bluuebunny/crossref_metadata_2025 huggingface dataset:
Acidizing—Lessons from the Past and New Opportunities
Authors: Taylor Robert , Fyten Glen C. , McNeil Fraser
Published: October 2012

The Canadian energy sector pioneered and developed industry-leading oil- and liquids-rich reservoir acidizing technology. This involved new acid additive chemistry and completion techniques. However, many of the newer technical professionals in the industry have not been exposed to this technology. The first section of this paper outlines acidizing technology, with a focus on application to current new opportunities.

Many of the current oil- and liquids-rich plays involve naturally fractured carbonate reservoirs. Acid treatments designed to enhance the conductivity of the existing fracture system can provide more-effective reservoir drainage than proppant fracturing treatments. The second section of this paper discusses how new placement techniques can offer more-effective zonal isolation while reducing completion time and associated costs, and how acid pre-pads can also reduce breakdown pressures and help minimize near-wellbore (NWB) tortuosity effects in many shale and sandstone reservoirs.
Incorporating Geomechanical and Dynamic Hydraulic Fracture Property Changes into Rate-Transient Analysis: Example from the Haynesville Shale
Authors: Clarkson C. R. , Qanbari F. , Nobakht M. , Heffner L.
Published: October 2012

It is well-known that many unconventional reservoirs experience porosity and permeability changes with pressure change during production. In recent work, authors have incorporated geomechanical modeling into production analysis procedures to account for stress-sensitivity of permeability of unconventional gas reservoirs, such as shale gas. Such corrections are necessary for deriving both accurate estimates of reservoir and hydraulic fracture properties from rate-transient analysis and for developing accurate long-term forecasts.

Some shale gas reservoirs are unique in that dynamic changes may occur in both the induced hydraulic fracture AND matrix permeability, which could have a substantial impact on shale gas productivity. Stress-dependence of shale gas permeability has been quantified in the lab by several researchers, but measurements of this kind for propped or unpropped fractures under in-situ conditions are less routinely measured. For the latter, a variety of mechanisms, caused in part or wholly by stress changes in the induced hydraulic fracture, could lead to conductivity changes.

In the current work, we investigate the impact of both stress-dependent matrix permeability and fracture conductivity changes on 1) rate-transient signatures and 2) derived reservoir and hydraulic fracture properties. Stress-dependent matrix permeability is incorporated into rate-transient analysis using modified pseudopressure and pseudotime formulations, and fracture conductivity changes are approximated by applying a time-dependent (dynamic) skin effect.

We demonstrate that when rate-transient analysis incorporates both matrix permeability changes and dynamic skin, the resulting rate-transient signature looks very similar to other shale plays (long-term transient linear flow). Uncorrected data appear to have a very short transient linear flow period, followed by apparent boundary-dominated flow. The impact of the applied corrections on estimates of system permeability and fracture half-length is demonstrated as is the impact on production forecasts.
Modeling 2-Phase Flowback of Multi-Fractured Horizontal Wells Completed in Shale
Authors: Clarkson C. R.
Published: October 2012

Early fluid production and flowing pressure data gathered immediately after fracture-stimulation of multi-fractured horizontal wells may provide an early opportunity to generate long-term forecasts in shale gas reservoirs. These early data, which often consists of hourly (if not more frequent) monitoring of fracture/formation fluid rates, volumes and flowing pressures, are gathered on nearly every well that is completed. Additionally, fluid compositions may be monitored to determine the extent of load fluid recovery, and chemical tracers added during stage treatments to evaluate inflow from each of the stages. There is currently debate within the industry of the usefulness of these data for determining the long-term production performance of the wells. "Rules of thumb" based upon percentage of load fluid recovery are often used by the industry to provide a directional indication of well-performance. More quantitative analysis of the data is rarely performed; it is likely that the multi-phase flow nature of flowback, and the possibility of early data being dominated by wellbore storage effects has deterred many analysts.

In this work, the use of short-term flowback data for quantitative analysis of induced hydraulic fracture properties is critically evaluated. Examples from the Marcellus shale are analyzed. The short (< 48 hours) flowback periods were followed by long-term pressure build-ups (~1 month). Gas/water production data was analyzed using analytical simulation and rate-transient analysis methods designed for analyzing multi-phase coalbed methane (CBM) data. One interpretation is that the early flowback data corresponds to wellbore + fracture volume depletion (storage). It is assumed that fracture storage volume is much greater than wellbore storage. This flow-regime appears consistent with what is interpreted from the long-term pressure buildup data, and from rate-transient analysis of flowback data. Assuming further that the complex fracture network created during stimulation is confined to a cylindrical region around perforation clusters in each stage, fluid production data can be analyzed using a 2-phase tank model simulator to determine fracture permeability and drainage radius, the latter being interpreted to be equivalent to effective (producing) fracture half-length. Total fracture half-length, derived from rate-transient analysis of on-line (post-cleanup) data, verifies the flowback estimates. An analytical forecasting tool that accounts for multiple sequences of post-storage linear flow, followed by late-stage boundary flow, was developed to forecast production using only flowback-derived parameters, volumetric inputs, matrix permeability, completion data and operating constraints. The preliminary forecasts are in very good agreement with on-line production data, after several months of production. The use of flowback data to generate early production forecasts is therefore encouraging, but needs to be tested for a greater data set for this shale play and for other plays.
Practical Use of Simulators for Characterization of Shale Reservoirs
Authors: Alkouh Ahmad , Schechter David , Wattenbarger Robert A. , Patel K.
Published: October 2012

Shale gas/oil wells are a challenge due to the complex reservoirs and well completion designs. Commercial simulators with new automatic features play an important role in shale reservoir characterization. These commercial simulators include special features for modeling horizontal, multi-fracked shale wells with simplified user interfaces. The primary goal of this paper is to compare the simulation of transient and boundary dominated flow with analytical solutions through specialized rate function plots. These comparisons provide a straightforward means for testing the accuracy of automatic gridding features and the simulation methodology. If simulators can match idealized reservoirs accurately, then confidence improves in the matching of actual field cases that may vary from idealized reservoir behavior.

In this work, we tested the accuracy of these simulator features by making numerous simulation runs for various geological and geometric scenarios. We considered different simulation gridding and system models to correctly represent the transient linear flow and its effect on the analysis. Some general gridding rules were developed.

This work investigates the use of an effective permeability equation from analytical solution and its application to several wells in reservoirs located in the Bakken, Barnett, and Eagle Ford formations. Simulation was used to confirm the equation’s accuracy and to show its applicability in fractured shale reservoirs.

Results from this investigation should help engineers select the best automatic features to accurately represent shale wells and then cross check the results using the analytical solution. This study also expanded our understanding of flow behavior in production data which may be used to improve modeling shale wells for better agreement with the analytical solutions.
What's Positive About Negative Intercepts
Authors: Thompson J. M. , Liang P. , Mattar L.
Published: October 2012

The paradigm shift towards horizontal well drilling with multiple fracture stages to exploit unconventional plays has unsurprisingly resulted in a rapid growth of questions regarding the interpretation of the associated well performance signatures on log-log diagnostic and specialized analysis plots. Log-log diagnostic plots perhaps best illustrate the sequence of flow-regimes which may result from this completion type. However, the long-term behavior one should expect to see on a square-root-time plot from the sequence is seldom presented in the literature, in spite of the ubiquitous use of linear flow specialized plots for unconventional well performance analysis. This paper addresses frequently asked questions regarding the meaning of the commonly observed negative y-intercepts on these plots. Using multi-frac horizontal well analytical models, synthetic production data sets were generated to evaluate various hydraulic-fracture geometries. The resulting data signatures are presented on a dimensionless specialized plot to reveal the behavior of the early linear, transitional and (late) compound linear flow regimes. This study illustrates that negative intercepts are typically created from the transitional period following the first linear flow and quantifies both the magnitude and sign of the resulting intercept produced from compound linear flow based on various hydraulic fracture length and spacing combinations. Using a field example, this work also demonstrates that false interpretations of compound linear flow may arise due to the misinterpretation of the prolonged transitional flow period between the first and second linear flow regimes.
Comparison of Empirical Decline Curve Methods for Shale Wells
Authors: Kanfar Mohammed S , Wattenbarger R. A.
Published: October 2012

Analyzing shale wells using traditional decline curve methods is problematic because of the nature of reservoir properties and flow behavior in typical shale wells. New empirical methods were developed to model the special production decline of shales. These methods were formulated using different mathematical and statistical bases and result in different forecasts. Hence, engineers have a variety of methods that may give different estimates for ultimate recovery when analyzing shale wells. In this work, four recently developed decline curve methods, along with the traditional Arps method, were compared.

The four recent methods compared here were empirically formulated for shale wells and tight gas wells. They are: a) the Power Law Exponential Decline, b) the Stretched Exponential Decline, c) Duong’s Method, and d) the Logistic Growth Model. Each method has different tuning parameters and equation forms. In this work, the methods were programmed and automated by using nonlinear regression to match the production "history" of a well. In addition, they were compared in terms of "goodness of fit" to the history data and reliability of automation as well as production forecast and ultimate recovery estimation. These methods were compared with simulation models in addition to field data from Barnett Shale, Bakken Shale, and the Eagle Ford Shale.

Each of these methods may have application for different cases. It may be advisable to program each of these methods for optional usage in applications. But this current paper should allow engineers to understand better the characteristics of each method and to choose the method that best models their wells under various circumstances.
Sleeve Activation Sleeve Activation in Open-hole Fracturing Systems: A Ball Selection Study
Authors: Baihly Jason , Aviles Isaac , Johnson Joshua , Melenyzer George
Published: October 2012

During the past decade, the completion technique used in liquid-rich unconventional plays in North America has undergone a transformation. Today, the vast majority of completions in these areas are open-hole (OH) graduated ball-drop fracturing isolation systems. This preferred completion type for horizontal wells is driven by the efficiency gains in fracturing operations and the production gains when compared to previously used completion techniques. Thousands of open-hole fracturing systems are run each year, with a continuously growing stage count.

Graduated ball-drop type completions rely on a sliding sleeve activated by a ball dropped from surface. Each ball travels the length of the lateral well to its intended operational depth, at which it meets a mated seat and isolates the wellbore below. Once the ball is in position, the sliding sleeve opens via the hydraulic force on the ball and seat, allowing a fracturing stage to commence. This dual function of the ball—activation and sealing—is of extreme importance for the stimulation treatment process. If the ball fails, it will result in bypassed pay zones and unintentional refracturing of previously stimulated zones. Although sometimes surface pressures can be used to infer ball behavior, often the pressure signals observed at surface cannot guarantee successful ball performance.

This paper will present an extensive study of ball performance under pressure for the most common ball materials in the industry. Phenolic, composite and metal alloy materials were explored with the pros and cons for each investigated. In particular three main areas were analyzed: 1) molding, layering and extrusion of material versus inconsistencies in ball performance; 2) ball deformation at high pressure versus pressure required to bring the ball off seat; and 3) comparison of the performance of phenolic, composite and metal alloy materials for ball fabrication and their performance at high temperature.

The conclusions from this paper provide operators the necessary information to consider when making completion and ball material decisions in their field operations. In particular, the results of this testing may illuminate some previously unexplainable occurrences in graduated ball sliding-sleeve systems. This testing clarified that not all fracturing balls pumped in horizontal wells perform equivalently under wellbore fracture conditions.
Streamlined Completions Process: An Eagle Ford Shale Case History
Authors: Arguijo Andrew L. , Morford Lee , Baihly Jason , Aviles Isaac
Published: October 2012

The Eagle Ford shale is a hydrocarbon-producing formation of significant importance due to its capability for producing at high-liquid/gas ratios, more so than other traditional shale plays. Situated in south Texas, the total Eagle Ford liquids production in 2007 was less than 21,000 bbl total. In 2011, production averaged 65,500 BOPD in the play (EIA, 2011). Activity in the Eagle Ford continues to increase because the benefits from producing high liquid yields across much of the play, along with attractive commodity prices, have made the Eagle Ford a more attractive development over many other shale reservoirs.

The rapid development of the Eagle Ford shale was enabled by horizontal drilling. In 2007 none of the reported production was from horizontal wells. In 2011 alone over 2,800 drilling permits were issued, virtually all of them for horizontal wells (RigData, 2012). The Eagle Ford shale has low-clay content, high-carbonate content, and is in an extensional basin, making it conducive to somewhat complex hydraulic fracturing (Martin et al, 2011). The plug and perforating technique has become the preferred completion method in the play due to multiple entry points creating complex fractures at a minimal cost. This completion technique requires a mechanical means for conveying perforating guns, such as coiled tubing (CT), wireline tractor or stick pipe, for the first fracturing stage at the toe of the well.

To streamline their completion process, an Eagle Ford operator chose to use an initiator valve that is run at the toe of the well as part of the final completion design. This pressure activated valve is capable of initiating operations on the first fracturing stage without the need for CT or other mechanical means of conveyance of perforating guns. Simple and robust, the valve is activated by a pressure increase from the surface. The valve uses a rupture disc for precise activation and a helical port design that allows for hydraulic fracturing to be performed through the valve into the cement and the formation. With over a dozen wells completed in the Eagle Ford formation by the operator, the valve has provided logistical and economic benefits to the streamlined completion process.

This paper describes the initiator valve completion tool and its application in the Eagle Ford shale. A case history is presented to show the specific design and operation of the initiator valve, as well as its benefits over other completion practices that target the first stage in a closed lateral system. Detailed activation of the valve and fracturing data through the valve are also presented.
Considerations for Pore Volume Stress Effects in Over-pressured Shale Gas under Controlled Drawdown Well Management Strategy
Authors: Akande Jesse , Spivey J. P.
Published: October 2012

The high decline rate observed in over pressured shale has attracted the attention of the industry, and better well management procedures for long term productivity improvement are still evolving. Operators are recognizing some benefit in controlled rate (controlled drawdown) production as one way of improving well performance for the wells in over pressured stress sensitive formations.

During uncontrolled rate production because of high drawdown, the permeability in stress sensitive shales decays faster because of increased stress. Often high initial gas rate is accompanied by high decline rate as the permeability reduction takes effect. In addition, proppant could also be produced back, crushed or embedded in the formation. However, controlled rate production minimizes the rate decline, albeit at reduced initial gas rate. Modelers resort to using different stress permeability decay coefficients for these two production strategies. Higher values are assigned to uncontrolled rate production to produce lower EUR. This approach, although convenient, requires different permeability versus stress tables depending on the production strategy.

Porosity and pore volume reduction in shales could be as high as 20 percent due to changes in net stress. The pore volume reduction provides in situ energy for gas recovery. The increased rate of permeability decay due to changing in situ stresses reduces the effectiveness of pressure support from pore volume reduction as fractures close under stress.. Controlled rate production strategy slows down permeability decay rate and this enables better use of pore volume energy. The pore volume consideration could provide additional gain to EUR for controlled rate.

Our analytical simulation model couples geomechanics permeability and porosity stress coefficients and evaluates well performance under moderate and low net stress sensitivity. Haynesville and Marcellus shales were evaluated. The importance of pore volume stress effect from the stand point of well performance evaluation and reservoir characterization is assessed.
Innovative Nanoparticle Drilling Fluid and Its Benefits to Horizontal or Extended Reach Drilling
Authors: Hareland Geir , Wu Andrew , Lei Lingyun , Husein Maen M. , Zakaria Mohammad F.
Published: October 2012

Development of new exploration, drilling and completion technologies in the past two decades have led to the opening of new plays in North America targeting unconventional resources. Lots of innovative drilling fluids have been developed and applied in the drilling and completion engineering. The demands encountered drilling highly deviated wells include the effective control of torque and drag. Therefore one of the applications of the innovative drilling fluids is to lower friction coefficient between drillstring and wellbore, which will reduce the drag and make it possible to drill longer horizontal or extended distances during horizontal or extended reach wells.

This paper first briefly introduces the problems from the drag when drilling horizontal or extended reach wells, calculation of torque and drag with analytical models and the shortcomings of those models. Then addresses how the lower friction coefficient from the innovative fluid will bring benefit to the horizontal or extended reach drilling, where finite element method (FEM) is introduced to analyze the interaction between the wellbore and drillstring. Finally three case studies are detailed and results are also analyzed.

The three examples are calculating the drag and torque along the entire drillstring, comparing the drag and torque with different friction coefficients with constant torque, buoyancy and downhole weight on bit, and obtaining the increment of horizontal section when using the innovative drilling fluid. The tension or compression force distribution along the entire drillstring is clearly shown through graphs or plotting. The results and analysis with FEM show that the low friction coefficient from the innovative drilling fluid has a great benefit in horizontal or extended reach drilling, increasing the current rig and equipment reach limit substantially.

The analysis method presented in this paper can provide a solid base for drilling engineers so that they can accurately estimate the extended reach with this new drilling fluid. It will improve the drilling efficiency and reduce the total cost, especially in unconventional well drilling in that less and longer wells can be used to drain the reservoirs.
New Advances in Production Data Analysis of Hydraulically Fractured Tight Reservoirs
Authors: Siddiqui Shahab K. , Ali Afsar , Dehghanpour Hassan
Published: October 2012

Tight reservoirs stimulated by multistage hydraulic fracturing are commonly described by a dual porosity model. This model consists of homogeneous matrix blocks separated by vertical hydraulic fractures. This paper hypothesizes that the production data of some fractured horizontal wells may also be described by a triple porosity model. The third medium can be either reactivated natural fractures or thin horizontal beds with a higher permeability. We test this hypothesis by extending the existing triple porosity models to develop an analytical procedure for determining the reservoir parameters. We derive the simplified equations for different regions of the rate-time plot including linear and bilinear flow regions. These equations can be used to calculate the effective fracture half-length, matrix permeability and length of micro-fractures. We use the proposed model to analyze the production data of two wells drilled in Barnett shale. The results show that a dual porosity model is more appropriate for describing Barnett shale data. Even if the micro-fractures are present they are not inter-connected and the length scale is much smaller than the hydraulic fracture spacing.

The second part of this paper focuses on analyzing production data of tight oil reservoirs. We plot rate-normalized pressure (RNP) versus material balance time (MBT) of two wells drilled in Cardium and Bakken formations. We observe a half-slope followed by a unit-slope in both cases. This paper hypothesizes that the half slope reflects the linear transient flow regime, and the unit slope reflects the linear pseudosteady state (PSS) flow. We test this hypothesis by developing a new model for pseudo steady state flow when pressure interference occurs between two adjacent hydraulic fractures. We determine the reservoir properties by both PSS and transient analysis methods. For Cardium well, both methods give very close results. For Bakken well, both methods give relatively close results. We conclude that analyzing the late time production data of tight oil wells complement the linear transient analysis and can be used to calculate the stimulated reservoir volume, which can eventually help the industry to optimize the fracturing operation.
Using Microseismicity to Understand Subsurface Fracture Systems and Increase the Effectiveness of Completions: Eagle Ford Shale, TX
Authors: Detring John P. , Williams-Stroud Sherilyn
Published: October 2012

Existing natural fractures often have a significant impact on both stimulation and production of oil and gas wells. Effective exploitation of unconventional reservoirs requires the understanding of the local tectonic history and the present day stress regime. Signal strength, high quality reflection seismic, microseismic imaging, and moderate structural complexity of the liquids-rich gas and tight oil Eagle Ford shale makes it an ideal place to study hydraulic fracturing in tight rocks. Microseismic monitoring results showed clear structural trends relating to reactivation of existing faults and fractures, and rock failure mechanisms determined through source mechanism inversions. These results provided critical information to the operator for optimizing the hydraulic fracture design.

Microseismic data collected using a surface array allowed the full geometry of the result to be viewed with no directional bias. The geometry of the microseismicity trends related to fracturing developed during the stimulation treatment were representative of the true geometry of the structure. The large aperture and wide azimuth of the monitoring array facilitated the determination of source mechanisms from every event detected, which provided full coverage of the focal sphere of each source mechanism. The events identified two different source mechanisms, indicating a different failure mechanism for fractures than for reactivated faults.

Microseismicity with a NE-SW orientation are interpreted to be related to either induced or reactivated fractures. Microseismicity also formed trends that are contiguous across more than one wellbore in a ENE-WSW direction. These trends are interpreted to have formed as a result of fault reactivation. Source mechanisms from faulting parallal to SHmax have failure planes that strike NE-SW with normal dip-slip failure on steeply-dipping planes. Those from fault reactivation have strike-slip failure on ENE-WSW striking failure planes. The orientations of the fault-related trends are parallel to extensional Gulf of Mexico growth faulting. The microseismicity trends associated with fracturing form at an angle of approximately 25° to the faulting trends and are parallel to SHmax.

Microseismicity trends associated with faults are used to project where faults will intersect adjacent wells. Identification of these faults in the reservoir via microseismic mapping allow operators to modify their treatment parameters and stage spacing in order to avoid geologic hazards. The operator combines the treatment pump parameters for the wells with the additional structural understanding gained from the analysis of fracture trends and source mechanisms to identify zones that should be avoided in subsequent treatments. In addition, the mapped microseismicity provides critical information that was used to modify well spacing for subsequent wells, thereby optimizing the completion plan and dramatically cutting costs.
Case-Based Reasoning Technology Used to Provide Early Indications of Potential NPT-Related Problems while Drilling the Viking
Authors: Le Dean
Published: October 2012

There is a considerable value proposition for drilling personnel to be able to use real-time data and have an intelligent technology scan for potential problems before they are realized. To then further offer resolution options for the potential problem is an even greater value proposition.

Use of automated intelligent technologies to interpret data and alert users of potential problems is in existence for many commercial and industrial applications. These technologies are frequently employed in surveillance systems such as traffic control, security, and internet usage. The historic challenge for most of these technologies in field applications is that many of the problem scenarios have varying degrees of parameter differences. As such, rule-based technologies have not met expectations. This challenge has been resolved through use of an intelligent technology that evaluates and ranks a problem scenario’s parameters based on case similarity. In other words, this technology compares the relative differences of problem parameters to baseline case history problem parameters. This approach is a much better representation of reality in the field, where no two problems are exactly the same – they are only similar.

An intelligent real-time technology utilizing case-based reasoning can now be deployed in drilling operations to help recognize and mitigate non-productive time problems before they occur, thereby improving overall drilling efficiency. This software technology recalls human and situational experience across rigs, assets and regions. By continuously monitoring the real-time data-streams from ongoing drilling operations, it compares the current situation with past experience (cases). When the current situation is similar to a case, an alert is sent to users and the case is displayed along with lessons learned, advice and best practices.

This technology was successfully deployed in a proof of concept with junior oil company, drilling the Viking formation. This paper highlights the theory behind the technology, deployment and integration with the junior oil company, and the results of the project, including a case study in which the technology sent an alert of a potential stuck pipe incident and suggested remedial actions to address the problem before it occurred. This paper concludes with how the technology can be continually adapted to new downhole drilling challenges.
Seed Vigor and the Uniformity of Emergence of Corn Seedlings
Authors: Egli D.B. , Rucker M.
Published: November 2012

Seed vigor is defined as those “seed properties that determine the potential for rapid, uniform emergence and development of seedlings under a wide range of field conditions.” Seedlings from high‐vigor seed lots are expected to emerge more uniformly than those from low‐vigor lots. We tested this hypothesis in a series of greenhouse and growth chamber experiments with several high‐ and low‐vigor corn (Zea mays L.) samples that had high standard germination. Seed‐vigor levels were estimated with the saturated cold test where the seeds were stressed with low temperature (10°C) and field soil for 7 d and then germination was measured after 5 d at 25°C. The uniformity index (UI) (time from 10 to 90% of final emergence) was estimated by planting seeds 3.8 cm deep in soil and counting emergence every 6 h in greenhouse and growth chamber experiments. Lowering the soil temperature from roughly 23 to 15°C increased the time to 10% of final emergence (T10) from about 100 to more than 300 h and increased the UI. Low‐vigor seed always had a larger UI than high‐ vigor seed, but the difference was less when the seedlings emerged rapidly (UIs were 20 to 30 h) than when they emerged slowly (maximum of ~80 h for high‐vigor seed and 140 h for low‐vigor seed). High‐vigor seed had more uniform emergence, but soil temperature and the time to emergence also influenced uniformity.
Loss of Maize Seed Vigor as Affected by Biochemical Changes during Hydropriming
Authors: Wattanakulpakin Papassorn , Photchanachai Songsin , Miyagawa Shuichi , Ratanakhanokchai Khanok
Published: November 2012

Hydropriming has both positive and negative effects on seed performance. Hydropriming (for 6 to 30 h) was performed in the maize (Zea mays L.) seed lines ‘TSK 11’ and ‘PS 54’. A short hydropriming time of 6 to 12 h improved seed germination in both lines. An improvement in seed vigor, as investigated by germination after accelerated aging, was observed after hydropriming for 6 and 12 h in ‘TSK 11’ seeds, but only after 6 h of hydropriming in ‘PS 54’. The reduction in seed vigor occurred faster in ‘PS 54’ than in ‘TSK 11’, which was confirmed at hydropriming times of 12 and 18 h, respectively. The higher activities of antioxidant enzymes, that is, superoxide dismutase (SOD) and ascorbate peroxidase (APX) in ‘TSK 11’, and SOD, peroxidase (POD), and APX in ‘PS 54’, correlated with enhanced maize seed vigor after priming. The deterioration of primed maize seeds was linked to the process of lipid peroxidation, indicated by the generation of malondialdehyde during imbibition, and acetaldehyde and ethanol during redrying. Additional indicators were identified: a reduction in the antioxidant activities of SOD, CAT, and APX for ‘TSK 11’, and SOD and CAT for ‘PS 54’, decreased raffinose content, and increased amylase activity. A less compact cellular ultrastructure was observed in hydroprimed seeds and was associated with seed deterioration. The different responses in physiological and biochemical attributes induced by hydropriming were related to their genotype and partially affected by the initial characteristic differences between the two maize lines causing different maize seed appearance.
Nitrogen Use Efficiency in a Genetically Diverse Set of Winter Oilseed Rape (Brassica napus L.)
Authors: Kessel Bettina , Schierholt Antje , Becker Heiko C.
Published: November 2012

Genetic variation in N uptake and utilization was investigated in a set of genetically diverse oilseed rape (Brassica napus L.) genotypes, including hybrid, modern, and old cultivars and resynthesized lines. A total of 36 genotypes were grown at seven locations with two levels of N supply: no fertilization and optimal fertilization (between 160 and 220 kg ha–1 N, depending on regional recommendations). The hybrid cultivars had the highest yields and the old land races and resynthesized lines had the lowest yields. This ranking of the various groups was consistent and independent of the N level. Genetic variation exists for both the uptake efficiency and the utilization efficiency. In the presence of low N levels, variation in N use efficiency is mainly due to differences in uptake efficiency whereas differences in utilization efficiency were more important in the presence of high N fertilization.
Barley Yellow Dwarf Virus Effects on Cereal Plant Growth and Transpiration
Authors: Erion Gabriel G. , Riedell Walter E.
Published: November 2012

Little is known about how changes in root system characteristics caused by barley yellow dwarf virus (BYDV) infection affect transpiration in cereal plants. Objectives of these greenhouse studies were to elucidate virus infection effects on plant growth and apparent transpiration rate in oats (Avena sativa L. ‘Coast Black’) and barley (Hordeum vulgare L. ‘Robust’). Seedlings were infested at the first leaf stage (13 d after planting) with viruliferous (BYDV) or nonviruliferous bird cherry oat aphids (Rhopalosiphum padi L.) for 48 h. Aphids were removed and plants grown for an additional 26 d. Root and shoot dry weights, root‐to‐shoot weight ratio, leaf blade dry weight, leaf blade area, and apparent transpiration rate were measured. Data were subjected to ANOVA analysis. Viral disease symptoms, such as reduced tiller number, stunting, leaf chlorosis, and reddening, were more pronounced in oats than in barley. Virus infection decreased root dry weight by 88% in oats and 35% in barley, reduced root‐to‐shoot ratio by 65% in oats and 36% in barley, decreased leaf blade area by 75% in oats and 36% in barley, and reduced apparent transpiration by 73% in oats and 33% in barley. Thus, BYDV infection caused significant reductions in growth and water movement through the transpiration stream to a greater extent in oats than in barley, indicating that Coast Black oats was sensitive to BYDV infection whereas Robust barley was considerably more tolerant.
Variability for Drought Related Traits of Virginia‐Type Peanut Cultivars and Advanced Breeding Lines
Authors: Balota Maria , Isleib Thomas G. , Tallury Shyam
Published: November 2012

Water deficit is increasingly becoming a limiting factor for peanut production in the Virginia–Carolina (VC) peanut growing region. Even though extensive research efforts have been made worldwide to improve drought tolerance in peanut, performance of genotypes largely depends on the environment in which they grow and no such information is available for the VC area. The objective of this study was to determine the variability for CO2 assimilation rate (A), stomatal conductance (gs), transpiration efficiency (A:gs), specific leaf area (SLA), chlorophyll content estimate (soil plant analysis development [SPAD] meter readings), stomata number per square centimeter and per leaf, and canopy temperature depression (CTD) of 18 peanut (Arachis hypogaea L.) virginia‐type cultivars and breeding lines grown in rain‐fed plots in southeastern Virginia. The relationship between physiological and agronomic traits was then analyzed. Genotype had a significant effect on all physiological traits. Excepting CTD, year also had a significant effect on all physiological characteristics. The genotype × year interaction was not significant for A, gs, A:gs, SPAD, and SLA suggesting dominant controlling factors for these traits. Under water stress in both years, pod yield was consistently associated with A (higher A results in higher yield) and SPAD (greener leaves results in higher yield). These results suggest that development of cultivars with greener leaves and higher A when gs is low may ensure better yields under rain‐fed conditions in the VC region.
Decision support model for water policy in the presence of waterlogging and salinity
Authors: Khan Shahbaz , Rana Tariq , Hanjra Munir A. , Robinson David
Published: October 2012

Irrigation improves food security and human wellbeing. Poorly managed irrigation can raise watertables inducing waterlogging and salinity. Excessive groundwater withdrawals can lower watertables, impacting drainage and interlinked hydroeconomic systems. Sustainable irrigation management thus remains a global water policy challenge. This study develops a framework for using market-based instruments for net groundwater recharge management to mitigate waterlogging and salinity, taking selected settings in the Murray–Darling Basin in Australia as a case study. The SWAGMAN® series of models are developed which enable farmers to meet their paddock-scale recharge targets while optimizing profits, and to link their onfarm land and water management actions to regional recharge goals. Spatial quantification of recharge effectively converts a diffuse source groundwater recharge issue to a point source problem, enabling assignment of private property rights to a common pool issue. Integrated hydrological, economic, and institutional models, as well as farm case studies, are used to evaluate the efficiency of various net recharge management options, specifically a cap-and-trade model. The results show that the net gains from the scheme would be small, about 1% of annual farm income, which do not support its outright adoption. Consideration of offsite/indirect impacts may, however, alter this calculus.
Implementing participatory irrigation management in Thailand
Authors: Kumnerdpet Wachiraporn , Sinclair A. John
Published: October 2012

Participatory Irrigation Management (PIM) was formally adopted in Thailand in 2004. The involvement of farmers in water management decision making is necessary to meet the implementation challenges of this initiative. As such, the research presented in this paper considered the level of farmer involvement in water management and decision making, and the lessons learned by both government officials and farmers through the implementation of PIM in Thailand to date. Data collected from document reviews and a total of 44 semistructured face-to-face and telephone interviews of public irrigation officials and farmers nationwide show that farmers possess the full potential to manage irrigation water by themselves, and that they are making important changes to governance systems for irrigation. However, they need both the opportunity and the continuing supportof public irrigation officials for success, which is currently only being partly achieved through the PIM initiative.
Coronal Vertebral Clefts: A Radiological Indicator for Chromosomal Aberrations
Authors: Doberentz Elke , Schumacher Reinhard , Gembruch Ulrich , Gasser Jürg Andreas , Müller Annette M.
Published: October 2012

Coronal clefts—a radiolucent band running through at least one vertebral body, visualized in the lateral spinal radiograph and discussed as a physiological variation of the fetal vertebral ossification pattern—are often found in fetal autopsies with trisomies. Published studies are missing concerning the question of whether this finding could serve as a diagnostic radiological or even ultrasonographic sign. We studied the incidence of radiological coronal clefts and their association with chromosomal aberrations in 443 fetuses (mostly medically induced abortions). In 42 of the 443 fetuses (9.5%), coronal clefts were visualized. The majority (71%) were localized in the lumbar spine. No cervical or singular sacral clefts were detected. Twenty-five of the 42 fetuses (60%) displaying coronal clefts had chromosomal aberrations, either as a trisomy (13 or 21) or as monosomy X. Histologically, coronal clefts showed a missing central ossification of the vertebral body. Remnants of the notochord could be excluded. Hence, coronal clefts represent a variant ossification of vertebral bodies in fetal development that is found almost exclusively in fetuses with chromosomal aberrations or severe congenital malformations. This finding could be a helpful supplement to prenatal diagnostics and fetal autopsy. On the other hand, the genetic diagnosis of chromosomal aberration, especially trisomy, does not automatically imply the presence of coronal clefts.
Evaluation of a ketamine-propofol drug combination with or without dexmedetomidine for intravenous anesthesia in cats undergoing ovariectomy
Authors: Ravasio Giuliano , Gallo Martina , Beccaglia Michela , Comazzi Stefano , Gelain Maria Elena , Fonda Diego , Bronzo Valerio , Zonca Annalisa
Published: October 2012

Objective—To evaluate the use of a ketamine-propofol combination, with or without dexmedetomidine, in cats undergoing ovariectomy and to assess Heinz body formation following administration of these drugs.

Design—Randomized clinical trial.

Animals—15 client-owned female cats.

Procedures—Anesthesia was induced with a ketamine (2.0 mg/kg [0.91 mg/lb])-propofol (2.0 mg/kg) combination with (n = 7) or without (8) dexmedetomidine (0.003 mg/kg [0.0013 mg/lb]) and was maintained via continuous IV infusion of a 1:1 ketamine-propofol combination (administration rate for each drug, 10.0 mg/kg/h [4.54 mg/lb/h]). Cats underwent ovariectomy; duration of infusion was 25 minutes. Physiologic variables were measured at predetermined time points. Heinz bodies were quantified via examination of blood smears. Numeric scales were used to assess quality of recovery, degree of sedation, and signs of pain after surgery.

Results—The ketamine-propofol group had a significantly higher mean heart rate at several time points during drug infusion, a significantly shorter time from the end of infusion to extubation (7 vs 29 minutes), and significantly lower sedation scores for the first hour after surgery than did the ketamine-propofol-dexmedetomidine group. Other variables were similar between groups; recovery was smooth, and anesthesia and postoperative analgesia were deemed adequate for all cats. The number of RBCs with Heinz bodies was not increased after surgery, compared with values immediately after anesthetic induction.

Conclusions and Clinical Relevance—Total IV anesthesia with a ketamine-propofol combination, with or without dexmedetomidine, appeared to be effective in healthy cats. These short-term infusions produced smooth recovery and adequate analgesia during the postoperative period.
In vitro surface biocompatibility of high-content silicon-substituted calcium phosphate ceramics
Authors: Mostafa Nasser , Shaltout Abdallah , Radev Lachezar , Hassan Hassan
Published: October 2012

The present work investigates surface biocompatibility of silicon-substituted calcium phosphate ceramics. Different silicon-substituted calcium phosphate ceramic bodies were prepared from co-precipitated powders by sintering at 1300°C. The in vitro bioactivity of the ceramics was assessed in simulated body fluid (SBF) at 37°C for periods up to 4 weeks. The changes in the surface morphology and composition were determined by scanning electron microscopy (SEM) coupled with electron probe microanalysis and energy dispersive spectrometer (EDX). Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to observe the change in ionic concentration of SBF after removal of the samples. The bioactivity of the ceramics increased with an increasing silicate ion substitution in a systematic way. The surface of ceramics with 2.23% silicon substitution was partially covered with apatite layer after one week, while ceramics with 8.1% silicon substitution were completely covered with apatite in the first week. The porous microstructure of high-concentration Si-substituted ceramics helps the dissolution of surface ions and the leaching process. This allows SBF to reach supersaturation in a short time and accelerate the deposition of apatite layer.
A theoretical study on the red- and blue-shift hydrogen bonds of cis-trans formic acid dimer in excited states
Authors: Yang Dapeng , Yang Yonggang , Liu Yufang
Published: October 2012

The excited states of cis-trans formic acid dimer and its monomers have been investigated by time-dependent density functional theory (TDDFT) method. The formation of intermolecular hydrogen bonds O1-H1...O2=C2 and C2-H2...O4=C1 induces bond length lengthening of the groups related to the hydrogen bond, while that of the C2-H2 group is shortened. It is demonstrated that the red-shift hydrogen bond O1-H1...O2=C2 and blue-shift hydrogen bond C2-H2...O4=C1 are both weakened when excited to the S1 state. Moreover, it is found that the groups related to the formation of red-shift hydrogen bond O1-H1...O2=C2 are both strengthened in the S1 state, while the groups related to the blue-shift hydrogen bond C2-H2...O4=C1 are both weakened. This will provide information for the photochemistry and photophysical study of red- and blue-shift hydrogen bond.
Biogenic iron compounds: XRD, Mossbauer and FTIR study
Authors: Shopska Maya , Cherkezova-Zheleva Zara , Paneva Daniela , Iliev Mihail , Kadinov Georgi , Mitov Ivan , Groudeva Veneta
Published: October 2012

Materials based on biogenic iron oxides, which are a product of the metabolic activities of the neutrophilic iron-oxidizing bacteria (NIOB) from Sphaerotilus-Leptothrix group, were investigated. Natural microbial probes were collected from freshwater flow from Vitosha Mountain (Bulgaria) and cultivated under laboratory conditions in respect to select suitable cultures and conditions (nutrition media) for biomaterial accumulation of biogenic oxides. Samples were studied by physicochemical methods: X-ray diffraction, Mossbauer spectroscopy and IR spectroscopy. Their phase composition and physicochemical properties were obtained. Presence of both amorphous and crystal phase (ultra- and highly dispersed particles) was proved. Iron-containing compound in the natural biomass consists of α-FeOOH. The cultivated materials have more complex composition with iron-containing ingredients as α-FeOOH, Γ-FeOOH, Γ-Fe2O3 and Fe3O4. The sample of natural biomass was tested in reaction of CO oxidation and it showed potential to be used as catalyst support.