bluuebunny/crossref_metadata_2025 huggingface dataset:
Whiskers de fibra de sisal obtidos sob diferentes condições de hidrólise ácida: efeito do tempo e da temperatura de extração
Authors: Teodoro Kelcilene B. R. , Teixeira Eliangela de M. , Corrêa Ana C. , Campos Adriana de , Marconcini José M. , Mattoso Luiz H. C.
Published: September 2011

Neste trabalho, os efeitos de diferentes condições de tempo e temperatura usados para a preparação de whiskers de sisal foram investigados com o objetivo de se determinar a influência destes parâmetros experimentais na morfologia, cristalinidade e estabilidade térmica dos materiais preparados. A obtenção dos whiskers deu-se após o pré-branqueamento da fibra de sisal com solução alcalina de peróxido de hidrogênio. A fibra branqueada foi submetida ao processo de hidrólise com solução de ácido sulfúrico 60% (m/m) sob três diferentes condições de temperatura e tempos de extração: 45 °C e 60 minutos (WS45_60); 45 °C e 75 minutos (WS45_75) e 60 °C e 30 minutos (WS60_30). Os whiskers foram caracterizados quanto à morfologia por microscopia eletrônica de transmissão (MET), quanto à cristalinidade (DRX), carga superficial (potencial zeta) , teor de enxofre (análise elementar) e quanto à estabilidade térmica por termogravimetria (TGA). Os resultados mostraram que os whiskers de sisal apresentaram comprimento e diâmetro médios e 210 nm e 5 nm respectivamente. Devido à alta aglomeração dos whiskers, diferenças relativas às características dimensionais não puderam ser determinadas. Os resultados obtidos revelaram uma forte dependência da cristalinidade final dos whiskers com a temperatura e tempo de extração. O uso de temperatura mais alta (60 °C) associado a um menor tempo de extração (30 minutos) resulta em whiskers com boa estabilidade térmica (235 °C), maior cristalinidade e sem o comprometimento da estrutura cristalina da celulose.
O Sistema Único de Saúde como paradigma nas representações sociais dos cirurgiões-dentistas
Authors: Camargo Sérgio Xavier de , Nakama Luiza , Cordoni Junior Luiz
Published: September 2011

Este estudo se propôs a verificar se o Sistema Único de Saúde (SUS) é reconhecido pelos cirurgiões-dentistas como paradigma para a prática profissional. Trata-se de uma pesquisa qualitativa que analisou as representações sociais do SUS desses profissionais. O grupo de estudo reuniu dentistas com atuação profissional vinculada aos serviços públicos de Saúde, especificamente servidores públicos e professores universitários, sendo constituído por três casos: profissionais do serviço público tradicional de Londrina (PR); profissionais da Estratégia Saúde da Família (ESF) de Curitiba (PR); docentes de faculdades de Odontologia de Londrina (PR). Os resultados evidenciaram três possibilidades: desconhecimento do SUS; conhecimento e ceticismo; conhecimento e Utopia. Conclui-se que o SUS não é plenamente reconhecido como referencial para a atenção odontológica pelos cirurgiões-dentistas, e que sua adesão ao projeto SUS se dá apenas na contingência da associação entre conhecimento do SUS e crença pessoal em sua viabilidade.
Resiliência e socialização organizacional entre servidores públicos brasileiros e noruegueses
Authors: Carvalho Virgínia Donizete de , Borges Livia de Oliveira , Vikan Arne , Hjemdal Odin
Published: September 2011

O estudo objetivou analisar a relação entre a resiliência e a socialização organizacional junto a novos servidores de duas universidades públicas, em contextos culturais distintos, quais sejam Brasil e Noruega. As pesquisas em socialização organizacional apontam que a adaptação do indivíduo a um novo cargo e a uma nova organização tende a ser um evento estressor e a resiliência, que descreve os processos de superação do estresse e adversidades, poderia auxiliar a compreensão das diferenças nos resultados de socialização entre indivíduos numa mesma organização. Com base nesse presssuposto, a pesquisa foi desenvolvida junto a uma amostra de servidores docentes e técnico-adiministrativos brasileiros e noruegueses. Análises de regressão hierárquica foram desenvolvidas com o intuito de observar e comparar a capacidade preditiva da resiliência em relação à socialização organizacional. Os resultados demonstraram, de modo geral, que a resiliência contribuiu significativamente para explicar os resultados de socialização organizacional, independentemente da nacionalidade e da ocupação. A capacidade preditiva da resiliência em relação à socialização organizacional foi maior entre os novos servidores brasileiros. As implicações práticas, limitações e principais contribuições do estudo são discutidas, com sugestões para futuras pesquisas.
Violência no trabalho em saúde: análise em unidades básicas de saúde de Belo Horizonte, Minas Gerais
Authors: Batista Cássia Beatriz , Campos Augusto de Souza , Reis Juliana do Carmo , Schall Virgínia Torres
Published: September 2011

O presente estudo buscou investigar e compreender a violência vivenciada em unidades básicas de saúde (UBSs) da perspectiva dos processos de trabalho em saúde. A caracterização da violência nesse contexto, ao identificar e compreender os elementos da produção desse fenômeno, contribui para o seu enfrentamento. De cunho descritivo-exploratório, para a coleta de dados a pesquisa utilizou grupos focais e entrevistas com usuários, trabalhadores e gestores do serviço de saúde. O estudo mostra as consequências e os impactos da violência nas UBSs, retratando atitudes geradas pelos episódios de violência, bem como ações preventivas e mecanismos de apoio e suporte. A análise dos resultados marca a necessidade de se fortalecer não só a humanização e a gestão do trabalho em saúde, mas também a formação dos profissionais, atrelada às melhorias nas condições e no ambiente de trabalho e, consequentemente, na prestação dos serviços de saúde.
Dimensão psicossocial da atividade física na velhice
Authors: Santana Maria da Silva
Published: September 2011

Objetivou-se identificar as representações sociais da atividade física no contexto dos programas para a terceira idade no município de Natal (RN), Brasil. Foi feito um estudo transversal de abordagem quanti-qualitativa.Por conveniência, a amostra não probabilística foi constituída de 70 indivíduos. Na coleta dos dados, utilizou-se um questionário com dados sociodemográficos, associação livre de palavras e questão aberta. O núcleo central da representação foi composto por felicidade/saúde/dança e ginástica, revelando diferentes entendimentos e mostrando também que o conhecimento construído da atividade física assume um papel preponderante na vida de idosos, adquirindo, gradativamente, a representação de "vida com mais saúde e qualidade na velhice". A composição do núcleo central ao considerar elaborações mentais, emoções, práticas e explicações oriundas do cotidiano que se introduzem na constituição da representação social em foco, poderá influenciar as escolhas e estratégias de se desenvolver melhora nos padrões de saúde e na qualidade de vida dos idosos.
DNA Microarray Analysis Identifies CKS2 and LEPR as Potential Markers of Meningioma Recurrence
Authors: Menghi Francesca , Orzan Francesca N. , Eoli Marica , Farinotti Mariangela , Maderna Emanuela , Pisati Federica , Bianchessi Donatella , Valletta Lorella , Lodrini Sandro , Galli Giuseppe , Anghileri Elena , Pellegatta Serena , Pollo Bianca , Finocchiaro Gaetano
Published: September 2011

Meningiomas are the most frequent intracranial tumors. Surgery can be curative, but recurrences are possible. We performed gene expression analyses and loss of heterozygosity (LOH) studies looking for new markers predicting the recurrence risk. We analyzed expression profiles of 23 meningiomas (10 grade I, 10 grade II, and 3 grade III) and validated the data using quantitative polymerase chain reaction (qPCR). We performed LOH analysis on 40 meningiomas, investigating chromosomal regions on 1p, 9p, 10q, 14q, and 22q. We found 233 and 268 probe sets to be significantly down- and upregulated, respectively, in grade II or III meningiomas. Genes downregulated in high-grade meningiomas were overrepresented on chromosomes 1, 6, 9, 10, and 14. Based on functional enrichment analysis, we selected LIM domain and actin binding 1 (LIMA1), tissue inhibitor of metalloproteinases 3 (TIMP3), cyclin-dependent kinases regulatory subunit 2 (CKS2), leptin receptor (LEPR), and baculoviral inhibitor of apoptosis repeat-containing 5 (BIRC5) for validation using qPCR and confirmed their differential expression in the two groups of tumors. We calculated ΔCt values of CKS2 and LEPR and found that their differential expression (C-L index) was significantly higher in grade I than in grade II or III meningiomas (p < .0001). Interestingly, the C-L index of nine grade I meningiomas from patients who relapsed in <5 years was significantly lower than in grade I meningiomas from patients who did not relapse. These findings indicate that the C-L index may be relevant to define the progression risk in meningioma patients, helping guide their clinical management. A prospective analysis on a larger number of cases is warranted.
Influence of strain rates and loading histories on the compressive damage behaviour of concrete
Authors: Xiao Shiyun , Li Hongnan , Monteiro Paulo J. M.
Published: September 2011

Reported herein are the results of dynamic compressive tests of plain concrete specimens that were carried out with strain rates ranging from 10−5/s to 10−2/s. It is found that the compressive strength and the initial elastic modulus increase but the critical strain of concrete decreases with the increasing strain rate. The damage is defined as a reduction in the tangent modulus. The damage behaviours of concrete in the stress and strain space are investigated. Dynamic compressive load histories with different strain rates and different magnitudes are conducted on plain concrete specimens, and then the dynamic compressive damage tests of these specimens are also conducted. The effects of load histories on dynamic strain–strain curves, dynamic compressive strengths and the dynamic damage behaviour of concrete are studied.
Quantified Prediction of Technically Recoverable Resources for Unconventional Gas in Frontier Basins
Authors: Cheng Kun , Wu Wenyan , Holditch Stephen A. , Ayers Walter B. , McVay Duane A.
Published: September 2011

Along with the trend that unconventional gas resources are significant in meeting the great energy demand, it is intuitively needed to know their quantified volume, especially for the frontier basins where little exploration of unconventional resources has been undertaken. Following by our work in standardized investigation and quantified evaluation of recoverable resources in 25 mature North American basins, this paper further employs two methods to evaluate TRR (Technically Recoverable Resources) for unconventional gas in frontier basins: Source Rock method (SR) and Conventional TRR Input method (CTRRI).

The source rock method derives from the fact that source rock potential is the mechanism for generating hydrocarbons. Thus, using the relationships between TRR and source rock factors, the SR can adequately capture TRR from the indirect source rock evaluation. Combined with the ratio of unconventional and conventional hydrocarbons from our prior investigations, the method can further deduce conventional resources and unconventional resource volumes. Different from SR that provides an independent measure of TRR, conventional TRR input method requires known recoverable conventional resources for frontier basin. To calculate frontier basin TRR volume, the frontier basin’s recoverable conventional volume is divided by the fraction of conventional resources in the similar reference basin from basin analog system investigation (BASIN). It is noted that all the quantifications are regulated by the unified definition from petroleum resource investigation summary and evaluation (PRISE). Although the two methods estimate TRR for frontier basins in different conditions, the initial tests on three basins show that estimates by CTRRI are in accordance with those by SR. The results validate the resource triangle concept with distributions of different resource types (i.e., conventional oil, conventional gas, coalbed methane, shale gas, and tight gas sand), and can be further evaluated by more complete estimation of North American basin resources and international unconventional gas resources.
Injection Well – Producer Well Combinations in Application of Toe-To-Heel Steam Flooding (THSF)
Authors: Fatemi S. Mobeen , Jamaloei Benyamin Yadali
Published: September 2011

Toe-to-Heel Steam Flooding (THSF) is a new, short-distance thermal EOR process that achieves high recovery by virtue of its stable front propagation and producing mobilized oil directly into an active section of the horizontal producer. However, the wells configuration design for field development purposes still requires critical attention so as to ensure less environmental effect, efficient start-up and optimal oil recovery.

We present a series of 3-D simulated experiments using our developed PVT and rock model for KEM heavy oil reservoir in Iran to study the feasibility of THSF. Model has been validated with the published experimental observations. Then, different well configurations using Vertical (V) or Horizontal (H), Injector (I) and/or Producer (P) in direct line drive (VIHP, HIHP) or staggered line drive (VI2HP, 2VIHP) have been investigated.

The results show that THSF outperforms the conventional steam-flooding (VIVP). Different wells configurations of THSF showed superior performance over CSF in low-permeability KEM reservoir. A quasi-vertical steam condensation front exists that moved along the horizontal section in a toe-to-heel manner. Contrary to CSF, there was no or negligible steam override and channeling in different THSF configurations. Also, the horizontal injector configuration (HIHP) was the most efficient configuration for achieving rapid start-up, i.e., the shortest time to achieve stable front propagation. The single vertical injector configuration (VI2HP) was initially slow to achieve stable operation, due to the development of a much smaller steam zone. As the process continued, 2VIHP provided improved vertical, areal, and volumetric sweep efficiency associated with steam condensation front, which resulted in larger steam chamber and higher ultimate oil recovery. Finally, the sensitivity of THSF performance to the length of horizontal producer and traversal distance between producers (for VI2HP) or between injectors (for 2VIHP) has been simulated. These results indicate the optimized scenarios for the field development purposes.
"Red" vs. "Green" Scale Inhibitors For Extending Squeeze Life – A Case Study From North Sea, Norwegian Sector – Part II
Authors: Jordan M. M. , Sorhaug E. , Marlow D.
Published: September 2011

Over the years environmental legislation has forced changes in the types of scale inhibitor molecule that can be deployed in certain regions of the world. These regulations have resulted in changes from phosphonate scale inhibitor to polymer based chemistry, particularly in the Norwegian and UK continental shelf where phosphonates have either been on the substitution list or phased out for many applications. Over the past 10 years significant improvements in inhibitor properties of the so called "green" scale inhibitors have been made. However for one particular operator the squeeze application of this "green" scale inhibitor resulted in poorer than expected treatment lifetimes and significant operating cost due to the frequency of retreatment. To overcome the increasing operating cost an evaluation was made of the current treatment chemicals vs. the older more established phosphonate scale inhibitors. The results for the laboratory evaluation suggested that the older chemistry would extend treatment life and reduce operating cost. A case was made to the legislative authority who approved the use of the phosphonate scale inhibitor and field applications started. The squeeze lifetimes for the "red" phosphonate chemistry were shown to be significantly better than the existing "yellow/green" inhibitors. During the following months other scale inhibitors with improved environmental characteristics were developed and evaluated. One such molecule was shown to have similar coreflood retention than the applied "red" phosphonate and presented no formation damage. This paper presents the laboratory evaluation of the new scale inhibitor, illustrates the improvement observed with this new inhibitor via field squeeze treatment results from a well treated with both the "red" and new "yellow" environmental profile inhibitor chemicals.

This paper outlines the challenges with environmental legislation and how it has been possible to develop technical solutions (both in terms of environmental vs. safety issues and with new inhibitor chemicals) to meet the challenges of offshore scale control.
Thermal Gas Recovery from Coal Seam Gas Reservoirs Using Underground Coal Gasification
Authors: Salmachi Alireza , Haghighi Manouchehr , Bedrikovetsky Pavel , Xu Chaoshui
Published: September 2011

Gas production from coal seam gas reservoirs initiates by dewatering operation. Reservoir pressure reduction activates gas desorption and gas diffuses from micropores to macropores and consequently coal cleats. Dewatering operation provides the required driving force for the gas to desorb. In this research, in situ coal combustion is introduced as an enhanced gas recovery method.

Methane desorption from coal matrix is an endothermic process. Heating disturbs thermal equilibrium of the coal and more gas is released at higher temperature. A numerical transport model is applied to investigate thermal effect on gas desorption and diffusion in coal. Desorption-diffusion properties of the coal are modeled at non isothermal condition. Due to extremely low thermal conductivity of coal, convection is the dominant mechanism responsible for heat transfer in coal seam. Physical properties of the coal, Langmuir pressure and volume, porosity, density and initial diffusivity control methane mobility in thermal treatment.

Underground coal gasification which is a known technology in coal mining is proposed to be used as the source of heat. Controlled air injection into different wells in a coal seam reservoir can generate some hot spots in the reservoir. Heat flux generated from underground coal gasification sites has the potential to be transferred within the reservoir and locally increases reservoir temperature.

It is shown that the combination of underground coal gasification and coal seam gas production has the potential to develop a new technology that not only reduces the dewatering operation but also enhances gas recovery. Results show that thermal recovery can significantly increase gas desorption and diffusion in coal seam gas reservoirs. Thermal treatment causes higher desorption rate and ultimate recovery factor, lower water production and higher wellhead pressure.
Injectivity of Hydrophobically Modified Water Soluble Polymers for IOR: Controlled Resistance Factors vs. Flow-Induced Gelation
Authors: Dupuis Guillaume , Rousseau David , Tabary René , Grassl Bruno
Published: September 2011

The associative properties of Hydrophobically Modified Water Soluble Polymers (HMWSP) are known to be attractive for IOR, both because of their enhanced thickening capability as compared to classical water soluble polymers (for mobility control) and of their marked adsorptions on surfaces (for well treatments). In previous works, we have studied HMWSP injectivity in the dilute regime and shown, in particular, that adsorption played a major role in controlling injectivity. In this paper, we report new experimental data on the injectivity of HMWSP solutions in the semi-dilute regime.

From membrane filtration tests at imposed flow rate, we have firstly observed the formation of a filter-cake made of HMWSP physical gel, which remained largely permeable to polymers. This "gel-filtration" entailed modifications of the solution's viscosimetric properties, which can be explained by a rearrangement of the intra- and inter-chain hydrophobic bonds in the solution. The second part of our work consisted in injectivity tests in model granular packs. We have performed comparative experiments in porous media with variable permeabilities but at the same shear rate in the pore throats. Results show that, above a critical pore throat radius, rpC, HMWSP injection lead to stable resistance factors, with values close to the solution's viscosity, and that, below rpC, gelation occurs during injection. Furthermore, resistance factors measured on the cores internal sections evidence for in-depth gel formation. These insights could represent a new step towards the tuning of HMWSP injection conditions to the application targeted: mobility control or profile/conformance control.
High-Efficiency Boron Crosslinkers for Low-Polymer Fracturing Fluids
Authors: Sun Hong , Qu Qi
Published: September 2011

Guar-based fracturing fluids are the most commonly used fluids in reservoir stimulation. To provide high viscosity, boron crosslinked gels are preferred for their ability to heal after mechanical shearing and their favorable environmental properties. However, polymer loading determines amount of polymer residue, which can damage the formation and proppant pack. New, efficient boron crosslinking chemistry promises to reduce polymer loading in fracturing fluids and therefore minimize polymer residue and damage.

As a first step toward improving crosslinking efficiency, several diboronic acids were tested as model compounds in a series of guar solutions against boric acid. The results demonstrated that such chemistry could effectively reduce C* (critical overlap concentration for polymer chains), C** (critical entangle concentration for polymer chains) and Ccc (critical crosslinking concentration) of guar solutions. Further observations show crosslinking efficiency is a function of the crosslinking sites and chemical structures of the crosslinkers.

A new chemistry was developed to produce crosslinkers more cost-effective than the model compounds, whereby boron was incorporated via reactions between organometallic intermediates and boron reagents. Amines and polyimines were used as the base scaffolds and derivatized under mild conditions. The resulting compounds contain more crosslinking sites than the existing chemistry and can connect multiple guar chains to form a much more complex network for more efficient proppant transport.

A series of crosslinkers based on the new amine derivatization were synthesized and evaluated. This paper will show the lab test results of model compounds and new crosslinkers versus the conventional boric acid crosslinker. Analysis and discussion of the chemistry, crosslinking performance and economics will be presented.
Integrating Geological Characterization and Historical Production Analysis to Evaluate Interwell Connectivity in Tazhong1 Ordovician Carbonate Gas Field, Tarim basin
Authors: Hedong Sun , YanMei Xu , Xingliang Deng , Jianfa Han , Ying Shi , Linlin Lu , Wen Cao
Published: September 2011

Tazhong No. 1 gas field is a typical vug-fractured carbonate gas condensate reservoir with high heterogeneity and complex geological characteristics. This reservoir was discovered 5 years ago. There is an urgent need to study inter-well connectivity procedures for maximum oil /gas recovery. A detailed geological understanding of the reservoir is needed to gain a detailed reservoir dynamic description and determine the optimal recovery method for this oil reservoir. These are essential to having a successful operation, as well as reducing drilling uncertainties and improving the efficiency of oilfield management. An integrated static and dynamic workflow to determine connectivity is developed with the data collected from initial production stages of over 20 wells. This paper presents the concept of dynamic characterization of the vug-fracture carbonate gas condensate reservoirs, which mainly involves data processing, wellbore flowing pressure calculation, analytical well test analysis, numerical well test analysis, long-term production data history match and decline curve analysis, and performance prediction. In addition, the authors introduced history matching and pointed out the main reasons for the significant errors between actual data and simulation results. Several examples of triple medium condensate gas filed are given. Reservoir properties, such as permeability, skin factors, are determined. Reservoir volume and OGIP are estimated. These integrated dynamics results served as input data for connectivity with geological characterization. The results also show that the methodology is necessary, which can accurately identify gas reservoir parameters and decrease the non-unique. Based on the reservoir dynamic characterization, the wells network locations are optimized and good results are obtained in oil recovery.
Review on ESP Surging Correlations and Models
Authors: Gamboa Jose , Prado Mauricio
Published: September 2011

Head deterioration observed in electrical submersible pumps under two-phase flow is mild until a sudden performance breakdown is observed in the pump head curve at a certain volumetric gas fraction. This critical condition is termed surging. Consequently, the two-phase pump head is associated with whether the stage operates under conditions prior (mild performance deterioration) or after (severe performance deterioration) the surging point.

The surging, for engineering purposes, can be predicted by published correlations, but the lack of theoretical basis is a limiting factor for their application. Mechanistic models seem to be the proper alternative. But, the poor understanding of the physical mechanism that causes the surging hinders the development of such mechanistic models. This paper reviews some of these correlations and mechanistic models by comparing its predictions against experimental data acquired in a closed loop with water and air utilizing a commercial 24 stages ESP. The data cover a wide range of volumetric gas fraction, rotational speeds and intake pressures. As consequence of this analysis, two correlations have been formulated. The first correlation predicts the surging as function of rotational speed and fluid properties, while the second correlation intends to predict the homogenous boundary. This boundary encloses a regime in which the homogenous model works for predicting the ESP head curve.
Fully Coupled Chemical-Thermal-Poro-Mechanical Effect on Borehole Stability
Authors: Zhai Z.. , Abou-Sayed A..
Published: September 2011

Drilling instability is always one of the major challenges to drilling engineers. The temperature differential and pressure differential affect the borehole instability by altering the stress concentration at near wellbore region through poro-elastic and thermal elastic stresses. The temperature gradient and pressure gradient between the drilling fluid and formation change not only from conduction and convection, but also from interacting to each other. In low mobility formation such as shale, the thermo-induced pore pressure is important while in high mobility formation, the pressure effect on the temperature is not negligible.

Furthermore, the imbalance in chemical potentials between the formation pore fluid and wellbore drilling fluid will cause the solvent and solutes to diffuse and transport. This will alter the fluid pressure due to chemical osmosis pressure. In this paper, a fully coupled borehole stability model is proposed including thermal, pore, chemical effect. In the model, not only pressure, heat conduction and convection are included, but also the interaction of pressure and heat are incorporated. The model is solved by superimposing method and finite difference method which otherwise is impossible to be obtained from analytical solution.
A Novel Fluid to Improve the Hydraulic Cracking Stress of Rock
Authors: Grady Brian , Wu Shuqing , Funkhouser Gary P.
Published: September 2011

Negatively charged poly(methyl methacrylate-co-butyl acrylate) (P(MMA-BA)) particles, and positively charged dissolved poly(ethyleneimine) (PEI) polymer were adsorbed onto a cement block using a layer-by-layer assembly technique. The block was fashioned so as to have a cylindrical hole running from one face to another along its long axis, and a fluid containing one of the two charged materials was pumped through the block. The result was a controllable-thickness film tens of micrometers thick, and the pressure required to crack the cement block was measured after sealing one end of the hole. Latex particles with a Tg near the use temperature showed the maximum improvement in the cracking stress of the blocks. In a multilayer coating with identically sized particles, the cracking stress of the blocks increased to an improvement of 25% and then dropped off with increasing number of layers, even though the relationship between film thickness and the number of layers was linear. An improvement of about 30% in the cracking stress of the coated blocks was obtained when using multiple layers with different particle sizes. Tests done under confinement, e.g., with an external stress applied to the outside of the blocks, suggest that not only does a film-forming mechanism contribute to performance, but filling of microcracks in the rock may also play a role.
Viscosification-on-Demand: Chemical Modification of Biopolymers to Control Their Activation by Triggers in Aqueous Solutions
Authors: Reddy B. R.
Published: September 2011

Completion and stimulation operations in the oilfield industry are made possible because of the availability of suitable viscosifying polymers, particularly those from biological sources. Many such polymers, particularly those of random-coil type, suffer from viscosity losses caused by thermal thinning at elevated temperatures. Shear thinning coupled with thermal thinning of natural polymers and their derivatives limits their use to lower temperatures or requires high concentrations of such materials to prevent particulate settling. High polymer concentrations cause excessive surface-fluid viscosities. High surface viscosities of fluids require high pump pressures, which can result in either operational limitations or wellbore instabilities. An ideal way to overcome such limitations is to compensate for thermal thinning as it occurs by delaying release of viscosifying polymers into the treatment solutions until needed.

This paper discusses the development of a simple and cost-effective chemical method used to modify polysaccharides and their derivatives such that their viscosification ability, by hydration followed by dissolution in the treatment fluid, can be triggered when and where it is needed. The triggers can be salinity, pH, and/or temperature. Additionally, the method also provides for improvement of viscosification efficiency of the polymers because of increased molecular weights of the modified polymer, which allows fluid designs with less polymer content, resulting in less formation damage. Using this method, guar and its derivatives, cellulose and its derivatives, starch, xanthan, scleroglucan, and diutan polymers were modified to obtain products with interesting and versatile combinations of delayed hydration, higher viscosification efficiencies, and susceptibility to different methods of activation. The timing of viscosification using different triggers was measured by viscosity/rheological methods. Potential uses for such materials in fracturing, gravel packing, fluid diversion, and plugging are demonstrated with suitable examples. Mechanistic aspects of the chemical reactions are also discussed.
The Impact of Organic Acid on Scale Inhibitor/Corrosion Inhibitor Interaction, a Case Study from West Africa
Authors: Spicka K. J. , Johnston C. J. , Jordan M. M. , Nguyen L. T. , Samaniego S. L. , Sutherland L.
Published: September 2011

A development in deepwater off Western Africa has been experiencing incompatibility between the incumbent scale inhibitor and a newly deployed corrosion inhibitor. Initial laboratory testing to determine the amount of scale inhibitor necessary to overcome the interference from the corrosion inhibitor indicated that the effects of the corrosion inhibitor could not be overcome by increasing the dose of the scale inhibitor. Testing of other scale inhibitors indicated that there was not a suitable scale inhibitor that could inhibit scale formation in the presence of the corrosion inhibitor. That initial work was performed using synthetic brines that contained no acetate/acetic acid buffer to help control pH of the system. Further work evaluating the effect of buffering upon scale inhibitor performance employed brine containing an acetate/acetic acid buffer. Once this buffer solution was employed in static bottle testing, it was observed that an alternative scale inhibitor previously tested now worked in the presence of the corrosion inhibitor. While it is known that corrosion inhibitors can impact scale inhibitor performance the impact of organic acid on this interaction has not been published.

Since the field where the chemicals were to be applied is known to contain organic acids (upwards of 2,000 ppm), the testing which included the acetate/acetic acid buffer is viewed as a more representative test for the field than the testing that did not contain any organic acids. A field trial of the alternative scale inhibitor and the corrosion inhibitor has been under taken. The paper will present the results from two field trials, the laboratory evaluation to understand the mechanism of interaction and selection of the alternative inhibitor chemical. This paper will shed light on the challenging subject of scale inhibitor and corrosion inhibitor interaction and review the most appropriate test methods/conditions to select non interfering chemicals.
Evaluation of Liquid Loading in the Pinedale Field: Integration of Smart Plunger Data and Mechanistic Modeling
Authors: Bello O. , Falcone G. , Xu J. , Scott S. , Harrod J.
Published: September 2011

Smart plungers1 can be used to enhance diagnostics and performance evaluation of liquid-loaded gas wells. The objective of this work is to develop a framework in which surface measurements and smart plunger data from the Pinedale field are analyzed using a mechanistic plunger lift model, so as to provide a methodology for maximizing well performance and reducing operational costs.

In this paper, the application of smart plunger technology in two Pinedale wells is presented. A description of the mechanistic model used for the analysis of the gathered transient flow data is also provided, including a discussion on changes to the model for different well completions (namely with or without packer). Inputs to the model are dynamic pressure and temperature, well completions, fluid properties and produced flow rates. Results from the two Pinedale wells are presented and critically reviewed. The results suggest that the proposed integrated approach is a feasible and practical methodology to optimize the performance of plunger lift cycles. Recommendations are then made for future technological advances in the development of an interpretation model for real-time analysis of smart plunger data, towards fully automated management of liquid loading in gas wells.
Monobore Expandable Liner Extension Saves Well With Problematic Drilling Programme from Abandonment
Authors: Stockmeyer Carl F. , Durment Albert S. , Ismail Ahmed S. , Lapeira Manuel
Published: September 2011

To circumvent or minimize non-productive time (NPT) in wells where drilling programs with problematic drilling sections would be expected, the Monobore Expandable Liner Extension System (MELES) was developed. A recent exploration project in Egypt predicted costly and time consuming drilling hazards in their well programme and planned the MELES as a contingency system should these situations be realized. While drilling the 12.25-in. hole section below the 13-3/8-in. casing, situations with caving, sloughing, and swelling shale sections, combined with lost returns were encountered. Before the 12.25-in. hole section was completed, shales packed off the drillstring and part of the bottomhole assembly (BHA) was left in the hole. The MELES was no longer a contingency, but would now be required in the casing design to reach the target evaluation depth with a sufficient hole size of 6.0-in. Casing (9-5/8-in.) was run as deep as hole conditions allowed, with a recess shoe to enable the monobore expandable liner extension below. Following drillout of the recess shoe, open hole conditions presented the same challenges previously experienced. The 8-in.outside diameter (OD) liner extension system was run, but well conditions prevented getting the expandable liner to depth and it was pulled out of the hole.

Conditioning trips with increased mud weight up to 12.3 pounds per gallon (ppg), reaming and backreaming, along with an open hole cementing effort, were performed for stabilization. A second attempt was made to run in the hole. The hanger located in the recess shoe profile of the 9-5/8-in. casing and the system was expanded to the same inside diameter as the casing above. The expanded liner's shoe was now located just above the previously left BHA, but the trouble zone sections were isolated with no reduction in hole size from the previous casing.

The expanded liner was pressure tested to 1,000 psi before cementing. Recess shoe ports were enabled and initial circulation established, and the wellbore did indeed pack off and build pressure, preventing full annular cement. Pressure inside the casing was applied and 15 barrels (bbl) of cement were squeezed into the hole. A casing exit was milled in the expanded monobore liner to enable bypassing the BHA that was left in the hole from previous drilling operations.

The case history explored in this paper highlights overcoming substantial issues using expandable drilling liner technology via a monobore liner extension that resulted in successful installation and circulation. The preplanning, installation considerations, expansion process, lessons learned and post-deployment results will be discussed.
The Use of Zinc Dialkyl Dithiophosphate as a Lubricant Enhancer for Drilling Fluids Particularly Silicate-based Drilling Fluids
Authors: Chang Zen-Yu , Breeden David , McDonald Michael
Published: September 2011

As well profiles become more challenging, drilling fluids and lubricants face the need to provide further reductions in torque and drag. Tightening environmental regulations have placed further pressure on operators who now look more frequently to water-based fluids to solve these challenges despite their higher coefficients of friction.

One of the most commonly used methods for reducing torque and drag is the addition of a lubricant to the drilling fluid. Lab results show that the addition of a minor amount of zinc dialkly dithiophosphate (ZDDP) is an effective means of improving the performance of most classes of lubricants including those used with water-based fluids. Downhole conditions of temperature and pressure can provide the necessary conditons for the ZDDP to decompose and form a polyphosphate film on the surface of the drill string and casing. It is postulated that this film serves multiple beneficial roles; reducing wear and corrosion on the underlying metal surface while working synergistically with other lubricants used.

This paper focuses on the use of ZDDP/lubricant combinations in potassium and sodium silicate-based drilling fluids. Silicates were chosen as the drilling fluid for this evaluation because of their reputation for shale inhibition, clean environmental performance and because these fluids are often disadvantaged with high coefficients of friction. Lab testing has shown that a small addition of ZDDP can improve performance for a number of lubricants demonstrated by 15% to 60% reductions in coefficient of friction versus the unmodified lubricant. Of the various lubricants tested with ZDDP, the base lubricant was selected for field trials using the criteria of performance and health, safety and environmental characteristics.
Effect of Alkalinity on Oil Recovery During Polymer Floods in Sandstone
Authors: Kazempour Mahdi , Sundstrom Eric , Alvarado Vladimir
Published: September 2011

Alkaline flooding has been purported as a promising process for enhancing heavy oil recovery, while alkaline-polymer (AP) and alkaline-surfactant-polymer (ASP) injection represent commercial flooding strategies for lighter oils. The alkali in an ASP flood can reduce adsorption of surfactants and react with acids in the oil to form soaps. Polymers increase the viscosity of water and control mobility ratio. The addition of an alkali to a straight polymer flood can further increase the efficiency in polymer flooding. The alkali can react with the rock and polymer to reduce polymer adsorption and decrease polymer solution viscosity allowing higher injectivity.

We report results of core experiments for polymer, alkali, and AP tertiary floods. The conditions tested correspond to Wyoming's Minnelusa sandstone reservoirs. Berea cores were waterflooded to residual oil saturation, and then a tertiary injection of a polymer, alkali or AP solution was run, followed by waterflooding. We also show results of polymer solution viscosity with varying alkali concentration. Polymer adsorption results from dynamic and static experiments with and without alkali are reported. Numerical history match of coreflooding results was performed using k-partition method using CMG-STARS.

Results show that a tertiary alkali injection produces negligible oil recovery and pressure drop increase. Straight polymer injection produces considerable oil recovery with a significant increase in pressure drop that may not be favorable for field designs. The injection of the AP solution also produced considerable oil recovery, but the increase in pressure drop was less than that of the straight polymer flood. The effects of alkali on polymer and rock surface lead to significant impact on recovery factor, resistance factors and also residual resistance factors.

Results of this study can be utilized to improve the engineering design of polymer flooding with the addition of alkali to improve the injectivity and reduce the loss of polymer due to adsorption on the rock surface.
Critical Evaluation of Biocide-Friction Reducer Interactions Used in Slickwater Fracs
Authors: Aften Carl , Paktinat Javad , O'Neil Bill
Published: September 2011

The practice of slick water fracturing has increased significantly with the advent of horizontal shale stimulation. Many technologies have evolved to improve the practice, including multi-stage fracturing of horizontal wells and simultaneous fracturing, both of which increase frac treatment volumes up to several million gallons of slick water per well. Recent incidents related to interaction of biocides and friction reducers have created concerns for the industry and compelled operators to adopt methods of using biocides with short half-lives, in order to minimize or eliminate biocide contamination in flowbacks reused as frac water. Concurrently, some biocides can crosslink polyacrylamide-based friction reducers, causing severe formation damage, production impairment, and flowbacks that contain cross linked polymers, requiring further chemical treatment and increasing operational costs.

This study examines polymers and biocides, along with other additives (oxygen scavengers and scale inhibitors) commonly used in slick water fracturing, and identifies the parameters that could minimize the effectiveness of slick water frac treatments and potentially cause formation damage. To illustrate, this study incorporates a high molecular weight water-based emulsion polyacrylamide as the friction reducer, used in conjunction with various non-oxidizing biocides, with results reflecting positive, negative, or neutral impacts. Experimental results presented in this study are supported by utilizing a 20-gallon capacity friction loop with a Reynolds number of 150,000. Conventional bench top methods were also used. Results indicate that particular biocide-friction reducer systems exhibit significant performance deviations when standard brines or flowback water is used in shale slick water fracturing treatments.

Results obtained from this study provide operators a tool to avoid combinations of specific chemicals used in slick water fracturing. Awareness of additive interactions in specific frac fluids used can maximize the effectiveness of treatments, and avoid costly errors that may adversely impair production and jeopardized performance of the biocide. The integrity of the assets on location are thus affected by diminished biocide performance (Olliver et al, 2005). Therefore, any biocide chosen for slick water treatment should be pretested for compatibility with the friction reducers and other chemical additives, in order to insure an incident free operation from a chemical standpoint and minimize the potential for formation damage.
The Analysis of Chemical Processes in Reservoirs Based on the Identification of Injection Water Fraction in Produced Brine
Authors: Ishkov Oleg , Mackay Eric , Sorbie Ken
Published: September 2011

The time and subsequent evolution of injection water breakthrough are some of the main indicators production chemists monitor for. After injected water breaks through, the risk of scaling may significantly change and scale mitigation procedures should be planned accordingly. The fraction of the injection water in the produced brine may only be ascertained from analysis of the produced water samples. So far, however, there has been little discussion about other applications of injection water fraction tracking. In this paper new applications that follow on from accurate knowledge of injection water fraction are proposed.

The calculated injection water fraction may be applied to:

Quickly and accurately identify when injection water breakthrough has taken place and therefore remedial action to prevent scale damage needs to be implemented. Identify which ions are involved in in situ geochemical reactions, and the degree of relative ion deviations; identify ion exchange reactions (Relative Ions Deviations). Detect which formation or formations a well is producing from, and potentially the amount of flow from each layer without the use of downhole flow metering.

Strong evidence of the involvement of barium, sulphate, and magnesium ions in reactions, based on the calculations of the Relative Ions Deviations, has been shown for field data. In another case, application of injection water fraction prompted a re-evaluation of the formation water compositions, and as a result it was discovered that the well was producing from a different formation after re-perforation.

The significant new developments presented in this paper allow analysts to obtain an indication of which ions are involved in the reactions, and the degree of relative ion deviations. Additionally, a technique which identifies which formation or formations the well is producing from is proposed.