bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Hybrid Numerical/Analytical Model of a Finite-Conductivity Vertical Fracture Intercepted by a Horizontal Well
Authors: Al-Kobaisi M. , Ozkan E. , Kazemi H. 
Published: August 2006

Summary
This paper presents a hybrid numerical/analytical model for the pressure-transient response of a finite-conductivity fracture intercepted by a horizontal well. The model dynamically couples a numerical fracture model with an analytical reservoir model. This approach allows us to include finer details of the fracture characteristics while keeping the computational work manageable. For example, the fracture may have irregular shape, nonuniform width, and variable conductivity, and the well may not intersect the fracture at its geometric center.
In this paper, we use the hybrid model to investigate the effects of fracture properties on the pressure-transient characteristics of a single, finite-conductivity horizontal-well fracture. The single horizontal-well-fracture model can be extended easily to multiply fractured horizontal wells by superposition. The model also can be used to compute the pseudoskin caused by the effects of nonideal fracture geometry, variable conductivity, and flow choking around the wellbore and to investigate the influence of fracture properties on the performance of horizontal wells.
A Reliable Correlation To Predict the Change in Minimum Miscibility Pressure When CO2 Is Diluted With Other Gases
Authors: Emera Mohammed K. , Sarma Hemanta K. 
Published: August 2006

Summary
A new genetic algorithm (GA)-based correlation has been developed to estimate the change in MMP when CO2 is diluted with other gases, termed "impure CO2" in the context of this paper. The advantage of this correlation over others is that it can be used for gas mixtures with higher N2 concentrations (tested up to 20 mol%) and with non-CO2 component concentrations up to 78 mol% (e.g., H2S, N2, SOx, O2, and C1−C4) with a higher accuracy. Equally important, it could be a useful screening tool when experimental data are not available and when developing an optimal and economical laboratory program to estimate the MMP.
In developing this correlation, the GA software developed in our earlier work (Emera and Sarma 2005a) has been modified to account for various components in the injected-gas stream. The correlation estimates the change in MMP as a function of injected-gas solvency in the oil. The solvency, in turn, is related to critical properties of the injected gas (critical temperature and pressure). In addition, pure CO2/oil MMP is used as an input in this correlation. The correlation has been validated successfully against published experimental data and several correlations in the literature. It yielded a better match with an average error of 4.7% and a standard deviation of 6.3%, followed by the Sebastian et al. (1985) correlation with a 13.1% average error and a 22.0% standard deviation and the Alston et al. (1985) correlation with a 14.1% average error and a 43.2% standard deviation.
Optimal Coarsening of 3D Reservoir Models for Flow Simulation
Authors: King Michael J. , Burn Karam S. , Wang Pengju , Muralidharan Venkataramanan , Alvarado Freddy , Ma Xianlin , Datta-Gupta Akhil 
Published: August 2006

Summary
We have developed a new constrained optimization approach to the coarsening of 3D reservoir models for flow simulation. The optimization maximally preserves a statistical measure of the heterogeneity of a fine-scale model. Constraints arise from the reservoir fluids, well locations, pay/nonpay juxtaposition, and large-scale reservoir structure and stratigraphy. The approach has been validated for a number of oil and gas projects, where flow simulation through the coarsened model is shown to provide an excellent approximation to high-resolution calculations performed in the original model.
The optimal layer coarsening is related to the analyses of Li and Beckner (2000), Li et al. (1995), and Testerman (1962). It differs by using a more accurate measure of reservoir heterogeneity and by being based on recursive sequential coarsening instead of sequential refinement. Recursive coarsening is shown to be significantly faster than refinement: the cost of the calculation scales as (NX·NY·NZ) instead of (NX·NY·NZ)2. The more accurate measure of reservoir heterogeneity is very important; it provides a more conservative estimate of the optimal number of layers than the analysis of Li et al. The latter is shown to be too aggressive and does not preserve important aspects of the reservoir heterogeneity. Our approach also differs from the global methods of Stern and Dawson (1999) and Durlofsky et al. (1996). It does not require the calculation of a global pressure solution, nor does it require the imposition of large-scale flow fields, which may bias the analysis (Fincham et al. 2004). Instead, global flow calculations are retained only to validate the reservoir coarsening.
Our approach can also be used to generate highly unstructured, variable-resolution computational grids. The layering scheme for these grids follows from the statistical analysis of the reservoir heterogeneity. Locally variable resolution follows from the constraints (reservoir structure, faults, well locations, fluids, pay/ nonpay juxtaposition). Our reservoir simulator has been modified to allow a fine-scale model to be initialized and further coarsened at run time. This has many advantages in that it provides both simplified and powerful workflows, which allow engineers and geoscientists to work with identical shared models.
Tidal Pressure Response and Surveillance of Water Encroachment
Authors: Langaas K. , Nilsen K. I. , Skjaeveland S. M. 
Published: August 2006

Summary
A review of the tidal response in petroleum reservoirs is given. Tidal response is caused by periodic changes in overburden stress induced by the ocean tide; the "tidal efficiency factor" is derived by two different approaches and is in line with a recent well test in the Ormen Lange gas field.
For small geomechanical pertubations like the tidal effect, we show that a simplified coupling of geomechanics and fluid flow is possible. The coupling is easy to implement in a standard reservoir simulator by introducing a porosity varying in phase with the tide. Simulations show very good agreement with the theory.
The observation of the tidal response in petroleum reservoirs is an independent information provider [i.e., it provides information in addition to the (average) pressure and its derivative from a well test]. The implementation of the tidal effect in a normal reservoir simulator gives us the opportunity to study complex multiphase situations and to evaluate the potential of the tidal response as a reservoir-surveillance method. The case studies presented here focus on the possibility of observing water in the near-well region of a gas well.
Influence of Initial Water Saturation on Recovery by Spontaneous Imbibition in Gas/Water/Rock Systems and the Calculation of Relative Permeability
Authors: Li Kewen , Chow Kevin , Horne Roland N. 
Published: August 2006

Summary
It has been a challenge to understand why recovery by spontaneous imbibition could both increase and decrease with initial water saturation. To this end, mathematical models were developed with porosity, permeability, viscosity, relative permeability, capillary pressure, and initial water saturation included. These equations foresee that recovery and imbibition rate can increase, remain unchanged, or decrease with an increase in initial water saturation, depending on rock properties, the quantity of residual gas saturation, the range of initial water saturation, and the units used in the definitions of gas recovery and imbibition rate. The theoretical predictions were verified experimentally by conducting spontaneous water imbibition at five different initial water saturations, ranging from 0 to approximately 50%. The effects of initial water saturation on residual saturation, relative permeability, capillary pressure, imbibition rate, and recovery in gas/water/rock systems by cocurrent spontaneous imbibition were investigated both theoretically and experimentally. Water-phase relative permeabilities and capillary pressures were calculated with the experimental data of spontaneous imbibition. Experimental results in different rocks were compared.
The Genetic Counseling Video Project (GCVP): Models of practice
Authors: Roter D. , Ellington L. , Erby L. Hamby , Larson S. , Dudley W. 
Published: August 2006

AbstractGenetic counseling is conceptualized as having both “teaching” and “counseling” functions; however, little is known about how these functions are articulated in routine practice. This study addresses the question by documenting, on videotape, the practices of a national sample of prenatal and cancer genetic counselors (GCs) providing routine pre‐test counseling to simulated clients (SCs). One hundred and seventy‐seven GCs recruited at two annual conferences of the National Society of Genetic Counselors (NSGC) were randomly assigned to counsel one of six female SCs of varying ethnicity, with or without a spouse, in their specialty. One hundred and fifty‐two videotapes were coded with the Roter Interaction Analysis System (RIAS) and both GCs and SCs completed evaluative questionnaires. Two teaching and two counseling patterns of practice emerged from cluster analysis. The teaching patterns included: (1) clinical teaching (31%) characterized by low psychosocial, emotional and facilitative talk, high levels of clinical exchange, and high verbal dominance; and (2) psycho‐educational teaching (27%) characterized by high levels of both clinical and psychosocial exchange, low levels of emotional and facilitative talk, and higher verbal dominance. The counseling patterns included: (1) supportive counseling (33%) characterized by low psychosocial and clinical exchange, high levels of emotional and facilitative talk, and low verbal dominance; and (2) psychosocial counseling (9%) with high emotional and facilitative talk, low clinical and high psychosocial exchange, and the lowest verbal dominance. SCs ratings of satisfaction with communication, the counselor's affective demeanor, and the counselor's use of non‐verbal skills were highest for the counseling model sessions. Both the teaching and counseling models seem to be represented in routine practice and predict variation in client satisfaction, affective demeanor, and nonverbal effectiveness. © 2006 Wiley‐Liss, Inc.
Secondary centers of ossification of the human toes: Exceptional polymorphism and evolutionary perspectives
Authors: Billmann Franck , Le Minor Jean‐Marie 
Published: August 2006

AbstractAs great morphological variability characterizes the phalanges of the human toes in adults, we hypothesized for a possible variability in the presence or absence of their secondary (= epiphyseal) centers of ossification linked to the unique morphology of the human foot within primates. The aim of this study was thus to provide original and detailed data on the occurrence of these centers. Classically, the big toe or hallux (I) presents two secondary centers and the lateral toes (II–V) three centers, and consequently the five toes present a total of 14 secondary centers. The material studied consisted of 261 foot radiographs from 261 young individuals of European origin (202 males and 59 females; 6–16 years). The presence (or absence) of the secondary centers of the phalanges of the toes was assessed for each foot. Feet presenting a biphalangeal variant in one or more lateral toes were studied separately. The theoretical possibilities of association of the three secondary centers in a given lateral toe (II–V) are eight in number; these eight patterns were studied and coded in the present study by types A–H. An exceptional variability in the occurrence of the secondary centers in lateral toes (II–V) was observed, and the classic pattern of phalangeal ossification was never observed. The absence of one or more secondary centers seems to be observed only in the human species, and we suggest that this could be a derived pattern specific to the human species, i.e., autapomorphic pattern. These results are of interest in the characterization and understanding of the reduction in size of the lateral toes which characterizes the specific evolution of the human foot. Am J Phys Anthropol, 2006. © 2006 Wiley‐Liss, Inc.
Phenotypic, maximum genetic, and special environmental variability in prehistoric human populations
Authors: Varela Héctor Hugo , Cocilovo José Alberto 
Published: August 2006

AbstractThe phenotypic variance (VP) may be divided into the genetic variance (VG), the general environmental variance (VEg), and the special environmental variance (VEs). The latter is estimated through repeatability calculation (b). This value is considered the upper limit of heritability and represents maximum genetic variance proportion (VGm = VG + VEg) in relation to VP (b = (VG + VEg)/VP). This process allows an improved determination of biological relationships among groups from estimators maximizing the genetic information of quantitative characters. Two hundred and thirty‐seven individuals inhabiting the northern coast of Chile for 4,000 years were taken as a sample. Measurement was made of six metric characters at both sides of the cranium. Special environmental values (es) were obtained by regression. The difference between these values and the phenotypic values (p) consists in the genetic values plus the general environmental values (g + eg). A mean b value of 0.83 indicated that VEs represents 17% of VP. The results showed: 1) high stability of the maximum genetic variance in time and space, 2) high correlation between the biological relationships model, the phenotypic model, and the maximum genetic model, and 3) random distribution of the nongenetic variation, as expected from the quantitative genetics theory. These results support the use of phenotypic data for the interpretation of the evolution history of prehistoric populations. Am J Phys Anthropol, 2006. © 2006 Wiley‐Liss, Inc.
Codierte Mikropartikel für Hochdurchsatz‐Mehrfachanalysen
Authors: Wilson Robert , Cossins Andrew R. , Spiller David G. 
Published: August 2006

AbstractNach der Entschlüsselung des Genoms wächst nun der Wunsch, mehr molekulare Information aus immer kleineren Proben zu gewinnen. Derzeit vertraut man auf planare Testanordnungen, doch die Qualität der Ergebnisse variiert von Versuchssystem zu Versuchssystem. Suspensionen codierter Mikrokügelchen ergeben höherwertige Daten, allerdings ist die auf diese Weise erhältliche molekulare Information durch die Zahl unterscheidbarer Codes in einer Probe beschränkt. Neue Synthesemethoden für codierte Partikel könnten hier Abhilfe schaffen, aber bei der wachsenden Vielfalt an neuen Technologien fällt die Auswahl nicht leicht. Dieser Aufsatz wägt kritisch ab, ob die neuartigen codierten Partikel gut in Mehrfachanalysen abschneiden werden.
Very high modulus high‐density polyethylene and high‐modulus polypropylene obtained by solid‐state roll drawing
Authors: Ajji A. , Dumoulin M. M. 
Published: August 2006

AbstractThis article describes results obtained with a process developed for rolling and drawing simultaneously polymer profiles in the solid state. Solid‐state roll drawing has the advantage of being continuous, which allows relatively high production rates and the generation of high deformation ratios with some degree of biaxial orientation. The roll‐drawing process allows the extent of biaxial orientation to be controlled by the adjustment of the tension and compression loads applied to the polymers, in particular semicrystalline thermoplastics. Some experimental results obtained with a four‐station roll‐drawing apparatus are presented, particularly on high‐density polyethylene (HDPE) and polypropylene. The effect of process parameters, such as the gap between the rolls and tension, are discussed. Aspects discussed also include relaxation; structure development in terms of orientation and crystallinity as a function of draw ratio (λ); λ as a function of process parameters; and finally, mechanical and thermal properties as a function of λ. Moduli as high as 25 GPa in the longitudinal direction and about 4 GPa in the transverse direction were obtained with successively rolled, initially thick, HDPE profiles. © 2006 Government of Canada. Exclusive worldwide publication right in the article have been transferred to Wiley Periodicals, Inc. J Appl Polym Sci 102: 3391–3399, 2006
Some insight into hydrolytic scission mechanisms in bioerodible polyesters
Authors: Alexis Frank , Venkatraman Subbu , Kumar Rath Santosh , Gan Leong‐Huat 
Published: August 2006

AbstractPLLA, PDLLA, and PLGA copolymers have been studied to understand the details of their degradation behavior. All polymers exhibited a homogeneous mode of degradation, with uniform rates of degradation throughout the film. Crystallinity inhibited water absorption and hence retarded degradation. The degradation rate was increased by the presence of glycolic acid units in the PLGA copolymer; this effect overwhelms any decrease in degradation rate because of increased crystallinity due to the additional GA units. This effect is demonstrated quantitatively in this study. In PLGA polymers, there is evidence of unusual recrystallization behavior as degradation proceeds, due mainly to the higher rate of hydrolytic scission of the glycolide linkage compared with the lactide, as verified quantitatively with the use of 1H NMR studies. Application of a Monte Carlo model to the degradation results, however, appears to show a random scission process. The details of the mechanistic study of different factors influencing the process of degradation, as reported here, may have important implications in terms of selecting the right material for specific biomedical applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3111–3117, 2006
Effect of crosslinking concentration on mechanical and thermodynamic properties in acrylic acid–co–methyl methacrylate hydrogels
Authors: Katime Issa , de Apodaca E. Díaz , Rodríguez E. 
Published: August 2006

AbstractThe mechanical and thermodynamic properties of poly(acrylic acid‐co‐methyl methacrylate) hydrogels with varying crosslinker N,N′‐methylenebisacrylamide (NMBA) content are reported. A higher NMBA content generally led to a stronger and harder gel with lower water content. Swelling capacity decreased as the NMBA concentration increased between 0.5% and 2%, remaining constant beyond this range. The temperature changes of the partial molar Gibbs free energy of dilution and enthalpic and entropic contributions were examined. The thermodynamic parameters showed that swelling was an unfavorable and endothermic process. The freezing and nonfreezing water in the hydrogel was determined by differential scanning calorimetry (DSC). Freezing water content decreased with increasing crosslinker (NMBA) content, whereas the ratio of nonfreezing water to total water content increased with NMBA content because of the promoting of hydrophobic interactions in the hydrogels. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4016–4022, 2006
Bismaleimide modified bis propargyl ether bisphenol A resin: Synthesis, cure, and thermal properties
Authors: Liu Feng , Li Wanwan , Wei Liuhe , Zhao Tong 
Published: August 2006

AbstractBis propargyl ether bisphenol A (PBPA) was synthesized and blended with 4,4′‐bismaleimide diphenyl methane (BDM) at different molar ratios. The cure behavior of the blend resins was measured by DSC and FTIR spectra. The results indicated that the onset cure temperatures of the blend resins were about 20–30°C lower than that of pure PBPA, and the cure exothermic enthalpy of the resins also significantly reduced from 1320 (PBPA) to 493 J/g (PBPA–BDM (1.0:2.0)). The thermal stabilities and dynamic mechanical properties of the cured resins were characterized by TGA and DMA, respectively. The thermal stability of the resins improved markedly with the increase in BDM content, and the glass transition temperature increased from 306°C for PBPA–BDM (1.0:0.5) to 358°C for PBPA–BDM (1.0:2.0). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3610–3615, 2006
Synthesis and characterization of a macromolecular surface modifier for polypropylene
Authors: Chen Hanjia , Zhu Yafei , Zhang Yi , Xu Jiarui 
Published: August 2006

AbstractA novel macromolecular surface modifier, a polypropylene‐graft‐poly(butyl methylacrylate) copolymer, was synthesized through the coupling of polypropylene containing maleic anhydride with monohydroxyl‐terminated poly(butyl methylacrylate). The effects of the raw ratio, reaction temperature, and molecular weight of the branches on the graft reaction were studied. The graft copolymers were characterized with IR, 1H‐NMR, thermogravimetry, and differential scanning calorimetry. The results of attenuated total reflection/Fourier transform infrared and contact‐angle measurements indicated that polypropylene‐graft‐poly(butyl methylacrylate) could diffuse preferably onto the surface and be used as a surface modifier for polypropylene. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:3413–3419, 2006
Reaction‐induced phase separation in poly(vinyl acetate)/polyester blend
Authors: Bulliard X. , Michaud V. , Månson J.‐A. E. 
Published: August 2006

AbstractIn blends of unsaturated polyester (UP), poly (vinyl acetate) (PVAc), and styrene, a reaction‐induced phase separation occurs upon curing that is due to the crosslinking between styrene and the UP molecules. The evolution of the morphology was observed by optical microscopy on a heated stage. Light transmission was used in parallel to precisely detect the onset of phase separation and the formation of microvoids. Using Fourier transform IR spectroscopy in the same conditions, the conversions at phase separation and at microvoiding were evaluated. Phase separation occurs at a very low degree of conversion and microvoiding develops at around 60% of conversion. The final morphology of the blend was investigated by scanning electron microscopy. The relative influences of the cure temperature, the concentration in PVAc, and the molecular weight of PVAc were investigated. It was confirmed that the early stages of the reaction at high temperature determine the final morphology of the blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3877–3888, 2006
Synthesis and properties of ethylene/styrene copolymers produced by metallocene catalysts
Authors: Haider N. , Expósito M. T. , Muñoz‐Escalona A. , Ramos J. , Vega J. F. , Méndez L. , Martínez‐Salazar J. 
Published: August 2006

AbstractEthylene/styrene copolymers were synthesized under constant polymerization conditions using six different metallocene catalysts activated with methylaluminoxane. For all the catalysts used, the activity and molecular weight of the copolymers produced decreased with the amount of styrene in the reactor feed, but the styrene content of the copolymers increased. Catalysts with carbon bridges and bulky ligands gave rise to copolymers with higher styrene content. As a result of the increased styrene content of the copolymer, the melting temperature decreased. This effect was ascribed to a decrease in the crystallinity of the copolymers. It was also found that lamellar thickness could be significantly diminished by the incorporation of comonomers. The copolymers showed a broad spectrum of mechanical properties as a function of the comonomer ratio. At low styrene contents, they behaved like typical semicrystalline thermoplastics, and at higher styrene contents, they exhibited the properties typical of elastomers. Of the catalysts tested, [rac‐ethylenebis(4,5,6,7‐tetrahydro‐1‐indenyl)]zirconium dichloride emerged as the most promising for the production of ethylene/styrene copolymers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3420–3429, 2006