bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scale Inhibitors for Geothermal Applications
Authors: Guan Hua 
Published: May 2012

Abstract
Siliceous scaling deposition from geothermal brine is recognized as detrimental to the smooth operation of steam generation and injection facilities; the control of such deposition is costy and less well understood. Scales normally encountered in geothermal wells are often different from the conventional cases. Silica (amorphous and colloidal) and poor crystallized metal silicates are the most common scale types in geothermal applications.
There are a number of ways to control this type of scaling, including both engineering (e.g. maintain pressure and temperature) and chemical means (e.g. controlled precipitation and inhibition). This paper will focus on preventative techniques by the use of chemical inhibitors.
Currently there are no standard or generally accepted laboratory test methods to study these types of fouling problems. However, using a low-pressure test method and testing apparatus, we are able to rank the scaling inhibition performance of several generic chemicals. Furthermore, the chemical was successfully packaged into formulations that are suitable to a specific geothermal well condition where large amount of iron are present, complicated with the codeposition of barium sulphate scale. The mechanisms of silica/metal silicate scale formation and inhibition, including the verification test using a HPHT apparatus for this geothermal application, are discussed in this paper.
Modeling the Thermodynamic Properties of Common Minerals at High Temperature, Pressure and Salinity with Complex Ions
Authors: Shi Wei , Lu Haiping , Zhang Nan , Fan Chunfang , Kan Amy T. , Tomson Mason B. 
Published: May 2012

Abstract
The ultra-high temperature (150–250°C), pressure (1,000–2,000 bar, 15,000 to 30,000 psi) and TDS (&gt;300,000 mg/L) in deepwater oil and gas production pose significant challenges to scaling control due to limited knowledge of mineral solubility, kinetics and inhibitor efficiency at these extreme conditions. Prediction of thermodynamic properties of common minerals is currently limited by lack of experimental data and inadequate understanding of modeling parameters. In this study, a new apparatus was built to test scale formation and inhibition at high temperatures and pressures. Solubilities of two common minerals, barite and calcite, were tested at temperature up to 250°C, pressure up to 1,500 bar (22,000 psi) and ionic strength up to 6m in solutions with elevated concentrations of mixed electrolytes (e.g., calcium, magnesium, sulfate and carbonate) representing the maximum range of interferences expected (95%CI) in oil and gas wells. As an attempt towards experimentally determining mineral solubility at high temperature, pressure and salinity, not only does this study contribute to the extremely limited data base, but it also provides a reliable approach for evaluating and adjusting model predictions at extreme conditions. Predictions by a thermodynamic model based on Pitzer's ion interaction theory were evaluated using experimental data. The dependence of Pitzer's coefficients for ion activity coefficients on temperature and pressure was examined and incorporated into the scale prediction model, whose prediction is consistent with both experimental and literature data at all conditions tested.
Coupled Adsorption/Precipitation Experiments: 1. Static Results
Authors: Ibrahim J. , Sorbie K. S. , Boak L. S. 
Published: May 2012

Abstract
The mechanism of retention of scale inhibitors (SI) within the reservoir formation is central to a squeeze treatment having a long lifetime. Scale inhibitors are retained within porous media by the two main mechanisms of adsorption (Γ) and precipitation (∏). There is not complete agreement in the literature about when we should use one mechanistic description or another, and indeed both can occur together as coupled adsorption/precipitation (Γ/∏). Previously a general model of coupled (equilibrium) adsorption/precipitation has been derived and the agreement between the model and experiment was very good (Kahrwad et al., 2008). This model was subsequently extended to derive a consistent dynamic coupled Γ/∏ flow model for simulating non-equilibrium (kinetic) coupled processes of any type (Sorbie, 2010). This latter model has not yet been fully validated, but the work in this paper and its companion paper (Paper 2: Ibrahim et al, 2010) provides the type of data required in order to do this.
In this paper (Paper 1), new static experimental adsorption/precipitation measurements are presented for two phosphonate inhibitors, DETPMP (a penta-phosphonate) and OMTHP (a hexa-phosphonate) using sand, kaolinite and siderite as the mineral phases. These experiments were carried out at a range of adsorbent mass (m)/ fluid volume (V)/ ratios and it is the "apparent adsorption", Γapp vs. the final scale inhibitor concentration, cf, which is measured and plotted. By observing how the Γapp vs. Cf, curves vary for different values of the (m/V) ratio, this indicates whether we are in the purely adsorbing (Γ) or in the coupled adsorption/precipitation (Γ/∏) regime (Kahrwad et al., 2008). For these static apparent adsorption tests, m = 10g, 20g and 30g samples of each mineral were used (with a fixed volume of SI solution, V = 80ml) to analyse the apparent adsorption behaviour. In addition, related pure precipitation/compatibility tests were carried out in the absence of any minerals in the bulk solutions. The experimental results for both phosphonate scale inhibitors show good agreement with the theory in different regions of pure adsorption and coupled adsorption/precipitation. These results show clearly how such laboratory measurements should be carried out to determine both the levels of SI retention and the precise retention mechanism. This paper characterizes the systems used in subsequent dynamic adsorption/ precipitation sand pack floods which are reported in a related paper (Ibrahim et al., 2012) and which will be used in future to validate fully dynamic coupled Γ/∏ flow models (Sorbie, 2010).
A New Correlation to Predict the Stoichiometry of Mixed Scale: Iron-Calcium Carbonate
Authors: Alsaiari H. A , Zhang N. , Work S. , Kan A. , Tomson M. B. 
Published: May 2012

Abstract
Calcium carbonate and iron carbonate scales are widely observed in oil and gas production. Scale formation can be useful for corrosion control; however, excessive scale buildup can lead to severe production loss. What is called calcite scale in the field is almost always a solid solution of iron in calcite. Yet little attention has been paid to the precipitation of these mixed calcium-iron carbonate scales. As a result, knowledge of the formation and inhibition of mixed calcium/iron scales is very limited.
Normally, calcite scale formation is readily inhibited, whereas siderite inhibition is notoriously difficult. The solid-solution transition from predominantly calcite to predominantly siderite properties is unknown. Besides, although the solubility of mixed scale can differ by several orders of magnitudes from the solubility of its pure salts, scale prediction models are normally developed based on the data from pure solids. Finally, the incorporation of iron into calcite solid dramatically alters the kinetics of scale growth, as will be illustrated.
A series of experiments were performed to precipitate mixed iron-calcium carbonate (FexCa1−XCO3), ranging from calcium-rich to iron-rich. The experiments were conducted at 7.3±0.2 pH in 0.5 M NaCl at 55 °C. The work was performed with a new constant composition method, modified to handle oxygen sensitive ferrous carbonate scale and solid solutions.
Based upon the experimental results and a flux-based theoretical derivation, a new correlation in a form of a logistic function has been developed to predict the composition of FexCa1−xCO3 as a function of the aqueous composition. The model is an excellent representation for all of the experimental results, with R2 greater than 0.97. The correlation and methods developed in this work can readily be adapted to other mixed scale systems. Laboratory results will be compared with field observations and the consequences discussed.
Impact of Reservoir Reactions on Thermodynamic Scale Predictions
Authors: Gomes R. M. , Mackay E. J. , Deucher R. H. , Bezerra M. C. , Rosário F. F. , Jordan M. M. 
Published: May 2012

Abstract
Evaluation of the scaling risk at production wells is generally carried out using thermodynamic prediction models. These models are generally very accurate in terms of predicting the type of scale that may form, the degree of supersaturation, and the mass of scale that will deposit by the time the system reaches equilibrium – provided the brine composition or compositions involved are well known, and the pressure and temperatures conditions are accurately specified. However, in performing these calculations, engineers and chemists often fail to take account of reactions occurring in the reservoir, and assume that brines reaching the production wells have not reacted in any way prior to entering the wellbore. This often leads to a significant overestimate of the scaling risk.
The work presented in this paper addresses this issue by studying data from various fields to identify what can be learnt from the produced brine compositions. A new technique to estimate the range of scaling tendencies that takes account of reservoir precipitation is developed, and the results are displayed in a 3D response surface. This is illustrated for barium sulphate scaling tendency, accounting for different levels of ion stripping.
In order to calibrate some simulation parameters, and to identify the more important equations that should be inserted in the reservoir simulation, studies were performed based on the observed data. Different reservoir simulations were used and compared, with a focus on scale management to identify positive and negative aspects of each one.
This work has identified that in fields with reservoir temperatures above 120°C and calcium concentrations above 7000 mg/l, significant sulphate stripping occurs due to anhydrite precipitation. This effect is increased where ion exchange leads to a reduction in magnesium and an increase in calcium concentration as the injected brine is displaced through the reservoir.
Innovative Integrated Procedure for Scale Removal in Khuff Gas Wells in Saudi Arabia
Authors: Bolarinwa Simeon , Jauregui Jairo Leal , Buali Mustafa , Aramco Saudi , Kharrat Wassim , Kovalenko Kirill 
Published: May 2012

Abstract
Many Khuff gas wells have been experiencing inorganic scale deposits: iron sulfide, iron oxides and calcium carbonate, which are causing weak production and poor wellbore accessibility. The scale problem requires a prompt solution to meet Saudi Aramco gas production objectives.
The history of scale removal trials in Khuff gas wells in Saudi Arabia included the mechanical removal with Coiled Tubing (CT), and the chemical dissolution with acid and/or other scale dissolvers pumped through CT or bullheaded. All these methods failed to provide the expected outcome and some jobs resulted in major operational failures like stuck pipe, pinholes, H2S release at surface, and formation damage. As a result of these failures the descaling jobs were put on hold by Saudi Aramco many times between 2007 and 2010 with no significant progress made until the 2nd half of 2010.
A project was launched to establish an innovative descaling procedure aimed at a safe and effective scale removal. The integrated solution starts with the temporary isolation of the reservoir to eliminate gas and H2S returns at surface, enable a "closed system" cleanout with safe solid handling at low choke pressure, and minimum surface testing equipment. The second step is based on mechanical removal that eliminates long soaking time and/or H2S generation during chemical dissolution. For that, a high pressure jetting tool designed and proved to remove hard scale is deployed on CT. The critical step of scale cleanout to surface is optimized with the use of large outside diameter CT string and special high temperature gel to ensure efficient lift and eliminate the risk of stuck pipes. The major enhancement to this project is the ability to monitor in real-time bottom-hole pressure and temperature, annular solid concentration, and the high pressure jetting tool efficiency with a fiber optic enabled coiled tubing string. The whole process resulted in a controlled and optimized scale removal treatment.
Multiple case histories are presented in this paper to demonstrate the successful implementation of the integrated solution, which is then selected as the only approved method for scale removal in Khuff gas wells.
Modelling Squeeze Treatments of Fractured Reservoir Zones
Authors: Stalker Robert , Wright Rob , Fitzpatrick Rob , Graham Gordon 
Published: May 2012

Abstract
The presence of fractured reservoir zones presents significant challenges for the modelling and optimisation of squeeze treatments. Fluid flow in fractured systems is relatively well understood, and the effect of fractures on the placement of chemical can be modelled. However, to model the quantitative effects of fractures on scale inhibitor returning from squeezed zones, it is necessary to also model the retention and release of inhibitor from a fractured zone. This involves modelling the flow of inhibitor between fracture and matrix, while modelling the retention and release of inhibitor by the rock matrix.
Using conventional near wellbore squeeze simulators (Place iT v5), artificially induced fractures have been simulated using a near wellbore dual permeability approach more commonly used to model wells with a skin factor. The method has been extended from single fractured intervals to dual intervals/zones and the competitive placement of chemical between the fractured zones has been modeled.
The work shows how the predicted chemical placement and the resulting inhibitor return lifetimes can be simulated in fractured wells and how the sizing of the overflush can be more significant than simply accounting for the fracture volume. The mathematical concepts and assumptions used in the model development are presented.
Naturally fractured reservoirs present a special challenge both from the practical scale-management and theoretical (predictive modelling) points of view. Whereas useful conclusions can be drawn using simplified models, more physically meaningful modeling of fracture/matrix interaction is required for the more challenging wells. Rock matrix – fracture interaction can be accounted for using analytical methods including important processes such as molecular diffusion i.e. to account for rock / chemical / fluid imbibition and diffusion. The development of modeling capabilities for such systems is outlined and results from simulations compared with those conducted using more conventional though less rigorous approaches.
Has the Widespread Adoption of IFRS Reduced U.S. Firms' Attractiveness to Foreign Investors?
Authors: DeFond Mark L. , Hu Xuesong , Hung Mingyi Y. , Li Siqi 
Published: May 2012

ABSTRACT
Widespread adoption of IFRS has fueled debate about whether its dominance puts U.S. firms at a competitive disadvantage in attracting global investors. We examine this issue by looking at the change in foreign mutual fund investment in U.S. companies after 2005, the year in which IFRS surpassed U.S. GAAP as the world's most commonly used accounting standard. We find that while foreign investment in U.S. companies is essentially flat over our sample period, it declines relative to foreign investment in EU IFRS adopters. Foreign investment also declines in U.S. companies that experience large increases in IFRS industry peers relative to U.S. companies that experience small increases. In addition, the relative decline is concentrated among mutual funds that do not specialize in U.S. stocks, and is greater for smaller U.S. firms. Overall, our results suggest that the worldwide adoption of IFRS reduces U.S. firms' relative attractiveness to foreign investors.
Data Availability: All data are publicly available from sources indicated in the text.
The effects of domestication on the scaling of below‐ vs. aboveground biomass in four selected wheat (Triticum; Poaceae) genotypes
Authors: Qin XiaoLiang , Niklas Karl J. , Qi Lin , Xiong YouCai , Li FengMin 
Published: May 2012

• Premise of the study: Theory and empirical studies have shown that, on average, belowground biomass (MB) scales one‐to‐one (isometrically) with aboveground biomass (MA) within and across plant species both at the individual and population level, i.e., MB ∝ MAα=1, where α is the scaling exponent. However, little is known about how domestication affects this relationship.• Methods: To examine the effects of domestication, we investigated the root vs. shoot biomass relationship during the first 30 d of growth of four wheat genotypes: two older genotypes, MO4 (T. monococcum, a diploid) and DM31 (T. dicoccum, a tetraploid) and two more recent genotypes, DX24 and L8275 (T. aestivum, both hexaploids).• Results: Biomass allocation to roots scaled more or less isometrically with respect to shoot biomass allocation during the first 30 d of growth for both of the older genotypes, whereas shoot biomass allocation exceeded root allocation for the two more recent genotypes. This difference was attributable to the first 15 d of growth. Although root biomass allocation exceeded shoot biomass allocation during the first 15 d of growth for the two older genotypes, shoot biomass exceeded root biomass allocation during this critical phase of development for the two more recent genotypes.• Conclusions: Based on a very limited sample of wheat genotypes, these results indicate that domestication has resulted in an increased biomass allocation to shoots compared to root biomass allocation. This shift possibly reflects artificial selection under agricultural conditions (for which water and nutrients are not limiting) favoring higher crop yields.
Doublage d’un extrait de Volver d’Almodóvar et modification du scénario
Authors: Gilet Gaïdig 
Published: May 2012

L’activité proposée s’adresse à des élèves de 3e et a pour support un extrait du film d’Almodóvar, Volver. Les tâches finales consistent en une modification du scénario initial et en un travail de doublage. Toutes les compétences du Cadre européen commun de compétences pour les langues : apprendre, enseigner, évaluer (CECRL)1 sont travaillées dans cette activité qui permet un travail ludique et créatif autour du cinéma.
Chronic Lymphocytic Inflammation With Pontine Perivascular Enhancement Responsive to Steroids Following Influenza Vaccination
Authors: Hillesheim Paul B. , Parker John R. , Parker Joseph C. , Escott Edward , Berger Joseph R. 
Published: May 2012

Inflammatory processes within the central nervous system are challenging for the clinician, radiologist, and pathologist alike. They often can mimic other more well-known and defined disease processes. We present the case of a patient with a newly described inflammatory process that primarily involves the pons and adjacent structures, which is called chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS). An 80-year-old man presented with numbness of his right hand that ultimately progressed to involve both lower extremities and face and was associated with mild dysarthria and ataxia. He had received the influenza vaccination 2 weeks prior. The biopsy revealed primarily reactive T-cell lymphocytic infiltrates with macrophages and gliosis. Treatment required long-term immunosuppressive therapy. CLIPPERS is a recently described central nervous system inflammatory condition that should be considered in the differential diagnosis when a prominent lymphocytic inflammatory infiltrate is encountered in brainstem, spinal cord, midbrain, or cerebellar biopsies.
Development of Nanomaterials for SALDI‐MS Analysis in Forensics
Authors: Lim Angelina Yimei , Ma Jan , Boey Yin Chiang Freddy 
Published: May 2012

AbstractWithin the last decade, the escalation of research output in the field of nanotechnology has spurred the development of new nanomaterials for use as assisting agents in surface assisted laser desorption ionization mass spectrometry (SALDI‐MS). Specifically modified nanomaterials, coupled with mass spectrometry, have improved the detection sensitivity, specificity, flexibility and reproducibility of SALDI‐MS analysis. The technological advancement of LDI‐MS has in turn, propelled the use of the analytical technique in the field of forensics. In this report, the various roles and applications of metal‐, silicon‐ and carbon‐based nanostructured materials as SALDI matrices in the analysis of forensic samples are described. The advantages of SALDI‐MS as an analytical tool for forensic sample analysis are also discussed.
Synthesis of Dibenzothiophenes and Carbazoles by Sequential ‘Tetra‐Fold Heck/6 π‐Electrocyclization/Dehydrogenation’ Reactions of Tetrabromothiophene and Tetrabromo‐N‐methylpyrrole
Authors: Toguem Serge‐Mithérand Tengho , Knepper Ingo , Ehlers Peter , Dang Tung T. , Patonay Tamás , Langer Peter 
Published: May 2012

AbstractDibenzothiophenes and carbazoles were prepared by tetrafold Heck reactions of tetrabromothiophene and N‐methyltetrabromopyrrole and subsequent 6π‐electrocyclization and dehydrogenation. A number of reactions could be successfully carried out as domino reactions in only one synthetic step.
Asymmetric Homogeneous Hydrogenation in Flow using a Tube‐in‐Tube Reactor
Authors: Newton Sean , Ley Steven V. , Arcé Eva Casas , Grainger Damian M. 
Published: May 2012

AbstractIn this update, the asymmetric homogeneous hydrogenation of a number of trisubstituted olefins utilizing the recently developed tube‐in‐tube gas‐liquid flow reactor is described. A number of chiral iridium‐ and rhodium‐based catalysts and other parameters such as pressure, solvent, temperature and catalyst loading were screened. The advantage of the flow set‐up for rapid screening and optimization of reaction parameters is illustrated. Furthermore, a comparative study using batch conditions aided in the optimization of the flow reaction set‐up. The set‐up was further modified to recycle the catalyst which prolonged catalytic activity.
Identifying the Nature of Charge Recombination in Organic Solar Cells from Charge‐Transfer State Electroluminescence
Authors: Wetzelaer Gert‐Jan A. H. , Kuik Martijn , Blom Paul W. M. 
Published: May 2012

AbstractCharge‐transfer (CT) state electroluminescence is investigated in several polymer:fullerene bulk heterojunction solar cells. The ideality factor of the electroluminescence reveals that the CT emission in polymer:fullerene solar cells originates from free‐carrier bimolecular recombination at the donor‐acceptor interface, rather than a charge‐trap‐mediated process. The fingerprint of the presence of nonradiative trap‐assisted recombination, a voltage‐dependent CT electroluminescence quantum efficiency, is only observed for the P3HT:PCBM system, which is explained by a reduction of the competing bimolecular recombination rate. These results are in agreement with measurements of the illumination‐intensity dependence of the open‐circuit voltage.