bluuebunny/crossref_metadata_2025 huggingface dataset:
Successful Deployment of a Green Multifunctional Scale Inhibitor, A Case Study From the Rockies
Authors: Spicka K. J. , Hirst M. C. , Hochhalter G. E. , Steppler D. J. , Haag J. T.
Published: May 2012

This paper will highlight the effectiveness of a novel, environmentally friendly multifunctional polymeric scale inhibitor that inhibits carbonate and sulfate scales as well as halite.

The deposition of halite in the oilfield can present a challenge for operators in fields with high TDS brines. The large amounts of halite that can deposit in a short amount of time can lead to reduced production as well as a costly and logistically cumbersome remediation. A customer was controlling halite deposition by injecting a low salinity water source to dilute/dissolve the deposits. However, this remedial solution also presented an additional problem to the customer as the injection of the fresh water source led to calcium carbonate deposition due to brine incompatibility.

This paper will present laboratory test results which highlight the effectiveness of this novel multifunctional scale inhibitor against halite, carbonate and sulfate scales. These results will be compared to traditional scale inhibitors. Following laboratory testing, this environmentally acceptable scale inhibitor product was deployed in high TDS wells where halite deposition was occurring. This paper will also demonstrate the successful implementation of the product, which provided calcium carbonate inhibition and a reduction in the volume of fresh water needed for control of halite deposition. This reduction in water consumption led to significant cost savings for the customer.

The value this case study brings to the industry is an overview of the challenges halite and associated scales present to hydrocarbon recovery and the development/implementation of a multifunctional molecule rather than a chemical blend for scale control. Results of this paper have implications for other fields across the world where halite scale is a flow assurance challenge.
Phosphorus Functionalised Polymeric Scale Inhibitors, Further Developments and Field Deployment
Authors: Todd M. J. , Thornton A. R. , Wylde J. , Strachan C. J. , Moir G. , Goulding J. R.
Published: May 2012

As the oil and gas industry strives to replace ageing, environmentally undesirable scale inhibitors there is an ever increasing use of polymeric inhibitors. Incorporation of phosphorus functionality into a polymer backbone has been shown to improve inhibition efficiency, enhance adsorption characteristics and allow the polymer concentration to be analysed by elemental phosphorus. It is known that some phosphorus tagged polymers can be problematic to analyse in oil field brines as they typically have a low phosphorus content which is difficult to determine from the background.

The development of novel phosphorus functionalised polymeric scale inhibitors was previously described (SPE 130733). This paper follows the development of the inhibitor class. Utilising extensive laboratory testing the interactive nature of the scale inhibitors and reservoir lithology was studied. These novel phosphorus functionalised inhibitors were compared to a number of other available P-containing polymers.

Following successful development, one of the phosphorus functionalised polymeric inhibitors was subject to sequential field-trial in a harsh BaSO4 scaling, highly naturally fractured North Sea carbonate reservoir. The phosphorus functionalised inhibitor provided improved performance compared to the incumbent product. Following the successful deployment in a carbonate reservoir the novel inhibitor class was also deployed in a number of North Sea sandstone reservoirs and one field wide case study is reported with details on the innovative management and implementation strategy presented. Focus has been given to the application of these products and a detailed analysis of field proven benefits given.

This paper concludes with a detailed comparison of these Phosphorus functionalized scale inhibitors with the incumbent products they have replaced in the case histories described. The benefits that these novel, innovative products have given to the operator are described along with a technical synopsis of incremental performance benefits.
Qualification Procedure For Continuous Injection Of Chemicals In The Well -Method Development
Authors: Goodwin Neil J. , Svela Odd Geir , Olsen John Helge , Tjomsland Tore , Hustad Britt Marie , Graham Gordon M.
Published: May 2012

Method development of laboratory bench and rig tests for assessing the suitability for application of chemicals via down-hole pressure tube systems is presented. Areas of interest include precipitation or viscosity changes due to solvent loss both in bulk samples and samples in capillaries, and long term product stability in capillaries using new flow rigs designed to more fully replicate pressure tube injection phenomena (particularly chemical stability under extreme T and P conditions). Indeed fluid stability and other challenges relating to down-hole continuous injection have led to a number of failures being recorded in recent years indicating that the physical properties rather than the absolute performance of the chemicals is often key to their successful deployment.

Continuous chemical injection systems for down-hole application are being included in more well completions as their usefulness is recognised. While the initial capital costs are increased, such systems provide a number of benefits over reliance on squeeze treatments for down-hole application. These may include the opportunity to use chemicals unsuitable for squeeze treatment due to the risk of formation damage, the ability to maintain higher doses, and avoiding the need to interrupt production to apply chemicals in complex subsea wells.

Using the developed methods we have identified a number of ways in which formulated scale inhibitors may produce problems within continual injection systems. These include particulate formation and line plugging in capillaries, and solid formation or viscosity increases in response to solvent loss within a tube (as opposed to bulk samples).

These methods will form the basis for future qualification procedures for chemicals intended for down-hole chemical injection with the aim of avoiding application issues in the field. They have been developed both to better understand chemical / fluid stability under down-hole continuous injection conditions following a number of recorded field deployment problems, and then to provide improved qualification for new chemicals and systems.
New Polymer Chemistry for Squeeze Application in Tight Carbonate Reservoirs
Authors: Chen Tao , Heath Steve , Benvie Ronald , Chen Ping , Montgomerie Harry , Hagen Thomas
Published: May 2012

The development of effective scale squeeze inhibitors in carbonate reservoirs is still a big challenge, especially with the increasing environmental constraints. For tight carbonate reservoirs, formation damage is one of the major considerations as it can be caused due to fines mobilization, carbonate reservoir dissolution and collapse, and scale inhibitor compatibility issues. For the development of any product for squeeze application, the product must also demonstrate good inhibition performance, long squeeze life and accurate residual analysis at low concentrations as well as being suitable for improved placement techniques if required.

Many scale inhibitors are either irreversibly retained in chalk reservoirs due to uncontrolled precipitation reactions or are poorly adsorbed with both processes resulting in short treatment lifetimes. Some new, readily detectable, polymeric scale inhibitor chemistry, containing a special functional amine group to have a good affinity to the chalk reservoir, was developed to provide a balance between irreversible and poor retention and thus provide effective squeeze life.

The results of a comprehensive testing program, including compatibility, formation dissolution, dynamic tubing blocking, static adsorption and core flood tests will be presented, that will highlight the design and development of a polymeric scale inhibitor suitable for tight carbonate reservoirs while meeting the environmental requirements for application in the UK and Scandinavia.

The new polymer has been shown to demonstrate excellent retention and release characteristics while also being non-damaging to carbonate reservoir material. The impact of calcium tolerance, pH and molecular chemistry will be discussed with regard to the design and performance of the new polymer when compared to some environmentally friendly phosphonate chemistry and other polymeric scale inhibitors.

This paper will demonstrate a logical design procedure to develop an environmentally acceptable polymeric scale inhibitor product whose chemistry has been optimised for squeeze application in tight carbonate reservoirs. In addition, discussions on the mechanisms of scale inhibitor retention and formation damage with regard to selection, design and optimization of suitable scale squeeze inhibitors in tight carbonate reservoirs will be addressed.
Elemental Sulphur Induced Formation Damage Management in Gas Reservoir
Authors: Adesina Fadairo , Churchill Ako , Olugbenga Falode
Published: May 2012

Sulphur compounds are considered as the most hazardous non-hydrocarbons in reservoir fluids, because of their corrosive nature, deleterious effects of petroleum products and tendency to plug porous medium which may impair formation productivity. Precipitation and deposition of elemental sulphur within reservoirs, near well bore region may significantly reduce the inflow performance of sour-gas wells and thus affect economic feasibility negatively.

Studies have sought that almost all deep sour reservoirs precipitate elemental sulphur either occurring as a result of decomposition of H2S to give elemental sulphur or occurring as indigenous usually referred to as native sulphur as a dissolved species. Uncontrollable elemental sulphur induced formation damage has been one of the profit hurting syndromes that occurs in deep water sour gas reservoir.

Meanwhile many correlations have been formulated thermodynamically to predict the occurrences of elemental sulphur but little information related to effect of its saturation on gas production and its corresponding formation damage.

This paper presents an improved model for predicting elemental sulphur saturation and corresponding formation damage around the well bore. Results show that the minimum pore spaces blockage time was over-estimated by previous formulation.
Effects of Hydrate Inhibitors on the Solubility of Barite and Halite in Produced Water
Authors: Djamali Essmaiil , Lu Haiping , Kan Amy T. , Tomson Mason B.
Published: May 2012

Large quantities of hydrate inhibitors, such as methanol, MEG (ethane 1, 2 diol), and TEG (triethylene glycol) are used to prevent gas hydrate formation during production from a gas/oil well. Due to environmental and economic concerns, MEG is often regenerated via a thermal vacuum distillation process. The hydrate inhibitors adversely enhance scale formation. The impact of temperature and concentration on mineral scale formation during MEG regeneration is largely unknown. The solubility of barite and halite in methanol/brine and MEG/brine solution was measured up to 473.15 K (200 °C ) and 6.6 MPa (1000 psia) to evaluate the impact of high temperature on mineral scale formation in hydrate inhibitor/brine solutions. A model is developed to assist the process design to prevent scaling risk during MEG regeneration. The "unified theory" of electrolytes developed by one of the authors (EDJ), for prediction of the standard state thermodynamics properties of electrolytes to extreme temperatures and pressures, has been adapted to model the effect of temperature and pressure on mineral salt solubility in methanol, ethanol and MEG/brine solutions. The model requires knowing the Gibbs free energy of hydration at some temperature, usually 298.15 K (25 °C), and only two previously determined constants for each electrolyte. Once these constants are fixed, the model can be used to predict the standard state partial molar Gibbs free energies of electrolytes up to supercritical temperatures. The temperature and pressure behavior of electrolytes can now be accurately predicted from existing low temperature data alone. A modification of Pitzer's model for activity coefficients is also used to account for the effect of mixed electrolytes on solubility in cosolvent/brine systems. The combined model will be applied to typical reboiler systems in use on off-shore platforms and on shore.
A Novel and Comprehensive Study of Polymeric and Traditional Phosphonate Inhibitors for High Temperature Scale Control
Authors: Wang Wei , Kan Amy T. , Tomson Mason B.
Published: May 2012

This paper presents a quantitative study of scale inhibitor thermal stability with regard to their potential application in high temperature wells. Systematic experiments have been conducted to investigate: (1) the influence of thermal aging on phosphonate and polymeric inhibitors at 200 °C, (2) the time (minutes to days) and temperature (up to 200 °C) dependence of inhibitor thermal degradation, (3) the impact of stainless steel and iron on the degradation of inhibitors at high temperatures, (4) the difference in aging tests with inhibitors in solution and that adsorbed on core materials, and (5) the effectiveness of a chelating agent to prevent the catalytic degradation of scale inhibitor by metal ions. The results enable a more accurate understanding of thermal degradation and provide a comprehensive guidance on the selection and placement of scale inhibitors for high temperature oil and gas production.
Coupled Adsorption/Precipitation Experiments: 2. Non-Equilibrium Sand Pack Treatments
Authors: Ibrahim J. , Sorbie K. S. , Boak L. S.
Published: May 2012

Scale inhibitors (SI) are retained in the reservoir formation by both adsorption (Γ) and precipitation (Π) mechanisms, and these are responsible for the duration of the squeeze lifetime. However, processes such as the adsorption of SI and dissolution of precipitated SI complexes are not instantaneous. During a scale inhibitor treatment in a rock core, the fluid/mineral contact time may be quite short compared to the equilibrium time for the SI/mineral system for many practical experimental flow rates. This is also the case in the near-wellbore region where flow rates are very high and hence dynamic (non-equilibrium) effects may be significant. The SI retention process occurring in the sand packs, and indeed within the reservoir formation, are therefore likely to be non-equilibrium processes for at least some period of the squeeze process. If this hypothesis is correct, non-equilibrium behavior can be observed from the change in observed SI effluent concentrations as the flow rate changes in the sand pack flood. Therefore, non-equilibrium effects must be taken into account in the derivation of the parameters governing the squeeze such as the adsorption isotherms and/or the precipitation/dissolution model.

In this paper, we present a range of novel experimental results from a series of variable rate adsorption and precipitation sand pack floods for OMTHP ( hexaphosphonate) scale inhibitor. The sand pack experiments were conducted using silica sand as the adsorbing mineral and all the floods were conducted using identical procedures. The unique feature of this series of floods is that the bulk coupled adsorption/precipitation behaviour of this system (OMTHP/sand) has been fully characterized in previous work (Paper 1, Ibrahim et al., 2012). Therefore, we know precisely when the system is in the "adsorption only (Γ)" or in the "coupled adsorption/precipitation (Γ/Π)" regime. The sand pack effluent results show non-equilibrium behavior as the flow rate changes. These results indicate the importance of flow rate on the derivation of dynamic isotherms (Γ) and precipitation models (Π) prior to field application modeling. We believe that the results presented in this work probably yield the most complete dataset of well characterised adsorption/precipitation SI pack floods assembled to date.
The Relation Between Barite Inhibition by Phosphonate Scale Inhibitors and the Structures of Phosphonate-Metal Complexes
Authors: Shaw S. S. , Welton T. D. , Sorbie K. S.
Published: May 2012

In produced waters from fields undergoing seawater (SW) flooding, inhibiting mineral scaling can be problematic because the SW/formation water (FW) ratio is constantly changing. For barium-sulfate scale, for example, the barite saturation ratio (SR), the yield of barite precipitate, and the molar ratio Ca2+/Mg2+ in the produced waters all evolve over time. This paper describes the effects of SR and molar ratio Ca2+/Mg2+ on the barium-sulfate inhibition efficiency (IE) of nine phosphonate scale inhibitors (SIs): OMTHP (hexa-phosphonate), DETPMP and HMTPMP (penta-phosphonates), HMDP and EDTMPA (tetra-phosphonates), NTP (tri-phosphonate), EABMPA and HEDP (di-phosphonates), and HPAA (mono-phosphonate and mono-carboxylate). IE experiments were carried out testing a range of SW/FW compositions (i.e., SR and molar ratio Ca2+/Mg2+ varying). The minimum inhibitor concentration (MIC) level of these phosphonate SIs might correlate with either the level of SR for the SW/FW mixing ratio in question (Type 1) or the Ca2+ and Mg2+ levels in solution (Type 2).

When experiments were repeated, but the produced brine molar ratio Ca2+/Mg2+ was fixed, the MIC for both Type 1 and Type 2 species always correlated with the SR. The performance of these phosphonate SIs in consumption experiments, where supernatant [SI] and [Ba2+] are both assayed by inductively coupled plasma (ICP) spectroscopy at multiple residence times, is also briefly discussed. In this paper, the reasons behind Type 1 and Type 2 IE behavior in phosphonate SIs are discussed, in terms of SI molecular structure, pH, SI speciation, SI binding constants to Ca2+ and Mg2+ cations, and the possible mononuclear or polynuclear chelate structures with M2+ cations that can form under the test conditions. Possible SI-M2+ complex structures are proposed, and through molecular modeling, explanations are provided for why Type 1 and Type 2 behavior is exhibited by phosphonate SIs.
Prediction of Mineral Scaling in a MEG Loop System of a Gas Production Offshore
Authors: Baraka-Lokmane S. , Hurtevent C. , Ohanessian J-L. , Rousseau G. , Seiersten M. , Deshmush S.
Published: May 2012

An offshore gas field located in the Far East has two reservoirs: reservoir A and reservoir B. Production fluids consist of gas and hydrocarbon condensate with some produced water from the two reservoirs. The producing fields are in water depths varying between 250 and 275m with ambient seawater temperatures and operating conditions that result in only occasional concerns about potential hydrate formation in the production systems. Lean Monoethylene Gylcol (MEG) is injected near the wellheads for hydrate inhibition.

This paper presents the risk of mineral scaling at critical points throughout the process with the three production scenarios: reservoir A alone, reservoir A and reservoir B, and finally reservoir B alone. Special attention has been put on the effect of mixing produced waters from reservoir A and reservoir B topside. Furthermore there are considerable uncertainties with respect to the amount of organic acids that may be produced; therefore some evaluations have been performed with and without organic acids.
Emerging 4th Generation Analytical Technology for the Individual Analysis of Multiple Families of Co-mingled Scale Inhibitors in Deepwater Wells
Authors: Thompson Alan , Gundersen Thomas E. , Andresen Alf Terje , Dahlgren Per Anders , Juliussen Bjorn
Published: May 2012

The individual analysis of polymeric scale inhibitors in co-mingled flow backs from wells in subsea and deepwater templates is a particularly challenging application for analytical techniques in the industry.

The application of the analytical technique of mass spectrometry to this challenge has resulted in routine 3rd generational analytical methods where a primary inhibitor can be quantified in the presence of a secondary subsea squeeze inhibitor and a tertiary topside scale inhibitor; something which had not been demonstrated previously in commercial applications. In more complex deep water field developments in the North Sea and Gulf of Mexico, where 4–8 wells can be co-mingled, the use of these third generation analytical techniques may not always be sufficient therefore it is necessary to develop improved methodologies to cope with the presence of an increasing number of chemical families.

This paper presents details of an emerging 4th generation analytical method which is being developed to allow the accurate quantification of 4–5 chemical families of scale inhibiting polymers in the presence of each other and other production chemicals such as corrosion and hydrate inhibitors. These would include scale squeeze polymers, scale inhibiting polymers applied subsea, or scale inhibiting polymers applied topsides. This method builds upon the 3rd generation analytical technology by using a novel mass detection technique which gives a much enhanced sensitivity and specificity to molecular functional groups.

The development of this method will add to the rich "toolbox" of state-of-the-art analytical techniques which now allow the analyst an unparalleled ability to generate accurate, specific and robust data from even the most demanding of applications and allow the chemical supplier and operator to individually monitor wells tied back to even the most complex of subsea templates in the most challenging of deepwater applications.
Selection of Anti-scale and Anti-corrosion Products: How to Avoid Interactions?
Authors: Gonzalez Marianna Rondon , Passade-Boupat Nicolas , Bascoul Paul , Baraka-Lokmane Salima , Hurtevent Christian
Published: May 2012

The injection of multiple chemicals, such as anti-scale and anti-corrosion additives, must often take place sequentially or simultaneously in very close injection points. Thus it is necessary not only to evaluate the efficiency of chemicals individually, but also to screen for incompatibilities and/or interference between chemicals. These interferences can affect either the anti-scale efficiency, the anti-corrosion efficiency, or even worth both additives efficiencies at the same time. This kind of mutual reduction of efficiency may have been the reason for past pipeline failures, where both scaling and corrosion were observed despite the addition of large quantities of both additives. Electrostatic interaction is a possible explanation, as the two chemicals carry opposite charges. In conjunction with the usual tests performed for additive selection, a physicochemical framework has been developed to evaluate the behavior of pairs of additives at different concentrations. For a model water presenting both corrosion and scaling issues, the efficiency of the anti-scaling additive is evaluated based on the quantification of free Ba2+ in solution by ionic chromatography and the efficiency of the anti-corrosion additive is assessed based on the change in the interfacial tension. Many candidate additives for oil field applications have been evaluated and "interaction maps" have been constructed. These maps indicate regions of concentrations at which one or both additives are not effective. These maps are useful for the selection of products that should be effective without risks of interactions. To finalize the validation, we can perform an "ultimate" blocking test where both additives, water and oil, are in contact at one point of the experiment, to also take into account the partitioning of additive between oil and water. This framework is not only useful for production chemistry studies of new field developments, but also for new product tenders in existing fields.
A 3-Year Results of Application a Combined Scale Inhibition and Hydraulic Fracturing Treatments using a Novel Hydraulic Fracturing Fluid, Russia
Authors: Levanyuk Olesya , Overin Alexander , Sadykov Almaz , Parkhonyuk Sergey , Lungwitz Bernhard , Enkababian Philippe , Klimov Alexander , Energy Imperial , Legeza Sergey
Published: May 2012

Scale deposits are a common problem in oil and gas wells and can have detrimental effects on well production. Depending on the severity, scaling can stop production entirely as scale forms anywhere in the well production system, including the formation, perforations, casing or tubular, and in or on the artificial lift equipment. There are several chemical and mechanical methods for removing scale deposits. However, to prevent scale deposition, the only solution is chemical inhibitors injected into the formation. The typical production system includes artificially lifted, stimulated wells (propped hydraulic fractures) placed in reservoirs where pressure maintenance is achieved by water flooding. The artificial lifting is typically accomplished through use of electric submersible pumps (ESPs). In reservoirs where produced fluids exhibit scaling tendencies, ESP run life is significantly shortened by scale formation on the pump elements restricting rotation. By treating the formation with chemical inhibitors, the life of the ESP can be extended.

In this paper we provide approaches for improving a compatibility of a novel hydraulic fracturing fluid (used in Russia) and scale inhibitor. A 3-year campaign to combine scale inhibition with the hydraulic propped fracture effectively increased the average run life of ESPs in the Mayskoe and Snezhnoe oil fields.
Scale Removal Operations in High Pressure High Temperature Tight Carbonate Reservoir and Sour Environment - Challenges and Guidelines
Authors: Almai Noura , Dashti Qasim , Baddula Ravi Chandra , Al-Awadi Mishari , Baloushi Taha , Aouchar Najet , Hamed-Naji Iyad , Metzger Thomas
Published: May 2012

Currently, Kuwait Oil Company (KOC) is successfully producing from high pressure and high temperature formations. The reservoirs are deep with True Vertical Depth (TVD) approximating 15,000 feet, and pressures and temperatures of 11,000 psi and 275° F respectively. The formations are composed of carbonates both tight and porous. The produced hydrocarbons are of high H2S and CO2 content, up to 10% and 12%, respectively.

The aforementioned sour environment in addition to water cut occurrence during the production phase have led to scale creation. In addition, corrosion, erosion and pitting also occur, requiring well intervention to sustain production. Furthermore, well monitoring is essential and planning for workover and well interventions is becoming unconventional with higher associated risk.

The recent scale removal activities proved to be very challenging with weight loss seen from the coiled tubing (CT) of approximately 7,000 Ib and CT leakage while operating at the hole condition. The CT pressure control equipment failed due to sudden increased in H2S concentration, which was attributed to the chemical reaction between the cleaning fluid (15% HCl) and the well fluids/scale mixture.

This paper explains the well history, objectives of operation, execution history, procedures and causes of these challenges. Hence, lessons learned, observations and knowledge gained by the Kuwait Oil Company (KOC) are evolving, advancing, and being employed at an accelerated rate despite high cost.
Development of Test Method and Environmentally Acceptable Inhibitors for Zinc Sulfide Deposited in Oil and Gas Fields
Authors: Wang Bin , Chen Tao , Chen Ping , Montgomerie Harry , Hagen Thomas , Liu Xuan , Yang Xu
Published: May 2012

Zinc sulfide (ZnS) is an exotic scale formed in the oil and gas fields, especially in HT/HP wells. It is relatively difficult to test ZnS formation and inhibition in the laboratory using traditional static jar and dynamic loop tests due to the oxidization during the test and its naturally ‘soft’ scale characteristic. Limited studies have been focused on ZnS and the detailed inhibition mechanisms are still unknown.

In this paper, a newly developed stress test method has been applied to evaluate the performance and mechanisms of ZnS inhibition. Compared with the traditional test methods, it shows good reproducibility and provides a quick and effective way to evaluate the performance of inhibitors and information to understand the mechanisms of inhibition.

More than 15 typical scale inhibitors, representing several different types, have been tested using this newly developed method. The ZnS scale inhibitors were classified as three types based on the inhibition mechanisms from this work:

Type 1: Dispersion and nucleation inhibitors. These scale inhibitors showed nucleation and growth inhibition effect at low concentrations of sulfide and dispersion effect at high concentrations of sulfide.

Type 2: Nucleation and growth scale inhibitors. These scale inhibitors inhibit nucleation and growth of ZnS formation, where the test can be stressed further.

Type 3: Scale inhibitors with poor performance on ZnS inhibition. The turbidity and stress curve did not change obviously in the presence of scale inhibitors.

This paper will give a comprehensive study of ZnS formation and inhibition, including scale prediction, development of test method and inhibitors, insight into the mechanism of ZnS inhibition and identification of environmentally acceptable inhibitors.
Understanding the Co-deposition of Calcium Sulphate and Barium Sulphate and Developing Environmental Acceptable Scale Inhibitors Applied in HTHP Wells
Authors: Liu Xuan , Chen Tao , Chen Ping , Montgomerie Harry , Hagen Thomas , Wang Bin , Yang Xu
Published: May 2012

Calcium sulphate and barium sulphate are two major scales experienced in the oil and gas fields, especially when sea water breakthrough in the waterflood supported HTHP wells. Normally, studies have been focused on a single scale component. Seldom studies have focused on the co-deposition of calcium sulphate and barium sulphate. The importance of interference between calcium sulphate and barium sulphate deposition in the field, especially for the HTHP wells, has been ignored.

In this paper, the interference between calcium sulphate and barium sulphate deposition has been studied based on a field case in the North Sea. The mechanisms of co-deposition have been addressed using both scale prediction and laboratory tests. Environmentally acceptable scale inhibitors have also been developed.

The scaling tendency and mass deposition of calcium sulphate and barium sulphate have been predicted with sea water breakthrough at different levels. The difference between calcium sulphate and barium sulphate, and the consequences of both types of scale deposition are discussed.

Dynamic scale loop tests have been carried out. It demonstrated that a small amount of barium sulphate deposit substantially accelerates the co-deposition of barium sulphate and calcium sulphate. Linked to the scale prediction, the mechanism of co-deposition of calcium sulphate and barium sulphate has been addressed.

Several scale inhibitors, including phosphonate and polymer based inhibitors, along with an amine based polymer have been tested under the worst case scaling condition. Environmentally acceptable scale inhibitors have been developed and are suitable for squeeze application.

This paper will give a comprehensive study of co-deposition of calcium sulphate and barium sulphate, including scale prediction, laboratory evaluation, mechanism discussion and inhibitor selection. It will contribute to understand calcium sulphate and barium sulphate scale deposition in HTHP wells and find effective inhibitors for field application.
Effective Laboratory Simulation of Scale Inhibitor Squeeze Treatments -Core to Field II
Authors: Graham Gordon , Stalker Robert , Hoeth Laurien Wichers , Kidd Samuel L. , Lagarde Frederic , Orski Karine
Published: May 2012

Coreflood experiments are an integral part of the selection and optimisation of scale inhibitor treatments, providing information on formation damage, inhibitor return profiles and dynamic retention isotherms. However, significant discrepancies can arise between core and field due to test methodology.

In a previous paper (SPE131131), we demonstrated that test methodology can have significant consequences for the comparative inhibitor returns, particularly with respect to oversaturation. The paper showed that many of the limitations can often be overcome through appropriate simulation techniques.

We extend this work and present further results of laboratory core flood tests specifically designed to examine the effect of core flood test methodology on the derived return isotherm, particularly examining the effect of injection of different volumes of main treatment ranging from ~ 0.5 pore volume (under saturated) to 20 pore volumes (over saturated) for a series of different generic scale inhibitors. This work clearly identifies the significant detrimental artefact of inhibitor oversaturation. This paper differs from the previous works (SPE 131131) in that examples are shown where core flood oversaturation can not be overcome with effective isotherm derivation and upscaling. This is due to significant differences in the isotherms derived as a function of the level of oversaturation with main treatment chemical. This paper will also demonstrate the impact of low concentrations of impurities and or the use of chemical blends when testing with poorly designed core flood tests.

Thus the paper directly addresses the procedures involved in core flooding, recommends approaches and test protocols which allow more appropriate product ranking and allow improved simulation from core to field.
Asymmetries in numerical density of pyramidal neurons in the fifth layer of the human posterior parietal cortex
Authors: Djukic-Macut Natasa , Malobabic Slobodan , Stefanovic Natalija , Mandic Predrag , Filipovic Tatjana , Malikovic Aleksandar , Saranovic Milena
Published: May 2012

Background/Aim. Both superior parietal lobule (SPL) of dorsolateral
hemispheric surface and precuneus (PEC) of medial surface are the parts of
posterior parietal cortex. The aim of this study was to determine the
numerical density (NV) of pyramidal neurons in the layer V of SPL and PEC and
their potential differences. Methods. From 20 (40 hemispheres) formaline
fixed human brains (both sexes; 27- 65 years) tissue blocks from SPL and PEC
from the left and right hemisphere were used. According to their size the
brains were divided into two groups, the group I with the larger left (15
brains) and the group II with the larger right hemisphere (5 brains). Serial
Nissl sections (5 ?m) of the left and right SPL and PEC were used for
stereological estimation of NV of the layer V pyramidal neurons. Results. NV
of pyramidal neurons in the layer V in the left SPL of brains with larger
left hemispheres was significantly higher than in the left SPL of brains with
larger right hemisphere. Comparing sides in brains with larger left
hemisphere, the left SPL had higher NV than the right one, and then the left
PEC, and the right SPL had significantly higher NV than the right PEC.
Comparing sides in brains with the larger right hemisphere, the left SPL had
significantly higher NV than left PEC, but the right SPL had significantly
higher NV than left SPL and the right PEC. Conclusion. Generally, there is an
inverse relationship of NV between the medial and lateral areas of the human
posterior parietal cortex. The obtained values were different between the
brains with larger left and right hemispheres, as well as between the SPL and
PEC. In all the comparisons the left SPL had the highest values of NV of
pyramidal neurons in the layer V (4771.80 mm-3), except in brains with the
larger right hemisphere.
Influence of balanced occlusion in complete dentures on the decrease in reduction of an edentulous ridge
Authors: Postic Srdjan
Published: May 2012

Background/Aim. Balanced occlusal arrangement of artificial teeth and
balanced occlusion is a specific type of occlusion that preserves the
stability of complete dentures. Balanced occlusion comprises realization of
tooth contacts at the working side as well as at the balancing side, at the
same time. The aim of this study was to assess the influence of balanced
occlusal arrangement of artificial teeth on the decrease in reduction of
edentulous alveolar ridge. Methods. A longitudinal study on 91 fully
edentulous patients was conducted using their panoramic radiographs and
parameters of vertical dimension of edentulous ridges. All the patients were
clinically examined by the same and a qualified dental practitioner.
Numerical values of parameters of vertical dimensions of edentulous ridges
and lines were statistically processed and compared using the Student?s
t-test. Results. Vertical dimensions and heights of edentulous ridges were
different after comparison of parameters in complete denture wearers with
balanced occlusion and complete denture wearers without bilaterally balanced
occlusion, as well as between male and female edentulous patients.
Statistically significant differences of heights were established in complete
denture wearers? with a set of artificial teeth without balanced occlusion,
at the baseline and 12 months after wearing of complete dentures. Conclusion.
Balanced occlusion is a favored occlusal design in setting of artificial
teeth in conventional complete dentures, which preserves edentulous ridge and
influence the stability of dentures.
What Teachers in Pre-vocational Education Should Teach and What They Actually Teach: A Comparison of Curricula and Teaching in Germany and China
Authors: Pilz Matthias , Li Jun
Published: May 2012

This article compares the pre-vocational education curriculum plans in lower-secondary schools in Germany and Mainland China, and their implementation. Choosing the curricula of certain school types in two selected regions in both countries, this research first carries out a content analysis of the curriculum plans, using the criteria developed from the curriculum development theory of Reetz. In the second step, based on the findings on the theoretical level, some semi-structured in-depth teacher interviews are conducted in both countries with the purpose of finding out the degree of curriculum implementation as well as influencing factors in the actual teaching practice. The investigation reveals that in both countries certain disparities exist between the curriculum plan on the one hand and the teaching reality on the other hand. The reasons for the disparity are largely different in the two countries and are closely related to the varied institutional settings, the financial situation, as well as teacher training, etc.
Asian Students' Citizenship Values and their Relationship to Civic Understanding: An Exploratory Study Comparing Thai and Hong Kong Students
Authors: Kennedy Kerry J.
Published: May 2012

This article draws on data from the International Civic and Citizenship Education Study (ICCS) to compare selected citizenship values of students from Thailand and Hong and the relationship of these values to students' civic knowledge. The results indicated considerable differences in the responses of students from each society and differing impacts on their civic knowledge. The models proposed here seem to be more explanatory of the Thai students' responses than they are of Hong Kong students', so additional explanations need to be found for the latter's achievement. This study, for example, has been able to account for just over 32% of the variance in Thai students' civic knowledge, but for only 14% for Hong Kong students. It represents an important start in seeking a fuller explanation of students' civic learning in different cultural, political and social contexts.
Co-operatives and the Equity-Liabilities Puzzle: Concerns for Accounting Standard-Setters
Authors: López-Espinosa Germán , Maddocks John , Polo-Garrido Fernando
Published: May 2012

SYNOPSIS:

The IASB/FASB joint project on Financial Instruments with Characteristics of Equity (formerly Liabilities and Equity) has highlighted the complexity and the associated difficulty of drawing the line between liabilities and equity. While classification difficulties have been identified for investor-owned businesses (IOB), the inconsistency of the different approaches being considered is clearer when applied to classification of the financial instruments of co-operatives whose ownership characteristics differ from the IOB model. In co-operatives the existence of an upper limit on members' claims on the net assets while the co-operative is a going concern is a key ownership characteristic. We have examined the characteristics of co-operative member shares in six European countries as well as in the U.S. and in Canada, in order to analyze the application of the various classification approaches under discussion by the IASB and FASB. The results of this analysis indicate that classification criteria based on ownership must take account of the fact that ownership is multidimensional and contingent on the type of firm.

JEL Classifications: M41, P13.
On the SU(2)×SU(2) symmetry in the Hubbard model
Authors: Jakubczyk Dorota , Jakubczyk Paweł
Published: May 2012

We discuss the one-dimensional Hubbard model, on finite sites spin chain, in context of the action of the direct product of two unitary groups SU(2)×SU(2). The symmetry revealed by this group is applicable in the procedure of exact diagonalization of the Hubbard Hamiltonian. This result combined with the translational symmetry, given as the basis of wavelets of the appropriate Fourier transforms, provides, besides the energy, additional conserved quantities, which are presented in the case of a half-filled, four sites spin chain. Since we are dealing with four elementary excitations, two quasiparticles called “spinons”, which carry spin, and two other called “holon” and “antyholon”, which carry charge, the usual spin-SU(2) algebra for spinons and the so called pseudospin-SU(2) algebra for holons and antiholons, provide four additional quantum numbers.
On the role of longitudinal momenta in high energy hadron-hadron scattering
Authors: Sharf Igor , Tykhonov Andrii , Sokhrannyi Grygorii , Deliyergiyev Maksym , Podolyan Natalia , Rusov Vitaliy
Published: May 2012

We demonstrate a new method to calculate inelastic scattering cross-sections, which in contrary to the Regge-based methods takes into account the energy momentum conservation law. It is shown that the main contribution to integral expressing inelastic scattering cross-sections does not come from the multi-Regge domain. In particular, accounting for the longitudinal momenta contribution to virtualities is sufficient and results in the new mechanism of cross-section growth. The reasons for taking into account the sufficiently high number of interference contributions are shown and the approximate method for this purpose is developed. By fitting single free parameter of the model achieved a qualitative agreement of the total and inelastic cross sections with experimental data.
Equation of state and initial temperature of quark gluon plasma at RHIC
Authors: Csanád Máté , Májer Imre
Published: May 2012

In gold-gold collisions of the Relativistic Heavy Ion Collider a perfect fluid of strongly interacting quark gluon plasma (sQGP) is created. The time evolution of this fluid can be described by hydrodynamical models. After an expansion, hadrons are created during the freeze-out period. Their distribution reveals information about the final state. To investigate the time evolution one needs to analyze penetrating probes: e.g. direct photon observations. In this paper we analyze a 1+3 dimensional solution of relativistic hydrodynamics. We calculate momentum distribution, azimuthal asymmetry and momentum correlations of direct photons. Based on earlier fits to hadronic spectra, we compare photon calculations to measurements to determine the equations of state and the initial temperature of sQGP. We find that the initial temperature in the center of the fireball is 507±12 MeV, while for the sound speed we get c
s=0.36±0.02. We also estimate a systematic error of these results. We find that the measured azimuthal asymmetry is also compatible with this model. We also predict a photon source that is significantly larger in the out direction than in the side direction.
Rabi type oscillations in damped two-dimensional single electron quantum dots
Authors: Mukhopadhyay Madhuri , Hazra Ram , Ghosh Manas , Mukherjee Samaresh , Bhattacharyya Shankar
Published: May 2012

We present a quantized model of a harmonically confined dot atom with inherent damping in the presence of a transverse magnetic field. The model leads to a non-Hermitian Hamiltonian in coordinate space. We have analytically studied the effects of damping on Rabi type oscillations of the system. The model explains the decoherence of Rabi oscillations in a Josephson Junction.
Single scattering detection in turbid media using single-phase structured illumination filtering
Authors: Berrocal E. , Johnsson J. , Kristensson E. , Aldén M.
Published: May 2012

This work shows a unique possibility of visualizing the exponential intensity decay due to light extinction, when laser radiation propagates through a homogeneous scattering medium. This observation implies that the extracted intensity mostly originates from single scattering events. The filtering of this single light scattering intensity is performed by means of a single-phase structured illumination filtering approach. Results from numerical Monte Carlo simulation confirm the experimental findings for an extinction coefficient of µe = 0.36 mm−1. This article demonstrates an original and reliable way of measuring the extinction coefficient of particulate turbid media based on side-scattering imaging. Such an approach has capabilities to replace the commonly used transmission measurement within the intermediate single-to-multiple scattering regime where the optical depth ranges between 1 < OD < 10. The originality of the presented approach is that only one image is used (instead of three images usually employed in structured illumination) and that no monitoring of the incident intensity is required, simplifying the experimental procedure and set-up. Applications of the technique has potential in probing challenging homogeneous scattering media, such as biomedical tissues, turbid emulsions, etc, in situations where dilution cannot be applied and where conventional transmission measurements fail.
Spectral interferometry-based chromatic dispersion measurement of fibre including the zero-dispersion wavelength
Authors: Hlubina P. , Kadulová M. , Ciprian D.
Published: May 2012

We report on a simple spectral interferometric technique for chromatic dispersion measurement of a short length optical fibre including the zero-dispersion wavelength. The method utilizes a supercontinuum source, a dispersion balanced Mach-Zehnder interferometer and a fibre under test of known length inserted in one of the interferometer arms and the other arm with adjustable path length. The method is based on resolving one spectral interferogram (spectral fringes) by a low-resolution NIR spectrometer. The fringe order versus the precise wavelength position of the interference extreme in the recorded spectral signal is fitted to the approximate function from which the chromatic dispersion is obtained. We verify the applicability of the method by measuring the chromatic dispersion of two polarization modes in a birefringent holey fibre. The measurement results are compared with those obtained by a broad spectral range (500–1600 nm) measurement method, and good agreement is confirmed.