bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigação dos sintomas de depressão e sua associação com ansiedade entre alunos de graduação em odontologia
Authors: Waisman João Pedro Barroso , Mendes Karine Laura Cortellazzi , Possobon Rosana de Fátima 
Published: March 2019

Depressão e ansiedade são cada vez mais frequentes entre alunos de graduação, podendo afetar seu desempenho acadêmico. Pessoas ansiosas podem apresentar mais sintomas de depressão. Objetivou-se investigar a prevalência de sintomas de depressão entre alunos de graduação em Odontologia e verificar a associação com a ansiedade-traço e variáveis socioeconômicas e demográficas entre os alunos. Participaram 261 graduandos em Odontologia (FOP-Unicamp), dos 5 anos de curso, no ano de 2018. Os alunos convidados a participar preencheram o Inventário de depressão de Beck (BDI) e o Idate-T (ansiedade-traço), além do questionário socioeconômico. Realizou-se análise descritiva dos dados. Análises brutas, estimando-se os Odds Ratios e Intervalos de 95% de Confiança,foram realizadas para testar a associação entre depressão e as variáveis independentes. Os testes estatísticos foram realizados pelo Bioestat 5.0. com significância de 5%. A média de idade dos alunos foi de 21,1 anos. Da amostra, 43,2% eram do sexo feminino, idade ≤ 21 anos e 93% moravam longe dos pais. Em relação a depressão, 44,8% tinham ausência ou sintomas depressivos mínimos e 55,2% tinham depressão, sendo que 70,9% de leve a moderada, 25,5% moderada a grave e 3,6% grave. Alunos que apresentaram alta ansiedade-traço tiveram 5,64 vezes mais chance de ter depressão do que aqueles com baixa ansiedade-traço. A prevalência de alunos com sintomas depressivos foi alta e a alta ansiedade-traço foi associada a presença de depressão.
Guerbet Alkoxy Betaine Surfactant for Surfactant-Polymer Flooding in High Temperature, High Salinity Reservoirs
Authors: Cai Hongyan , Wang Qiang , Luo Wenli , Wang Hongzhuang , Zhou Xinyu , Li Jianguo , Zheng Yancheng 
Published: March 2019

Abstract
In recent decade, various betaine surfactants have been developed and extensively investigated for binary Surfactant-Polymer flooding (SP flooding) due to their high interfacial activity at oil-water interface, excellent thermal tolerant and salt/divalent ion resistant characteristics under harsh reservoir conditions. Herein, a new type of guerbet alkoxy betaine surfactant (GAB) was prepared and evaluated for SP flooding. In order to boost the emulsification capability of betaine surfactant, ethylene oxide (EO) functional group was incorporated into betaine molecule and guerbet alcohol was selected as hydrophobic group. Firstly, glycidyl ether was prepared by reaction of alkoxylated Guerbet alcohol and epoxy chloropropane. Then, glycidyl ether and dimethyl amine generated tertiary amine. In the last step, surfactant GAB was synthesized by quarternization reaction of tertiary amine with 3-chloro-2-hydroxyl propanesulfonic acid sodium salt. In-lab performance evaluations, including interfacial tension, long term stability, contact angle, and phase behavior were conducted for this GAB surfactant. The developed surfactant demonstrated very good compatibility with high temperature, high salinity (HTHS) reservoir conditions. Applicability range of GAB surfactant amounted to 275,000 mg/L and 120 °C. Ultralow interfacial tension with crude oil was obtained using diluted GAB solutions with weight concentration ranging from 0.03% to 0.20%. For formulation composed by 0.5% GAB and 0.5% amidobetaine, Winsor III middle phase microemulsion was formed with dehydrated light oil from a high temperature, high salinity carbonate reservoir. The solubilization ratio mounted to 16 at reservoir temperature of 95 °C and optimal salinity of 50,000 mg/L. Compared with guerbet alkoxy sulfate surfactant and conventional sulfobetaine with similar structure, the developed betaine surfactant GAB showed better thermal stability, higher interfacial activity, and intensified emulsification capability under HTHS conditions.
Acid and Scale Inhibitor Squeeze Treatments on Two Subsea Gas Condensate Wells: Design of Subsea Connection, Treatment, Wells Start-Up and Results of the Operation.
Authors: Hatscher Stephan , Kiselnikov Maxim 
Published: March 2019

Abstract
On the Vega gas condensate and oil field in the Norwegian North Sea, two high temperature, high pressure (HTHP) gas condensate wells on one subsea template in 370 m water depth were acid and scale inhibitor treated in order to improve productivity by acid scale removal and prevent future scaling. Significant amount of work was undertaken on design and qualification of the treatment fluids. In order to reduce operation time and increase efficiency, a novel one-time connection concept was utilized. During the operations, wells were kicked off after energizing with gas bullheaded from the neighbouring well. The treatment fluids were designed to reduce consequences for the host facility due to H2S generated during the operation - this required optimization after understanding of the H2S source as witnessed in prior treatments.
The new concept with one-time connection was successfully employed and allowed for three subsequent well treatments in a row, thus saving at least two days vessel operations time. The gas injection from the neighbouring well - the one not treated at the moment - allowed for an efficient start-up of the treated well without need for larger nitrogen injection which would have led to contamination and potentially to flaring due to off-spec gas. The introduction of a batch with pH neutralizer and H2S scavenger batch into the treatment design to be placed into the production pipeline reduced H2S liberation and production to the host facilities, thus limiting the operational stress on the platform. Productivity of well A1 showed an immediately significant increase after the operations, whereas productivity of well A2 required a longer clean-up than originally anticipated.
Development of a Barium Sulphate Scale Inhibitor for Chalk Solid Loaded Conditions
Authors: Temple Erin , Jordan Myles , Williams Helen , Kjelstrup Sigrid , Kilibarda Marija , Johansen Kolbjorn 
Published: March 2019

Abstract
The impact of suspended solids and dynamic conditions on sulphate scale control is well-known. Previous work examined the effect of suspended solids, along with static and turbulent conditions, on one scale inhibitor (Vs-Co). This study has focused on the challenges experienced by an operator of a chalk reservoir field, with a significant amount of carbonate solids in the system, and a high sulphate scale risk due to high barium concentration, injection seawater breakthrough, and cool topside process conditions (20°C). The initial laboratory evaluation showed that the minimum inhibitor concentration (MIC) observed increased from 50ppm to 250ppm after 24 hours (&gt;80% efficiency) under these conditions.
A further study investigated whether a reduction in MIC could be achieved with different chemistry. Various chemicals were screened in conventional static jar tests and in stirred tests to induce turbulence incorporating mixed solids. The results showed that many of the conventional scale inhibitor chemistries, working by nucleation inhibition and crystal growth retardation, could not cope with the severe scaling conditions and were less efficient than the incumbent. However, a "novel" scale inhibitor formulation was shown to work more effectively and resulted in a significantly lower MIC than the incumbent.
Under sulphate scaling conditions (80:20 FW:SW), VS-Co recorded an MIC of 250ppm which was reduced to ≤100ppm with the novel chemical. This resulted in the opportunity for the operator to reduce their chemical dose rate and logistical costs.
This novel chemical works by a combination of nucleation inhibition and crystal growth retardation. As a result of this inhibition mechanism, other operators experiencing similar harsh sulphate scaling conditions could achieve a lower treat rate in high suspended solid loaded systems.
Effect of Scaling and Corrosion Inhibitors on the Static Adsorption of an Anionic Surfactant on a Carbonate Rock
Authors: Gutierrez Mary Ellen , Gaona Silvia Juliana , Calvete Fernando Enrique , Botett Jesus Alberto , Ferrari Jean Vicente 
Published: March 2019

Abstract
About half of the world's oil reserves are in carbonate reservoirs, and most of these formations are mixed-wet or oil-wet and fractured, with extremely heterogeneous porosities and permeabilities. Implementation of enhanced oil recovery (EOR) techniques in this kind of reservoir is essential to achieve peak oil production and increase the recovery factor. Chemical EOR (CEOR) processes have been studied for many years in carbonate reservoirs but are not usually economically viable. Surfactant flooding has been considered as one of the most promising techniques among the chemical recovery methods due to the capacity of some surfactants to alter the carbonate rocks' wettability. However, the process is economically feasible only when losses of surfactant caused by adsorption into the porous media are decreased. Adsorption of surfactants can be affected by the surface charge on the rock surface and fluid interfaces. In general, the adsorption of cationic surfactants on carbonates is lower in comparison with other surfactants. Nevertheless, the high cost of cationic surfactants compared to anionic ones has led to studies aiming to evaluate the injection of the latter in the presence of a sacrificial agent in order to reduce the adsorption caused by interaction between the negative charges of the surfactant and positive charges on the carbonate surface. This work aims to study the effect of the presence of two chemicals, normally applied as scaling and corrosion inhibitors, on reducing the static adsorption of an anionic sodium olefin sulfonate surfactant on a carbonate rock. Water soluble poly(sodium methacrylate) (PSM) and diethanolamine (DEA) were evaluated as sacrificial agents in concentrations close to their scaling and corrosion inhibitor functions, respectively, to verify their sacrificial role in a co-injection chemical scenario. Adsorption studies were carried out using a pulverized carbonate rock in which low-salinity water was used as the base medium. Aqueous stability tests were carried out, which made it possible to select the correct salinity for the solutions of surfactant. Surface tension measurements were used as an indirect approach to study the adsorption of the surfactant in the presence and absence of PSM and DEA. Individually, PSM presented the best performance in reducing the adsorption of the anionic surfactant, while the DEA showed an almost null effect. However, when the chemicals were mixed, a synergistic effect was observed. The performance of PSM can probably be attributed to a steric effect of an adsorbed layer of polymer. It will be shown that even at lower concentrations, co-injection chemicals which are used for targeting other issues, such as scaling and corrosion inhibitors, may play the role of a sacrificial agent in reducing the adsorption of anionic surfactants, which is a concern in application to carbonate reservoirs.
Strategies for Squeezing Co-Mingled Wells in the Same Flow Line in Sub-Sea and Deepwater Environments - Guidelines for Scale Inhibitor Selection and Effective Treatment Strategies and Design
Authors: Heath Stephen , Gjøsund Nina , Dugué Dominique 
Published: March 2019

Abstract
As the oil and gas industry continues to operate in more complex and deeper water environments downhole scale control via scale squeeze treatments becomes an ever-increasing technical challenge. It is therefore essential that effective scale management strategies are adopted which incorporate suitable scale inhibitor (SI) selection, analysis and treatment design procedures to provide optimal and cost-effective squeeze treatment lifetimes to maximise oil production and reduce well intervention costs.
In this paper key factors are evaluated in order to provide a guidance to selecting a suitable treatment strategy for downhole scale control in co-mingled sub-sea well and the impact of chemical retention, minimum inhibitor concentration (MIC), limit of quantifiable detection (LOQD) and well dilution factors on treatment design and strategy are discussed. The pros and cons of different treatment strategies are presented in this paper and consideration is given to following three treatment strategies: Treating all wells with the same chemical and over designing the chemical treatment lifetime ie 18 months and then re-treating all wells after 12 months;Treating individual wells with tagged versions of the same scale inhibitor chemical;Treating individual wells with different scale inhibitors.
Options (ii) and (iii) offer the ability to design similar treatment lifetimes for each well but have the flexibility to monitor wells individually and re-squeeze when required.
Examples are provided for treatment options (ii) and (iii) based upon a field example to illustrate the design concepts for fluorescent (F) and phosphorus (P) tagged polymers in two co-mingled wells and a theoretical example for treating three co-mingled wells with different scale inhibitors, one of which could be a phosphonate with two tagged polymers.
This paper presents an overview of the key factors that influence chemical selection and treatment design for co-mingled wells in the same flow line. In addition, it will highlight important concepts to provide guidance for the design of effective treatment strategies for squeezing co-mingled wells in sub-sea and deepwater environments.
Effect of Calcium Carbonate on Barite Solubility Using a Chelating Agent and Converter
Authors: Abdelgawad Khaled , Mahmoud Mohamed , Elkatatny Salaheldin , Patil Shirish 
Published: March 2019

Abstract
Barium Sulfate (Barite) is one of the common oil and gas field scales formed inside the production equipment and in the reservoir. Barite is also a common weighting material used during drilling oil and gas wells. Barium sulfate scale may exist as well in carbonate formations. The removal of barium sulfate from calcium carbonate formation is a challenging problem because of the solubility of calcium carbonate is higher compared to that of barium sulfate in different acids. In addition, barium sulfate is not soluble in the regular acids such as hydrochloric (HCl) acid and other organic acids.
In this paper, the effect of calcium carbonate on barium sulfate solubility in a chelating agent and converter catalyst was investigated using solubility experiments at 80°C as a function of time. 20 wt.% DTPA with 6 wt.% potassium carbonate (converter) were used at pH of 12. The effect of calcium chelation on the barium sulfate solubility was studied in two scenarios. The first scenario when Barium sulfate is dissolved first then the solution reacts with calcium carbonate. The second scenario when both calcium carbonate and barium sulfate are exposed to the DTPA solution at the same time. In addition, the effect of calcium carbonate loading on the barium sulfate solubility was determined using 25, 50, 75, and 100 wt.% of the scale as calcium carbonate. As an evaluation criterion, inductively coupled plasma (ICP) was used to analyze the cation concentration and determine the solubility of each scale type.
For the two scenarios of barium sulfate dissolution, the presence of calcium carbonate had a significant effect on the solubility of barium sulfate. When DTPA solution got saturated first with barium cations after 24 hours, and the addition of calcium carbonate to the solution will cause immediate barium drop of solution (concentration drop from 2140 to 1984 ppm in 30 min in 50 ml solution) which cause precipitation of barium sulfate. In addition, simultaneous chelation of both calcium carbonate and barium sulfate showed a low barium sulfate solubility compared to calcium carbonate. This can be explained by the high affinity of DTPA to calcium compared to barium.
It is highly recommended to account for the presence of any calcium source during the design of the chemical formulation for barium sulfate scale removal using DTPA. Therefore, DTPA treatment formulation is recommended in sandstone formations. Field results can be completely different from laboratory results if Ca2+ chelation from carbonate rocks is ignored.
Water Chemistry Application in Reservoir Management and Production
Authors: Wei Wei , Wang Wei , Clinch Simon 
Published: March 2019

Abstract
This paper presents novel approaches and comprehensive field case examples on applying water chemistry in reservoir management and production. Systematic field water sampling and analysis, data integration, and water chemistry fingerprinting techniques are utilized for various important applications such as Original Oil In Place (OOIP) estimate, water source identification, prediction/prevention/management of oilfield scale and other water-related production/operation problems. Field case study examples show significant value creation achieved by utilizing water chemistry-based approaches. Results show subsurface water heterogeneity can significantly impact the calculation of OOIP, water sampling and analysis is critical to identify "unexpected" scaling risk at initial water breakthrough and monitor seawater breakthrough ensuring management/treatment in place as needed, systematic water data collection and integration and understanding can be used as a reliable/efficient/cost-effective approach to identify water source/water breakthrough from a new formation zone. Significant value creation was achieved for projects via our novel and systematic water chemistry-based approach discussed in this paper.
A Novel Biochemical-Based Paraffin Wax Removal Program Providing Revenue Generation and Asset Enhancement
Authors: Raney Kirk , Alibek Ken , Shumway Martin , Karathur Karthik , Stanislav Terry , West Gary , Jacobs Marc 
Published: March 2019

Abstract
New biochemically-derived products for the removal of paraffin wax from oil wells do not require additional capex nor heat and do not utilize bacteria. They contain inactivated microbial cells, biosurfactants and biosolvents, and other components harvested as microbial byproducts that emulsify and dissolve paraffin from rock pores and from the well surfaces over wide temperature, salinity, depth, and pH ranges. Additionally, they increase oil recovery by remediating near-wellbore formation damage, reducing interfacial tension, altering rock surfaces and changing their wettability, and reducing oil viscosity. The product application is environmentally superior to well treatments using hot oil/water and aromatic solvents and is economical due to low capital and operating costs required for product synthesis. Specifically, product preparation is achieved using a modular fermentation system that is installed near the points of application. This insures highly efficient and low-cost production and logistics, as well as reducing time from generation to application which maximizes potency. With sufficient space, water, and electricity, the initial manufacture of the dispersal products can occur within a few weeks.
The treatment products utilized were initially developed and tested in laboratory studies, which showed that dispersion rates of the relevant paraffin samples were comparable to those achieved with toluene. The paraffin dispersal products exhibit a very high level of efficacy and safety when deployed in the Appalachian and Permian Basins. The potency of these products has led to outstanding paraffin removal results as indicated by reduced well failures in both vertical and horizontal wells and by visual observation of sucker rods removed from the wells. In addition, tank sludge and wax deposits in pipelines can be removed through either residual product flowing from the well or through direct application. Growth of detrimental bacteria and formation of biofilms are inhibited by the product application thereby reducing corrosion risk.
Specifically, details of an almost two-year 70-well study in the Appalachian Basin are reported in which no well failures were observed due to paraffin buildup and 95% of the wells exhibited an enhanced oil recovery effect during the paraffin remediation treatments. This resulted in an approximate 50% average increase in sustained production rate over baseline. Analysis of the results forecasts a substantial increase in future production, thereby significantly enhancing the value of the producing wells. Importantly, longer times between required treatments and the increased recovery rates have transformed the paraffin maintenance program into a documented revenue generator for the operator.
A New Approach to Testing Scale Inhibitors in Mild Scaling Brines – Are Dynamic Scale Loop Tests Needed?
Authors: Barber Miriam , Heath Stephen 
Published: March 2019

Abstract
Static jar tests are widely known and used in the oil and gas industry for quantitative screening and determining the minimum effective dose (MED) for scale inhibitors. However, when dealing with very low saturated brines, challenges are faced in the laboratory to replicate the same scaling environment found in the oilfield facilities and often brines have to be stressed in order to induce scaling in the laboratory tests. This paper proposes an efficient approach for quick chemical selection and recommendation for low scaling environments.
The method proposed has been developed and successfully applied for the selection and recommendation of scale inhibitors in low to mild saturated brines. This technique involves the combination of the standard static jar test with Scanning Electron Microscopy (SEM) and UV-Visible Spectrophotometry (UV/VIS).
The two case studies presented here shows two fields with low to mild barium sulphate (BaSO4) and calcium carbonate (CaCO3) scaling issues. This novel approach of has been used to screen and identify the best scale inhibitor in terms of cost effective peformance. Post-experimental analyses such as the Scanning Electron Microscope/Energy Dispersive X-Ray Diffraction Spectrometry (SEM/EDXS) permitted the investigation and assessment of the type of scale formed, and the mechanisms of inhibiton for each scale inhibitor chemistry tested.
This combined approach removed any discrepancies obtained by visual observations and/or Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) efficiency measurements. Furthermore, the UV-Visible Spectrophotometry was used in conjunction to the static SEM/EDXS method, in order to reassess the MED for the scale inhibitor candidates using the kinetic turbidity test (KTT) method. Results obtained from the KTT method complimented those from the combined static with ICP and SEM imaging, providing a quick understanding of the scale formation kinetics and inhibition efficiency.
To summarise, results have shown that different techniques can be used as a fast screening process for the MED using different scale inhibitors at low scaling regimes. Therefore, the static SEM and KTT methods are recommended as a thorough screening process for determining the optimum MED and selection of the best fit for purpose scale inhibitor. This opposes the conventional dynamic scale loop (DSL) approach, which would require severe alterations to the brine chemistry in order to get a scaling blank within a minimum 2-hour-period.