bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of lone pairs in the ferroelastic phase transition in the palmierite-type lead phosphate-arsenate solid solution
Authors: Angel Ross J. , Beirau Tobias , Mihailova Boriana , Paulmann C. , Bismayer Ulrich
Published: February 2012

The structural changes associated with the R-3m to C2/c ferroelastic phase transition in the solid solution Pb3(P1–x
As
x
O4)2 have been followed by Raman spectroscopy on samples with x = 0.00, 0.08, 0.37, 0.57, 0.65, 0.80, 1.00 over the temperature range 80–850 K. The high-temperature structural state of four intermediate samples with x = 0.37, 0.57, 0.65 and 0.80 was also studied by synchrotron single-crystal X-ray diffraction. The new results, in combination with previous data, reveal that Pb3(P1–x
As
x
O4)2 undergoes a complex sequence of transformation processes with several characteristic temperatures that can be clearly identified in addition to that of the ferroelastic phase transition at T
c. These structural changes are mainly driven by two phonon modes: vibrations of the Pb2 atoms (stereochemically active in the C2/c phase perpendicular to the layers characteristic of the palmierite-type structure), and rotational modes of the PO4 and AsO4 units within the plane of the layers. The former ensures coupling of the atomic displacements both within and between the layers, while the latter favours the coupling of the monoclinic species within the layers. With decreasing temperature, at T
4 ≫ T
c the Pb2 atoms are displaced from their special positions on the triad axis of the R-3m structure. At T
3 the size of the nanoclusters composed of coupled displacements of Pb2 atoms on the monoclinic pattern is sufficient to produce both macroscopic effects in all compositions (diffuse super-lattice intensities in the diffraction patterns, non-symmetry-breaking strain in the unit-cell parameters, a step in the C

p
curve) and microscopic effects in the broadening of the vibrational modes of the Pb2 atoms. The temperature interval between T
3 and T
4 is considerably smaller for the intermediate compositions than for the end-members indicating that the chemical disorder on the tetrahedral site facilitates the condensation of monoclinic species, probably by smearing the potential barrier between different monoclinic orientational states. At T
2 < T
3, but still above T
c, the AsO4 tetrahedra undergo monoclinic deformation in order to better coordinate the adjacent displaced Pb2 atoms, while the geometry of the PO4 tetrahedra remains unchanged down to T
c (and for As-rich compositions, slightly below T
c). At T
c the ordered Pb2 displacements and rotated tetrahedra drive a displacement of the Pb1 atoms from their trigonal (paraelastic) positions and long-range-ordered ferroelastic domains are formed. However, for all compounds, residual disorder of the Pb2 displacements persists below T
c to a further characteristic temperature T
1 at which the displacements of all types of atoms become completely ordered on all length scales.
Sportolók occult lágyéksérve
Authors: Bátorfi József , Simon Éva , Parti Krisztina , Horváth Alexandra , Bajsz András , Horváth Tibor
Published: February 2012

Absztrakt

Bevezetés: A sportolók occult lágyéksérve külön entitású kórképet alkot, és része az irodalomban PIPS (pubic inguinal pain syndrome) néven ismert tünetegyüttesnek. A lágyéktáji fájdalom okainak feltárása nem könnyű feladat, több betegséget és szakterületet érinthet. Anyag és módszerek: Saját megfigyelésünkben occult lágyéksérv gyanúja miatt 14 esetben döntöttünk laparoscopos diagnosztika mellett. Valamennyi sportolónak (közöttük 11 futballista) jellemző panasza volt: a suprapubicus fájdalom pihenésre elmúlt, de edzésre, sportolásra újrakezdődött. A fizikális vizsgálat sérvesedést nem mutatott. A régió ultrahangvizsgálata 12 esetben hasprésre a hátsó hasfalon protrusiót jelzett. A laparoscopos diagnosztika valamennyi esetben pozitív volt: 13 medialis és 1 femoralis sérvet találtunk, amelyeket a laparoscopos diagnosztika folytatásaként transabdominalis praeperitonealis hernioplasztikával rekonstruáltunk. Eredmények: Szövődményünk nem volt, betegeink 2–3 nappal a műtét után emissióra kerültek. A fokozatos, panaszt nem okozó terhelést 7–10 nappal későbbre tanácsoltuk. A versenyszerű sportolásba valamennyi operáltunk 4–6 hét múlva sikerrel visszatért. Következtetés: A sportolók lágyéktáji fájdalmának egyik oka lehet az occult, fizikális vizsgálattal nem diagnosztizálható lágyéksérv, ami laparoscopos diagnosztikával felfedhető, és egyben transabdominalis praeperitonealis hernioplasztikával eredményesen gyógyítható.
Effect of the linear velocity during the melt spinning process on shape memory transformation of Ni-Ti ribbons
Authors: Nuñez-Mendoza E. , López Cuellar E. , Benicio de Castro Walman , López Walle B.
Published: February 2012

The usual process to produce NiTi shape memory alloys is vacuum induction melting (VIM). Currently a new alternative process to produce NiTi shape memory alloys by rapid solidification structures called Melt Spinning has been studied. In this work, results of ribbons with a chemical composition Ti-55.2 Ni (wt %) alloy prepared by this method are presented. The ribbons are prepared at two different linear velocities: 30 m/s and 50 m/s. After that, samples are heat treated at 350 °C during 1 hour. The alloys are characterized by Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC) and X-Ray Diffraction. According to the cycled DSC test, transformation peaks are associated with the B2→R→B19´ transformation during cooling and B19´→R→B2 during heating, showing transformation in multi-peaks. The martensite B19´ start (Ms) is varying from 35 to 39°C and the martensite finish (Mf) from 15 to 21°C, 42-47°C for austenite B2 start (As) and 65-69°C for austenite finish (Af) approximately. All analyzed ribbons show very similar values of transformation hysteresis temperatures at 50% of transformation of around 28°C. In order to change solidification rate, linear velocity is varied during the melt spinning process. Results indicate that linear velocity affects directly the temperature of transformation. When the linear velocity is increasing, crystallographic Ti-rich precipitates are developed, but dendritic growth disappears, changing the microstructure and decreasing these transformation temperatures. Then changes in linear velocity can dramatically affect shape memory properties, and in this case a velocity of 50 m/s produces a more homogenous alloy.
Leishmanicidal activity and cytotoxicity of compounds from two Annonacea species cultivated in Northeastern Brazil
Authors: Vila-Nova Nadja Soares , Morais Selen Maia de , Falcão Maria José Cajazeiras , Machado Lyeghyna Karla Andrade , Beviláqua Cláudia Maria Leal , Costa Igor Rafael Sousa , Brasil Nilce Viana Gramosa Pompeu de Sousa , Andrade Júnior Heitor Franco de
Published: February 2012

INTRODUCTION: Visceral leishmaniasis is endemic in 88 countries, with a total of 12 million people infected and 350 million at risk. In the search for new leishmanicidal agents, alkaloids and acetogenins isolated from leaves of Annona squamosa and seeds of Annona muricata were tested against promastigote and amastigote forms of Leishmania chagasi. METHODS: Methanol-water (80:20) extracts of A. squamosa leaves and A. muricata seeds were extracted with 10% phosphoric acid and organic solvents to obtain the alkaloid and acetogenin-rich extracts. These extracts were chromatographed on a silica gel column and eluted with a mixture of several solvents in crescent order of polarity. The compounds were identified by spectroscopic analysis. The isolated compounds were tested against Leishmania chagasi, which is responsible for American visceral leishmaniasis, using the MTT test assay. The cytotoxicity assay was evaluated for all isolated compounds, and for this assay, RAW 264.7 cells were used. RESULTS: O-methylarmepavine, a benzylisoquinolinic alkaloid, and a C37 trihydroxy adjacent bistetrahydrofuran acetogenin were isolated from A. squamosa, while two acetogenins, annonacinone and corossolone, were isolated from A. muricata. Against promastigotes, the alkaloid showed an IC50 of 23.3 µg/mL, and the acetogenins showed an IC50 ranging from 25.9 to 37.6 µg/mL; in the amastigote assay, the IC50 values ranged from 13.5 to 28.7 µg/mL. The cytotoxicity assay showed results ranging from 43.5 to 79.9 µg/mL. CONCLUSIONS: These results characterize A. squamosa and A. muricata as potential sources of leishmanicidal agents. Plants from Annonaceae are rich sources of natural compounds and an important tool in the search for new leishmanicidal therapies.
Species distribution and in vitro fluconazole susceptibility of clinical Candida isolates in a Brazilian tertiary-care hospital over a 3-year period
Authors: Furlaneto Márcia Cristina , Rota Juliana Frasnelli , Quesada Regina Mariuza Borsato , Furlaneto-Maia Luciana , Rodrigues Renne , Oda Silas , Oliveira Marcelo Tempesta de , Serpa Rosana , França Emanuele Júlio Galvão de
Published: February 2012

INTRODUCTION: In this study, we aimed at identifying Candida isolates obtained from blood, urine, tracheal secretion, and nail/skin lesions from cases attended at the Hospital Universitário de Londrina over a 3-year period and at evaluating fluconazole susceptibilities of the isolates. METHODS: Candida isolates were identified by polymerase chain reaction (PCR) using species-specific forward primers. The in vitro fluconazole susceptibility test was performed according to EUCAST-AFST reference procedure. RESULTS: Isolates were obtained from urine (53.4%), blood cultures (19.2%), tracheal secretion (17.8%), and nail/skin lesions (9.6%). When urine samples were considered, prevalence was similar in women (45.5%) and in men (54.5%) and was high in the age group >61 years than that in younger ones. For blood samples, prevalence was high in neonates (35%) and advanced ages (22.5%). For nail and skin samples, prevalence was higher in women (71.4%) than in men (28.6%). Candida albicans was the most frequently isolated in the hospital, but Candida species other than C. albicans accounted for 64% of isolates, including predominantly Candida tropicalis (33.2%) and Candida parapsilosis (19.2%). The trend for non-albicans Candida as the predominant species was noted from all clinical specimens, except from urine samples. All Candida isolates were considered susceptible in vitro to fluconazole with the exception of isolates belonging to the intrinsically less-susceptible species C. glabrata. CONCLUSIONS: Non-albicans Candida species were more frequently isolated in the hospital. Fluconazole resistance was a rare finding in our study.
The impact of leprosy on health-related quality of life
Authors: Lustosa Anselmo Alves , Nogueira Lídya Tolstenko , Pedrosa José Ivo dos Santos , Teles João Batista Mendes , Campelo Viriato
Published: February 2012

INTRODUCTION: Leprosy is a potentially disabling infectious disease that evolves into emotional issues due to the prejudice that persists about the illness. The endemic has declined substantially with multidrug therapy (MDT) in the 80's; however, new demands associated with the reduction of stigma and the improvement of the affected people's quality of life have emerged. In Brazil, leprosy is still a public health problem. Piauí is the second state in the Northeast in prevalence and detection, and Teresina is a hyperendemic city. This study aimed to analyze the health-related quality of life (HRQoL) of people in treatment for leprosy in Teresina/PI. METHODS: An observational study was conducted using the SF-36 (a specific questionnaire for assessing quality of life), which sought the determinants of poor quality of life among people with leprosy, outlining the sociodemographic, clinical, and epidemiological characteristics of the 107 patients interviewed. RESULTS: The correlations between the variables showed five determinants of HRQoL: late diagnosis, multibacillary forms, reactions, disability diagnosis grade II, and prejudice. The profile of the participants showed that leprosy still affects the lower social classes in historically endemic areas, causing high percentages of secondary injuries that compromise the work capacity and quality of life of the affected people, perpetuating the stigma associated with the disease. CONCLUSIONS: The study reinforces the need to implement more effective strategies of disease control, due to the development of severe and disabling forms of leprosy is directly related to poor HRQoL in the same cured patient.
Rapid detection of Van genes in rectal swabs by real time PCR in Southern Brazil
Authors: Cantarelli Vlademir , Cavalcante Bianca , Pilger Diogo André , Souza Fabiana , Dias Cícero Gomes , Brodt Teresa , Cantarelli Maritza , Secchi Carina , d'Azevedo Pedro Alves
Published: February 2012

INTRODUCTION: Laboratory-based surveillance is an important component in the control of vancomycin resistant enterococci (VRE). METHODS: The study aimed to evaluate real-time polymerase chain reaction (RT-PCR) (genes vanA-vanB) for VRE detection on 115 swabs from patients included in a surveillance program. RESULTS: Sensitivity of RT-PCR was similar to primary culture (75% and 79.5%, respectively) when compared to broth enriched culture, whereas specificity was 83.1%. CONCLUSIONS: RT-PCR provides same day results, however it showed low sensitivity for VRE detection.
Bacillary angiomatosis in HIV-positive patient from Northeastern Brazil: a case report
Authors: Justa Renata Félix da , Carneiro Adriana Banhos , Rodrigues Jorge Luiz Nobre , Cavalcante Andréia , Girão Evelyne Santana , Silva Paulo Sergio , Valença Júnior José Telmo , Menezes Dalgimar Beserra de , Leitão Terezinha do Menino Jesus Silva
Published: February 2012

It is a report of disseminated bacillary angiomatosis (BA) in a 23-year-old female patient, who is HIV-positive and with fever, weight loss, hepatomegaly, ascites, and papular-nodular skin lesions. The clinical and diagnostic aspects involved in the case were discussed. Bacillary angiomatosis must always be considered in the diagnosis of febrile cutaneous manifestations in AIDS.
Educação a distância: uma abordagem metodológica e didática a partir dos ambientes virtuais
Authors: Amarilla Filho Porfírio
Published: February 2012

Este artigo aborda a Educação a Distância a partir da influência dos ambientes virtuais. Suas exigências, suas relações técnico-pedagógicas necessárias e os pressupostos necessários aos processos ensino e aprendizagem a partir da utilização desses ambientes. A partir de uma análise do conceito de ambiente virtual e das implicações que sua influência impõe ao processo de ensino-aprendizagem, procura-se analisar algumas implicações metodológicas e didáticas aos projetos educacionais dessa natureza aplicados a essa modalidade de ensino a partir desses ambientes. Para isso, propõe-se uma reflexão sobre o conceito de Educação a Distância, a partir da compreensão dos domínios da educação, do professor e do aluno, tendo como fundamento os desafios que essa nova tecnologia apresenta a essa modalidade de ensino.
O complexo da educação em Lukács: uma análise à luz das categorias trabalho e reprodução social
Authors: Lima Marteana Ferreira de , Jimenez Susana Vasconcelos
Published: February 2012

O artigo discute a educação em Lukács, a partir de sua Ontologia do Ser Social. Prioritariamente, destaca os elementos que assinalam o lugar da educação no processo de reprodução social, em cuja dinâmica esta manteria, com o trabalho, uma relação de dependência ontológica e autonomia relativa. Explicita que, se, em sentido lato, a educação é um complexo universal, empenhado em efetivar a apropriação, por parte dos indivíduos, das objetivações constituintes do gênero humano, esta não paira sobre a totalidade social, vinculando-se, em sentido estrito, às necessidades da sociedade de classe. Por esse prisma, a análise lukacsiana permite concluir que o complexo da educação, conquanto impelido a manter o sistema de acumulação privada e a exploração do homem pelo homem sob o capital, pode constituir-se em espaço para objetivação de posições teleológicas voltadas à emancipação humana.
Height‐growth response to climatic changes differs among populations of Douglas‐fir: a novel analysis of historic data
Authors: Leites Laura P. , Robinson Andrew P. , Rehfeldt Gerald E. , Marshall John D. , Crookston Nicholas L.
Published: February 2012

Projected climate change will affect existing forests, as substantial changes are predicted to occur during their life spans. Species that have ample intraspecific genetic differentiation, such as Douglas‐fir (Pseudotsuga menziesii(Mirb.) Franco), are expected to display population‐specific growth responses to climate change. Using a mixed‐effects modeling approach, we describe three‐year height (HT) growth response to changes in climate of interior Douglas‐fir populations. We incorporate climate information at the population level, yielding a model that is specific to both species and population. We use data from provenance tests from previous studies that comprised 236 populations from Idaho, Montana, and eastern Washington, USA. The most sensitive indicator of climate was the mean temperature of the coldest month. Population maximum HT and HT growth response to changes in climate were dependent on seed source climate. All populations had optimum HT growth when transferred to climates with warmer winters; those originating in sites with the warmest winters were taller across sites and had highest HT growth at transfer distances closest to zero; those from colder climates were shortest and had optimum HT growth when transferred the farthest. Although this differential response damped the height growth differences among populations, cold‐climate populations still achieved their maximum growth at lower temperatures than warm‐climate populations. The results highlight the relevance of understanding climate change impacts at the population level, particularly in a species with ample genetic variation among populations.
North American vegetation model for land‐use planning in a changing climate: a solution to large classification problems
Authors: Rehfeldt Gerald E. , Crookston Nicholas L. , Sáenz-Romero Cuauhtémoc , Campbell Elizabeth M.
Published: February 2012

Data points intensively sampling 46 North American biomes were used to predict the geographic distribution of biomes from climate variables using the Random Forests classification tree. Techniques were incorporated to accommodate a large number of classes and to predict the future occurrence of climates beyond the contemporary climatic range of the biomes. Errors of prediction from the statistical model averaged 3.7%, but for individual biomes, ranged from 0% to 21.5%. In validating the ability of the model to identify climates without analogs, 78% of 1528 locations outside North America and 81% of land area of the Caribbean Islands were predicted to have no analogs among the 46 biomes. Biome climates were projected into the future according to low and high greenhouse gas emission scenarios of three General Circulation Models for three periods, the decades surrounding 2030, 2060, and 2090. Prominent in the projections were (1) expansion of climates suitable for the tropical dry deciduous forests of Mexico, (2) expansion of climates typifying desertscrub biomes of western USA and northern Mexico, (3) stability of climates typifying the evergreen–deciduous forests of eastern USA, and (4) northward expansion of climates suited to temperate forests, Great Plains grasslands, and montane forests to the detriment of taiga and tundra climates. Maps indicating either poor agreement among projections or climates without contemporary analogs identify geographic areas where land management programs would be most equivocal. Concentrating efforts and resources where projections are more certain can assure land managers a greater likelihood of success.
The Affective and Cognitive Dimensions of Health Anxiety Are Associated With Different Orientations to Health Threat
Authors: Fergus Thomas A. , Valentiner David P.
Published: February 2012

Using a sample of medically healthy college students (N = 412), this study examined whether the two core dimensions of health anxiety share differential relations with orientations (approach and avoidance) to health threat. These two dimensions are an affective dimension marked by health worry and a cognitive dimension marked by disease conviction. Using a scenario-based measure that depicted potential health threats, the tendency to respond to such threats using safety behaviors that paralleled either approach or avoidance behavior was assessed. As predicted, zero-order and partial correlation analyses revealed that approach-based safety behaviors were especially relevant to the affective dimension of health anxiety and avoidance-based safety behaviors were especially relevant to the cognitive dimension of health anxiety. Conceptual and therapeutic implications are discussed.
Clinical Interventions for Technology-Based Problems: Excessive Internet and Video Game Use
Authors: King Daniel L. , Delfabbro Paul H. , Griffiths Mark D.
Published: February 2012

Psychological problems arising from excessive use of digital technologies, particularly in relation to the Internet and video games, are of growing clinical concern. Although there is no consensus whether technology-based problems constitute primary psychopathologies that should be recognized as clinical disorders, a significant number of problem users have used clinical treatment services. There is therefore a growing need for the mental health community to be aware of available clinical treatments for technology-based problem behaviors and the efficacy of these treatments. This article presents an overview of the prevalence of technology-based problems in Eastern and Western countries and the known cognitive-behavioral dimensions of problematic technology use. We also consider issues related to the assessment of technology-based problems, and critically review clinical treatments for technology-based problems.
Can Positive Thinking Reduce Negative Affect? A Test of Potential Mediating Mechanisms
Authors: Lightsey Owen Richard , Johnson Edward , Freeman Paul
Published: February 2012

Trait negative affect has emerged as a fundamental psychological dimension that can undermine mental health and well-being. Although recent evidence indicates that negative affect often declines over time, the malleable psychological mechanisms that predict these declines are not yet fully understood. The authors tested whether positive automatic thoughts (PATs) predicted negative affect through a positive relationship with self-esteem and hence an inverse relationship with negative automatic thoughts. Measures of these constructs were administered to 161 undergraduates. Consistent with theory and hypotheses, self-esteem and negative thoughts fully mediated the relationship between PATs and trait negative affect: PATs predicted higher self-esteem, which predicted less frequent negative thoughts. Negative thoughts directly predicted negative affect. The cross-sectional structural equation model accounted for 65% of the variance in negative affect. An alternative model in which self-esteem was construed as predicting PATs, and hence negative thoughts and negative affect, was not supported.
Between Mind and Brain:Final and Efficient Causation in Relation to Neuroplasticity
Authors: Hassert Derrick L.
Published: February 2012

Reductionism is usually taken for granted in many areas of science, neuroscience and psychology being no exceptions. It is often assumed as scientific orthodoxy that human behavior can be reduced to “what the brain does” without recourse to a consideration of cognition. Although many philosophers and ethicists may seek to reduce or eliminate the concept of mind, other philosophers and ethicists have continually pointed out the logical inconsistencies of such an approach. Via a discussion of efficient and final causes in Aristotelian philosophy, I seek to argue that the understanding of human beings as rational and social creatures has guided and should continue to guide our approach to the care and treatment of the mentally ill. Observations concerning rational behavior and cognition, by necessity, have provided the benchmarks by which clinicians evaluate the effectiveness of somatic/pharmacological or psychological/ behavioral interventions: Eliminative reductionism is inappropriate in this area. In approaching issues pertaining to the relationship between human cognitive functioning and neural functioning, the distinction between capacity and vehicle will be used. However, the fact that mental and behavioral functioning can alter neuronal functioning (and vice versa) necessitates that those working with the mentally ill need to know both the efficient causes—the vehicles of certain capacities—and the role of the capacities themselves and how they relate to possible final causes in giving explanations for behavior. These issues become more significant when considering the ethics of treatment choice for those with mental disorders.
Mechanical Efficiency Algorithm Solves Drilling Problems in Areas of Limited/Inaccurate Offset Data
Authors: Purwanto Arifin , Ibrahim Hani , Saheta Vishal , Bits Smith
Published: February 2012

A well plan is essentially a decision-making roadmap for choosing equipment required for drilling the required wellbore. The operator's ability to properly assess offset drilling data and key lithology factors to match available BHA tools and procedures plays a large role in determining project success. Accordingly, the software support systems utilized to interpret and extrapolate data have a direct impact on the ability of drilling engineers to optimize operations.

Historically, most well plans were assembled using data from offset wells and prior experience. However in most cases, a rudimentary analysis could not produce a comprehensive picture of the complex, interdisciplinary downhole dynamics that affect drilling performance, especially in the case of limited or missing offset data. Even when reliable data was available, a one-dimensional analysis has failed to completely exploit the available informational value from offset wells. This has forced engineers to be more conservative when designing wells and include more contingencies. The result is operators are drilling in a reactive manner, which often led to decisions resulting in performance degradation rather than optimization.

To solve the problem and improve drilling performance in areas of limited/inaccurate offset data, engineers have developed a Mechanical Efficiency Ratio optimization system (MER) that accurately measures the BHA's use of available energy. The modeling tool was tested in several applications and accurately predicted performance including ROP, footage capabilities and dull bit condition. The tool used data and evaluation of rig capabilities, bit/BHA performance, downhole behavior and formation challenges including high-rock strength and interbedded lithologies.

The authors will present three case studies that outline how the software program was used to measure system efficiency to determine which bit would have the highest ROP, total footage capabilities and best dull grade estimate compared to offset runs. The MER will also determine if the system (bit/BHA) or the optimized drilling parameters will improve drilling efficiency.
New Model to Predict Formation Damage due to Sulfur Deposition in Sour Gas Wells
Authors: Mahmoud M. A. , Al-Majed A. A.
Published: February 2012

Elemental sulfur (S8) is often present in considerable amounts in sour gas reservoirs at the reservoir conditions (pressure and temperature). For the isothermal conditions in the reservoir, the reduction in reservoir pressure below a critical value will cause the elemental sulfur to deposit in the formation. Sulfur deposition can cause severe loss in the pore space available for gas, and in turn it will affect the gas well productivity. Accurate prediction of sulfur deposition in the reservoir will help in better management of sour gas reservoirs with potential sulfur deposition problems.

In this paper a new analytical model was developed to predict the formation damage due to sulfur deposition. This model can be used to study the effect of sulfur deposition on gas relative permeability, reservoir porosity, skin damage and reservoir rock wettability. The main objective of this model is to investigate the effect of radial distance on formation damage. Accurate correlations of different rock and fluid properties were used in this model for improved predictions. Accurate correlations of gas viscosity and gas compressibility were used, as the sulfur solubility is a strong function of gas viscosity and gas density. These correlations were used for the calculation of sulfur solubility at reservoir conditions.

Model predictions showed that sulfur deposition depends on the radial distance from the well bore. The most damage occurred in the 3 ft around the wellbore. As the radial distance increases the effect of sulfur deposition becomes negligible. Unlike previous models, which neglected the effect of pressure on gas properties, accurate correlations were used in the new model. Also, various sulfur solubility correlations were tested using the new model. A reduction of 2000 psi in the reservoir pressure, causes a 40 % loss of reservoir porosity at a radial distance of 3 ft from the wellbore and almost 85 % loss in the gas relative permeability at the same distance.
A Field Wide Surface Network Modeling and De-bottlenecking of Production Network for Nine Fields of GNPOC
Authors: Kumar Aditya , Omer Omer Mohamed , Sulaiman Abu Bakr
Published: February 2012

Greater Nile Petroleum Operating Company (GNPOC) is facing challenges to sustain their production, which has been declining at the rate of 15% (approximate) annually. Major part of production is sustained by drilling infill wells re-completion. Pipeline network plays important role in delivering the production from wellhead to Field Processing Facility (FPF). Bottlenecks in pipeline can cause rise in wellhead pressure, which can have impact on production substantially. To identify these bottlenecks and reduce backpressure effect on network GNPOC initiated a project for de-bottlenecking of production pipeline network nine fields. A high fidelity Surface Network Model was developed for all field of GNPOC, which have more than 400 producing wells.

This surface network model will help to quickly identify and accurately quantify bottleneck and other opportunity to reduce backpressure on the system and improve production. This model will also help in further field development, pipeline tie-in / lineup, best nearby Oil Gathering Manifold (OGM) to tie-in new wells etc. The approach of building model is kept simple, robust and scalable. Scalable model will helps GNPOC to add-in well model and integrated this production model to reservoir simulator, facility model and real time data easily and quickly. The model would also assist in evaluating field operation and development plan and expedite the engineering decision process. The identified bottleneck has been ranked in order or priority (which needed immediate attention).

A totally new approach was adopted in the study in terms of the location, training and technology transfer in Sudan. The project engineer worked in close association with operation engineers from field and office. Also actual work has been partially carried out in field as well as office. This approach has given more opportunity to field operation engineers to interact with current modeling tool and technology and increase confidence level.

This paper describes the development of the surface network model for nine fields of GNPOC, technical & project management challenges faced and the way ahead. The model includes the production and transportation networks. This paper also includes major de-bottleneck areas in the production network of GPNOC and How to make effective use of this model for engineering analysis.
A New Binary LCM System Helped Cure Losses during Cementing while Minimizing Risk of Plugging for Slim Liners
Authors: Bhaisora Devesh , Paton Nestor , Waheed Arshad , El Nashar Radi , Farouk Mohamed , Soliman Fathy
Published: February 2012

Fibers are commonly used as lost circulation materials (LCMs) during cementing. Their evolution began with 2-in. long natural fibers, and glass fibers 3-mm long are now available to the industry to address lost-circulation issues.

A major operator needed to cement 5-in. production liner in a depleted reservoir in the Gulf of Suez (GOS). The equivalent circulating density (ECD) exceeded the fracture gradient of the formation while circulating more than 1.5 bbl/min of mud. Losses were predicted during the cementing and an effective LCM added to the fluids was necessary to minimize the loss. A higher concentration of conventional fibers was not recommended because they can block the floats or area around liner-hanger slips.

A new spacer and slurry design was formulated using two different types of LCM systems to help minimize losses during cementing. Both types have minimal chances of blocking restricted flow areas inside pipe. These LCMs help minimize risk of plugging floats or liner hangers, particularly in slim liners where the ID of float valves is only a couple of inches. Powdered LCM was used with the spacer only because it can affect cement slurry properties. This LCM can be used in at least two to three times higher concentrations than conventional fibers. The main objective of using it with spacer was to seal any loss zone before cement began entering into that zone. A different type of inert glass-fiber LCM was used with the cement slurry, but in lower concentrations, to provide extra safety measures for curing losses. The combination of these two fibers helped cure losses from a state of complete loss, to minor losses; later, no remedial jobs were required. This paper summarizes job design and lessons learned from this successful job, which can be applied globally, specifically for slim-liner jobs.
Multidisciplinary Approach for Novel Application of Formation-Pressure-While-Drilling Service in High-Temperature (160 Deg.C) Low Permeability Carbonate
Authors: Bruni Corrado , Odumboni Idowu , Sellami Besma , Turner Marcus , Sanguinetti Marco , Kazmer Jorge
Published: February 2012

The Abiod formation is the principal target in the Miskar field, offshore Tunisia. Consisting of fractured geomechanically stressed carbonate with a measured matrix permeability as low as 0.1 mD. The formation dates from Campanian to lower Maastrichtian and forms a horst structure. The formation has been under production since 1996.

Obtaining formation pressure data was considered critical for determining the magnitude of depletion from production, well-to-well comparisons for vertical and lateral connectivity, forward modeling, completion decisions, and refinement of the field development plan. Historically, this has been a challenge with conventional wireline (WL) formation testers for the following reasons:

Severe depletion and well deviation causing differential sticking High temperatures (150 to 195° C) at the limit of tool electronics Low permeability Fractures and breakouts that can impact seal success

This was overcome with a systematic multidisciplinary approach. After review of historical formation testing data, and influence on seal success with probe vs packer elements, it was decided to apply formation-pressure-while-drilling (FPWD) technology. The key questions with FPWD in this environment are: Can we achieve a good transient profile and what is potential impact of supercharging? These questions were addressed with advanced prejob modeling, which enabled determination of an optimized pretest configuration and testing procedure to minimize potential supercharging effects.

While drilling, stage-in procedures were used, and mud logging total gas data were gathered to identify areas of liberated gas. Pre-run wireline petrophysical data were gathered to characterize the Petrophysic of the reservoir and to calculate an intrinsic permeability profile. Ultrasonic borehole images and caliper data were used to determine the principal horizontal stress directions, fracture frequency, and orientation and to confirm the stratigraphyc dipping of the structure. Combined, this information allowed a focused orientation of the FPWD probe and optimal station selection avoiding fractures and breakouts.

This novel approach resulted in 100% seal success, >50% improvement. Four days of rig time were saved, and the required data were obtained.
Investigating the Effect of the Placement of Permanent Downhole Pressure Gauges in Intelligent Well Systems on Well Productivity: A Field Example
Authors: Anifowoshe Olatunbosun , Osisanya Samuel O.
Published: February 2012

In developing most deepwater fields with limited number of wells, intelligent well systems which consist of many valves and sensors are employed to maximize production capacity under facility constraints. Analysis of sensor data unaffected by wellbore effects allows operators to estimate key reservoir parameters, well capacity and calculate actual flow rates at zonal level. Decisions for operational control is made based on data analysis, the result of which is used to optimize overall field performance and maximize return on investment.

Understanding pressure sensors placement issue is important from pressure-transient analyses viewpoint. Pressure gauges should ideally be placed as close to the perforations as possible to ensure the pressure data is unaffected by friction in the tubing between the perforations and pressure gauges but placement of the gauge is dictated by completion hardware configuration and can be located far away from the point of reservoir fluid entry. This may result to potentially erroneous measured pressure data and may lead to the calculation of inaccurate reservoir parameters and an overestimated mechanical skin value from pressure buildup response.

One of the main operating constraints in deepwater wells is flux limit which is a practical well surveillance tool used to monitor and operate sand control completions, maintaining each producing interval at a maximum safe operating rate, and also monitoring well impairment to allow for proactive remedial operations. Since the flux limit is a function of mechanical skin, if the mechanical skin is over estimated because frictional losses are not properly accounted for, well production may be unnecessarily constrained.

In this paper, analysis was done using a wellbore/reservoir simulator to account for frictional effects in the tubing between the perforations, and the gauge for a field example. Sensitivity analysis was also carried out at different flow rates for each well and simple correlations were developed for predicting frictional effects. Results obtained from calculations showed that pressure gauges placement effect is significant as flow rate and gauge distance from perforations increases. Correcting for this effect increased the flux limit thus increasing production rate on several wells that were previously flux constrained.
Pressure Drawdown Decline Curve Analysis
Authors: Oghena A..
Published: February 2012

With the advent of downhole permanent gauge reliable gathering of flowing bottomhole pressure is on the rise. This essential bottomhole reservoir data is subtracted from the reservoir average pressure to calculate pressure drawdown. The resulting drawdown is commonly used to estimate well productivity index. In this paper we demonstrate how drawdown can be used to generate a decline curve which is extrapolated to estimate future recovery potential.

We show in detail how this method is used to estimate future production performance by linearization of drawdown-time curve and drawdown-cumulative curve and thereafter extrapolate the resulting straight-lines into the future.
Liner Cemented with Lightweight Slurry Allows Gas Production from Depleted Zone, A Case History
Authors: Shaaban Sherif , Salazar Luis , Hughes Baker , Livingstone Bob
Published: February 2012

The use of lightweight materials (ceramic or glass beads) is not new in our industry. But mainly, they have been used to control shallow water/gas flows. There are very few documented cases where lightweight slurries have been pumped across gas producing zones (normally deeper than the previous ones).

British Gas' offshore Scarb Field was producing from the 8.5" open-hole gravel pack completion, below the 9-5/8" casing, until this pay zone was depleted. The plan was then to plug and abandon this zone, side track from the 9-5/8" casing and run a 7" Production Liner to 1,900 mMD approximately. In this depleted field, each well was expected to produce around 60 MMscf of gas. Scarb Field is mainly a gas field, producing considerable amount of gas from the 1,600 – 1,900 meters interval. The pore pressure is between 2,000 – 3,000 psi at the zone of interest.

The dynamic gradient at the shoe depth was limited to 0.65 psi/ft, and the maximum allowed differential pressure over the zones to be cemented was restricted to 500 psi (fracture gradient around 0.7 psi/ft). To overcome this challenging scenario, 12.5 ppg cement slurry (based on ceramic beads) was proposed. As any slurry to be placed across a production zone, this had zero Free Fluid, low Fluid Loss and high Compressive Strength.

The other obvious concern was the quality of the cement bond. Due to the small volume involved, the slurry was batch mixed and all the basic good cementing practices followed.

This paper summarizes how the first two jobs were executed and the results obtained from the CBL/VDL logs.
Selection of Demulsifiers for Produced Crude Oil Emulsions
Authors: Graham David E. , Stockwell Alan
Published: February 2012

A conventional method of treating produced crude oil emulsions is by demulsifier injection; these demulsifiers are usually selected for specific crude oils using the well-known bottle test. It is the purpose of this paper to discuss a physicochemical aspect of the bottle test procedure highlighting a pitfall that has been accepted, and indeed used, for many years by both oil industries and service companies. The main problem is centred around the mode of demulsifier injection. Many demulsifiers are insoluble in crude oil and consequently have poor efficacies when injected in a neat form. In contrast, the performance of demulsifiers previously diluted in organic solvents can be either inhibited or enhanced. The reasons for this are highlighted. The interfacial pressure adsorption isotherms obtained for a given demulsifier in different solvents adsorbing to a crude oil-water interface, coupled to the demulsifier aggregation behaviour in these solvents, show the effect of solvency power on demulsifier interfacial activity. The consequences of this behaviour are demonstrated in the laboratory bottle test and also on the model dehydrating rig for a demulsifier which only poorly resolved an emulsion of water-in-a North Sea crude oil when added neat. We describe how the bottle test can be carried out to effectively and reproducibly screen demulsifiers.
Computer Assisted Gas Production Operations Offshore the Netherlands
Authors: Van der Male Jack , Geurtsen Maarten J. W. , Van Rosse Jaap , Weegink Eef J.
Published: February 2012

The Nederlandse Aardolie Maatschappij B.V. (NAM) is the operator of some 50 large and small gas and oil fields in the Netherlands, both offshore and on land (the latter of which includes the well-known Groningen gas field).

By the end of 1979 NAM's offshore production operations comprised five production platforms producing from four gas fields, into one pipeline to Den Helder onshore. It is expected that by 1986 these will have expanded to 15 platforms in 11 gas fields.

It is the intention to have the offshore production operations ‘unattended’, i.e. no regular staff will be on board for supervision and control of routine production operations. Staff will only be located offshore as and when required for specific tasks like well testing, adjustments, maintenance, repairs, etc. In order to enable such ‘unattended’ and ‘remote control’ production operations in a safe and responsible mode, a computer assisted (CAO – Computer Assisted Operations) tele-information/operations system has been selected. This system has been operational since late 1978 – early 1979 when the gas fields came on stream.

The CAO system comprises onsite metering, transmission to shore and subsequently data capture and data processing in computer facilities onshore (CAO-computer). As a tele-information/operation tool it provides the operator with full status information on offshore operations and enables him to control process variables Selected production data are sent automatically each 24 hours in a batch mode to another computer system in the Netherlands, for reporting and planning purposes.

The paper will highlight the various functions and tasks of the CAO-system and summarise the experience gained so far especially from a user standpoint.
An Appreciation of Middle Brent Sand Reservoir Features by Analogy with Yorkshire Coast Outcrops
Authors: Archer John S. , Hancock Nigel J.
Published: February 2012

This paper shows that many deltaic features of the Middle Brent Sand can be recognised in outcrop sediments along the Yorkshire coast, By visiting convenient outcrops and seeing the extent and often lack of continuity of these reservoir facies we reinforce some of the guidelines for sand body correlation and show their significance in reservoir study calculations.

One of the responsibilities of a reservoir engineer is to understand and predict reservoir performance. Reservoir definition in the Middle Jurassic reservoirs of the North Sea is complicated by complex sedimentary structures and by faulting. The middle part of the Middle Jurassic (Middle Brent Sand) in many North Sea reservoirs was formed by rivers flowing over a delta plain and is characterised by a great variety of facies changes. Understanding and mapping these sand and shale sequences and their relationship with depositional environment is guided significantly by combined sedimentological and reservoir engineering study. A proper understanding by reservoir engineers of the nature and significance of sedimentological descriptions is necessary for the creation of effective reservoir simulation models.
A System for Project Planning and Control
Authors: Clawson Robert M. , Cloughley Terence M. G.
Published: February 2012

A system has been developed for planning and control of a complex North Sea project. The system comprises a network of activities with supporting cost, time and resource data. Together, the network and activity data form the project plan, which subsequently becomes the tool for controlling the project execution. By linking the plan to an economics package, the planned execution is optimized. Other applications of the system became apparent during the course of development and, as a result of using the system, project costs have been reduced and confidence in attainment of schedules has increased. A system of this kind is considered essential for successful execution of future major projects.
Computerized Material Control and its Application to Project Management
Authors: Godliman Bryan , Connew Frederick
Published: February 2012

This paper reviews the development and application of two critical areas of management control data, time and cost, generated by on-going equipment and material progress information.

Quality of information with respect to access, presentation and response times is considered together with the interpretation and use made of data available.

The employment of a common computer based data source with ‘terminal’ interrogation at all important project locations is also discussed with particular respect to the visibility required for effective operational management and the form of data exposure to encourage and promote active participation in control at all levels.