bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Nitric Acid Concentration on Doping of Thin Film Single-walled Carbon Nanotubes for Electrode Application in Transparent, Flexible Dye Sensitized Solar Cells
Authors: Zhang Liling , Rao Manohar , Kochupurackal Jinesh , Mathews Nripan , Lam Yeng Ming , Mhaisalkar Subodh G. 
Published: February 2013

ABSTRACTA simple method is proposed for the chemical modification of carbon nanotubes (CNT) thin film counter electrodes (CE) for the replacement of fluorine-doped tin oxide (FTO) and platinum catalyst (Pt) while retaining light transparency. In order to decrease the sheet resistance, CNT thin films underwent various concentrations (≤10 M) and durations of HNO3 treatment prior to cell fabrication, and the effect on thin film properties was analyzed. P-doping was observed, and the maximum change in work function was found to be +0.35 eV with 4 M HNO3. Optimum sheet resistance reduction (50%) and work function increment were achieved after 1 h treatment with 4 M HNO3. Changes in optical transmittances for all samples were negligible (± 5%). Pristine and HNO3 treated films on plastic substrates were tested as CE in flexible bifacial dye sensitized solar cells (DSSC). Most significant improvements in conversion efficiencies were obtained when CNT on plastic substrates were pretreated with 8 M HNO3 (from 1.18% to 1.40% under roomlight, from 0.19% to 0.26% under 1 Sun).
High-temperature thermoelectric properties of W-substituted CaMnO3
Authors: Alfaruq Dimas S. , Eilertsen James , Thiel Philipp , Aguirre Myriam H , Otal Eugenio , Populoh Sascha , Yoon Songhak , Weidenkaff Anke 
Published: February 2013

AbstractThe thermoelectric properties of W-substituted CaMn1-xWxO3-δ (x = 0.01, 0.03; 0.05) samples, prepared by soft chemistry, were investigated from 300 K to 1000 K and compared to Nb-substituted CaMn0.98Nb0.02O3-δ. All compositions exhibit both an increase in absolute Seebeck coefficient and electrical resistivity with temperature. Moreover, compared to the Nb-substituted sample, the thermal conductivity of the W-substituted samples was strongly reduced. This reduction is attributed to the nearly two times greater mass of tungsten. Consequently, a ZT of 0.19 was found in CaMn0.97W0.03O3-δ at 1000 K, which was larger than ZT exhibited by the 2% Nb-doped sample.
The Team Approach to Replacing the Congenitally Missing Lateral Incisor: Restorative and Periodontal Considerations
Authors: Clem Donald S. , Hinds Kenneth F. 
Published: February 2013

Introduction: The replacement of congenitally missing maxillary lateral incisors can be a challenge from both a restorative and surgical perspective. The restorative dentist is limited in achieving esthetics by the surgical result not only by the implant position but by the surrounding periodontium of the site itself, as well as the adjacent teeth. The present case, replacing congenitally missing lateral incisors with an immediate provisional restoration, is important because it demonstrates the ideal team approach. By each clinician participating in stage I surgery, the restorative dentist and periodontist can work toward an optimal result. The combination of restorative expertise and regenerative enhancements simultaneously can result in a minimally invasive approach with fewer appointments and greater patient acceptance.Case Presentation: This case report demonstrates the restorative and surgical considerations and techniques for prefabrication of screw‐retained provisional restorations placed at the time of surgery. Surgical considerations and techniques to support the restoration position, size, and screw retention connection are also presented.Conclusions: Close communication between treatment team members is critical to achieving predictable esthetics and function for congenitally missing maxillary lateral incisors. The participation of the restorative dentist at stage I surgery is critical in demanding esthetic cases such as this. Periodontal hard and soft tissues respond well to prefabricated screw‐retained provisional restoration delivered at the time of surgery.
Self-Suspending Proppant
Authors: Mahoney R. P. , Soane D. , Kincaid K. P. , Herring M. , Snider P. M. 
Published: February 2013

Abstract
Presented here is a new approach to hydraulic fracturing, using proppants that self-suspend in water. To form these self-suspending proppants (SSP), conventional proppant particles are encapsulated with a thin layer of a high-molecular-weight hydrogel polymer, and then dried, yielding a free-flowing granular system that can be handled much like traditional proppants. Once the SSP contacts water, the hydrogel layer expands spontaneously and it forms a space-filling cushion around each granule. These SSPs were created to address the performance limitations that exist with traditional proppants. In contrast to traditional proppants, SSPs remain well suspended and evenly distributed within fracturing fluid. The new technology can be applied to a variety of proppant substrates.
Properties of the SSP arise from the hydrogel formulation used as their coating. Upon hydration in water, the hydrogel coating around the proppant particles imbibes water quickly and swells substantially, expanding the hydrodynamic radius of the polymer-enveloped solid core. In addition, any SSP particles that settle are easily resuspended upon restart of flow. The self-suspending proppant approach delivers proppants efficiently with the hydraulic fracturing fluid and results in no observable segregation/sedimentation. Conventional breakers are used to reverse the effect of the hydrogel layer, releasing the proppant into the fracture after transport.
Conventional proppants have a tendency to settle out of the carrier fluid, causing segregation during pumping. By contrast, the self-suspending proppant technology enables complete proppant suspension until deposition in the fracture. Moreover, using SSP can eliminate the need for the viscosity and suspension properties of a gel carrier entirely, thereby reducing the hydraulic pumping pressure for proppant transport. This self-suspending proppant technology offers a promising alternative to the proppant systems currently available for hydraulic fracturing applications. The major benefit of the SSP is better placement of proppant in the fracture, leading to lower water injection requirements, lower proppant usage, and improved well productivity.
Development and Use of High-TDS Recycled Produced Water for Crosslinked-Gel-Based Hydraulic Fracturing
Authors: Lebas R. , Lord P. , Luna D. , Shahan T. 
Published: February 2013

Abstract
Large quantities of high-total dissolved solids (TDS) produced water are generated during oil and gas production in Eddy County, New Mexico (more than 164 million bbl in 2011). Most of the high-saline produced water is reinjected into disposal wells at an average cost of USD 0.75 to USD 1.00 per bbl. Caused in part by the persistent drought conditions in New Mexico, beneficial use of produced water is receiving attention in the oil and gas industry. One alternative being considered is the use of produced water for hydraulic fracturing operations. Typically, wells in the Delaware basin require 40,000 to 60,000 bbl of fresh water each for hydraulic fracturing job during well development. As such, reclaiming produced water as the base fluid for fracturing not only helps alleviate the industry’s dependence on fresh water but can also lower the overall cost of the well stimulation treatment.
Using produced water exceeding TDS values of 270,000 ppm is key to reclamation and reuse programs in the Delaware basin. This paper discusses a project to (1) identify the critical parameters and the corresponding optimal ranges in the laboratory, that will allow use of treated produced water as a base fluid for crosslinked-gel-based hydraulic fracturing, and (2) evaluate the validity of the laboratory findings under actual field conditions.
High-TDS produced water from a Brushy Canyon producing well near Carlsbad, New Mexico was used as the base fluid for the bench-scale experiments. Crosslinked gels were formulated with carboxymethyl hydroxypropyl guar gum (CMHPG), a zirconium-based crosslinker, sodium chlorite breakers, and other ingredients. The apparent viscosity of the gels was measured using Chandler Model 5550 high-pressure/high-temperature (HP/HT) viscometers. The bottomhole temperature simulated in the experiments was approximately 140°F. The rheological effects of several parameters, including pH, salinity, and scaling tendencies, were evaluated. Other factors, including organics and suspended solids, are included in the discussion. In addition, a field test performed following the bench-scale experiments to validate the laboratory findings under the actual stimulation conditions is discussed. Results indicate that the fracturing treatment using high-TDS produced water successfully created a fracture network and transported sand into that fracture network.
Production Forecasting of Hydraulically Fractured Conventional Low-Permeability and Unconventional Reservoirs Linking the More Detailed Fracture and Reservoir Parameters
Authors: Sierra Leopoldo , Mayerhofer Mike , Jin C. J. 
Published: February 2013

Abstract
Fracture stimulation and production forecasting are two important processes for conventional low-permeability or unconventional reservoirs. Fracture stimulation of either type of reservoir helps assure commercial production rates or maximize exploitation, while proper production forecasting informs the operator in advance of the potential short- and long-term value of the well and the area.
To provide more accurate recovery forecasts for conventional low-permeability or unconventional reservoirs, one must consider the key parameters of the generated hydraulic fracture, including effective fracture length (affected by filtrate clean-up and fracture damage), relative differences in fracture and formation flow capacity (e.g., dimensionless fracture conductivity), proppant distribution, tapered fracture conductivity, and stress dependence of the fracture conductivity. In addition, stress dependence of reservoir permeability and reservoir fluid properties also have a major impact. Non-darcy and multiphase flow effects inside the fracture have been extensively discussed in the literature and will not be discussed in this paper but can be indirectly included when considering the discussion on reduced fracture conductivity.
For the horizontal wellbore architecture commonly used to exploit unconventional reservoirs, the knowledge of the optimum number of fractures to maximize the recovery is very important. This paper uses a numerical reservoir simulation study to develop simple correlations that quantify what fracture spacing is necessary to optimize recovery factors in unconventional gas reservoirs and how various hydraulic fracture parameters and non-ideal reservoir behaviors affect the horizontal well completion design.
Because the reservoir simulation process can take significant time and effort, and analytical solutions are sometimes very complex, a simple "back of the envelope" methodology to estimate the optimum fracture spacing can be advantageous for everyday use and a starting point for completion optimization. This paper also discusses how deviations from ideal behavior, in terms of fracture and reservoir properties, can affect the well design.
Proppant Distribution in Multistage Hydraulic Fractured Wells: A Large-Scale Inside-Casing Investigation
Authors: Crespo Freddy , Aven Nevil Kunnath , Cortez Janette , Soliman M. Y. , Bokane Atul , Jain Siddharth , Deshpande Yogesh 
Published: February 2013

Abstract
Effectively stimulating multiple pay zones using separate fracturing treatments can be costly and time consuming. By contrast, multistage fracturing is a widely used technique that offers the advantage of stimulating significant portions of the reservoir by fracturing through multiple perforations simultaneously. While the multistage fracturing method known as "plug and perf" has been proven to be an effective method for developing unconventional resources, it presents the challenge of achieving even proppant distribution to all perforation clusters during each stimulation stage.
It is commonly assumed that the plug and perforate multistage fracturing technique provides the planned fluid and proppant distribution among the fractures that are simultaneously taking fluid during pumping a single stage. However, parameters, such as the reservoir properties, fluid rheology, and proppant characteristics have demonstrated a strong influence on the actual proppant and fluid distribution into the various perforations.
Field data indicates, in many cases, that some of the clusters do not contribute to production. This indication supports the hypothesis that actual proppant and fluid distribution along the stimulated clusters might be different from the assumed uniform distribution. Some believe that the amount of proppant appears to be heavily weighted toward the end of the perforated interval, which results in uneven proppant distribution. Empirical data as well as laboratory tests have yet to be challenged against the few studies that exist.
This paper presents a first- of-its-kind large-scale investigation that was conducted to study proppant distribution among separated perforations along a horizontal interval. These experiments closely simulate any single stage during the plug-and-perforate fracturing process. The effect of various fluid specific gravities, fluid viscosities, proppant specific gravities, proppant sizes, and slurry flow rates were investigated while keeping outside-casing parameters constant. The various aspects of proppant and fluid flow through a perforated interval are discussed. The experimental efforts discussed in this paper create a better understanding of fluid and proppant behavior in this widely used fracturing process to help achieve maximum efficiency.
Constraints on Simultaneous Growth of Hydraulic Fractures from Multiple Perforation Clusters in Horizontal Wells
Authors: Bunger A. P. , Jeffrey R. G. , Zhang X. 
Published: February 2013

Abstract
In spite of the fact that multistage hydraulic fracturing from horizontal wells is the fastest growing and arguably the most economically important application for well stimulation, there remain a number of fundamental questions relevant to determining how long to make each isolated interval and how many perforation clusters to place within each interval. This paper provides new insights to this problem by predicting how many hydraulic fractures can be expected to grow simultaneously from multiple perforation clusters pressurized by a single injection stage. These predictions are obtained from a coupled mathematical model that includes the contributions of fluid flow, rock breakage, and pressure loss through the perforations to the total power requirements for growth of arrays of multiple hydraulic fractures. For typical shale gas stimulations, radial hydraulic fractures are predicted to grow from all perforation clusters, with progressive reduction in the number of hydraulic fractures so as to maintain a ratio of the radius to the spacing that is a bit less than one. If the hydraulic fractures are contained to a height H, then multiple PKN-like hydraulic fractures are predicted to continue growing, with the length of each hydraulic fracture increasing throughout the injection and with a spacing that is approximately 1.5H when perforation losses are strong and approximately 2.5H when perforation losses are negligible. These geometric predictions are consistent with previously published observations based on microseismicity associated with stimulations in the Barnett Shale.
Diagnostic Fracture Injection Testing Tactics in Unconventional Reservoirs
Authors: Cramer D. D. , Nguyen D. H. 
Published: February 2013

Abstract
To achieve optimal production from unconventional reservoirs, it is useful to determine the permeability, pore pressure, and state of stress of rock strata. Doing so will lead to properly designed treatments, realistic predictions of well performance, and a basis for normalizing reservoir contribution when evaluating completion and stimulation effectiveness.
An effective way to derive the necessary reservoir information is to conduct in-situ pressure transient tests. Since it is difficult to inject fluid into or withdraw fluid from the pore network of tight rock, diagnostic fracture injection tests (DFIT) have been employed to create an analyzable pressure decline response, as well as to derive the minimum horizontal stress via fracture closure identification.
This paper is a study of numerous DFITs conducted in unconventional reservoirs throughout the world to evaluate the reservoir and geomechanical characteristics of the pay zone and bounding intervals. Within this body of work, experiments were implemented to study the impact of testing methods on the test response and various types of analysis methods documented in the literature were implemented and compared. The paper summarizes findings and introduces tactics for planning/conducting tests and evaluating results in a variety of unconventional reservoir types.
Topics covered in the paper include:
Defining test objectives Test planning and strategies ○ Tactics for selecting injection rates and volumes ○ Downhole shut-in techniques for hastening fracture closure and radial flow regime development. ○ Vertical vs. horizontal wells ○ Multiple injection-falloff cycles. ○ Multi-interval tests ○ Multiple non-communicating pressure gauges. ○ Tactics for understanding test height Pre-test fracture modeling for selecting injection volumes and rates and test intervals. Procedure/execution Reservoir and geomechanical considerations ○ Sub-pressured reservoirs ○ Fracture closure ○ Impact of natural fractures ○ Near-wellbore fracture complexity
Evaluating the Impact of Mineralogy, Natural Fractures and In Situ Stresses on Hydraulically Induced Fracture System Geometry in Horizontal Shale Wells
Authors: Miller Camron , Hamilton Daniel , Sturm Stephen , Waters George , Taylor Thomas , Le Calvez Joel , Singh Manish 
Published: February 2013

Abstract
The objective of this study is to better understand the impact of mineralogy, in-situ stress and natural fractures on hydraulically-induced fracture system geometry within horizontal organic shale wells. Vertical heterogeneity within organic shale occurs at a much smaller scale than that in the lateral direction. Previous studies involving borehole image analyses suggest that the lateral variability observed in most horizontal shale wells is the result of the wellbore traversing multiple layers of different rock properties (i.e., vertical heterogeneity). Results have shown that a more efficient and effective hydraulic fracture stimulation is possible when this variability is addressed in the completion design.
Borehole micro -resistivity image data from horizontal wells in multiple U.S. shale basins are analyzed and compared to borehole -based micro -seismic data. Natural and drilling-induced fracture type, spacing and orientation are analyzed in order to reveal their impact on hydraulic fracture initiation and geometry. Natural fracture orientation relative to the maximum horizontal stress has been shown to influence hydraulically-induced fracture system geometry. Drilling-induced fractures are essentially miniature hydraulic fractures and provide information about near wellbore in-situ stresses that can be used to predict relative hydraulically -induced fracture initiation pressures and geometry. Previous studies have shown that fracture initiation pressure is directly proportional to clay content within organic shale reservoirs.
This study provides an improved understanding of factors that ultimately control the economics of horizontal shale wells. Horizontal measurements collected during drilling or post-drill allow for (i) understanding where the wellbore is in section (i.e., well placement), (ii) visualization of how the reservoir characteristics are changing along the lateral wellbore (i.e., heterogeneity) and, (iii) planning the stimulation accordingly (i.e., treatment design). These data allow operators to predict how certain reservoir properties impact reservoir stimulation. Such correlations should lead to improved operational efficiency and better well performance, thereby increasing return on investment.
Thoracobiliary fistulas: literature review and a case report of fistula closure with omentum majus
Authors: Crnjac Anton , Pivec Vid , Ivanecz Arpad 
Published: February 2013

Abstract
Background. Thoracobiliary fistulas are pathological communications between the biliary tract and the bronchial tree (bronchobiliary fistulas) or the biliary tract and the pleural space (pleurobiliary fistulas).
Review of the literature. We have reviewed aetiology, pathogenesis, predilection formation points, the clinical picture, diagnostic possibilities, and therapeutic options for thoracobiliary fistulas.
Case report. A patient with an iatrogenic bronchobiliary fistula which developed after radiofrequency ablation of a colorectal carcinoma metastasis of the liver is present. We also describe the closure of the bronchobiliary fistula with the greater omentum as a possible manner of fistula closure, which was not reported previously according to the knowledge of the authors.
Conclusions. Newer papers report of successful non-surgical therapy, although the bulk of the literature advocates surgical therapy. Fistula closure with the greater omentum is a possible method of the thoracobiliary fistula treatment.
The value of the sagittal-oblique MRI technique for injuries of the anterior cruciate ligament in the knee
Authors: Nenezić Dragoslav , Kocijancic Igor 
Published: February 2013

Abstract
Background. Complete rupture of the anterior cruciate ligament (ACL) does not represent a diagnostic problem for the standard magnetic resonance (MR) protocol of the knee. Lower accuracy of the standard MR protocol for partial rupture of the ACL can be improved by using additional, dedicated MR techniques. The study goal was to draw a comparison between sagittal-oblique MR technique of ACL imaging versus flexion MR technique of ACL imaging and, versus ACL imaging obtained with standard MR protocol of the knee.
Patients and methods. In this prospective study we included 149 patients who were referred to magnetic resonance imaging (MRI) examination due to knee soft tissues trauma during 12 months period. MRI signs of ACL trauma, especially detection of partial tears, number of slices per technique showing the whole ACL, duration of applied additional protocols, and reproducibility of examination were analysed.
Results. Accuracy of standard MRI protocol of the knee comparing to both additional techniques is identical in detection of a complete ACL rupture. Presentations of the partial ruptures of ACL using flexion technique and sagittaloblique technique were more sensitive (p<0.001) than presentation using standard MR protocol. There was no statistically significant difference between MRI detection of the ruptured ACL between additional techniques (p> 0.65). Sagittal-oblique technique provides a higher number of MRI slices showing the whole course of the ACL and requires a shorter scan time compared to flexion technique (p<0.001).
Conclusions. Both additional techniques (flexion and sagittal-oblique) are just as precise as the standard MR protocol for the evaluation of a complete rupture of the ACL, so they should be used in cases of suspicion of partial rupture of the ACL. Our study showed sagittal-oblique technique was superior, because it did not depend on patient’s ability to exactly repeat the same external rotation if standard MR protocol was used or to repeat exactly the same flexion in flexion MR technique in further MR examinations. Sagittal-oblique technique does not require the patient’s knee to be repositioned, which makes this technique faster. We propose this technique in addition to the standard MR protocol for detection of partial ACL tears.