bluuebunny/crossref_metadata_2025 huggingface dataset:
Crescimento e absorção de nutrientes pelo feijoeiro adubado com cama de aves e fertilizantes minerais
Authors: Lourenço Késia Silva , Corrêa Juliano Corulli , Ernani Paulo Roberto , Lopes Letícia dos Santos , Nicoloso Rodrigo da Silveira
Published: June 2013

O feijoeiro é tradicionalmente cultivado em pequenas propriedades, onde é comum o uso de dejetos animais para adubação das culturas. Como é uma cultura de ciclo curto, os nutrientes precisam estar disponíveis logo após a germinação, o que nem sempre acontece quando a fertilização ocorre a partir de fertilizantes orgânicos. Neste trabalho, objetivou-se avaliar a eficiência de diferentes camas de aves em relação aos fertilizantes minerais na produção de matéria seca e na liberação de nutrientes para o feijoeiro, em casa de vegetação. O experimento foi conduzido em 2010, com amostras de um Latossolo Vermelho distroférrico com 16 g kg-1 de matéria orgânica, 1,9 e 84 mg dm-3 de P e K, respectivamente, e pH 6,0. Adotou-se delineamento experimental de blocos casualizados com 10 tratamentos e cinco repetições. As unidades experimentais foram constituídas por vasos com 14 dm³ de solo e cinco plantas de feijão, do cultivar BRS Requinte, durante 60 dias. Os tratamentos consistiram de cinco camas de aves compostas pelos seguintes materiais: palha de milho, bagaço de cana-de-açúcar, palha de pastagem natural, areia ou acícula de Pinus, formulações de nutrientes (NPK, NP, PK e NK) e um testemunha, sem nenhum fertilizante. Os fertilizantes minerais com P proporcionaram maior produção de matéria seca da parte aérea (MSPA) e de raízes (MSRA) do feijoeiro do que as camas de aves, por causa da maior liberação para o solo de N e P disponíveis. Dentre as camas estudadas, aquela constituída por areia foi a que proporcionou os maiores valores de MSPA e de MSRA. As plantas fertilizadas com as camas de aves acumularam, em média, 58,6 % do N e 59,0 % do P, em relação às fertilizadas com os tratamentos que continham N e P minerais. A taxa de recuperação pelas plantas de N e K foi maior para os nutrientes aplicados na forma mineral do que na orgânica. As camas de aves podem ser utilizadas como fertilizantes para a cultura do feijoeiro desde que sejam suplementadas com N e P minerais.
Erosividade das chuvas associada a períodos de retorno e probabilidade de ocorrência no estado do Rio de Janeiro
Authors: Machado Roriz Luciano , Carvalho Daniel Fonseca de , Rouws Janaina Ribeiro Costa , Gomes Daniela Pinto , Eduardo Eliete Nazare
Published: June 2013

O conhecimento da erosividade das chuvas associada à probabilidade de ocorrência e ao período de retorno pode contribuir para o planejamento conservacionista de uma região, em médio e longo prazo. A fim de gerar informações para melhor utilizar modelos e controle da erosão, dados de chuvas de 30 séries pluviográficas e pluviométricas, abrangendo 25 municípios, entre 1933 e 2006, foram estudados quanto à adequação das séries e do cálculo da probabilidade de ocorrência teórica (P) e período de retorno (T) da erosividade das chuvas (EI30 e KE>25), para o Estado do Rio de Janeiro. Foi feita a espacialização do potencial erosivo associado aos períodos de retorno de 2, 5, 10, 20, 50 e 100 anos para todo o Estado. A erosividade anual média (EI30) ou fator R da USLE para qualquer localidade no Estado do Rio de Janeiro pode ser igualada ou superada pelo menos uma vez, em média, em um período de 1,8 a 2,1 anos, com faixa de 48,5 a 54,9 % de probabilidade de ocorrência teórica. As localidades que apresentam maior erosividade associada aos períodos de retorno estão situadas nas mesorregiões Metropolitanas e em partes das mesorregiões Sul e Centro Fluminense. Foi possível identificar de oito a 12 regiões homogêneas, quanto à distribuição espacial da erosividade associada aos períodos de retorno de dois para 100 anos no Estado. De modo geral, a maior variação da distribuição espacial da erosividade apresenta-se na faixa de período de retorno de dois a cinco anos.
Equação preditora de idade óssea na iniciação esportiva através de variáveis antropométricas
Authors: Cabral Breno Guilherme de Araújo T. , Cabral Suzet de Araújo Tinôco , Vital Roberto , Lima Kenio Costa de , Alcantara Tabata , Reis Victor Machado , Dantas Paulo Moreira Silva
Published: June 2013

INTRODUÇÃO: Atualmente o desempenho esportivo tem se desenvolvido de forma rápida e concreta, exigindo, dessa forma, uma eficiente evolução das diferentes áreas das ciências do esporte, oferecendo o suporte cientifico necessário à continuidade desse fenômeno. OBJETIVO: O estudo em questão teve como objetivo desenvolver uma equação matemática preditora de idade óssea de jovens atletas, com base em variáveis antropométricas. MÉTODOS: Para se alcançar o resultado final foram medidas dobras cutâneas, perímetros corporais e diâmetros ósseos, idade cronológica e idade óssea. O tratamento estatístico utilizou a correlação entre as variáveis, a regressão linear múltipla com modelagem backward. RESULTADO: Se obteve como resultado final um modelo de equação que explica 75,4% da variação da idade óssea com r = 0,868 e R² = 0,754, utilizando idade cronológica, estatura, dobra tricipital, perímetro corrigido de braço e diâmetros de fêmur e úmero. CONCLUSÃO: Concluiu-se a partir dos resultados, que esse tipo de modelo revela valores aproximados aos observados através da radiografia de mão e punho, tornando-se importante na observação do estágio maturacional através de testes de fácil aplicabilidade por profissionais da área esportiva.
Incidência de lesão musculoesquelética em jogadores de futebol
Authors: Almeida Pedro Sávio Macedo de , Scotta Ângelo Pontes , Pimentel Bárbara de Mattos , Batista Júnior Sedenir , Sampaio Yasmin Rodrigues
Published: June 2013

INTRODUÇÃO: Sendo o futebol um esporte de grande popularidade em todo o mundo e principalmente no Brasil, vários estudos procuram formar um perfil das lesões e dos jogadores mais propensos a elas; porém, este tipo de estudo é raro na região norte do País. OBJETIVO: Analisar a incidência de lesões musculoesqueléticas nos jogadores de futebol profissional do Clube do Remo, Belém, PA. MÉTODOS: Foram analisados 27 jogadores de futebol profissional do Clube do Remo, durante o Campeonato Paraense de futebol de 2010. Os dados foram coletados através da verificação dos prontuários e aplicação de um questionário semicodificado para os atletas; posteriormente foi realizada a análise estatística. RESULTADOS: Ao analisar a amostra, verificou-se que a maioria das lesões foi de contraturas e contusões, os locais corpóreos mais acometidos foram a coxa e o joelho e a posição em campo mais lesionada foi a de meio de campo. CONCLUSÃO: Ocorreram várias lesões musculares; por isso, é necessário um acompanhamento da equipe multiprofissional, já que este tipo de lesão não ocorre devido a trauma e sim pelos movimentos que os jogadores são impostos durante os jogos e treinos.
Relação entre a personalidade e lesões musculares em atletas de tênis de campo
Authors: Keller Birgit , Braga Ana Maria , Coelho Ricardo Weigert
Published: June 2013

INTRODUÇÃO: A personalidade de um indivíduo é o resultado de uma complexa rede de influências de diversos fatores independentes como a constituição biológica e psicológica, além das influências do meio social, ambiental e cultural em que vive. Ela é a integração dessas partes que interagindo formam o todo. OBJETIVO: Verificar se existe relação causa-efeito entre traços de personalidade, sexo e lesão no esporte. MÉTODO: A amostra foi composta por 60 atletas com idade média de 15,6 (DP =1,5) anos, sendo 35 atletas do sexo masculino e 25 atletas do sexo feminino pertencentes à Categoria Infanto-Juvenil, participantes de torneios de tênis de campo da Federação Paranaense e Catarinense. Para a coleta de dados foi utilizado o Inventário Fatorial de Personalidade - IFP. Para tratamento dos dados utilizou-se uma MANOVA e uma ANOVA a um nível de p < 0,05. RESULTADOS: Apresentaram significância para a variável lesão com Agressão (p = 0,01) e Heterossexualidade (p = 0,00). Para a variável sexo, houve diferença significativa com Intracepção (p = 0,02); Afago (p = 0,02); Dominância (p = 0,004); Autonomia (p = 0,03); Heterossexualidade (p = 0,00). CONCLUSÃO: A agressividade é um importante traço de personalidade a ser considerado para ser controlada para prevenir e diminuir as incidências de lesões em atletas de tênis.
Distribuição de subgrupos com base nas respostas fisiológicas em jogadores profissionais de futebol pela técnica K Means Cluster
Authors: Novack Luiz Fernando , Nascimento Vitor Bertoli , Salgueirosa Fabiano de Macedo , Carignano Luís Felipe , Fornaziero André , Gomes Elton Bonfim , Osiecki Raul
Published: June 2013

INTRODUÇÃO: A preparação física no futebol necessita estar sempre em constante atualização em virtude das exigências presentes no futebol contemporâneo. OBJETIVO: Verificar a sensibilidade da técnica estatística K Means Cluster na distribuição de grupos com base nas respostas fisiológicas pertinentes ao futebol. MÉTODOS: Os atletas foram submetidos a avaliações antropométricas para determinar o percentual de gordura (%G) e de massa magra (MM), teste incremental em esteira para obter o VO2 máximo (VO2máx) e a velocidade de limiar ventilatório (VLim), bem como testes de campo para a agilidade (AG) e o salto vertical (SV). Os dados foram analisados pelo teste de Kruskal-Wallis e a distribuição dos grupos foi desenvolvida pela técnica de K Means Cluster conforme as semelhanças dos jogadores com essas variáveis fisiológicas, assumindo o nível de significância de p < 0,05. RESULTADOS: Os grupos diferiram significativamente somente com relação ao SV (p < 0,001), MM (p < 0,001), VLim (p = 0,011) e VO2máx (p = 0,029) indicando que para estas variáveis, os atletas necessitam ser distribuídos em grupos. Entretanto, o %G e a AG (p = 0,317; p = 0,922), respectivamente, não foram diferentes, indicando que essas variáveis podem ser aprimoradas em todos os atletas de maneira coletiva. CONCLUSÃO: Tendo em vista os resultados encontrados, podemos concluir que a distribuição dos grupos pela técnica K Means Cluster pode ser realizada utilizando as respostas fisiológicas dos atletas no intuito de otimizar e priorizar o treinamento físico das principais necessidades apresentadas em comum pelos atletas, independentemente da função tática exercida em campo.
Estimativa do equivalente metabólico (MET) de um protocolo de exercícios físicos baseada na calorimetria indireta
Authors: Coelho-Ravagnani Christianne de Faria , Melo Flávia Carolina Lemos , Ravagnani Fabricio C. P. , Burini Franz Homero Paganini , Burini Roberto C.
Published: June 2013

OBJETIVO: O objetivo do estudo foi determinar o gasto energético (GE) em termos de gasto calórico e equivalente metabólico (MET) de duas sessões de um protocolo de exercício. MÉTODOS: Quinze indivíduos adultos (51,0 ± 5,5 anos) realizaram as sessões de exercício (80min), compostas por (aquecimento, caminhada e flexibilidade; Sessão A) e (aquecimento, caminhada e resistência muscular local; Sessão B). A frequência cardíaca (FC) foi medida durante cada parte da sessão. Em laboratório, foram medidos, em dias diferentes, o consumo máximo de oxigênio (VO2max), durante repouso e exercício (usando a FC média obtida nas aulas), por calorimetria indireta. O MET dos exercícios foi obtido dividindo VO2 em exercício (mL.kg-¹. min-¹) pelo VO2 em repouso (mL.kg-¹.min-¹). O GE dos exercícios foi calculado por: MET x Peso (kg) x Tempo (min)/60. RESULTADOS: Os resultados foram analisados por ANOVA com teste post hoc de Tukey (p < 0,05). Resultados: Um MET para este grupo foi de 2,7 ± 0.1mL.kg ¹. min-¹. O valor médio de MET nos exercícios foi de 4,7 ± 0,8 (aquecimento), 5,8 ± 0,9 (caminhada) e 3,6 ± 0,7 (flexibilidade) na sessão A, e 4,6 ± 1,2 (aquecimento), 5,6 ± 1,0 (caminhada) e 4,8 ± 1,0 (resistência muscular localizada) na sessão B. O custo de energia foi similar entre as sessões (A: 398 ± 86,7 kcal e B: 404 ± 45 kcal; p > 0,05). Nenhuma atividade foi classificada como vigorosa (> 7 METs). Não houve diferença no VO2 entre caminhada (15,6 ± 2,8 ou 15,4 ± 2,6 mL.kg-¹.min-¹) e resistência muscular localizada (13,2 ± 2,9 mL.kg-¹.min-¹) embora ambos tenham sido superiores (p > 0,05) aos exercícios de flexibilidade (10,1 ± 2,2 mL.kg-¹. min-¹). CONCLUSÃO: O protocolo proposto atinge a atividade física necessária para adultos saudáveis, para melhorar e manter a saúde, por sua estrutura, intensidade moderada, duração, frequência e gasto calórico.
A Relative Permeability Modifier for Water Control: Candidate Selection, Case Histories, and Lessons Learned after more than 3,000 Well Interventions
Authors: Vasquez Julio , Eoff Larry
Published: June 2013

Excessive water production can detrimentally affect the profitability of hydrocarbon producing wells and limit their economic life. Relative permeability modifiers (RPMs) were introduced to the oil and gas industry more than two decades ago as an option to selectively reduce water production. This type of treatment became appealing to operators because of its simplicity of deployment requiring no zonal isolation (i.e., bullhead-type treatments). However, RPM treatments have their limitations, and proper candidate selection is the key to a high success ratio. This paper discusses the application of a unique RPM system developed for water control.

This RPM system is based on a hydrophobically modified water soluble polymer (HRPM) that, once adsorbed to the surface of the rock, selectively reduces water effective permeability with little to no damage to oil or gas production. The hydrophobic modification to the base polymer chain adds unique associative properties to the system. In contrast to porosity fill-sealants (i.e., crosslinked polymer gels), HRPM treatments only provide a restriction to water flow. The following parameters are discussed: (1) HRPM performance testing, (2) candidate selection criteria, (3) design considerations and best practices for field implementation, and (4) case histories.

To date, more than 3000 treatments have been performed with this HRPM system. A wide variety of case histories are highlighted in this paper discussing different types of reservoirs, wellbore completions, and water production mechanisms, among others. In addition to water control, the application of this HRPM system has been extended to hydraulic fracturing, acid stimulation, and overbalanced workover interventions. Case histories are examined. Often, RPM treatments are applied in reservoir/wellbore conditions outside of their operating capabilities. One of the main objectives of this paper is to assist operators with the candidate selection process for this particular HRPM treatment.
Case Study Analysis of Formation Damage Induced by Brine Workover Fluid on Burcioaia Reservoir (Romania) and Research on Damage Removal Methods
Authors: Dragomir A. , Precupanu L. , Arsenoiu V. , Tippel P. , Radulescu G. , Sava D. , Zosmer C. , Tudorin O. C.
Published: June 2013

Brine workover fluid has a confirmed damage for gas condensate wells generated by both water blockage and fines presented in it. Studied reservoir is a gas condensate field where workover operations performed for replacing downhole equipment have induced severe damage.

Formation damage for brine workover fluid was tested on core for both hydrocarbon flowing phases (condensate and gas) and revealed up to four times decreasing in permeability.

Laboratory research was then oriented to identify the best solution to remove induced damage. It was tried to identify how much of damage was induced by water blockage and how much by fines present in workover fluid. Tests revealed a good recovery of permeability for gas by using alcohol/surfactant fluids but not close to original permeability. On the other hand correctly formulated mud acid solution have removed induced damage and increased the permeability up to three times more than original permeability.

Results have been implemented on field Burcioaia and foam acidizing was used successfully in field tests. For very long perforated intervals foam was used as diverter. In some cases only acid solution was foamed and in other cases also neutral foam was pumped in slugs in between acid stages.

Case histories for performed removing damage jobs are also presented.
Dynamic Fluid Erosion on Filter Cakes
Authors: Opedal Nils van , Cerasi Pierre , Ytrehus Jan David
Published: June 2013

The erosion on filter cakes was studied. A water based drilling fluid was placed in a pressure cell and filter cakes where formed under both static and dynamic filtering conditions. The erosion was studied on static formed filter cakes by varying the propeller rotation velocity and rotation duration. The measured response was the filter cake weight and thickness and these two parameters exhibited a slightly different development with regard to erosion. The dynamic filter cakes were formed at different propeller rotation velocity. Increasing fluid movement during the filter cake formation lead to thinner and denser filter cakes which were less prone to erode compared to filiter cakes formed under static and low fluid motion movement.
Long-Term Dynamic Flow Testing of Proppants and Effect of Coatings
Authors: Aven Nevil Kunnath , Weaver Jim , Loghry Ray , Tang Tingji
Published: June 2013

The intention for using proppants in a fracture is to create a hydraulically conductive pathway for reservoir fluids that is open to flow and stays open. Most propped fractures, however, experience a loss of flow capacity with time. Several mechanisms have been identified that contribute to this loss, such as mechanical failure of proppant grains, proppant embedment, fluid residue damage, formation spalling, and others. Recently, fracture diagenesis has been proposed as an additional mechanism that can significantly contribute to the slow loss of fracture conductivity.

Previous attempts to quantify the degree of diagenetic activity have been made under conditions of stress and temperature, but without dynamic fluid flow. This paper presents an automated experimental setup that enables long-term (six or more months) dynamic flow testing of multiple proppants simultaneously at reservoir temperature conditions.

This apparatus was used to determine the rate of diagenetic activity on some sand and ceramic proppants with slow, continuously flowing formation water. The results are compared to static cell test results. In addition to a baseline comparison of the proppants under consideration, specialized coatings aimed at reducing the rate of diagenetic reactions are evaluated. Data for four proppants and six coatings subjected to 350°F flowing simulated formation water for six months are presented. Proppants were analyzed for changes in mechanical and compositional properties after 0, 2, and 6 months by scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and crush strength. Dynamic permeability was monitored periodically throughout the test period along with produced fluid ionic content as determined by inductively coupled plasma (ICP) testing. Mass changes of each test proppant were measured.

Results presented in this paper should be helpful to the stimulation engineer responsible for selecting proppants desiring sustained fracture conductivity. A detailed description of an automated laboratory method in which proppants can be evaluated for long periods of time with little human interaction is presented.
Emulsified Chelating Agent: Evaluation of an Innovative Technique for High Temperature Stimulation Treatments
Authors: Sayed M. A. , Nasr-El-Din H. A. , De Wolf C. A.
Published: June 2013

Acid treatments in wells drilled in carbonate reservoirs aim to remove the damage, and increase the permeability in the area around the wellbore. Regular HCl used to be the main stimulation fluid; however at high temperatures, HCl causes excessive corrosion, rapid acid spending and face dissolution. For high temperature treatments, the alternatives are limited; including chelating agents, such as GLDA (glutamic acid-N,N-diacetic acid) and HEDTA (N-hydroxyethyl-ethylenediamine-triacetic acid).

This paper discusses the evaluation of an innovative technique to formulate a new emulsified chelating agent that can be used for high temperature stimulation treatments. GLDA (pH = 3.8) of 38 wt% initial concentration was selected to formulate the emulsified GLDA (EGLDA). The EGLDA was formulated using a cationic emulsifier, with final GLDA concentration and volume fraction of 20 wt% and 0.7, respectively. The viscosity of the new EGLDA was measured at temperatures up to 300°F using an HPHT rheometer. The reaction of the EGLDA and limestone rock was studied using a rotating disk apparatus at temperature of 230°F. Coreflood experiments were performed using low permeability Indiana limestone core samples and emulsified GLDA at a temperature of 300°F and injection rate of 2.0 cm3/min.

EGLDA is a non-Newtonian shear-thinning fluid, where the viscosity can be represented by the power-law model. The emulsified GLDA achieved a viscosity of 57.5 cp at 100 s-1 and 75°F. The EGLDA was stable up to 300°F, and the apparent viscosity at 10 s-1 shear was found to be 40 cp. The reaction rates of EGLDA with calcite were in the range of 6.2×10-8 to 1.2×10-7 gmole/cm2.s, less by 2 orders of magnitude than those of 15 wt% HCl emulsified acid formulated by 1.0 vol% emulsifier and reacted with calcite at a temperature of 230°F. The coreflood experiments performed using EGLDA and Indiana limestone cores, indicated that emulsified GLDA was able to enhance the permeability of the core by a factor of 3.7 times. From the work done, the EGLDA achieved low reaction rates with no face dissolution at high temperature, and this will results in better stimulation treatments, especially in high temperature wells.
Impact of Waxy Crude Oil on Appropriate Crude Conditioning Techniques and Core Flood Testing for the Maari Oilfield
Authors: Kidd Samuel , Stalker Robert , Graham Gordon , Einzinger Christian , Duff Lauchie , Hobbs George
Published: June 2013

The Maari Field is located 50 miles off the coast of South Taranaki, New Zealand. In this paper, we will present details of a laboratory test programme which was conducted to assist in the design of removal and mitigation treatments for flow assurance in the Maari oilfield. Main operating partner OMV initiated laboratory testing of a series of carbonate and sulphate scale dissolver and inhibitor treatments for use in the field, examining formation damage aspects potentially associated with the use of such fluids in the field. The waxy nature of the reservoir crude oil presented challenges for core flood testing, in particular the design of appropriate crude oil conditioning techniques to provide representative samples and core flood protocols to omit potential laboratory artefacts.

The Maari crude oil contains heavy oil fractions, high wax content and a high wax appearance temperature. Standard field sampling, laboratory conditioning and sub-sampling methods can result in loss of light fractions through evaporation and thus a crude oil sample weighted towards the heavier molecular weight oil fractions. Also there is potential for heavy end losses due to insufficient conditioning temperature, filtering and sub-sampling. Appropriate protocols were therefore required to condition the crude oil to a field representative state for use. Heavy oil fractions within the crude oil presented challenges for conducting effective core flood tests. Oil particulates and heavy fractions can induce wax deposits and fines mobilisation effects that can be considered test artefacts obscuring formation damage test results. Alternative test methods were therefore designed to ensure the crude conditioning methods and core flood tests are as representative as possible of the oilfield whilst also providing clear and accurate formation damage assessment.

This paper therefore presents a laboratory strategy designed to account for the aforementioned challenges alongside laboratory test results and subsequent recommendations for crude and core conditioning and core test protocols under similar conditions.
Field Case Histories of a Non-Damaging Guar Alternative for Linear Gel Application in Slickwater Fracturing
Authors: Sun Hong , Zhou Jia , Cutler Jennifer , Royce Tom , Nelson Scott , Qu Qi
Published: June 2013

Slickwater hydraulic fracturing is commonly used to stimulate unconventional formations, including many shale reservoirs. Large volumes of water and additives are pumped downhole at high rates to propagate the fractures and delay proppant settling. At high flow velocities, proppants in friction reducer-based fluids can be very abrasive, leading to reduced service life for fracturing equipment. Slickwater fluids also often lead to poor proppant transport and placement, resulting in reduc ed stimulation efficiency. Traditionally, medium- to high-viscosity guar linear gels are used to mitigate these challenges, which may leave behind polymer damage and can also be affected by periods of guar shortages.

An alternative solution is presented here to deliver the desirable viscosity with a novel synthetic polymer system. The new polymer incorporates easily breakable linkages in its backbone, susceptible to conventional oilfield oxidizer breakers under downhole conditions. The system also shows fast hydration with almost instantaneous viscosity development, and thus allows rapid and easy adjustments of fluid viscosity and rapid switching between polymers when needed. Laboratory testing demonstrated that the polymer solution breaks in the presence of oxidizer breakers at elevated temperatures and leaves no formation or fracture damage. Many successful treatments using this system have been pumped and confirmed the above benefits, and significantly improved production of the trial wells over the offset wells has been observed. The new system greatly simplifies the overall process of hybrid hydraulic fracturing applications, making the new polymer an effective and economical option to address the ongoing guar availability and pricing challenges.

This paper will show the laboratory data, discuss several successful field applications of the new fluid system and present production data to demonstrate its real-world performance and effectiveness.
Impact of Charge Type Used in Perforation on the Outcome of Matrix Acid Treatment in Carbonate Formations: Comparative Study
Authors: Rabie Ahmed I. , Nasr El-Din Hisham A. , Hardesty John T. , Clark Nathan G. , Bell Matthew R.
Published: June 2013

Perforation is the most common way to establish effective communication between the reservoir and the wellbore in wells completed with casing. Although perforation with shaped charges has become the dominant method for completion, conventional shaped charges do not always provide deep and clean-enough tunnels that result in the required productivity and/or facilitate subsequent stimulation treatments.

Therefore, the objectives of this work are to utilize the Perforation Flow Cell (PFC) and the Perforation Treatment Cell (PTC), both developed by GEODynamics, to investigate the impact of using reactive liner shaped charges on the outcome of matrix acidizing treatments and to compare the performance of reactive and conventional charges for different charge types and loads.

Cream Chalk cores with 7 in. diameter × 24 in. length were perforated with two weights of reactive and conventional charges (15 and 23 g) under simulated downhole conditions using two designs of charges; deep penetration (DP) and good hole (GH). All cores were initially saturated in odorless mineral spirit (OMS) and the same fluid was used to flush the core before and after the acidizing step. Porosity and pre-shot (initial) permeability were measured.

After perforation, post-shot permeability was reported and the cores were CT-scanned to visualize and measure the geometry of the perforation tunnels. 15 wt% HCl was used for the acidizing step at 200°F and the effluent samples were periodically collected to measure Ca, Mg, Fe, Al, and metal ions that are present in the core, tubulars, cement, and shaped charge material in the perforation assembly. Cumulative acid pore volume and acid injectivity were reported. CT scans were performed again after acidizing to assess the wormhole morphology obtained with various types of charges.

Experimental results showed that reactive charges create tunnels with more effective (open) length when compared to the equivalent conventional charge, especially at the tip of the tunnel. As a result, stimulation treatments were enhanced and less acid pore volume and time to breakthrough were required. These results were confirmed by chemical analysis that showed higher calcium and metal ion concentration in the effluent samples when the conventional charge was used. CT-scanning after treatment showed a dominant wormhole created from the tip of the perforation tunnel when the reactive charges were used compared to multiple and deviated/branching wormholes with the conventional charges.
Quality Control of Particle Size Distributions
Authors: Kumar Arunesh , Chellappah Kuhan , Aston Mark , Bulgachev Roman
Published: June 2013

Two important aspects often overlooked in the design of bridging solids packages for drilling fluids are: a) obtaining accurate particle size measurements, and b) allowing for the influence of particle attrition. This paper explores both aspects and illustrates, using field data, the challenges and positive impact on productivity (or injectivity) of getting the distribution right.

Commonly-used bridging solids were sized in the laboratory by sieve analysis and laser diffraction techniques and the results compared. The two methods gave similar results for particles in the range ~ 50–500 μm, but there was a significant discrepancy for larger particles. Since sieving best reflects the functional purpose of the particles (to block pores or fractures) it is suggested that sieve analysis should be the preferred method for particles with a d90 above about 500 μm.

Studies of particle grind down (attrition) showed the critical attrition parameters to be the particle type (material), the initial particle size, and the shear rate. Large particles ground down faster and to a greater extent than smaller ones. In the laboratory tests, large 1400 μm particles were found to reduce in size by up to 80% compared with only a 5% reduction in size for 300 μm sized particles over a 30 minute test period. Fluid viscosity also had an influence on attrition but particle concentration appeared to have only a marginal effect.

Two field case studies are presented. These used small bridging particles for pore sealing to minimize formation damage in two drill-in fluid applications. A grind-down effect was observed in case 1 (water based mud) which used 50 μm marble particles, and so steps were taken to restore the size distribution. There was no apparent attrition effect in case 2 (oil mud) which used a mixture of smaller 20 μm marble particles and barite. Careful management of the fluids led to a successful outcome in terms of well performance in both cases.
Evaluating Flowback Proppants for Proppant Diagenesis in Shale
Authors: Raysoni Neelam , Sarda Anjali
Published: June 2013

The concept of proppant diagenesis has been discussed for several years. Detailed studies and analysis have been conducted to better understand hydrothermal degradation of alumina-based proppant, which has sometimes led to a significant loss of fracture conductivity. Also, testing has been performed in laboratories at high temperatures to accelerate the rate of reactions over short durations. Many of these tests have been reported in the literature and have provided significant insight to various geochemical reactions that occur within the fracture and the possibility of the proppant pack being unstable under laboratory conditions.

However, it is equally important to look for evidence of proppant pack instability under reservoir conditions. Attempts were made to evaluate proppants that were flowed back during production from fracture stimulated reservoirs. A sample of a manufactured proppant obtained for evaluation was taken from a well that had a sandstone-dolomite lithology, while natural sand (quartz) proppant samples were obtained from different fracture stimulated wells where shale was the dominant lithology (Barnett shale). Various evaluation techniques were used, such as looking at pH of the fluids, inductively coupled plasma (ICP), X-ray diffraction (XRD), X-ray fluorescence (XRF), and loss on ignition/total organic content (LOI/TOC). Scanning electron microscope coupled with energy dispersive X-ray (SEM-EDX) proved to be beneficial for detailed analysis and helped improve understanding of the structures (growths) on the proppant surface. Extensive efforts were made to finalize best-method testing procedures along with different analytical methods.

Efforts were also made to validate some of the results generated in the laboratory under near-reservoir conditions of temperature and test duration. This paper presents data from the analysis for flowback manufactured proppants and fracturing sands that confirm the phenomena of proppant diagenesis under reservoir conditions, as well as laboratory conditions that replicate pseudo-reservoir conditions as closely as was practical.
New Treatment Method for Enhancing Propped Fracture Conductivity: A Laboratory Study
Authors: Nguyen P. D. , Rickman R. D. , Weaver J. D. , Vonk T. Z. , Loghry R. A.
Published: June 2013

Much effort in hydraulic fracturing technology has focused on fracturing fluid development to maximize its proppant transportability, while keeping potential polymer damage to a minimum. This paper presents the results of a laboratory study that demonstrates and quantifies the effectiveness of a new method for enhancing and sustaining proppant pack conductivity.

The approach uses an aqueous-based surface modification agent (ASMA) as part of the pad fluid stage to treat the fracture faces before placement of proppant into the fractures. ASMA treatment forms a thin film that becomes tacky and hydrophobic on both the fracture face and formation particulates. This coating causes the proppant to adhere to the created fracture faces, which can help to mitigate proppant settling inside a hydraulic fracture, resulting in improved vertical distribution of proppant within the fracture. It was also determined that ASMA treatment helps reduce polymer damage and results in the binding of fines that are generated during the fracturing process.

This study used Berea sandstone and various shale core samples that were split along the core length to create artificial fracture faces. These fracture faces were then treated with an ASMA solution, followed by immersion in proppant fluid slurry, and were then reassembled for core flow testing under closure stress. A permeability comparison of the fractured cores, with and without ASMA treatment and proppant slurry exposure, demonstrated a dramatic increase in the fractures of the treated cores. The results show that ASMA treatments are applicable to most types of formations, including shales, sandstones, and coals. The experimental results are presented by examining the reliability of ASMA treatments on the fracture faces during formation of the fracture and the ASMA's effectiveness at forming a partial monolayer of proppant for enhancing well productivity.
Physics Mechanisms of Enhanced Recovery By Fines-migration-assisted Waterflooding (Laboratory Study)
Authors: Zeinijahromi A. , Bedrikovetsky P.
Published: June 2013

Several different physics mechanisms yield in enhanced oil recovery with low salinity water flooding: reduction in interfacial tension, alteration of wettability, mobilization and size exclusion of fines. In this paper the laboratory study of fines migration and straining during low salinity waterflooding is performed. First, single-phase flood with piece-wise salinity decreasing was carried out to assure the presence of movable fines in the rocks under investigation. The, sequential waterflooding by formation water, restoration of the connate water with oil and waterflooding by fresh water, were undertaken. The laboratory tests have been performed under the conditions of large scale approximation, so Welge-JBN methods for determining relative phase permeability were applicable. The relative permeability curves were obtained from the coreflood data. The obtained curves show that the permeability for water increases at low water saturations while it decreases at high saturations. The non-monotonic behavior of relative permeability for water is the main finding of this paper.
CT Scan Study of the Leak-Off of Oil-Based Drilling Fluids into Saturated Media
Authors: Frequin Dorien , Bedrikovetsky Pavel , Zitha Pacelli L.J.
Published: June 2013

Leak-off of oil-based drilling mud into liquid-saturated cores was studied both theoretically and experimentally. First a simple model for the leak-off process was developed extending an earlier analysis of static filtration into unsaturated cores. Then CT scan aided static filtration experiments were performed in dry, brine-saturated and oil-bearing cores, simulating possible reservoir saturation regimes. Formation of external filter cake and internal filtration of solid particles were visualized and leak-off volumes were measured as function of time. At the end of the experiments the formed external filter cake and internal particle deposition were characterized with the aid of an Electron Scanning Microscope. Using drilling fluids containing carbonate particles it was found that leak-off volumes for saturated cores are larger than for unsaturated cores. It was observed further that leak-off volumes increase with particle size, i.e. consistently with a more permeable external filter cake and limited internal filtration. Leak-off volumes decreased when using smaller hematite particles or barite particles having wider particle distribution size.
An Experimental and Simulation Study of Asphaltene-Induced Permeability Impairment under Natural Depletion Condition
Authors: Khalifeh Mahmoud , Kharrat Riyaz , Bagherzadeh Hadi , Izadi Milad
Published: June 2013

Asphaltene deposition is one serious problem in many of Iranian oil reservoirs. So, a deeper understanding of this phenomenon is essential to prevent its related formation damage and increasing ultimate production through selecting a proper planning. The major goals of this study are (a) investigation of asphaltene deposition on rock surfaces under natural depletion condition during dynamic flow tests, and (b) simulation study of asphaltene-induced permeability damage by using commercial software and evaluation of its strengths and weaknesses.

To extend the results of this work, asphaltene deposition and simulation study performed on both carbonate and sandstone rocks. The results of dynamic flow experiments show asphaltene deposition is a continuous process causing permeability impairment and is also partially reversible. Simulation results indicate good matching of the experimental data at final steps of the experiments and it means that software should be modified respect to modeling of asphaltene deposition. In addition, surface deposition and entrainment mechanisms are more important in carbonate rocks than sandstones while pore plugging mechanisms depends on the pore size distribution of the rock and it may play same role in carbonate and sandstone rocks. The simulation model considers constant values for adsorption and plugging coefficient, while these coefficients are changing during experiment. All the tests are performed and simulated in accordance to reservoir condition and oil production rate of wells.
Investigation of Effective Mechanisms in Permeability Reduction Due to Asphaltene Deposition through Porous Media
Authors: Khederzadeh M. , Ostadrezaei S. , Kharrat R. , Bagherzadeh H. , Mahdavi S. , Khalife M.
Published: June 2013

Asphaltene deposition during natural depletion and miscible gas injection is a common problem in matrix and near well-bore region of oil reservoir throughout the world. This problem may lead to formation damage and reduction in production. Understanding the permeability reduction mechanisms during different processes of production is vital in optimizing production and injection processes in order to minimize the formation damage.

In this study, asphaltene deposition during natural depletion and miscible CO2 injection was conducted through core flooding tests at reservoir conditions. The natural depletion was done at several pressure steps while CO2 injection was performed simultaneously with live oil into the core sample. The CO2 mole percent in injected fluid was chosen to be more than the onset value. According to static experiments the onset of asphaltene precipitation due to CO2 injection was equal to 10% mole percent for the desired oil.

The main purpose of this paper is to consider asphaltene deposition mechanisms including surface deposition, plugging and filtration cake formation during primary depletion and CO2 injection. Consequently these mechanisms were investigated using related models. Based on results, plugging became dominant mechanism of permeability impairment, although surface deposition may exist during the tests. The pressure drop diagrams confirm the most pressure reduction was encountered at the entrance of the core; hence permeability reduction at initial part was more severethan the final portion. The results of this work may be helpful for understanding of permeability reduction mechanisms related to asphaltene deposition during natural depletion and CO2 injection in this heavy oil reservoir.
Formation Damage Due To Iron Precipitation In Carbonate Rocks
Authors: Assem A. I. , Nasr-El-Din H. A. , De Wolf C. A.
Published: June 2013

Iron precipitation during matrix acidizing treatments is a well-known problem. However, extensive literature review highlighted that no systematic study was conducted to determine where this iron precipitates, the factors that affect this precipitation and the magnitude of the resulting damage.

In this paper, the effect of iron precipitation in the acidizing operations is studied. HCl solutions (5 – 10 wt%) containing 5,000 to 10,000 ppm of Fe3+ were used for these experiments. The effect of varying acid concentration, initial core permeability, core length, temperature, and flow rate was studied. Coreflood experiments were conducted on 6 and 20 in. long Indiana limestone cores over a wide range of permeabilities and up to 300°F. In these experiments, 0.5 PV of acid solution was injected. The cores were scanned after treatments using a CT scanner and cut to better determine the location of iron deposition. The core effluent samples were analyzed for iron and calcium concentrations using ICP-OES.

Results showed a significant amount of iron precipitated on the injection face of the cores and the sides of wormholes, i.e. where the contact occurs between the acid and the rock, producing a minimal or no gain in the final permeability, which indicated severe formation damage. The damage increased with the increase of the amount of iron in solution. At higher temperatures and flow rates, the damage was significant. Core length didn't affect the degree of damage. This paper will discuss the results obtained and give recommendations on whether to use iron control agents in the field or not.
Integral Completion Technique for Heavy Oil Thermal Recovery
Authors: Yue Hui , Pang Wei , Duan Youzhi , Zhang Tongyi , He Zuqing , Deng Dawei , Hou Qian , Du Juan , Zhao Xu , Feng Xiaoxu
Published: June 2013

Nowadays, the annual heavy oil production is more than 15 million tons in China and more than 60% of which are developed by cyclic steam stimulation (CSS) technology. Vacuum insulated tubing (VIT) with thermal packer is the mostly adopted thermal insulation manner during steam injection progress. This usually leads to two major problems. One is casing integrity issues like casing crack, casing collapse, and cement sheath damage induced by thermal packers's failure or cyclic casing as Well as cement heating. Another problem is frequent injection and production strings transformation, and this leads to operation cost increasing and high temperature production time wasting especially when CSS is of short cycle in super-heavy oil or thin thickness reservoirs.

In order to solve the two problems, the vacuum insulated casing (VIC) and relevant integral completion technique are researched taking well completion, heat insulation and hereafter production into consideration simultaneously rather than separately. This completion technique injects steam by VIC while not by VIT and produces in normal tubing, thus eliminates the thermal packer's failure problems, meanwhile, simplifies the injection and production pipe conversion process and saves production time. VIC's heat loss and steam quality along wellbore are compared with that of VIT. The related techniques like cementing, perforation while adopting VIC are also studied.

Field trials in Henan oilfield in China verify this completion's suitability for CSS in heating insulation, production performance and economics compared with normal method of CSS. The completion provides a long-term Well integrity solution for thermal Well recovery not only by CSS, also by other thermal manners like SAGD. Also, it can play an important role in heat proof exploitation of other resources like gas hydrate and geothermal energy.
Auditor Fees and Auditor Independence—Evidence from Going Concern Reporting Decisions in Germany
Authors: Ratzinger-Sakel Nicole V. S.
Published: June 2013

This study examines the potential for non-audit services to impair auditor independence using going concern modifications as a proxy for audit quality. While prior research has focused primarily on Anglo-Saxon environments, this study focuses on Germany because of the country's unique reporting attributes and lower litigation risk when compared to Anglo-Saxon settings. Based on a sample of financially stressed manufacturing companies during the period 2005–2009, the results do not suggest that German auditors are less independent when the level of non-audit fees is high. However, there is some evidence that Big 4 audit firms are less likely than their non-Big 4 counterparts to issue a going concern emphasis-of-matter paragraph for engagements characterized by both relatively high levels of non-audit fees and financial stress.
REDEEM: A Pragmatic Trial to Reduce Diabetes Distress
Authors: Fisher Lawrence , Hessler Danielle , Glasgow Russell E. , Arean Patricia A. , Masharani Umesh , Naranjo Diana , Strycker Lisa A.
Published: June 2013

OBJECTIVE

To compare three interventions to reduce diabetes distress (DD) and improve self-management among non–clinically depressed adults with type 2 diabetes mellitus (T2DM).

RESEARCH DESIGN AND METHODS

In REDEEM, 392 adults with T2DM and DD were randomized to computer-assisted self-management (CASM), CASM plus DD-specific problem solving (CAPS), or a computer-administered minimal supportive intervention. Primary outcomes were Diabetes Distress Scale (DDS) total, the Emotional Burden (EB) and Regimen Distress (RD) DDS subscales, and diet, exercise, and medication adherence.

RESULTS

Significant and clinically meaningful reductions in DD (DDS, EB, and RD) and self-management behaviors occurred in all three conditions (P < 0.001), with no significant between-group differences. There was, however, a significant group × baseline distress interaction (P < 0.02), in which patients with high baseline RD in the CAPS condition displayed significantly larger RD reductions than those in the other two conditions. RD generated the most distress and displayed the greatest distress reduction as a result of intervention. The pace of DD reduction varied by patient age: older patients demonstrated significant reductions in DD early in the intervention, whereas younger adults displayed similar reductions later. Reductions in DD were accompanied by significant improvements in healthy eating, physical activity, and medication adherence, although not by change in HbA1c.

CONCLUSIONS

DD is malleable and highly responsive to intervention. Interventions that enhance self-management also reduce DD significantly, but DD-specific interventions may be necessary for patients with high initial levels of DD. Future research should identify the minimal, most cost-effective interventions to reduce DD and improve self-management.