bluuebunny/crossref_metadata_2025 huggingface dataset:
Nicotine Self-Administration Differentially Regulates Hypothalamic Corticotropin-Releasing Factor and Arginine Vasopressin mRNAs and Facilitates Stress-Induced Neuronal Activation
Authors: Yu Guoliang , Chen Hao , Zhao Wenyuan , Matta Shannon G. , Sharp Burt M.
Published: March 2008

Acute nicotine is a potent stimulus for activation of the stress-responsive hypothalamic–pituitary–adrenal (HPA) axis, while chronic nicotine self-administration (SA) desensitizes the ACTH response to self-administered nicotine but cross-sensitizes to mild footshock stress (mFSS). To identify underlying mechanisms, we investigated (1) the effects of chronic nicotine SA on the coexpression of corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) mRNAs, the primary hypothalamic neuropeptides regulating ACTH release, in the parvocellular division of paraventricular nucleus (pcPVN), and (2) mFSS-induced activation of these neurons during nicotine SA. Adult male Sprague Dawley rats were given 23 h/d unlimited access to self-administer nicotine (0.03 mg/kg per injection, i.v.) for 19 d. Brains were double labeled with fluorescencein situhybridization of CRF and AVP mRNAs and triple labeled after mFSS exposure for CRF and AVP mRNAs and c-Fos protein. Chronic nicotine SA significantly increased AVP mRNA signal and the number of pcPVN AVP-positive (AVP+) neurons (twofold to threefold), reduced the number of CRF-positive (CRF+) neurons by ∼60%, but increased pcPVN CRF+/AVP+neuronal number fivefold. Significantly, although chronic nicotine SA did not affect total c-Fos expression induced by mFSS in pcPVN CRF+neurons, the majority of the new CRF+/AVP+population was activated by this heterotypic stressor. These phenotypic neuronal alterations may provide the pivotal mechanism underlying the capacity of chronically self-administered nicotine to cross-sensitize the HPA response to specific stressors, suggesting that nicotine may augment HPA responsiveness to specific stressors in human smokers.
Misplacement of Purkinje Cells during Postnatal Development in Bax Knock-Out Mice: A Novel Role for Programmed Cell Death in the Nervous System?
Authors: Jung A-rong , Kim Tae Woo , Rhyu Im Joo , Kim Hyun , Lee Young Don , Vinsant Sharon , Oppenheim Ronald W. , Sun Woong
Published: March 2008

During early postnatal development, the orchestrated regulation of proliferation, migration and the survival versus elimination of neurons is essential for histogenesis of the cerebellum. For instance, Purkinje cells (PCs) promote the proliferation and migration of external granule cells (EGCs), whereas EGCs in turn play a role in the migration of PCs. Considering that a substantial number of neurons undergo programmed cell death (PCD) during cerebellar development, it seems likely that neuronal loss could have a significant role in the histogenesis of the cerebellum. To address this question, we examined postnatal development of the cerebellum in Bax-knock-out (KO) mice in which the PCD of PC has been reported to be selectively reduced or eliminated, whereas EGCs are unaffected. We confirmed the absence of PC PCD as well as the normal PCD of EGCs in Bax-KO mice. We also observed a subpopulation of PCs that were misplaced in the inner granule cell layer of Bax-KO mice on postnatal day 5 (P5) to P10 and that, by the end of the major period of cerebellar histogenesis (P14), lose expression of the PC marker calbindin. These results suggest that the removal of ectopically located neurons may be a previously unrecognized function of developmental PCD.
Learning-Related Plasticity of Temporal Coding in Simultaneously Recorded Amygdala–Cortical Ensembles
Authors: Grossman Stephen E. , Fontanini Alfredo , Wieskopf Jeffrey S. , Katz Donald B.
Published: March 2008

Emotional learning requires the coordinated action of neural populations in limbic and cortical networks. Here, we performed simultaneous extracellular recordings from gustatory cortical (GC) and basolateral amygdalar (BLA) neural ensembles as awake, behaving rats learned to dislike the taste of saccharin [via conditioned taste aversion (CTA)]. Learning-related changes in single-neuron sensory responses were observed in both regions, but the nature of the changes was region specific. In GC, most changes were restricted to relatively late aspects of the response (starting ∼1.0 s after stimulus administration), supporting our hypothesis that in this paradigm palatability-related information resides exclusively in later cortical responses. In contrast, and consistent with data suggesting the amygdala's primary role in judging stimulus palatability, CTA altered all components of BLA taste responses, including the earliest. Finally, learning caused dramatic increases in the functional connectivity (measured in terms of cross-correlation peak heights) between pairs of simultaneously recorded BLA and GC neurons, increases that were evident only during taste processing. Our simultaneous assays of the activity of single neurons in multiple relevant brain regions across learning suggest that the transmission of taste information through amygdala–cortical circuits plays a vital role in CTA memory formation.
Adaptive Control of Saccades via Internal Feedback
Authors: Chen-Harris Haiyin , Joiner Wilsaan M. , Ethier Vincent , Zee David S. , Shadmehr Reza
Published: March 2008

Ballistic movements like saccades require the brain to generate motor commands without the benefit of sensory feedback. Despite this, saccades are remarkably accurate. Theory suggests that this accuracy arises because the brain relies on an internal forward model that monitors the motor commands, predicts their sensory consequences, and corrects eye trajectory midflight. If control of saccades relies on a forward model, then the forward model should adapt whenever its predictions fail to match sensory feedback at the end of the movement. Using optimal feedback control theory, we predicted how this adaptation should alter saccade trajectories. We trained subjects on a paradigm in which the horizontal target jumped vertically during the saccade. With training, the final position of the saccade moved toward the second target. However, saccades became increasingly curved, i.e., suboptimal, as oculomotor commands were corrected on-line to steer the eye toward the second target. The adaptive response had two components: (1) the motor commands that initiated the saccades changed slowly, aiming the saccade closer to the jumped target. The adaptation of these earliest motor commands displayed little forgetting during the rest periods. (2) Late in saccade trajectory, another adaptive response steered it still closer to the jumped target, producing curvature. Adaptation of these late motor commands showed near-complete forgetting during the rest periods. The two components adapted at different timescales, with the late-acting component displaying much faster rates. It appears that in controlling saccades, the brain relies on an internal feedback that has the characteristics of a fast-adapting forward model.
Okadaic Acid-Sensitive Protein Phosphatases Constrain Phrenic Long-Term Facilitation after Sustained Hypoxia
Authors: Wilkerson Julia E. R. , Satriotomo Irawan , Baker-Herman Tracy L. , Watters Jyoti J. , Mitchell Gordon S.
Published: March 2008

Phrenic long-term facilitation (pLTF) is a serotonin-dependent form of pattern-sensitive respiratory plasticity induced by intermittent hypoxia (IH), but not sustained hypoxia (SH). The mechanism(s) underlying pLTF pattern sensitivity are unknown. SH and IH may differentially regulate serine/threonine protein phosphatase activity, thereby inhibiting relevant protein phosphatases uniquely during IH and conferring pattern sensitivity to pLTF. We hypothesized that spinal protein phosphatase inhibition would relieve this braking action of protein phosphatases, thereby revealing pLTF after SH. Anesthetized rats received intrathecal (C4) okadaic acid (25 nm) before SH (25 min, 11% O2). Unlike (vehicle) control rats, SH induced a significant pLTF in okadaic acid-treated rats that was indistinguishable from rats exposed to IH (three 5 min episodes, 11% O2). IH and SH with okadaic acid may elicit pLTF by similar, serotonin-dependent mechanisms, because intravenous methysergide blocks pLTF in rats receiving IH or okadaic acid plus SH. Okadaic acid did not alter IH-induced pLTF. In summary, pattern sensitivity in pLTF may reflect differential regulation of okadaic acid-sensitive serine/threonine phosphatases; presumably, these phosphatases are less active during/after IH versus SH. The specific okadaic acid-sensitive phosphatase(s) constraining pLTF and their spatiotemporal dynamics during and/or after IH and SH remain to be determined.
Estudo comparativo do uso de prednisolona versus acetato de hidrocortisona no tratamento da hiperplasia adrenal congênita por deficiência da 21-hidroxilase forma clássica
Authors: Leite Flavia M. , Longui Carlos A. , Kochi Cristiane , Faria Claudia , Borghi Mauro , Calliari Luis Eduardo P. , Monte Osmar
Published: March 2008

O tratamento da hiperplasia adrenal congênita (HAC) por deficiência da 21-hidroxilase forma clássica é habitualmente realizado com acetato de hidrocortisona. A hidrocortisona oral, em nosso meio, só está disponível em farmácias de manipulação. A prednisolona possui solução oral estável, comercialmente disponível, e tem como vantagem poder ser utilizada em dose única diária. O objetivo desse estudo foi comparar a eficácia da prednisolona aos resultados obtidos com o acetato de hidrocortisona. Foram estudados 15 pacientes, idade cronológica média (DP) de 7,2 anos (3,6), em dois períodos consecutivos de um ano, inicialmente utilizando a hidrocortisona (17,5 mg/m²/dia, divididos em três doses), seguida do uso de prednisolona (3 mg/m²/dia, dose única matinal). A avaliação dos tratamentos foi realizada por meio das variações do escore Z de estatura para idade cronológica (deltaZE), do escore Z de estatura para a idade óssea (deltaZEIO) e do escore Z do Índice de massa corporal (IMC) (deltaZIMC), bem como os valores da androstenediona em cada período. Não houve diferença na deltaZE, na deltaZEIO e na deltaZIMC entre os dois períodos, assim como nos valores de androstenediona. Concluiu-se que a prednisolona em dose única diária apresenta eficácia semelhante à obtida com a hidrocortisona utilizada três vezes ao dia, podendo ser considerada uma opção terapêutica nos pacientes com HAC por deficiência da 21-hidroxilase.
Contribuição da tomografia computadorizada em pacientes com metástases pulmonares de carcinoma diferenciado de tireóide não-aparentes na radiografia e tratados com radioiodo
Authors: Rosário Pedro W. S. , Tavares Wilson C. , Barroso Álvaro L. , Rezende Leonardo L. , Padrão Eduardo L. , Purisch Saulo
Published: March 2008

A tomografia computadorizada (TC) de tórax é mais sensível que a radiografia na detecção de metástases pulmonares do carcinoma diferenciado de tireóide (CDT), sendo importante conhecer melhor o valor agregado desse método. Este estudo avaliou a resposta ao tratamento com 131I em pacientes com metástases pulmonares de CDTs não-aparentes na radiografia e o valor da TC nesses casos. Foram avaliados 25 pacientes com metástases pulmonares não-aparentes na radiografia, que receberam inicialmente 100 a 200 mCi de 131I. Naqueles com pesquisa de corpo inteiro (PCI) pós-dose com captação pulmonar, um novo tratamento era realizado após seis a 12 meses, e assim sucessivamente. A chance do encontro de captação pulmonar na PCI pós-dose não foi diferente em pacientes com TC negativa ou positiva (100% versus 91,5%). Os valores médios de tireoglobulina (Tg) sérica foram maiores naqueles com TC positiva (108 ng/mL versus 52 ng/mL). PCI pós-dose negativa foi alcançada em 82% dos pacientes com TC positiva e em 92,3% com TC negativa, e a atividade acumulada de 131I para alcançar essa resposta não foi diferente nos dois grupos (em média, 300 mCi). Quarenta e sete por cento dos pacientes com TC negativa ao final do tratamento apresentaram Tg estimulada indetectável, mas nenhum daqueles que permaneceu com TC positiva apresentou-a. Em pacientes com Tg elevada, o resultado da TC aparentemente não altera a indicação da terapia e a atividade de 131I a ser administrada. Nos casos com metástases pulmonares, a permanência de micronódulos na TC nos pacientes com PCI pós-dose negativa após o tratamento foi associada à persistência de Tg detectável.
Avaliação das fístulas urogenitais por urorressonância magnética
Authors: Mamere Augusto Elias , Coelho Rafael Darahem Souza , Cecin Alexandre Oliveira , Feltrin Leonir Terezinha , Lucchesi Fabiano Rubião , Pinheiro Marco Antônio Lopes , Borges Ana Karina Nascimento , Garcia Gustavo Fabene , Seabra Daniel
Published: March 2008

OBJETIVO: As fístulas vesicovaginais e ureterovaginais são complicações incomuns, secundárias a doenças ou a cirurgias pélvicas. O sucesso terapêutico dessas fístulas depende de adequada avaliação pré-operatória para o diagnóstico e visualização do seu trajeto. Este trabalho tem o objetivo de demonstrar o potencial da urorressonância no diagnóstico das fístulas urogenitais e na visualização dos seus trajetos. MATERIAIS E MÉTODOS: Foram analisados, retrospectivamente, os prontuários médicos e as imagens radiológicas e de urorressonância magnética de sete pacientes do sexo feminino com diagnóstico de fístula urogenital. Para a urorressonância foram realizadas seqüências 3D-HASTE com saturação de gordura. RESULTADOS: Seis pacientes apresentavam fístula vesicovaginal e uma paciente tinha diagnóstico de fístula ureterovaginal à direita. Com a utilização da urorressonância magnética, foi possível demonstrar o trajeto da fístula em seis das sete pacientes (85,7%), sem a necessidade de cateterização vesical ou da injeção de contraste. CONCLUSÃO: Este estudo demonstra o potencial e a aplicabilidade da urorressonância na avaliação dessas fístulas.
Software para análise quantitativa da deglutição
Authors: Spadotto André Augusto , Gatto Ana Rita , Cola Paula Cristina , Montagnoli Arlindo Neto , Schelp Arthur Oscar , Silva Roberta Gonçalves da , Yamashita Seizo , Pereira José Carlos , Henry Maria Aparecida Coelho de Arruda
Published: March 2008

OBJETIVO: Apresentar um software que permita uma análise detalhada da dinâmica da deglutição. MATERIAIS E MÉTODOS: Participaram deste estudo dez indivíduos após acidente vascular encefálico, sendo seis do gênero masculino, com idade média de 57,6 anos. Foi realizada videofluoroscopia da deglutição e as imagens foram digitalizadas em microcomputador, com posterior análise do tempo do trânsito faríngeo da deglutição, por meio de um cronômetro e do software. RESULTADOS: O tempo médio do trânsito faríngeo da deglutição apresentou-se diferente quando comparados os métodos utilizados (cronômetro e software). CONCLUSÃO: Este software é um instrumento de análise dos parâmetros tempo e velocidade da deglutição, propiciando melhor compreensão da dinâmica da deglutição, com reflexos tanto na abordagem clínica dos pacientes com disfagia como para fins de pesquisa científica.
Métodos tipo dual simplex para problemas de otimização linear canalizados e esparsos
Authors: Silva Carla Taviane Lucke da , Arenales Marcos Nereu , Sousa Ricardo Silveira
Published: March 2008

Os problemas de otimização linear canalizados e esparsos, objeto principal deste trabalho, surgem em várias aplicações, como por exemplo, problemas de planejamento da produção, problemas de mistura, entre outras. Métodos tipo dual simplex com busca linear por partes foram propostos e analisados em Sousa et al. (2005), com resultados efetivos para problemas densos pequenos e agora são analisados para problemas esparsos maiores. Algumas heurísticas de pivotamento foram implementadas para tentar manter a esparsidade e reduzir o tempo total de resolução dos problemas. Um conjunto de exemplos com estruturas esparsas que tipicamente ocorrem na prática foram gerados aleatoriamente para analisar o desempenho dos métodos. Os resultados computacionais demonstram a eficiência da abordagem.
Assimetria de informação e confiança em interações cooperativas
Authors: Bertolin Rosangela Violetti , Santos Antônio Carlos dos , Lima Juvêncio Braga de , Braga Marcelo José
Published: March 2008

O presente artigo é resultado de um estudo de caso cujo foco retratou a problemática da assimetria de informação em uma organização cooperativa. Após identificar aspectos da assimetria de informação existente no relacionamento agente (dirigentes) e principal (associados), procurou-se compreender seus efeitos nas transações e relações de confiança dos membros com a organização. A pesquisa foi feita com recurso a entrevistas, análise de documentos, registros em arquivos e observação não-participante. Empreendeu-se a Análise de Conteúdo sob a perspectiva qualitativa, buscando as significações da assimetria de informação e confiança por meio da análise das percepções e satisfações dos sujeitos investigados quanto ao gerenciamento de informações categorizadas tanto internas quanto externas à organização. Constatou-se existência de assimetrias nas informações de âmbito interno e externo entre dirigentes e associados. Esta assimetria traz efeitos negativos sobre a confiança dos associados em transacionar com a cooperativa, fatos que permitiram refletir sobre novas implicações para a análise teórica da agência aplicada a estas organizações.
Embarcações motorizadas: uma ameaça aos peixes-boi marinhos (Trichechus manatus) no Brasil
Authors: Borges João Carlos Gomes , Vergara-Parente Jociery Einhardt , Alvite Carolina Mattosinho de Carvalho , Marcondes Milton César Calzavara , Lima Régis Pinto de
Published: March 2008

O aumento do tráfego de embarcações motorizadas em áreas utilizadas para alimentação, descanso e reprodução pelos peixes-boi marinhos tem não só afugentado estes animais, mas resultado em potenciais casos de colisões. Este trabalho tem como objetivo relatar casos de interações entre embarcações motorizadas e peixes-boi marinhos (Trichechus manatus) no litoral Nordeste do Brasil. As interações ocorreram nos Estados do Ceará, Paraíba e Sergipe com três espécimes, sendo um destes com quatro registros. Foram observados transtornos clínicos como edema da região frontal, proptose ocular, emagrecimento e múltiplos cortes ao longo do corpo. Sendo assim, o aumento do tráfego de embarcações, e a falta de normativas e de fiscalização que assegurem a efetiva proteção de determinadas áreas, representam um risco direto para a conservação dos peixes-boi marinhos no litoral Nordeste do Brasil.
Managing Hydrate Risks for a Black Oil Long Subsea Tie-Back When Water Cut Predictions Exceed Original Design
Authors: Harun A. F , Blanchard T. J. , Erdogmus M.
Published: March 2008

The BP King West oil well, located in 5400 feet of water in the Gulf of Mexico, is a 2.3 mile tie back to a 17 mile dual active heated King flowline. This heated flowline, receives throughput from two other BP King oil wells, and produces to the Marlin tension leg platform located in 3200 feet of water.

Recent reservoir studies predicted a higher water cut than originally anticipated during project sanctioning. Thus, a project was executed to evaluate if the existing hydrate management strategy, which relies on the crude’s non-plugging tendencies (contains natural surfactants that act as anti agglomerant), is still adequate or any modifications in operating procedures or facilities were required.

Transient simulations were performed to evaluate if hydrates can be prevented by modifying the operating procedures prior to extended shutdowns and during cold restarts. Experimental work was conducted to confirm the non-plugging hydrate characteristics of King West crude and to determine maximum water cut above which the characteristic no longer holds.

Transient simulations showed that water flow back by gravity and gas injection could not displace all the water from the King West flowline; thus should not be used as preventive measures. The experimental work confirmed non-plugging hydrate characteristics up to 25% water cut. Since the recent subsurface simulations predict maximum water cut just slightly above 25%, King West hydrate management can still rely on the non-plugging hydrate characteristics of its crude.
A General Approach for Deliverability Calculations of Gas Wells
Authors: Al-Attar H. , AL-Zuhair S.
Published: March 2008

This paper presents a general and a simplified method for deliverability calculations of gas wells, which among other advantages, eliminates the need for conventional multipoint tests. The analytical solution to the diffusivity equation for real gas flow under stabilized or pseudo-steadystate flow conditions and a wide range of rock and fluid properties are used to generate an empirical correlation for calculating gas well deliverability. The rock, fluid and system properties, used in developing previous correlations found in literature, were limited to reservoir pressure, reservoir temperature, gas specific gravity, reservoir permeability, wellbore radius, well drainage area, and shape factor. Additional key properties such as reservoir porosity, net formation thickness and skin factor are included in this work to develop a more general dimensionless Inflow Performance Relationship (IPR). It is found that the general correlation, developed is this study, presents the observed field data much closer than previous ones found in the literature. In addition, based on the larger data set, an empirical relation to predict future deliverability from current flow test data is also developed.

The two modified and general relations developed in this work provide a simple procedure for gas deliverability calculations which greatly simplifies the conventional deliverability testing methods. The required data can be obtained from a build-up test, or a single-point flow test, instead of an elaborate multipoint flow test. Further, the broad range of practically all rock and fluid properties used in developing the modified dimensionless IPR curves should cover the majority of the field situations generally encountered. The use of the modified dimensionless IPR curves, the pseudo-pressure formulation and the sensitivity analysis indicate a generality of the approach presented in this paper, irrespective of the gas reservoir system under study.
Optimum Allocation Methodology for Gas Condensate Wells
Authors: Ibrahim M.
Published: March 2008

Production rate and volume information are important for many reservoir surveillance and management tasks. For example, many techniques for estimating the remaining producible gas in a reservoir depend on accurately knowing the amount of gas produced from the reservoir in combination with the average reservoir pressure. History-matching gas, and water production data using a reservoir simulator is a common practice in workflows used for making investment decisions such as whether or not to drill more wells. The quality of a history-matched model is limited by the quality of the allocated production data. An additional need for quality rate allocation is that the production volumes for individual wells or reservoirs are often required for regulatory reporting.

Production allocation for high temperature and pressure is not easy task as the current orifice plate flow meter is not deigned for high condensate gas ratio (CGR). The error in using current meters could reach up to 60 percent in gas rate due to accumulation for condensate on the orifice plate. In this field, there are only two wells producing from two zones. There is only one production separator in the platform which makes the allocation difficult due to the need for shutting down one well to do multirate test on the other well. One of the wells has a downhole pressure gauge but the other well does not.

In this paper, we will present new procedures for using a combination of the downhole pressure and multirate tests to construct the accurate inflow performance curve (IPR) for each well. Then, at each reservoir pressure the relationship between wellhead flowing pressure and flow rate is programmed by Visual Basic program (VBA). This program is used to allocate daily gas rate from the wellhead flowing pressure.

This method shows high accuracy for allocating the history and current gas flow rate with high condensate ratio. Also, provide accurate well test analysis and accurate reserve calculation.
Laboratory Evaluation of Water Swellable Materials for Fracture Shutoff
Authors: Abbasy Imran , Vasquez Julio , Eoff Larry , Dalrymple Dwyann
Published: March 2008

The existence of high permeability features such as fissures, fractures, and eroded out permeability zones, diminishes the sweep efficiency of any water, gas, or polymer flooding. This paper presents the laboratory evaluation of three water swellable materials that can be bullheaded into the well to shut off fractures. The water swellable materials would be mixed on the fly, entering fissures and fracture systems as they swell without invading the matrix of the rock. The rate of absorption can be controlled based on the particle size, carrier fluid, and formation fluid. This conformance technology is also applicable to address loss circulation problems in production and injection wells.

The following materials were evaluated: (a) a polyacrylamide polymer, (b) a chloroprene rubber, and (c) a nitrile rubber. The polyacrylamide polymer is capable of absorbing 30 to 400 times its own weight in water while the two rubbers swell approximately 5 to 10 times their original weight. The water swellable materials were evaluated for effectiveness to: (1) provide controllable swelling rates at different conditions, (2) shut off the flow of water in synthetic cores with simulated fractures at 135°F, and (3) provide long-term thermal stability in H2S and CO2 environments.

Discussed are: (1) the methodology used for measurement of swelling properties for each material at different conditions including carrier fluid, particle size, and temperature, and (2) core flow tests with simulated fractures. These materials are nontoxic and do not contain heavy metal crosslinkers. Based on this study, these materials present an innovative technology for fracture shutoff and to control loss circulation problems. In addition, these materials are resistant to acid contamination in CO2 and H2S environments.
Challenging Chemical Gas Shut off in a Fractured Carbonate Reservoir—Case Studies
Authors: Al-Sharji Hamed , Ali Ehtesham , Kosztin Bela , Edwards Clement , Neyaei Fardin Ali , Shaheen Tarek
Published: March 2008

This paper discusses the gas shut-off treatments carried out in a fractured carbonate field in north Oman and also describes the good practices and lessons learnt from a number of jobs. In addition to the technical analysis, the paper also addresses the economic value of the campaign.

Oil production from this field with complex geology and reservoir mechanism was negatively affected by gas breakthroughs in several wells. The constraints on gas handling capacity resulted in shutting-in a number of high GOR wells. These wells were required to be treated to shut-off source of the gas breakthrough in order to restore oil production. Challenges faced in shutting off these gas zones included: 1) Poor cement bond behind the liner shoe. 2) Massive fractures resulting in loss circulation. 3) Uncertainty with fractures volume estimation. 4) Fracture shut-off in open-hole sections. 5) Treatment execution under sub-hydrostatic conditions.

To overcome these challenges a robust chemical shut off methodology had to be innovated. This methodology consisted of the following main pillars: a) Utilize various reservoir diagnostics tools to identify fractures and sources of high GOR. b) Use of flowing cross-linked polymer gel combined with a ringing type of cross-linked polymer gel as a capping fluid. c) Utilize an on-fly mixing system that enables volume and concentration adjustment as plugging progression dictates. d) Utilize matrix diagnostics plot along with modified hall plot in real-time to continually estimate flowing gel volume. e) Deploy a fit-for-purpose gel placement assembly for treatment under Sub-hydrostatic conditions.
Integration of Resistivity Imaging and Enhanced Vertical Resolution Nuclear Magnetic Resonance Data for Improved Quantification of Reserves in Thinly Bedded Reservoirs
Authors: Hashem Abdel Hakim , Reda Ahmed
Published: March 2008

There is little that is more important to an operating company than the accurate assessment of its oil and gas reserves. In thick, clean formations that are relatively homogeneous laterally and vertically, reserves calculations are usually straightforward. The level of uncertainty in these calculations can increase substantially, however, with increasing reservoir complexity.

One such source of complexity is the challenge presented by thinly laminated formations. The challenge is that thinly bedded formations are, by definition, below the resolution of the most commonly used logging tools. As such, many thin bed formations may not even be detected, let alone properly evaluated and accounted for in reserves estimates.

Two wireline formation evaluation technologies are available that, when used in concert with conventional macro wireline logs, can substantially reduce reserves uncertainty in thin bed formations.

One of these is a resistivity imager tool such as the X-tended Range Micro Imager (XRMI). With vertical resolution down to 0.10 inches, resistivity imager tools provide a reliable means of thin bed detection. The other technology is nuclear magnetic resonance (NMR). NMR tools such as the MRIL Prime can provide estimates of formation porosity, permeability and hydrocarbon properties in thin bed formations, albeit with relatively coarse vertical resolution which can be enhanced by post-processing technique.

This paper explores a new method for enhancing the vertical resolution of the MRIL data that leads to integrates the best attributes of both NMR and resistivity imaging tools to bring about improved reserves estimates. A case study is presented from the Nile delta in which a field - comprised of a thick, clean, high porosity deltaic sedimentary layer overlain by a thinly laminated sand-shale sequence – is quantitatively evaluated for fluid saturation and productivity with a new post-processing technique. Recommendations for future data integration methods and applications are also proposed.
Modeling and Simulation of Instabilities in Gas-lifted Oil Wells
Authors: Jahanshahi E. , Salahshoor K. , Kharrat R. , Rahnema H.
Published: March 2008

Unstable production behavior affects many offshore fields, particularly at their decline stages. "Casing heading" and "density wave" are two types of instability that have been identified and both can result in production loss. These instabilities have influence on each other, but the interaction has not been fully addressed yet. One contribution of this paper is to study the interplay of these two phenomena. For this purpose, key variable of density wave phenomenon; pressure at injection point in tubing that is governed by an integral equation; is considered as a fourth state variable added to 3-D dynamical model of casing heading. Another contribution is some modifications on the casing heading and density wave dynamic models. Finally, the proposed model is simulated in MATLAB® and OLGA®, and the results are compared with well operation facts and data from field.
Meeting the Flow Assurance Challenges of Deepwater Developments: From Capex Development to Field Start Up
Authors: Jordan M. M. , Feasey N. D.
Published: March 2008

As oil accumulations in easily accessible locations around the world become less available developments in deeper water locations become a more common target for field development. Deepwater projects, particularly subsea development, present a host of challenges in terms of flow assurance and integrity. In this paper the focus will be on the chemical control of flow assurance challenges in hydrate control, scale control and wax/asphaltene control within deepwater (>750 meter) developments. The opportunities for kinetic hydrate control vs. conventional thermodynamic hydrate control will be outlined with examples of where these technologies have been applied and the limitations that still exist. The development of scale control chemical formulations specifically for subsea application and the challenges of monitoring such control programs will be highlighted with developments in real time and near real time monitoring. Organic deposit control (wax/asphaltene) will focus on the development of new chemicals that have higher activity but lower viscosity than currently used chemicals hence allowing deployments at colder temperatures and over longer distances.

The factors that need to be taken into account when selecting chemicals for deepwater application will be highlighted. Fluid viscosity, impact of hydrostatic head on injectivity, product stability at low temperature and interaction with other production chemicals will be reviewed as they pertain to effective flow assurance.

This paper brings learning from other deepwater basins with examples from the Gulf of Mexico, West Africa and Brazil, which will be used to highlight these challenges and some of the solutions currently available along with the technology gaps that exist.
Seismically Driven Characterization, Simulation and Underbalanced Drilling of Multiple Horizontal Boreholes in a Tight Fractured Quartzite Reservoir: Application to Sabria Field, Tunisia
Authors: Ouenes A. , Robinson G. , Balogh D. , Zellou A. , Umbsaar D. , Jarraya H. , Boufares T. , Ayadi L. , Kacem R.
Published: March 2008

This paper describes the application of the Continuous Fracture Modeling (CFM) workflow to the Sabria field in Tunisia. This workflow consists of four steps. The first step in the workflow is to interpret key seismic horizons and use them in high resolution inversion and spectral imaging to create impedance and frequency-dependent seismic attributes. The second step consists of building seismically constrained geologic models of lithology and other petrophysical properties. The third step consists of using the derived geologic models along with all the post-stack seismic attributes and additional geomechanical models to derive high resolution 3D fracture models. The fourth step is to use the derived fracture models in a reservoir simulator to verify the validity of the models by their ability to match past individual well performances and to design optimal well trajectories that intercept a large number of fractures and produce economical oil rates. This workflow was applied to the Sabria field in Tunisia and was followed by actual drilling. The seismic attributes and the appropriate geologic and geomechanical models were used as input in REFRACT, a fracture modeling software, to create accurate 3D fracture models. The resulting fracture porosity and permeability were input in a reservoir simulator. All the past individual well performances were matched, confirming the reliability and accuracy of the derived fracture models. The resulting simulation and fracture models were used to plan multiple horizontal boreholes, drilled underbalanced from a single platform. The resulting oil production from the boreholes and the recorded logs confirm the validity of both the fracture and simulation models.
CO2 Geological Storage Field Development: Initial Experiences in an Emerging Industry
Authors: Jenvey N. J. , Moen R. S. , Muller N. , Buehler J. , Costello M. S. , Schwander M. M.
Published: March 2008

Global climate change induced by the release of greenhouse gases (notably carbon dioxide) into the atmosphere is a topic of considerable discussion around the world. Shell believes that this debate is over, and instead has entered into a debate about what we can do about it. Therefore as part of Shell's integrated carbon management plan (which includes renewable energy sources and fossil fuel efficiency improvements) we are currently investigating several sites and geologic formations across the globe for their suitability in the long-term storage of CO2 using technology and experience from over 30 years of safely transporting and injecting CO2 in oil and gas operations.

This talk will illustrate some of the technical challenges that can be expected during the implementation lifecycle (from site exploration to closure) of such projects, and is based upon our learning both in recent CO2 sequestration projects and the industrial analogue of CO2 Enhanced Oil Recovery. These include: establishing initial screening criteria; developing appraisal and piloting techniques; building appropriate reservoir models; designing fit-for-purpose injection wells; assessing containment risks; and determining monitoring requirements. These projects are particularly challenging in today's society where information is easily accessible by the public, yet policy and regulations are still evolving. Based on our own experience, we suggest that an integrated technical evaluation is critical for the accurate long-term fate assessment of CO2 geological storage sites.
Case Study: The Application of Sand Management Solution for the Sarir Field in Libya
Authors: Qiu K. , Gherryo Y. , Shatwan M. , Marsden R. , Alexander J. , Retnanto A.
Published: March 2008

Sand production from the Sarir field became a major concern for AGOCO at the end of the 1980s when ESPs were introduced to the field. The sanding severely impaired the performance of field, and consequently led to significant economic loss.

AGOCO recognized that it was facing a major challenge in terms of understanding potential sanding risk for Sarir, and that it was necessary to design and implement a sandface completion and sand management strategy for more than 400 wells in the field. It was decided to apply a particular systematical approach, termed as Sand Management Solution (SMS), to properly address the sanding issues it was facing, which involved prediction, prevention, monitoring, and, if required, remediation activities. The first step in the SMS was to obtain a clear understanding of the cause and the mechanism for the sand production. This knowledge was required because attempts to run new completion designs without knowing the cause of the sand and understanding the risks had been proved costly, and would be likely to fail.

To this end, a SMS was implemented in Sarir field. The work started from geomechanical reservoir characterization including geomechanics core laboratory test and mechanical earth model building, sanding prediction and evaluation, and a detailed review of sanding history to understand the severity of the sanding risk and sanding mechanism. Based on this knowledge, sanding management and remedial completion measures were devised that would minimize economic loss caused by sanding and optimize hydrocarbon production.

This paper provides details of implementation of this SMS in the Sarir field, and demonstrates that a systematical approach is required when addressing sanding issues in giant mature fields such as Sarir.
Integrated Fluid Characterization: Maximising the Value of Fluid Information From Exploration to Production
Authors: McKinney Daniel , Clarke Ed , Elshahawi Hani , Flannery Mattew , Hashem Mohamed , Stankiewicz Artur
Published: March 2008

Fluid characterisation is critically important to effective reservoir management. Misinterpreting reservoir properties, for instance, can result in non-optimal well placement, completion strategy, and facilities design as well as large errors in reserves, drainage volume and production rate predictions. Characterisation of reservoir fluids based on a single technique or technology such as mud-gas logging, wireline logging, PVT, or wellsite chemistry is standard in most E&P operations. Integrated approaches involving multiple tools and technologies are still relatively new to the industry, but Shell, through its FEAST (Fluid Evaluation and Sampling Technology) global centre of expertise, is routinely implementing such integrated approaches for fluid characterisation. For example, advanced mud-gas logging data can be used for fluid facies prediction and picking sampling points for formation testing; PVT data can be calibrated against mud logging data; and downhole fluid analysis can provide fluid property measurements real time, during sampling. Integration ensures that the evaluation objectives are addressed using the most optimal technologies and workflows, maximises the value of information, and improves operational decision-making.

The interpretative workflow also involves integrating advanced mud-gas logging technology data with formation testing, Geochemical, and PVT data to predict fluid properties in unsampled wells. Understanding reservoir fluid properties ahead of the actual sampling operation enables smart decisions while drilling and logging, which can save millions of dollars in operational costs. The sampling process can be optimized in terms of where and when to sample, and how many samples to collect; and the quality of the fluids collected can be substantially improved. Because each technique has its strengths and limitations, integration is far more valuable than relying on any single source for interpretation. Ultimately, no technique is used in isolation, and no interpretation is worked in a vacuum without adequately understanding the geological setting and the fluid sourcing, migration, and trapping mechanisms.
Deepwater Gulf of Mexico Development Challenges Overview
Authors: Close Frank , McCavitt Bob , Smith Brian
Published: March 2008

Chevron's role as a major player in the global energy arena is due in large part to the Company’s extensive oil and gas exploration and production operations. A large proportion of the Company’s extensive reserves are located in deepwater locations throughout the world. The Company is one of the largest producers of crude oil and natural gas on the Gulf of Mexico (GoM) shelf and among the top acreage holders in the Gulf's deepwater1 and ultra deepwater2. Following on from the successes of an aggressive deepwater exploration campaign in the Gulf of Mexico, a series of major discoveries were rapidly appraised and moved to development (Fig. 1).Fig. 1Chevron GoM appraisal and development activities

This paper will give a high level review of some of the recent development challenges for the deepwater and ultra deepwater fields in the GoM and will explain how these challenges were addressed and how the Company plans to address even more demanding challenges in the future.
Road to ruin
Authors: Laurance William
Published: March 2008

Tough laws won’t save poor nation’s ecosystems until the impacts of developments are taken seriously

Reprinted with permission from New Scientist, issue 2607, 06 June 2007, page 25

Himalayan Journal of Sciences Vol.4(6) 2007 p.9
Acts of God are not the problem
Authors: Sicroff Seth
Published: March 2008

Mountain tourism both increases the risks posed by mountain hazards and also provides the economic opportunity to effectively cope with those hazards. Salient points and recommendations from participants in “Mountain Hazards, Mountain Tourism” e-conference include:Although climate change is increasing the likelihood of glacial lake outburst floods (GLOFs), we now have the scientific tools to monitor and quantify such hazards. Unfortunately, those tools are not being used on a regular basis. This increases the hazard of media sensationalism, which in turn increases the risk of serious economic damage as well as lost scientific credibility. Contrary to published reports, the hazard mitigation project at Tsho Rolpa in Rolwaling was left in an incomplete state and without provision for scientific monitoring; the lake still poses a great risk. More attention must be paid to the human component of mountain hazards. Ethnic cleansing programs such as the current disaster in Bhutan cause suffering and economic damage on a scale that beggars most natural events. A useful step toward the rational confrontation with all sorts of disasters (not just those that impact mountains) would be the conversion of King Gyanendra’s palace into a Disaster Management University.

Himalayan Journal of Sciences Vol.4(6) 2007 p.11-19
Phenology and water relations of eight woody species in the Coronation Garden of Kirtipur, central Nepal
Authors: Shrestha Bharat B , Uprety Yadav , Nepal Keshav , Tripathi Sandhya , Jha Pramod K
Published: March 2008

Phenological activities of eight woody species planted in Kirtipur (central Nepal) were examined, each for one dry season between September 2001 and June 2003. From Pressure Volume (P-V) analysis, we determined relative water content at zero turgor (RWCz), osmotic potential at zero turgor (Ψsz) and full turgor (Ψsf ), and bulk modulus of elasticity (ε) once a month through the course of dry season. Both evergreen species (Cotoneaster bacillaris Wall., Quercus lanata Sm., Ligustrum confusum Decne., Woodfordia fruticosa (L.) Kurz.) and deciduous species (Celtis australis Linn., Alnus nepalensis D.Don., Bauhinia variegata Linn. and Lagerstroemia indica Linn.) put out their new leaves during the dry summer when day length and temperature were increasing. Generally, bud break coincided with concentrated leaf fall during the dry summer and the leaf fall reduced total leaf area to its lowest value. The deciduous species were leafless for one to three months, followed by a prolonged period of leaf production and shoot elongation. Evergreen and deciduous species manifested distinct adaptive strategies to water deficit. Evergreens can reduce osmotic potential (Ψs) to its low value and maintain proper water potential (Ψ) gradient from soil to plant, which facilitates absorption of water during dry season. Elastic tissue in deciduous species is coupled with leaf shedding during the dry season; both factors may help maintain proper Ψs for new growth during dry period. One evergreen species (Woodfordia fruticosa) and three deciduous species (Celtis australis, Bauhinia variegata and Lagerstroemia indica) have inherently high dehydration tolerance due to their elastic tissue. During drought there has been osmotic adjustment in Quercus lanata, and elastic adjustment in Ligustrum confusum, Celtis australis and Lagerstroemia indica.

Key words: Himalayas, Pressure Volume (P-V) curve, relative water content (RWC), osmotic adjustment, elastic adjustment

Himalayan Journal of Sciences Vol.4(6) 2007 p.49-56
Production of haploid wheat plants from wheat (Triticum aestivum L.) x maize (Zea mays L.) cross system
Authors: Niroula Raj K , Bimb Hari P , Thapa Dhruva B , Sah Bindeswor P , Nayak Sanothos
Published: March 2008

The present study was carried out taking single F1 wheat and four maize varieties, viz. Arun-1, Arun-2, Khumal Yellow and Rampur Composite, to determine the efficiency and influence of maize genotypes on various parameters of haploid formation. Wheat spikelets were hand pollinated with freshly collected maize pollen, and 1 ml of 100 ppm 2,4-D was immediately injected on the uppermost internode. Twenty-four hours after 2,4- D injection, the cups of the florets were filled with the same solution of 2,4-D for two more consecutive days. Seventeen days after pollination, the embryos were excised and cultured in half-strength MS basal medium supplemented with 30 g/l sucrose, and 7 g/l agar. The cultured embryos were maintained at 25°C with 16/8 hours light/darkness after treating in the dark for seven days at 4°C and incubation in the dark for seven days at 25°C. Application of 2,4-D after pollination was found to be essential to the recovery of culturable size of embryos. The significant effect of maize genotypes on frequency of ovary development, embryo formation and haploid plant per pollinated floret was observed. The mean percentages of embryo formation and haploid plants per pollinated floret varied from 5.17 to 21.45 and 0.96 to 10.15, respectively, depending upon the maize varieties used. The highest frequency of embryo recovery and plant per floret was found when wheat F1 was pollinated with Arun-2 followed by Arun-1 and Khumal Yellow. It is suggested that the production of dihaploids (DHs) in wheat can be enhanced by using more responsive maize genotypes as pollinators.

Key words: 2,4-D, caryopsis, floret, haploid embryo, wheat x maize cross

Himalayan Journal of Sciences Vol.4(6) 2007 p.65-69