bluuebunny/crossref_metadata_2025 huggingface dataset:
Avaliação da incidência e de fatores de risco para a colite isquêmica após reparo de aneurisma de aorta abdominal
Authors: Pandolfo Gilmara , Fillmann Lúcio Sarubbi , Fillmann Henrique Sarubbi , Fillmann Erico Ernesto Pretzel , Petracco João Batista , Goldani Marco Antônio
Published: December 2007

Este estudo teve como objetivo principal determinar a incidência da colite isquêmica após o reparo de aneurisma de aorta abdominal, bem como identificar fatores de risco para o desenvolvimento da mesma. Foram estudados 11 pacientes submetidos a reparo cirúrgico eletivo de aneurisma de aorta abdominal no Serviço de Cirurgia Cardiovascular do HSL-PUCRS. A incidência de colite isquêmica foi determinada através de retossigmoidoscopia flexível, com biópsia, realizada em todos os pacientes no 7º pós-operatório. A incidência da doença foi comparada com variáveis clínicas como: sexo; idade; presença de comorbidades associadas; choque trans-operatório; fluxo na artéria mesentérica inferior (AMI); complicações pós-operatórias; e o desfecho final. Em nossa amostra, a incidência da colite isquêmica após o reparo de aneurisma de aorta abdominal foi 36%, sendo destes 25% da forma gangrenosa. A ocorrência de isquemia do cólon foi mais freqüente em associação com o diagnóstico de doença pulmonar obstrutiva crônica, e em pacientes que apresentavam fluxo na artéria mesentérica inferior no pré-operatório (p<0,05). Em conclusão, neste grupo de pacientes, a incidência de colite isquêmica foi superior à descrita na literatura. A presença de DPOC e pulso na AMI no pré-operatório foram preditivos de ocorrência de colite isquêmica, após o reparo de aneurisma de aorta abdominal.
Pesquisa de sangue oculto nas fezes e correlação com alterações nas colonoscopias
Authors: Altenburg Francisco Luis , Biondo-Simões Maria de Lourdes Pessole , Santiago Aline
Published: December 2007

INTRODUÇÃO: Diante do número significativo de casos de câncer colo-retal métodos de rastreamento tornam-se necessários. A pesquisa de sangue oculto (PSO) e tida como apropriada para grandes populações consideradas de baixo risco.. OBJETIVO: Determinar a incidência de lesões neoplásicas ou pré-neoplásicas em pacientes com PSO positivos ou negativos, e correlacionar com os achados da colonoscopia. MÉTODOS: 67 pacientes foram submetidos à colonoscopia e PSO. As indicações para os exames foram: dor abdominal, alteração do hábito intestinal, e história familiar de câncer colo-retal. RESULTADOS: 37 pacientes tinham PSO negativa e 30 PSO positiva. Vinte e duas colonoscopias foram normais. As colonoscopias revelaram : pólipos, retocolite ulcerativa, doença diverticular e um tumor. A sensibilidade foi de 46,7%, especificidade de 59,1%, valor preditivo positivo de 70% e negativo de 35,1%. Considerando apenas as lesões malignas ou com potencial , a sensibilidade foi de 76,5%, a especificidade de 66%, o valor preditivo positivo de 43,3% e o negativo de 89,2%. CONCLUSÕES: Há necessidade de rastreamento a partir dos 40 anos. A pesquisa de sangue oculto nas fezes, pelo seu baixo custo e caráter não invasivo, apesar da baixa sensibilidade e especificidade, é um bom método para rastreamento de populações consideradas de baixo risco.
Espectroscopia fototérmica e difração de raios x: técnicas complementares para a investigação do Cr3+ no sistema LiGaSiO4-LiGa5O8-Li5GaSi2O8
Authors: Pedro S.S. , Sosman L.P.
Published: December 2007

Neste trabalho tentamos estabelecer um método de preparo conveniente para a obtenção da fase LiGaSiO4 de forma predominante no sistema LiGaSiO4-LiGa5O8-Li5GaSi2O8 contendo Cr3+ como impureza substitucional. As amostras foram produzidas com os componentes Li2CO3, Ga2O3, SiO2 e Cr2O3. Inicialmente, os óxidos foram misturados mecanicamente durante 2h em um gral de ágata e prensados em forma de pastilhas de 10 mm de diâmetro e 2 mm de espessura, sob carga de 2t. As pastilhas foram levadas ao forno e aquecidas até 1000ºC, dentro de cadinhos de alumina. Após 72 h o forno foi desligado e esta amostra de pastilhas foi resfriada dentro do forno. A amostra obtida foi investigada por difração de raios X para a verificação da proporção entre as fases formadas. Uma nova amostra, destinada ao objetivo de variar a proporção entre as fases, foi preparada moendo os óxidos durante 6 h, pastilhados sob 2t, e queimada também a 1000ºC, porém durante 90 h. Após este tempo de residência à temperatura de queima, o forno foi desligado, iniciando o processo de resfriamento da amostra dentro do mesmo. Em seguida realizamos as medidas de espectroscopia fototérmica nas pastilhas das duas amostras. O interesse na pesquisa desses materiais se justifica pelo fato de que eles apresentam bandas largas de absorção e emissão, nas regiões espectrais do visível e do infravermelho próximo. Estas bandas são sintonizáveis e permitem um amplo número de aplicações: em medicina, comunicações e lasers de estado sólido, por exemplo.
Resposta radiodosimétrica de implantes de sementes de biovidros radioativos no cérebro de coelhos
Authors: Costa I.T. , Campos T.P.R.
Published: December 2007

Implantes intersticiais de sementes radioativas são empregados como uma forma eficiente de tratamento de tumores cerebrais. Os biovidros surgiram como uma interessante alternativa aos materiais metálicos implantados por poderem ser absorvidos pelo organismo, diminuindo as possibilidades de efeitos colaterais. O presente trabalho investiga a radiodosimetria de implantes produzidos em cobaias no grupo de pesquisa NRI/UFMG - Núcleo de Radiações Ionizantes. A distribuição espacial da energia específica depositada por unidade de massa, gerada pelas sementes de Sm-153, foi avaliada. Um modelo computacional da região do cérebro foi construído utilizando o software SISCODES produzido pelo grupo de pesquisa NRI. Foram digitalizadas as seções de tomografia computadorizada obtidas dos coelhos com implantes de sementes. Estas foram convertidas em um modelo tridimensional de voxel, cujos tecidos, sua composição química e densidade foram identificados. A simulação do transporte de partículas nucleares foi realizada pelo código estocástico MCNP5. Os implantes executados consistiram de 15 sementes cerâmicas de Ca-Si-Sm de 1.6mm de comprimento e 0,3mm de diâmetro, enriquecidas com Sm-153. Foi previsto no modelo o posicionamento de três filetes com 5 sementes cada, sendo o espaço entre sementes de 1.2mm cada e entre filetes de 8mm. As atividades assumidas para as sementes foram de 120MBq/semente. Os resultados mostram regiões de isodose projetadas sobre o modelo de voxel dos coelhos, reproduzindo a distribuição espacial da energia depositada por unidade de massa (dose absorvida) no cérebro das cobaias. Foi previsto que a dose absorvida de 3,2Gy produzidas por 15 sementes não é suficiente para o controle tumoral no modelo em estudo. Recomenda-se o aumento do número de sementes, a atividade específica, e redução do afastamento das sementes para 5-6mm aproveitando das emissões betas emitidas do Sm-153.
Oxidation kinetics of commercially pure titanium
Authors: Gemelli E. , Camargo N.H.A.
Published: December 2007

The aim of this work was to perform thermal characterization of commercially pure titanium in dry air to determine its oxidation kinetics and the structure of the oxide. The oxidation kinetics were determined thermogravimetrically under isothermal conditions in the temperature range 300 to 750 ºC for 48 hours and the structure of the oxides was determined by differential thermal analyses and X-ray diffraction in the temperature range room temperature - 1000ºC. The oxidation rate of titanium increased with increase in temperature. It was high in the initial stages of oxidation and then decreased rapidly with time, especially up to 600 ºC. The kinetic laws varied between inverse logarithmic at the lower temperatures (300 and 400 ºC) and parabolic at the higher temperatures (650, 700 and 750 ºC). Evidences from X-ray diffraction and differential thermal analyses data revealed that the passive oxide film formed at room temperature crystallized into anatase at about 276 ºC. The crystallized oxide formed in the range 276 - 457 ºC consisted of anatase, in the range 457 - 718 ºC consisted of anatase and rutile sublayers, and at temperatures beyond 718 ºC consisted of a layer of pure rutile. Scanning electron microscopy observations reveled that the oxidized surfaces were crack-free and the surface roughness increased steadily with oxidation temperature.
Modelling faecal bacteria pathways in receiving waters
Authors: Schnauder I. , Bockelmann-Evans B. , Lin B.
Published: December 2007

The two-dimensional finite-volume model ‘Hemat’ was refined to model the pathways, fate and decay factors of faecal indicator organisms for an integrated river and coastal basin water system. The numerical model was developed, calibrated and tested by modelling faecal indicator organism inputs from river sources. A comprehensive field data set was available including intensive offshore survey data collected during a two-week period; these were used as a time series for the verification of the hydrodynamic model. River discharges and water quality data were used as boundary and initial conditions for the model. The impact of alternative land-use management strategies on the water quality of the receiving estuarine and coastal waters was investigated by modelling a series of 14 scenarios. Generally, the model results show that the faecal indicator organism input from point sources of sewage effluent dominated during dry weather and base flow conditions. On the other hand, riverine sources (such as diffuse catchment sources) significantly dominated the concentrations in the bay both during and after rainfall events. Finally, it was found that a reduction in land used for animal husbandry can considerably reduce the critical peak concentration occurring after heavy rainfall events.
Undergraduate lessons from historical failures
Authors: Mottram J. T.
Published: December 2007

Details of an undergraduate module that uses failure-related case studies to develop awareness of the major lessons to be learnt from historical disasters are presented. Increasingly, professional civil engineers work on projects for interdisciplinary systems of growing complexity and innovation, with safety and reliability at the heart of contract, design and execution procedures. Knowledge of how industry manages risk is therefore very important in preventing collective amnesia, as systems become more complex and powerful. Integration of new technologies, leading to ‘smart’ and adaptive structures brings with it the obligation for civil engineers to have a broader appreciation of what might go wrong. To achieve this goal a module called Forensic Engineering exposes students, not only to the lessons to be learnt from failures in construction, but equally to those from disasters in the industrial sectors of aviation, chemical, marine, nuclear, offshore oil and gas, and rail.
Statewide Identification of Adverse Events Using Retrospective Nurse Review: Methods and Outcomes
Authors: Silver Michael P. , Hougland Paul , Elder Susan , Haug Jan , Pritchett Tracey , Donnelly Steven , Link Carolyn L. , Xu Wu
Published: December 2007

This study was conducted as part of a two-state study of the validity of hospital discharge data for adverse event (AE) surveillance. Reliability of nurse identification of AEs was assessed through comparison with physician review. Nurses reviewed 6,296 medical records selected from two sampling frames. All were patients in 41 Utah acute care hospitals and surgery patients in 36 Missouri hospitals. A total of 1,035 records were independently reviewed by physicians using the same methods. Overall agreement between nurse and physician findings in Utah and Missouri, at the case level, was 78.5% (238/303) and 68.2% (499/732), respectively. Nurse review of medical records to identify AEs represents a cost-effective alternative to physician review for large-scale and ongoing patient safety improvements and surveillance purposes.
Production of Wet Natural Gas Containing Corrosive Components: Four Case Histories
Authors: Havlik Wolfgang , Thayer Karin , Oberndorfer Markus
Published: December 2007

In petroleum production, the problem of corrosive media attacking metallic structures is almost ubiquitous. Particularly severe environments are encountered in the production and transport of wet natural gas containing corrosive components, such as hydrogen sulphide and carbon dioxide. When exploring new gas fields, it is therefore a prerequisite to take into account the corrosivity of the respective fluids in all stages of the field development, material selection, field layout, and facilities design. In preparation of the subsequent production phase, reliable corrosion monitoring programs have to be selected, established, and implemented as necessary. Furthermore, the financial aspects always play an important role, thus posing a real challenge for the engineer forced to seek a compromise between economics and design.

This paper gives a comprehensive overview of these considerations regarding four different OMV gas fields, two in Austria and two in Pakistan, which were successfully developed and brought onstream between 1967 and 2003. These fields not only vary in their geographical position, but also in their gas compositions, production start, and the location of gas dehydration units.

One major aspect dealt with in each of these cases was material selection, including metallic as well as nonmetallic and composite materials. Where the initial decision was made in favor of carbon steel, different methods of corrosion protection, the application of corrosion inhibitors, corrosion monitoring, and intelligent pigging are discussed in the paper.

A comparison of the various methods of resolution worked out for all four case histories, as well as the experience gained in more than three decades of production and transportation of wet, corrosive natural gas is presented.

Furthermore, results of the ongoing corrosion monitoring measurements in operation in the mature gas fields are discussed under the aspect of the remaining facility lifetimes.
Operational Control of Hydrocyclones During Variable Produced Water Flow Rates—Frøy Case Study
Authors: Husveg Trygve , Johansen Oddgeir , Bilstad Torleiv
Published: December 2007

International regulations of produced water discharges to sea are enforced, thereby enhancing focus on optimizing produced water treatment. De-oiling hydrocyclones are prioritized technology for produced water treatment on offshore oil-producing platforms. Oil/water separation happens within a few seconds in hydrocyclones and preciseness in operational control is essential. Surging flow may cause severe problems to hydrocyclones. A case study at TOTAL E&P NORGE AS's Frøy field demonstrated how the implementation of a holistic process control structure effectively optimized hydrocyclone performance by reducing oil in produced water by 50%. This paper emphasizes how operational interaction between separators and hydrocyclones, alternative routing of hydrocyclone oil streams, capable control systems, and establishing hydrocyclone performance indicators are all elements in optimization programs for de-oiling hydrocyclones.
Discussion of A Practical Method for Anticipating Asphaltene Problems
Authors: Civan Faruk
Published: December 2007

Wang et al. (2004) propose a practical approach to predicting the conditions leading to asphaltene problems. Their Fig. 7d presents three onset pressures of asphaltene flocculation determined at 70, 140, and 210°F temperatures. These data are of practical significance because it may be inferred from this information whether the asphaltenes present in crude oil are stable or unstable at various pressure and temperature conditions. Therefore, it may be useful to correlate these data in a convenient and rigorous manner so that the onset pressures at reservoir temperatures other than the three reported measurements can also be estimated by interpolation/extrapolation, as suggested by the procedure described below.
Development and Testing of a Pseudo-Three-Dimensional Model of Hydraulic Fracture Geometry
Authors: Settari Antoníh , Cleary Michael P.
Published: December 2007

A pseudo-three-dimensional (P3DH) model has been developed to describe realistically the evolution of geometry of a 3D hydraulic fracture produced by fluid injection into a reservoir. The present model bypasses the task of a fully 3D crack geometry calculation, which is at present prohibitively complex in the context of a complete practical fracturing simulator. The P3DH model presented formulates the problem in terms of equations for lateral fluid flow and crack opening for the main body of the fracture, coupled with a very efficient scheme for describing vertical fracture growth at each cross section. The equations for lateral flow are solved by finite differences, and the vertical propagation problem is solved by numerical implementation of a singular integral equation on a suitable set of Chebyshev points.

The testing of P3DH components shows both an excellent agreement of the lateral propagation model with various analytical solutions (Ref. 1) and a strong sensitivity of vertical propagation to confining stress and stiffness contrast of adjacent strata and to fluid rheology. The sample simulations show that the model produces realistic fracture growth under a wide range of conditions, is extremely sensitive to the dominant containment parameters, and therefore can be used to study the effect of relevant design parameters on fracture shapes and pressures in stimulation treatments.

The P3DH model is highly efficient and suitable for incorporation in a general 3D fracturing simulator. The computational effort for calculation of fracture geometry with P3DH is generally comparable to that required for the simulation of the fluid flow in the surrounding reservoir.
A Sensitivity Study of the Effect of Parameters on Results From an In-Situ Combustion Simulator
Authors: Anis M. , Hwang M. K. , Odeh A. S.
Published: December 2007

A study of the sensitivity of results from an in-situ combustion simulator to key parameter variations was made. The model was based on the finite-difference method of solution and accounted for the kinetics of the combustion process. The parameters were block size, dimensionality of the model, number of reactions, activation energy, reaction constant, and injection rate.

About 50 dry-combustion simulation runs were made using the model in one-, two-, and three-dimensional (ID, 2D, and 3D) modes. The chemical properties for a heavy oil were used. In general, runs were carried out for 6,000 days. The output results were cumulative oil production, oxygen consumption, peak temperature, injection bottomhole pressure (BHP), WOR, GOR, heat release from reactions, fuel consumptions, and saturation distribution.

The results were most sensitive to the flow convection parameters, such as block size and dimensionality. Kinetic parameter effects were not as significant as previously thought. Moreover, the investigation identified practical difficulties in running a kinetic-based model. Numerical distortion of the convection effects with large grid blocks limits the utility of such models. A brief discussion of a possible method to overcome some of the difficulties is given.
A Two-Dimensional Theory of Fracture Propagation
Authors: Biot M. A. , Masse L. , Medlin W. L.
Published: December 2007

A basic theory of two-dimensional (2D) fracture propagation has been developed with a Lagrangian formulation combined with a virtual work analysis. Fluid leakoff is included by the assumption that an incompressible filtrate produces a piston-like displacement of a compressible reservoir fluid with a moving boundary between the two. Poiseuille flow is assumed in the fracture. We consider both Newtonian and non-Newtonian fluids with and without wall building. For non-Newtonian fluids, we assume the usual power-law relation between shear stress and shear rate. The Lagrangian formulation yields a pair of nonlinear equations in Lf and bj, the fracture length and half-width. By introducing a virtual work analysis, we obtain a single equation that can be solved numerically. For non-wall-building fluids, it predicts much higher leakoff rates than existing methods. The Lagrangian method also allows nonelastic phenomena, such as plasticity, to be included. A practical computer program developed from this theory has been used for more than 10 years to design fracturing treatments in oil and gas reservoirs in Canada, California, the midcontinent and Rocky Mountain areas, the U.S. gulf coast, the North Sea, and in northern Germany. In most of these applications, it has predicted fracture dimensions that have been in line with production experience. Optimization methods based on this program led to very large fracturing treatments in low-permeability gas sands that were forerunners of massive fracturing treatments in tight gas sands. Specific examples in which this method was used to design fracturing programs in large gas fields in Kansas and Texas are discussed.
Nonisothermal Effects During Injection and Falloff Tests
Authors: Benson S. M. , Bodvarsson G. S.
Published: December 2007

Numerically simulated pressure transients during injection and falloff tests are analyzed to develop methods for obtaining the correct permeability/thickness of the reservoir and the skin factor for the well. The results show that to analyze correctly the pressure transients governed by a moving thermal front, the fluid-property values must correspond to the temperature of the injected fluid. For pressure falloff tests and for injection tests conducted in a well cooled by previous injection or drilling, however, the physical properties of the in-situ reservoir fluids must be used. The application of conventional isothermal methods for calculating skin values from injection and falloff data will give erroneous results. A new method is presented for calculating skin values from injection and falloff data that accurately corrects for nonisothermal effects. Examples are given to illustrate this analysis method. The technique is applied to the analysis of injection test data from a well located in the East Mesa geothermal field in southern California.
Some Practical Issues on Real-Time Reservoir Model Updating Using Ensemble Kalman Filter
Authors: Wen Xian-Huan , Chen Wen H.
Published: December 2007

The concept of "closed-loop" reservoir management is currently receiving considerable attention in the petroleum industry. A "realtime" or "continuous" reservoir model updating technique is a critical component for the feasible application of any closed-loop, model-based reservoir management process. This technique should be able to rapidly and continuously update reservoir models assimilating the up-to-date observations of production data so that the performance predictions and the associated uncertainty are up-to-date for optimization of future development/operations. The ensemble Kalman filter (EnKF) method has been shown to be quite efficient for this purpose in large-scale nonlinear systems.

Previous studies show that a relatively large ensemble size is required for EnKF to reliably assess the uncertainty, and a confirming step is recommended to ensure the consistency of the updated static and dynamic variables with the flow equations. In this paper, we further explore the capability of EnKF, focusing on some practical issues including the correction of the linear and Gaussian assumptions during filter updating with iteration, the reduction of ensemble size with a resampling scheme, and the impact of data assimilation time interval.

Results from the example in this paper demonstrate that the proposed iterative EnKF performs better with more accurate predictions and less uncertainty than the traditional noniterative EnKF. The use of iteration reduces the impact of nonlinearity and non-Gaussianity. Results also show that iteration may only be required when predictions are considerably deviated from the observations. The proposed resampling scheme can significantly reduce the ensemble size necessary for reliable assessment of uncertainty with improved accuracy. Finally, we show that the noniterative EnKF is sensitive to the size of time interval between the assimilation steps. Using the proposed iterative EnKF, results are more stable, more accurate reservoir models and predictions can be obtained even when a large time interval is used. This also indicates that iteration within the EnKF updating serves as a process that corrects the stronger nonlinear and non-Gaussian behaviors when larger time interval is used.
The Role of the Simulator in Drilling Operations
Authors: Millheim K. K.
Published: December 2007

This paper presents a reference on the simulation industry—the state of the art, how the simulator is used, different types of simulators, and how simulator use applies to the drilling industry. For those contemplating buying or developing a simulator, this paper cites the uses and pitfalls of the simulator in drilling applications. This paper is intended to aid the engineer and manager in making decisions pertaining to the development, acquisition, or use of a drilling simulator.
Temperature-Dependent Relative Permeability and Its Effect on Oil Displacement by Thermal Methods
Authors: Nakornthap K. , Evans Ronald D.
Published: December 2007

An analytical theory is presented that permits the formulation of a mathematical model to describe the variation of relative permeability with temperature in a water/oil system. The theory develops analytical equations for temperature-dependent relative permeability in terms of water saturation, irreducible water saturation, and differential change in irreducible water saturation with temperature. These equations predict and agree reasonably well with experimental results reported by other researchers.

The implications of temperature-dependent relative-permeability data on reservoir performance of a thermal process are also presented. These data together with the application of the Buckley-Leverett frontal-advance theory and the fractional-flow equation are used to predict oil recovery.
Steep Wave Forces on Large Offshore Structures
Authors: de St. Q. Isaacson Michael
Published: December 2007

A new numerical method for calculating the interaction of steep (nonlinear) ocean waves with large coastal or offshore structures of arbitrary shape is described. The evolution of the flow, and in particular the loads on the structure and the runup around it, are obtained by a time-stepping procedure in which the flow at each time step is calculated by an integral equation method based on Green's theorem.

A few comparisons are made with available solutions and results are presented for a typical design wave in shallow water. The method is capable of predicting forces caused by steep waves accurately and without prohibitive computer effort.
Comparison of Sodium Carbonate, Sodium Hydroxide, and Sodium Orthosilicate for EOR
Authors: Burk J. H.
Published: December 2007

Alkaline and alkali/polymer flooding are economical and versatile techniques proposed for application in EOR. Recently, the use of high-pH alkaline chemicals was emphasized to obtain low interfacial tensions (IFT's) with the crude oil and to counteract alkali loss by both reservoir rock and interstitial water reactions. This experimental study compares the utility of sodium carbonate (Na2CO3) buffer solutions with sodium hydroxide (NaOH) and sodium orthosilicate (Na4SiO4) at equal Na2O levels for alkaline and alkali/polymer flooding.

The alkalis were found to be equally effective in reducing IFT with Wilmington Ranger zone crude, and eight other acid crude oils. Tertiary recovery results from 20 Berea corefloods with the Ranger zone crude and hard reservoir brine were equivalent (6 to 17%) for Na2CO3, NaOH, and Na4SiO4. Similar modest recoveries were obtained for polymer floods that used Polyacrylamide or xanthan gum. However, polymer augmentation of alkaline floods dramatically increased tertiary oil yields to 73 to 95%. In addition, alkali improved the injectivity of polymer solutions. The alkali reactions with sandstone were much less severe with Na2CO3 than with NaOH or Na4SiO4.
Comparison of an Improved Compositional Micellar/Polymer Simulator With Laboratory Corefloods
Authors: Camilleri Dominic , Fil Andre , Pope G. A. , Rouse B. A. , Sepehrnoori Kamy
Published: December 2007

In this paper, we compare numerical simulations made with our previously reported simulator with both our own and literature experiments. The most significant improvement concerns the phase behavior model used in the simulator. The new model approximately represents the phase behavior of pseudoquaternary mixtures containing surfactant, cosurfactant, oil, and brine. The different effects of sodium and calcium cations in the mixtures are accounted for with a new cation exchange model allowing for exchange with both clays and micelles. A tertiary oilflood experiment is reported that includes a more complete analysis of phase compositions and properties than generally available previously. Produced samples were analyzed for surfactant, alcohol, sodium, calcium, polymer, tritium, water, carbon-14-tagged decane, and decane. These analyses and pressure drop were compared with simulated behavior. Supporting physical property data were used as much as possible to estimate simulator input parameters rather than adjusting or "history matching" the results. Agreement with the most important features of the experiment was good. This agreement and good agreement with an experiment from the literature lead us to conclude that a significant improvement over previous efforts has been achieved. Especially noteworthy is our capability to account for the chromatographic separation of surfactant and alcohol.
Analytical Representation of the van Everdingen-Hurst Aquifer Influence Functions for Reservoir Simulation
Authors: Fanchi J. R.
Published: December 2007

Linear regression analysis has been used to develop some simple analytical expressions for the van Everdingen-Hurst aquifer influx influence functions. Regression results are presented for a variety of aquifer radius/reservoir radius ratios. The regression equations are designed for use in reservoir engineering applications, especially reservoir simulation.
Gravitational Effects During Diffusional Mass Transfer at the Pore Scale
Authors: Mahers Eric G. , Dawe Richard A.
Published: December 2007

A novel approach to study and to quantify diffusional mass transfer at the pore scale is by holographic interferometry. This is a passive technique as information is obtained from what is occurring within the pores while the fluids in the pores are not physically disturbed. The porous media used were transparent micromodels with carefully designed two-dimensional (2D) network patterns where fluids could be readily trapped. The holograms of these micromodels were made by a wet-gate technique that ensured that they would not be moved during processing, and the live fringes were observed and recorded for subsequent analysis while the mass transfer processes occurred. Maps of lines of constant composition obtained over the whole pore showed the direction and rate of diffusion and any convective component of mass transfer.

This paper gives examples for both miscible and partially miscible systems and demonstrates that the alignment of the pores with respect to the gravitational field is a significant factor in the mass transfer. The correct modeling of the pore-scale mass-transfer phenomena is essential for proper scaling to reservoir EOR processes.
Glenn Pool Surfactant Flood Pilot Test: Comparison of Laboratory and Observation-Well Data
Authors: Bae J. H. , Patrick C. B.
Published: December 2007

A surfactant flood pilot test was conducted in the William Berryhill lease of the Glenn Pool field, Creek County, OK. The test was conducted in the Upper sand in a 20-acre [8.1-ha], four-inverted-five-spot pattern. The field had been waterflooded and had a residual oil saturation of 30% PV.

A preflush preceded the surfactant slug, which was specifically formulated for this oil-wet reservoir. There were two observation wells in line between an injector and the central producer. Fluids from the observation well were periodically sampled and analyzed. A large oil bank observed in these wells had an oil cut of 40% or higher.

Despite chromatographic separation and changing sulfonate concentration and salinity, ultralow tension was maintained for a long period. The interfacial tension (IFT) behavior involving these variables was much more complex than expected. It was concluded that the process performance in the field as monitored in the observation wells was as good as expected from laboratory linear core test results.
Simple Frictional Analysis of Helical Buckling of Tubing
Authors: Mitchell R. F.
Published: December 2007

Previous analyses of helical buckling of tubing have not considered frictional forces. In this paper, differential equations are derived and solved for two simplified cases of interest: downward motion of the tubing—e.g., when buckling occurs during the landing of the tubing—and upward motion of the tubing—e.g., when buckling occurs as a result of thermal and differential pressure loading subsequent to landing. While somewhat more complicated than the conventional frictionless buckling equations, these solutions are still suitable for hand calculations. These solutions, however, do not represent general solutions to buckling with friction. Load reversals and lateral frictional forces add complications that would require computer analysis. Several examples are examined to evaluate the relative importance of friction, which has a significant impact on tubing length change for loaded cases. For instance, the choice of a conservative value for the friction coefficient may allow the solution of a difficult seal-design problem by reducing a large predicted length change. Friction also has an important effect on set-down loads. Frictionless buckling calculations do not give conservative results for this problem.
Injection Well Logging Using Viscous EOR Fluids
Authors: Knight Bruce L. , Davarzani Mohammad J.
Published: December 2007

A new tool has been developed that overcomes problems associated with logging injection wells in the presence of viscous fluids. The tool was evaluated in the laboratory and the field in water and polymer injection wells. Results indicate that the tool provides better information than conventional equipment. Special attention to log interpretation is required in zones where the flow pattern changes from turbulent to transition flow. A method is suggested to improve log interpretation that considers changes in flow regime.
Vertical Interference Testing Across a Low-Permeability Zone
Authors: Ehlig-Economides C. , Ayoub J. A.
Published: December 2007

Bremer et al.1 described a mathematical model for analysis of a vertical interference test across a low-permeability zone. The test configuration called for recording wellbore pressure vs. time opposite one permeable layer while fluid is produced from the second permeable layer. The two permeable layers are separated by a tight zone of low vertical permeability. This paper offers a more general interpretation technique that allows for distinct properties in the two permeable layers and includes wellbore-storage and skin effects.

The purpose of the vertical interference test across a low-permeability zone is to determine the vertical permeability of the tight zone separating the two permeable strata. The results of such a test may influence well completion decisions for primary, secondary, and enhanced oil recovery. Of particular interest is the estimation of the fluid flow rate into or out of the packed-off layer.

Field test data have been analyzed with the new techniques. By including wellbore-storage and skin effects, the model presented in this study provides a much better fit with the data presented by Bremer et al.1 Because this method allows for determination of formation properties in both permeable zones, simultaneous recording of the pressures in both the producing and packed-off layers is recommended. Results indicate that the wellbore- pressure difference between the flowing and packed-off zones becomes constant after sufficient time and depends only on the permeabilities in the three zones. If wellbore-storage effects can be minimized, the behavior of pressure vs. log time may exhibit two distinct slopes: the first providing for calculation of the permeability in the flowing layer, and the second allowing calculation of the permeability in the packed-off layer. Type curves are presented for analysis of both the pressure and pressure-derivative transients.

The interpretation method is suitable for broader application than previous methods would allow. An important result is an estimate of the rate of crossflow between layers separated by a low-permeability zone.
Influence of Minor Components on Strength Development of 2CaO/SiO2-Silica Cement
Authors: Sasaki S. , Kobayashi W. , Okabayashi S.
Published: December 2007

We have been accumulating the technical data on 2CaO/SiO2-silica cement as cementing material for deep oil wells and high-temperature geothermal wells. For this paper, we chose 21 inorganic compounds as minor components that are supposed to contaminate cement slurries at cementing and investigated their influence on strength development of 2CaO/SiO2-silica cement.

The early compressive strength of β-2CaO/SiO2-silica cement at 662°F [350°C] decreased remarkably with the addition of borates and hydroxides, but the strength of hardened specimens with 0.5 to 1.0% calcium chloride and magnesium chloride increased significantly. Also, we confirmed that the effect of the addition of minor components on β-2CaO/SiO2-silica cement was similar to that on γ-2CaO/SiO2-silica cement. Within this work, the strength of hardened specimens cured at 350°F [177°C] decreased with the addition of any inorganic compounds.
Design, Testing, and Planning Considerations for a 20-in. Record Casing String
Authors: Pejac R. D. , Fontenot E. P.
Published: December 2007

During May 1984, a total of 12,455 ft [3800 m] of 20-in., 169-lbf/ft [51-cm, 2.47-N/m] C-95 casing was successfully run and cemented to the surface in L.W. Magoun No. 1, Concordia Parish, LA. The string consisted of 303 joints and required 49 hours to run. The casing weight in 9.7-lbm/gal [1162-kg/m3] mud was l.8×106 lbm [826 Mg].

This paper discusses the engineering, operational planning, and job execution for this world-record string of 20-in. [51-cm] casing. The topics include casing design, manufacturing, connection testing, and running and cementing procedures.
Bentonite Quality and Quality-Evaluation Methods
Authors: Bol G. M.
Published: December 2007

Problems with bentonite quality and bentonite-quality-control methods have consistently been observed in the field in recent years. These problems are investigated and proposals are made on how to mitigate them. A number of commercial bentonites have been analyzed and their performances evaluated (1) to determine to what extent quality variations occur between commercial bentonites from different manufacturers, (2) to determine the cause(s) of these variations, and (3) to develop a proper quality-control method for bentonite.

The results show significant variations in quality between Oil Companies Materials Assn. (OCMA) and API-grade bentonite. The main cause of these variations is the different type and amount of extending chemical added.

Differences in rheology and fluid loss between bentonite suspensions in fresh water, seawater, and hydrogen-peroxide (H2O2) solutions give a quantitative measure of bentonite extension. Differences in performance before and after hot-rolling do the same.
Steam-Injection Profile Control Using Limited-Entry Perforations
Authors: Small G. P.
Published: December 2007

A completion technique for steam-injection wells that ensures improved profile distribution of steam into several independent sands is being used at the South Belridge field in California. Previously, steam profiles were poor for many of the conventionally perforated (two ⅜-in. [9.5-mm] -diameter holes per foot) injection wells. This standard completion does not guarantee that the thicker, higher-permeability sands will not act as thief zones with respect to the thinner, tighter sands open in the same wellbore. Limited-entry perforating (typically one hole per 15 to 20 ft [4.6 to 6.1 m] of gross interval with at least one in each major sand member) provides the best assurance of achieving a uniform injection profile in single-wellbore multisand completions.
Friction Pressures of Proppant-Laden Hydraulic Fracturing Fluids
Authors: Shah Subhash N. , Lee Yung N.
Published: December 2007

Friction-pressure calculations of proppant-laden fluids are very important not only in the design of any hydraulic fracturing treatment but also in real-time monitoring of fracturing treatments. Recent advances in real-time fracture analysis have necessitated an accurate knowledge of bottomhole treating pressure (BHTP). To estimate BHTP, an accurate prediction of friction pressures of fluids in the flow conduit is required.

This paper presents a new approach for predicting friction pressures of proppant-laden fracturing fluids that is based on an analytical method and uses nondimensional quantities in the analysis of flow data. From the flow data with various proppant-laden gels in multiple pipes, generalized correlations are developed and presented that incorporate such variables as proppant size, proppant density, proppant concentration, fluid density, flow rate, polymer gel concentration, and pipe size. These correlations are valid for a wide range of terminal Froude number, NFr​​​  *(8.4×10−3  to  1.3×10−4), and particle Froude number, NFrp (20 to 200). These ranges include the calculated values of NFr​​​  * and NFrp for the majority of hydraulic fracturing treatments conducted today.

The correlations are verified by comparison of the estimations with data gathered in field-size tubing and field-gathered data. Our predictions agree more closely with field data than previously published methods. Unlike previous studies, this investigation indicates that besides other factors, proppant size, pump rate, flow geometry, and polymer gel concentration play a significant role in the friction-pressure predictions of proppant-laden fluids.
Geology and Clay Mineralogy of the Morrow Formation, Southeastern New Mexico
Authors: Mazzullo L. J. , Mazzullo J. M.
Published: December 2007

Drilling and completion procedures for Morrow sandstone reservoirs in southeastern New Mexico must be designed to anticipate vertical variations in clay mineralogy in the wellbore, because different reservoir sandstones can have different authigenic clay compositions. In southeastern New Mexico, well control and sample control are more than adequate to facilitate such predictions.
Deconvolution of Wellbore Pressure and Flow Rate
Authors: Kuchuk Fikri J. , Carter Richard G. , Ayestaran Luis
Published: December 2007

Determination of the influence function of a well/reservoir system from the deconvolution of wellbore flow rate and pressure is presented. Deconvolution is fundamental and is particularly applicable to system identification. A variety of different deconvolution algorithms are presented. The simplest algorithm is a direct method that works well for data without measurement noise but that fails in the presence of even small amounts of noise. We show, however, that a modified algorithm that imposes constraints on the solution set works very well, even with significant measurement errors.
Description of an Improved Compositional Micellar/Polymer Simulator
Authors: Camilleri D. , Engelsen S. , Lake L. W. , Lin E. C. , Ohno T. , Pope G. , Sepehrnoori K.
Published: December 2007

This is one of three companion papers describing a micellar/polymer or chemical flood simulator and comparing it to experimental data. A three-dimensional version of this simulator has been developed, but in this paper we describe only the one-dimensional (1D) flow equations because we focus on comparisons with linear coreflood data and related physical properties. All physical property models are the same in both versions, however. The property models described in this paper are (1) inaccessible PV, (2) permeability reduction, (3) polymer-phase viscosity, (4) adsorption, (5) residual phase saturations as a function of capillary number, and (6) relative permeabilities.
Experimental Investigation of the Interaction of Phase Behavior With Microscopic Heterogeneity in a CO2 Flood
Authors: Bahralolom I. , Bretz R. E. , Orr F. M.
Published: December 2007

This paper reports results of an experimental investigation of the effects of microscopic heterogeneity on local displacement efficiency in a CO2 flood. Flow-visualization experiments for first-contact miscible displacements are described and compared with effluent composition measurement for the same models. High-pressure flow-visualization experiments for multicontact miscible CO2 floods are also described. The displacements were performed in two-dimensional (2D) etched glass models made from thin-sections of San Andres carbonate core from the Maljamar field. Techniques used in preparation of the models are described briefly.

Observations of first-contact miscible displacements in heterogeneous models indicate that early breakthrough and a long transition zone occur when preferential flow paths exist in the pore structure. This behavior corresponds to a flowing fraction less than 1 in the Coats-Smith model. Because the 2D models contained no dead-end PV, the results presented indicate that a low flowing fraction can occur if flow velocities in different portions of the pore space differ significantly. Coats-Smith parameters obtained for models were comparable with values obtained in floods performed in reservoir samples.

Visual observations of the CO2/crude-oil displacements indicate that there is an interaction between phase behavior and microscopic heterogeneity. Mixing of nearly pure CO2 in the preferential flow path with oil in adjacent regions leads to a residual oil saturation (ROS) that forms in the preferential path after oil initially present has been displaced.
Thermal Alteration of Viscous Crude Oils
Authors: Fassihl Mohammed R. , Meyers Kevin O. , Weisbrod Kirk R.
Published: December 2007

At temperatures encountered during thermal recovery, crude oil may undergo compositional changes that permanently reduce viscosity. An increase in the crude's API gravity and the formation of solids and gas accompany these viscosity reductions. This paper presents results of a laboratory study on thermal alteration of two biodegraded crudes and one immature heavy oil over a temperature range from 77 to 780°F [25 to 416°C] at reaction times up to 350 hours. Experimental results indicate that up to a 1, 000-fold reduction in viscosity can occur. Compositional changes accompanying thermal alteration are discussed and correlated to changes in the physical properties. We show that the viscosity and density of the reacted oil can be predicted from the net change in the carbon number distribution determined by simulated distillation. A kinetic model was developed and compared with laboratory results and published data.