bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling and Simulation of Nitrate Injection for Reservoir Souring Remediation
Authors: Haghshenas Mehdi , Sepehrnoori Kamy , Bryant Steven L. , Farhadinia Mohammad Ali
Published: November 2012

Reservoir souring refers to the onset of hydrogen sulfide (H2S) production during waterflooding. Besides health and safety issues, H2S content reduces the value of the produced hydrocarbon. Nitrate injection is an effective method to prevent the formation of H2S. Designing this process requires the modeling of a complicated set of biogeochemical reactions involved in the production of H2S and its inhibition. This paper describes the modeling and simulation of biological reactions associated with the injection of nitrate to inhibit reservoir souring. The model is implemented in a general-purpose adaptive reservoir simulator (GPAS). To the best of our knowledge, GPAS is the first field-scale reservoir simulator that models reservoir souring treatment.

The basic mechanism in the biologically mediated generation of H2S is the reaction between sulfate in the injection water and fatty acids in the formation water in the presence of sulfate-reducing bacteria (SRB). There are proposed mechanisms that describe the effect of nitrate injection on souring remediation. Depending on the circumstances, more than one mechanism may occur at the same time. These mechanisms include the inhibitory effect of nitrite on sulfate reduction, the competition between SRB and nitrate-reducing bacteria (NRB), and the stimulation of nitrate-reducing sulfide-oxidizing bacteria (NR-SOB). For each mechanism, we specify the biological species and chemical components involved and determine the role of each component in the biological reaction. For every biological reaction, a set of ordinary differential equations along with differential equations for the transport of chemical and biological species are solved.

The results of reported experiments in the literature are used to find the input parameters for field-scale simulations. This reservoir simulator can then predict the onset of reservoir souring and the effectiveness of nitrate injection and helps in the design of the process. The comprehensive modeling accounts for variation in biological system characteristics and reservoir conditions that affect the production and remediation of H2S.
A New Method To Model Relative Permeability in Compositional Simulators To Avoid Discontinuous Changes Caused by Phase-Identification Problems
Authors: Yuan Chengwu , Pope Gary A.
Published: November 2012

Simple methods, such as the use of density during compositional simulations, often fail to identify the phases correctly, and this can cause discontinuities in the computed relative permeability values. The results are then physically incorrect. Furthermore, numerical simulators often slow down or even stop because of discontinuities. There are many important applications in which the phase behavior can be single phase, gas/liquid, liquid/liquid, gas/ liquid/liquid, or gas/liquid/solid at different times in different gridblocks. Assigning physically correct phase identities during a compositional simulation turns out to be a difficult problem that has resisted a general solution for decades. We know that the intensive thermodynamic properties, such as molar Gibbs free energy, must be continuous, assuming local equilibrium, but this condition is difficult to impose in numerical simulators because of the discrete nature of the calculations. An alternative approach is to develop a relative permeability model that is continuous and independent of the phase numbers assigned by the flash calculation. Relative permeability is a function of saturation, but also composition, because composition affects the phase distribution in the pores (i.e., the wettability). The equilibrium distribution of fluids in pores corresponds to the minimum in the Gibbs free energy for the entire fluid/rock system, including interfaces. In general, however, this relationship is difficult to model from first principles. What we can easily do is calculate the molar Gibbs free energy (G) of each phase at reference compositions where the relative permeabilities are known or assumed to be known and then interpolate between these values by use of the G calculated during each timestep of the simulation. Relative permeability values calculated this way are unconditionally continuous for all possible phase-behavior changes, including even critical points. We tested the new relative permeability model on a variety of extremely difficult simulation problems with up to four phases, and it has not failed yet. We illustrate several of these applications.
Improving Real-Time Image-Data Quality With A Telemetry Model
Authors: Hartmann Andreas , Akimov Oleg , Fulda Christian , Morris Stephen
Published: November 2012

The introduction of new measurements constantly increases the amount of real-time data from logging-while-drilling (LWD) services, providing better information for informed decision making. This is matched by telemetry technologies that provide data rates from bits per second to megabits per second. During a deployment, the bandwidth is shared between several services requiring different data rates, leaving the user with the task of aligning telemetry technology and shared data rates to the application. High-volume services often allow for data compression. Lossless or near-lossless compression provides the best data quality but requires large bandwidth. Lossy compression reduces bandwidth usage dramatically, but may result in degraded data quality. Thus, telemetry planning must be tied closely to service objectives and requires expert advice.

We present a planning approach in which we model the realtime-data compression of an LWD high-resolution imaging tool that uses a flexible compression algorithm. This system allows lossy compression for telemetry rates as low as 1 bps, while at the same time delivering memory-data quality using high-speed-telemetry technology. The compression rate determines the image resolution and must be adjusted to the detail required in the transmitted image. Using offset-well data or simulated memory data, the expected real-time image is simulated and its level of detail quantified. For instance, the presence and appearance of fractures in real time can be forecasted. This enables us to optimize telemetry usage and define compression and drilling parameters for a successful deployment of the imaging service.

This paper will outline the methods and benchmark the technology of the imaging tool, using real-time data measured during field deployments. We will then use parameter variations to show how increasing net bandwidth improves the amount of detail in the images, and how these are used for different levels of realtime-data interpretation.
In-Situ Mechanical- and Functional-Behavior Characterization of a Shape-Memory Polymer for Sand-Control Applications
Authors: Yuan Yusheng , Goodson Jim , Johnson Mike , Gerrard David
Published: November 2012

Pumping a gravel slurry between a downhole screen and the rock matrix has been used to prevent production of undesirable solids or sand from the formation in traditional oil and gas completions. Recently developed expandable technology attempts to eliminate this operation by expanding metallic sand-control screens against the wellbore. However, one problem with this process is borehole irregularity. It is desirable to have a smart downhole-screen structure that is capable of self-expanding and conforming to the borehole surfaces in certain downhole conditions. Use of an advanced shape-memory-polymer (SMP) structure offers breakthrough performance for sand-control applications. Proper characterization and full understanding of the thermal, mechanical and functional behavior of the SMP structure in simulated downhole pressure, temperature, and fluid conditions are critical for successful applications.

This study used a high-pressure/high-temperature (HP/HT) in-situ mechanical test system and test method to characterize the in-situ hot-wet mechanical and functional behavior of the SMP foam, including deployment and contact-pressure-development functional properties, compressive resistance, and time-dependent stress-relaxation and creep mechanical properties. These properties were determined during immersion in a fluid environment at various temperatures under ambient pressure and 3,000- to 5,000-psi hydrostatic pressure. Effects of the test temperature, fluid condition, and the hydrostatic pressure on mechanical and functional properties of the SMP foam were identified. Study results were used to establish the operational window of the SMP screen as a sand-control solution.
Alkaline Steam Foam: Concepts and Experimental Results
Authors: Lau H.C.. C.
Published: November 2012

Experimental studies have shown that the steam-foam process can be enhanced significantly by injecting a suitably formulated alkali/surfactant mixture in the aqueous phase of steam. Emulsionscreening tests, corefloods, and flow-visualization experiments using an alpha olefin sulfonate (AOS) surfactant with 16–18 carbon, Na2CO3, and a heavy Californian crude have shown that alkaline steam foam offers significant advantages over regular steam foam by combining the benefits of thermal and chemical enhanced-oil-recovery (EOR) processes.

First, Na2CO3 reduces surfactant consumption by adsorption by rendering the clay surface more negatively charged. Second, by precipitating divalent ions that get ion exchanged off the clays, Na2CO3 reduces surfactant consumption by precipitation. Third, a suitably formulated alkali/surfactant system reduces the oil/water interfacial tension (IFT) sufficiently to enable the heavy oil to be emulsified into the aqueous phase in the presence of steam. This oil-in-water emulsion is less viscous than the oil alone and can be readily transported. Consequently, the residual-oil saturation (ROS) is reduced to a value less than that of steam. Fourth, this lower ROS reduces the destabilizing effect of oil on foam, resulting in stronger steam foam that provides better mobility control than regular steam foam. Therefore, it has the potential to further reduce steam gravity override. Fifth, the reduction in gravity override also reduces loss of heat to the cap rock, thereby improving steam utilization.

When applied to steamdrive, alkaline steam foam has the benefit of increasing foam-propagation rate, improving mobility control, improving steam use, and reducing the ROS. Potential applications of alkaline steam foam to steam soaks and steam-assisted gravity drainage (SAGD) are also discussed.
Estimating Drainage-Area Pressure With Flow-After-Flow Testing
Authors: Kabir C.S.. S. , Elgmati M.. , Reza Z..
Published: November 2012

Estimating the average drainage-area pressure (pav) of individual wells is a cornerstone to any reservoir-management practice. Yet conventional methods do not always offer reliable solutions to this vexing problem. This study shows that transient flow-after-flow (FAF) testing offers an excellent opportunity to establish pav in a time-lapse mode, when conducted following operational shutdowns. Instrumented wells are natural candidates for FAF testing.

Real-time surveillance offers the opportunity to perform rate-transient analysis that results in drainage volume and, consequently, pav. However, gathering quality rate data commensurate with pressure over a long producing period is fraught with uncertainty, which raises questions about the validity of the pav so obtained. In addition, continuous changes in drainage-boundary conditions pose modeling challenges with a given reservoir model. Therefore, the independent estimation of pav cannot be overemphasized. This paper presents a theroretical framework for transient FAF testing and also shows a pragmatic approach to handling pressure/rate data incoherence.
Removal of Cyclic Borehole Noise From Low- and High-Resolution LWD Images and Its Impact on Image Interpretation
Authors: Sugiura J.. , Lee R..
Published: November 2012

The use of logging-while-drilling (LWD) imaging tools in realtime decision making and post-drilling analysis has become commonplace. However, image noise and processing errors because of inherent measurement physics can propagate errors and, thus, complicate interpretation of openhole log data and images. For example, standard density images tend to amplify image noise from small borehole irregularities. Among different borehole irregularities, spiraling is known to occur more frequently with conventional rotary assemblies, steerable motor assemblies, and rotary-steerable assemblies. When the cyclic-noise amplitude from spiraling becomes large relative to the measurement of the primary interest, it grossly affects the quality of the recorded formation bulk density, photoelectric factor, and neutron porosity.

This paper shows novel methods to remove cyclic noise from formation-evaluation (FE) images by applying frequency-domain filtering. Although the initial attempt of fast Fourier transforms (Zhang et al. 2010) illustrates the straightforward concept, it is seldom used because of implementation issues requiring interactive filter design and intensive operator intervention. Recently, a new method (Sugiura et al. 2011) has been designed to improve the filtering process. Additionally, the new adaptive filter designs automate the cyclic-noise-removal process from the FE images. Standalone software has been developed to process the entire image logs from one well, without human supervision. The software adaptively modifies the filter behavior as borehole-oscillation noise characteristics change with formation, drilling assemblies, hole inclination, and depth.

To examine its validity qualitatively, the algorithm is then applied to various field data, not only on low-resolution density images but also on higher-resolution density images. The new algorithm has been proved by bringing considerable improvement to the image quality without any artificial interruptions. The rugosity effect is reduced significantly, and the apparent resolution of bed-boundary features is increased.

Furthermore, comparative field examples illustrate the improvement in image-feature extraction. The method described here is critical, for example, for small-fracture detection and more-precise definition of formation-property contrasts indicative of bed boundaries in irregular boreholes. This new method not only is effectively used for density images but also is applicable to any other borehole images, such as resistivity and ultrasonic images.
Gas Permeability of Shale
Authors: Sakhaee-Pour A.. , Bryant Steven L.
Published: November 2012

Permeability is one of the most fundamental properties of any reservoir rock required for modeling hydrocarbon production. However, shale permeability has not yet been understood fully because of the complexities involved in modeling flow through nanoscale throats. In this paper, we analyze the effects of adsorbed layers of methane (CH4) and of gas slippage at pore walls on the flow behavior in individual conduits of simple geometry and in networks of such conduits. The network is based on scanning elecron microscope (SEM) images and a drainage experiment in shale. To represent the effect of adsorbed gas, the effective size of each throat in the network depends on the pressure. The hydraulic conductance of each throat is determined on the basis of the Knudsen number (Kn) criterion (Knudsen 1909). The combined effects of adsorption and slip depend strongly on pressure and on conduit diameter. The results indicate that laboratory measurements made with N2 at ambient temperature and 5-MPa pressure, which is typical for a transient pulse-decay (TPD) method, overestimate the gas permeability at early life of production by a factor of four. This ratio increases if the measurement is run at ambient condition because the low pressure enhances the slippage and reduces the thickness of the adsorbed layer. Moreover, the permeability increases nonlinearly as the in-situ pressure decreases during production. This effect contributes to mitigating the decline in the production rate of shale-gas wells. Laboratory data available in the literature for CH4 permeability at pressures below 7 MPa agree with model predictions of the effect of pressure.
New and Improved Methods for Performing Rate-Transient Analysis of Shale Gas Reservoirs
Authors: Nobakht Morteza , Clarkson C.R.. R. , Kaviani D..
Published: November 2012

Multifractured horizontal wells are currently the most popular method for exploiting low-permeability tight and shale gas reservoirs. Production data analysis is the most widely used tool for analyzing these reservoirs for the purpose of reserves estimation, hydraulic fracture stimulation optimization, and development planning (Ambrose et al. 2011). However, as pointed out by Clarkson et al. (2012), a fundamental problem with the application of conventional production data analysis to ultralow permeability reservoirs is that current methods were derived with the assumption that flow can be described with Darcy's law. This assumption may not be valid for tight/shale gas reservoirs, as they contain a wide distribution of pore sizes, including in some cases nanopores (Loucks et al. 2009). Therefore, the mean-free path of gas molecules may be comparable to or larger than the average effective rock pore throat radius, causing the gas molecules to slip along pore surfaces. This results in slippage non-Darcy flow, which is not accounted for in conventional production data analysis.

Clarkson et al. (2012) modified the pseudovariables used for analyzing gas reservoirs in production data analysis to account for slippage. They demonstrated that if the effect of slippage is not considered, it leads to noticeable errors in reservoir characterization. Clarkson et al. (2012) also mentioned that even after using the modified pseudovariables, the values for permeability and fracture half-length do not exactly match the input data to simulation. In this paper, a methodology to properly analyze the production data from a fractured well in a tight/shale gas reservoir producing under a constant flowing pressure in the presence of desorption and slippage is presented. This method uses a new pseudotime definition instead of the conventional pseudotime currently being used in production data analysis. The method is validated using a number of numerically simulated cases. It is found that the newly developed analytical method results in a more reliable estimate of fracture half-length or contacted matrix surface area, if permeability is known.
An Innovative Approach for Pore Pressure Prediction and Drilling Optimization in an Abnormally Subpressured Basin
Authors: Contreras Oscar , Hareland Geir , Aguilera Roberto
Published: November 2012

Thus far, an indirect generalized method to predict pore pressure under subpressured conditions has not been reported in the literature. In this work, an innovative procedure is presented for estimation of pore pressure and optimization of wells drilled in the abnormally subpressured Deep Basin of the Western Canada Sedimentary Basin (WCSB). The procedure starts with detailed evaluation of five wells drilled in a township that covers the study area. Pore pressure was calculated from sonic logs and the modified D exponent by the use of Eaton's method (Eaton 1975), which proved to be the most effective approach for abnormally subpressured conditions over a variety of methods tested (Contreras et al. 2011). The optimization procedure was carried out by use of the apparent-rock-strength log (ARSL), which is an effective indicator of formation drillability and is very sensitive to the pore pressure. Next, optimization of individual sections in each well was carried out to determine the optimum types of bits and operational parameters for the lowest cost of drilling.

An artificial-intelligence function was implemented to set up the optimum combination of parameters in such a way that the rate of penetration (ROP) (m/h) was increased after a number of simulation runs while controlling the bit wear. Special attention was focused on tight gas reservoirs for selection of the most suitable parameters that increase the quality of drill cuttings. It was concluded that the roller-cone bit IADC 547 (with at least 0.73 hp in the bit per square inch) provides the best-quality cuttings for the Nikanassin Group. This is of paramount importance for increasing accuracy in the quantitative determination of permeability and porosity from cuttings particularly in those tight gas reservoirs where the amount of cores is very limited.

It is concluded that wells in the Deep Basin of the WCSB can be drilled efficiently with seven bit runs while maintaining the cuttings quality, bit-wear level, and well stability at a significantly high average ROP of 13 m/h. Another conclusion is that the normal trend methods from sonic logs are the most effective approach when dealing with an abnormally subpressured basin.
Finite Horizontal Well Crossing a Natural Fracture Normally
Authors: Prats Michael , Raghavan R..
Published: November 2012

An analytic solution in terms of the Laplace transformation is presented to calculate the pressure distribution in multizone, composite reservoirs intercepted by a finite horizontal well that is oriented normal to the plane interfaces in an infinite field. A three-zone reservoir is analyzed for illustrative purposes, with the horizontal well traversing a thin high-permeability central zone confined between two parallel planes representing the natural fracture, and with the well completed in the adjacent zones. The method provides the transient pressure field for each of the three zones, allowing analyses of the flow fields both within the fracture and within the reservoir as a function of pertinent parameters. The computational scheme considered is both viable and robust. To our knowledge, this topic is yet to be analyzed in this fashion analytically.

The numerical results presented are limited to a parametric study of (1) transient well pressures and their time derivative and (2) steady-state flux and flow-rate distributions at the fracture faces as a function of distance from the well. A steady-state correlation of the productivity index is also provided.

We discovered that of the two generally accepted procedures for estimating the average well pressure, the one based on well rates proportional to the local permeability and well length gives results consistent with our model, whereas the one requiring equal average pressure at each well segment introduces significant disturbances to the flow field near the fracture-well intercepts, at least when small and large well lengths are present, as is the case in the problem under consideration. This subject needs additional investigation.
3D Inversion-Based Interpretation of Marine CSEM Data
Authors: Zach J.J.. J. , Frenkel M.A.. A.
Published: November 2012

The marine controlled-source electromagnetic (CSEM) method has been evolving into a geophysical imaging tool for increasingly complex geological settings in which multiple resistive bodies can be resolved. An advanced subsurface imaging workflow for 3D CSEM surveys is presented, which reproduces the resistivity distribution to within a spatial resolution determined by the frequencies included. The performance of our advanced-processing workflow is demonstrated using a case study from the Gulf of Mexico (GOM), where a dense 3D grid was acquired over an area of high-quality seismic data and well log control.

At the core of our 3D workflow is an inversion methodology with approximate Hessian-based optimization and a fast finite-difference time-domain forward operator. The optimization matches the synthetic to the measured field within 100–200 iterations and is sufficiently robust in three dimensions to avoid expensive regularization schemes. The sensitivity of the gradient-based inversion to the starting model is addressed by investing considerable effort in building 1D inversion-based starting models. At the same time, 3D inversion algorithms for survey layouts, including azimuthal data, demand high-quality data conditioning for which we present a processing sequence from time-domain electromagnetic data acquired by seabed receivers to frequency-domain data and weights for inversion.

Detection and delineation of reservoirs in the presence of salt is recognized as a major challenge to CSEM methods. In order to interpret 3D data accurately in such a complex environment, the true-resistivity cube is built from a sequence of constrained inversion-based interpretation steps. Using a data set acquired in 2008 in the GOM, we demonstrate the ability of our 3D technology to resolve small (2×2 km), low-resistivity pay (Δρ:5Ω·m) targets within the vicinity (< 1 km) of large salt bodies. In this case study, the 3D method converged within 1 week, running on 150 parallel nodes.
A Basis for Automated Control of Steam Trap Subcool in SAGD
Authors: Gotawala Dharmeshkumar R. , Gates Ian D.
Published: November 2012

Full steam conformance along the well pair of the steam-assisted gravity-drainage (SAGD) oil-sands-recovery process is essential for high thermal efficiency. Conformance can be improved by controlling injection and production strategies to ensure that steam is delivered to target regions in the reservoir. Smart wells use interval-control valves (ICVs) that, conceptually, can be dynamically controlled to yield uniform steam injectivity along the well pair. Dynamic control algorithms, such as proportional-integral-derivative (PID) control and their associated controller parameters, have not yet been developed for the SAGD processes that use ICVs. One control strategy would be to control the interwell subcool temperature difference—that is, the difference between the steam-injection temperature and the produced-fluids temperature. If this temperature difference is small, then the liquid pool above the production well is small and there is a likelihood of live steam production from the chamber. On the other hand, if the difference is large, the pool may rise above the injection well and gravity drainage is hindered because the chamber is largely filled with liquid. Here, the focus is on developing a simple, approximate theory for the behavior of the liquid pool at the base of the steam chamber to determine the ranges of values of control parameters to achieve a targeted interwell subcool temperature difference.
Altering an Existing Well Design To Meet New BOEMRE Worst-Case Discharge Criteria
Authors: Bowman Steven
Published: November 2012

The Moccasin exploration well in the deepwater Gulf of Mexico (GOM) was suspended before reaching planned total depth (TD) because of the GOM drilling moratorium imposed after the Macondo blowout. The well design had to be significantly altered to meet the new worst-case discharge criteria required by the Bureau of Ocean Energy Management, Regulation, and Enforcement (BOEMRE) and to resume drilling while preserving a planned 10⅝-in. hole size at TD for formation-evaluation purposes. To meet the worst-case discharge collapse criteria, the well must survive an uncontrolled blowout at the mudline (seawater gradient to the wellhead with a flowing-oil gradient from the wellhead to TD). Furthermore, the well must survive shutting in the blowout, leaving the well fully evacuated to oil from the wellhead to the flowing zone (maximum anticipated wellhead pressure with an oil gradient to TD below).

The Moccasin well's 13⅝-in. liner had to be tied back to the wellhead to provide sufficient burst resistance for the case of full evacuation to oil. An exceptionally long 11⅞-in. liner and a short 11⅞-in. scab liner inside 13⅝-in. casing were required to mitigate deep collapse risk of the 13⅝-in. liner associated with a flowing, unrestricted blowout at the mudline.
Air-Foam-Injection Process: An Improved-Oil-Recovery Technique for Waterflooded Light-Oil Reservoirs
Authors: Dong X.. , Liu H.. , Sun P.. , Zheng J.. , Sun R..
Published: November 2012

With the intent of solving problems that emerge at the later stage of waterflooded reservoirs, we study the feasibility of air-foam flooding of waterflooded light-oil reservoirs using the method of physical simulation. Through isothermal combustion experiments, the influence of clay mineral and foam on low-temperature-oxidation (LTO) reactions is investigated qualitatively. Then, the quantitative investigation of water saturation on oxidation rate and O2 consumption rate is discussed. After that, some dynamic foam displacement experiments are also performed, including the singletube displacement experiments of air foam at different water saturations and enhanced-oil-recovery (EOR) experiments of air-foam flooding in parallel tubes. In addition, in order to verify the O2 consumption capacity of the sample oil, a slimtube experiment is conducted. The results show that the presence of clay minerals could speed the process of the LTO reaction, while the presence of foam will slow this process. The LTO reaction is not significantly associated with oil viscosity. The concentration of O2 was near zero when the gas breakthrough occurred. Once the oxidation region reached the outlet, the concentration of O2 suddenly increased, and the effect of O2 consumption became worse. G64-38 crude oil performs better in the process of O2 consumption. The injection of air foam could effectively plug the high-permeability tube and restart the low-permeability tube. This paper could be used as a tool for the successful design of air-foam flooding at a later waterflood stage to enhance crude-oil recovery in light-oil reservoirs.
Comparative effectiveness of biologic antirheumatic therapies in rheumatoid arthritis after failure to respond to a first TNF inhibitor
Authors: Finckh Axel
Published: November 2012

Evaluation of: Gomez-Reino JJ, Maneiro JR, Ruiz J
et al.
Comparative effectiveness of switching to alternative tumour necrosis factor (TNF) antagonists versus switching to rituximab in patients with rheumatoid arthritis who failed previous TNF antagonists: the MIRAR Study.
Ann. Rheum. Dis.
doi:10.1136/annrheumdis-2012-201324 (2012) (Epub ahead of print)

. Rheumatoid arthritis is a chronic immune-mediated disease affecting approximately 1% of the population. The prognosis of this chronic condition has considerably improved over the past decade with the earlier use of antirheumatic drugs and the introduction of new biologic therapies. Current treatment guidelines recommend using these agents after a failed response to conventional disease-modifying antirheumatic drugs, but the relative positioning of the various available biologic agents is not yet well established. All biologic agents have been proven to be superior to placebo in large trials, but only very few randomized controlled trials have compared directly competing therapeutic options. This article evaluates the effectiveness of rituximab compared with an alternative TNF antagonist (anti-TNF) in rheumatoid arthritis patients who experienced a previous failed response to anti-TNF. The results of this large observational cohort study suggest that rituximab offers a greater benefit on rheumatoid arthritis disease activity than alternative monoclonal anti-TNFs.
Maximizing health through the rapidly developing fields of comparative and cost–effectiveness
Authors: Annemans Lieven
Published: November 2012

Lieven Annemans
is a Full Professor of Health Economics at Ghent University and Brussels University (Belgium) and cofounder of the Interuniversity Centre for Health Economics Research. He is Past-President of the International Society for PharmacoEconomics and Outcomes Research, a member of the Flemish Council for Health and Wellbeing (advising the Minister of Health), and an external expert to the Belgian Health Care Knowledge Centre, the Belgian health technology assessment body. He has 20 years experience in health-economic evaluations of pharmaceutical drugs, vaccines, medical devices, diagnostics and preventive health actions in various medical areas. He is author of the book ‘Health economics for noneconomists: an introduction to the concepts, methods and pitfalls of health economic evaluations’ and of the recent report ‘Towards valuable innovation in the EU’ (a background report to the EU council of ministers of health). His main research interests are epidemiological models, health technology assessment, retrospective/prospective health-economic evaluations and physician payment systems. He has published approximately 150 papers in peer-reviewed journals, presented approximately 300 posters/papers at scientific conferences, and has given approximately 500 lectures and trainings on health economics and health technology assessment.
Possible ways to enhance renin–angiotensin prescribing efficiency: Republic of Serbia as a case history?
Authors: Kalaba Marija , Godman Brian , Vuksanović Aleksandar , Bennie Marion , Malmström Richard E
Published: November 2012

Background:
Multiple reforms have been instigated across Europe to enhance prescribing efficiency. Supply-side reforms in the Republic of Serbia include measures to lower the price of generics and originators, with demand-side measures including patient copayments and prescribing restrictions. Specific measures for renin–angiotensin inhibitor drugs include a 50% copayment for angiotensin receptor blockers (ARBs) versus approximately 50 cents per prescription for established angiotensin-converting enzyme inhibitors (ACEIs), as there is no perceived difference in effectiveness between the two classes.
Objectives:
To assess the influence of these measures on ARB utilization, as well as reimbursed prices of ACEIs and ARBs over time.
Method:
Observational retrospective case study of all ambulatory care patients in the Republic of Serbia’s Health Insurance Fund database who were dispensed at least one ACEI or ARB alone or in combination (fixed dose combination [FDC]) between 2005 and 2011. Utilization measured in defined daily doses (DDDs) and only reimbursed expenditure (overall and expenditure/DDD) as Health Insurance perspective.
Results:
There was a 1.8-fold increase in renin–angiotensin inhibitor drug utilization, rising to 207.4 DDDs/1000 inhabitants per day in 2011. This is driven principally by a 19.6-fold increase in ACEI FDCs. There was only limited utilization of ARBs at just 2% of total renin-angiotensin inhibitor drugs in 2011. Reimbursed expenditure increased 2.54-fold due to an appreciable increase in ACEI FDC utilization at approximately twice the cost of ACEIs in recent years. Alongside this, we noted considerable differences in expenditure/DDD for different ACEIs.
Conclusion & future perspective:
High patient copayments for ARBs appreciably limited their utilization in Serbia, which mirrors the findings from other studies. Potential future measures to enhance prescribing efficiency include reference pricing for ACEIs based on the lowest price of an established ACEI. In addition, reference pricing for FDCs should be based on the reference price of the individual components combined. This builds on recent reforms restricting the reimbursement of FDCs until 3 months after individual components have been prescribed separately.
SEM/EDX and XRD characterization of silver nanocrystalline thin film prepared from organometallic solution precursor
Authors: Dimitrijevic R. , Cvetkovic O. , Miodragovic Z. , Simic M. , Manojlovic D. , Jovic V.
Published: November 2012

The Ag nano-structured thin films prepared on flat glass substrates have been
studied. The ball-like silver nanoparticles have been synthesized in large
quantity by using a modified method of hydrolytic decomposition of silver
complexes with amino types ligands formed in ethanol aqueous solution. SEM
analysis revealed that Ag nanoparticles are all sphere shaped with bimodal
size (40 and 70 nm) distribution. The results of XRD powder pattern
examination show that Ag nanoparticles are pure phase, well crystallized. The
unit cell dimensions measured on synthesized Ag nano films show small but
frequent contraction in comparison to Ag metal standard.
Satisfaction with orthodontic treatment
Authors: Keles Filiz , Bos Annemieke
Published: November 2012

Objectives:

To examine the satisfaction of patients with their orthodontic treatment at the Department of Orthodontics at the Academic Centre for Dentistry Amsterdam (ACTA) in The Netherlands.

Materials and Methods:

To analyze differences in satisfaction through time, the results of patients treated at ACTA in 2008 and 2009 were compared with the results of patients treated at ACTA in 2000. A validated questionnaire about patient satisfaction was used. The total scale was divided into six subscales. A questionnaire was sent to all patients younger than 30 years who finished orthodontic treatment in 2008 and 2009 at ACTA.

Results:

The internal consistency of the total scale and the six subscales of the questionnaire was satisfactory. Respondents scored highest on items about satisfaction with the doctor-patient relationship (mean 4.24; SD 0.63) and lowest on items regarding their satisfaction with psychosocial improvement (mean 2.88; SD 0.87). Compared to the results of the sample from 2000, significant differences were found on the subscales doctor-patient relationship, residual category, and psychosocial improvement as well as on the total sum scale.

Conclusions:

The doctor-patient relationship remains the most important factor contributing to patient satisfaction. However, the results show that, overall, patients are more satisfied with their orthodontic treatment than patients were a decade ago.
Accuracy of three-dimensional and two-dimensional ultrasonography for measurement of tumor volume in dogs with transitional cell carcinoma of the urinary bladder
Authors: Naughton James F. , Widmer William R. , Constable Peter D. , Knapp Deborah W.
Published: November 2012

Objective—To determine the accuracy of 3-D and 2-D ultrasonography for quantification of tumor volume in dogs with transitional cell carcinoma (TCC) of the urinary bladder.

Animals—10 dogs with biopsy-confirmed TCC.

Procedures—The urinary bladder of each dog was distended with saline (0.9% NaCl) solution (5.0 mL/kg), and masses were measured via 3-D and 2-D ultrasonography. Masses were also measured via 3-D ultrasonography after bladders were distended with 2.5 and 1.0 mL of saline solution/kg. Subsequently, the bladder was deflated and distended with CO2 (5.0 mL/kg); CT was performed after IV contrast medium administration. Tumor volumes were calculated via 3-D ultrasonography, 2-D ultrasonography, and CT (reference method) and compared via ANOVA, Deming regression, and Bland-Altman plots. Repeated-measures ANOVA was used to assess effects of bladder distension on 3-D tumor volume measurements. Repeatability of measurements was estimated via the coefficient of variation for each method.

Results—Repeatability was considered good for all 3 methods. There was no significant difference in tumor volume measurements obtained via 3-D ultrasonography at different degrees of urinary bladder distension. Results of Deming regression and Bland-Altman plots indicated excellent agreement between tumor volume measurement with 3-D ultrasonography and CT, but not between 2-D ultrasonography and CT.

Conclusions and Clinical Relevance—Tumor volume in dogs with TCC of the urinary bladder was accurately measured via 3-D ultrasonography. Use of 3-D ultrasonography can provide a less expensive and more practical method for monitoring response to treatment than CT and was more accurate than 2-D ultrasonography.
Prevalence and antimicrobial susceptibility of virulent and avirulent multidrug-resistant Escherichia coli isolated from diarrheic neonatal calves
Authors: Barigye Robert , Gautam Ablesh , Piche Lisa M. , Schaan Lynn P. , Krogh Darlene F. , Olet Susan
Published: November 2012

Objective—To determine the prevalence of selected virulence genes and the antimicrobial susceptibility of multidrug-resistant (MDR) Escherichia coli isolated from diarrheic neonatal calves.

Sample—97 E coli isolates from diarrheic neonatal calves.

Procedures—E coli isolates were tested via PCR assay for 6 virulence genes and susceptibility to 17 drugs belonging to 9 classes. A 2-sample test of proportions was used to make comparisons between proportions of virulent and avirulent MDR isolates.

Results—23 of 97 (23.7%) isolates were virulent, and 74 (76.3%) were avirulent. Of the 23 virulent isolates, 15 (65.2%) were positive for K99, 14 (60.9%) for F41, 12 (52.2%) for STa, 9 (39.1%) for Stx1, 6 (26.1%) for intimin, and 0 (0%) for Stx2. Twenty of 23 (87.0%) virulent isolates expressed ≥ 2 virulence genes, and 3 of 23 (13.0%) were positive for 1 virulence factor. Eight of 23 (34.8%) virulent isolates expressed STa, K99, and F41, whereas 1 of 23 (4.4%) was positive for STa, F41, intimin, and Stx1. The second most frequent gene pattern was Stx1 and intimin. Twenty of 23 (87.0%) virulent isolates were MDR; the highest prevalence of resistance was recorded for the macrolide-lincosides, followed by the tetracyclines and penicillins. Also, 17 of 23 (74.0%) virulent isolates were resistant to sulfadimethoxine, and 10 of 23 (43.5%) were resistant to trimethoprim-sulfamethoxazole. Additionally, 60 of 74 (81.0%) avirulent isolates were MDR.

Conclusions and Clinical Relevance—The prevalence of multidrug resistance was comparable for virulent and avirulent E coli isolated from diarrheic neonatal calves. Cephalosporins and aminoglycosides had reasonable susceptibility.
Effect of leukoreduction treatment on vascular endothelial growth factor concentration in stored canine blood transfusion products
Authors: Graf Christine , Raila Jens , Schweigert Florian J. , Kohn Barbara
Published: November 2012

Objective—To evaluate vascular endothelial growth factor (VEGF) concentrations in canine blood products treated with or without a leukoreduction filter.

Sample—10 canine blood donors.

Procedures—Dogs underwent blood collection. Five of 10 units were leukoreduced prior to separation into packed RBCs and fresh frozen plasma (FFP). Concentrations of VEGF were measured by ELISA in plasma supernatants from aliquots of packed RBCs obtained immediately after separation and on days 7, 14, and 21 of storage. Fresh frozen plasma samples of 2 filtered and 2 nonfiltered units were examined after storage.

Results—RBC counts in whole blood before and after leukoreduction did not differ significantly, but WBCs and platelets were removed effectively. The VEGF concentration was lower than the detection limit (9 pg/mL) in 9 of 10 plasma samples and in all packed RBC and FFP units immediately after separation. The median VEGF concentrations in 5 nonfiltered packed RBC units were 37, 164, and 110 pg/mL on days 7, 14, and 21 of storage, respectively. In 5 filtered packed RBC and all FFP units, VEGF concentrations remained lower than the detection limit.

Conclusions and Clinical Relevance—Leukoreduction filters were effective in preventing the release of VEGF during storage of canine RBC products.
Effects of leukotriene C4 on the bioelectric properties and ion transport of equine tracheal epithelium
Authors: Lester Guy D. , Rice Brett L.
Published: November 2012

Objective—To determine effects of leukotriene (LT) C4 on ion transport across equine tracheal epithelium.

Sample—Tracheal epithelium from cadavers of 24 horses considered free of respiratory tract disease.

Procedures—Mucosae were mounted into Ussing chambers, and short-circuit current (Isc) was monitored over time. Effects of LTC4 were examined for various conditions, including addition of amiloride (10μM) to the mucosal bath solution, addition of bumetanide (10μM) to the serosal bath solution, addition of barium (1mM) to the serosal bath solution, and substitution of gluconate for chloride and HEPES for bicarbonate in bath solutions. Electrolyte transport was assessed via 22Na and 36Cl isotope fluxes.

Results—Addition of LTC4 (50nM) to the serosal bath solution caused an increase in Isc for basal conditions and a larger increase after pretreatment with amiloride. The increase was negated in part by the addition of bumetanide to the serosal bath solution and further reduced by substitution of HEPES for bicarbonate in bath solutions. Remaining current was reduced to values less than those before treatment with LTC4 by the addition of barium to the serosal solution. There was a small increase in Isc after the addition of amiloride and substitution of gluconate for chloride. Radioisotope flux indicated that addition of LTC4 to the serosal bath solution increased chloride secretion and reduced sodium absorption.

Conclusions and Clinical Relevance—LTC4 stimulated chloride secretion through a predominately bumetanide-sensitive pathway, with a smaller contribution from a bicarbonate-dependent pathway. Thus, LTC4 appears to be a potential mediator of airway hypersecretion in horses.
Use of and satisfaction of pet owners with a clinical behavior service in a companion animal specialty referral practice
Authors: Herron Meghan E. , Lord Linda K.
Published: November 2012

Objective—To determine whether availability of a veterinary behavior service aids in the recruitment of clients to a referral practice who may not have chosen to visit a referral practice otherwise and to assess the priorities and satisfaction of first-time clients.

Design—Prospective survey study.

Sample—87 questionnaires completed by pet owners.

Procedures—Owners of dogs and cats visiting the Behavior Medicine Clinic, a veterinary behavior service, at The Ohio State University Veterinary Medical Center for the first time were asked to participate in a 10-question survey at the end of their initial appointment.

Results—59 of 87 (68%) new clients had never visited the Veterinary Medical Center for any other specialty service; in addition, 56 of 87 (64%) had never taken a pet to any specialty practice prior to their appointment with the Behavior Medicine Clinic. Seventy-four of 85 (87%) clients reported that they were likely to bring their pet to another specialty service on the basis of their experience with the Behavior Medicine Clinic.

Conclusions and Clinical Relevance—On the basis of the survey findings, availability of veterinary behavior services may result in recruitment of first-time clients to a referral center. Clients' experience with a veterinary behavior service may increase their likelihood of visiting other specialty practices within the same hospital, potentially increasing revenue for the entire practice.
Seizures following head trauma in dogs: 259 cases (1999–2009)
Authors: Friedenberg Steven G. , Butler Amy L. , Wei Lai , Moore Sarah A. , Cooper Edward S.
Published: November 2012

Objective—To determine whether dogs with head trauma have a greater incidence of seizures than the general canine patient population.

Design—Retrospective case series.

Animals—259 client-owned dogs.

Procedures—Medical records of dogs evaluated for head trauma at The Ohio State University Veterinary Medical Center from 1999 to 2009 were reviewed. Data were collected regarding the cause of the head trauma, physical examination and neurologic examination findings, comorbidities, and the development of seizures during hospitalization. A telephone survey was conducted to question owners regarding the development of seizures after discharge. Relationships between the nature of the head trauma and the development of seizures were then examined.

Results—3.5% of dogs with head trauma developed in-hospital seizures, and 6.8% of dogs with head trauma for which follow-up information was available developed seizures after hospital discharge, compared with an epilepsy rate of 1.4% in our hospital. Dogs that developed in-hospital seizures were significantly more likely to have been hit by a car or experienced acceleration-deceleration injury. Additionally, 10% of dogs with traumatic brain injury had in-hospital seizures. No visit or patient characteristics were significantly associated with the development of out-of-hospital seizures.

Conclusions and Clinical Relevance—Dogs with head trauma may develop seizures at a greater rate than dogs in the general canine patient population. Particularly in the immediate to early posttraumatic period, clinicians should remain vigilant for the development of posttraumatic seizures and treat patients accordingly.