bluuebunny/crossref_metadata_2025 huggingface dataset:
Estoque de serapilheira e fertilidade do solo em pastagem degradada de Brachiaria decumbens após implantação de leguminosas arbustivas e arbóreas forrageiras
Authors: Silva André Barbosa , Lira Junior Mario Andrade , Dubeux Junior José Carlos Batista , Figueiredo Márcia do Vale Barreto , Vicentin Rayssa Pereira
Published: June 2013

As pastagens formam a base da pecuária brasileira; essas sofrem degradação em larga escala por deficiência de nitrogênio (N). O consórcio com leguminosas, além de fixar N, pode apresentar outros efeitos na fertilidade do solo como acidificação ou retirada de nutrientes de camadas mais profundas para as mais superficiais. Este trabalho objetivou avaliar o estoque de serapilheira e a fertilidade do solo em pastagens degradadas de braquiária (Brachiaria decumbens), após implantar leguminosas arbustivas e arbóreas forrageiras. Para isso, uma amostragem foi realizada em março de 2010 em um experimento no campo, introduzindo pastagem degradada de Brachiaria decumbens, em julho de 2008, com sabiá (Mimosa caesalpiniifolia), leucena (Leucaena leucocephala), mororó (Bauhinia cheilantha) e gliricídia (Gliricidia sepium), além de braquiária adubada e não adubada com N. As amostras de solo e serapilheira foram coletadas aos 0-10, 10-20 e 20-40 cm de profundidade, em três transectos, alternando pontos cobertos por gramíneas e leguminosas, totalizando sete amostras compostas por parcela para determinar pH, P, K, Ca, Mg e Al no solo, enquanto SB, t e m foram calculados. A serapilheira foi separada visualmente em leguminosas, gramíneas e materiais não identificados, em que foram utilizados para quantificação de matéria seca, matéria orgânica, N, P, C, fibra detergente ácido e lignina. A introdução das leguminosas aumentou os teores de N total na serapilheira e reduziu as relações C:N, com destaque para gliricídia e sabiá; entretanto, essa última apresentou elevados teores de lignina. Houve efeito significativo da cobertura por leguminosas, sem diferenças entre essas, para pH e K, na profundidade de 0-10 cm, e para Al e m, aos 10-20 cm de profundidade.
Estratégias de manejo da palha de azevém para cultivo do arroz irrigado em sucessão
Authors: Correia Silmara da Luz , Silva Paulo Regis Ferreira da , Serpa Michael da Silva , Vieira Vladirene Macedo , Boeni Madalena , Menezes Guilherme Borba
Published: June 2013

A adoção de sistemas de rotação e sucessão de culturas é um dos pré-requisitos fundamentais para sustentabilidade dos sistemas de produção agrícola. Diante disso, o objetivo deste trabalho foi avaliar os efeitos de época de dessecação do azevém e de dose de adubação nitrogenada, aplicada na semeadura do arroz irrigado em sucessão, como estratégias para viabilizar o uso dessa sucessão em áreas de cultivo de arroz irrigado. O experimento foi conduzido no campo em dois anos agrícolas (2008/09 e 2009/10), em Cachoeirinha, RS, em um Gleissolo Háplico Ta distrófico típico. Utilizou-se o delineamento de blocos casualizados, em parcelas subdivididas, com três repetições. Os tratamentos foram constituídos de quatro épocas de dessecação do azevém (90, 70, 50 e 30 dias antes da semeadura do arroz, no primeiro ano; e 49, 34, 19 e 6, no segundo ano), de cinco sistemas de manejo da adubação nitrogenada no arroz irrigado, obtidos pela combinação de quatro doses de N na semeadura (0, 10, 20 e 40 kg ha-1) e de quatro doses de N em cobertura (150, 140, 130 e 110 kg ha-1), totalizando 150 kg ha-1, e de uma testemunha sem aplicação de N, durante todo o ciclo da cultura. A presença de palha de azevém com as plantas mantidas de pé não prejudica o estabelecimento inicial de plantas de arroz cultivado em sucessão. O rendimento de grãos de arroz irrigado cultivado em sucessão ao azevém não é influenciado pela época de dessecação de azevém e pela dose de N aplicada em semeadura.
O vídeo didático "Conhecendo o Solo" e a contribuição desse recurso audiovisual no processo de aprendizagem no ensino fundamental
Authors: Jesus Olinda Soares Fernandes de , Mendonça Thiago , Araújo Izabel Cristina Leinig , Cantelli Katy Boniza , Lima Marcelo Ricardo de
Published: June 2013

O uso de recursos audiovisuais no ensino de solos, como estímulo para os alunos, pode auxiliar na construção de um conhecimento crítico e reflexivo. Este trabalho objetivou analisar a contribuição do vídeo "Conhecendo o Solo" no ensino e na aprendizagem dessa temática no nível fundamental. Com o intuito de estimular os alunos a perceber a importância dos solos nos ambientes, esse vídeo foi aplicado como conteúdo de ensino. Em seguida, foi aplicado um questionário, em que os alunos descreveram as principais ideias transmitidas por esse, especificando os pontos positivos e negativos do recurso utilizado. A análise do questionário revelou que o uso do vídeo foi um facilitador da aprendizagem. Porém, as respostas dos estudantes indicaram que alguns aspectos necessitam de adequações, como o dinamismo, a interatividade, a quantidade de informações e a narração. Mesmo assim, o recurso foi classificado pela maioria dos alunos como adequado, e o repertório de conteúdos apresentou similaridade com o exposto no vídeo, caracterizando-o como um recurso de influência positiva no processo de ensino e aprendizagem.
Efeito do uso profilático do anti-inflamatório não-esteroide ibuprofeno sobre o desempenho em uma sessão de treino de força
Authors: Correa Cleiton Silva , Cadore Eduardo Lusa , Baroni Bruno Manfredini , Silva Eduardo Ramos da , Bijoldo Jocelito Martins , Pinto Ronei Silveira , Kruel Luiz Fernando Martins
Published: June 2013

INTRODUÇÃO: Medicamentos anti-inflamatórios não esteroides, como o ibuprofeno, têm sido utilizados por atletas de várias modalidades com o intuito de aumentar desempenho esportivo. OBJETIVO: Verificar o efeito do uso profilático de ibuprofeno sobre desempenho em uma sessão de treino de força. MÉTODOS: Um ensaio clínico, cruzado, randomizado, duplo-cego e placebo-controlado foi desenvolvido com 12 praticantes regulares de treino de força do sexo masculino, os quais realizaram uma sessão de treino após a ingestão de ibuprofeno (1,2 g) e uma outra após a ingestão de placebo. Seis séries dos exercícios supino e agachamento foram realizadas em cada sessão de treino com uma carga constante correspondente a 65% da 1RM de cada exercício. O desempenho no treinamento foi mensurado através do número de repetições que os voluntários conseguiram realizar em cada série de exercício a cada sessão de treino de força. RESULTADOS: Não foram verificadas diferenças significativas de desempenho no treino de força com a administração prévia de placebo ou ibuprofeno (p > 0,05). CONCLUSÃO: A ingestão de ibuprofeno nos parâmetros de administração adotados pelo presente estudo não promove qualquer tipo de alteração na tolerância ao exercício em uma sessão isolada de treino de força, o que contraria a indicação dessa substância para fins ergogênicos no treino de força.
Incidência e fatores de risco de lesões em jogadores de futsal portugueses
Authors: Serrano João Manuel , Shahidian Shakib , Voser Rogério da Cunha , Leite Nuno
Published: June 2013

INTRODUÇÃO: A reduzida expressão de estudos publicados sobre a incidência de lesões no Futsal em Portugal justificou a realização deste trabalho. OBJETIVO: Identificar as potenciais causas de lesões nesta modalidade, referência para o desenvolvimento de protocolos específicos de prevenção de lesões. MÉTODOS: A amostra foi constituída por 411 jogadores federados de Futsal em Portugal, masculinos e femininos, de diferentes níveis competitivos. Foram utilizados os dados coletados num questionário com informação retrospectiva. O tratamento estatístico consistiu na análise inferencial entre grupos através do teste de Kruskal-Wallis e do teste para dados não paramétricos de Mann-Whitney (nível de significância de 5%). RESULTADOS: Os resultados confirmaram a entorse da articulação tíbio-társica como a lesão de maior incidência (48,8% do total) no Futsal. As lesões com período de impedimento entre oito e 28 dias tiveram a maior expressão (52,7% do total). Este estudo não revelou diferenças significativas em relação ao gênero ou posição em que os jogadores ocupam na quadra sobre a incidência, o tipo ou a região anatômica das lesões. No entanto, verificou-se significativamente maior incidência de entorses e contraturas em situação de treino e maior incidência de roturas musculares e fraturas em jogo, sendo que essas últimas provocaram um período de impedimento maior para os atletas. Também se verificou significativamente maior incidência de lesões articulares ou ósseas, entorses e fraturas, em resultado do contato com adversários e maior incidência de lesões musculares ou ligamentares sem contato com adversários. Os resultados não evidenciaram diferenças significativas na lateralidade das lesões. CONCLUSÃO: Os resultados realçam a importância de programas específicos de prevenção da entorse da tíbio-társica, especialmente nas crianças e jovens, independentemente da posição que ocupam na quadra, particularmente em situações de contato com adversários.
Comparação de diferentes métodos de controle da carga interna em jogadores de voleibol
Authors: Bara Filho Maurício Gattás , Andrade Francine Caetano de , Nogueira Ruan Alves , Nakamura Fábio Yuzo
Published: June 2013

INTRODUÇÃO: A capacidade de monitorar precisamente a carga de treinamento é um importante aspecto para a efetividade da periodização e para a prevenção de efeitos negativos, como a queda no rendimento. OBJETIVOS: Comparar e correlacionar diferentes métodos de controle de carga interna de treinamento em jogadores de voleibol. MÉTODOS: Quinze atletas profissionais de voleibol do sexo masculino, com idade entre 18 e 30 anos, que competiam em níveis estaduais e nacionais, participaram deste estudo. A carga de treino para cada sessão foi calculada utilizando três diferentes métodos: PSE da Sessão, Zonas de FC (TRIMP) de Edwards e de Stagno. RESULTADOS: Verificou-se que há correlação positiva e significativa entre o método proposto por Foster, Edwards e Stagno. No entanto, os valores das correlações individuais entre PSE e Edwards (0,451 a 0,670), em geral, foram ligeiramente maiores que os da correlação entre PSE e Stagno (0,206 a 0,597). CONCLUSÃO: O método proposto por Edwards, bem como o método proposto por Foster, melhor refletem as cargas de treino no voleibol, fazendo com que o monitoramento das cargas seja realizado de maneira mais fidedigna e confiável quando realizado por esses dois métodos.
Ultimate lateral pressure of two side-by-side piles in clay
Authors: GEORGIADIS K. , SLOAN S.W. , LYAMIN A.V.
Published: June 2013

The ultimate earth resistance for a group of two side-by-side piles that are laterally loaded in clay is investigated using four different methods of analysis: three numerical (the displacement finite-element method, and the upper- and lower-bound finite-element limit analysis methods) and one analytical (an analytical upper-bound plasticity method developed in this paper). The results of the three numerical methods are shown to be in excellent agreement, while the analytical solution presents a theoretical upper bound that is very close to the numerical results. The results of the analyses are used to identify the predominant failure mechanisms for different pile spacings and pile–soil adhesions. They are also used to develop a design chart and design equations for determination of the ultimate lateral bearing capacity factor.
Water-sensitive urban design: learning from experience
Authors: Dolman Nanco , Savage Amy , Ogunyoye Fola
Published: June 2013

Water introduces both opportunities and risks to urban areas. Society is faced with the challenge of finding solutions to complex and interrelated problems such as living safely in densely populated deltas, planning ahead for climate change, finding alternatives to fossil fuels, and urban redevelopment. We need to make sure that all this is achieved in a sustainable way. This paper elaborates on the need to transition towards water-sensitive cities, drawing on the experience of urban water management and water-sensitive urban design in the Netherlands and the UK. This transition involves strengthening the integration of water in spatial planning and design processes, requiring any spatial intervention or new development to be evaluated on opportunities for sustainability and innovation. Design tools or building blocks are suggested that enable the transition to a city in which the awareness of water, energy, nature and living environment are connected, in which developments always take place in a resilient and climate-proof way, and where water can be a focus for enjoyment and vitality. The paper concludes with recommendations on how the UK can build on its own experience and learn from the Netherlands to achieve more water-sensitive urban design.
Water-sensitive urban design: opportunities for the UK
Authors: Ashley Richard , Lundy Lian , Ward Sarah , Shaffer Paul , Walker Louise , Morgan Celeste , Saul Adrian , Wong Tony , Moore Sarah
Published: June 2013

Water-sensitive urban design (WSUD) is a concept that is gaining support as a means to manage urban water systems in an integrated way through the better positioning of the topic of water in urban planning and design processes. Water-sensitive urban design is emerging in the UK and this paper sets the scene and identifies the opportunities and constraints from a UK perspective. Recent developments in integrated water management, ecosystem services and multifunctional land use provide new opportunities for ‘getting more for less’. These can range from seeing all forms of water as a resource, exploiting opportunities to contribute to the green and blue infrastructure agendas, resilience to climate and other changes. This paper draws on international experience as to how water-sensitive urban design can deliver opportunities; mitigate the urban development challenges; implement and support institutional, regulatory and practical opportunities and demonstrate the benefits of taking a water-sensitive urban design approach in the UK. The key requirements for delivery are highlighted and a proposed vision for water-sensitive urban design in the UK outlined.
Multi-geophysical Investigation of Geological Structures in a Pre-selected High-level Radioactive Waste Disposal Area in Northwestern China
Authors: An Zhiguo , Di Qingyun , Wang Ruo , Wang Miaoyue
Published: June 2013

A potential high-level radioactive waste (HLRW) disposal site in northwestern China was investigated to determine its suitability for such a use. The site is primarily covered with well-developed metamorphic granite rocks. The primary targets for geological repositories are three granite rock masses (I, II, and III). Only surface geological data were available from previous studies. The objective of this study was to evaluate the quality of the rock mass and identify any weak geological structures that could jeopardize this future underground repository. We used gravity and aeromagnetic data on a large scale to study the regional geological structures within and around the three rock masses. Subsequently, in 2009, a controlled source audio-frequency magnetotelluric (CSAMT) survey was conducted to study rock mass I in more detail.

This paper introduces three-dimensional (3-D) tomography imaging of gravity and aeromagnetic data. 3-D tomography imaging was carried out on previously collected gravity and aeromagnetic data and, using the results of different depth slices, we evaluated the rock mass quality and interpreted the geology. The aeromagnetic depth slices show that at about 1-km deep in rock masses I and III there is a high magnetic susceptibility body, possibly caused by an early granite intrusion. The deep granite or metamorphic rocks appear as weak `magnetic anomalies in the magnetic slices. The results also indicate that rock mass II is more deeply buried and smaller than rock masses I and III. In the upper crust, inhomogeneous density variations have a strike direction consistent with that of the structure revealed in the aeromagnetic data.

For rock mass I, we designed a CSAMT line to map small-scale outcropped faults to depth, and identify any hidden faults or weakened zones in the subsurface. Because of the highly resistive ground, we improved the electrode contact conditions by pouring salt water on both the transmitting and receiving electrodes. During data processing, we applied Hanning filtering to reduce static effects from lack of electrical homogeneity near the ground surface, and through experimentation found an optimum filter length to achieve maximum static effect reduction. Sounding data were inverted for geoelectrical cross sections using a two-dimensional smooth-model inversion method. Inversion artifacts were suppressed by imposing the model smoothness constraint. Several important results were revealed by the inversion: the inversion section correctly recognized two fractures at the surface, and also identified two new faults that were not observed during the previous geological survey. The inversion profile suggests that the narrow factures and deformation bands extend to a great depth. With further drilling confirmation, this interpretation will enhance understanding of the deep geological structures at the HLRW disposal site.
Hydraulic Fracturing with Water-Based Fluids in Water-Sensitive Formations
Authors: Salazar F. , Rachid R. , Jimenez J. , Milne A. , Ali Syed
Published: June 2013

Ecuador is producing oil today from mature fields with increasing water cut, and most of the reservoirs are subhydrostatic with permeability ranging from 10 to 1000 md and significant clay content (mainly kaolinite and glauconite) in the formation matrix. As a consequence of the increasing workover interventions and fluid invasion due to the depleted reservoir conditions, there was need to stimulate the wells to be able to bypass the damage zone. In the past, it was common to lose completion fluid into the reservoir, resulting in a 20% to 50% reduction in production or even in extreme cases killing the well when the completion fluid was incompatible with either reservoir fluids or formation clays.

Historically matrix acidizing treatments have been perfomed in an attempt to remove formation damage or to increment production, with limited success. Matrix acidizing treatments are not sufficient to fully remove the damage because of the high clay content, and in many cases, the damage cannot be removed by just treating the critical matrix. Conventional hydraulic fracturing treatments were then tried as a means to bypass the damage. However, some of the wells treated showed positive skin factors following the fracture treatments.

The wells in which hydraulic fracturing had proved unsuccessful were studied in more detail to understand the reason why hydraulic fracturing resulted in a positive skin. It was concluded from the formation mineralogy and core flow testing that the fracturing treatments were unsuccessful due to a reduction in the formation permeability due to the mechanical plugging and movement of the kaolinite or disrupted mica in the pore throats. The reduction in the matrix permeability results in skin damage in the faces of the fracture. The fracture-face damage or skin can also be caused by fluid loss from the fracturing fluid through the fracture faces, which creates an additional drop in pressure that may further reduce the productivity of the well. The impact of these effects on the productivity of a treated well depends on the reservoir characteristics and mineralogy, fracture geometry, extent of fluid leakoff into the reservoir, and the viscosity of the fracturing fluid filtrate. The magnitude of these effects and resulting additional pressure drop generally increases with increasing reservoir permeability.

To eliminate or mitigate the fracture-face skin effect in water-sensitive formations, a new treatment incorporating a prepad of a viscosified blend of chelants and acid was field tested. By adding this stage into the fracturing treatment design, the retained matrix permeability was increased to +/- 70% of the undamaged matrix permeability, resulting in negligible fracture-face skin. The productivity of fracturing treatments performed using this innovative technique resulted in negative skin factors and production ratios that exceeded expectations in water-sensitive and high clay content reservoirs.
Acidizing Sandstone Formations Using a Sandstone Acid System For High Temperatures
Authors: Zhou L. , Nasr-El-Din H. A.
Published: June 2013

Regular mud acid mixtures have been extensively used to stimulate sandstone formations; however, the use of this acid in a deep well has some major drawbacks, including high and uncontrolled reaction rate and corrosion to well tubulars. A single stage sandstone acid system (HF and a phosphonic acid) has been developed as an alternative to mud acid. Carbonate minerals in sandstone formations can cause formation damage. Therefore, there is a need to remove the carbonates to enhance the performance of this sandstone acid system.

In this study, the single stage sandstone acid systems with different HF concentration were examined to stimulate sandstone formation at high temperature. Berea (5 wt% clays) and Bandera (11 wt% clays) sandstone cores were used in the coreflood experiments. Coreflood experiments on sandstone cores were conducted at 300 °F at a flow rate of 2 cm3/min. The concentrations of Si, Ca, Al, Mg, and Fe in the core effluent samples were analyzed using Inductively Coupled Plasma (ICP). 0.6M GLDA (pH= 3.8), 0.6M HEDTA (pH =3.8), and 9 wt% formic acid solution were evaluated to remove the carbonate minerals from Bandera sandstone cores.

Coreflood experiments showed the sandstone acid systems enhanced the permeability of Berea sandstone cores, and the optimum injection volume is 2.5 PV to keep the integrity of the cores at 2 cm3/min and 300°F. This acid system damaged Bandera sandstone cores severely at 300°F, which contain 16 wt% dolomite, and 10 wt% illite. Analysis of core effluent samples indicated that there was CaF2 precipitate in the core when the acid systems were pumped without preflush. Therefore, calcium carbonate in Bandera sandstone cores should be removed with preflush. GLDA, HEDTA and formic acid (9 wt%) were compatible with Bandera sandstone cores at low pH value, and formic acid was much more effective in remove carbonate in Bandera sandstone cores.
Effects of Total Suspended Solids on Permeability of Proppant Pack
Authors: Ye X. , Tonmukayakul N. , Lord P. , LeBas R.
Published: June 2013

Recently, interest in using produced water for hydraulic stimulation processes has greatly increased within the oilfield services industry. However, successful hydraulic fracturing operations using produced water have yet to reach their full potential. This is largely because of wide variance in water quality from such sources as bacterial content, suspended solids, scale, and precipitate potential. Among these, suspended solids are a major issue. Their presence can create severe problems by plugging the proppant's pore space. In this paper, the effects of total suspended solids (TSS) on proppant permeability using a novel benchtop device (Ye et al. 2009) are discussed. This apparatus imposes a controlled strain on the proppant pack while continually measuring its permeability up to a compressive stress of 7,100 psi. Another unique feature of this apparatus is the direct visualization of the proppant pack through a polycarbonate window. Images taken have been analyzed, which provides quantitative information about the relationship between relative permeability and fine particles invasion. Results using produced water samples revealed that electrocoagulation (EC) treatment would increase the permeability up to 40%, depending on the proppant and produced water source. Extensive data analyses and flow visualizations are presented, demonstrating the effects of TSS on the permeability of proppant packs.
Fracturing Fluid Conductivity Damage and Recovery Efficiency
Authors: Weaver J. D. , Liang F. , Schultheiss N. C.
Published: June 2013

The primary purpose of hydraulic fracturing is to provide highly conductive paths from the reservoir to the wellbore. This is accomplished by pumping fracturing fluids at extreme pressures to create fractures in the reservoir rock. In addition to creating the fractures, the fluid is used to carry proppant into the fractures to keep them open for flow after the pressure is relieved.

The performance of fracturing fluids is generally determined by their ability to 1) create fracture width and length with minimal loss of energy caused by friction, 2) efficiently transport proppant through the tubulars and deep into the fracture, 3) keep the proppant suspended to help distribute proppant vertically in the fracture, 4) break on a planned schedule to permit rapid and efficient flowback without producing back the proppant, and 5) perform all of these goals economically.

There are several good methods available to determine fluid efficiencies, proppant transport properties, and fluid break times that are important to a stimulation engineer when designing fracture treatments. However, there are few methods available that adequately simulate post-fracturing fluid recovery that provides the expected well cleanup rate, efficiency, and impairment of proppant pack conductivity.

This paper presents the development of a laboratory method that permits the determination of post-fracture cleanup parameters of a fluid system under realistic reservoir conditions. Fluid rheology and fluid recovery data are presented that compare commonly used fracturing fluid systems with a variety of breakers and proppant types. The use of this data should aid stimulation engineers in the selection of the optimum fluid system, breaker package, and proppant combination for specific reservoir conditions.
Self-Diverting Acid for Effective Carbonate Stimulation Offshore Brazil: A Successful History
Authors: Neto A. T. , Silva C. A. , Torres R. S. , Farias R. L. , Prata F. G. , Souza L. A. , Pereira A. Z. , Calderon A. , Sandes E. F.
Published: June 2013

The stimulation history in offshore Brazil is undergoing into a deep transformation. The requirements of technology, before focused on sandstone reservoirs demand, are being expanded by the need for techniques to stimulate carbonate reservoirs, specially the pre-salt carbonates. In this scenario, a self-diverting acid system based on a viscoelastic surfactant (VES) technology was introduced for carbonate reservoir stimulation.

The Self-Diverting VES (SD-VES) promotes viscosity development when the acid comes in contact with the carbonate formation. The mechanism of viscosity development is simple: In concentrated acid, the system presents low viscosity, which results in friction reduction while pumping; however, when the fluid reacts with the formation and the acid concentration decreases, the micelle spherical structures combine, transforming into rod-like micelles that convert to a 3-D structure, which increases the fluid viscosity. The high viscosity generates a temporary barrier across the high-injectivity zones, diverting the subsequent fluid to treat other reservoir zones.

Generally the SD-VES is associated with several placement techniques that aid in achieving good treatment distribution through the entire producer interval. Regardless of the placement technique applied, the SD-VES is generally used as the main acid fluid and is bullheaded into the well. Because of its rheological behavior, the SD-VES is pumped as a single fluid during bullheading, aiming to achieve formation stimulation and good treatment distribution throuth the entire productive interval.

Since the SD-VES was introduced in 2009 to treat carbonate reservoirs in offshore Brazil, more than 40 wells have been treated using the system in the various acid placement techniques presented in this paper. Three case histories are presented to better illustrate the different scenarios where the SD-VES was applied.
Evaluation of Formation Damage/Remediation Potential of Tight Reservoirs
Authors: Elkewidy Tarek Ibrahim
Published: June 2013

Oil or gas effective and relative permeabilities can be reduced to a great extent due to the invading liquid phase of the drill-in or completion fluid, contrary to the misconception that formation damage is less of a concern in lower permeability reservoirs (e.g., less than 5 md). Many laboratory, well logging, and formation tester data proved that mud filtrate (both from water- and oil-based muds) can deeply invade the formation enhanced by capillary forces. This will result in reduction of the oil or gas effective permeability, especially if the formation exhibits fluid emulsion blocks and phase trapping. Unfavorable interaction of the filtrate with the reservoir fluids and rock minerals can generate emulsions and precipitates. The same scenario may occur in hydraulically fractured formations.

An integrated multidisciplinary approach is pursued in this study to evaluate formation damage/remediation potential of low permeability reservoirs. The techniques involve different formation evaluation methods including core analysis, well logging, and well testing along with various cleanup scenarios. Furthermore, results from petrographic analysis and laboratory experiments (Micro and Macroscopic scales) are related and correlated with the larger Mesoscopic and Megascopic scales of well logs and well testing, respectively.

Results of these efforts lead to the following technical contributions; a) Delineation of the low permeability heterogeneous reservoirs, e.g. the Leduce carbonates, into their hydraulic units. b) Determination of the undamaged formation absolute and relative permeabilities along with the diameter of filtrate invasion. c) A rule of thumb is to minimize or prevent damage from taking place by selecting a drilling fluid that quickly forms an easily removable mudcake. d) Cleaning up damage due to water filtrate may be accomplished by just flowing the well and can be accelerated using solvents or surfactants. However, once the formation reaches its irreducible water saturation, remediating water saturation below the irreducible value may not significantly improve its permeability.
Three-Dimensional Sonic and Anisotropy Data to Provide Effective Fracture Treatments
Authors: Smith Charles H. , Hamilton Layne , Bashkirtseva Alena
Published: June 2013

Hydraulic fracturing has become a common completion treatment or stimulation treatment for horizontal wells; however, effectiveness of these treatments, in terms of improved production, is difficult to predict. One reason for uncertain production results is poor fracture initiation in the reservoir, which can be caused by drilling-induced damage or a formation's natural resistance to breakage.

Several approaches have been attempted to solve this problem and provide a better return on completion investment. One approach that has achieved strong initial results is the use of dipole sonic logs to determine closure stress. From closure stress, formation breakdown pressures can be determined, which are used to design more effective treatments and place them more efficiently in the well and reservoir, where breakdown pressures are lower. This paper presents research to validate this approach.

Two wells were selected in the same area and geologic setting. The first was completed using standard processes for this asset. A dipole sonic log was run in the horizontal wellbore before beginning the completion. Results from the sonic log were compared to the fracture treatments after the fact.

In a second vertical pilot well, information was acquired, including elemental capture, dipole sonic, and nuclear magnetic resonance, with the objective of determining rock texture, vertical and horizontal rock mechanical properties, effective porosity, and permeability. A dipole sonic was then run through the horizontal section of this second well to determine anisotropy. This knowledge was used to select perforation and stage points in the horizontal well and design fracture treatments.

Two additional reservoirs are included in this paper where dipole sonic logs were run only in the horizontal cased hole but reference nearby pilot holes. Results from all cases were positive; therefore, it is believed that this technique can be useful in any reservoir.
Foam And Scale Inhibitor Squeeze With Natural Gas: A Lifeline For Water Flooded And Damaged Gas Well
Authors: Rauf O. , Gerdes S. , Lummer N. R.
Published: June 2013

It is commonly seen that water accumulation and near wellbore damage leads to the loss of production. This phenomenon had also been observed in many gas fields in Germany. Five years ago foam & scale inhibitor batch (FSIB) technique was applied but it remained successful only in few fields as only fluid pumping with chemicals was the part of this technique.

Foam & scale inhibitor squeeze (FSIS), a novel technique was developed that involves natural gas pumping along with chemicals. It has been done by using high pressure mobile natural gas compressor. This technique is based on several steps during which foam water as based along with additives (like scale inhibitors, chelating agent etc.) comingled with natural gas are being pumped in the well. In final step compressed natural gas is also bullheaded to displace the pumped chemicals in to the formation.

FSIS has been successfully applied to bring water flooded and damage wells (with no production) back to production. Many targets can be achieved in one job by applying this technique like: removal of water in near wellbore region, cleaning from scales, well kick-off to production in quick time after treatment (due to comingled and displaced gas and reduced hydrostatic pressure), less down time, economy and no effect of produced gas quality.

This report would elaborate the difference between the two techniques Foam & scale inhibitor Batch (FSIB) and Foam & scale inhibitor squeeze (FSIS). Job procedure and benefits associated with these techniques will also be presented along field results.
Evaluation of RPMs in Heterogeneous Cores - Fracture Scale do Matter
Authors: Restrepo Alejandro , Lopera Sergio , Ocampo Alonso , Castro Eber
Published: June 2013

From theoretical work related to production mechanisms to the development and application of preventative and remedial technologies, water control has been and continues to be a broadly studied subject in the oil industry. Although the last word appears to be elusive and trial and error approaches have led to mixed results, there are recent encouraging advances especially in complex systems such as those related to fractures where water arrival can seriously compromise field development plans.

The present work focuses on the study of polymer based RPMs in different petrophysical systems. Laboratory tests at reservoir conditions are documented for homogeneous, macro fractured and micro fractured sandstone cores representative from fields located in Colombian foothills, where active tectonics and compositional fluids are present.

According to relative permeability mesurements taken before and after treatment, RPMs performance can widely vary depending on the type of rock and water saturation range. Results suggest that a critical Sw exists in macrofractured systems above which RPM "swithches" its behaviour promoting higher Kw. Although this effect is not noted in homogeneous nor microfractured cores, there seems to be higher benefits in the last one in terms of kw reduction and final recovery.

Observations derived from this study are now of key value for planning and executing field tests throughout subject fields allowing to clasiffy target areas and tune expected benefits based on laboratory results.
Return Permeability: When A Single Number Can Lead You Astray In Fluid Selection
Authors: Offenbacher Matt , Luyster Mark , Gray Leigh , He Wenwu , Leonard Russell , Stephens Mike
Published: June 2013

Historically, return permeability testing has become a standard to establish minimally damaging fluid properties. This single number is typically focused upon for its simplicity, however the testing procedure and intermediate data provide much more than just this value. The process provides insight into formation damage mechanisms and their overall impact on potential well performance. The variable nature of procedures and apparatus as well as interpretation of data is regularly limited to the percent return permeability - a potentially misleading value in fluid selection. A thorough review of existing literature and experience on recent projects details the recognized potential for variability as well as misperceptions in interpreting results. Examples of test data are reviewed to capture damage mechanisms where fluid formulations require further optimization. In many cases conclusions are drawn and fail to identify why differences in the percent return permeability yields a particular result. Prior published work assessing formation damage tends to focus upon formation characteristics. This paper details the results and data typically provided with these analyses. These data include: fluid loss, initial return permeability, and techniques used to determine the damage mechanism. Test results are reviewed to illustrate where the risk of unwarranted conclusions occurs. Recommendations for appropriate analysis of both final return permeability and intermediate data are provided for optimized fluid design. Through the techniques discussed, testing procedures have the potential to provide the maximum insight into fluid-formation interactions on the core material available.
Risks, Mitigation and Management of Wax Production Chemistry in a SAGD Environment: Downhole to Surface and Beyond
Authors: Shepherd Andrew G. , Vandeweyer Tony , Rafik Dena , van Kins Simon , Baksteen Erik , Cheong Anthony
Published: June 2013

Precipitation, deposition and gelling of paraffins are common production chemistry challenges associated with upstream exploration and production. In this paper the different steps used to identify the wax-related issues from project to start-up and steady state are discussed. The development is a field under steam-assisted gravity drainage (SAGD). Critical to the mapping of production chemistry risks are the many specific analytical and modeling procedures employed. During the project stages, the main risks identified were: wax precipitation downhole and potential gelling of the export pipeline. Clear strategies were put in place to manage both these potential problems. During the start-up of the field, a number of wells were suffering from poor inflow performance. A downhole deposit was retrieved and analyzed. This was identified as wax, with an increase in paraffin distribution compared to the parent crude oil. Successful mitigation of wax deposition downhole was achieved for a selective number of wells using a combination of fluid treatment and extended soak time. This suggests wax deposition is occurring in the near wellbore area. Noticeable effects of SAGD drive on the wax properties of individual well samples are observed reflected in increasing pour points (for wells where heat has broken through). No effect yet is observed on the export crude oil. Long-term surveillance for wells and the facility will continue to rely on wax measurements in combination with tubing head temperatures. Mitigation options will be further developed for continuous operational improvement.
An Investigation of the Plugging Mechanisms in a Slotted Liner from the Steam Assisted Gravity Operations
Authors: Romanova U. G. , Ma T.
Published: June 2013

A slotted liner recovered from the well 07P05 located in the McMurray formation of the Long Lake area, Canada, where Nexen Inc. is producing bitumen with the Steam Assisted Gravity Drainage (SAGD) technology, was investigated in the study. The study was aimed to determine the conditions of the liner and assist Nexen in identifying the mechanisms of the liner failure. The study included a physical examination of the liner, direct measurements of the liner aperture, permeability measurements, epoxy impregnation of the selected sections of the liner, and the analysis of plugging material and surface of slots. The study results show the corrosion and/or plugging and/or poor slot specification result in effective apertures being different than the specification. The study also shows that pressure drops across the liner sections are small, likely due to removal of the surface plugging clay and fines. The plugging material consists of large amount of corrosion products, significant amount of iron sulphide, clay fines (mostly kaolinite), and some quartz grains. The examination of the slots show that films of the plugging material consisting of predominantly corrosion products and clay, gradually choking slots.
Type Curves for Injectivity Decline
Authors: Kalantariasl Azim , Duhan Sundeep , Bedrikovetsky Pavel
Published: June 2013

Injectivity decline is a wide spread phenomenon for seawater injection, produced water re-injection, disposal of produced water in aquifers and whatever waterflood project with a poor quality injected water. The typical injectivity decline curves appear for impedance (normalised reciprocal to well index) versus PVI. They consist of linear growth interval for deep bed filtration, another interval for the linear growth during formation of external filter cake, ending up with the stabilised value. This paper discusses the stabilised impedance calculation.

The mathematical model for the stabilised impedance is based on the torque balance of attaching (electrostatic and permeate) and detaching (drag, lifting and gravity) forces exerting upon a particle on the cake surface. If compared with the previous models, this paper accounts for electrostatic force and for varying non-unit value of the permeate factor. It was shown that the electrostatic force can exceed other forces and cannot be neglected. Moreover, the permeate factor can highly exceed one. Accounting for the two above factors completely change the order of magnitude for the lever arm ratio as obtained from the stabilised injectivity, if compared with previous works. The lever arm was also calculated from the particle deformation by permeate and electrostatic forces using Hertz theory, resulting in the same order of magnitude as that obtained from well data. It validates the model for stabilised injectivity.

Analysis of 35 injector histories results in probabilistic distributions for 5 injectivity impairment coefficients, including the lever arm ratio. It provides with fully predictive tool for injectivity decline.
Drilling Depleted Reservoirs - Is Formation Damage Sometimes a Good Thing?
Authors: Byrne Michael , Oyovwevotu Joy , Retalie Ian
Published: June 2013

Drilling depleted reservoirs can present many challenges from a drilling, completion and production perspective. Formation damage due to increased overbalance for example, is well documented as a particular concern. But could we see some drilling benefit from increased formation damage at higher overbalance?

This paper will outline experience in drilling depleted reservoirs and discuss the impact of formation damage on well productivity, injectivity and drilling performance. In several examples, the benefits of formation damage outweigh the deficits and we propose a planned approach for future wells in depleted reservoirs. Formation damage is measured in the same way as for assessment of the productivity or injectivity impact but the data is applied to a different challenge. The additional pressure drop in the near wellbore area as a result of formation damage can protect the reservoir and minimise fracture propagation. Whilst formation damage can be important in depleted reservoirs it is largely irrelevant if wells cannot be drilled. With the method proposed wells can be planned, drilled, completed and produced (or injected).

The paper proposes better understanding of the impact of formation damage in order to enable drilling, completion and development of depleted reservoirs or intervals and proposes a new methodology to use formation damage as part of a well planning workflow.
Formation Damage Matters, Sometimes - Quantification of Damage Using Detailed Numerical Modeling
Authors: Byrne M , Rojas E
Published: June 2013

Formation damage sometimes has a significant impact on well productivity or injectivity. Much of the work undertaken to mitigate against formation damage serves to qualify the impact of damage and for example, determine the least damaging introduced fluids. Whilst qualification is important, quantification of damage impact is a much greater prize.

Taking advantage of increased computational power and speed, Computational Fluid Dynamics (CFD) has been applied in the last five years to numerically model and quantify flow restriction in wells and the near wellbore (Byrne et al 2009). This process enables better prediction of the real impact of formation damage on well productivity. The process has been applied to many real fields and wells and in this paper we present some of the latest revelations on the impact of formation damage on well performance.

In order to illustrate the simplicity of the process a sensitivity analysis of typical formation damage restrictions has been applied. This demonstrates the impact of different formation damage quantities and depths on different well trajectories and lengths in the same reservoir. In some cases the impact of damage that could be classed as "severe" in a laboratory test has little impact on eventual well productivity. In others the damage has a profound impact on well performance. With the obvious caveat that every well is different, we propose some consistent guidelines on the impact of damage based on our numerical modelling work.

Modelling of this kind does not reduce the necessity to understand or simulate damage, instead it enables focus where formation damage has greatest impact and creates a greater awareness of the importance of damage to our industry. Through increasing use of appropriate modelling, uncertainty is reduced and better wells can be drilled and completed.