bluuebunny/crossref_metadata_2025 huggingface dataset:
The Influence of Students’ Sociocultural Background on the IELTS Speaking Test Preparation Process
Authors: Pavlovskaya Galina , Lord Anastasia
Published: October 2018

The article is aimed at highlighting the sociocultural factors a teacher/IELTS instructor should consider preparing Russian students for the IELTS exam. The main focus of the study was on four speech functions most frequently used in the IELTS Speaking Test: explaining and paraphrasing, expressing personal opinion, providing personal information, and summarizing. The study aims to question the assumption that the problems arising in the use of these speech functions are provoked by the students’ low language level and to investigate if there are any sociocultural issues connected with the use of the above-mentioned speech functions influencing students’ performance during the IELTS Speaking Test. The study was conducted among first-year students at the Higher School of Economics (HSE) in the Faculty of Computer Science. To see the problem from a different perspective, the study involved not only the first-year students who seem to struggle with the speech functions but also their English teachers who can provide trustworthy first-hand information on the problems the students frequently face. The results of the study demonstrate that the cause of problems students encounter using the speech functions should not be attributed only to their language knowledge, as do the majority of interviewed teachers. The way students tend to explain, paraphrase, summarize, express their opinion and provide personal information is culturally defined which influences students’ ability to perform these functions effectively. To help Russian students avoid sociocultural problems preparing for the IELTS Speaking Test, a teacher/IELTS instructor should aim to increase students’ sociocultural awareness of the pitfalls in the use of the essential speech functions and sociocultural competence in a foreign language.
Giant retroperitoneal liposarcoma during pregnancy: case report
Authors: Paul Dhruba Prasad , Garg Kashish
Published: October 2018

24-year-old woman was presented with huge vulval mass for which she was operated, histopathological report of that mass shows angiomyoma. After few months she was discovered to have a giant retroperitoneal tumor incidentally during her routine obstetric examination at 24 weeks of gestation. Initial investigation by abdominal-pelvic computed tomography (CT) (18/08/18) revealed an a large multiseptated soft tissue attenuated minimally enhancing pelvic mass (31.8cmx13.2x 24cm) protruding in the abdominal cavity displacing the bowel loops proximally and pushing retro organs posteriorly. She underwent laparotomy with preservation of the fetus at 24 weeks of gestation. Final diagnosis was made after HPE report which shows myxoid liposarcoma. She was referred to regional cancer hospital for radiotherapy and then patient lost in follow up.
Mass occurrence of the liverwort Herbertus sendtneri in a glacial lake in the Andes of Colombia
Authors: Gradstein Robbert , Vanderpoorten Alain , Van Reenen Guido , Cleef Antoine
Published: October 2018

Muchas especies de briófitas tropicales crecen en habitats periódicamente inundados como lechos del río, pantanos y cascadas, pero se presentan pocos briófitas sumergidas permanentamente y están más que todo en lagunas de alta montaña. Su identificación podría ser dificil por la modificación de rasgos inducidos por el medio acuático. Aquí se trata de una población sumergida del género Herbertus de las hepáticas de una laguna glaciar a 4120 m en la Sierra Nevada del Cocuy, Colombia. Las plantas acuáticas caracterizadas por el porte enano y los apices obtusos de las hojas. Se ha identificado como H. oblongifolius, un taxon raro descrito de Brazil y recientemente, basado en la morfología, ubicada como sinónima de la especie variable, H. sendtneri, de distribución amplia. Análisis molecular ha confirmado que las plantas acuáticas pertenecen a H. sendtneri. La semejanza de las plantas acuáticas con las ramitas de H. sendtneri parece de sugerir un fenótipo juveníl. Las plantas acuáticas probablemente tienen su origen en una población en las rocas y lajas cercanas y han llegado a la laguna a través de ramitas vegetativas caedizas y así traidas a la laguna por el viento y el agua, o plantas enteras entraron a la laguna con lluvias fuertes inundando las lajas. © 2018. Acad. Colomb. Cienc. Ex. Fis. Nat.
Atividades farmacológicas do monoterpeno 1,8-cineol: um estudo in silico
Authors: Souto Ingrid Carneiro Cavalcante , Ferreira José Lucas Soares , Oliveira Heloísa Mara Batista Fernandes de , Alves Maria Angélica Sátyro Gomes , Oliveira Filho Abrahão Alves de
Published: October 2018

Os óleos essenciais são os principais compostos de uso terapêutico derivados de plantas, amplamente utilizados na produção de perfumes e cosméticos, apresentando também efeito farmacológico. Dentre os vários componentes dos óleos essenciais estão os terpenos; estes resultam do metabolismo secundário das plantas. O 1,8-cineol ou eucaliptol, é um monoterpeno de grande índice terapêutico segundo a literatura. O presente estudo objetiva realizar uma análise in silico do 1,8- cineol para atividade anti-hipertensiva, antiasmática e analgésica. Com a análise in silico do monoterpeno pode-se observar que este composto apresenta maiores valores de Probabilidade de ser ativos ara as atividades estudadas, em relação aos valores de Probabilidade de ser inativo. Portanto, conclui-se que o 1,8-cineol é um potente candidato a fármaco com várias atividades terapêuticas, de acordo com os estudos in silico.
Aceitação de metodologias de ensino à distância na área da saúde: Uma revisão integrativa
Authors: Benelli Jéssica Louise , Gil Lourdes Da Silva
Published: October 2018

O presente estudo trata-se de uma revisão bibliográfica com o objetivo de avaliar a aceitação e inserção da metodologia EAD por estudantes e profissionais na área da Saúde, descrevendo metodologias realizadas, seus resultados e impacto na formação dos participantes. Para isso foi realizada busca em bases reconhecidas de artigos científicos que contenham as expressões: “EAD e saúde”, “e-learning health”, e “e-learning and health”. Foram incluídos 43 artigos, dos quais 11 foram sobre metodologias nacionais, e os demais em diversos países de diferentes continentes. Na maioria das metodologias foi utilizado o ambiente virtual de aprendizagem, sendo o Moodle a plataforma mais citada, aplicada tanto a profissionais já formados, no contexto de formação continuada, quanto à alunos de graduação e pós-graduação, de modo complementar ao conhecimento presencial. Das iniciativas realizadas 90,5% tiveram resultados positivos, algumas inclusive com resultados superiores aos de metodologias presenciais comparativas, sendo os resultados negativos associados à falta de engajamento dos tutores e professores ou a falta de dinamicidade da estratégia realizada. A presente revisão nos mostra que o ensino à distância tem sido utilizado para aprimorar, aumentar e consolidar conhecimentos inerentes à pratica dessas profissões de forma muito proveitosa, além disso, permite, na Saúde, a democratização do acesso aos recursos, sendo uma ferramenta também de Saúde Pública.
A Monte Carlo Simulation Study Robustness of MANOVA Test Statistics in Bernoulli Distribution
Authors: Şahin Mustafa , Koç Şeyma
Published: October 2018

The aim

of this study is to compare the robustness of Manova test statistics against

Type I error rate using the Monte Carlo simulation technique. In the method,

numbers are generated according to constant and increasing variance for g=3,4,5 group p=3,5,7 dependent variables n=10,30,60

sample size using the R. Numbers have been produced using these 54

combinations. Pillai Trace test statistic has been the least deviating from the

nominal α =0.05

value. Wilk Lambda and Hotelling-Lawley Trace test results were close to each

other. The researchers can decide according to the comparison results of the

analysis's suggested decision stage.
Reference Class Forecasting Method in Predicting Construction Project Duration
Authors: Bayram Savaş , Al-jıbourı Saad
Published: October 2018

Project

delay is a global problem affecting construction and other industries in many

countries. Its impact on planning and budgeting can be serious for all

stakeholders involved and difficult to resolve. The purpose of this study is to

analyze the reliability of duration estimates of public building projects based

on actual duration of similar projects carried out in the past.Turkey is used

as a case study for this purpose and data from 643 public building projects

completed in Turkey were collected. The data include contract durations, actual

durations as well as the total construction areas for all projects. Reference

Class Forecasting (RCF) method is proposed and used to investigate whether it

would be possible to produce reliable and realistic project duration forecasts

based on such data. RCF can realistically predict the actual final duration of

the projects of different reference classes for various levels of acceptable

risks. Original estimates of the contract durations in Turkey are generally

optimistic or underestimated. Government buildings with the highest average

construction area required lower uplift values on the estimated durations to

produce accurate and realistic forecasts.So far the RCF method has been broadly

applied to predict project cost rather than duration. This paper describes it

use for forecasting duration in building projects.
Avoiding AGI races through self-regulation
Authors: Worley III G Gordon
Published: October 2018

The first group to build artificial general intelligence or AGI stands to gain a significant strategic and market advantage over competitors, so companies, universities, militaries, and other actors have strong incentives to race to build AGI first. An AGI race would be dangerous, though, because it would prioritize capabilities over safety and increase the risk of existential catastrophe. A self-regulatory organization (SRO) for AGI may be able to change incentives to favor safety over capabilities and encourage cooperation rather than racing.
Mass Balance of Novaya Zemlya Archipelago, Russian High Arctic, using Time-Variable Gravity from GRACE and Altimetry Data from ICESat and Cryosat-2
Authors: Ciracì Enrico , Velicogna Isabella , Sutterley Tyler Clark
Published: October 2018

We examine the mass balance of the glaciers in the Novaya Zemlya Archipelago, located in the Russian High Arctic using time series of time-variable gravity from the NASA/DLR Gravity Recovery and Climate Experiment (GRACE) mission, laser altimetry data from the NASA Ice Cloud and land Elevation Satellite (ICESat) mission, and radar altimetry data from the ESA CryoSat-2 mission. We present a new algorithm for detecting changes in glacier elevation from these satellite altimetry data and evaluate its performance in the case Novaya Zemlya by comparing the results with GRACE. We find that the mass loss of Novaya Zemlya increased from 10±5 Gt/yr over 2003-2009 to 14±4 Gt/yr over 2010-2016, with a brief period of near mass balance between 2009 and 2011. The results are consistent across the gravimetric and altimetric methods. Furthermore, the analysis of elevation change from CryoSat-2 indicates that 60\% of the mass loss occurs at low elevation, where thinning rates are highest. We also find that marine-terminating glaciers in Novaya Zemlya are thinning significantly faster than land-terminating glaciers, which indicates an important role of ice dynamics of marine-terminating glaciers. We posit that the glacier changes have been caused by changes in atmospheric and ocean temperatures. We find that the increase in mass loss after 2010 is associated with a warming in air temperatures, which increased the surface melt rates. There is no enough information on the ocean temperature at the front of the glaciers to conclude on the role of the ocean, but we posit that the temperature of subsurface ocean waters must have increased during the observation period.
Structural, Magnetic and Mossbauer studies of Transition metal doped Gd2Fe16Ga0.5TM0.5 intermetallic compounds (TM=Cr, Mn, Co, Ni, Cu, and Zn)
Authors: Dahal Jiba , Kalangala Sikkanther Batcha Syed Ali , Alam Jahangir
Published: October 2018

The effect of transition metal substitution for Fe and the structural and magnetic properties of Gd2Fe16Ga0.5TM0.5 (TM=Cr, Mn, Co, Ni, Cu, and Zn) compounds were investigated. Rietveld analysis of X-ray diffraction indicates that all the samples crystallize in the hexagonal Th2Ni17 structure. The lattice parameters: a, c and unit cell volume show TM ionic radii dependence. Both Ga and TM atoms show preferred site occupancy for 12j and 12k sites. The saturation magnetization at maximum room temperature was observed for Co, Ni, and Cu of 69, 73, and 77 emu/g, respectively while minimum value was observed for Zn (62emu/g) doping Gd2Fe16Ga0.5TM0.5. Highest Curie temperature of 590 K was observed for Cu doping which is 15% and 5% and thesehigher than Gd2Fe17 and Gd2Fe16Ga compounds, respectively. The hyperfine parameters viz. hyperfine field and isomer shift, show systematic dependence on the TM atomic number. The observed magnetic and Curie temperature behavior in Gd2Fe16Ga0.5TM0.5 is explained on the basis of Fe(3d)-TM(3d) hybridization. The superior Curie temperature and magnetization value of Co, Ni, and Cu doped Gd2Fe16Ga0.5TM0.5 compounds as compared to pure Gd2Fe17 or Gd2Fe16Ga makes Gd2Fe16Ga0.5TM0.5 a potential candidate for high-temperature industrial magnet applications.
A Qualitative Investigation of Farmer and Rancher Perceptions of Trees and Woody Biomass Production on Marginal Agricultural Land
Authors: Hand Ashley , Tyndall John C.
Published: October 2018

Bioenergy produced from perennial feedstocks such as woody biomass could serve as an opportunity to strengthen local and regional economies and also jointly produce various environmental services. In order to assess the potential for biomass- based bioenergy, it’s essential to characterize the interest that potential biomass suppliers have in such an endeavor. In the U.S. Great Plains region, this largely means assessing relevant perceptions of farmers and ranchers. We conducted a series of farmer and rancher oriented focus groups in North Dakota, South Dakota, Nebraska and Kansas to qualitatively explore opinions about the role that trees can play in agriculture and interest in woody biomass systems within existing Northern Great Plains (NGP) farms and ranches. Our findings suggest that farmer and ranchers generally value the role that trees, or tree-based practices like windbreaks can play in agriculture particularly on marginal farmland in terms of conservation or crop protection. Yet relative to the potential of trees as a biomass crop there is a distinct lack of knowledge and skepticism. Farmers and ranchers also noted variable degrees of risk concern and uncertainty regarding investing in tree-based systems, as well as a number of perceived external market related constraints to integrating trees within their managed systems. Most of the participants recognized that if biomass production or an increase in tree planting and management in general were to expand in the NGP region, government programs would likely be required to provide much needed technical guidance and financial incentives. As the NGP regional bioeconomy continues to emerge and expand, private and public investment relative to niche bioenergy feedstocks such as woody biomass should address the type of information needs that farmers and ranchers have relative to integrating biomass production into existing farm and ranch systems.
Diabetes mellitus tipo 2 podría predecir una pérdida subóptima de peso después de una cirugía bariátrica
Authors: Núñez-Núñez Mizael A. , León-Verdín M. Guadalupe , Muñoz-Montes Norberto , Rodríguez-García Judith , Trujillo-Ortiz J. Abraham , Martínez-Cordero Claudia
Published: October 2018

Introducción: la cirugía bariátrica no beneficia a todos los pacientes. Identificar a los pacientes gravemente obesos que tendrán éxito después de la cirugía bariátrica sigue siendo un reto para el equipo transdiciplinario. El objetivo de este estudio retrospectivo fue analizar factores dietéticos preoperatorios que pudieran predecir una pérdida de peso exitosa después de la cirugía bariátrica.Métodos: el estudio retrospectivo incluyó a pacientes sometidos a una cirugía de bypass gástrico laparoscópico en Y de Roux como procedimiento para obesidad severa (n = 84). Datos demográficos del paciente, comorbilidades, factores dietéticos y los resultados de pérdida de peso se extrajeron de la historia clínica electrónica.Resultados: la diabetes mellitus tipo 2 (DM2) se asoció con una pérdida subóptima de peso después de una cirugía de bypass gástrico laparoscópicoen Y de Roux.Conclusiones: aunque la cirugía bariátrica sigue siendo el tratamiento más efectivo para los pacientes con obesidad severa, es fundamental desarrollar estrategias para mejorar y mantener la pérdida de peso, especialmente en pacientes con DM2. Evaluar las características dietéticas de los candidatos a cirugía bariátrica es crucial.
Pointing the Foot Without Sickling: An Examination of Ankle Movement During Jumping
Authors: Jarvis Danielle N , Kulig Kornelia
Published: October 2018

The sauté is a relatively simple dance jump that can be performed by both highly skilled dancers and non-dancers. However, there are characteristics of jumping unique to trained dancers, especially in terms of foot and ankle movement during flight. Dancers are trained not to
“sickle,” or to avoid the anatomically coupled ankle inversion that occurs with plantar flexion, maintaining the appearance of a straight line through the lower leg and foot. The purpose of this study was to examine ankle movements in elite dancers compared to non-dancers. Twenty
healthy females, 10 with no prior dance training and 10 professional dancers, performed 20 consecutive sautés while three-dimensional kinematic data were collected. Sagittal and frontal plane kinematics were calculated and vector coding methods were used to quantify coordination patterns
within the ankle in the sagittal and frontal planes. This pattern was chosen for analysis to identify the avoidance of a sickled foot by trained dancers. Peak ankle positions and coordination patterns between groups were examined using independent t-tests (a<0.05). Dancers demonstrated
greater peak plantar flexion (p<0.01) and less change in ankle angle during the flight phase (p=0.01), signifying holding the pointed foot position during flight. There was no statistically significant difference in sagittal and frontal plane ankle coupling (p=0.15); however, the Cohen’s
d effect size for the difference in coupling was medium-to-large (0.73). Dynamic analysis of the foot and ankle during jumping demonstrates how elite dancers achieve the aesthetic requirements of dance technique.
Heart Rate Response of Professional Musicians When Playing Music
Authors: Vellers Heather L , Irwin Conor , Lightfoot JT
Published: October 2018

Objectives: The primary aim was to determine the level of physiological stress evoked while playing music in a standing position as indicated by heart rate (HR) response. A secondary aim was to analyze the effect of music genre (classic rock, western, contemporary Christian, and metal
rock) on the relative HR response. Lastly, we considered potential physiological initiators of the music-playing-induced HR response. Methods: HR response was monitored in 27 professional musicians (3 women, 24 men) between the ages of 21and 67 yrs old during rehearsal and public performances.
The percent maximal HR (%MHR) evoked was determined by taking a percentage of the age-predicted maximal HR for each musician and comparing the average %MHR in each genre during public and rehearsal events. The role of the potential initiators of these responses (e.g., number of years playing
in public, event type, instrument type, tempo, etc.) was determined using multiple regression analyses. Results: The overall average %MHR responses were 52±5% and 59±5% during rehearsal and public performances, respectively, with genre type having a significant effect on the
HR response (p=0.01). Body mass index and tempo were each found to be significant contributors to the HR response while playing music (r2=0.506, p=0.001). Conclusion: Playing music professionally evokes considerable increases in HR response, with music genre influencing the level of the physiological
response. We concluded that 50% of the HR response while playing music was associated with body mass index, music tempo, and instrument type.
Christopher Wynn Parry (1924–2015)
Authors: Winspur Ian
Published: October 2018

Performing Arts Medicine lost a great practitioner, friend, and advocate last month with the death of Dr. Christopher Wynn Parry.
Nanoparticles as Foam Stabilizer for Steam-Foam Process
Authors: Khajehpour Maryam , Reza Etminan S.. , Goldman Jon , Wassmuth Fred , Bryant Steven
Published: October 2018

Steam foams have been considered effective additives for unconventional oil-recovery processes. Conventionally, for steam-foam applications, chemical additives are injected with steam. However, this procedure can have serious challenges because of poor thermal stability of additives and high volume of additives loss caused by adsorption to the rock surface. To overcome these limitations, nanoparticles can be used as novel additives to improve generation and stabilization of the foams for steam-foam applications.

In this study, silica nanoparticles in synergy with surfactants have been used as steam additives. Dynamic light scattering (DLS), a foam-height test using N2 at reservoir conditions, and thermal-stability analysis were designed to measure nanoparticle size distribution in brine, foamability, and thermal stability of the additive solutions, respectively. Subsequently, coreflooding tests were performed to evaluate the synergistic effect of nanoparticles and surfactants on the foam performance and oil recovery. We observed an optimal ratio of nanoparticle and surfactant that yields the best foam-generation performance in bulk medium. Herein, surface-treated silica nanoparticles have been tested with two of our candidate surfactants. The nanoparticles alone generate a small amount of foam, whereas each surfactant generates a small-to-moderate amount of foam. Synergy is demonstrated by the system that contains 0.1-wt% nanoparticles (the optimal concentration) and 0.5-wt% surfactant solution at neutral pH (≈7), as it leads to approximately 67 and 50% greater foam height, respectively, for Surfactants A and B than foam height observed in tests with surfactants only, in bulk medium. Corefloods with coinjected steam and water containing nanoparticles and surfactant confirm the synergy, exhibiting measurable improvement in mobility-reduction factor (MRF) and steam control, compared with coinjection of steam and water containing only surfactant.
A Semianalytical Model for Pressure-Transient Analysis of Fractured Wells in Unconventional Plays With Arbitrarily Distributed Discrete Fractures
Authors: Chen Zhiming , Liao Xinwei , Sepehrnoori Kamy , Yu Wei
Published: October 2018

In this paper, we present an efficient semianalytical model for pressure-transient analysis in fractured wells by considering arbitrarily distributed fracture networks. The semianalytical model included three domains: matrix, hydraulic-fracture networks, and discrete natural fractures. Using the line-source function, we developed the diffusivity equation for fluid flow in matrix. By applying the vertex-analysis technique, we eliminated the flow interplay at fracture intersections and established the diffusivity equations for fluid flow in hydraulic-fracture networks and isolated natural fractures. The pressure-transient solution of these diffusivity equations was obtained using Laplace transforms and the Stehfest numerical inversion.

Results showed that with the discrete natural fractures, a “V-shaped” pressure derivative (the classical dual-porosity feature of naturally fractured reservoirs) emerged. With the hydraulic-fracture networks, the reservoir system would exhibit pressure behaviors such as “pseudoboundary-dominated flow,” “fracture-interference flow,” and “fluid-feed flow.” All these pressure characteristics were dependent on the properties and geometries of natural/hydraulic fractures. In addition, through synthetic field application, we found that different (natural/hydraulic) fracture distributions and geometries had distinct behaviors of pressure derivatives, which may provide an effective tool to identify the properties of randomly distributed natural fractures as well as complex hydraulic fractures in unconventional plays.
Centrifugal Pump Head Prediction using Affinity Laws Modified for Viscosity
Authors: Patil Abhay , Morrison Gerald , Delgado Adolfo , Casillas Hector
Published: October 2018

A new approach based on the similitude principle is used to evaluate the effect of fluid viscosity on pump performance. A well validated CFD technique of the entire stage of a mixed flow pump including the secondary flow path is utilized to develop this method. Simulations are carried out at different fluid viscosities representing the pump performance in laminar as well as turbulent flow regimes. The non-dimensional parameters such as head coefficient (Ψ), flow coefficient (ϕ) and rotational Reynolds number (Re) are utilized to characterize the pump performance. The head coefficient data for all viscosities collapsed to two separate lines when represented as a function of Φ∗Rew−a with each representing the separate flow regime for pump flow. The exponent "a" (called the Morrison number) is characterized as a function of the rotational Reynolds number and the specific speed of the pump. This procedure has the potential to completely characterize the performance of any pump with any specific speed at any operational speed, however, a larger data base is required to completely populate the Morrison number plot.
Efficacy of Surfactants in Rich Gas Shale Wells
Authors: Alzhanov Yermek , Karami Hamidreza , Pereyra Eduardo , Gamboa Jose
Published: October 2018

Foam lift has proven to be an effective method to mitigate liquid loading in unconventional resource (UCR) wells. Water-soluble surfactants are commonly used when liquid loading is mainly caused by formation water. There is a larger uncertainty involving the efficacy of water-soluble surfactant at water cuts below 80%. Therefore, oil-soluble surfactants are recommended. However, high oil-soluble surfactant price causes a significant increment in Opex, which can make the well production uneconomical.

Flow loop tests have been carried out in a closed-loop 2″ ID facility to emulate continuous backside foam injection. The oil condensate is emulated using a low density commercial isoparaffin oil, while tap water and compressed air are used instead of formation water and natural gas. The experiments are conducted at water cut values that range between 70% and 100% for surfactant concentration of 250 ppm. The foamer surfactant is a commercial water-soluble surfactant that is commonly used in oil field applications. The liquid loading onset is primary parameter obtained from each test through video and data analysis. Other parameters such as flow pattern and pressure gradient are also reported.

The experimental results show that liquid loading initiates at gas flow rates around 252 MSCFD for air-water flow in a 2-in. ID tubing. Adding the condensate fraction with a fixed total liquid rate and no surfactant slightly increases the critical gas rate. After surfactant injection, the reduction in critical gas flow rate is approximately 40% for most water cuts except the case of 70% water cut, where the oil presence seems to inhibit the surfactant effectiveness. Visual observations at this case show a significant reduction in generated foam, and relatively similar flow pattern transitions as the case of no surfactant. These results demonstrate that water-soluble surfactants are very effective in mitigating liquid loading at high water cuts, but their effectiveness reduces as water cut decreases. This causes an increase in the critical gas flow rate despite foam injection.

Currently, most operators aim to produce from condensate-rich shale in order to increase profit. The results of this study offer a first look in the following two issues. First, the effect of oil in liquid loading is investigated and the effectiveness of surfactant at different water cuts is evaluated. Second, the results can be used to design cost effective treatments based on water-soluble surfactants. Most literature about the effect of water cut on surfactant injection effectiveness is based on small scale lab. This experimental study is one of the few flow loop tests to investigate the effect of oil on the onset of liquid loading with surfactant.
End of Tubing and Packer Placement Effects on Gas Lift Operations in Toe Down Gas Wells
Authors: Nair J.. , Pereyra E.. , Sarica C..
Published: October 2018

Gas lift operations in toe-down gas wells are usually dictated by convenience or knowledge based on previous experience. Parameters such as end of tubing location and packer placement are vital in determining efficacy of gas lift operations, alongside injection rate and injection location. The aim of this study is to quantify the effects of these parameters. The scope of this study is to provide guidelines to help assist design of gas lift systems for toe down gas wells.

A large scale experimental facility was constructed to study gas lift operations in toe-down gas wells. Air and water were used as test fluids, and the flow rates studied were those typically seen in toe down gas wells, resulting in slug flow being the dominant flow regime. Three end of tubing locations were studied, and in two of these locations the effect of a packer was quantified. Two different injection locations were studied as part of this study. Flow parameters such as pressure drop, holdup and slug characteristics were measured along the test facility.

Experimental results indicated that gas lift operations do not significantly affect the behavior of flow parameters such as holdup and pressure, upstream of the point of injection. The most significant effect of gas lift is observed to be a reduction of pressure drop fluctuations downstream of the point of injection. Packer placement also significantly affects gas lift performance, and it was observed that packered configurations are more efficient. Also, for a given end of tubing location, gas lift injection at the deepest point is observed to be the most effective in reducing pressure drop fluctuations.

This is the first experimental study conducted on the effect of end of tubing location and packer placement on gas lift operations on a large-scale test facility with field scale diameters for casing and tubing. Packer placement is currently dictated by mechanical concerns and depth limitations. This study addresses potential risks and benefits of running a packer as deep as possible, from a hydrodynamic standpoint.
Integrated Well Interference Modeling Reveals Optimized Well Completion and Spacing in the Marcellus Shale
Authors: Pankaj Piyush , Shukla Priyavrat , Kavousi Payam , Carr Timothy
Published: October 2018

Naturally fractured reservoirs such as the Marcellus shale require an integrated reservoir modeling approach to determine well spacing and well-to-well interference. The Marcellus Shale Energy and Environment Laboratory (MSEEL) is a joint project between universities, companies, and government to develop and test new completion technologies and acquire a robust understanding of the Marcellus shale. The study presented in this paper aims to reveal an approach to determine reservoir depletion with time through coupled geological modeling and geomechanical evaluation followed by completion and well performance history matching for a multiwell pad in the Marcellus shale.

The geomechanical model was prepared with interpreted vertical log data. A discrete natural fracture (DFN) model was created and used to determine the complexity of hydraulic fracture geometry simulated through complex fracture models on a two well pad. The microseismic data obtained during the hydraulic fracture simulations served as a constraining parameter for the hydraulic fracture footprint in these wells. Sensitivity to the DFN is realized by parametric variations of DFN properties to achieve a calibrated fracture geometry. Reservoir simulation and history matching the well production data confirmed the subsurface production response to the hydraulic fractures. Well spacing sensitivity was done to reveal the optimum distance that the wells need to be spaced to maximize recovery and number of wells per section.

Hydraulic fracture geometry was found to be a result of the calibration parameters, such as horizontal stress anisotropy, fracturing fluid leakoff, and the DFN. The availability of microseismic data and production history matching through integrated numerical simulation are therefore critical elements to bring unique representation of the subsurface reaction to the injected fracturing fluid. This approach can therefore be consistently applied to evaluate well spacing and interference in time for the subsequent wells completed in the Marcellus. With the current completion design and pumping treatments, the optimal well spacing of 990 ft was determined between the wells in this study. However, wells to be completed in the future needs to be modeled due to the heterogeneity in the reservoir properties to ensure that wells are not either underspaced to cause well production interference or overspaced to create upswept hydrocarbon reserves in the formation.

By adopting the key learnings and approach followed in this paper, operators can maximize subsurface understanding and will be able to place their wellbore in a nongeometric pattern based on reservoir heterogeneity to optimize well spacing and improve recovery.
Heavy Oil Waterflood Application of Capacitance Resistance Models
Authors: Zhang Tiantian , IZGEC Omer , Sayarpour Morteza
Published: October 2018

The capacitance-resistance model (CRM) is an analytical tool that uses only injection and production rate to quantify interwell connectivity and response time during a waterflood. It has been widely used in conventional waterfloods for reservoir characterization, performance evaluation and optimization. Heavy oil waterfloods introduce challenges to the application of CRM due to the high mobility ratio and its rapid variation as a function of waterflood maturity. Using conceptual reservoir models and sensitivity studies, we provide guidelines for application of CRM in heavy oil waterfloods. We illustrate our approach in two heavy oil fields under waterflood.

In heavy oil waterfloods, it is observed that interwell connectivity and response time varied over time, especially right before and after water breakthrough. The magnitude of CRM parameter variation is a function of viscosity ratio between water and oil, flood maturity, and contrast of flow and storage capacity of the flow units. Case studies of heavy oil watetrflood (one mature, one immature) showed that CRM can be used for waterflood analysis, and forecasting. In the immature flood with one injector and two producers and high permeability contrast, the most extreme variation of CRM parameters was observed. In the pattern flood where injected fluid was distributed relatively evenly among producers and breakthrough had already occurred, the CRM parameters tended to be constant over time. We showed that with frequent analysis (window approach) CRM can be efficiently used in heavy oil waterfloods,
Applications of Progressive-Recursive Self-Organizing Maps Algorithm in Guiding Reservoir History Matching
Authors: Al-Turki Ali A. , Al-Dossary Mubarak N. , Al-Ghamdi Amell A. , Al-Harbi Badr M.
Published: October 2018

Reservoir model history matching is a complex, time-consuming, and resource intensive process that needs to be carried out carefully for building reliable predictive tools to manage Oil & Gas assets. Reservoir models encompass detailed geological description representing subsurface heterogeneities that influence its dynamics. To intelligently manage and preserve the complexity of the reservoir models, an artificial intelligence, Progressive-Recursive Self-Organizing Maps (PR-SOM), algorithm was developed. PR-SOM is an unsupervised artificial intelligence neural network algorithm that classifies the reservoir grid cells into progressive reservoir parameters to identify similarly adjoining regions. The algorithm explores and identifies model geo-bodies with similarities and dissimilarities in a progressive and recursive manner. This allows history matching to be conducted on much smaller subsets of the reservoir model of similar geological features.

In this work, an artificial intelligence (AI) algorithm was applied, first, to guide the reservoir-wide history match processes. Next, the algorithm was applied to fine-tune well performance using information form well testing and historical data. The algorithm uses both static properties (permeability, rock quality indices, porosity, flow zonation … etc.) and dynamic properties (pressure or saturation) to construct similarities matrix. The results show that the clusters’s growth is progressive, controlled and quality assured by accounting for the controlling reservoir parameters. The number of mapped regions (clusters) is determined by optimizing the similarity matrix recursively. The quality of the global reservoir history match shows the effectiveness of the algorithm, better quality matching for historical production data, and fewer iterations (i.e. less simulation runs). The process is repeated to calibrate the reservoir model near wellbores by limiting the AI algorithm to only the drainage regions seen from well tests and historical data.

The results show that employed AI-guided history matching revealed similarities and dissimilarities in the reservoir model. That not only enhance field and well match, but also allowed us to maintain the heterogeneity contrasts inherited from the Earth model. The advanced algorithm was successfully used to assess the extent of geological heterogeneity and its impact on reservoir dynamics, to enhance history match quality, minimize human interaction, and to reduce computational requirements.
Extended Reach U-Shape Re-Entry Drilling in Shallow Depleted Fractured Reservoirs in Congo Offshore Oldest Oilfield
Authors: Tony Chembou Mike , Bruno Valeri , Loïs Crevoisier de , Michel Akue , Vincent Rodet , Gabriele Ghia , Achille Mouamba , Ali Lazzem
Published: October 2018

Congo has been an oil producing country since the 70's, it is in this context of aging oilfield and low oil price environment that a redevelopment project was launched to give a second life to a shallow, depleted, mature, offshore oilfield with viscous oil (22° API) in a cost-effective manner.

The solution selected was to drill "U-shape" side tracks (inclination at TD 115deg) from the original boreholes on an existing platform (60m WD). The objective was to create a second drainage area of up to 500m, ~200m away from the original producing zone. Five re-entries U-shape wells were delivered with measured to vertical depth ratios up to 2.5 in shallow heavily depleted reservoirs (270m TVD). The team selected innovative and low cost techniques to overcome many challenges, from high DLS in unconsolidated formations using simple mud motor BHA, to running 4-1/2" liner up to 115deg inclination and implementing a thixotropic mixed metal oxide mud system to mitigate losses.

The project has been successful both from a budget and production standpoint.
A Method for Improving the Evaluation of Elemental Concentration in Neutron-Induced Gamma-Ray Spectroscopy Logging
Authors: Liu Juntao , Liu Shucai , Yuan Chao , Zhang Feng , Yan Huizhong , Miao Bin , Li Hu
Published: October 2018

The determination of elemental concentrations, mineralogy and lithology is essential for the evaluation of unconventional plays. Several instruments utilizing D-T generator and gamma ray detectors have been developed to determine elemental weight fractions. The measured gamma ray energy spectrum can be approximated by a linear combination of the standard spectra of individual elements. Each geochemical well logging instrument has its unique set of elemental standards, which can be obtained by experimental approaches. The variations of the shapes of elemental standards are not considered under different conditions and it affects the accuracy of the elemental concentrations.

A decomposition of measured spectrum is carried out based on the elemental standard spectra to determine the relative elemental yields, which represent the contribution of gamma rays emitted by each element to the measured spectrum. Then the elemental yields can be converted to elemental weight fractions by using oxide closure model. The standard gamma ray spectra of individual elements are calculated by using Monte Carlo numerical simulation. The responses of standard spectra under different conditions such as different borehole sizes and drilling mud types, are simulated. The reasons for the change of the standard spectra shape are analyzed. A model based on gamma ray attenuation is introduced to compensate for the effects of logging conditions on the changes of standard spectra.

The simulation results show that variation of logging conditions have impacts on the shapes of the standard libraries. Therefore, if only one set of fixed standard spectra is utilized in processing measured spectra, the accuracy of elemental concentrations is affected. To address this problem, a model for compensating for the variations of the shapes of standard spectra is proposed. A field example of pulsed neutron spectroscopy logging is illustrated to validate the proposed method and results show that the agreement between computed elemental weight fractions and core analysis values is improved.

In the processing of geochemical logging data, changes in the shapes of the standard spectra were not considered. One set of fixed elemental standards are always utilized. In our study, a specific Monte Carlo simulation code is used to study the changes of elemental standards due to the variation of logging conditions and a method is proposed to improve the accuracy of elemental concentration measured by geochemical well logging.
Collapse and Bending Analysis of Slotted Liners by 3D FEM under Various Reservoir Conditions
Authors: Liu Xiaoda , Morita Nobuo
Published: October 2018

The goal of the research is to study the structural integrity and slot width change of slotted liners by 3D finite element analysis and experimental study. Slotted liners are widely used because of the abilities to ensure wellbore integrity and sand control. During installation and operations, the slotted liners have to be strong enough to hold axial loads and radial compression to prevent excessive buckling and deformation of slots. Experiments were designed to select the grades of materials, diameter/thickness of pipes, and slot pattern. Finite element models were developed to predict the integrity of slotted liners and acceptable slot width changes. The study considered slotted liner design and analyzed how much material grades, casing/tubing dimension and slot patterns affect the risk of slotted liner failure.
The Importance of Clean Off-Plane Perforations in All Phases of a Deepwater Well and Its Productivity Impact
Authors: Mahadev Karthik A.V. , Haldipur Prashant , Tinker Steven J. , Stewart Carlos , Roy Alistair M.
Published: October 2018

High permeability reservoirs in Deepwater Gulf of Mexico have been completed with fracpacks resulting in high production rate wells. The initial production rates for these wells range from 3 mbd to almost 40 mbd; and these rates can be sustained over extended periods of time (several years). Most of these developments in the Gulf of Mexico require sand control with cased hole fracpacks as the preferred completion technique. In addition to providing reliable sand control, fracpacks result in relatively low skin by bypassing near wellbore damage. Over the past few years, operators have focused on reducing skin and improving the production from these wells; leading to a more detailed analysis of fracpack performance. This paper will demonstrate that in high permeability reservoirs, production from the off-plane perforations is as important as production from the fracture. It examines the theoretical basis of the contribution of off-plane perforations to total flow and demonstrates the adverse effect on this contribution due to damage from drilling fluids and solids, cementing spacers and solids, fluid loss materials, perforating debris, wellbore debris, and crosslinked gel. Several case histories are analyzed to evaluate and quantify these effects and to show that the lower the conductivity contrast between the (high permeability) reservoir and the fracture, the higher the production benefit that can be realized by effectively cleaning the off-plane perforations.
Lessons Learned from In-well Fiber-optic DAS/DTS Deployment
Authors: Sanni Modiu , Hveding Frode , Kokal Sunil , Zefzafy Ibrahim
Published: October 2018

Fiber-optic sensing technology has gradually become one of the pervasive tools in the monitoring and surveillance toolkit for reservoir and production engineers. Traditionally, sensing with fiber optic technology in the form of distributed temperature sensing (DTS) or distributed acoustic sensing (DAS), and most recently distributed strain sensing (DSS) and distributed chemical sensing (DCS), were done with the fiber being permanently clamped either behind the casing or production tubing. Clamping the fiber behind tubing or casing is sometimes beleaguered with operational challenges that often lead to rendering the fiber partially damaged or inoperable. The emergence of the composite carbon-rod (CR) system that can be easily deployed in and out of a well, similarly to wireline logging, has made it possible to sense any well without prior fiber-optic installation.

In this paper, we present the lessons learned from the first well where we deployed in-well fiber-optic DAS/DTS. The DAS/DTS sensing was done in a few vertical oil producer wells and water injector wells without prior fiber-optic installation. The key objectives of the tests were to (1) investigate any well integrity across the entire length of each well, (2) assess production and injection flow profile across the perforations and behind casing, which hitherto was not possible with conventional production logging tool (PLT) tool, and (3) investigate the possibility of using the combination of distributed acoustic survey and distributed temperature survey for quantitative production flow analysis.

This paper reviews the complete design and implementation of the in-well fiber-optic deployment, field operational issues, analyses, and interpretation of the sensing results. The combination of DAS/DTS data showed no well integrity related issues. The sensing data surprisingly pinpointed a few geological features such as cooling shallow aquifers that hitherto had not been noticed. The combination of different pulse widths during shut-in and production/injection cycles helped to refine the resolution of the flow profile from the production and injection zones.