bluuebunny/crossref_metadata_2025 huggingface dataset:
Mitochondrial DNA corroborates the species distinctiveness of the Planalto (Thamnophilus pelzelni Hellmayr, 1924) and the Sooretama (T. ambiguus Swainson, 1825) Slaty-antshrikes (Passeriformes: Thamnophilidae)
Authors: Lacerda DR. , Marini MA. , Santos FR.
Published: February 2008

The Thamnophilus punctatus complex has been recently reviewed on the basis of morphological and vocal characters, and is divided in six different species. Two of the new species, although well defined on the basis of morphological differences, could not be unambiguously distinguished through their loudsongs. The Planalto Slaty-antshrike (Thamnophilus pelzelni) and the Sooretama Slaty-antshrike (T. ambiguus) are most easily distinguished by subtle and localized changes in plumage colors of males and females. In the present study we used sequences of the control region, Cytochrome b, and ND2 genes, of the mitochondrial DNA (mtDNA) to evaluate the levels of molecular differentiation between these two species. The mean pairwise distance between the two species was 3.8%, while it varied from 2.7% to 4.9% for each mtDNA region. Although extensive variation was also detected among haplotypes within species, especially for T. ambiguus, we suggest that the genetic divergence found between T. ambiguus and T. pelzelni is high enough to corroborate the separate species status of these two antbird taxa.
Comparative cytogenetic study in Muscidae flies
Authors: Parise-Maltempi PP. , Avancini RMP.
Published: February 2008

The chromosome modal number in Muscoidea Diptera is 2n = 12, including five pairs of autosomes and one sex chromosome pair. Nevertheless, some species with 2n = 10 chromosomes have been described, all of them from the Muscidae family. We analyzed the karyotype of some Muscidae species from different subfamilies and compared the obtained data with the karyotypes of some species of the families Calliphoridae and Sarcophagidae. Comparisons of these species with other Muscidae species revealed a considerable variation among their sex chromosomes. This variation in the length of the sex chromosomes suggests that parts of these chromosomes were lost or fused with autosomes. The constitutive heterochromatic regions and the nucleolar organizer regions (NORs) were also analyzed and some aspects about the relationship between these regions and the sex chromosomes are discussed.
O efeito do corticosteróide na prevenção da síndrome da embolia gordurosa após fratura de osso longo dos membros inferiores: revisão sistemática com meta-análise
Authors: Cavallazzi Rodrigo , Cavallazzi Antonio César
Published: February 2008

OBJETIVO: Analisar a evidência disponível sobre o efeito do corticosteróide na prevenção da síndrome da embolia gordurosa (SEG) após fratura de osso longo do membro inferior e/ou pélvis. MÉTODOS: Pesquisamos as bases de dados eletrônicas do Medline, Excerpta Medica, Cochrane Library, Literatura Latino-Americana e do Caribe em Ciências da Saúde e Scientific Electronic Library Online em março de 2007. Selecionamos estudos randomizados e controlados que compararam corticosteróide com placebo (ou cuidados de rotina) na prevenção da SEG após fratura de osso longo de membro inferior e/ou pélvis. Também revisamos as referências contidas nos estudos incluídos. RESULTADOS: Seis estudos foram incluídos. O risco relativo total de desenvolver SEG foi 0,16 (IC95%: 0,08-0,35) no grupo que recebeu corticosteróide em comparação com o grupo controle. O risco relativo total de desenvolver hipoxemia foi 0,34 (IC95%: 0,19-0,59) no grupo que recebeu corticosteróide em comparação com o grupo controle. CONCLUSÃO: A análise da evidência mostrou que o corticosteróide diminui o risco de SEG e hipoxemia após fratura de ossos longos de membro inferior.
Poluição atmosférica devida à queima de biomassa florestal e atendimentos de emergência por doença respiratória em Rio Branco, Brasil - Setembro, 2005
Authors: Mascarenhas Márcio Dênis Medeiros , Vieira Lúcia Costa , Lanzieri Tatiana Miranda , Leal Ana Paula Pinho Rodrigues , Duarte Alejandro Fonseca , Hatch Douglas Lloyd
Published: February 2008

A poluição atmosférica é um importante problema de saúde pública, principalmente na Amazônia e grandes cidades brasileiras. Em setembro de 2005, observou-se elevada concentração de fumaça em Rio Branco, Acre, devido às queimadas. Para avaliar a relação entre a concentração diária de particulate matter < 2,5 µm (PM2,5) e o número de atendimentos diários de emergência por doença respiratória (DR), desenvolveu-se estudo ecológico. A concentração de PM2,5 ultrapassou o limite de qualidade do ar durante 23 dias. Observou-se maior incidência de DR em crianças < 10 anos e correlação positiva entre a concentração de PM2,5 e atendimentos por asma.
Termoplastia brônquica: relato do primeiro tratamento endoscópico de asma na América Latina
Authors: Rubin Adalberto Sperb , Cardoso Paulo Francisco Guerreiro
Published: February 2008

A termoplastia brônquica é um novo procedimento broncoscópico que libera energia por radiofreqüência nas vias aéreas, com potencial redução da broncoconstrição causada pela contratura da musculatura lisa. Relatamos o caso de um homem de 48 anos, portador de asma persistente moderada, submetido à termoplastia brônquica. O tratamento aumentou o volume expiratório forçado no primeiro segundo, aumentou o número de dias livres de sintomas, reduziu o uso da medicação de resgate e melhorou o escore no questionário de Juniper Asthma Quality of Life Scale. A termoplastia brônquica foi bem tolerada e segura. Esta foi a primeira termoplastia brônquica na América Latina, com resultados estimulantes após 12 meses quanto ao seu potencial benefício em asmáticos pouco controlados.
Economic and Physical Optimization of Hydraulic Fracturing
Authors: Marongiu-Porcu M. , Economides M. J. , Holditch S. A.
Published: February 2008

Optimization has taken several different hues in all areas of engineering. Hydraulic fracturing, as applied to petroleum wells, has had its share. In the past, and before the maturing of high-permeability fracturing and the tip screen out techniques, this well stimulation procedure was limited to low-permeability reservoirs and unrestricted fracturing. In such cases, the fracture length would be an appropriate design optimization variable against an economic criterion, e.g., the Net Present Value (NPV). This involved the balancing of incremental future revenue against the cost of execution. Also interesting are parametric studies, allowing the variation of execution variables and the detection of differences in their respective design NPV. Such differences would be useful in decisions to measure a variable or stay within reasonable assumptions. The emergence of higher-permeability fracturing and the Unified Fracture Design (UFD) concept allowed two important notions. First, there is no difference between low and high-permeability reservoirs in terms of benefiting for fracturing. Just execution issues need to be resolved. Second, and more important, for any mass of proppant to be injected in any well, there exists only one fracture geometry that would maximize production. This geometry, consisting of length and propped width (with height as a parasitic variable) can be readily determined and, if placed, it will provide the maximum productivity index. All other configurations would result in lower productivity values. This is physical optimization.

In this paper we combine the two: the economic and physical. For each proppant mass we first optimize the fracture physically and then we apply the NPV criterion. We perform a series of parametric studies for a range of reservoirs and we use economic variables that differ in various parts of the world. We show how to determine the optimum fracture size. We then show how fracture treatments may be attractive in certain reservoirs in mature areas but not attractive elsewhere. We also show that for a diversified company, given the choice, few successful fractures in high-permeability reservoirs are far preferable to fracturing large numbers of wells in lower permeability fields, although the latter can be made economically attractive only through hydraulic fracturing.
A Novel Technique for Determining Screen Failure in Offshore Wells: A GOM Case History
Authors: Navaira G. , Hupp M. , Palisch T. , Renkes J.
Published: February 2008

Offshore completions in the Gulf of Mexico must typically address sand control. Our industry has made significant progress with respect to sand control equipment and implementation. However, even properly designed and executed completions are subject to mechanical failure, with the first indications often being production of solids into a common separation facility. In many offshore completions, particularly sub-sea or multi-zone completions, it is often difficult and expensive to determine which well or specific completion interval has failed, most times requiring production to be shut in for diagnosis. Not until that point can a remedy be evaluated.

One GOM producer engaged the services of a proppant supplier to determine whether a suite of proppants/gravel could be developed that could be uniquely identified and placed in each completion interval. In the event of proppant production to surface (mechanical failure), the surface samples would be analyzed to directly determine which interval had failed. The proppant needed to be non-radioactive yet identifiable with standard laboratory techniques.

The supplier subsequently developed a methodology whereby the proppant could be "tagged" with over 20 unique markers. This paper will discuss how the tagging agents are incorporated to become a permanent component of the pellet. The results of laboratory testing will be provided, verifying that the taggant does not materially affect the performance of the proppant.

In addition, the authors will review case histories where this new product was successfully placed in multi-zone frac pack completions in several deepwater GOM completions. The paper will also describe basic laboratory techniques used to successfully identify the source of proppant found in a surface choke subsequent to the frac. The economic savings provided by this novel approach will be presented, as well as other potential applications for this new product.
Reasons for Oil-Based Hydraulic Fracturing in Western Siberia
Authors: Elgassier M. M , Stolyarov S. M.
Published: February 2008

Both water- and oil-base fracturing have been used in West Siberian wells. However, the vast majority of these wells are hydraulically fracture stimulated using water-base fracturing fluids because for the same job size, the base fluid for water-base jobs is much cheaper than that of oil-base jobs. However, in some situations oil-base fracturing fluid may be the only option to improve well production performance.

This paper reviews oil-base hydraulic fracturing case histories in Western Siberia. Such treatments were used in Jurassic formations because of formation water sensitivity and in Cretaceous formations to control fracture height. Oil-base fracture stimulation treatments were specifically designed with base fluid that had lower than usual viscosity while maintaining its ability to carry proppant and withstand the high asphaltene and water content of Siberian crude and reduce the risk of fracture extension into water zones.

In many cases post-treatment incremental production of oil-base jobs was better than that of water-base jobs. Switching to oil-base fracturing fluids led to control of fracture geometry and eliminated the problem of formation sensitivity to the fracturing fluid. Much lower water cuts were also achieved post oil-base treatments because of fracture height containment. Excluding the cost of base fluid, oil-base treatments saved the operator, on average, 35% of the job cost. This is mainly due to reducing job size and lowering water cut.
Designing Well Fluids for the Ormen Lange Gas Project, Right on the Edge
Authors: Vickers Stephen , Hutton Alistair , Lund Arne , McKay Ian , Van Kranenburg Aart , Twycross Jean
Published: February 2008

The challenges in developing the Ormen Lange field were the harsh weather conditions, deep-water depth, subsea topography and sub-zero seabed temperatures. Due to environmental constraints and the selected sand face completion type, a water-based fluid system was required. This paper discusses the design of the fluids to give full hydrate inhibition, maximize breaker effectiveness, provide low overbalance, and reduce corrosion risk. An extensive research and development program was initiated that spanned over two years. The study included bridging and chemical component selection, brine evaluation, hydrate suppression measurement, elastomers compatibility, extensive breaker treatment studies, formation damage measurements using actual reservoir core and long term corrosion testing. An in-situ generating acid/enzyme breaker treatment deployed in the gravel pack carrier fluid was developed to optimise filtercake cleanup whilst providing a non-corrosive environment for the selected gravel pack screens and lower completion metallurgy. The basis of design and knowledge gained in the laboratory testing phase was transferred to the field and the first three wells of the initial development phase have been drilled and completed trouble-free. The resulting production rates have met expected targets proving low formation damage and an efficient cleanup was achieved.
Acoustic Surveillance of Production Impairment With Real-Time Completion Monitoring
Authors: Bakulin Andrey , Sidorov Alexander , Kashtan Boris , Jaaskelainen Mikko
Published: February 2008

Deepwater production is challenged by well underperformance problems that are hard to diagnose early on and expensive to deal with later. Problems are amplified by reliance on few complex wells with sophisticated sand control media. New downhole data is required for better understanding and prevention of completion and formation damage. We introduce Real-Time Completion Monitoring (RTCM), a new non-intrusive surveillance method for identifying impairment in sand-screened completions that utilizes acoustic signals sent via the fluid column. These signals are carried by tube waves that move borehole fluid back and forth radially across the completion layers. Such tube waves are capable of "instant" testing of the presence or absence of fluid communication across the completion and are sensitive to changes occurring in sand screens, gravel sand, perforations, and possibly reservoir. The part of the completion that has different impairment from its neighbors will carry tube waves with modified signatures (velocity, attenuation) and also would produce a reflection from the boundary where impairment changes. The method relies on permanent acoustic sensors performing acoustic soundings at the start of production and then repeating these measurements during the life of the well. Thus, it could be thought of as "miniaturized" 4D seismic and "permanent log" in an individual wellbore. In the meantime repeated conventional wireline measurements can be performed to assess the completion permeability.
Protecting Sand Control Screens Against Solids Plugging During Installation
Authors: McElfresh Paul , Welch John
Published: February 2008

In the completion of many offshore wells, the installation of sand control screens is a necessary and vital step to ensure optimum production rates. Current procedures usually involve displacing the solids laden drilling fluid from the well with a clear or weighted completion brines in order to minimize any solids that could potentially plug the filtration media of the screens. Other methods entail special sizing of the drilling fluid solids such that they will pass through the screens. This paper describes a new method to protect against solids plugging while installing sand screens in muds containing solids of any size distribution.

The protection takes the form of a film which is wrapped or coated on the outside of the woven mesh filtration medium of the screen. The film is protected from mechanical deterioration by the outside shroud of the screen itself. During the installation of the screen, the film prohibits invasion of solids into the filtration area by providing a physical barrier. Once the screens are in place, the film is removed through decomposition by the well bore fluids. The decomposition step is initiated by a material in the film which has a minimum solubility threshold near the temperature of the fluids at the bottom of the hole.

The treatment is engineered for wells requiring sand control up to about 200° F (93° C) using either water-or oil-based muds. The treatment also offers a method to maintain the maximum filtration efficiency by protecting from solids invasion during installation.
New Alternatives of Water Shutoff Treatments: Application of Water Sensitive Metastable Systems
Authors: Lakatos István , Lakatos-Szabó Julianna , Bódi Tibor , Vágó Árpád
Published: February 2008

The primary aim of the research project was to develop such chemical systems, which triggered by mixing with water will form the blocking phase. As a novelty, water sensitive homogeneous solutions and water external microemulsions were developed, which are stable until they are diluted with water forming thus stable macroemulsions. Transformation of different metastable systems to stable ones in reservoir space having high water saturation may radically restrict the water flow through their high viscosity and entrapment of the dispersed particles by the pores. As dispersed phases organic silicon compounds, tensides and natural crude oil fractions were tested. The transformation and structure of phases and size of particles were analyzed by photon correlation spectrometry, rheometry, while the flow properties were studied in natural sandstone systems.

The core studies confirmed that all metastable systems reduce the flow of water by 80-90% in water-saturated sandstone. Using chemical-free postflush the flow resistance remains substantial against water in case of silicones; meanwhile the permeability deterioration against oil or gas is negligible. The metastable systems are effective and single step disproportional permeability modifying fluids.

The metastable systems may offer an excellent opportunity for water shutoff in matured oil and gas fields and gas storage facilities. The unique properties of the techniques are that flow resistance may occur only in water saturated reservoir space and in case of technical failure; the flow barrier can be eliminated by oil and gas injection.
Novel Acid-Diversion Technique Increases Production in the Cantarell Field, Offshore Mexico
Authors: Garcia Benjamin , Soriano Eduardo , Chacon Wendy , Eoff Larry
Published: February 2008

Cantarell, which is an offshore complex of fields in the Bay of Campeche, is the most important complex in Mexico and is the second-largest producing field in the world. It is comprised of five fields, with the main pay zones consisting of highly fractured, vuggy carbonate formations from Jurassic, Cretaceous and Lower Paleocene geological ages. Matrix acidizing has always been the main stimulation process used to improve production from these carbonate reservoirs and this is especially the case now that this mature complex has reached its production peak.

As with all acidizing programs, a critical factor for success of the treatments is distribution of the acid between all productive zones. Since most producing wells are not homogeneous and contain layers of varying permeability, even distribution of the acid is a difficult task. In addition, the water saturation of the various zones has a major effect on the acid distribution. Since acid is an aqueous fluid, it will tend to predominantly enter the zones with the highest water saturation, in many cases resulting in increased water production. This brings with it the multitude of problems associated with high water production.

This paper will present the results of approximately 55 high permeability wells ranging from 1,000 to 6,000 md, which have been acidized using a novel acid diverter based on associative polymer technology (APT). This polymer inherently reduces the formation permeability to water with little or no effect on the permeability to hydrocarbon. Data from production logs from several of the treated wells will be presented, which show excellent oil production distribution along the perforated intervals. In addition, production logs will also be shown for wells acidized with other diverters, such as foams and in-situ crosslinked acid, which showed poorer results.
An Effective Technique to Reduce Bottomhole Friction Pressure During Hydraulic Fracturing Treatments
Authors: Smith Caleb G. , Khiat Smail , Albadraoui Dhafir
Published: February 2008

During a hydraulic fracturing treatment, it is imperative that adequate perforation channels link the wellbore to the formation. Bottomhole friction is a critical issue that can worsen as the result of poor perforation channels. Excessive bottomhole friction begets high treating pressures, which in turn can lead to premature screenouts when a well is hydraulically fractured.

The traditional method of perforating using through-tubing explosives has inherent disadvantages. These disadvantages can contribute to bottomhole friction in a multitude of ways. Drawbacks include the damage done to the near-wellbore area by the compaction force of the explosives and the debris left behind in the perforation channel. The small entry-hole diameter (EHD) made by through-tubing guns contributes to bottomhole friction by creating a large pressure drop across the perforations.

Hydraulically jetting with proppant (HJP) to create perforations entails pumping a combination of fluid and either proppant or sand down a string of jointed tubing or coiled tubing to create perforations. The slurry exits the jetting nozzle at a high velocity and creates a channel through the casing and cement and into the formation, in turn connecting the wellbore to the formation. The perforation depth is determined by the time the slurry is allowed to act in one area. Details such as perforation diameter, shot density, and phasing are determined by the specifications of the jetting tool.

This technical paper presents field data from a hydraulic fracturing treatment in which HJP was used to reduce bottomhole friction by 70%. This procedure creates superior connectivity between the wellbore and formation and leaves less near-wellbore damage. This benefit is significant in that it reduces the risk of premature screenouts when fracturing, as can often happen when perforating using through-tubing explosives.
Quantifying Skin Variation for Underbalanced Perforating
Authors: Zhan Lang , Kuchuk Fikri , Filas Jim , Kannan Dhani , Saeedi Jawaid , Van Petegem Charles
Published: February 2008

Reliable estimates of post perforation damage skin are important for designing remedial solutions and productivity enhancement operations. Underbalanced perforating (UBP), which is widely used in well completions, induces transient fluid flow that provides an opportunity for quantifying the formation parameters. However, the skin factor can rarely be estimated reliably from pressure data acquired in the current UBP operations if without flowing on surface in sufficient time. The reasons are that (a) the flow rate after an UBP continuously varies during the surge; (b) the skin factor may decrease substantially during the flow period because the mud cake, invaded filtrates, and particulate pore plugging are progressively removed at the vicinity of the sandface region; (c) the crashed layer of the perforation tunnels is cleaned up. The existing pressure transient analysis methods to determine the skin were almost exclusively developed with an assumption that the skin factor remains constant during a test. The conventional analyses do not represent the underlying physics of the surge flow and lead to loss of useful information from the skin variations. Few SPE papers have investigated the variable skin condition with a simple hyperbolic function for a constant rate drawdown. The constant rate drawdown assumption is not suitable for the UBP as the flow rate varies along with the changes in the skin (during clean-up) and the wellbore pressures.

We present a general formula to handle the skin variation resulting from the UBP and other surge flow tests. This formula extends the applications of a classic convolution algorithm to include variations in the skin and flow rates. New analytical solutions have been derived for both homogeneous and heterogeneous reservoirs based on the general convolution formula. The new solutions are applied to an integrated interpretation workflow to invert the skin variation as well as other formation parameters from pressure measurements. A field example, where both the skin and flow rate vary, demonstrates a successful application of the new solutions and interpretation methodology. The inferred skin variation allows a complete and detailed quantification of the perforation quality and cleanup efficiency. The results of this work enable the implement of better strategies for well completions and production optimization as well as correct inputs of nodal analysis.
Fracturing in Tight Gas Reservoirs: Application of SCAL Methods to Investigate Formation Damage Mechanisms
Authors: Bazin B. , Bekri S. , Vizika O. , Herzhaft B. , Aubry E.
Published: February 2008

Gas well productivity in tight reservoirs is greatly impeded by the fracturing fluid interactions with the formation. New simulators introduce formation damage mechanisms to calculate gas well productivity. However, equations describing formation damage must be supported by experimental data obtained in conditions representative of fracturing operations.

The purpose of this work is to derive the absolute permeability damage and multiphase flow upon return gas permeability after core invasion by a fracturing fluid by methods used in Special Core Analysis Laboratory (SCAL). The core permeability is in the microDarcy range. Experimental data of absolute permeability damage due to the fracturing fluid filtration and water sensitivity of this illitic sandstone as well as water saturation profiles measured by X-Ray in two phase flow experiments are interpreted. The methodology of interpretation provides the petrophysical data specific to the rock-fluid system: the absolute permeability, the relative permeability damage due to hysteresis, and the capillary pressure curve.

In addition, simulations are presented for the evaluation of the impact of various operational parameters like pressure draw-down on the gas productivity. It is shown that permeability hysteresis must be considered to explain the low gas recoveries at short term. On the long term, the natural clean-up is very slow. The results, derived from a real rock-fluid system, are used to provide recommendations for improving back flow procedures. This methodology can be applied to any case of damage due to the alteration of rock-fluid properties.
Interactions of Iron and Viscoelastic Surfactants: A New Formation-Damage Mechanism
Authors: Al-Nakhli A. R. , Nasr-El-Din H. A. , Al-Baiyat A. A.
Published: February 2008

Viscoelastic surfactant-based acids have been extensively used over the last few years in matrix and acid fracturing treatments. Two main types of viscoelastic surfactants have been used; amphoteric and cationic. Once the acid reacts with the carbonate formation and the pH increases above two and the concentrations of calcium and magnesium ions increases, these surfactants form a long rod shaped micelles. As a result, the viscosity of the solution increases significantly. This will result in better acid diversion in matrix acid treatments and deeper acid penetration in acid fracturing treatments.

Viscoelastic surfactant-based acids were used in more than 600 successful treatments. The results, however from one treatment was below expectations. Analysis of the live acid used indicated that this acid contained nearly 10,000 mg/l total iron. It was clear that there were some interactions between iron and the viscoelastic surfactant used. Therefore, this study was conduct to better understand interactions between iron and various types of viscoelastic surfactants. All tests were conducted on live acid that contained 20 wt% HCl, 4 to 6 vol% surfactant, and 0.3 vol% corrosion inhibitor. Ferric chloride was added to the live acids at various concentrations from 0 to 10,000 mg/l.

Compatibility tests indicated that there are strong chemical interactions between iron (III) and all types of viscoelastic surfactants examined. A gel like material was noted at a certain iron concentration. SEM analysis indicated that the gel-like material contained iron. Also analysis of the iron in the supernatant using ICP confirmed this result. The critical iron concentration was found to be a function of the surfactant type. Extensive lab testing indicating that there is interactions between iron and the amide and amine groups present in these surfactants. Corrosion inhibitors contain amine and amide groups, and they did affect the interactions between iron and viscoelastic surfactants. These interactions resulted in the formation of the gel-like material that can cause sever formation damage. This paper will discuss the results obtained and give recommendations to avoid the formation of such damaging material.
A New Gravel-Pack Approach Using Two Different Proppants in Long Horizontal Well Completions
Authors: de Magalhães J. V. M , Calderon A. , de Oliveira T. J. L. , Pires I. J. , Martins A. L.
Published: February 2008

The new scenario for offshore development in Brazil includes heavy oil fields in ultra deepwaters where 1000 m to 2000 m horizontal section wells are economical drives for field development. Such well geometry would assure effective reservoir drainage to maintain a reasonable productivity index of a heavy oil field.

In such wells, mainly in low frac gradient scenarios, it is known that the dynamic pressures during gravel-packing operations can easily overcome formation frac pressure. In order to accomplish this task and avoid formation damage, a new approach has been proposed. During the beta wave stage, where a large pressure growth is observed, a lightweight proppant would be pumped.

This article shows the computational simulations used to design this gravel-packing operation with two different proppants, in order to enable the completion of such wells.
Enhanced Oil Production Through a Combined Application of Gel Treatment and Surfactant Huff'n'Puff Technology
Authors: Wang Yefei , Bai Baojun , Gao Hengda , He Long , Zhao Fulin
Published: February 2008

Surfactant huff-puff for production wells has become a recent interest, especially for extremely heterogeneous reservoirs. However, injected surfactant will preferentially move into fractures in fractured reservoirs or higher permeability zones in unfractured reservoirs and will bypass much of the reservoir. In addition, the surfactant will be produced immediately after the production well resumes to production, so the soaking time is limited. This paper introduces a novel process which couples gel treatment and surfactant huff-puff in one EOR process in which surfactant solution is first injected into the production well, then followed by gel treatment. The proposed method has been applied for 10 production wells in a polymer flooding unit in Daqing oilfield. The best compatible surfactant and gel were screened out for the given reservoir conditions before the field application. The mechanisms of the proposed method were studied using core flooding experiments. The field application design process is presented and the application results have been analyzed. Application results show pressure drawdown test can be an important criterion to select candidate for the combined method.
A New Method To Characterize Scaling Damage From Pressure Measurements
Authors: Carageorgos T. , Marotti M. , Bredrikovetsky P.
Published: February 2008

Sulphate scaling with consequent deposit formation and wellbore damage is a well-known phenomenon that occurs during waterflooding, when mixing of incompatible injection and formation waters may result in sulphate salt precipitation and flow restriction. The reliable productivity decline prediction is based on mathematical modelling with well-known model coefficients. The sulphate scaling system contains two governing parameters: the kinetics coefficient characterising the velocity of chemical reaction and the formation damage coefficient showing how the permeability decreases due to salt precipitation.

Previous works have derived analytical-model-based method for determination of both coefficients from breakthrough concentration and pressure drop during laboratory coreflood on quasi steady state commingled flow of injected and formation waters, and also from just pressure drop measurements during two corefloods with two different ratios "formation water : seawater".

This paper extends the previous works, by sequence of two commingled injections of incompatible waters into the same core with two different ratios "formation water : seawater". Two different slopes of skin factor increase during two injections allow calculating the kinetics and formation damage coefficients in order to predict scaled-up well behaviour.
Formation Damage Evaluation From Non-Linear Skin Growth During Coreflooding
Authors: Bedrikovetsky P. , Vaz A. S. L. , Furtado C. , de Souza A. L. S.
Published: February 2008

Injectivity decline of oilfield injection wells is a widespread phenomenon during sea/produced water injection. The decline may result in significant cost increase of the waterflooding project. Reliable modelling-based prediction of injectivity index decrease is important for waterflood design as well as for the choice and preventive treatment of injected water. One of the reasons for well injectivity decline is permeability decrease due to rock matrix plugging by solid/liquid particles suspended in the injected water.

The mathematical model for deep bed filtration contains two empirical functions – the filtration coefficient and the formation damage coefficient. We consider the case where both coefficients are linear functions of retained particle concentration. In this case, the model is fully determined by four constants. These constants should be determined from laboratory coreflood tests by forcing water with particles to flow through core samples. A routine laboratory method determines the filtration coefficient from expensive and difficult particle concentration measurements of the core effluent; then the formation damage coefficient is determined from inexpensive and simple pressure drop measurements.

An alternative method uses pressure data at an intermediate point of the core, supplementing pressure measurements at the core inlet and outlet. The proposed method furnishes values for the four model parameters. The method is implemented in a simple and robust tool used in field conditions to characterise injectivity damage system and predict injection well behaviour.
XANES Spectroscopic Analysis of Phosphorus Speciation in Alum‐Amended Poultry Litter
Authors: Seiter Jennifer M. , Staats‐Borda Kristin E. , Ginder‐Vogel Matthew , Sparks Donald L.
Published: February 2008

Aluminum sulfate (alum; Al2(SO4)3·14H2O) is used as a chemical treatment of poultry litter to reduce the solubility and release of phosphate, thereby minimizing the impacts on adjacent aquatic ecosystems when poultry litter is land applied as a crop fertilizer. The objective of this study was to determine, through the use of X‐ray absorption near edge structure (XANES) spectroscopy and sequential extraction, how alum amendments alter P distribution and solid‐state speciation within the poultry litter system. Our results indicate that traditional sequential fractionation procedures may not account for variability in P speciation in heterogeneous animal manures. Analysis shows that NaOH‐extracted P in alum amended litters is predominantly organic (∼80%), whereas in the control samples, >60% of NaOH‐extracted P was inorganic P. Linear least squares fitting (LLSF) analysis of spectra collected of sequentially extracted litters showed that the P is present in inorganic (P sorbed on Al oxides, calcium phosphates) and organic forms (phytic acid, polyphosphates, and monoesters) in alum‐ and non‐alum–amended poultry litter. When determining land application rates of poultry litter, all of these compounds must be considered, especially organic P. Results of the sequential extractions in conjunction with LLSF suggest that no P species is completely removed by a single extractant. Rather, there is a continuum of removal as extractant strength increases. Overall, alum‐amended litters exhibited higher proportions of Al‐bound P species and phytic acid, whereas untreated samples contained Ca‐P minerals and organic P compounds. This study provides in situ information about P speciation in the poultry litter solid and about P availability in alum‐ and non‐alum–treated poultry litter that will dictate P losses to ground and surface water systems.
Silica Materials for Medical Applications
Authors: Vallet-Regí María , Balas Francisco
Published: February 2008

The two main applications of silica-based materials in medicine and biotechnology,i.e.for bone-repairing devices and for drug delivery systems, are presented and discussed. The influence of the structure and chemical composition in the final characteristics and properties of every silica-based material is also shown as a function of the both applications presented. The adequate combination of the synthesis techniques, template systems and additives leads to the development of materials that merge the bioactive behavior with the drug carrier ability. These systems could be excellent candidates as materials for the development of devices for tissue engineering.
Evaluation of Shifts in White‐Tailed Deer Winter Yards in the Adirondack Region of New York
Authors: HURST JEREMY E. , PORTER WILLIAM F.
Published: February 2008

ABSTRACT In the Adirondack region of northern New York, USA, severe weather and deep snow typically force white‐tailed deer (Odocoileus virginianus) to congregate in areas of dense coniferous cover and along watercourses at lower elevations. We examined 16 yards in the Adirondacks and explored the observation that deer have changed their movement behavior to incorporate residential communities within their wintering areas. We compared locations of deer herds in 2003 and 2004 to deer wintering areas mapped during the 1960s and 1970s. Deer were predominantly absent in 9 of 16 historical yards but were present in residential communities within the same drainage. Yarding areas to which deer shifted contained more residential, deciduous, and mixed cover than yards where no shift occurred, indicating that deer in residential areas were using conifer and mixed cover at a finer scale than deer in nonresidential areas. Smaller winter ranges and core areas of marked deer in a residential winter yard further imply greater concentration of resources available in these areas. Marked deer demonstrated flexibility in core winter range fidelity, a behavior that allows for more permanent shifts as habitat and food resources change or as new areas with appropriate resources are encountered. Our study suggests that low‐density residential areas in lowland conifer forests may provide an energetic advantage for deer during winter due to the assemblage of quality habitat interspersed with open areas and a variety of potential food sources in environments where movement is typically constrained by deep snow. Managers should consider the potential for changes in use of deer wintering areas prior to land conservation efforts and may need to adapt management strategies to reduce conflicts in communities occupied by deer during winter.
Importance of Native Seeds in White‐Winged Dove Diets Dominated by Agricultural Grains
Authors: PRUITT KENNETH D. , HEWITT DAVID G. , SILVY NOVA J. , BENN STEVE
Published: February 2008

ABSTRACT  Agricultural intensification is a key factor in the decline of many avian populations throughout the world, yet the exact mechanisms that contribute to these declines are relatively unresolved, especially for seed‐eating species. We tested the hypothesis that forage quality, particularly protein content, limits productivity in birds consuming diets dominated by agricultural grains and lacking in native forages. We used white‐winged doves (Zenaida asiatica) because columbids are highly granivorous and white‐winged doves have declined in areas dominated by grain agriculture. We randomly assigned 52 pairs of captive doves to 1 of 2 treatments: we fed one treatment sorghum (Sorghum bicolor) and the second sorghum plus native seeds (croton [Croton sp.] and native sunflower [Helianthus sp.]). Birds with access to native seeds fledged 123% more young per pair, with young weighing 32% more at fledging than those fed only sorghum. Doves with access to native seeds selected a diet consisting of 43% sorghum, 32% croton, and 25% sunflower. We conclude that agricultural grains, which typically have high metabolizable energy and low to moderate protein concentrations, are not sufficient for normal productivity of white‐winged doves. The lack of native forages with sufficient metabolizable energy and protein content may be a factor in the declining productivity of white‐winged doves in the lower Rio Grande Valley of Texas, USA, as well as other species in regions dominated by agriculture.
Application of a Bioeconomic Production Model to Improve Wildlife Management
Authors: RASHFORD BENJAMIN S. , DUGGER BRUCE D. , ADAMS RICHARD M.
Published: February 2008

ABSTRACT  Faced with limited budgets, wildlife managers need to determine the set of management activities that achieve management objectives at least cost, which requires using both ecological and economic principles to make management decisions. We used data from a biological simulation model of breeding waterfowl to embed biological response within an economic optimization model. Nonlinearity of the response function was attributable to density dependence and interactions between jointly applied management activities. We then used the bioeconomic model to solve a waterfowl manager's least‐cost problem. Model results demonstrated that 1) biological response and economic cost jointly determine the least‐cost management plan, 2) nonlinearity of the biological response function should be modeled explicitly to identify cost‐effective management plans, and 3) least‐cost management plans depend on the chosen population objective. We demonstrate how concepts from production economics can aid decision making in a wide range of applied wildlife management settings; however, though applied to waterfowl management, we did not intend to provide a robust prescription for waterfowl managers.
Accuracy, Precision, and Observation Rates of Global Positioning System Telemetry Collars
Authors: HANSEN MICHAEL C. , RIGGS ROBERT A.
Published: February 2008

ABSTRACT  We addressed concerns regarding performance of various Global Positioning System (GPS) collar configurations for describing habitat use by Rocky Mountain elk (Cervus elaphus) in rugged, forested terrain. We tested 8 GPS collars (Lotek Wireless, Newmarket, ON, Canada) in 4 different model and equipment configurations at 2 reference points (an open hilltop and a forested ravine) to determine habitat‐specific differences in performance among collar configurations. We then placed individual collars at 60 additional points that were stratified randomly among 4 canopy‐cover classes and 3 classes of available sky. All collars exhibited a locational bias of 4 m horizontally west and of 10 m vertically below a reference standard established by position‐averaging with a handheld receiver (Garmin 12MAP) calibrated at National Geodetic Survey benchmarks. The GPS collar models that were programmed for longer satellite‐acquisition times provided greater location precision than models that had been programmed for short acquisition times to preserve battery power. Canopy cover and available sky had a greater effect on collar location precision and observation rates than slope, slope position, aspect, conifer basal area, tree height, canopy depth, or elevation. Researchers should test collars at known reference points to confirm that location precision and rates of observation are adequate for their particular study objectives. Manufacturers of GPS collars should inform clients of their programming criteria for acquisition time so that customers can make informed decisions regarding trade‐offs between precision of locations, data quantity, and battery life.
Movements and Survival of Molt Migrant Canada Geese From Southern Michigan
Authors: LUUKKONEN DAVID R. , PRINCE HAROLD H. , MYKUT RICHARD C.
Published: February 2008

ABSTRACT We studied movements and survival of 250 female giant Canada geese (Branta canadensis maxima) marked during incubation with either satellite‐monitored platform transmitting terminals or very high frequency radiotransmitters at 27 capture areas in southern Michigan, USA, in 2000–2003. We destroyed nests of 168 radiomarked females by removing eggs after day 14 of incubation, and we left nests of 82 incubating hens undisturbed after capture and marking. Of females whose nests we experimentally destroyed, 80% subsequently migrated from breeding areas to molt remiges in Canada. Among 82 nests left undisturbed, 37 failed due to natural causes and 51% of those females departed. Migration incidence of birds that nested in urban parks was low (23%) compared with migration incidence of birds that nested in other classes of land use (87%). Departure of females from their breeding areas began during the second and third weeks of May, and most females departed during the last week of May and first week of June. Based on apparent molting locations of 227 marked geese, birds either made long‐distance migratory movements >900 km, between latitudes 51° and 64° N, or they remained on breeding areas. Molting locations for 132 migratory geese indicated 4 primary destinations in Canada: Western Ungava Peninsula and offshore islands, Cape Henrietta Maria, Northeast James Bay and offshore islands, and Belcher Islands, Hudson Bay, Canada. Following molt of remiges, Canada geese began to return to their former nesting areas from 20 August through 3 September, with 37% arriving on or before 15 September and 75% arriving on or before 1 October. Migration routes of geese returning to spring breeding areas were relatively indirect compared with direct routes taken to molting sites. Although overall survival from May through November was 0.81 (95% CI: 0.74–0.88), survival of migratory geese marked on breeding sites where birds could be hunted was low (0.60; 95% CI: 0.42–0.75) compared with high survival of birds that remained resident where hunting was restricted (0.93; 95% CI: 0.84–0.97). Nest destruction can induce molt migration, increase hunting mortality of geese returning from molting areas, and reduce human‐goose conflicts, but managers also should consider potential impacts of increasing numbers of molt migrants on populations of subarctic nesting Canada geese.