderate to high shear stresses using jet impingement methodology. A series of tests have been conducted to determine the extent of corrosion under moderate to high shear conditions. Static tests and low shear rotating cylinder electrode (RCE) tests have been carried out using the same brine system to allow comparison of results from the different methods. Ultimately, high flow (moderate to high shear) pilot rig tests have also been used to verify the results. The results show that the jet impingement approach is effective in generating field representative conditions, which in turn can support material or chemical selection. The work presented is supported by case studies which will be illustrated. In order to test effectively, the flow regimes experienced in the field must be replicated. Using CFD models we demonstrate that the observed field conditions can be reproduced using these laboratory flow regimes and produce results that correlate well.

Laboratory-based assessments of corrosion inhibitors for chemical qualification generally rely on approaches designed to replicate all key aspects of the corroding environment (ppCO2, field crude, brine composition, system temperature, pressure, wall shear, etc.). However, the time and costs associated with testing under fully field representative conditions (e.g. High Pressure/ High Temperature (HP/HT) autoclave or flow loop tests), often restrict the use of such tests to chemicals at dose rates pre-qualified by simpler screening tests, especially when many different formulations are submitted for potential qualification.This paper includes illustrative examples of how apparently small changes to the test methodology in these preliminary screening tests can have significant influence on the relative ranking and absolute performance of the chemicals tested, specifically:the effect of pre-corrosion; adjustment of brine chemistry to avoid artefacts from scale deposition; appropriate pH control (representative of the in situ field conditions where high ppCO2 may be present) partitioning between hydrocarbon and aqueous phases can be affected by minor procedural differences.The net effect is that product ranking can be significantly affected, potentially leading to the qualification of less effective products, or more significantly to the de-selection of otherwise effective products, prior to the more detailed field representative autoclaves / flow loops. More so, since many of the artefacts can be transferred from the screening tests to the field representative tests, product performance and ranking in the more field representative HP/HT tests can also be affected, if critical control of the test conditions is not adhered to.Examples are provided from both generic corrosion inhibitor formulations as well as case studies using field specific formulations. This will assist in improving the design of corrosion inhibitor screening programs and eliminating common errors and artefacts.

With developing interest in unconventional fields, such as fractured shales, there has been a need to develop models that accurately reflect the fluid-transport mechanisms in such formations. The current paper does this from the viewpoint of modelling scale inhibitor squeeze treatments. Unlike conventional reservoirs, where chemical transport is dominated by pressure differentials from pumping, in ultra-low permeability systems imbibition and diffusion processes can be as important, if not more so. We report a model that numerically solves either the imbibition equation or Fick's second law of diffusion to simulate these transport mechanisms, and couples these processes to inhibitor adsorption and desorption using either Freundlich or Langmuir isotherms. As only a fraction of the production interval is typically treated, the model interactively allows the user to select which fractures have been treated. The influence of partial treatment of the fracture network on overall treatment effectiveness is presented as is the effect of varying entry location of the produced water into the well. The model was also developed to simulate spontaneous imbibition of the aqueous inhibitor solution in combination with inhibitor adsorption, albeit in the absence of diffusion. The effect of this imbibition has been evaluated from the perspective that it acts as a potential "treatment thief" because it preferentially transports the applied inhibitor solution into oil-producing zones, whence it should contribute very little to mitigation of the current scaling risk.

The relative paucity of reliable experimental data for calcium sulphate solubility under ultra HPHT conditions and in complex brines characteristic of oilfield formation waters means that scale-prediction models used to design and manage such fields are compromised by the need to rely on extrapolations from more conventional operating conditions, and simple brines. This work describes the measurement of new experimental solubility data using a purpose-built laboratory test rig capable of attaining 250 °C and 25,000 psi. This has been used to measure the solubility of calcium sulphate minerals in brines of various salinities as well as their degree of dissolution under long residence time equilibrium conditions and low-flow, shorter residence time, steady-state conditions. Methods of approaching equilibrium via dissolution were compared with those by precipitation of a supersaturated solution in the presence of crushed mineral. In addition, the result of using anhydrite or gypsum has been examined. The data generated were compared with the predictions of various thermodynamic electrolyte software packages. Laboratory tests show that an extended shut-in period for dissolution tests is required to reach equilibrium at 50 °C. Similar tests at 150°C required shorter equilibration times, but these were still longer than the 18-minute contact times for slow flow tests. Precipitation tests were shown to reach equilibrium over much shorter residence times. Additional thermodynamic equilibrium measurements are also provided here at 50 and 150 °C at 10,000 and 19,000 psia for ZnS and PbS, which again show considerable variance to that currently predicted from available software. This paper provides additional fundamental experimental data relating to mineral solubility and describes the importance of ensuring the methodology adopted for different minerals is assessed to ensure that true equilibrium solubility data are reported. The data obtained can be used to improve the modelling of CaSO4 under ultra-HPHT conditions and Pb/ZnS under typical downhole HT/HP and topside conditions. In addition, it provides an indication of the limitations in current brine prediction software that the industry relies on, thereby illustrating the need for updated models in this area.

Imaging gradients result in the generation of concomitant fields, or Maxwell fields, which are of increasing importance at higher gradient amplitudes. These time-varying fields cause additional phase accumulation, which must be compensated for to avoid image artifacts. In the case of gradient systems employing symmetric design, the concomitant fields are well described with second-order spatial variation. Gradient systems employing asymmetric design additionally generate concomitant fields with global (zeroth-order or BThis work demonstrates a general solution to eliminate the zeroth-order concomitant field by applying the correct BA global phase offset is reduced in the phase-contrast exam, and blurring is virtually eliminated in spiral images. The bulk image shift in the phase-encode direction is compensated for in EPI, whereas signal loss, ghosting, and blurring are corrected in the fast-spin echo images.A user-transparent method to compensate the zeroth-order concomitant field term by center frequency shifting is proposed and implemented. This solution allows all the existing pulse sequences-both product and research-to be retained without any modifications. Magn Reson Med 79:1538-1544, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Background Intestinal ischemia and reperfusion (I/R) injury leads to abnormalities in motility, namely delay of transit, caused by damage to myenteric neurons. Alterations of the nitrergic transmission may occur in these conditions. This study investigated whether an in vitro I/R injury may affect nitric oxide (NO) production from the myenteric plexus of the guinea pig ileum and which NO synthase (NOS) isoform is involved. Methods The distribution of the neuronal (n) and inducible (i) NOS was determined by immunohistochemistry during 60 min of glucose/oxygen deprivation (in vitro ischemia) followed by 60 min of reperfusion. The protein and mRNA levels of nNOS and iNOS were investigated by Western-immunoblotting and real time RT-PCR, respectively. NO levels were quantified as nitrite/nitrate. Key Results After in vitro I/R the proportion of nNOS-expressing neurons and protein levels remained unchanged. nNOS mRNA levels increased 60 min after inducing ischemia and in the following 5 min of reperfusion. iNOS-immunoreactive neurons, protein and mRNA levels were up-regulated during the whole I/R period. A significant increase of nitrite/nitrate levels was observed in the first 5 min after inducing I/R and was significantly reduced by Nω-propyl-l-arginine and 1400 W, selective inhibitors of nNOS and iNOS, respectively. Conclusions & Inferences Our data demonstrate that both iNOS and nNOS represent sources for NO overproduction in ileal myenteric plexus during I/R, although iNOS undergoes more consistent changes suggesting a more relevant role for this isoform in the alterations occurring in myenteric neurons following I/R.

Calcium carbonate scale control during Alkaline Surfactant Polymer (ASP) flooding is a recognised challenge due to mixing of the high-pH ASP waters with reservoir brine. In most cases ASP flooding is aimed towards reservoirs containing low-calcium and magnesium formation waters, and previous reports have concluded that in such cases production well scaling can be effectively treated with conventional scale inhibitors. For reservoirs containing moderate to high levels of alkaline-earth metal ions in the produced waters, such as reservoirs that have been flooded with sea water, the scaling risk is considerably exacerbated, with the result that conventional scale inhibitors are essentially ineffective except at very low sea-water fractions in the produced water mixture following ASP breakthrough. This paper presents the results for an extensive research and development project firstly to examine alternative inhibitor chemistries and then to develop more complex formulations containing synergistic additives to improve calcium carbonate scale control in high sea-water content produced waters in ASP floods. The developed formulations are shown to control the scales effectively with water chemistries that were previously shown to be beyond the efficacy of conventional inhibitors (negligible effect at 500 mg/l). The paper will present and discuss the different types of scale inhibitor chemistries examined, the nature of other chemistries and additives examined in combination with the scale inhibitors, and will describe the synergistic effects observed between the different chemicals. Results from this extensive series of laboratory tests will then be presented showing the considerable benefits of the new formulations and demonstrating how scale inhibition can now be achieved under these extreme and previously uncontrollable producer well conditions. The paper will also introduce the challenges and present an overview of the case study that initiated this development program.

This paper describes a laboratory and modelling study into halite (sodium chloride, rock salt) deposition in mature gas production wells. Halite deposition can result in significant production and integrity issues, and mitigation measures are primarily based upon injection of low-salinity wash water, often coupled with careful control of production parameters (such as well drawdown), for which scale-prediction models are used. Laboratory investigation of halite scaling and performance of halite inhibitors typically uses the mixing of incompatible brines or cooling a saturated solution, either in bottle tests or using a dynamic scale rig. While these methods allow precipitation kinetics and inhibitor performance to be examined, they are far from ideal as they require significant modification of the brine chemistry and deposition conditions. In this paper, we describe a novel approach to laboratory investigation of halite deposition that much more closely mimics the evaporative scaling mechanism mostly widely experienced in the field, and can be performed using produced-water compositions and conditions that are much more representative of the field. It is based upon a dynamic, flowing system where field-representative formation water is co-injected with gas at an appropriate level of under-saturation in water content to that expected under production conditions. Electrolyte prediction software was used to model the halite scaling tendency in the experiments, and very good correlation was found between the prediction of supersaturation and the onset of precipitation and deposition. This agreement implies that the scale-prediction model is accurate for halite scaling via this mechanism, and adds much confidence to the use of this tool for optimizing production parameters to minimize the effects of halite scaling in the field. The work also confirms earlier reports that the critical scaling tendency for halite – the value at which significant precipitation and deposition occurs in the field – is very close to unity for the conditions tested in this work. The new laboratory method was also used to generate calcium carbonate scaling by the mechanism – primarily transfer of CO2 to the gas phase – that is by far the predominant one found in the field; this led to observation of a mixed halite/calcium carbonate deposit.

Inorganic scale formation in oilfield systems is greatly influenced by the fluid-flow regime, with shear rates and turbulence affecting nucleation, surface growth, morphology and adhesion. However, current scaling risk analysis relies upon thermodynamics-based predictions together with simple rules-of-thumb to address kinetics because the impact of flow regime is poorly understood. Similarly, scale inhibitor performance is typically evaluated under static or low-shear, laminar-flow conditions, which are highly unrepresentative of those in most production systems. This paper examines scale deposition at metal surfaces and bulk-phase precipitation as a function of shear and turbulence, highlighting how rate and even scale composition can change in systems with mildly oversaturated sulphate tendencies. Conventional static and low-shear methods are compared with those using rotating cylinder and jet impingement to achieve high Reynolds numbers and shear stresses up to 400 Pa (and even 10,000 Pa via more sophisticated approaches). This builds upon earlier work (SPE 169761) and demonstrates the influence of fluid-flow dynamics on the critical supersaturation required to induce scaling, and by extension, on the nature of the deposit that may form where a system is mildly oversaturated for more than one scale. An example is where a sulphate scale at lower supersaturation precipitates under high shear conditions preferentially over another sulphate scale with higher supersaturation. This work also highlights the significance of better matching shear and turbulence in the ranking of scale inhibitors, reporting differences in the relative performance of different generic inhibitors as a function of shear. Finally, the paper describes the new test methods by which scaling propensity and inhibitor performance can be determined under conditions of shear and turbulence that are more representative of production conditions. A key aspect of this is that it facilitates testing of mildly supersaturated systems without having to adjust brine chemistry, leading to better understanding of the magnitude of uncontrolled scaling and of the Minimum Effective Dose of inhibitors to control it.

Scale inhibitor squeeze treatments in high-permeability sandstone reservoirs can be readily simulated using matrix flow models. However, designing such treatments for application in fractured shale reservoirs is less developed, partly because the mechanisms for fluid flow are less well understood and partly because the manner by which the inhibitors are transported and retained in fractured shale formations differ considerably from the simple matrix flow encountered in sandstone reservoirs. Accurate prediction of squeeze treatment lifetimes is important for scale management both economically, to ensure optimum productivity at lowest cost of operation, and practically, to schedule treatments appropriately. Until recently this has not been achievable for fractured shale formations without the use of full-field simulators. This paper demonstrates that even a near-wellbore model, if appropriately modified, can achieve good agreement with inhibitor-returns field data from bullheaded squeeze treatments in 7 different multiply fractured wells in 2 different Unconventional shale formations. Field data were compared with simulations using a model that couples inhibitor diffusion into and out of the rock matrix with adsorption either onto the rock matrix or the fracture proppant or both; it was found that in some field cases there is negligible difference between inclusion or exclusion of proppant adsorption, whereas in others much better simulation of inhibitor returns is observed if proppant adsorption is included. Other aspects have been included in the model, such as the influence of proppant embedment (changing the porosity of the fracture void) and treatment of only a fraction of the multiple fractures present in a well. Interestingly, inhibitor returns in the 3 wells in one field correlated best with simulations assuming only a low fraction (up to 30%) of fractures were treated by the squeeze, whereas simulations from 4 wells in another field correlated better with a much higher fraction of fractures (60 – 90%) being treated. This paper illustrates that an appropriate near-wellbore model can give good agreement with field data provided plausible physical phenomena are included, and that such a model can be used to design better squeeze treatments in Unconventional fractured-shale reservoirs without the need for complex full-field simulators.

Top of the line (TOL) corrosion presents a major challenge for many oil and gas operating companies, especially those producing or exporting gas. It is known to occur during multiphase flow, such as transport of wet gas, as a result of water vapour condensing on the upper, internal surfaces of the pipe which may not be protected by conventional corrosion inhibitors. The dissolution of corrosive gases present in the gas stream (mainly CO2 and/or H2S) into the condensed water can result in severe general or localised corrosion. The design and testing of inhibitors to protect against TOL corrosion is a key area of development, and as yet no industry standard test methodology is available for measuring TOL corrosion and assessing inhibitor performance under these conditions. In order to combat TOL corrosion, effective inhibitors are required to possess two somewhat contradictory properties: namely, to establish stable films on the steel surface while also possessing sufficient volatility to be transported to all locations where protection is required. Recently, we have developed a laboratory test method involving a relatively rapid screening stage followed by testing at more field-representative conditions, to determine TOL corrosion rates as well as to qualify the effectiveness of corrosion inhibitors designed to provide effective control against both TOL and bottom of the line (BOL) corrosion. The method, which includes techniques for ambient-pressure testing as well as alternative techniques for elevated pressures, has been shown to reliably determine the effectiveness of TOL corrosion inhibitor formulations. Both approaches have been validated by comparison with field cases. The application of this test methodology is already providing improved inhibitor selection for TOL corrosion, complementary to more standard test methods for inhibitor selection for BOL corrosion.

Background Ischemic episodes lead to profound functional and structural alterations of the gastrointestinal tract which may contribute to disorders of intestinal motility. Enhancement of glutamate overflow and the consequent activation of NMDA (N-methyl-d-aspartate) receptors may participate to such changes by modulating different enteric neurotransmitter systems, including cholinergic motor pathways. Methods The molecular mechanism/s underlying activation of NMDA receptors in the guinea pig ileum were investigated after glucose/oxygen deprivation (in vitro ischemia) and during reperfusion. Key Results The number of ileal myenteric neurons positive for NR1, the functional subunit of NMDA receptors, and its mRNA levels were unchanged after in vitro ischemia/reperfusion. In these conditions, the protein levels of NR1, and of its phosphorylated form by protein kinase C (PKC), significantly increased in myenteric neurons, whereas, the levels of NR1 phosphorylated by protein kinase A (PKA) did not change, with respect to control values. Spontaneous glutamate overflow increased during in vitro ischemia/reperfusion. In these conditions, the NMDA receptor antagonists, d(-)-2-amino-5-phosphonopentanoic acid [(d)-AP5] (10 μmol L−1) and 5,7-dichlorokynurenic acid (5,7-diClKyn acid) (10 μmol L−1) and the PKC antagonist, chelerythrine (1 μmol L−1), but not the PKA antagonist, H-89 (1 μmol L−1), were able to significantly depress the increased glutamate efflux. Conclusions & Inferences The present data suggest that in the guinea pig ileum during in vitro ischemia/reperfusion, NR1 protein levels increase. Such event may rely upon posttranscriptional events involving NR1 phosphorylation by PKC. Increased NR1 levels may, at least in part, explain the ability of NMDA receptors to modulate a positive feedback on ischemia/reperfusion-induced glutamate overflow.

This work reports on the synthesis of a SrTi1-x FexO3 nanostructured compound (0.0 B x B 0.1) using a modified polymeric precursor method. The effect of the addition of iron on the thermal, structural and morpho- logical properties of the nanoparticles was investigated by FT-IR spectroscopy, X-ray diffraction, and field emission scanning electron microscopy (FE-SEM). A thermogravi- metric analysis indicated that the crystallization process preceded by three decomposition steps. Differential ther- mal analysis experiments showed that decomposition occurred in a broad range of temperatures from 400 to 600 C. It was observed that iron ions acted as catalysts, promoting rapid organic decomposition and phase forma- tion at a lower temperature than in SrTiO3. Moreover, the addition of iron decreased the crystallite size and increased the lattice parameter of the SrTi1-xFexO3 structure.

Al2CoO4–PbCrO4 and Al2CoO4–Pb2CrO5 crystalline powders in different proportions were obtained by the polymeric precursor method. Differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques were used to accurately characterize the distinct thermal events occurring during synthesis. The TG and DSC results revealed a series of overlapping decomposition reactions due to different exothermal events, which were identified as H2O and NOx elimination and polymer pyrolysis. The X-ray diffraction patterns of the xAl2CoO4–(1 − x)PbCrO4 and xAl2CoO4–(1 − x)Pb2CrO5 mixed compounds, with x = 1, 0.75, 0.5, 0.25 and 0, were obtained in the crystalline form with their respective phases, and proved consistent with the nominal compositions. The synthesis of these two systems yielded nine different colors and shades.

Summary This paper describes field experience and lessons learned from bullhead-deployed scale-control operations in a deepwater subsea development in the Campos basin, Brazil; specifically, this paper is about deploying such treatments from the floating production, storage, and offloading (FPSO) host, along the production flow-lines, and into four low-water-cut, horizontal, subsea wells completed with sand control. The relatively small number of high-cost, highly productive wells, coupled with a very high barium sulfate (BaSO4) scaling tendency upon breakthrough of injection water, meant that not only was effective downhole scale management critical to achieve high hydrocarbon recovery, but that even wells at low water cuts were deemed to be at sufficient risk to require squeeze application. Initial bullheaded scale treatments comprised three "hybrid" treatments: a mutual-solvent preflush, a water-based main flush, and a diesel overflush. As water-production rates rose, so did the treatment volumes required. To improve the logistics of these treatments and to mitigate issues that arise from poor injectivity of diesel in these wells, core studies were conducted to investigate the option of changing the overflush fluid from marine diesel to injection-quality seawater. This change also introduced the possibility of forming a gas-hydrate plug during shut-in, but this was managed by use of a thermodynamic hydrate inhibitor and by replacing the flowline contents to flashed crude during the shut-in period. Both the operational aspects and the response of the wells to the modified treatments will be compared with those previously deployed in terms of, in particular, the injectivity of the wells during treatment and well-treatment cleanup rates and productivity afterward. The core studies also highlighted a formation-damage mechanism caused by incompatibility between the mutual solvent and the produced oil; this required modification of the treatment.

To develop a gradient pre-emphasis scheme that prospectively counteracts the effects of the first-order concomitant fields for any arbitrary gradient waveform played on asymmetric gradient systems, and to demonstrate the effectiveness of this approach using a real-time implementation on a compact gradient system.After reviewing the first-order concomitant fields that are present on asymmetric gradients, we developed a generalized gradient pre-emphasis model assuming arbitrary gradient waveforms to counteract their effects. A numerically straightforward, easily implemented approximate solution to this pre-emphasis problem was derived that was compatible with the current hardware infrastructure of conventional MRI scanners for eddy current compensation. The proposed method was implemented on the gradient driver subsystem, and its real-time use was tested using a series of phantom and in vivo data acquired from two-dimensional Cartesian phase-difference, echo-planar imaging, and spiral acquisitions.The phantom and in vivo results demonstrated that unless accounted for, first-order concomitant fields introduce considerable phase estimation error into the measured data and result in images with spatially dependent blurring/distortion. The resulting artifacts were effectively prevented using the proposed gradient pre-emphasis.We have developed an efficient and effective gradient pre-emphasis framework to counteract the effects of first-order concomitant fields of asymmetric gradient systems. Magn Reson Med 77:2250-2262, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Summary This paper describes field experience and lessons learned from scale control operations in a deepwater subsea development in the Campos Basin, Brazil; specifically, from bullheading scale-inhibitor squeezes from the FPSO host, along the production flowlines, into four low-watercut, horizontal subsea wells, completed with sand control. The relatively small number of high-cost, highly productive wells, coupled with a very high barium-sulfate scaling tendency upon breakthrough of injection water, meant that not only was effective scale management critical to achieve high hydrocarbon recovery, but even wells at low water cuts were deemed to be at sufficient risk to require squeeze application. Use of conventional, water based squeezes have been known to cause significant damage to productivity in low-watercut wells, including those showing a fines-migration tendency, as was the case here. Hence, on the basis of risk mitigation, supported by an extensive program of laboratory testing, it was decided that for the initial treatments, only the mainflush would be water based, with a mutual-solvent preflush and marine-diesel overflush. Other key challenges associated with treating from the host included the remote location of the wells, the potential to form hydrates, the cleanliness of the lines along which the treatment would pass, the achievement of effective placement over a long producing interval, as well as the need to deploy the chemical package via a support vessel adjacent to the FPSO. All had to be managed because of the high cost and low availability of a deepwater rig that could deploy the treatments directly to the subsea wellheads. This paper will explore in detail the issues associated with inhibitor-squeeze deployment in deepwater, subsea fields, many of which are currently being developed in the Campos basin, Gulf of Mexico, and West Africa, and are a good example of best-practice sharing from another oil basin.

The rupture of the kidney with the formation of an extracapsular hematoma in the renal cavity but no evidence of external trauma or other obvious renal cause, is an uncommon finding, most often requiring urgent surgery. An underlying renal pathology, often a renal tumor, should always be suspected. This article describes the case of a 57-year-old male patient who was admitted for severe left flank pain and presented with signs of peritonism, microscopic hematuria and low hemoglobin levels; an emergency left subcostal laparotomy was performed, with removal of the hematoma and enucleation of a partially open mid-renal mass; the kidney was spared. Histology showed a WHO type I, Fuhrman grade 2, papillary renal cell carcinoma. The article deals further with frequency, presentation, type and treatment of the pathology underlying the spontaneous rupture of the kidney, particularly with regard to renal carcinoma.

In this study, we measured the lymphocyte levels of proteins involved in apoptosis regulation, such as Bcl-2, the peripheral benzodiazepine receptor (PBR), caspase-3, and Cu/Zn superoxide dismutase (Cu/Zn SOD), in patients with Parkinson's disease (PD), either untreated or under therapy with dopaminergic agents (l-Dopa alone or l-dopa + dopamine agonists) and in healthy volunteers. All PD groups showed increased activity of caspase-3, compared to controls, particularly those under treatment only with l-Dopa. In this latter group, the increase in caspase-3 activity was also paralleled by an increase in the concentration of Cu/Zn SOD. In addition, patients taking l-Dopa + dopamine agonists showed marked decrease in Bcl-2 levels and increased PBR expression, which seems in keeping with the hypothesis that PBR may be functionally related to Bcl-2. In conclusion, we found clear modifications in the levels of proteins involved in the control of apoptosis in lymphocytes of PD patients. These changes were disease related but also modulated by the pharmacological treatment, which confirms the potential role of apoptosis in PD pathogenesis and the modulatory influence of dopaminergic agents.

Scale-dissolver technology has been developed and applied with varying degrees of success over the past few years to remove carbonate and the more challenging sulphate/sulphide scales from production tubing and process equipment. It can often seem a much safer, more cost-effective remediation approach than physical removal, in particular, in the new generation of HP/HT fields, where any physical well intervention carries high risk, while the high temperatures would normally be beneficial in enhancing scale solubility and dissolution rate. The current paper reports dissolution characterstics of three solvents for calcite, barite, celestite and anhydrite in the temperature range 85°C to 176° to verify their performance up to the very high temperatures of a specific HP/HT development. These solvents included a typical alkaline-pH chelant for sulphate scale, an organic-acid mixture for carbonate scales, and a novel neutral-pH chelant as a less corrosive solvent for carbonate scale removal. In some tests the liquid-to-solid ratiowasvaried to evaluate the impact of excess scale on solvent performance. The performance against BaSO4 of the alkaline-pH chelant unexpectedly declines very significantly at 176°C relative to that observed at 85°C. Thermal instability was ruled out as the cause becausethe solvent showed very limited decline in performance when tested at 85°C after it had been thermally aged at 176°C. Performance at 176°C showed an initial rise followed by a decreasein aqueous barium ions, strongly indicating secondary re-precipitation of a barium-containing species at this temperature. In contrast, dissolution rates of carbonate scale by organic acid were greaterat the higher temperature, as would be expected. The novel neutral chelant showed a decline in calcite dissolution performance during the 176°C test but unlike the alkaline-pH chelant used for sulphate scale, this chelant showed degradation after thermal ageing and re-testing at 85°C. The findings from this paper suggest that there is temperature limit above which effective removal of sulphate scales may not be feasible with the selected solvents due to re-precipitation of a secondary reaction product, while for carbonate removal the current neutral chelants tested have a thermal stability issue at 176°C. These findings need to be considered when evaluating the potential role of chemical remediation in the overall scale-control strategy for HP/HT fields.

Wear of polyethylene acetabular components of hip implants is a significant clinical problem. In prosthetic hip surgery, polyethylene wear is identified as a factor that limits the life of the implant; it is known that the production of debris can cause adverse tissue reactions that may lead to extensive bone loss around the implant, and consequently loosening of the fixation. A new class of so-called Diamond-Like Carbon coatings, applied to titanium femoral heads was compared to ceramic and metallic heads in terms of wear behavior against UHMWPE using a hip joint simulator with a bovine calf serum lubricant. A thin film of Diamond-Like Carbon was deposited directly onto titanium (Ti6Al4V) head using chemical vapor deposition. The wear of polyethylene coupled with Diamond-Like Carbon coated femoral heads was comparable to that obtained with the polyethylene coupled with commer- cial alumina femoral heads. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 53: 221-226, 2000

The aims of this study were to assess the possible role of peripheral benzodiazepine receptors (pBZrs)1 in mediating the in vitro effects of carbamazepine (CBZ) on some neutrophil functions in healthy volunteers and to investigate neutrophil function and pBZr expression in patients with epilepsia on CBZ monotherapy for at least 1 year. In vitro CBZ (42-168 microM) concentration-dependently inhibited chemotaxis induced by N-formyl-methionyl-leucyl-phenylalanine (FMLP) or lipopolysaccharide (LPS)-activated human serum. CBZ did not affect random migration, phagocytosis index, phagocytosis frequency, NBT reduction frequency, C. albicans lethality index and resting superoxide production. The pBZr antagonist PK 11195 (1 microM, per se ineffective) reversed the inhibitory effect of CBZ on chemotaxis induced by endotoxin-activated serum or FMLP. The pBZr agonist Ro 5-4864 (10-100 microM) mimicked the effect of CBZ on chemotaxis induced by endotoxin-activated serum or FMLP and had no effect on the other parameters. Neutrophils from epileptic patients on chronic CBZ monotherapy had impaired FMLP- and serum-induced chemotaxis and enhanced expression of pBZrs on neutrophils. These data strongly suggest an involvement of pBZrs in mediating the in vitro effects of CBZ on chemotaxis; furthermore, impairment of the same neutrophil function parameters and overexpression of pBZrs in patients are consistent with the hypothesis of an in vivo interaction of CBZ with pBZrs.

The Authors present a comparison between the first 13 radical perineal prostatectomies performed in their Center and 14 retropubic radical prostatectomies, in order to describe the experience of a group adopting a new technique besides an already acquired one. The age of the patients ranged from 56 to 74 years (mean 67), the mean follow-up was 12 months. Both technique provided a disease-specific survival of 100% and absence of technique-related complicances. The perineal technique implies, at the beginning, worse –- although acceptable –- results as regards continence and erectile function and better results as regards duration of the hospital stay of the patient.