bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Limits of Fluid Flow in Propped Fractures- the Disparity Between Effective Flowing and Created Fracture Lengths
Authors: Barree R.D. , Duenckel R.J. , Hlidek B.T. 
Published: January 2019

Abstract
Post hydraulic fracture diagnostics often leads to an estimation of effective fracture lengths that are substantially shorter that the created length. (Ibrahim et al. 2017, Barree et al. 2003) This gives rise to questioning validity of the diagnostics or concerns regarding execution of the fracture stimulation itself. The objective of the paper is to show that short effective lengths are understood and predictable in the context of the physics of flow in propped fractures. Extensive laboratory testing of a broad range of proppants under a wide range of conditions has led to a databased and detailed understanding of pressure drop in a propped fracture as a function of fluid flow. The pressure drop in turn will dictate inflow from the reservoir at any point along the fracture. This interaction of pressure drop in the fracture and reservoir inflow will in turn dictate the flowing length of the fracture. Testing has demonstrated and it is well understood that the conductivity of a proppant under downhole conditions in a propped fracture is significantly less than that measured in the lab under ideal conditions of single phase Darcy flow at 2 lbm/ft2 loading. (Duenckel et al. 2017) This results from the combined effects of low proppant concentrations, frac fluid damage, multiphase flow and non-Darcy flow as well as other damage mechanisms. The paper will demonstrate that the pressure loss in the fracture resulting from the combined effects of these damage mechanisms quickly consumes the available energy to the point that the viscous forces are less than the capillary and gravity forces in the fracture, limiting further flowing length. In very low permeability reservoirs inflow from the reservoir quickly becomes insufficient to overcome gravity and capillary forces. The paper will also address the following question: if effective lengths are very short of what benefit is pumping large volumes of proppant? Further, how does one explain apparent field evidence for long fracture lengths (e.g. pressure communication) if indeed the effective length is much shorter? The paper will show how effective fracture lengths are not dependent on propped fracture properties alone. Given the limited effective conductivity resulting from a combination of damage mechanisms, the interaction of the propped fracture conductivity and reservoir inflow dictate effective fracture lengths. The resulting effective lengths are expected to be much shorter than the created lengths.
Improving Hydraulic Fracturing Performance and Interpreting Fracture Geometry Based on Drilling Measurements
Authors: Downie Robert , Daves Dusty 
Published: January 2019

Abstract
It is a well-established principle that rock properties affect fracture geometry. This paper investigates the relationships between fracture responses observed during completion operations and rock properties that are obtained during the drilling of a well. It will also attempt to quantify the benefits of designing completions based on these rock properties.
Four pairs of wells adjacent to one another are included the study. Each pair of wells includes one well with a completion design based on the operator's baseline guidelines, and one well with the perforation depths and stage boundaries selected from rock strength information derived from drilling data. The fracture treatment pressure responses are correlated to the rock properties, and the two completion methodologies are compared to determine whether there is an operational or production benefit to this completion methodology.
The results of the study show a clear and distinctive difference between treatment responses in wells whose completions are based upon drilling-derived rock properties, and those that did not. The most striking of these differences is that instantaneous shut-in pressures were higher in wells where completion stages and perforation depths were selected based on rock properties, without corresponding increases in average treatment pressures. This is likely an indication of improved fracture containment (higher net pressures) which would be expected with an equitable fluid distribution among perforation clusters. Further to this, the analysis allowed for the identification of rock parameters associated with increased risk of excessive height growth which is independent of the completion methodology used. Production comparisons will be included to support the findings.
The result of this work is a clear path forward to improving future wells by understanding how rock properties and completion design are related to fracture height growth. This allows for a re-evaluation of future drilling targets and the modification of treatment designs to maintain the maximum amount of fracture energy within the target zone. It will also help to provide further evidence that completions can be improved through the optimized placements of stage boundaries and perforation clusters.
This paper will present a new analytical workflow that combines the use of drilling-derived rock properties and fracture treatment responses to gain important insights and drive future decisions for both the drilling and completion processes.
Apparent Toughness Anisotropy Induced by Roughness of in Situ Stress: A Mechanism that Hinders Vertical Growth of Hydraulic Fractures and Its Simplified Modeling
Authors: Fu Pengcheng , Huang Jixiang , Settgast Randolph R. , Morris Joseph P. , Ryerson Frederick J. 
Published: January 2019

Abstract
A hydraulic fracture's height growth is known to be affected by many factors that are related to the layered structure of sedimentary rocks. While these factors are often used to qualitatively explain why hydraulic fractures usually have well-bounded height growth, most of them cannot be directly and quantitatively characterized for a given reservoir to enable a priori prediction of fracture height growth. In this work, we study the role of the "roughness" of in situ stress profiles, namely alternating low- and high-stress among rock layers, in determining the tendency of a hydraulic fracture to propagate horizontally versus vertically. We found that a hydraulic fracture propagates horizontally in low-stress layers ahead of neighboring high-stress layers. Under such a configuration, a fracture mechanics principle dictates that the net pressure required for horizontal growth of high-stress layers within the current fracture height is significantly lower than that required for additional vertical growth across rock layers. Without explicit consideration of the rough stress profile, the system behaves as if the rock is tougher against vertical propagation than it is against horizontal fracture propagation. We developed a simple relationship between the apparent differential rock toughness and characteristics of the stress roughness that induce equivalent overall fracture shapes. This relationship enables existing hydraulic fracture models to represent the effects of rough in situ stress on fracture growth without directly representing the fine-resolution rough stress profiles.
Empirical Links Between Sub-Surface Drivers and Engineering Levers for Hydraulic Fracture Treatments and the Implications for Well Performance
Authors: Stephenson Ben , Bai Taixu , Huckabee Paul , Tolle John , Li Ruijian , MacDonald Jeff , Acosta Luis 
Published: January 2019

Abstract
Does the sub-surface drive completion design or is the rock less of a concern with industry trends to higher proppant-, fluid- and stage-intensities? To address this challenge it was first necessary to understand; 1) how the sub-surface could potentially influence completion and stimulation design, 2) what are the available engineering levers and moreover, 3) whether well performance has actually been impacted by tailoring completions in different plays from specific case-studies.
Although there is a multitude of published field examples of how completion design changes have driven value, clarity around the inter-connectedness with sub-surface variability, either between plays or within a play, is commonly missing. New templates have been developed that describe the conceptual links between the nine key 'Sub-surface Drivers' for hydraulic fracturing and their associated engineering Levers categorized by well-, fluid-, proppant- and stage-design. These templates are a compilation of extensive empirical observations from both operations and field performance reviews incorporating thousands of wells across North America, supported with learnings from geomechanical theory and modeling.
The nine Sub-surface Drivers that influence completion design and control the access to hydrocarbons are, 1) mobility, 2) reservoir pressure, 3) gross thickness, 4) layering heterogeneity, 5) rock stiffness, 6) natural fractures, 7) stress anisotropy, 8) risk of fraccing faults and, 9) risk of fraccing out of zone. Drivers 1-7 govern the connectivity, whereas 8 and 9 influence stimulation ineffectiveness. It is proposed that there are approximately fifteen primary engineering Levers related to these nine Drivers, which have been shown to have a measurable impact on completion effectiveness and/or production.
Case studies illustrate that the Sub-surface Drivers play a significant role in most plays, but they are not all relevant in every play. The challenge is to acknowledge the variability, or lack of, and pursue completion design optimization goals, while managing the variance in the well performance range.
Whereas industry trends of increasing completions intensity have delivered more value in many plays, the Sub-surface Drivers concept have primarily proven useful to mitigate against poor wells in development and explain exploration failures. By developing a systematic set of templates for Drivers and their respective levers, learnings from other operators can be high-graded through the formulation of connectivity analogues with the goal of showing where changes in completion design may be more, or less applicable.
Nine Plus Years of Production Show Value of Proper Design in Oil Window of Barnett Shale
Authors: Ely John W. , Harper Jon , Nieto Esteban N. , Kousparis Dimitrios , Kousparis Andrew , Crumrine Curt 
Published: January 2019

Abstract
The Northern extension of the "COMBO" Barnett Shale is located primarily in Montague, Cooke, and Clay counties in the North Texas region. This play is unique in that the shale in the area is very rich in total organic content (TOC) and contains a relatively high concentration of carbonates throughout. This extension is primarily inside the the oil window of the Barnett, rather than predominately within the more gas-rich region, which dominates the rest of the shale's development throughout North Texas (See Figure 1). Some of the earliest technological enhancements in oil production from shale occurred in the COMBO Barnett play, prior to the expanse and relative boom of the Eagle ford shale, and many other successful unconventional oil shale plays throughout the industry, both domestic and international. The Barnett in this area is typically quite thick, with sections from 300-700 feet. In some cases, naturally occurring fractures are fairly evident and can be identified through the use of image logging, prior to the completion phase of a well. Some areas may exhibit limited natural fractures, but have very brittle rock. Vertical completions were dominate during the early development of the Barnett, constituting a vast majority of oil and gas wells in production within the region. In fact, measureable time in production for the wells in the area indicated that properly completed vertical wells had respectable economics, which were later, at times, enhanced with horizontal drilling and multi-stage frac completions and re-completions.
Simplification and Simulation of Fracture Network Using Fast Marching Method and Spectral Clustering for Embedded Discrete Fracture Model
Authors: Xue Xu , Rey Alvaro , Muron Pierre , Dufour Gaelle , Wen Xian-Huan 
Published: January 2019

Abstract
Embedded Discrete-Fracture Model (EDFM) is designed to accurately represent realistic hydraulic fracture network (HFN) and provide efficient performance predictions by honoring the fracture topology. Due to the complexity of HFN, the EDFM grid may be computationally inefficient, particularly for field-scale applications with millions of fracture cells. This paper aims at incorporating the Fast Marching Method (FMM) and spectral clustering for fast HFN analysis, simplification and simulation under the framework of EDFM.
HFNs are first generated using a commercial hydraulic fracture simulator. The FMM is used to solve the pressure front propagation using the fracture graph and subsequently the ‘diffusive time of flight’, well and completion index are calculated. The results are used as pre-conditions to split the fracture graph into connected components, which are subsequently partitioned using spectral clustering. The resulting clusters are used for fracture simplification resulting in a significantly lower number of fracture elements for flow simulation. To demonstrate the feasibility of the workflow, we use the Multi-Well Pad pilot model, which is characterized by a complex HFN and a high-resolution matrix system. We investigate the relationship between matrix resolution (characterized by the matrix-fracture size of the reservoir cells) and the ratio of oil and gas production on the field. Our investigation provides an alternative approach to explain the very large Gas Oil Ratio (GOR) reported for this type of reservoirs. The required levels of refinement to correctly represent the observed GOR presents an opportunity to test the efficiency and accuracy of our proposed workflow for HFN simplification. We use the results of the FMM applied to the high-resolution models to find an optimal spectral fracture clustering. The results show that the proposed workflow can achieve massive fracture cells aggregation (with only 1% of the original fracture cell number) while maintaining the accuracy.
This is the first study for analysis, simplification, and simulation of HFN for EDFM using a field scale model. The main contributions are: (i) honor the topology of complex HFNs in EDFM and is able to represent the complex physics observed in the oil and gas shale reservoirs, (ii) HFNs diagnosis without simulation, and (iii) massive fracture aggregation with an error below 5 percent, and speed-up higher than 16 times of the fine scale model.
CounterProp, Finally Adding the Correct Proppant in the Proper Size and Proper Sequence in Slick Water Treatments
Authors: Ely John W , Harper Jon , Nieto Esteban N. , Semmelbeck Mark 
Published: January 2019

Abstract
As long as Stokes law or low viscosity Newtonian fluids have been available, common knowledge within the industry has been that whenever these fluids are utilized during the hydraulic fracturing process, very rapid settling of any conventional proppant occurs. Over the years, there have been occasional jobs pumped where the larger sized proppant was the initial proppant pumped, followed by the smaller meshed sand, ceramic or bauxite materials. Little attention was paid to this differing sort of treatment, due to the belief in piston like displacement of proppant regardless of fluid type. Commonly curable resin-coated sand was always pumped in the very last slurry stage of a fracturing treatment, in the common hopes of controlling any potential sand production from the near wellbore area when operations were concluded and flow back operations were initiated to bring the well on line. In reality, with typical over flush volumes, any resin-coated sand pumped during a slick water treatment will travel far away from the wellbore.
Spatial variability and temporal dynamics of cyanobacteria blooms and water quality parameters in Missisquoi Bay (Lake Champlain)
Authors: Melendez-Pastor I. , Isenstein E. M. , Navarro-Pedreño J. , Park M-H. 
Published: January 2019

AbstractCyanobacteria bloom events have been associated with eutrophication processes, along with hydrologic and climate factors. Missisquoi Bay is a portion of Lake Champlain (USA–Canada) that is highly eutrophic and prone to cyanobacteria blooms and cyanotoxins. This study assessed the spatial–temporal influence of nutrients, turbidity and temperature in cyanobacteria distributions during a bloom event in the summer of 2006. Correlations, generalized linear models (GLMs), geostatistics and local indications of spatial association (LISA) autocorrelation analysis tested the influence of nutrient and non-nutrient explanatory variables in cyanobacteria biovolume. Total phosphorus exhibited a high direct correlation with cyanobacteria biovolume. The best performing GLMs included total phosphorus, total nitrogen, Secchi depth (as turbidity) and temperature as explanatory variables of cyanobacteria biovolume. Variogram analysis of those variables resulted in a better understanding of the underlying spatial variation process of the cyanobacteria bloom event. The LISA test revealed a moderate but stable autocorrelation between cyanobacteria biovolume and total phosphorus from 180 to 1,000 m of weight distance, suggesting the possibility of up-scaling the current results to coarse-resolution satellite imagery for more frequent monitoring of bloom events. The LISA test also revealed the spatial–temporal dynamic (movement of cyanobacteria scums) of high cyanobacteria blooms with high total phosphorus concentration.
Use of broken brick to enhance the removal of nutrients in subsurface flow constructed wetlands receiving hospital wastewater
Authors: Dires Simachew , Birhanu Tarekegn , Ambelu Argaw 
Published: January 2019

Abstract
Eight horizontal subsurface flow pilot scale artificial wetlands were constructed to evaluate the effectiveness of broken brick to remove nutrients from hospital wastewater. The average total suspended solids (TSS), 5-day biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), NH4-N, NO3-N, and phosphate percent removal efficiency of constructed wetlands were, respectively, 93.2%, 90.4%, 83.7%, 64%, 64.3%, 52.1% and 56.1% in the dry season and 89.7%, 85.8%, 82.9%, 66%, 62.7%, 56.1% and 59.5% in the rainy season. Broken brick bed wetlands provide better removal efficiency of TKN, ammonia, nitrate, and phosphate with an average removal rate of 73%, 71.3%, 79.6% and 77.1% in the dry season and 74.7%, 70.7%, 70.9% and 73.6% in the rainy season, respectively, and it provides better adsorption sites for ammonium, nitrate, and phosphate. Typha with the broken brick bed significantly improved (P &lt; 0.05) the treatment performance of the constructed wetland systems for the removal of ammonia, nitrate, and phosphate. The seasonal variation could not significantly influence the removal of all the pollutants, but better performance of nitrate and phosphate was achieved in a dry season. Use of locally available broken brick as a substrate media can increase the nutrient removal efficiency of wetlands at a cheaper cost when applied in full scale constructed wetlands.
Modified xanthan gum for crystal violet uptake: kinetic, isotherm, and thermodynamic behaviors
Authors: Zheng Meixia , Lian Fengli , Zhu Yujing , Liu Bo , Chen Zheng , Zhang Yi , Zheng Baodong , Zhang Longtao 
Published: January 2019

Abstract
Modified xanthan gum (XG-AM-TTE) was employed as an adsorbent to study the adsorption behavior, thermodynamics and kinetics of crystal violet (CV) from an aqueous solution. Fourier transform infrared spectroscopy analysis indicates that the functional groups present in the adsorbent, such as carboxyl, ester and hydroxyl groups, are included on the external surface of the material, and these groups are potential active sites for interaction with CV. According to X-ray diffraction results, the structure of XG-AM-TTE after CV adsorption became more disordered, and the microstructure change is an indication of effective adsorption of CV to the surface, with CV becoming remarkably dispersed in the adsorbent according to the scanning electron microscopy observations. The adsorption kinetics and adsorption equilibrium were best described by the pseudo-second-order model and Freundlich isotherms, respectively. The thermodynamic parameters, as the Gibbs-free energy (ΔG), enthalpy (ΔH) and entropy (ΔS), indicated that the adsorption is a spontaneous, endothermic and entropy increase process. The maximum adsorption capacity of XG-AM-TTE was 183 ± 12 mg/g, suggesting that XG-AM-TTE is an efficient adsorbent.
El Síndrome de Burnout : un riesgo permanente en el trabajo de enfermería
Authors: Balseiro Almario Lasty 
Published: January 2019

Los psicólogos hablan del Síndrome de Burnout desde los años 70. Este hace referencia al desgaste profesional y estrés producido por el desgaste que se da entre las expectativas de cada profesional y la realidad misma del trabajo. Cuando no se consiguen los resultados y objetivos propuestos, a pesar de haberse intentado por todos los medios y de acuerdo con sus posibilidades, hace su aparición el sentimiento que puede desencadenar el &quot;estar quemado&quot; o síndrome de Burnout. de El Burnot se trata de un Síndrome clínico descrito en 1974 por Freudemberg, Psiquiatra que trabajaba en una clínica para toxicómanos en Nueva York. Observó que al año de trabajar, la mayoría de los voluntarios sufría una progresiva pérdida de energía, hasta llegar al agotamiento, síntomas de ansiedad y de depresión, así como desmotivación en su trabajo y agresividad con los pacientes.
Cuando se trabaja sin ilusión, e incluso en desagrado, con frecuencia se debe a la aparición del síndrome de Burnout o síndrome del quemado. Este mal afecta, sobre todo a aquellos cuyo trabajo tiene una repercusión directa sobre la vida de otras personas Profesores, médicos o Enfermeras son algunos de los profesionales que padecen este tipo de síndrome
Evaluación de la docencia en enfermería desde la opinión de los actores de la educación.
Authors: Ponce Gómez Gandhy , González Juárez Liliana , Bernal Becerril Martha Lilia 
Published: January 2019

La práctica docente como praxis social, debe trascender de dimensión para reconocer la relación entre personas, mediar un saber colectivo culturalmente organizado e intrínsecamente conectado con un conjunto de valores personales y sociales implicando su transformación.
En Enfermería la evaluación docente cobra relevancia, no solo por cuantificar un actuar en lo didáctico, sino de indagar la dimensión personal, interpersonal, social y de valores que se forma en estudiantes; porque se trata de transformadores sociales que serán responsables del cuidado a la salud de los individuos.
Metodología: estudio de tipo cuantitativo correlacional, en alumnos y docentes de una escuela de Enfermería de nivel superior en el DF ("n" de docentes = 23 Y “n" de alumnos = 250).
Resultados: Los profesores de 2° y 8° semestre son evaluados más alto con respecto al índice general de desempeño; la dimensión didáctica es la evaluada con medias más bajas en general, y que aún con una relación relativamente baja son los docentes de menor edad quienes reciben evaluaciones más favorables.
Transitando desde la autovaloración y la perspectiva del alumno hacia el descubrimiento de la riqueza y complejidad de la docencia se pretende transformar reflexiva y críticamente la importante tarea educativa.