bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical and Analytical Modelling of the Gas Well Liquid Loading Process
Authors: Dousi Niek , Veeken Cornelis A.M. , Currie Peter K. 
Published: December 2007

Summary
Liquid loading is a serious problem in areas where gas fields are maturing. This paper presents an analysis of the production behavior of liquid-loaded wells over time. This clearly shows that these wells can operate at two different rates—a stable rate, at which full production is taking place, and at a lower metastable rate, at which liquid-loading effects play a role.
A model has been constructed that enhances the understanding of the process of water buildup and drainage in gas wells. It assumes a single gas- and water-coproduction point and a single water reinjection point. As expected, a water column is built up in the well as soon as production takes place below the critical rate. As observed in the field, for good inflow performance, a metastable flow rate can be observed. At this state, the water-reinjection and water-coproduction rate are equal to one another, and the water-column height stabilizes.
A sensitivity analysis has been carried out to determine how well parameters influence the metastable flow rate, the time required to reach this metastable rate, the corresponding water-column height, and the shut-in time required to drain this water column. The results of the analysis indicate that significant metastable flow rates occur in wells that have good inflow performance, a low water/gas ratio, and a large distance between injection and production point.
Furthermore, a steady-state analytical solution has been derived for the metastable rate and stabilized water-column height confirming the numerical-analysis results.

Introduction
Many of the mature offshore gas fields in the southern North Sea have already experienced considerable pressure depletion resulting in significantly reduced gas flow rates and, eventually, liquid loading. Insight into the flow characteristics of these liquid-loaded wells will help manage tail-end production (i.e., will help define the most effective means of accelerating and maximizing their ultimate recovery.
Improved Reservoir Management With Intelligent Multizone Water-Alternating-Gas (WAG) Injectors and Downhole Optical Flow Monitoring
Authors: Sandøy B. , Tjomsland T. , Barton D. T. , Daae G. H. , Johansen E. S. , Vold G. 
Published: December 2007

Summary
A four-zone intelligent water-alternating-gas (WAG) injector was installed at the Statoil Veslefrikk Field in the North Sea in May 2004. The completion includes one on/off and three variable downhole chokes for controlling injection rate into each of the four zones. The completion also includes three downhole optical flow-meters and three optical pressure and temperature gauges. Measurement of surface injection rate and the rate from each of the three flowmeters provides real-time measurement of injection rate into each zone, regardless of choke positions.
The well is on a WAG cycle in which one zone is primarily intended for gas injection and the other three zones are primarily intended for water injection. Therefore, equipment that can control and measure water flow and gas flow with no changes in hardware was critical for the success of this installation.
The combination of downhole chokes and flowmeters allows full control and monitoring of zonal injection rates and has proved to be a valuable tool for managing reservoir pressures and optimizing production. After more than 1 year of operation during water injection, all the valves and the optical monitoring equipment are functioning satisfactorily. It is estimated that up to half of the well's value creation during its expected lifetime is because of the DIACS (Downhole Instrumentation and Control System) installation.
Circulating Usage of Partial Produced Fluid as Power Fluid for Jet Pump in Deep Heavy-Oil Production
Authors: Chen Shengnan , Li Heng , Zhang Qi , He Jun , Yang Daoyong 
Published: December 2007

Summary
Jet pumping driven by light oil is one of the preferred lift methods for producing heavy oil in a deep heavy-oil reservoir. Generally, the amount of light oil required is too large to be acceptable. One solution which reduces the amount of light oil required is to blend light oil with a portion of the produced fluid at a reasonable ratio. Then, the produced fluid/light-oil mixture is reinjected into the well as the power fluid. In this case, the viscosity of the blended power fluid keeps increasing and eventually reaches its equilibrium value, which has been found to be a function of reservoir-oil viscosity, light-oil viscosity, the ratio of light oil to blended power fluid (volumetric percentage), and the ratio of well rate to diluent rate (M ratio). Moreover, an optimal ratio of light oil to blended power fluid can be determined by using an iterative algorithm developed in this study. Variations in any of the previously mentioned parameters, especially the viscosity of light oil and the ratio of light oil to blended power fluid, result in a significant change in both the viscosity of the blended power fluid and the pressure loss in the production string. It has been shown in a field application that the amount of light oil used for driving the jet pumping operation can be reduced by more than 50%.
Rheology of Heavy-Oil Emulsions
Authors: Alboudwarej Hussein , Muhammad Moin , Shahraki Ardi , Dubey Sheila , Vreenegoor Loek , Saleh Jamal 
Published: December 2007

Summary
Water is invariably produced with crude oil. If there is enough shear force when crude oil and produced water flow through the production path, stable emulsions may be formed. This scenario may particularly be present during the production of heavy oils, where steam is used to reduce the viscosity of heavy oil, or in cases in which submersible pumps are used to artificially lift the produced fluids. To efficiently design and operate heavy-oil production systems, knowledge of the realistic viscosities of the emulsified heavy oil, under the actual production conditions, is necessary. This study is an attempt to investigate the effect of water content, pressure, and temperature (i.e., operating conditions on the viscosity of live heavy-oil emulsions).
Two heavy oil samples from South America were used for this study. The stock tank oil (STO) samples were recombined with the corresponding flash gases to reconstitute the original reservoir oil compositions. Live oil/water emulsions were prepared in a concentric cylinder shear cell using synthetic formation water, under predetermined pressure, temperature, and shear conditions. The stability of live emulsions was investigated using a fully visual pressure/volume/temperature (PVT) cell, while viscosities were measured using a precalibrated, high-pressure capillary viscometer. Viscosities were measured at least in three different flow rates at the testing conditions. In addition to live-oil emulsion studies, the stability and droplet size distribution of STO emulsions were also determined.
Experimental results indicated that the inversion point for the STO emulsions was approximately 60% water cut (volume), and the average droplet size was increasing with water content. For all measured cases, viscosities varied with temperature according to an Arrhenius relation, while viscosities did not indicate any variation with flow rate (shear) within the range of tested flow rates. Measured viscosities also increased as pressure decreased below the bubblepoint of the sample as lighter hydrocarbon components evolved. The measured viscosities increased as much as 500% because of the presence of emulsions before a sharp drop in viscosity beyond the inversion point. The variation of viscosity with water content for live emulsion samples indicated that the inversion point for live emulsions is similar to that of STO samples.
The experimental results are also used to analyze and evaluate the performance of an ESP system when water cut increases and causes emulsion in a well.
Behavior of a Scale Inhibitor Water-in-Oil Emulsion in Porous Media
Authors: Romero C. , Bazin B. , Zaitoun A. , Leal-Calderon F. 
Published: December 2007

Summary
The use of water-in-oil emulsions (WO) to deploy scale inhibitors has been reported in the literature as an alternative to water-based squeeze treatments. The non-aqueous nature of these emulsions has the advantage of preventing water blocking, which adversely affects oil production in aqueous squeeze treatments. Placing the scale inhibitor in a WO or "invert" emulsion has shown in some cases the additional advantage of enhancing treatment lifetime. However, results from the literature seem contradictory and highlight a poor understanding of this technology.
The present paper aims at providing further insight on emulsified scale inhibitor placement in porous media. We focus on studying the retention mechanisms of the emulsion droplets containing the scale inhibitor (SI), whilst SI release and, consequently, the performance of the emulsified squeeze is not discussed. Preliminary experiments were conducted using a low molecular-weight biopolymer as a SI. They evidenced a low adsorption/retention of this SI in aqueous solution. Reformulation of the product under invert emulsion was investigated to measure inhibitor retention.
Results from coreflood experiments using well-characterized silicon carbide (SiC) packs provided preliminary evidence of aqueous droplet adsorption as the main retention mechanism in porous media. This was expected considering the average droplet size of 0.3 µm (300 nm). The mother formulation of the WO emulsion is a concentrate, containing 80% of water phase and 8% of active SI. The product can be diluted down to 2% water phase by adding the desired oil phase. Dilution does not affect emulsion stability or increase the emulsion's droplet size. These results represent a promising first step towards the development of a technically and commercially viable, environment-friendly SI technology based on WO emulsions. Future work to study the emulsified SI release mechanisms and its consequent performance are being prepared to compare with conventional aqueous squeeze treatments.
Proppant Placement Using Reverse-Hybrid Fracs
Authors: Liu Yajun , Gadde Phani B. , Sharma Mukul M. 
Published: December 2007

Summary
In conventional gel-fracturing treatments, the damage induced by the gel can have a significant impact on well performance, particularly in low-permeability gas formations. Slick-water fracs have been shown to be more successful in some tight gas formations because of reduced gel damage and limited height growth. Proppant placement is a major concern in water fracs. Hybrid water fracs (i.e., using slick water as the pad fluid and gel to place the proppant) provide improvements to the performance of water fracs.
This paper proposes a new method, reverse-hybrid fracs (RHF), for the efficient placement of proppant deep into created fractures while minimizing gel-induced damage. Experiments were conducted in a simulated fracture (i.e., slot cell) to study the transport of proppant. Slick water was injected first into the slot, followed by gel. Finally, slick water containing proppant was injected to displace the gel. The water that carried the proppant quickly formed viscous fingers through the gel. The gel was observed to form long, thin layers that effectively hindered proppant settling and helped transport the proppant further into the slot. This resulted in the formation of proppant packs above the gel layers.
In this paper, experimental results are presented to show how the gel layers distribute in the slot and how proppant distribution is affected by the gel layers. A transparent cell composed of rough walls was set up to investigate the effect of fracture wall roughness. The effects of fluid viscosity ratio, fracture wall roughness, and gel pad volume were investigated. Based on the experiments and scaling relations, recommendations are made for the pumping sequence and the size of the gel and slick-water stages in reversehybrid fracture treatments.
This method of proppant placement requires less gel than conventional gel fracs. Other possible advantages include: (1) less gel damage to the proppant pack, (2) limited height growth, and (3) less penetration of the pad fluid into the formation resulting in shorter cleanup time following fracture treatment.
Ozonation and reductive deiodination of iopromide to reduce the environmental burden of iodinated X-ray contrast media
Authors: Putschew A. , Miehe U. , Tellez A.S. , Jekel M. 
Published: December 2007

The potential of ozonation for the removal of iodinated X-ray contrast media (ICM) with focus on the oxidation products was examined. Iopromide used as model compound was dissolved in tap water, respectively in the effluent of a membrane bioreactor and was ozonated. Ozone (10 mg/L) was continuously introduced into a semi-batch reactor (35 L/h). After 30 minutes the ozone concentration was increased to 30 mg/L. In all experiments the iopromide concentration decreased very fast, whereas the decrease of the amount of organic bound iodine (AOI) was much lower. The concentration of iodate, the inorganic oxidation product increases with time, depending on the AOI decrease. The data clearly show that the ozonation of iopromide using a common applied ozone dosage leads to the formation of numerous iodinated transformation products, which are detectable by LC-ESI-MS.
As an alternative treatment, especially for the treatment of urine or hospital waste water, the source for the contamination, it was tested if iopromide can be deiodinated by zero-valent iron. First experiments done in stirred batch reactors using iopromide dissolved in ultra pure water and urine with an initial pH of 2 showed that iopromide can be deiodinated completely by zero-valent iron. Even in contaminated urine collected in a hospital a deiodination of ICM was possible. Kinetic studies at constant pH showed that the deiodination can be described by pseudo-first order for equal iopromide and iron concentrations. The observed rate constant kobs increased with decreasing pH with a maximum at pH 3 with 4.76 × 10−4 s−1.
The concentration of iopromide can be decreased by ozonation and by the reductive dehalogenation. In case of ozonation iodinated organic compounds are the main reaction products, whereas the reductive dehalogenation leads to transformation products which are not iodinated and are thus most probable biodegradable.
Predictors of Incretin Concentrations in Subjects With Normal, Impaired, and Diabetic Glucose Tolerance
Authors: Vollmer Kirsten , Holst Jens J. , Baller Birgit , Ellrichmann Mark , Nauck Michael A. , Schmidt Wolfgang E. , Meier Juris J. 
Published: December 2007

OBJECTIVE—Defects in glucagon-like peptide 1 (GLP-1) secretion have been reported in some patients with type 2 diabetes after meal ingestion. We addressed the following questions: 1) Is the quantitative impairment in GLP-1 levels different after mixed meal or isolated glucose ingestion? 2) Which endogenous factors are associated with the concentrations of GLP-1? In particular, do elevated fasting glucose or glucagon levels diminish GLP-1 responses?
RESEARCH DESIGN AND METHODS—Seventeen patients with mild type 2 diabetes, 17 subjects with impaired glucose tolerance, and 14 matched control subjects participated in an oral glucose tolerance test (75 g) and a mixed meal challenge (820 kcal), both carried out over 240 min on separate occasions. Plasma levels of glucose, insulin, C-peptide, glucagon, triglycerides, free fatty acids (FFAs), gastric inhibitory polypeptide (GIP), and GLP-1 were determined.
RESULTS—GIP and GLP-1 levels increased significantly in both experiments (P &lt; 0.0001). In patients with type 2 diabetes, the initial GIP response was exaggerated compared with control subjects after mixed meal (P &lt; 0.001) but not after oral glucose ingestion (P = 0.98). GLP-1 levels were similar in all three groups in both experiments. GIP responses were 186 ± 17% higher after mixed meal ingestion than after the oral glucose load (P &lt; 0.0001), whereas GLP-1 levels were similar in both experiments. There was a strong negative association between fasting glucagon and integrated FFA levels and subsequent GLP-1 concentrations. In contrast, fasting FFA and integrated glucagon levels after glucose or meal ingestion and female sex were positively related to GLP-1 concentrations. Incretin levels were unrelated to measures of glucose control or insulin secretion.
CONCLUSIONS—Deteriorations in glucose homeostasis can develop in the absence of any impairment in GIP or GLP-1 levels. This suggests that the defects in GLP-1 concentrations previously described in patients with long-standing type 2 diabetes are likely secondary to other hormonal and metabolic alterations, such as hyperglucagonemia. GIP and GLP-1 concentrations appear to be regulated by different factors and are independent of each other.
Artifical Intelligence Languages
Authors: Vranes Sanja 
Published: December 2007

AbstractProgramming languages have had a crucial impact on the development of the artificial intelligence (AI) branch of computer science for at least two reasons. First, they allow convenient implementation and modification of programs that demonstrate and test AI ideas. Second, they provide vehicles of thought and they allow the user to concentrate on higher level concepts. Frequently, new ideas in AI are accompanied by a new language in which it is natural to apply these ideas.
Bioinformatics
Authors: Akutsu Tatsuya 
Published: December 2007

Abstract
Bioinformatics is an interdisciplinary area between biology and computer science. One of the major goals of bioinformatics is to develop methods and tools for analyzing huge amounts of biological data, including genomic sequences, protein structures, and gene expression data, whereas another major goal of bioinformatics is to discover new biological knowledge using such kinds of tools. We focus on the former goal and review important computational problems and computational techniques for solving these problems. In particular, we explain the following topics: pairwise and multiple sequence alignment, hidden Markov models and their applications to bioinformatics, protein structure prediction, kernel methods for bioinformatics, and analysis of gene expression patterns.
Computer Architecture
Authors: Flynn Michael 
Published: December 2007

AbstractComputer architecture represents the programming model of the computer, including the instruction set and the definition of register file, memory, and so on. Over time, the concept of computer architecture has evolved to include both the functional specification and the hardware implementation. At the system level, it defines the processor‐level building blocks, such as processors and memories, and the interconnection among the building blocks. At the microprocessor level, computer architecture determines the processor's programming model and its detailed implementation. The implementation of a microprocessor is also known asmicroarchitecture.
Computerized Dictionaries: Integrating Portable Devices, Translation Software, and Web Dictionaries to Maximize Learning
Authors: Loucky John Paul 
Published: December 2007

AbstractThis article looks first at background studies on bilingual and electronic dictionaries, then surveys their use, followed by a look at the state of the art in technical features employed by various translation programs and devices. After briefly reviewing the history of electronic lexicography, their place in language and self‐access learning is discussed, with many references given for further in‐depth study. Overall, 75 companies are listed that produce a wide variety of various computerized dictionaries and translation software programs. Finally, their potential for maximizing language learning is discussed, with pedagogical recommendations given that apply to improving the integration of these devices with both classroom and self‐access, independent online learning in all fields.
Concurrent Programming
Authors: Gomaa Hassan 
Published: December 2007

Abstract

Concurrent programming refers to the development of programs that address the parallel execution of several tasks. A
process
or
task
represents the execution of a sequential program or a sequential component in a concurrent program. Each task deals with one sequential thread of execution; thus, no concurrency is allowed within a task. However, overall system concurrency is obtained by having multiple tasks executing in parallel. The tasks often execute asynchronously (i.e., at different speeds) and are relatively independent of each other for significant periods of time. From time to time, the tasks need to communicate and synchronize their operations with each other. Concurrent programming has been applied extensively in the development of operating systems, database systems, real‐time systems, interactive systems, and distributed systems.
Data Analysis
Authors: Wu Yi‐Hung , Chen Arbee L. P. 
Published: December 2007

Abstract
In this article, we describe the concepts and techniques of data analysis. Two categories, supervised data analysis and unsupervised data analysis, are first presented according to their different initial conditions and resultant uses. Two methods for data analysis are then described and illustrated by examples, which are based on probability theory and fuzzy‐set theory, respectively. Following this introduction of the fundamental data analysis methods, the methods for data analysis on two types of Internet data, web page and web log, are presented. Further discussions on advanced methods for Internet data analysis are then provided, which are based on rough‐set theory and association mining concepts. Finally, we bring this article to a conclusion with the research trends highlighted.
Data Structures and Algorithms
Authors: Oliveira Carlos A.S. , Pardalos Panos M. , Prokopyev Oleg A. 
Published: December 2007

AbstractAlgorithms and data structures are the basic building blocks employed in computer sciences research and applications. We present the fundamental concepts in the area of analysis of algorithms and data structures. The concept of abstract data type is introduced, along with some useful data types such as lists, queues, stacks, trees, and graphs. More advanced data structures are also mentioned along with applications where they occur. Techniques for algorithm construction, including divide and conquer, dynamic programming, and backtracking, are introduced. Standard algorithms are presented, such as sorting, searching, and matrix multiplication. Finally, more advanced topics such as approximation algorithms, parallel algorithms, and randomized algorithms are discussed.
Deductive Databases
Authors: Grant John , Minker Jack 
Published: December 2007

AbstractIn this article define the concept of deductive database including the formal definition of a query and an answer to a query; we provide an historical background for deductive databases; we explain the different types of deductive databases starting with Datalog and including stratified, nonstratified, extended, and disjunctive deductive databases; we discuss various semantics for deductive databases; we list the prototypes and implementations of deductive databases; we also give several applications that cannot be handled by relational and databases and require deductive databases.
Embedded Operating Systems
Authors: Mo Albert , Cheng Kim 
Published: December 2007

Abstract
Many of the systems and devices used in our modern society must provide a response that is both correct and timely. More and more computer systems are built as integral parts of many
of these systems to monitor and control their functions and operations. These embedded systems often operate in environments where safety is a major concern. For real‐time embedded applications in which task deadlines must be satisfied, a real‐time operating system (RTOS) with an appropriate scheduler for scheduling tasks with timing constraints must be used. This article introduces the basics of RTOSs, covering task synchronization, scheduling, memory management, and input/output.