bluuebunny/crossref_metadata_2025 huggingface dataset:
Boletín informativo
Authors: Socidrogalcohol Socidrogalcohol
Published: March 2016

Boletín
Can we predict psychostimulant use in youths? A study with structural equation modeling analysis
Authors: Becoña Elisardo , López-Durán Ana , Fernández del Río Elena , Martínez Úrsula , Fraga Jaime , Osorio Jesús , Arrojo Manuel , López-Crecente Fernanda , Nieves Domínguez María
Published: March 2016

Knowing which factors predict the use of psychostimulant drugs among youths is important for designing preventive programs and the identifi-cation of youths with the highest probability of use, to avoid some of the problems that can be derived from it. The purpose of this study is to examine the relationship between perceived availability, risk perception, personality traits, antisocial personality patterns, and use of other substances in the prediction of psychostimulant use. The sample was composed by 1,177 youths (584 males and 593 females) aged 14 to 25 in Spain, recruited randomly, stratified by lifetime use- non use of psychostimulants (cocaine or ecstasy). The path which best predictspsychostimulant use is: Personality traits-legal substance use-cannabisuse-psychostimulant use. The next path is: Personality traits-antisocialpersonality patterns-psychostimulant use. Risk perception and perceivedavailability were significant in the prediction, but made a smaller contribution. The results of this study suggest that the model evaluatedcan predict psychostimulant use in youths. This model can be seen as auseful tool for developing preventive strategies and for identifying thoseyouths that are at risk for problems related to drug use.
Consumo de drogas y prácticas sexuales de los adolescentes de la ciudad de Medellin (Colombia)
Authors: Castaño Pérez Guillermo A. , Arango Tobon Eduardo , Morales Mesa Santiago , Rodríguez Bustamante Alexander , Montoya Montoya Carolina
Published: March 2016

Se estudia la relación entre consumo de drogas y prácticas sexuales en adolecentes de la ciudad de Medellín (Colombia). Mediante muestreo pro- babilístico aleatorio y por conglomerados, se obtuvo una muestra represen-tativa de 955 adolescentes entre los 14 y 17 años de edad pertenecientes a colegios públicos y privados de la ciudad de Medellín de los grados 9º, 10º y 11º. Los resultados muestran que la prevalencia general derelaciones sexuales bajo el efecto de alcohol o drogas es del 43,67%. Las drogas más usadas para tener prácticas sexuales son el alcohol, la marihuana, el popper, la cocaína y el éxtasis. Consumir alcohol o drogas y tener prácticas sexuales presenta una asociación estadística significativa (p= .001). Las practicas sexuales mas frecuentes bajo el efecto de sustancias psicoactivas son las exploratorias (manoseo, caricias) 71%; la penetrativa vaginal (63.67%), el sexo oral (45.30%) y la masturbación (19.59%). Con respecto a tener prácticas sexuales bajo efecto de alcohol o drogas y usar métodos de protección, el 55,9% de los jóvenes usan siempre el condón, el 37,3% lo usan algunas veces y el 6,8% nunca lo usan. Este estudio prueba lo ya constatado por otras investigaciones donde se muestra la alta asociación estadística que hay entre el consumo de drogas y las prácticas sexuales, pero da cuenta que no existe asociación estadística significativa entre tener practicas sexuales bajo efectos de alcohol o drogas y el uso o no uso de métodos de protección, lo que constituye su hallazgo mas importante.
Efectividad a largo plazo de los tratamientos de mantenimiento con metadona en personas con adicción a derivados opiáceos
Authors: Bobes García Julio , Bobes Bascarán María Teresa
Published: March 2016

Los estudios prospectivos de grandes series con distintas dosis de mante- nimiento y marcadores distales estandarizados no existen, sin embargoactualmente existe evidencia acerca de la efectividad de la metadona como tratamiento a largo plazo de la adicción a opiáceos. Entre sus resultados se puede destacar un menor consumo de sustancias ilegales, menor impli- cación en actividades criminales y mejor funcionamiento social general. Por otra parte, la salud física y mental permanece más conservada y recu- perada. Puesto que los pacientes en tratamiento con metadona presentan menos probabilidad de padecer problemas cardiovasculares, VIH, hepatitis C, hepatitis B y otros procesos infecciosos, así como una menor comor- bilidad psiquiátrica. Este editorial pretende definir y guiar el posiciona- miento terapéutico a la hora de abordar el manejo de personas con abuso o dependencia a opiáceos. Para fundamentar las pautas guía se han tenido en cuenta y revisado los principales estudios a largo plazo, análisis sistemáticos y aproximaciones meta-analíticas de la efectividad de la metadona. Por todo ello se recomiendan, con el máximo nivel de evidencia, los tratamientos de mantenimiento con metadona a pesar de las debilidades en cuanto a toxicidad y riesgo cardiovascular, y las dificul- tades de sedación y disminución del funcionamiento cognoscitivo, siempre teniendo en cuenta la historia clínica, el estado de salud general, y los deseos y preferencias del paciente.
Human enhancement drugs and the pursuit of perfection
Authors: McVeigh Jim , Evans-Brown Michael
Published: March 2016

The emerging threat to public health posed by the use of human enhancement drugs has remained largely unrecognised. In attempts tobecome stronger, happier or smarter, or to look thinner, younger or morebeautiful, people are turning to a diverse range of pharmaceuticals. Thewidespread availability of drugs with the potential to improve human attributes, appearance and abilities has generated a new and growingaudience of users. Unlike users of drugs such as heroin, cocaine etc, users of human enhancement drugs do not necessarily perceive themselves as ‘drug users’. Those attracted to these drugs may have little or no knowledge or understanding of the physical or psychological harm associated with these substances or their potential for addiction. In addition to the potent effects of many human enhancement drugs, there are considerable risks associated to the clandestine nature of the market. The growing number of untested, banned or adulterated drugs and the lack of safeguards and quality assurance in the illicit manufacturing process has resulted in serious harms and fatalities. The ease with which pharmaceuticals can be manufactured and distributed, combined with the significant profits that can be made from the illicit market, has resulted in a growing challenge for policy makers and health systems in many countries. This editorial aims to raise awareness of this emerging drugs situation and provide a brief overview of some of the drugs and their associated risks.
Eficiencia de dos intervenciones motivacionales para la deshabituación tabáquica en adolescentes (breve e intensiva) realizadas en Institutos de Educación Secundaria
Authors: Pérez-Milena Alejandro , Navarrete Guillén Ana Belén , Mesa-Gallardo María Inmaculada , Martínez Pérez Rocío , Leal-Helmling Francisco Javier , Pérez-Fuentes Carlos
Published: March 2016

Se desea determinar la eficiencia de dos intervenciones motivacionales en adolescentes, basadas en el uso de disonancias cognitivas, para conseguir el cese del tabaquismo. Se realiza un estudio experimental aleatorizado multicéntrico en 5 Institutos de Educación Secundaria. Se proponen inter-venciones individuales en los institutos participando adolescentes fuma- dores (≤20 años) que desean dejar de fumar, con exclusión de embara- zadas, trastornos graves de salud mental o uso de drogas antitabaco. Se recogió el consentimiento informado y un cuestionario previo (variables demográficas, consumo de tabaco/alcohol/drogas, apoyo familiar/social). Se desarrollan dos intervenciones por médicos de familia en el propio instituto mediante un muestreo aleatorio estratificado: intensiva (cuatro sesiones de 15 minutos, reducción progresiva del consumo) y breve (sesión única de 15 minutos, cese inmediato del consumo). Se confirmala abstinencia mediante cooximetría el primer, sexto y duodécimo mes tras la intervención, con análisis por intención de tratar. Participan 92 adolescentes, con edad media 15,4±1,0 años, sin diferencias al principiode las intervenciones: 82% fuman a diario, con baja dependencia (62%) y motivación alta/moderada para el cese (88%), 78% consumen alcohol y 21% drogas. La función familiar y el apoyo social son normales en la mayoría. 47% recibe la intervención intensiva. Se consigue la abstinenciadel 64%±5,0 el primer mes (20% mejor en intervención intensiva, p<0,05 χ2); 42%±5,2 el sexto mes y 27%±4,6 al año (sin diferencias). La inter-vención breve parece ser más eficiente, mientras que serían precisas más investigaciones para determinar el perfil del adolescente que se beneficiaría de una intervención intensiva.
Subtypes of adolescents with substance use disorders and psychiatric comorbidity using cluster and discriminant analysis of MMPI-A profiles
Authors: Magallón-Neri Ernesto , Díaz Rosa , Forns María , Goti Javier , Canalda Gloria , Castro-Fornieles Josefina
Published: March 2016

The main aim of this study was to replicate and extend previous results on subtypes of adolescents with substance use disorders (SUD), according to their Minnesota Multiphasic Personality Inventory for adolescents (MMPI-A) profiles. Sixty patients with SUD and psychiatric comorbidity (41.7% male, mean age = 15.9 years old) completed the MMPI-A, the Teen Addiction Severity Index (T-ASI), the Child Behaviour Checklist (CBCL), and were interviewed in order to determine DSMIV diagnoses and level of substance use. Mean MMPI-A personality profile showed moderate peaks in Psychopathic Deviate, Depression and Hysteria scales. Hierarchical cluster analysis revealed four profiles (acting-out, 35% of the sample; disorganized-conflictive, 15%; normative-impulsive, 15%; and deceptive-concealed, 35%). External correlates were found between cluster 1, CBCL externalizing symptoms at a clinical level and conduct disorders, and between cluster 2 and mixed CBCL internalized/externalized symptoms at a clinical level. Discriminant analysis showed that Depression, Psychopathic Deviate and Psychasthenia MMPI-A scales correctly classified 90% of thepatients into the clusters obtained.
Estudio epidemiológico de las intoxicaciones agudas atendidas en un hospital gallego entre 2005 y 2008
Authors: De Miguel-Bouzas José Carlos , Castro-Tubío Eva , Bermejo-Barrera Ana María , Fernández-Gómez Purificación , Estévez-Núñez Juan Carlos , Tabernero-Duque María Jesús
Published: March 2016

Se realizó un estudio descriptivo retrospectivo de las intoxicaciones agudas registradas en el Complexo Hospitalario de Pontevedra (CHOP) entre enero de 2005 y diciembre de 2008, para conocer el número y tipo de intoxica-ciones atendidas, su distribución según el sexo y edad del paciente, cronología, tipo de agentes tóxicos implicados, intencionalidad, anteceden- tes, clínica, evolución, tratamiento y análisis toxicológico empleado en el diagnóstico. Mediante los programas informáticos Clínica e IANUS y la consulta de todas las historias clínicas en papel de los pacientes atendidos con síntomas de intoxicación, se registraron los datos necesarios. Se incluyeron un total de 1893 pacientes con una edad media de 35,6 ± 17,6 años (66% hombres). La mayor incidencia se alcanzó los sábados y domingos durante los meses de verano (junio, julio y agosto). Los agentes tóxicos más frecuentes fueron las drogas de abuso (70,4%), destacando entre ellas el alcohol etílico (61%), frecuentemente asociado al sexo masculino y a un elevado grado de dependencia. En segundo lugar se situaron las intoxicaciones medicamentosas, frecuentemente asociadas al sexo femenino y producidas, en un 73,2% de los casos, por benzodiacepinas. La mayoría de las intoxicaciones registradas fueron voluntarias y en el 18,8% hubo intencionalidad suicida. Ésta se asoció mayoritariamente al sexo femenino. Las manifestaciones neurológicas fueron las más frecuentes y la mortalidad tan solo fue del 0,2%.
Group Acceptance Sampling Plans for Lifetimes Following an Exponentiated Fréchet Distribution
Authors: Rao G. Srinivasa , Rosaiah K. , Babu M. Sridhar
Published: March 2016

In this article, a group acceptance sampling plan is developed for exponentiated Fréchet distribution based on truncated lifetime with a known shape parameters. A group acceptance sampling plan for a truncated life test is proposed when a multiple number of items as a group can be tested simultaneously in a tester. The design parameters such as the number of groups and the acceptance number are determined using the two-point approach by satisfying the producer’s and the consumer’s risks at the specified quality levels, while the termination time and the number of testers are specified. The results are explained with tables and examples.
Buddhist literary tradition in Buryatia: geoinformation approaches to reconstruct a cultural phenomenon
Authors: Bazarov A. A. , Rinchinov O. S.
Published: March 2016

The article discusses problems of research and representation of the Buddhist literary tradition in Buryatia. It shows main factors of forming the tradition, gives characteristics of its current state and transformation under modern conditions. The approaches to a database generation and archaeographic investigations results presentation are discribed. The methodology of authority data control and GIS technology to create online information resource are represented.
The experience of classifying objects entering the e-book system
Authors: Diner E. V.
Published: March 2016

The article highlights problems characterizing the state of modern book communication, gives the definition of «electronic book» based on which objects classification in the e-book structure is carried out, taking into account the content of state standards and scientific research in the document theory.
A documentary-information approach in the context of post-non-classical methodology of knowledge in bibliographic and library sciences
Authors: Pleshkevich E. A.
Published: March 2016

The basis of a documentary-information approach in the post-non-classical library and bibliographic sciences is the documentary information theory, as well as presentation of library and bibliographic institutions and services as a united complex self-developing system. The article emphasizes studying the institutional information-documentary process, in the structure of which syntactic, semantic and pragmatic components are singled out. It underlines that library-bibliographical institutions implement a semantic component aimed maintaining the semantic symmetry, and a pragmatic one connected with information updating due to bibliographic activity, all these permits to consider library-bibliographical documents and information as a resource. It is noted, that this approach makes it possible, firstly, to consider complementary informational-documentation aspects of library-bibliographic activities (to refuse the documentary and information paradigms opposition), and secondly, to justify the status of library-bibliographic institutions as organizers rather than the documentary-information process intermediaries. The approach methodological potential is analyzed and shown.
Forming representations on the family reading tradition in bibliologic and library science research
Authors: Stepicheva T. V.
Published: March 2016

The article considers the family reading tradition and its formation in library science; a special attention is paid to approaches of its understanding and interpretation.
Polish books of Sabina Jaroszewska personal collection in A. S. Pushkin Tomsk Regional Universal Scientific Library stocks (its formation history, overview and studying prospects)
Authors: Nikienko I. V.
Published: March 2016

The article deals with book collecting as a way to preserve ethnic and cultural identity. The author examines Sabina Jaroszewska personality as the Polish library creator, her book assemblage history and composition, prospects for detailed studying the Polish collection fragment in A.S. Pushkin Tomsk Regional Universal Scientific Library (TRUSL) stocks are outlined. For the first time catalogues and inventories of the TRUSL Foreign book department are used as well as interviews with Academician Rostislav Karpov, who personally knew the collector.
Epidemiological surveillance of enteric viruses in sewage samples in East Macedonia and Thrace region in Greece
Authors: Parasidis Theodoros A , Alexandropoulou Ioanna G. , Konstantinidis Theocharis G. , Panopoulou Maria , Constantinidis Theodoros C.
Published: March 2016

The enteric viruses (EVs) are the most common and widespread human viruses, as they can spread in the environment through the faecal excretion. These infectious agents may cause outbreaks throughout the year. The aim of this study was to investigate the environmental presence of EVs using molecular methods. A total of 144 wastewater samples were collected between December 2004 and November 2006 from six sewage treatment plants in Greece. The sampling was carried out once a month. Out of the 144 examined wastewater samples, 59.7%, 40.9%, 17.3%, 34%, 2% were positive to the detection of adenovirus, enterovirus, norovirus GI, norovirus GII and hepatitis A, respectively. Our results indicated the potential public health risk associated with transmission of human enteric viruses through environmental wastewater routes. This is the first time that enteric viruses have been isolated in the region of East Macedonia and Thrace in Greece.
Preliminary Study on the Prevalence of West Nile Virus Antibody among Horses, Donkeys and Camels in Borno State, Nigeria
Authors: Baba Saka Saheed , NNnadi Obinna Damian , Hamman Kenas Dunama , Saidu Awal , Yuguda Abduldahiru El , Oderinde Bamidele Soji
Published: March 2016

In spite of several serological evidences for the presence of West Nile (WN) virus in Nigeria, the host range of the virus is not fully understood. In this study, the prevalence of the WN virus antibody was determined among horse, donkey and camel populations in Borno state, Nigeria. Two hundred and fifty serum samples comprising of 96 sera from each of horses and camels and 58 from donkeys were tested for presence of WN virus neutralizing antibody. An overall prevalence of WN virus neutralizing antibody of 13.2% was noted in the population of animals tested.  Significant difference (P≤0.05) in prevalence was observed between the animals tested. Highest prevalence (17.7%) was noted in camels followed by horses (11.5%) and donkeys (8.6%). The results of this study confirmed the prevalence of WV virus antibody in camels in Nigeria and represented the first serosurvey for WN virus activities among horses and donkeys in this part of the country. There is considerable activity of the virus in the study area and provided evidence for the potential roles this group of animals could play in the epidemiology of WN virus infection in Nigeria.
In silico structural analysis of Hantaan virus glycoprotein G2 and conserved epitope prediction for vaccine development
Authors: Rahman Monzilur , Parvege Md. Masud
Published: March 2016

Hantaan virus (HNTV) is an etiological agent of potentially fatal hemorrhagic fever with renal syndrome (HFRS). The virus infects a large number of patients annually with a mortality rate more than 10%. However, no treatment option or vaccine is available against the virus. Between two envelope proteins, HNTV glycoprotein G2 has higher antigenicity making it a better target for vaccine development. However, 3-D structure of the protein is not available which is important for identifying epitopes that are essential for vaccine design. Therefore, this study was designed to predict a structural model of glycoprotein G2 and to predict peptide sequences for vaccine development containing conserved epitopes within the structure. Many of the physio-chemical and structural properties including secondary structure and di-sulfide linkage of the protein were predicted using a number of computational tools. The 3D structure of the protein was modeled using I-TASSER online tool. The quality of the predicted models was evaluated with Ramachandran plot and Z-score. The structural and sequence information was used to predict B-cell and T-cell epitopes on glycoprotein G2.  Using various bio-informatics and immuno-informatics tools, a total of 9 continuous B-cell and 22 T-cell epitopes were predicted having significant antigenicity. These antigenic epitopes were further analyzed for conservation and a total of 4 B-cells and 8 T-cell epitopes were found to be highly conserved in sequences from diverse origins. These epitopes revealed by the current study are recognized by immune system to protect host from HNTV infection can be potential targets for vaccine development.
Novel Capillarity Quantification Method in IOR Process in Bakken Shale Oil Reservoirs
Authors: Pu Hui , Li Yinghui
Published: March 2016

Preliminary studies have been done to characterize rock-fluid properties, and flow mechanisms in the shale reservoirs. Most of these studies, through modifying methods used for conventional reservoirs, fail to capture dynamic features of shale rock and fluids in confined nano-pore space. In unconventional reservoirs, interactions between the wall of shale and the contained fluid significantly affect phase and flow behaviors. The inability to model capillarity with the consideration of pore size distribution characteristics using commercial software may lead to an inaccurate oil production performance in Bakken. This paper presents a novel formulation that consistently evaluates capillary force and adsorption using pore size distribution (PSD) directly from core measurements. The new findings could better address differences in flow mechanisms in unconventional reservoirs, and thus lead to an optimized IOR practice.
Application of PC-SAFT Equation of State for CO2 Minimum Miscibility Pressure Prediction in Nanopores
Authors: Wang Shuhua , Ma Mingxu , Chen Shengnan
Published: March 2016

CO2 miscible injection is generally one of the most efficient enhanced oil recovery (EOR) methods and widely used in the conventional oil reservoirs. The applicability of CO2 EOR technology for unlocking the resources from unconventional tight and shale formations and the mechanisms of miscible flooding in these reservoirs still remain unclear. An important parameter used to evaluate the feasibility of CO2 miscible flooding is the minimum miscibility pressure (MMP). Even though experimental approaches, empirical correlations and theoretical methods have performed well in measuring or predicting MMP between CO2 and crude oil in conventional reservoirs, they may not be suitable for unconventional formations as phase behavior and MMP can be significantly affected by confinement effect in small pores (e.g., nanopores) in such formations.

In this study, a new MMP prediction model based on the modified Parachor Model associated with the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) is developed to determine CO2 MMP both in the bulk phase and nanopores. The Parachor Model is modified to account for the confinement effect of nanopore walls on the equilibrium interfacial tension (IFT). The Equilibrium IFT reduction in nanopores is related to a temperature-dependent and slit pore width-dependent modification term. The parameters of the new Parachor Model are determined by matching the vapor-liquid surface tension values for CH4, C2H6, C3H8, n-C4H10, and n-C8H18 in nanopores, respectively. The prediction ability of the new model is verified by comparing the predicted MMP in the bulk phase with the results of other theoretical approaches and slim-tube experimental data. Finally, the new model is applied to estimate the MMP between Bakken oil and CO2 stream. The effect of temperature, slit pore width, and impure components in the injected CO2 on the MMP are also studied.

The newly developed model successfully reproduces MMP in bulk phase as compared with both other methods and experimental data. The overall average absolute relative deviation (AARD) for MMP is within 8 %. The calculated equilibrium IFT for liquid-vapor phase has a good agreement with molecular simulation results. For Bakken oil-CO2 system, if the slit pore width is larger than 10 nm, MMP is independent on pore width; otherwise, it decreases significantly with the decrease of the pore width. If pore width decreases to 3 nm, 67.5 % decrease in the IFT is observed and 23.5% reduction is achieved for MMP between Bakken oil and CO2 stream, indicating that it is easier to reach miscibility in nanopores, and CO2 miscible flooding might be a promising enhanced oil recovery (EOR) technology for tight oil and shale oil reservoirs. Furthermore, MMP increases with an increase of temperature in bulk phase, whereas IFT and MMP decrease with an increase of temperature in nanopores.
How Much Polymer Should Be Injected During a Polymer Flood?
Authors: Seright R. S.
Published: March 2016

This paper addresses two questions for polymer flooding. First, what polymer solution viscosity should be injected? A base-case reservoir-engineering method is present for making that decision, which focuses on waterflood mobility ratios and the permeability contrast in the reservoir. However, some current field applications use injected polymer viscosities that deviate substantially from this methodology. At one end of the range, Canadian projects inject only 30-cp polymer solutions to displace 1000-3000-cp oil. Logic given to support this choice include (1) the mobility ratio in an unfavorable displacement is not as bad as indicated by the endpoint mobility ratio, (2) economics limit use of higher polymer concentrations, (3) some improvement in mobility ratio is better than a straight waterflood, (4) a belief that the polymer will provide a substantial residual resistance factor (permeability reduction), and (5) injectivity limits the allowable viscosity of the injected fluid. At the other end of the range, a project in Daqing, China, injected 150-300-cp polymer solutions to displace 10-cp oil. The primary reason given for this choice was a belief that high molecular weight viscoelastic HPAM polymers can reduce the residual oil saturation below that expected for a waterflood or for less viscous polymer floods. This paper will examine the validity of each of these beliefs.

The second question is: when should polymer injection be stopped or reduced? For existing polymer floods, this question is particularly relevant in the current low oil-price environment. Should these projects be switched to water injection immediately? Should the polymer concentration be reduced or graded? Should the polymer concentration stay the same but reduce the injection rate? These questions are discussed.
Laboratory Study on Using Produced Water in High pH Borate Gels Used in Hydraulic Fracturing
Authors: Elsarawy Ahmed M. , Nasr-El-Din Hisham A. , Cawiezel Kay E.
Published: March 2016

Fracturing fluids are commonly formulated with fresh water to ensure reliable rheology. However, fresh water is becoming more costly, and in some areas, it is difficult to obtain. Therefore, using produced water in hydraulic fracturing has received increased attention in the last few years. A major challenge, however, is its high total dissolved solids (TDS) content, which could cause formation damage and negatively affect fracturing fluid rheology. The objective of this study is to investigate the feasibility of using produced water to formulate crosslinked-gel-based fracturing fluid. This paper focuses on the compatibility of water with the fracturing fluid system and the effect of salts on the fluid rheology.

Produced water samples were analyzed to determine different ion concentrations. Solutions of synthetic water with different amounts of salts were prepared. The fracturing fluid system consisted of natural guar polymer, borate-based crosslinker, biocide, surfactant, clay controller, scale inhibitor, and pH buffer. Compatibility tests of the fluid system were conducted at different cation concentrations. Apparent viscosity of the fracturing fluid was measured using a high-pressure high-temperature rotational rheometer. All rheology tests were conducted at a temperature of 180°F and were conducted according to API 13m procedure with a three-hour test duration. Fluid breaking test was also performed to ensure high fracture and proppant pack conductivity.

Produced water analysis showed a TDS content of 125,000 ppm, including Na, Ca, K, and Mg ion concentrations of 36,000, 10,500, 1,700, and 700 ppm, respectively. Results indicated the potential of produced water to cause formation damage. Therefore, produced water was diluted with fresh water and directly used to formulate the fracturing fluid. Divalent cations were found to be the main source of precipitation, and the reduced amounts of each ion were determined to prevent precipitation. The separate and combined effects of Na, K, Ca, and Mg ions on the viscosity of the fracturing fluid were also studied. Fluid viscosity was found to be significantly affected by the concentrations of divalent cations regardless of the concentrations of monovalent cations. Monovalent cations reduced the viscosity of fracturing fluid only in the absence of divalent cations, and showed no effect in the presence of Ca and Mg ions. Water with reduced concentrations of monovalent and divalent cations showed the most suitable environment for polymer hydration and crosslinking.

This paper contributes to the understanding of the main factors that enable the use of produced water for hydraulic fracturing operations. Maximizing the use of produced water could reduce its disposal costs, mitigate environmental impacts, and solve fresh water acquisition challenges.
Low Tension Gas Flooding as a Novel EOR Method: An Experimental and Theoretical Investigation
Authors: Jong Stephen , Nguyen Nhut M. , Eberle Calvin M. , Nghiem Long X. , Nguyen Quoc P.
Published: March 2016

Low Tension Gas (LTG) flooding is a novel EOR process which can address challenging reservoir conditions such as high salinity, high temperature, and tight rock. Current process understanding is limited, and a joint experimental and modeling approach allows for both interpretation and insight into the complex interactions between the key process parameters of salinity gradient, foam strength, microemulsion phase behavior, and phase desaturation in order to achieve a physically correct and predictive process model.

We performed a series of corefloods in high permeability Berea sandstones (~500 mD) to demonstrate the impact of salinity gradient on the LTG process and interactions between key mechanisms such as microemulsion phase behavior and foam stability. In order to provide additional insight into the experimental study and improve understanding of the LTG process, we used our newly developed LTG simulator which we built within CMG GEM.

The results demonstrate that decreasing slug injection salinity can lead to a 15% increase in residual oil in place (ROIP) recovery over a slug injected at optimum salinity, with earlier breakthrough and steeper recovery slope. In addition, there is evidence of a late time pressure buildup as salinity is decreased through mixing with drive salinity which is indicative of increasing foam stability. This may be due to an inverse relationship between oil-water IFT and foam stability and thus designing an optimal salinity gradient for an LTG process requires balancing oil mobilization due to ultralow IFT and effectively displacing mobilized oil with adequate foam mobility control.

We introduce and show the strength our compositional LTG simulator in a pioneering laboratory and simulation study that sheds light on the interaction between salinity, microemulsion phase behavior, and foam strength. Our conclusions indicate a significant departure from traditional ASP understanding and methodology when designing an LTG salinity gradient and serve as a foundation for future investigation.
Liquid CO2 EOR Potential in the Illinois Basin: Results of the Mumford Hills Pilot
Authors: Okwen Roland T. , Frailey Scott M.
Published: March 2016

Historically, deep oil reservoirs with temperatures and pressures above the critical point of carbon dioxide (CO2) are generally preferred over shallower reservoirs in enhanced oil recovery (EOR) and CO2 storage operations because of high recovery and storage efficiencies associated with miscible floods. As a result, shallower reservoirs containing significant volumes of recoverable resource are generally overlooked. However, basins with relatively low geothermal gradients and high fracture gradients, such as the Illinois Basin, can sustain pressures above the vapor pressure of CO2 where CO2 changes from a gas to liquid. Liquid CO2 has fluid properties similar to that of supercritical CO2 and is more readily miscible with oil.

This study evaluates the EOR potential of low-temperature reservoirs based on the performance of a miscible liquid CO2 flood pilot at the Mumford Hills oil field in Posey County, Indiana. About 7,000 tons (6,350 tonnes) of CO2 were injected into a Mississippian sandstone reservoir over a period of 1 year to demonstrate miscible CO2 EOR in low-temperature oil reservoirs. The reservoir model was calibrated with available historical primary waterflood, and CO2 flood pilot data. The calibrated reservoir model was used to simulate different full-field CO2 EOR development scenarios. The projected oil recovery factors range between 10% and 14%, which compares well to the Permian Basin supercritical CO2 flood recovery range of 8% to 16%.

The oil recovery factors from the simulated scenarios suggest that liquid CO2 floods in low-temperature oil reservoirs can achieve an incremental oil recovery similar to deeper, supercritical CO2 floods. Re-evaluating previously overlooked shallow depleted reservoirs as potential candidates for liquid CO2 EOR provides the opportunity to increase the development of these shallow oil reservoirs available for miscible CO2 flooding
Capillary Desaturation Curve Fundamentals
Authors: Yeganeh Mohsen , Hegner Jessica , Lewandowski Eric , Mohan Aruna , Lake Larry W. , Cherney Dan , Jusufi Arben , Jaishankar Aditya
Published: March 2016

A capillary desaturation curve (CDC) depicts the relationship between residual oil saturation, Sor, (i.e. oil left behind in a well-swept permeable medium) and capillary number. A CDC is one of the most fundamental curves of oil recovery as it reveals flow conditions required for good oil displacement in porous media. Despite the importance of this critical curve, the fundamentals describing the physics of a CDC are still incomplete.

We present a physical model to describe the capillary desaturation curve. The model balances the capillary pressure and applied viscous stresses caused by flow and takes advantage of contact angle hysteresis that occurs in porous media. It defines a critical oil ganglia length that depends inversely on capillary number and depends on porosity, permeability, and wettability. We have combined the critical oil ganglia expression and ganglia length distribution in porous media to arrive at an expression for the capillary desaturation curve. The model suggests that when a trapped oil ganglion is larger than the critical ganglia length, the applied pressure difference can mobilize the trapped oil ganglion. We describe the differences and similarities between our critical ganglia length expression and previously reported expressions. The model describing the relationship between residual oil saturation and capillary number was successfully verified with microfluidic experiments using various crude oils and displacing fluids. We have also demonstrated that the model applies to previously reported coreflood CDCs from sandstone and carbonate media. Extension of the model led to a single curve representation of variations in Sor with reduced pressure. This representation is independent of the chemistry of the displacing fluid.
Mapping CO2 Floods Using the Depth-to-Surface Resistivity Method: A Technology and Field Example
Authors: Nieuwenhuis Greg , MacLennan Kris , Wilt Michael , Wilkinson Mark , Ramadoss Vivek
Published: March 2016

Depth to Surface Resistivity (DSR) has been shown to be effective at mapping CO2, water flood, and residual oil aerially and vertically. Provided there is sufficient resistivity contrast between injected and in-situ fluids and subject to the reservoir depth and overburden resistivity, the technique is applicable for monitoring IOR/EOR fields. This information can be used to evaluate cap rock integrity, fluid loss to faults, and migration paths. The following paper presents a study of a CO2 flood followed by water alternating gas (WAG) injection.
Investigation of Surfactant Induced Wettability Alteration in Wolfcamp Shale for Hydraulic Fracturing and EOR Applications
Authors: Neog Anirban , Schechter David S.
Published: March 2016

The application of surfactants to improve oil recovery in conventional reservoirs via wettability alteration and enhancement of spontaneous imbibition has been extensively studied in the literature. However, little work has been performed yet to investigate the interaction of these surfactants with ultra-tight oil-rich shale reservoirs such as Wolfcamp shale. The use of horizontal drilling and massive multistage hydraulic fracturing has made primary oil recovery from these ultra-tight oil-rich shale reservoirs possible. With declining production from existing shale wells, it is essential to explore potential "beyond primary" strategies in shale oil development. This paper analyzes the potential of surfactants in altering wettability and improving the process of spontaneous imbibition in oil rich shales demonstrating nanodarcy range permeability, relevant to stimulation and "beyond primary" chemical EOR applications in shales.

Novel proprietary surfactant blends along with traditional nonionic surfactants were investigated in this study using Wolfcamp shale core samples exhibiting nanodarcy permeability. X-ray diffraction analysis was performed which indicated that Wolfcamp shale has mixed mineralogy, with quartz, calcite, and dolomite acting as the major minerals in varying proportions depending on the interval depth. Contact angle and interfacial tension measurements were performed at reservoir temperature to identify the state of native wettability and the impact of surfactants in altering wettability. Thereafter, spontaneous imbibition experiments were performed using 3D computed tomography methods to understand the improvement in the magnitude of imbibition penetration due to surfactant addition. Contact angle and spontaneous imbibition experiments showed that Wolfcamp shale is intermediate-wet and surfactants have the potential to alter the native wettability to a preferentially water-wet state and improve oil recovery due to enhanced spontaneous imbibition.

Surfactants which altered the wettability significantly, but lowered the interfacial tension only slightly showed the highest oil recoveries due to the creation of strong capillary driven forces directly responsible for effective spontaneous imbibition. The potential of surfactants in altering wettability and improving oil recovery via enhanced spontaneous imbibition in ultra-tight oil-rich shales was verified in this study. The effectiveness of traditional nonionic surfactants in altering wettability and improving oil recovery was found to be comparable to that of novel, more expensive proprietary surfactant blends, and hence, the traditional nonionic surfactants provide a cost effective option for stimulation and EOR applications in Wolfcamp shale. Overall, this paper presents the theory behind surfactant interaction with ultra-tight shales and provides experimental results to validate the viability of surfactant induced improved oil recovery in shales.
Snorre In-Depth Water Diversion - New Operational Concept for Large Scale Chemical Injection from a Shuttle Tanker
Authors: Skrettingland K. , Ulland E. N. , Ravndal O. , Tangen M. , Kristoffersen J. B. , Stenerud V. R. , Dalen V. , Standnes D. C. , Fevang Ø. , Mevik K. M. , McIntosh N. , Mebratu A. , Melien I. , Stavland A.
Published: March 2016

Declining oil production and increasing water cut in mature fields highlight the need for improved conformance control. Here we report on a successful in-depth water diversion treatment using sodium silicate to increase oil recovery at the Snorre field, offshore Norway, utilizing a new operational concept of using a stimulation vessel as a platform for the large-scale injection into a subsea well. A custom modified 35,000 DWT shuttle tanker was employed for the field pilot. This paper describes the vessel preparations and the large-scale interwell silicate injection operation. The operational aspects of the large-scale interwell silicate injection include; identification of injection vessel requirements, major vessel modifications, chemical logistic, general logistics to site, major equipment set-up on vessel, subsea connection, mixing and pumping schedules, onsite QC, and real time monitoring. Experience from these operations and lessons learned are included in this paper.

After the injection of approximately 400,000 Sm3 (113,000 Sm3 preflush, followed by 240,000 Sm3 of sodium silicate gelant and 49,000 Sm3 of postflush fluid) at injection rates up to 4,000 Sm3/d, the injection from the vessel was stopped and the well was put on regular seawater injection. Following more than two years of regular production, transient pressure measurements, tracer testing and water cut data are presented from the ongoing comprehensive data acquisition program. These results demonstrate clearly the achieved in-depth flow diversion through a delayed breakthrough of injected tracers and lower water cut in the relevant production well.
Reservoir Modeling and Production Performance Analysis to Investigate the Impacts of Reservoir Properties on Steam-Assisted Gravity Drainage in Cold Lake Oil Sands, Alberta
Authors: Wang Zexuan
Published: March 2016

When compared with steam-assisted gravity drainage (SAGD) operations in the McMurray Formation, Athabasca Oil Sands, SAGD projects in the Clearwater Formation at Cold Lake did not perform as expected, likely because of reservoir properties. This paper will use the Orion SAGD case study to: (1) investigate the impacts of reservoir properties on the SAGD thermal efficiency by field evidences; (2) identify key geological parameters influencing each well pad; and (3) summarize major geological challenges for Orion SAGD expansion.

Wireline log data were interpreted to characterize reservoir properties, which were used to build 3D models. 3D visualizations and 2D cross sections of the reservoir revealed spatial distribution and heterogeneity of each property. SAGD production performance was analyzed using: (1) temperature profiles that monitored the growth of the steam chamber; (2) cumulative steam-oil ratios (CSORs); and (3) oil production rates (OPRates), which are direct indicators of thermal efficiency.

Results show that impermeable barriers and low-permeability zones were detrimental to steam injectivity and steam chamber growth, as observation wells in Pilot Pads 1 and 3 did not detect any steam saturation. High-permeability zones favored high steam injectivity and mobility, especially in Pad 105. Steam chambers were irregularly shaped by high shale-content zones, as two sharp spikes displayed on the temperature profile in Pad 103. Low oil-saturation zones and thin net-pays increased the CSORs, as seen in Pads 106 and 104. Impermeable barriers are almost horizontal, making no difference on well pad orientation by their dip angles. Lack of porosity variation made it difficult to identify the impact of porosity on each well pad.

The relatively extensive distribution of impermeable barriers between and above well pairs, as well as the relatively large area of low oil saturation and thin net-pay, were identified as major geological challenges.
Polymer Flooding: Establishing Specifications for Dissolved Oxygen and Iron in Injection Water
Authors: Jouenne S. , Klimenko A. , Levitt D.
Published: March 2016

It is now common knowledge among EOR practitioners that the combination of ferrous iron (Fe2+) and oxygen causes severe oxidative degradation to EOR polymers, resulting in a lowering of molecular weight and hence a loss of viscosity. During the design of polymer flooding projects, an important question is thus the acceptable levels of Fe2+ and dissolved oxygen that can be tolerated in injection water specifications. Furthermore, we would like to be able to predict the extent of degradation in the case of excess Fe2+ or oxygen ingress.

However, despite over fifty years of research and a general understanding of the degradation mechanism involved, quantitative prediction of the extent of degradation has proven elusive and dependent on the measurement protocol. This is likely due to the fastidious experimental protocols required to work under anaerobic or limited-oxygen conditions.

We examine existing protocols and demonstrate that experiments in which either Fe2+ or oxygen are the limiting reagent yield equivalent results when the stoechiometry of the Fe2+ oxidation reaction with oxygen is taken into account. Based upon these findings, a novel, easy approach is proposed to quantify polymer oxidative degradation as a function of either dissolved oxygen or Fe2+ content.

The limits of 225 ppb Fe2+ and 32 ppb dissolved oxygen are fixed for Flopaam 3630S in 6 g/l brine in the concentration range 500-1500ppm in order to ensure degradation of low-shear plateau viscosity does not exceed 10%. Higher levels will lead to severe polymer degradation. The influence of polymer concentration, temperature and salinity is also investigated. At last, evolution of redox potential and pH during Fe2+ oxidation are discussed.

There is a direct practical application of these finding for the design of surface facilities for polymer dissolution and transport and for the prediction of degradation in case of oxygen ingress. Moreover, a simple and easily performed protocol is proposed for the evaluation of polymer oxidative degradation.
Field Test Results of a New Silicate Gel System that is Effective in Carbon Dioxide Enhanced Recovery and Waterfloods
Authors: Oglesby Kenneth D. , D'Souza David , Roller Chad , Logsdon Ryan , Burns Lyle D. , Felber Betty J.
Published: March 2016

Field test results of a new silicate based Silicate-Polymer-Initiator (SPI) gel system for zonal conformance control are presented from: 3 treatments in a central Mississippi sandstone carbon dioxide (CO2) flood, including 1 producer; 5 injector treatments in a mature, west Texas San Andres dolomite, CO2 flood under Water-Alternating-Gas (WAG) operation; and 2 injector treatments in a northeast Oklahoma waterflood. Gel treatment volumes ranged from 130 to 4,349 barrels of the patented, environmentally friendly, silicate gel system that is pumped at a near water viscosity and density. That pre-gel liquid is triggered to a gel by a pH change caused by external or internal initiation methods. One unique aspect of these silicate solutions is that they can be initiated by both the pre- and post-treatment injected CO2 itself. Alternately, other external and internal initiators can be used in both CO2 and water-floods. Targeted gel times ranged from 1 hour up to 6 days, with maximum gel strength generated within 2–4 weeks. The resultant silicate gels are 10 times stronger than any known gelled polymer system, per CTI laboratory Extrusion and Penetrometer testing. Selected additives were utilized in the gel treatment fluids to focus the pre-gelled solutions into the desired high permeability zones. Furthermore, pre-gel fluid entry into water or oil zones will not set the silicate gel, but will instead dilute the leading edge.

Rate, pressure, injectivity and downhole profile surveys were used to evaluate the treatment in injection wells. Oil, water and gas rates, Water: Oil Ratios, Gas: Oil Ratios and CO2 utilization efficiency were used to evaluate treatments in production wells. Offset production wells were monitored, where possible, for production changes, sometimes seen outside the prior established patterns. Where the data was available, the new silicate gel field treatments were directly compared to prior polyacrylamide and similar conformance systems. In most cases, the new silicate system exhibited positive responses while previous polymer based systems did not respond.