bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Horizontal Stress Models and Biot Poro-Elasticity on Predicted Fracture Geometry
Authors: Narasimhan Santhosh , Shaikh Hamza , Gray James K. , Cherian Bilu V. , Olaoye Olubiyi , Rifai Rafif , Kublik Kristina , McCleary Matt , Fluckiger Samuel D. , Sharf-Aldin Munir 
Published: January 2016

Abstract
This paper covers the methodology to derive all geomechanical properties (Young's modulus, Poisson's ratio and vertical/horizontal variable Biot constants as a function of rock type) for 13 different stress models. Minimum horizontal stress (Sh) is a key parameter controlling fracture height growth during hydraulic fracturing simulation. Assuming a homogeneous formation (rock property Horizontal:Vertical = 1.0) or poorly derived inputs for the anisotropy model can lead to incorrect fracture geometry. A major assumption made using the various stress models is the Biot poro-elastic constant. Many default models assume a Biot poro-elastic constant of one, which is valid for coarse grained conventional reservoirs where porosity is greater than 20%. Most of the reservoirs stimulated with hydraulic fracturing today do not fall in that porosity range, therefore an alternative derivation for the Biot poro-elasticity and its variability requires additional discussion.
Models derived and compared with their associated uncertainties in this paper include: Ben Eaton – isotropic, anisotropic, dynamic and modified with correction factor; default from auto log calibration; Vernik, Jaeger & Cook; Hubbert & Willis; Thiercelin – MC envelope and stiffness tensors (Cij); Segall & Penebaker. The geomechanical properties from the different stress models noted above were inserted into a gridded fracturing simulator. The outputs were compared to actual job and calibration data for; minimum horizontal stress, end of job net pressure and fracture geometry for each of the models.
When comparing fracture geometries from each stress model against calibration data it is apparent that the chosen stress model will have a substantial influence on the result. This illustrates the importance of choosing the correct stress model for fracture simulations.
Integration of Dynamic Microseismic Data with a True 3D Modeling of Hydraulic Fracture Propagation in Vaca Muerta Shale
Authors: Haddad Mahdi , Du Jing , Vidal-Gilbert Sandrine 
Published: January 2016

Abstract
Microseismic mapping during hydraulic fracturing processes in Vaca Muerta (VM) Shale in Argentina shows a group of microseismic events happening at shallower depth and at later injection time, and they clearly deviate from the growing planar hydraulic fracture. This spatial and temporal behavior of these shallow microseismic events incurs some questions regarding the nature of these events and their connectivity to the hydraulic fracture. To answer these questions, in this paper, we investigate these phenomena using a true 3D fracture propagation modeling tool along with statistical analysis on the properties of microseismic events.
First, we propose a novel technique in Abaqus incorporating fracture intersections in true 3D hydraulic fracture propagation simulations based on pore-pressure Cohesive Zone Model (CZM). The simulations fully couple slit flow in fracture with poro-elasticity in matrix and continuum-based leak-off on the fracture walls, and honor the fracture tip effects in quasi-brittle shale. Using this model, we quantify vertical natural fracture activation depending on reservoir depth, fracturing fluid viscosity, mechanical properties of the natural fracture cohesive layer, natural fracture conductivity, and horizontal stress contrast. The modeling results demonstrate this natural fracture activation in coincidence with the hydraulic fracture growth complexities at the intersection such as height throttling, sharp aperture reduction after the intersection, and multi-branching at various heights and directions.
Finally, we investigate the hydraulic fracture intersection with a natural fracture in the multi-layer VM Shale. We infer the natural fracture location and orientation from the microseismic events map and Formation MicroImager log in a nearby vertical well, respectively. We integrate the other field information such as mechanical, geological, and operational data to provide a realistic hydraulic fracturing simulation in the presence of a natural fracture. Our 3D fracturing simulations equipped by the new fracture intersection model rigorously simulate the growth of a realistic hydraulic connection path toward the natural fracture at shallower depths, which was in agreement with our microseismic observations.
Case Histories in Cost-Efficient Re-Fracturing of Horizontal Wells
Authors: Matt J. D. 
Published: January 2016

Abstract
Objectives/Scope: To identify cost-efficient re-fracturing methods in horizontal wells. We provide a case history of cost-efficient methods in the Eagle Ford, Permian, and Bakken by analyzing over 1000 re-fractured wells.
Methods, Procedures, Process: We have collected data on over 1000 re-fractured wells in our analysis. We incorporate the frac chemistry (slickwater vs gelled frac etc.) for each of the fracture treatments in this analysis. We have also analyzed the production improvements gained from the re-frac. We analyze the individual wells production prior to re-frac and the improved production after the re-frac.
Results, Observations, Conclusions: After standardizing as many variables as possible we have found that slickwater re-fracs with large amount of proppant have provided the highest production increase in terms of absolute production. Initial analysis shows slight differences between the three regions involved in this case study.
Novel/Additive Information: We are not aware of any other large scale public study done on this same topic. We hope that our case study based approach will provide a launching point for future work done on re-fracturing.
Improving Hydrocarbon Recovery in Sliding Sleeve Completions Utilizing Diverters in the Wattenberg Field
Authors: Fry Jessica , Roach Erik , Kreyche Brett , Yenne Travis , Geoffrey Gullickson , Jespersen Matt 
Published: January 2016

Abstract
The use of sliding sleeve completions has been widely recognized as an efficient and effective means of completing horizontal laterals in unconventional reservoirs for several years. Recently, the focus shifted to optimizing stage spacing and number of stages per lateral. Even with such optimization the entire lateral was not effectively stimulated and drained. In this 15-well pad pilot study, we focused not only on optimizing the design but also on achieving uniform drainage along the lateral.
A treatment design using biodegradable diverters to split each stage into two proppant cycles was recommended. The diverter was used on 5 of the 14 wells completed. Total proppant and fluid volumes, as well as proppant and fluid types, were the same on conventionally-treated and diverter-treated wells. Average treating rates and operation procedures were also similar over the entire study group. After stimulation, the wells were turned on with identical chokes and produced similarly. Daily oil, gas, and water rates were monitored over eight months and compared.
Production was normalized on a cumulative barrel of oil equivalent (BOE) per foot of lateral basis. Results showed the diverter-treated wells produced 28% more than the conventionally-treated wells at eight months, with the margin increasing. Although all wells were completed on the same pad, at the subsurface level they covered over two miles of structurally variable formation. A multivariate analysis incorporating subsurface, drilling, completion, and production properties was also conducted to determine the most important parameters contributing to hydrocarbon recovery.
This study shows that diverters can be incorporated in sliding sleeve completions to lower the total cost per BOE and increase hydrocarbon recovery. This diverter design and technology continues to be implemented in projects with success and positive impacts on production.
Remote Imaging of Proppants in Hydraulic Fracture Networks Using Electromagnetic Methods: Results of Small-Scale Field Experiments
Authors: LaBrecque Douglas , Brigham Russell , Denison Jessica , Murdoch Lawrence , Slack William , Liu Qing Huo , Fang Yuan , Dai Junwen , Hu Yunyun , Yu Zhiru , Kleinhammes Alfred , Doyle Patrick , Wu Yue , Ahmadian Mohsen 
Published: January 2016

Abstract
The goal of this project is to develop techniques for monitoring hydraulic fractures in reservoirs by injecting electrically conductive, dielectric, or magnetically permeable proppants. The contrasts between the properties of the proppants and the subsurface provided the basis for imaging using geophysical methods. The initial experiments focused on a series of small, shallow fractures; however, the goal of the project is to develop methods applicable to oil-field fractures.
The project began by screening different proppant types using laboratory and numerical analyses that have been ongoing by researchers at the Advanced Energy Consortium (AEC). This work identified Loresco coke breeze and steel shot as materials that could create significant electrical or magnetic contrasts with most geological formations. These proppants were tested by creating hydraulic fractures in a shallow field setting consisting of highly weathered residual saprolite near Clemson University in western South Carolina. Six hydraulic fractures were created in highly monitored cells by injecting the contrasting proppants at a depth of approximately 1.5 m. This created sub-horizontal fractures filled with proppant approximately 10 mm thick and extending 3 to 5 m in maximum dimension.
Each cell had a dense array of electrodes and magnetic sensors on the surface, as well as four shallow vertical electrode arrays that were used to obtain data before and after hydraulic fracturing. Net vertical displacement, cores and trenching were used to characterize the fracture geometries.
Hydraulic fracture geometries were estimated by inverting pre- and post-injection geophysical data using various codes. Data from cores and excavation show that the hydraulic fractures formed a saucer-shape with a preferred propagation in the horizontal direction. The geophysical inversions generated images with remarkably similar form, size, and location to the ground truth from direct observation. Displacement and tilt data appear promising as a constraint on fracture geometry.
Interwell Hydraulic Fracture Interaction Between Multistage Stimulated Wells and a Multi Zone Slant Open Hole Observation Well Placed in the Canadian Horn River Basin
Authors: Pyecroft James , Lehmann Jurgen , Petr Christopher , Lypkie Kevin , Purdy Ivan , Zafar Hammad , Hiller Chelsey , Meeks David 
Published: January 2016

Abstract
This paper presents well construction details and pressure responses for a slant well in a dry gas shale resource in northern British Columbia, Canada. We will present the drilling and completions plan for a Multi-Stage Hydraulic Fracturing (MSHF) campaign on a ten well half pad including consequences of an aggressive fluid environment. Horn River shale gas development involves Multi-well MSHF horizontal wells from a single surface pad location. The wells are treated sequentially from toe to heel of the horizontal section, alternating between wells. Strategic placement of an Open Hole (OH) slant well equipped with slotted liner, tubing, and pressure data recorders will be presented. Pressure responses during the MSHF campaign will be presented and reviewed against calibrated closure pressure data from Diagnostic Fracture Injection Test (DFIT) data and end of job instantaneous shut-in pressures (ISIP).
The initial concept of drilling an OH well placed between MSHF wells was to evaluate the fracture system between stimulated wells and to test whether an unstimulated open hole well placed between stimulated wells can economically produce gas. Other objectives were to provide an Oil Based drilling Mud (OBM) free wellbore that would enable water-based imaging logs. Water-based logs have enhanced ability to identify and map natural fractures. Initial logs would evaluate the natural fractures and subsequent post-completion logs would evaluate the hydraulic fracture transiting the shale resource rock to the OH well. Knowledge of how pre-existing natural fracture networks react to the hydraulic fracture process along with pressure response data recorded from all wells on the pad would be used to provide geoscientists and engineers the means to optimize stimulation programs for horizontal wells and wellbore placement within the various resource reservoirs in the Horn River Basin.
This paper will discuss the compromises that were made to the initial conceptual model that maximized learnings from the slant OH wellbore, and how the well was unexpectedly lost. Pressure interference data for future hydraulic fracturing models will be provided along with methods to describe how hydraulic fractures from nearby wells transect a well and interact with various reservoirs exposed within the OH segment of a slant wellbore.
Determining the Effectiveness of Isolation Techniques Using Completion Diagnostics and Production Analysis
Authors: Senters C. W. , Snyder D. J. , Warren M. N. , Leonard R. S. , Woodroof R. A. 
Published: January 2016

Abstract
The development of unconventional resources in North America has led to the implementation of a variety of drilling and hydraulic fracturing techniques. This paper reviews completion diagnostic data from over 50 wells in the Anadarko and Williston Basins that were evaluated by a multidisciplinary team. Production analyses were conducted in conjunction with the diagnostic data to further qualify the effectiveness of different completion practices.
Stimulation diagnostics including proppant tracers, microseismic data, and permanently installed fiber optic sensors are available to assist with identifying fracture growth both within and outside of a targeted interval. Wells in this study will utilize proppant tracers for the evaluation of stage coverage and isolation effectiveness.
This paper specifically focuses on isolation techniques used during hydraulic fracturing of uncemented multistage horizontal wells, including swellable packers, and single and dual-element hydro-mechanical packers. Stimulation coverage and zonal containment for these isolation techniques were evaluated, and the results demonstrate how different isolation techniques can affect production.
This study shows how operating conditions may also affect the integrity of certain isolation techniques, as results for the most effective isolation techniques vary by basin. These operating variations, among others, are examined in this paper as a possible contributing factor for the loss of annular isolation and corresponding production decreases.
Isolation techniques are often implemented in drilling and completion programs with insufficient data or field trials. Most of these decisions are made based on perceived cost optimization rather than the overall completion effectiveness and performance of the well. This study is the first of its kind using a macroscopic analysis of completion diagnostics and production data over a large data set for the evaluation of isolation techniques.
Pediatric intracranial gunshot wounds: the Memphis experience
Authors: DeCuypere Michael , Muhlbauer Michael S. , Boop Frederick A. , Klimo Paul 
Published: January 2016

OBJECTIVE
Penetrating brain injury in civilians is much less common than blunt brain injury but is more severe overall. Gunshot wounds (GSWs) cause high morbidity and mortality related to penetrating brain injury; however, there are few reports on the management and outcome of intracranial GSWs in children. The goals of this study were to identify clinical and radiological factors predictive for death in children and to externally validate a recently proposed pediatric prognostic scale.

METHODS
The authors conducted a retrospective review of penetrating, isolated GSWs sustained in children whose ages ranged from birth to 18 years and who were treated at 2 major metropolitan Level 1 trauma centers from 1996 through 2013. Several standard clinical, laboratory, and radiological factors were analyzed for their ability to predict death in these patients. The authors then applied the St. Louis Scale for Pediatric Gunshot Wounds to the Head, a scoring algorithm that was designed to provide rapid prognostic information for emergency management decisions. The scale's sensitivity, specificity, and positive and negative predictability were determined, with death as the primary outcome.

RESULTS
Seventy-one children (57 male, 14 female) had a mean age of 14 years (range 19 months to 18 years). Overall mortality among these children was 47.9%, with 81% of survivors attaining a favorable clinical outcome (Glasgow Outcome Scale score ≥ 4). A number of predictors of mortality were identified (all p < 0.05): 1) bilateral fixed pupils; 2) deep nuclear injury; 3) transventricular projectile trajectory; 4) bihemispheric injury; 5) injury to ≥ 3 lobes; 6) systolic blood pressure < 100 mm Hg; 7) anemia (hematocrit < 30%); 8) Glasgow Coma Scale score ≤ 5; and 9) a blood base deficit < −5 mEq/L. Patient age, when converted to a categorical variable (0–9 or 10–18 years), was not predictive. Based on data from the 71 patients in this study, the positive predictive value of the St. Louis scale in predicting death (score ≥ 5) was 78%.

CONCLUSIONS
This series of pediatric cranial GSWs underscores the importance of the initial clinical exam and CT studies along with adequate resuscitation to make the appropriate management decision(s). Based on our population, the St. Louis Scale seems to be more useful as a predictor of who will survive than who will succumb to their injury.
ON THE CONNECTION BETWEEN MICROBURSTS AND NONLINEAR ELECTRONIC STRUCTURES IN PLANETARY RADIATION BELTS
Authors: Osmane Adnane , III Lynn B. Wilson , Blum Lauren , Pulkkinen Tuija I. 
Published: January 2016

ABSTRACT
Using a dynamical-system approach, we have investigated the efficiency of large-amplitude whistler waves for causing microburst precipitation in planetary radiation belts by modeling the microburst energy and particle fluxes produced as a result of nonlinear wave–particle interactions. We show that wave parameters, consistent with large-amplitude oblique whistlers, can commonly generate microbursts of electrons with hundreds of keV-energies as a result of Landau trapping. Relativistic microbursts (>1 MeV) can also be generated by a similar mechanism, but require waves with large propagation angles

and phase-speeds

. Using our result for precipitating density and energy fluxes, we argue that holes in the distribution function of electrons near the magnetic mirror point can result in the generation of double layers and electron solitary holes consistent in scales (of the order of Debye lengths) to nonlinear structures observed in the radiation belts by the Van Allen Probes. Our results indicate a relationship between nonlinear electrostatic and electromagnetic structures in the dynamics of planetary radiation belts and their role in the cyclical production of energetic electrons (

keV) on kinetic timescales, which is much faster than previously inferred.
ERRATIC FLARING OF BL LAC IN 2012–2013: MULTIWAVELENGTH OBSERVATIONS
Authors: Wehrle Ann E. , Grupe Dirk , Jorstad Svetlana G. , Marscher Alan P. , Gurwell Mark , Baloković Mislav , Hovatta Talvikki , Madejski Grzegorz M. , Harrison Fiona H. , Stern Daniel 
Published: January 2016

ABSTRACT
BL Lac, the eponymous blazar, flared to historically high levels at millimeter, infrared, X-ray, and gamma-ray wavelengths in 2012. We present observations made with Herschel, Swift, NuSTAR, Fermi, the Submillimeter Array, CARMA, and the VLBA in 2012–2013, including three months with nearly daily sampling at several wavebands. We have also conducted an intensive campaign of 30 hr with every-orbit observations by Swift and NuSTAR, accompanied by Herschel, and Fermi observations. The source was highly variable at all bands. Time lags, correlations between bands, and the changing shapes of the spectral energy distributions can be explained by synchrotron radiation and inverse Compton emission from nonthermal seed photons originating from within the jet. The passage of four new superluminal very long baseline interferometry knots through the core and two stationary knots about 4 pc downstream accompanied the high flaring in 2012–2013. The seed photons for inverse Compton scattering may arise from the stationary knots and from a Mach disk near the core where relatively slow-moving plasma generates intense nonthermal radiation. The 95 spectral energy distributions obtained on consecutive days form the most densely sampled, broad wavelength coverage for any blazar. The observed spectral energy distributions and multi-waveband light curves are similar to simulated spectral energy distributions and light curves generated with a model in which turbulent plasma crosses a conical shock with a Mach disk.
THE CONVERGENCE OF PARTICLE-IN-CELL SCHEMES FOR COSMOLOGICAL DARK MATTER SIMULATIONS
Authors: Myers Andrew , Colella Phillip , Van Straalen Brian 
Published: January 2016

ABSTRACT
Particle methods are a ubiquitous tool for solving the Vlasov–Poisson equation in comoving coordinates, which is used to model the gravitational evolution of dark matter (DM) in an expanding universe. However, these methods are known to produce poor results on idealized test problems, particularly at late times, after the particle trajectories have crossed. To investigate this, we have performed a series of one- and two-dimensional “Zel’dovich pancake” calculations using the popular particle-in-cell (PIC) method. We find that PIC can indeed converge on these problems provided that the following modifications are made. The first modification is to regularize the singular initial distribution function by introducing a small but finite artificial velocity dispersion. This process is analogous to artificial viscosity in compressible gas dynamics, and, as with artificial viscosity, the amount of regularization can be tailored so that its effect outside of a well-defined region—in this case, the high-density caustics—is small. The second modification is the introduction of a particle remapping procedure that periodically reexpresses the DM distribution function using a new set of particles. We describe a remapping algorithm that is third-order accurate and adaptive in phase space. This procedure prevents the accumulation of numerical errors in integrating the particle trajectories from growing large enough to significantly degrade the solution. Once both of these changes are made, PIC converges at second order on the Zel’dovich pancake problem, even at late times, after many caustics have formed. Furthermore, the resulting scheme does not suffer from the unphysical, small-scale “clumping” phenomenon known to occur on the pancake problem when the perturbation wavevector is not aligned with one of the Cartesian coordinate axes.