bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantifying Skin Variation for Underbalanced Perforating
Authors: Zhan Lang , Kuchuk Fikri , Filas Jim , Kannan Dhani , Saeedi Jawaid , Van Petegem Charles 
Published: February 2008

Abstract
Reliable estimates of post perforation damage skin are important for designing remedial solutions and productivity enhancement operations. Underbalanced perforating (UBP), which is widely used in well completions, induces transient fluid flow that provides an opportunity for quantifying the formation parameters. However, the skin factor can rarely be estimated reliably from pressure data acquired in the current UBP operations if without flowing on surface in sufficient time. The reasons are that (a) the flow rate after an UBP continuously varies during the surge; (b) the skin factor may decrease substantially during the flow period because the mud cake, invaded filtrates, and particulate pore plugging are progressively removed at the vicinity of the sandface region; (c) the crashed layer of the perforation tunnels is cleaned up. The existing pressure transient analysis methods to determine the skin were almost exclusively developed with an assumption that the skin factor remains constant during a test. The conventional analyses do not represent the underlying physics of the surge flow and lead to loss of useful information from the skin variations. Few SPE papers have investigated the variable skin condition with a simple hyperbolic function for a constant rate drawdown. The constant rate drawdown assumption is not suitable for the UBP as the flow rate varies along with the changes in the skin (during clean-up) and the wellbore pressures.
We present a general formula to handle the skin variation resulting from the UBP and other surge flow tests. This formula extends the applications of a classic convolution algorithm to include variations in the skin and flow rates. New analytical solutions have been derived for both homogeneous and heterogeneous reservoirs based on the general convolution formula. The new solutions are applied to an integrated interpretation workflow to invert the skin variation as well as other formation parameters from pressure measurements. A field example, where both the skin and flow rate vary, demonstrates a successful application of the new solutions and interpretation methodology. The inferred skin variation allows a complete and detailed quantification of the perforation quality and cleanup efficiency. The results of this work enable the implement of better strategies for well completions and production optimization as well as correct inputs of nodal analysis.
Fracturing in Tight Gas Reservoirs: Application of SCAL Methods to Investigate Formation Damage Mechanisms
Authors: Bazin B. , Bekri S. , Vizika O. , Herzhaft B. , Aubry E. 
Published: February 2008

Abstract
Gas well productivity in tight reservoirs is greatly impeded by the fracturing fluid interactions with the formation. New simulators introduce formation damage mechanisms to calculate gas well productivity. However, equations describing formation damage must be supported by experimental data obtained in conditions representative of fracturing operations.
The purpose of this work is to derive the absolute permeability damage and multiphase flow upon return gas permeability after core invasion by a fracturing fluid by methods used in Special Core Analysis Laboratory (SCAL). The core permeability is in the microDarcy range. Experimental data of absolute permeability damage due to the fracturing fluid filtration and water sensitivity of this illitic sandstone as well as water saturation profiles measured by X-Ray in two phase flow experiments are interpreted. The methodology of interpretation provides the petrophysical data specific to the rock-fluid system: the absolute permeability, the relative permeability damage due to hysteresis, and the capillary pressure curve.
In addition, simulations are presented for the evaluation of the impact of various operational parameters like pressure draw-down on the gas productivity. It is shown that permeability hysteresis must be considered to explain the low gas recoveries at short term. On the long term, the natural clean-up is very slow. The results, derived from a real rock-fluid system, are used to provide recommendations for improving back flow procedures. This methodology can be applied to any case of damage due to the alteration of rock-fluid properties.
Interactions of Iron and Viscoelastic Surfactants: A New Formation-Damage Mechanism
Authors: Al-Nakhli A. R. , Nasr-El-Din H. A. , Al-Baiyat A. A. 
Published: February 2008

Abstract
Viscoelastic surfactant-based acids have been extensively used over the last few years in matrix and acid fracturing treatments. Two main types of viscoelastic surfactants have been used; amphoteric and cationic. Once the acid reacts with the carbonate formation and the pH increases above two and the concentrations of calcium and magnesium ions increases, these surfactants form a long rod shaped micelles. As a result, the viscosity of the solution increases significantly. This will result in better acid diversion in matrix acid treatments and deeper acid penetration in acid fracturing treatments.
Viscoelastic surfactant-based acids were used in more than 600 successful treatments. The results, however from one treatment was below expectations. Analysis of the live acid used indicated that this acid contained nearly 10,000 mg/l total iron. It was clear that there were some interactions between iron and the viscoelastic surfactant used. Therefore, this study was conduct to better understand interactions between iron and various types of viscoelastic surfactants. All tests were conducted on live acid that contained 20 wt% HCl, 4 to 6 vol% surfactant, and 0.3 vol% corrosion inhibitor. Ferric chloride was added to the live acids at various concentrations from 0 to 10,000 mg/l.
Compatibility tests indicated that there are strong chemical interactions between iron (III) and all types of viscoelastic surfactants examined. A gel like material was noted at a certain iron concentration. SEM analysis indicated that the gel-like material contained iron. Also analysis of the iron in the supernatant using ICP confirmed this result. The critical iron concentration was found to be a function of the surfactant type. Extensive lab testing indicating that there is interactions between iron and the amide and amine groups present in these surfactants. Corrosion inhibitors contain amine and amide groups, and they did affect the interactions between iron and viscoelastic surfactants. These interactions resulted in the formation of the gel-like material that can cause sever formation damage. This paper will discuss the results obtained and give recommendations to avoid the formation of such damaging material.
A New Gravel-Pack Approach Using Two Different Proppants in Long Horizontal Well Completions
Authors: de Magalhães J. V. M , Calderon A. , de Oliveira T. J. L. , Pires I. J. , Martins A. L. 
Published: February 2008

Abstract
The new scenario for offshore development in Brazil includes heavy oil fields in ultra deepwaters where 1000 m to 2000 m horizontal section wells are economical drives for field development. Such well geometry would assure effective reservoir drainage to maintain a reasonable productivity index of a heavy oil field.
In such wells, mainly in low frac gradient scenarios, it is known that the dynamic pressures during gravel-packing operations can easily overcome formation frac pressure. In order to accomplish this task and avoid formation damage, a new approach has been proposed. During the beta wave stage, where a large pressure growth is observed, a lightweight proppant would be pumped.
This article shows the computational simulations used to design this gravel-packing operation with two different proppants, in order to enable the completion of such wells.
Enhanced Oil Production Through a Combined Application of Gel Treatment and Surfactant Huff'n'Puff Technology
Authors: Wang Yefei , Bai Baojun , Gao Hengda , He Long , Zhao Fulin 
Published: February 2008

Abstract
Surfactant huff-puff for production wells has become a recent interest, especially for extremely heterogeneous reservoirs. However, injected surfactant will preferentially move into fractures in fractured reservoirs or higher permeability zones in unfractured reservoirs and will bypass much of the reservoir. In addition, the surfactant will be produced immediately after the production well resumes to production, so the soaking time is limited. This paper introduces a novel process which couples gel treatment and surfactant huff-puff in one EOR process in which surfactant solution is first injected into the production well, then followed by gel treatment. The proposed method has been applied for 10 production wells in a polymer flooding unit in Daqing oilfield. The best compatible surfactant and gel were screened out for the given reservoir conditions before the field application. The mechanisms of the proposed method were studied using core flooding experiments. The field application design process is presented and the application results have been analyzed. Application results show pressure drawdown test can be an important criterion to select candidate for the combined method.
A New Method To Characterize Scaling Damage From Pressure Measurements
Authors: Carageorgos T. , Marotti M. , Bredrikovetsky P. 
Published: February 2008

Abstract
Sulphate scaling with consequent deposit formation and wellbore damage is a well-known phenomenon that occurs during waterflooding, when mixing of incompatible injection and formation waters may result in sulphate salt precipitation and flow restriction. The reliable productivity decline prediction is based on mathematical modelling with well-known model coefficients. The sulphate scaling system contains two governing parameters: the kinetics coefficient characterising the velocity of chemical reaction and the formation damage coefficient showing how the permeability decreases due to salt precipitation.
Previous works have derived analytical-model-based method for determination of both coefficients from breakthrough concentration and pressure drop during laboratory coreflood on quasi steady state commingled flow of injected and formation waters, and also from just pressure drop measurements during two corefloods with two different ratios "formation water : seawater".
This paper extends the previous works, by sequence of two commingled injections of incompatible waters into the same core with two different ratios "formation water : seawater". Two different slopes of skin factor increase during two injections allow calculating the kinetics and formation damage coefficients in order to predict scaled-up well behaviour.
Formation Damage Evaluation From Non-Linear Skin Growth During Coreflooding
Authors: Bedrikovetsky P. , Vaz A. S. L. , Furtado C. , de Souza A. L. S. 
Published: February 2008

Abstract
Injectivity decline of oilfield injection wells is a widespread phenomenon during sea/produced water injection. The decline may result in significant cost increase of the waterflooding project. Reliable modelling-based prediction of injectivity index decrease is important for waterflood design as well as for the choice and preventive treatment of injected water. One of the reasons for well injectivity decline is permeability decrease due to rock matrix plugging by solid/liquid particles suspended in the injected water.
The mathematical model for deep bed filtration contains two empirical functions – the filtration coefficient and the formation damage coefficient. We consider the case where both coefficients are linear functions of retained particle concentration. In this case, the model is fully determined by four constants. These constants should be determined from laboratory coreflood tests by forcing water with particles to flow through core samples. A routine laboratory method determines the filtration coefficient from expensive and difficult particle concentration measurements of the core effluent; then the formation damage coefficient is determined from inexpensive and simple pressure drop measurements.
An alternative method uses pressure data at an intermediate point of the core, supplementing pressure measurements at the core inlet and outlet. The proposed method furnishes values for the four model parameters. The method is implemented in a simple and robust tool used in field conditions to characterise injectivity damage system and predict injection well behaviour.
XANES Spectroscopic Analysis of Phosphorus Speciation in Alum‐Amended Poultry Litter
Authors: Seiter Jennifer M. , Staats‐Borda Kristin E. , Ginder‐Vogel Matthew , Sparks Donald L. 
Published: February 2008

AbstractAluminum sulfate (alum; Al2(SO4)3·14H2O) is used as a chemical treatment of poultry litter to reduce the solubility and release of phosphate, thereby minimizing the impacts on adjacent aquatic ecosystems when poultry litter is land applied as a crop fertilizer. The objective of this study was to determine, through the use of X‐ray absorption near edge structure (XANES) spectroscopy and sequential extraction, how alum amendments alter P distribution and solid‐state speciation within the poultry litter system. Our results indicate that traditional sequential fractionation procedures may not account for variability in P speciation in heterogeneous animal manures. Analysis shows that NaOH‐extracted P in alum amended litters is predominantly organic (∼80%), whereas in the control samples, >60% of NaOH‐extracted P was inorganic P. Linear least squares fitting (LLSF) analysis of spectra collected of sequentially extracted litters showed that the P is present in inorganic (P sorbed on Al oxides, calcium phosphates) and organic forms (phytic acid, polyphosphates, and monoesters) in alum‐ and non‐alum–amended poultry litter. When determining land application rates of poultry litter, all of these compounds must be considered, especially organic P. Results of the sequential extractions in conjunction with LLSF suggest that no P species is completely removed by a single extractant. Rather, there is a continuum of removal as extractant strength increases. Overall, alum‐amended litters exhibited higher proportions of Al‐bound P species and phytic acid, whereas untreated samples contained Ca‐P minerals and organic P compounds. This study provides in situ information about P speciation in the poultry litter solid and about P availability in alum‐ and non‐alum–treated poultry litter that will dictate P losses to ground and surface water systems.
Density and thermal expansion of liquid binary Al–Ag and Al–Cu alloys
Authors: Brillo Jürgen , Egry Ivan , Westphal Jenny 
Published: February 2008

Abstract
Densities and thermal expansion coefficients of liquid Al–Ag and Al–Cu alloys were measured using the technique of electromagnetic levitation. This technique involves producing shadow images of the sample from which the volume is calculated by an image processing algorithm.
Data was obtained at temperatures above the melting point. The concentration dependence of density and thermal expansion was studied for both systems. It was found for Al–Ag and Al–Cu that both density and thermal expansion can be related to a negative excess volume and its temperature coefficient.
Double-smoothing in Kernel Hazard Rate Estimation
Authors: Pfahlberg A. , Gefeller O. , Weißbach R. 
Published: February 2008

Summary

Objectives:
In oncological studies, the hazard rate can be used to differentiate subgroups of the study population according to their patterns of survival risk over time. Nonparametric curve estimation has been suggested as an exploratory means of revealing such patterns. The decision about the type of smoothing parameter is critical for performance in practice. In this paper, we study data-adaptive smoothing.

Methods:
A decade ago, the nearest-neighbor bandwidth was introduced for censored data in survival analysis. It is specified by one parameter, namely the number of nearest neighbors. Bandwidth selection in this setting has rarely been investigated, although the heuristical advantages over the frequently-studied fixed bandwidth are quite obvious. The asymptotical relationship between the fixed and the nearest-neighbor bandwidth can be used to generate novel approaches.

Results:
We develop a new selection algorithm termed double-smoothing for the nearest-neighbor bandwidth in hazard rate estimation. Our approach uses a finite sample approximation of the asymptotical relationship between the fixed and nearest-neighbor bandwidth. By so doing, we identify the nearest-neighbor bandwidth as an additional smoothing step and achieve further data-adaption after fixed bandwidth smoothing. We illustrate the application of the new algorithm in a clinical study and compare the outcome to the traditional fixed bandwidth result, thus demonstrating the practical performance of the technique.

Conclusion:
The double-smoothing approach enlarges the methodological repertoire for selecting smoothing parameters in nonparametric hazard rate estimation. The slight increase in computational effort is rewarded with a substantial amount of estimation stability, thus demonstrating the benefit of the technique for biostatistical applications.
Amino Acid Transporters: Roles for Nutrition and Signalling in Developing Tissues
Authors: Van Winkle Lon J 
Published: February 2008

AbstractAmino acids serve both to nourish and signal in cells and, consequently, so do their biomembrane transporters. Most amino acid transporters now appear to have been cloned, and virtually all of the cloned transporters are listed in solute carrier (SLC) tables for easy access online (http://www.bioparadigms.org/slc/menu.asp). It is more difficult to decide which transporters are expressed in a given tissue, and the tissue's transporter functions will likely continue to emerge long after all of the transporters have been identified. We illustrate these ongoing investigations of transporter identification and function for the first cell types to differentiate in the early embryo.
Protein Synthesis Initiation in Bacteria
Authors: Grunberg‐Manago Marianne , Studer Sean M , Joseph Simpson 
Published: February 2008

Abstract
Translation initiation begins with the assembly of the pre‐initiation complex followed by the formation of the initiation complex. The process of initiation then continues until the first peptide bond is formed; it is at this point that translation begins. The formation of the pre‐initiation/initiation complex is often the rate‐limiting step during the process of translation, as it is influenced by a number of translational regulatory mechanisms. As a result, the process of initiation can play a significant role in gene expression.
Enzymatic Rate Enhancements
Authors: Quinn Daniel M , Sikorski R Steven 
Published: February 2008

Abstract
Enzymatic rate enhancements arise from the unmatched ability of enzymes to stabilize the transition states of the reactions that they catalyse. The purpose of this article is to discuss the magnitude and mechanistic origins of enzymatic rate enhancements. Selected enzymes are described that manifest a wide range of rate enhancements and corresponding catalytic strategies.
Spliceosomal Machinery
Authors: Grainger Richard J , Beggs Jean D 
Published: February 2008

Abstract
‘Spliceosomal Machinery’ describes how various small nuclear ribonucleic acids (snRNAs) and over 100 proteins interact to perform the precise removal of introns from eukaryotic pre‐messenger RNAs. The conserved major U2‐spliceosome machinery is the main focus of this article and other minor spliceosomes are also described, as well as an introduction to factors involved in regulating splicing.
Immunological Accessory Molecules
Authors: Benedict Stephen H , Cool Kelli M , Dotson Abby L , Chan Marcia A 
Published: February 2008

Abstract
Immunological accessory molecules are proteins expressed on the surface of immune cells that can modulate in a positive or negative manner the ability of the cell to develop or to perform one or more of its functions. Thus, accessory molecules are critical to the success or failure of controlling the immune response to foreign antigens such as infectious agents or organ transplants, the aberrant response to self‐antigens as in the case of autoimmune disease or the response to tumours.
Chromosome Mechanics
Authors: Moore Charleen M , Best Robert G 
Published: February 2008

Abstract
Chromosome mechanics describes the processes of chromosome replication and behaviour as they relate to somatic cell division and gametogenesis. Mitosis produces identical diploid somatic cells, whereas meiosis produces haploid germ cells with recombination of parental alleles. Aberrations occur in these processes that include chromosomal nondisjunction leading to numerical abnormalities and unrepaired deoxyribonucleic acid (DNA) damage resulting in chromosomal breakage and structural rearrangements.
Ethics of Research: Protection of Human Subjects
Authors: Gifford Fred 
Published: February 2008

AbstractResearch involving human subjects is invaluable for answering both scientific and clinical questions, especially those centred on making medical intervention as effective and safe as possible. But it raises a number of difficult moral issues: such experimentation can impose risk, questions arise about the adequacy of informed consent and clinical research creates a tension between the roles of clinical therapist and research scientist.
Malaria: Immunity
Authors: Hafalla Julius Clemence R , Matuschewski Kai , Mueller Ann‐Kristin 
Published: February 2008

Abstract

Malaria, a vector‐borne disease caused by
Plasmodium
parasites, remains a major cause of morbidity and mortality in the developing world. To attain a substantial and steady decline in disease and deaths, a safe and efficacious vaccine is an indispensable tool. However, fundamental to the discovery, design and development of a malaria vaccine is a comprehensive knowledge of the induction and regulation of protective immune responses against the parasite. To this end, studies utilizing animal models, naïve human volunteers and individuals living in malaria endemic areas have provided important insights regarding the different mechanisms of antimalaria immunity.
Intron Loss and Gain
Authors: Mourier Tobias , Jeffares Daniel C 
Published: February 2008

Abstract
Introns, the nonprotein coding regions of genes that are interspersed between protein‐coding exons are present in all eukaryotes' genomes. The variation in intron abundance in eukaryotic genomes signifies that intron loss and intron gain have occurred at varying degrees during the evolution of eukaryotes. Intron gain or loss events have been rare in human and other mammalian genomes, but intron loss in other eukaryotes is starting to be understood in terms of the biology of genomes.
Cancer Stem Cells
Authors: Cobaleda Cesar , Vicente‐Dueñas Carolina , Sanchez‐Garcia Isidro 
Published: February 2008

Abstract
Cancer stem cells (CSCs) are the pathological counterpart of normal somatic tissue stem cells. They possess the capacities to self‐renew and to generate a more differentiated, rapidly dividing and expanding tumour progeny. Although they constitute just a small percentage of the tumour mass, they are responsible for its maintenance and, therefore, according to the CSC hypothesis, they should be the target of anticancer treatments.
Five steps to maximizing dollars when the objective is money
Authors: Krivis Jeffrey , Zadeh Mariam 
Published: February 2008

AbstractJeffrey Krivis and Mariam Zadeh, of Los Angeles, focus on communication styles in order to improve settlements. The authors provide four tables of keywords that identify the way people get their points across. These signals allow negotiators to meet their adversaries on their opponents' terms, and provide improved results for their own clients.