bluuebunny/crossref_metadata_2025 huggingface dataset:
Avaliação nutricional, durante a amamentação, de tourinhos em pastejo recebendo suplementação proteica da amamentação à terminação
Authors: Fernandes Henrique Jorge , Paulino Mário Fonseca , Detmann Edenio , Valadares Filho Sebastião de Campos , Silva Aline Gomes da , Porto Marlos Oliveira , Rocha Anilza Andréia da , Biancardi Gabriel Figueiredo
Published: March 2012

O objetivo neste estudo foi avaliar as condições nutricionais de tourinhos em aleitamento, a pasto, recebendo suplementação com concentrados proteicos durante a época de transição águas-seca. Foram utilizados 52 bezerros mestiços com idade média inicial de 130 dias. Os animais foram distribuídos em quatro lotes, alojados em piquetes de Brachiaria decumbens Stapf junto com suas mães, onde receberam uma das quatro estratégias de suplementação: três suplementos concentrados, ou sal mineral (controle). Os suplementos concentrados diferiram quanto ao nível de proteína. Após 45 dias, realizou-se a avaliação nutricional dos animais, que incluiu a estimação do consumo e da digestão de nutrientes e das características do metabolismo proteico. A estimação do consumo e da digestibilidade foi feita utilizando-se os indicadores: LIPE®, dióxido de titânio e fibra em detergente neutro indigestível. Realizou-se ainda coleta de amostras de urina e de sangue. O efeito de suplementação e os efeitos linear e quadrático do nível de proteína no concentrado foram avaliados pela decomposição da soma de quadrados em contrastes ortogonais, adotando-se α = 0,10. O consumo de concentrado substituiu parte do pasto ingerido pelos bezerros e aumentou a ingestão de proteína, a digestibilidade da matéria seca e matéria orgânica, o teor de nutrientes digestíveis totais e a excreção de nitrogênio na urina. O nível de proteína no suplemento tem efeito linear positivo sobre a ingestão diária de proteína, a digestibilidade de todos os nutrientes e o teor de nutrientes digestíveis totais e efeito quadrático sobre a excreção de nitrogênio na forma de ureia na urina.
Ensino-aprendizagem numa perspectiva crítica: relatos de uma experiência
Authors: Mafra Flávia Luciana Naves , Cappelle Mônica Carvalho Alves , Mendonça Maria Cristina Angélico , Oliveira Maria de Lourdes Souza , Paula Maria das Graças
Published: March 2012

Com este artigo, temos por objetivo apresentar uma reflexão coletiva sobre uma experiência de ensino-aprendizagem, partindo de uma perspectiva crítica, para um curso de pós-graduação stricto sensu em Administração. O interesse não é, entretanto, apenas relatar uma experiência, mas também tentar aprender com esse processo, contribuindo, inclusive, para novas edições da disciplina. Com base no método da pesquisa-ação, neste artigo, revelamos ainda os percalços cotidianos no processo de ensino-aprendizagem da disciplina intitulada "Reflexões Críticas em Administração", a partir das visões e experiências de cinco professoras do curso de Administração. A utilização do termo "críticas" era, a nosso ver, a alternativa mais efetiva naquele momento para abarcar a diversidade de posições, experiências e ancoragens teórico-metológicas que caracterizavam a própria identidade do grupo de professoras. Como aporte teórico, enfatizamos elementos que são comuns em várias correntes de debate sobre perspectivas críticas, tais como a complexidade dos fenômenos sociais, a questão da autonomia e a importância da criatividade. Tratamos, portanto, de pensar uma perspectiva crítica não apenas a partir de conteúdos, mas também da forma como seriam construídos e socializados. Isso estaria condizente com a proposta da epistemologia da complexidade. Na disciplina, trabalhamos com estudantes de mestrado e doutorado por meio de incursões teórico-metodológicas em temas específicos. Ao final, foram produzidos trabalhos com diferentes características, abordando os temas debatidos a partir da ótica de cada grupo de estudantes-autores. Entretanto, a riqueza do processo e seus obstáculos não podem ser avaliados apenas com base nos resultados ou trabalhos produzidos. A utilização de avaliações periódicas produzidas por estudantes e professoras ajudou a construir a configuração das relações sociais - inclusive dos processos de ensino-aprendizagem - que envolviam esses atores.
Nonchemical and Herbicide Treatments for Management of Japanese Stiltgrass (Microstegium vimineum)
Authors: Ward Jeffrey Stuart , Mervosh Todd L.
Published: March 2012

Japanese stiltgrass, an annual grass species native to eastern Asia, has become a serious invasive-plant problem in the eastern United States. We compared the efficacy of herbicides and nonchemical options found effective for controlling stiltgrass in earlier studies, with organic herbicides and herbicides used at reduced rates in a wooded floodplain along the lower Connecticut River. We compared the effect of 2 yr of conventional and alternative treatments on cover of other nonnative and native species. Four blocks of 18 plots (3 by 4 m [9.8 by 13.1 ft]) were established in May 2008. Treatments included directed heating with a propane torch (June, July), hand-pulling (July), mowing with a string trimmer (July, August), foliar applications of household vinegar [5% acetic acid] (June, July) and the herbicides imazapic (June), pelargonic acid (June, July), and pelargonic acid plus pendimethalin (June). The following herbicides were applied at labeled doses and at one-fourth labeled doses: fenoxaprop-p-ethyl (July), glufosinate (August), and glyphosate (August). Stiltgrass cover and height were evaluated periodically, and plant samples were collected in autumn of 2008 and 2009 to determine the number of viable seeds produced. Final evaluations were conducted in June 2010 after 2 yr of treatment. Stiltgrass cover averaged 88% on untreated plots in fall. All treatments reduced stiltgrass cover and seed production. The least-effective treatments were hand-pulling, pelargonic acid, and vinegar in July. Direct heating, mowing, and vinegar in June reduced seed production by more than 90%. All treatments containing imazapic, pelargonic acid plus pendimethalin, fenoxaprop-p-ethyl, glufosinate, and glyphosate completely prevented stiltgrass seed production in the second year of treatment. Effective control of stiltgrass can be achieved during a 2-yr period with a variety of herbicides, including herbicides at one-fourth of the labeled dose, and through nonchemical treatments.
Competitive Interactions of Garlic Mustard (Alliaria petiolata) and Damesrocket (Hesperis matronalis)
Authors: Leicht-Young Stacey A. , Pavlovic Noel B. , Adams Jean V.
Published: March 2012

Competitive interactions between native plants and nonnative, invasive plant species have been extensively studied; however, within degraded landscapes, the effect of interspecific interactions among invasive plants is less explored. We investigated a competitive interaction between two sympatric, invasive mustard species that have similar life history strategies and growth forms: garlic mustard and damesrocket. Greenhouse experiments using a full range of reciprocal density ratios were conducted to investigate interspecific competition. Garlic mustard had a negative effect on the final biomass, number of leaves, and relative growth rate in height of damesrocket. Survival of damesrocket was not negatively affected by interspecific competition with garlic mustard; however, garlic mustard showed higher mortality because of intraspecific competition. These results indicated that although garlic mustard has been observed to be the dominant species in this landscape, it may not completely outcompete damesrocket in all situations. Studies of invasive species in competition are important in degraded landscapes because this is the common situation in many natural areas.
Nonchemical Methods for Paragrass (Urochloa mutica) Control
Authors: Chaudhari Sushila , Sellers Brent A. , Rockwood Stephen V. , Ferrell Jason A. , MacDonald Gregory E. , Kenworthy Kevin E.
Published: March 2012

Paragrass is a nonnative category I invasive species in central and south Florida. This perennial grass species outcompetes native vegetation and is capable of rapid spread by vegetative reproduction. Although glyphosate and imazapyr are effective herbicides for paragrass control, the use of herbicides in certain areas may be restricted because of application timing or environmental concerns. Therefore, our objectives were to examine the effect of water depth (saturated vs. flooded) after burning or cutting, and the effect of water depth and duration after simulated roller-chopping, on paragrass regrowth under controlled conditions. In the first study, paragrass plants were cut or burned with a propane burner to 1 cm (0.39 in) above the soil surface. Plants were either watered daily (control), or were subjected to one of two water treatments: water level at the soil surface (saturated) or flooded to a depth of 44 cm. Burned-saturated or burned-flooded plants had 92% less biomass 5 wk after treatment (WAT) than cut-saturated plants. Flooding resulted in plant death regardless of the plant treatment. In the second study, simulated roller-chopping was performed by cutting paragrass stolons into one-, two-, or three-node segments; planting them into flats; and subjecting them to water treatments for 3, 7, 14, 28, and 42 d. Burning, cutting, and roller-chopping could be useful to control paragrass if subsequent flooding is applied. Future research should focus on evaluating the response of these control techniques in natural areas where water depth can be managed.
Predicting the Occurrence of Downy Brome (Bromus tectorum) in Central Oregon
Authors: Lovtang Sara C. P. , Riegel Gregg M.
Published: March 2012

Where the nonnative annual grass downy brome proliferates, it has changed ecosystem processes, such as nutrient, energy, and water cycles; successional pathways; and fire regimes. The objective of this study was to develop a model that predicts the presence of downy brome in Central Oregon and to test whether high presence correlates with greater cover. Understory data from the U.S. Department of Agriculture (USDA) Forest Service's Current Vegetation Survey (CVS) database for the Deschutes National Forest, the Ochoco National Forest, and the Crooked River National Grassland were compiled, and the presence of downy brome was determined for 1,092 systematically located plots. Logistic regression techniques were used to develop models for predicting downy brome populations. For the landscape including the eastside of the Cascade Mountains to the northwestern edge of the Great Basin, the following were selected as the best predictors of downy brome: low average March precipitation, warm minimum May temperature, few total trees per acre, many western junipers per acre, and a short distance to nearest road. The concordance index = 0.92. Using the equation from logistic regression, a probability for downy brome infestation was calculated for each CVS plot. The plots were assigned to a plant association group (PAG), and the average probability was calculated for the PAGs in which the CVS plots were located. This method could be duplicated in other areas where vegetation inventories take place.
Biophysical Correlates with the Distribution of the Invasive Annual Red Brome (Bromus rubens) on a Mojave Desert Landscape
Authors: Abella Scott R. , Embrey Teague M. , Schmid Sarah M. , Prengaman Kathryn A.
Published: March 2012

Because of its ability to transform ecosystems by increasing the prevalence of fire, the invasive annual red brome is a priority exotic species for management in arid lands of the southwestern United States. By sampling red brome presence and 97 environmental (climatic, topographic, and soil) and native vegetation (e.g., perennial species richness) variables on 126 sites, we assessed biophysical correlates with red brome distribution on a 755,000-ha (1.9 million ac) Mojave Desert landscape. Brome occupied 55 of 126 (44%) 0.09-ha plots. The simplest models (i.e., those containing the fewest or most easily obtained variables) in multivariate (classification trees and nonparametric multiplicative regression) and univariate (χ2) models often portrayed red brome distribution as well, or nearly as well, as more complicated models containing more variables harder to obtain. The models varied, however, in their abilities for describing brome presence compared with absence. For example, a simple classification tree using only elevation, soil great group, parent material, and vegetation type improved estimates of brome presence for 55% of sites, absences for 87%, and overall for 73% of sites compared with a naïve model containing the observed frequency of brome in the data. Conversely, a more complicated model, including soil boron and sulfur, performed better for presences (96%) than for absences (73%; 83% overall). Results also showed variable support for two general postulates in invasive species science. Red brome distribution was not correlated with soil N, which is inconsistent with the supposition that nutrient-rich soils are more prone to invasion. Brome was correlated with native perennial species richness to support the postulate that exotic species abundance is correlated with species-rich habitats, but the correlation was weak (r= 0.38) and similar in strength to correlations with many other environmental variables. On this relatively low-elevation landscape, the areas currently most invaded by red brome include the higher elevations (> 777 m [2,549 ft]), limestone–sandstone soils, and burrobush and mixed perennial communities. Areas least inhabited by brome are the lowest elevations (< 491 m), gypsum soils, and creosotebush and saltbush communities.
Selective Control of Medusahead (Taeniatherum caput-medusae) in California Sagebrush Scrub using Low Rates of Glyphosate
Authors: Kyser Guy B. , Creech J. Earl , Zhang Jimin , DiTomaso Joseph M.
Published: March 2012

Although glyphosate is typically used as a nonselective herbicide, low rates have the potential to provide selective control of seedling annuals in the understory of established perennial plants. In a repeated experiment on two adjacent sites at a single location near Alturas, CA (2009 and 2010), we evaluated the efficacy of glyphosate at several different rates on medusahead and nontarget species in northern California sagebrush scrub. We applied glyphosate at 10 rates ranging from 0 to 709 g ae ha−1 (0 to 18 oz product acre−1) at three separate timings in each trial: mid-March (medusahead in early seedling stage), late April to early May (tillering), and late May to early June (boot to early head). Plots measured 3 m by 9 m (10 ft by 30 ft) and were arranged in randomized complete blocks with four replications for each rate and timing. We visually estimated vegetative cover for all dominant species in July before medusahead seed drop using three 1-m2 quadrats per plot. Medusahead cover declined with increasing rates of glyphosate, and the middle application timing (at tillering) was the most effective. In rate series regression models, we achieved 95% control of medusahead with 160 g ae ha−1 glyphosate in midseason 2009, compared with 463 g ae ha−1 in early season and 203 g ae ha−1 in late season. In 2010, we achieved 95% control with 348 g ae ha−1 in midseason, compared with > 709 g ae ha−1 in early season. Medusahead seed production reflected changes in cover, though individual plants tended to produce more seed at low densities. We attribute reduced control early in the season and poorer overall control in 2010 to greater tolerance of medusahead to glyphosate at lower temperatures. Treatment effects on big sagebrush, as indicated by shoot tip vigor, were minor, although the midseason timing caused a slight reduction in vigor. These results show that low rates of glyphosate (158 to 315 g ae ha−1) at a treatment timing corresponding to medusahead tillering can give economical and effective control of medusahead without long-term damage to big sagebrush.
Spread Dynamics of Perennial Pepperweed (Lepidium latifolium) in Two Seasonal Wetland Areas
Authors: Renz Mark J. , Steinmaus Scott J. , Gilmer David S. , DiTomaso Joseph M.
Published: March 2012

Perennial pepperweed is an invasive plant that is expanding rapidly in several plant communities in the western United States. In California, perennial pepperweed has aggressively invaded seasonal wetlands, resulting in degradation of habitat quality. We evaluated the rate and dynamics of population spread, assessed the effect of disturbance on spread, and determined the biotic and abiotic factors influencing the likelihood of invasion. The study was conducted at eight sites within two wetland regions of California. Results indicate that in undisturbed sites, spread was almost exclusively through vegetative expansion, and the average rate of spread was 0.85 m yr−1 from the leading edge. Spread in sites that were disked was more than three times greater than in undisturbed sites. While smaller infestations increased at a faster rate compared with larger populations, larger infestations accumulated more newly infested areas than smaller infestations from year to year. Stem density was consistently higher in the center of the infestations, with about 2.4 times more stems per square meter compared with the leading edge at the perimeter of the population. The invasion by perennial pepperweed was positively correlated with increased water availability but was negatively correlated with the cover of perennial and annual species. Thus, high cover of resident vegetation can have a suppressive effect on the rate of invasion, even in wetland ecosystems. On the basis of these results, we recommend that resident plant cover not be disturbed, especially in wet areas adjacent to areas currently infested with perennial pepperweed. For infested areas, management efforts should be prioritized to focus on controlling satellite populations as well as the leading edge of larger infestations first. This strategy could reduce the need for costly active restoration efforts by maximizing the probability of successful re-establishment of resident vegetation from the adjacent seedbank.
Integrated Management of Scotch Broom (Cytisus scoparius) Using Biological Control
Authors: Herrera-Reddy Angelica M. , Carruthers Raymond I. , Mills Nicholas J.
Published: March 2012

Integrated weed management strategies (IWM) are being advocated and employed to control invasive plants species. In this study, we compared three management strategies (biological control alone [BC], BC with fire [BC + F], and BC with mowing [BC + M]) to determine if physical controls reduce seed production by Scotch broom and interfere with the action of the biological control agent—the Scotch broom seed weevil. We measured seed production and seed predation by the weevil at both pod and plant scale, and seed bank density over two field seasons. We found no difference in the number of seeds per pod among management strategies. However, combining management strategies (BC + M and BC + F) resulted in significant reductions in pods per plant, mature seeds per plant, and seed bank density relative to biological control alone. We did not find differences among management strategies in number of weevils per pod or proportion of seeds predated by the weevil at either pod or whole-plant scale. However, combining management strategies (BC + M and BC + F) resulted in a significant reduction in healthy mature seeds per plant relative to biological control alone. Although both integrated strategies outperformed biological control alone in reducing seed production and the seed bank, with no statistical difference between them, we propose that short-rotation prescribed fire could prove to be a more effective strategy for long-term management of Scotch broom due to its potential for slightly greater depletion of the seed bank.
Match/mismatch between the Mytilus edulis larval supply and seston quality: effect on recruitment
Authors: Toupoint Nicolas , Gilmore-Solomon Lisandre , Bourque François , Myrand Bruno , Pernet Fabrice , Olivier Frédéric , Tremblay Réjean
Published: March 2012

We considered Cushing's match/mismatch theory in a heterotrophic environment and hypothesized that settlement and recruitment success in blue mussel are higher when the food supply is rich in polyunsaturated and essential fatty acids (PUFA/EFA). To test this hypothesis, we monitored larval development as well as fatty acid composition in trophic resources during two successive reproductive seasons. The decoupling we found between the presence of competent larvae in the water column and settlement rates strongly suggests that metamorphosis is delayed until conditions are suitable. In both years, the major mussel settlement peak was synchronized with a phytoplanktonic pulse rich in EFA, consisting of a large autotrophic bloom in 2007 and a short but substantial peak of picoeukaryotes in 2008. These results suggest a “trophic settlement trigger” that indirectly affects recruitment by strongly improving the settlement rate. Despite similar larval settlement rates during both years, the lower 2007 recruitment likely resulted from a mismatch with a high lipid‐quality trophic resource. The seasonal trophic conditions differed greatly between the two years, with fatty acids profiles reflecting heterotrophic plankton production in 2007 and mostly autotrophic production in 2008. In agreement with Cushing's theory, our results highlight a match/mismatch, related to the food lipid quality rather than food quantity. For the first time, we show that the recruitment in marine bivalves may be dependent on phytoplanktonic pulses characterized by high levels of PUFA.
Plant‐mediated and nonadditive effects of two global change drivers on an insect herbivore community
Authors: de Sassi Claudio , Lewis Owen T. , Tylianakis Jason M.
Published: March 2012

Warmer temperatures can alter the phenology and distribution of individual species. However, differences across species may blur community‐level phenological responses to climate or cause biotic homogenization by consistently favoring certain taxa. Additionally, the response of insect communities to climate will be subject to plant‐mediated effects, which may or may not overshadow the direct effect of rising temperatures on insects. Finally, recent evidence for the importance of interaction effects between global change drivers suggests that phenological responses of communities to climate may be altered by other drivers. We used a natural temperature gradient (generated by elevation and topology), combined with experimental nitrogen fertilization, to investigate the effects of elevated temperature and globally increasing anthropogenic nitrogen deposition on the structure and phenology of a seminatural grassland herbivore assemblage (lepidopteran insects).

We found that both drivers, alone and in combination, severely altered how the relative abundance and composition of species changed through time. Importantly, warmer temperatures were associated with biotic homogenization, such that herbivore assemblages in the warmest plots had more similar species composition than those in intermediate or cool plots. Changes in herbivore composition and abundance were largely mediated by changes in the plant community, with increased nonnative grass cover under high treatment levels being the strongest determinant of herbivore abundance. In addition to compositional changes, total herbivore biomass more than doubled under elevated nitrogen and increased more than fourfold with temperature, bearing important functional implications for herbivores as consumers and as a prey resource. The crucial role of nonnative plant dominance in mediating responses of herbivores to change, combined with the frequent nonadditive (positive and negative) effects of the two drivers, and the differential responses of species, highlight that understanding complex ecosystem responses will benefit from multifactor, multitrophic experiments at community scales or larger.
Experiences in Eliminating Steam Breakthrough & Providing Zonal Isolation in SAGD Wells
Authors: Brooks Robert T. , Tavakol Habib
Published: March 2012

For the last two decades major oil companies in Canada have been paying much attention to heavy oil which is an alternative unconventional reservoir (Canada and Venezuela have some of the largest bitumen deposits in the world). Main reasons for development could be the high price of oil, and improved technology to extract heavy oil, with a high recovery factor (up to 60% of the oil in place). Injecting steam is the most distinctive technique of heating up the formation rock and assisting in oil flow. Controlling steam injection and its distribution, and achieving economical recovery in an effective manner, has been a continuous mind-boggling issue for the heavy oil producers, and has been a great challenge.

High-temperature water and oil swellable packers have been developed to aid, and optimize, cyclic steam stimulation and Steam Assisted Gravity Drainage (SAGD) applications in heavy oil reservoirs. Simplicity is one of the great advantages of the swellable packers, which provide an ease of operation. The packer allows uniform or selective placement of steam along the entire length of horizontal section, and is designed to handle high temperature 575°F (302°C), and more than adequate differential pressures, associated with steam injection. Screens or slotted liners are run in hole to allow steam to be pumped in between the well pairs. Steam breakthrough, or diversion, has been experienced in numerous wells due to sand erosion and/or plugging of the slotted liners, which creates problems for continuous production. Swellable packers can be installed in conjunction with screens or slotted liner in order to distribute steam and provide zonal isolation. In the event of steam breakthrough, swellable packers can be deployed to isolate the affected zone(s). This intervention technique will assist in efficient continued production, elimination of sand production and steam breakthrough.

The technique of steam injection has been improving over the years, but still has room for refining of the processes. Some older wells have encountered with issues of steam channeling through the cemented casing & breaking out at the surface; which has been seen to create a threat to the environment. A horizontal well completed with slotted liner, or recently with specially designed type of screens, provides a far better method than perforated casing for injecting steam into the formation.

This paper presents solutions for SAGD wells with a unique technique for resolving wasted steam injection at the toe section of the well, and repair of steam breakthrough in production legs. Every operator is coming across new learning experience almost every day, although most of this information is proprietary, we are proposing a different solution path to overcome some of these issues.
Successful Techniques for Competently Abandoning Wells with Severe Casing Restrictions
Authors: Renting Deanne , Aparicio Tarcisio
Published: March 2012

Chevron has developed a number of new techniques for abandoning wells with severe parted casing, which have been successfully applied in an unconventional Californian reservoir. A number of wells have developed severe doglegs or parted casing. Such restrictions have prevented traditional workover techniques from reaching the reservoir to ensure a standard abandonment, referred to as ‘complex damage’. The first key learning is to maintain access to the reservoir as long as possible, by not pulling the equipment (tubing and packer) out of the wellbore when parted casing is suspected. In cases where it may not be possible to abandon the well after equipment is pulled from the well-bore, solidly cementing the equipment in the well may be a more robust abandonment technique than pulling the equipment and risking not being able to re-access the reservoir. When complex damage has developed, milling and explosive tools have been successfully applied to re-access the reservoir, run on tubing, wireline and coiled tubing. To evaluate the restrictions, diagnostics such as down-hole cameras are critical to develop and execute a successful abandonment plan. Using these techniques, Chevron abandoned several wells with complex damage in 2011.
Evaluation of CO2-EOR and Sequestration in Alaska West Sak Reservoir Using Four-Phase Simulation Model
Authors: Nourpour Aghbash Vahid , Ahmadi Mohabbat
Published: March 2012

Injection of CO2 into West Sak reservoir of Alaska was studied. The study was conducted with the objective to store CO2 and enhance the oil recovery. Due to low reservoir temperature, mixing of possible injected mixtures, including pure CO2 and HC-enriched CO2, and the in-place hydrocarbon will result in development of three hydrocarbon phases, gas, oil-rich and CO2-rich phases, at certain pressures encountered in reservoir. Commercially available simulators are incapable of appropriate identification of this new phase and using them will result in unrealistic results and wrong predictions.

A compositional EOS simulator, capable of handling up to four phases, including two HC liquid phases, was used. A three dimensional simplified model of the reservoir was built, based on reservoir core data, to study the oil displacement by various injected fluids including pure CO2. Sensitivity of the results to the relative permeability parameters of the second liquid phase was studied. Effect of using WAG with different water to gas ratios on the oil recovery and CO2 sequestration was also investigated. Various simulations runs resulting from combining different water-CO2 injection plans, well completion schemes, well spacing and production constraint were conducted to propose an injection-production strategy that can optimize the oil recovery and CO2 storage.

Results show that the second liquid phase significantly affects both breakthrough time and total oil recovery. The sensitivity analysis of relative permeability parameters shows its profound effect on the results, emphasizes the need to use accurately measured relative permeability data to produce accurate results.WAG scheme improves the sweep efficiency but decreases the amount of stored CO2.Within the range investigated, 880 -1240 ft, we found higher recovery rate for smaller well spacing but negligible change in ultimate recovery.

West Sak contains 7 to 9 billion barrels of original oil in place. Its high viscosity makes the primary recovery scheme inefficient. Although waterflooding was successful to a certain degree but CO2 injection can be a successful option to increase recovery and store considerable mass of CO2 that might be produced from coal-bed gasification in Alaska. Although CO2 cannot develop full miscibility with West Sak oil; however, it causes the oil to swell, oil viscosity to decrease, and recovery to increase.
Applying Method of Characteristics to Model the Flow of Compressible CO2 in Aquifers
Authors: Ghanbarnezhad Moghanloo Rouzbeh
Published: March 2012

This paper presents the first semi-analytic solution of two-phase two-component compressible flow in permeable media using method of characteristics (MOC). Analytical solutions are important as numerical simulations do not yield explicit expressions in terms of the model parameters. However, the previously developed MOC solutions rely on the incompressible fluid and rock assumptions that are rarely met in practice Furthermore, numerical simulations that provide the most comprehensive solutions to multiphase flow problems are computationally intensive. In this study, the method of characteristics (MOC) solution of the overall mass conservation equation of CO2 in two-phase two-component flow through permeable media is derived with no restriction on the compressibility of fluids and the rock.

A simulation approach is used to verify the derived analytical solutions. The simulation models consist of a vertical injection well and a producer located at the ends of a one-dimensional (1D) grid. The pace at which specific gas saturations propagate along the permeable medium are compared with the gas saturation profiles obtained when no compressibility is involved.

The results suggest that the velocity of a wave, which is associated with the transport of a certain mass of CO2 along the permeable medium, is a function of the gas saturation, compressibility of the rock and fluids, and the pressure gradient. The results reveal that the wave velocity will only be a function of the gas saturation and pressure gradient if the compressibility of the rock is negligible compared to that of CO2. Hence, the waves’ velocity will only depend on saturation, as is for an incompressible flow system, when changes in pressure gradient are minimal.

Thus, this paper explains how fast a compressible CO2 plume will travel along the aquifers length. In practice, the fate of the injected CO2 plume is essential to determine the storage capacity of aquifers and to evaluate the risk associated with the CO2 sequestration projects.
Evaluation of Electromagnetic Heating for Heavy Oil Recovery from Alaskan Reservoirs
Authors: Peraser V. , Patil S. L. , Khataniar S. , Dandekar A. Y. , Sonwalkar V. S.
Published: March 2012

Traditional thermal methods for heavy oil recovery involve use of steam to heat the wellbore and the reservoir. While the steam-based methods are widely in use and are generally successful, they also have high energy requirements, are not very efficient, and have environmental concerns. In addition, these methods are not readily applicable in Alaska, which is estimated to contain 18 to 27 billion barrels of heavy oil. Steam injection into the Alaskan heavy oil reservoirs is logistically complex, and is not practical due to the presence of a thick layer of permafrost. Hence, alternative methods to heat these reservoirs have to be considered.

The use of high frequency electromagnetic (EM) heating has been studied for a couple of decades now and is one of the approaches that has shown potential as a non-steam based thermal method for heavy oil recovery. Electromagnetic heating has several advantages over steam injection. The efficiency of steam injection is often limited by low formation permeability. Because EM energy is also absorbed by the formation, permeability of the formation is not as critical. Also, EM heating can be confined to the areas of interest and is easily controllable. This method seems to be ideally suited for the Alaskan heavy oil reservoirs as it does not entail steam injection through the permafrost.

In this study, use of EM heating for heavy oil recovery was examined mathematically by using engineering and physics-based computational modules. Using the fluid flow and heat transfer applications on a radial well model, the effects of EM power levels and frequency on heat penetration into the reservoir, temperature, and oil production were evaluated. The results showed that EM heating can increase heavy oil production rates by more than 200% using only moderate power levels, and continuous oil production could be sustained without any need to shut the well for heat dissipation or “soaking”. The use of EM heating appears to be a realistic approach towards developing Alaskan heavy oil reserves.
Using San Joaquin Valley Oil Fields as a Technology Test Bed To Mature Steamflood Technology
Authors: Stevenson J. K. , Behrens R. E. , Foote J. T. , Cassidy S. D.
Published: March 2012

Many heavy oil resources are giant, legacy-type assets that may take a century or longer to fully exploit. A key opportunity is to apply new technology and techniques to maximize recovery and economic performance. By selecting the right technology projects and managing them efficiently and effectively, we can reduce the cycle time to unlock this resource potential. Technology projects by their nature have large degrees of uncertainty that quite often cannot be resolved until tested in the field. Chevron has been using Kern River and other San Joaquin Valley oil fields as a technology development test bed for more than 50 years to unlock the resource potential of heavy oil.

The San Joaquin Valley is an ideal environment with a number of desirable attributes which facilitate Chevron’s field tests and pilots including:

• Location – accessible, onshore location with existing operations and major infrastructure

• Local Industry Capability – full spectrum of oil and gas service providers as well as highly capable personnel with extensive thermal recovery experience

• Resource Type and Size – large number of similar heavy oil assets which provides an economy of scale for applying new technology

• Risk – relatively low financial and Health, Environment & Safety (HES) exposure

• Heavy Oil Center of Excellence (HO CoE) - co-location of a corporate technology company unit and operating unit

• Ownership Structure – mostly 100% company owned and operated fields

The paper describes these factors and includes a number of technology examples that highlight considerations related to field testing and piloting in order to mature R&D projects.
Ensuring Better Well Stimulation in Unconventional Oil and Gas Formations by Optimizing Surfactant Additives
Authors: Xu Liang , Fu Qiang
Published: March 2012

Proper application of surfactant is critical to the completion process. It not only enhances initial production (IP), but helps sustain long-term production. Conventional wisdom suggests that the use of a nonemulsifying surfactant will work appropriately across most low-permeability reservoirs. Laboratory and field results, however, suggest that a weakly emulsifying surfactant is, in fact, far more efficient in solubilizing and mobilizing oil globules.

In this paper, an experimental toolbox and key strategies are presented for properly selecting surfactants for specific reservoir conditions. Dynamic surface tension, emulsion tendency, oil recovery, wettability and adsorption tests were all considered to select the proper surfactant for the case study. On the basis of these results, the field performance of both the nonemulsifying and weakly emulsifying surfactants are evaluated using production data from the Eagle Ford. The production-enhancement data appears to correspond well to lab results and strongly suggests that weakly emulsifying surfactants are superior at enhancing production.
Associative Data Modeling and Ant Colony Optimization Approach for Waterflood Analysis
Authors: Popa Andrei S. , Sivakumar Kailash , Cassidy Steve
Published: March 2012

Waterflooding is one of the oldest and most used techniques for increasing recovery in oil reservoirs. While successfully applied in sandstone formations, it presents certain challenges in tight, heterogeneous or unconventional reservoirs. Several strategies for pattern sizing, injection volumes and injection rates have been tested and implemented over the years by different operators in an attempt to optimize production and increase recovery. However, for unconventional reservoirs such as Diatomite formations, little information was documented on the success or failure of waterflood development scenarios. Using only high-level production and injection data, the objective of the study is to investigate the influence of pattern size on waterflood response and compare the various injection strategies executed in the field.

The paper presents two complementary approaches in an attempt to identify waterflood development best practices and optimization opportunities for the field. The first describes a relatively new clustering technology, Ants Colony Optimization (ACO), to find a sensible organization of “objects” into distinct groups, thus recognizing any patterns in the data. In our case, the “objects” are uniform grid blocks with distinct cumulative production and injection data. The algorithm utilizes a system of software ants, which mimics the actual way in which ants find the shortest path between their nest and food sources. The second approach involves an Associative Modeling technique, which works with entities that have a discrete independent existence, and their relationships are modeled as associations. Knowledge is inferred using an unconventional approach by comparing the normalized response of a random section area overlapped on different pattern sizes active in the field. Entities are expressed in terms of cumulative production and injection, and number of producers/injectors were then compared for these sections. The modeling contrasts different strategies, injection volumes and rates, used in different development areas.

This study introduces an innovative, fast, concise and simple approach for large data analysis and knowledge-extraction while demonstrating two intelligent approaches: ACO clustering and associative modeling. This approach can be easily adapted and applied to similar fields as a powerful method for comparing production/injection strategies on a large scale.
Field Scale Production Decline Characteristics During Gravity Drainage
Authors: Sahni Akshay , Beeson Dale , DiCarlo David A.
Published: March 2012

Gas or steam gravity drainage is a very efficient recovery mechanism. Field observations, laboratory studies and pore network modeling have pointed towards very low residual oil saturations and high recovery with gravity drainage. While work during the last three decades has focused on understanding the physics of three-phase flow, literature on field scale gravity drainage production decline characteristics is somewhat limited. Understanding field level production decline characteristics is important as it enables better production forecasting, resource estimation and reservoir management.

In this paper production data from two fields under gravity drainage is evaluated and it shows strong exponential decline characteristics. After an initial period of rapid decline, there is a period of lower decline for a long period of time. The paper relates field scale observations of gravity drainage to laboratory observations of gravity drainage in long cores. The laboratory experiments show similar behaviors where a period of initial rapid decline is followed by a long period of lower
 decline, resulting in very low remaining oil saturation in the gas invaded zone. The paper discusses physics of gravity drainage displacement and summarizes similarities and differences between field and laboratory observations.
Comparison of methane production by co-digesting fruit and vegetable waste with first stage and second stage anaerobic digester sludge from a two stage digester
Authors: Park Nathan D. , Thring Ronald W. , Helle Steve S.
Published: March 2012

Fruit and vegetable waste (FVW) was co-digested with first stage (FSS) and second stage anaerobic digester sludge (SSS) separately, over the course of 10 days, in batch reactors. Addition of FVW significantly increased the methane production in both sludges. After 10 days of digestion FSS + FVW produced 514 ± 57 L CH4 kg VS−1added compared with 392 ± 16 L CH4 for the SSS + FVW. The increased methane yield was most likely due to the higher inoculum substrate ratio of the FSS. The final VS and COD contents of the sewer sludge and FVW mixtures were not significantly different from the control values suggesting that all of the FVW added was degraded within 10 days. It is recommended that FVW be added to the first stage of the anaerobic digester in order to maximize methane generation.
Treatment of paper mill effluent using an anaerobic/aerobic hybrid side-stream Membrane Bioreactor
Authors: Sheldon M. S. , Zeelie P. J. , Edwards W.
Published: March 2012

This paper presents the design and operational performance data of an anaerobic/aerobic hybrid side-stream Membrane Bioreactor (MBR) process for treating paper mill effluent operated over a 6 month period. The paper mill effluent stream was characterized by a chemical oxygen demand (COD) range of between 1,600 and 4,400 mg/L and an average BOD of 2,400 mg/L. Despite large fluctuations in COD feed concentration, stable process performance was achieved. The anaerobic Expanded Granular Sludge Bed (EGSB) pre-treatment step effectively lowered the organic loading by 65 to 85%, thus lowering the MBR COD feed concentration to consistently below 750 mg/L. The overall MBR COD removal was consistent at an average of 96%, regardless of the effluent COD or changes in the hydraulic retention time (HRT) and organic loading rate (OLR). Combining a high-rate anaerobic pre-treatment EGSB with a Modified Ludzack–Ettinger (MLE) MBR process configuration produced a high quality permeate. Preliminary NF and RO results indicated an overall COD removal of around 97 and 98%, respectively.
Nine steps towards a better water meter management
Authors: Arregui F. J. , Soriano J. , Cabrera E. , Cobacho R.
Published: March 2012

The paper provides a comprehensive perspective of the critical aspects to be taken into account when planning the long-term management of water meters in a utility. In order to facilitate their quick understanding and practical implementation, they have been structured into nine steps. Ranging from an initial audit up to the final periodic meter replacement planning, these steps cover three aspects of the problem – field work, laboratory work and management tasks; and each one is developed in detail paying attention to the particular data needed and noting the practical outcome it will yield.
Performance indicators for wastewater treatment plants
Authors: Balmér P. , Hellström D.
Published: March 2012

The Swedish Water & Wastewater Association has operated a web-based system, VASS, for the collection and compilation of key data from the Swedish water utilities since 2003. The VASS system will now be expanded to include data on operation of individual wastewater treatment plants (WWTP). The objective is to provide performance indicators (PIs) for performance and economy and the use of resources such as energy, chemicals and manpower. A set of PIs has been developed that also includes explanatory factors to compensate for differences in the condition of operation between plants. This paper discusses the data required for the calculation of PI but also for explanatory factors, quality checks and for plant operation context. The discussion is based on the experiences from a test round with the participation of 24 WWTP.
Variability in nitrogen content of submerged aquatic vegetation: utility as an indicator of N dynamics within and among lakes
Authors: Blanchet Catherine , Maltais-Landry Gabriel , Maranger Roxane
Published: March 2012

Submerged aquatic vegetation (SAV) may serve as an integrative proxy of spatial and temporal nitrogen (N) availability in aquatic ecosystems as plants are physiologically capable of storing variable amounts of N. However, it is important to understand whether plant species behave similarly or differently within and among systems. We sampled different SAV species along a nutrient gradient at multiple sites within several lakes to determine variability in C:N ratios and % N content among species, among plants of the same species at a single site, among sites and among lakes. Species respond differently suggesting that not all plant types can be used universally as nutrient proxies. The greatest variability in % N and C:N ratios for Valliseneria americana was observed among lakes whereas for Elodea canadensis it was among sites within a lake and among plants within a site. This suggests that V. americana could be a particularly useful indicator of N availability at larger spatial scales (regional and within a large fluvial lake) but that E. canadensis was not a particularly useful proxy.