bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gel Degradation Studies of Oxidative and Enzyme Breakers to Optimize Breaker Type and Concentration for Effective Break Profiles at Low and Medium Temperature Ranges
Authors: Sarwar M. U. , Cawiezel K. E. , Nasr-El-Din H. A. 
Published: January 2011

Abstract
Chemical breakers are used in hydraulic fracturing fluids to reduce the molecular weight of guar polymers which reduces fluid viscosity and facilitates the flowback of residual polymer providing rapid recovery of polymer from the proppant pack. Ineffective breakers or misapplication of breakers can result in screenouts or flowback of viscous fluids both of which can significantly decrease the well productivity.
Breaker activity of low to medium temperature range oxidative and enzymatic breaker systems was evaluated, including ammonium persulfate, sodium persulfate, calcium and magnesium peroxides, and galactomannanase enzyme in linear gel fluids at temperatures from 75 oF-300 °F. Low temperature and high temperature viscometers were used to generate linear gel- break curves with time at desired temperature. The amount of unbroken gel and residue, generated at different temperatures and breaker concentrations, was also determined using a "residue-after-break test (RAB)," for two oxidizers and one enzyme breaker, all used for similar temperature applications in the field.
Viscosity measurement showed that reduction in the gel viscosity depends on both the breaker concentration and temperature. Also, increasing breaker concentration does not necessarily mean more reduction in viscosity. This paper provides a guideline of oxidative and enzyme breaker optimum use concentrations for specific temperatures in the form of breaker activity "S" curves. Enzyme breakers were found to provide a more homogeneous break and generate less residue compared to the oxidztive breakers in the resdiue-after-break (RAB) tests.
Practical Data Mining: Lessons Learned from the Barnett Shale of North Texas
Authors: LaFollette Randy F. , Holcomb William D. 
Published: January 2011

Abstract
This paper documents a data-mining study of well, hydraulic fracture treatment, and production parameters for horizontal wells in the north Texas Barnett Shale play. In this study, the authors have analyzed well and production data from more than 13,400 producing Barnett wells. A subsample of over 3,300 horizontal wells was characterized with respect to detailed well architecture data such as drift direction and angle, lateral length, perforations, etc. The study uses Geographical Information System pattern-recognition techniques in conjunction with more traditional statistical techniques to interpret hidden trends in otherwise scattered data sets. This work provides a case study in the practical use of data-mining techniques to address questions of best practices in Shale Gas reservoirs. It is made possible because the availability and quality of public domain well and production data has increased significantly in the past few years. Simple cross plotting of production data against well and treatment variables normally leads to broad scattering of results. This study takes advantage of the largest, richest well and production data set available from the gas shales and identifies key lessons-learned. Relevant trends, such as the impact of toe up versus flat versus toe down, horizontal well length, and drift angle variability on gas production rate are presented. This work is significant in that it shows that the application of practical data-mining methods to a large Shale Gas data set can result in learning key lessons that may not be apparent when working with small data sets. This work is also significant in the use of merged reservoir quality proxies, well architecture data, completion data, and stimulation data, against which production results are placed in geographical perspective for improved interpretation.
Single Versus Multiwell Microseismic Recording: What Effect Monitoring Configureation Has On Interpretation
Authors: Seibel Margaret , Baig Adam 
Published: January 2011

Abstract
Three monitoring wells with permanently installed 3C geophones were used to locate the microseismicity induced from a steam production cycle. This dataset of 52 high signal-to-noise ratio events were used to examine the location of events by progressively decimating the number sensor arrays. The three-array solutions were contrasted with different array combinations achieved by turning off one or two of the arrays. Event locations revealed the nature and magnitude of the limitations having incomplete coverage of the treatment zone.
Most steam and fracture treatments are monitored by a single observation well. Parameters, such as stimulated reservoir volume fracture azimuth and fracture dimensions in treatments like CSS, hydraulic fracturing, SAG-D, are estimated from the distribution of microseismic event locations. By taking three array locations as ground truth, the array configurations that most accurately reflect the actual fracture geometry are determined.
The observed distributions of the events relocated with decimated arrays show significant changes in overall fracture trend, geometry, and location accuracy. Progressive decimation of the number of arrays increases the inaccuracies of event locations, which results in the scatter of event locations. Decimation of the number of arrays changes the dimensions and azimuth of fractures, which are readily apparent upon comparison with the three-array solutions. The least biased decimated solutions are those using two arrays, one on either side of the treatment zone. Single array solutions show the most scatter, with the recording distance also controlling the degree of event mislocation.
This array decimation analysis shows how the array configuration and number for arrays affect the interpreted fracture volumes, geometries, and accuracy of event location. The different viewing angles from the single and dual array decimated subsets, as well as the different distances from the event clusters to the geophones are important considerations in mitigating the biases due to limiting the recording coverage.
Soft Rock Fracturing Geometry And Failure Mode In Lab Experiments
Authors: Olson Jon E. , Holder Jon , Hosseini S. Mehran 
Published: January 2011

Abstract
Hydraulic fracturing of uncemented sand was investigated with theoretical calculations and physical laboratory experiments to investigate crack tip mechanics for soft rock applications. The mechanics of soft rock fracturing is an important topic for the better understanding of injection operations in weakly or unconsolidated sands. Fracpack treatments, waste injection, and steam injection for heavy oil recovery are all applications for which the application of standard elastic hydraulic fracturing models may be inadequate due to expected nonelastic deformation components.
Analytical calculations indicate that shear associated with hydraulic fracturing is likely in unconsolidated sands at depth, but cases of high overpressure promote tensile mode fracturing. An expression is derived to predict the rock strength required in terms of UCS to achieve tensile fracture. Preliminary physical experiments were performed to ascertain failure mode in uncemented sand at low confining stress and to investigate shear failure under high viscosity injection. Physical specimens were created using sand ranging from 100 to 300 micron in diameter, compacted with wet vibration. Preliminary fracture opening experiments performed using solid wedging were imaged with a CT-scanner and demonstrated near-tip shear failure propagating diagonally away from the crack tip, but not along the in-plane propagation direction. Injection experiments indicated complex fracture propagation geometries involved fracture plane segmentation and curving. Preliminary results indicate fracture propagation mode is predominantly tensile and not shear, although deformation in the vicinity of the hydraulic fracture showed evidence of shear. Higher stress anisotropy is anticipated to increase the likelihood of shear failure over tensile failure.
Design of Multiple Transverse Fracture Horizontal Wells in Shale Gas Reservoirs
Authors: Song Bo , Ehlig-Economides Christine , Economides Michael J. 
Published: January 2011

Abstract
The game changing technology enabling economic natural gas production from shale is the multiple fracture well (MFTW), a horizontal well with multiple transverse fractures. The well itself can create a stimulated reservoir volume (SRV) that delineates sufficient gas reserves to payout the well and provide continued return for several decades. This paper shows the importance of permeability and adsorbed gas in ensuring a well design that will achieve these objectives.
In this paper we base decisions about the number and size of fractures and the horizontal well length (and therefore the fracture spacing) first on the physics of production and then on investment economics. Current practices using a repetitive well template applied to all wells in a given shale gas play result in some wells doing far better than expected while others barely pay out. We show that linear flow is likely to dominate production behavior until pressure interference occurs between adjacent fractures and that the time of inter-fracture interference predicted by linear flow pressure penetration is prolonged by desorption.
The shale permeability and the adsorbed gas parameters are used to design an economically successful well while ensuring at least 50% gas recovery in the SRV within a specified period of time. Field data from several shale gas formations are used to provide examples of the well design approach. The gas adsorption characterization typically comes from laboratory analysis, which we use to develop what we have called the adsorption index. Because the gas recovery factor depends on lowering the average pressure in the SRV, permeability and the adsorption index are used to estimate the time of inter-fracture interference, which in turn indicates the optimal spacing between fractures. This paper provides insights on the effective exploitation of a shale gas reservoir by optimizing the fracture and well architecture.
Integration of Production Analysis and Rate-Time Analysis via Parametric Correlations — Theoretical Considerations and Practical Applications
Authors: Ilk D. , Rushing J. A. , Blasingame T. A. 
Published: January 2011

Abstract
Well performance analysis in unconventional reservoirs is a challenging task because of the non-uniqueness associated with estimating well/formation properties. In addition, estimation of reserves is often uncertain due to very long transient flow periods. Recently, new semi-empirical rate-time relations (Ilk et al. 2008 and 2010) have been shown to properly model the rate-time behavior for wells in unconventional reservoirs. The success of these new rate-time relations has led us to focus on finding theoretical and empirical relationships between rate-time model parameters with well/formation properties.
This work attempts to integrate model-based production analysis (i.e., semi-analytical/analytical solutions) and rate-time analysis by using parametric correlations. We perform production analysis and rate-time analysis for various tight gas and shale gas wells, and then correlate the various model parameters from the rate-time equations with the well/formation properties estimated using full (model-based) production data analysis.
We demonstrate the application of the proposed methodology by using a sample of wells producing in tight gas and shale gas reservoirs. We can show that the integration of production analysis and rate-time analysis via parametric correlations is highly-dependent on the size of data sample (i.e., the number of wells) and the data quality. When high-quality data and ample production data are available, formation permeability and fracture half-length are well-correlated with the model parameters of the rate-time relations.
First Downhole Application of Distributed Acoustic Sensing (DAS) for Hydraulic Fracturing Monitoring and Diagnostics
Authors: Molenaar Mathieu M. , Hill David , Webster Paul , Fidan Erkan , Birch Bill 
Published: January 2011

Abstract
The first E&P downhole field trial of Distributed Acoustic Sensing (DAS) fibre optic technology was conducted by Shell Canada during the completion of a tight gas well in February 2009.
DAS is a novel technology that allows the detection, discrimination and location of acoustic events on a standard telecom single-mode fibre of several kilometres in length. Using a combination of the measurement of backscattered light and advanced signal processing, the DAS interrogator system segregates the fibre into an array of individual "microphones". To date the technology has been mainly applied in the defense and security industries. One of the most exciting applications for downhole application of DAS is in the area of hydraulic fracturing of tight sand and shale gas reservoirs. Balancing the cost of hydraulic fracture stimulation versus the production benefit is crucial in a tight sand and shale gas developments as, after drilling costs, the completion is the largest single cost component of the well.
Recordings were made while tools were run in hole, bridge plugs set, perforations shot and during the fracture stimulation treatment(s). The technology proved sufficiently reliable and sensitive to detect and monitor these in-well activities. The fidelity of the recordings made during hydraulic fracturing and flow back operations, provided a step-change improvement in the ability to perform real-time and post-job diagnostics & analyses of the stimulation.
The different case studies presented in this paper will illustrate how, even in its earliest form, DAS has the potential to enhance the capability of monitoring and understanding in-wellbore activities. The technology enables the optimization of hydraulic fracturing design and execution, which could drive down completion costs and lead to increased well productivity and ultimate recovery.
Experimental Validation of Microseismic Emissions from a Controlled Hydraulic Fracture in a Synthetic Layered Medium
Authors: Roundtree Russell , Miskimins Jennifer L. 
Published: January 2011

Abstract
Experiments using acoustic sensors to monitor stress changes and hydraulic fracture propagation in moderate size, layered rock samples are described in this paper. The results show that microseismic event locations closely follow the actual growth of the hydraulic fracture, especially near the well bore. More events are detected and localized near the acoustic transducers indicating that signal attenuation is significant. In the work performed, event location based on automated picking techniques is not yet accurate enough to make diagnostic conclusions about fracture propagation near and through the different layered materials. Advanced processing techniques being developed in industry may well have the additional resolution necessary to focus some of these more subtle events at the laboratory scale. The conducted experiments indicated that controlling hydraulic fracture growth in laboratory-sized samples is difficult in small and moderate sized samples, and dynamically changing flap jack pressures, and injection rates and pressures is mandatory to slow the fracture growth for proper analysis once it has initiated. A key outcome of the work is the recognition that rocks emit substantial amounts of acoustic energy when stressed at incremental pressure levels of only a few psi, which corroborates a model of rocks as being meta-stable materials and explains frequently observed field phenomena. Further advancements in the use of acoustic monitoring at the laboratory scale are warranted and significant breakthroughs are possible for non-invasive investigations of solid and layered materials under stress.
Advancements in Efficiency in Horn River Shale Stimulation
Authors: Demong Karl , Hands Ron , Affleck Brad 
Published: January 2011

Abstract
In the remote Horn River Shale of North East British Columbia, Canada the key challenge operators’ face is high costs related to completions in the horizontal wells. A strategy was developed to focus on efficiency improvements to make a positive impact on the economics. Previous projects were examined and a two prong approach was developed: first we needed to procure as many extra resources as could be anticipated to ensure continuous operations, and second we would have to have more than one critical path operation simultaneously so that costly activities could continue uninterrupted.
The resource planning includes the drilling of multiple wells on the pad and having most of the wells available for operations during the stimulation campaign. It also includes specially designed equipment such as bulk sand handling equipment, water handling, slurry handling, wellhead protection, SCADA systems and custom flow back equipment. In addition, new ways of managing the human resources at the site were implemented. To manage the critical path activities, a protocol was developed to manage surface and down hole interactions. A safety system was developed to support the integration of these challenging operations. An offsite real time operations room was employed were all the sensor data from the site was available, including frac data, water and sand supply, pressure and H2S.
The resulting impact on efficiency will be discussed in detail, including reaching a field frac efficiency record for the Horn River.
Teaching Punctuation in Early Modern England
Authors: Rodríguez-Álvarez Alicia 
Published: January 2011

Teaching Punctuation in Early Modern England
Much has been written on the punctuation practice of late sixteenth- and seventeenth-century English writers in order to work out the ultimate function of marks of punctuation. The main point of discussion has almost ever been whether punctuation indicated syntactic relationships or represented speech pauses either to give emphasis in oral delivery or just to be able to breathe. The focus of this paper, however, is the theory rather than the practice, in particular, the set of rules and conventions used by schoolmasters to guide students in their use of stops. Thus, textbooks used at the time to teach reading and writing will constitute our main sources of information to achieve the following aims: (i) to offer a classification of the different marks of punctuation described, (ii) to establish the functions schoolbooks assigned to punctuation marks in general, and (iii) to assess the importance schoolmasters gave to pointing. The results of this study - which follows the works by Ong (1944) and Salmon (1962, 1988) - will contribute to shed light on the ever-lasting debate on the principles guiding Early Modern English punctuation usage.
The Bases of Derivation of Old English Affixed Nouns: Status and Category
Authors: Torres Elisa 
Published: January 2011

The Bases of Derivation of Old English Affixed Nouns: Status and Category
The aim of this journal article is to carry out a complete analysis of the category, status and patterns of the bases of derivation of Old English affixal nouns. The results of the analysis are discussed in the light of the evolution from stem-formation to word-formation. The corpus of analysis of this research is based on data retrieved from the lexical database of Old English Nerthus, which contains 30170 predicates. 16694 out of these are nouns, of which 4115 are basic and 12579 qualify as non-basic. Within non-basic nouns there are 3488 affixed nouns (351 by prefixation and 3137 by suffixation) and 9091 compound nouns. The line of argumentation is that, under certain circumstances, the existence of more than one base available for the formation of a derivative does not reinforce the explanation of invariable bases; on the contrary, it goes in the direction of variable bases produced by inflectional processes and made ready for derivation. The following conclusions are reached. In the first place, the importance is underlined of formations on stems in Old English, involving, at least, nouns. Secondly, the analysis evidences that the importance of stem-formation in Old English might be higher than has been acknowledged by previous studies. If Old English made extensive use of words as bases of derivation, a single base should be available; if, on the contrary, Old English is still dependent on stem-formation, more than one base is likely to be found for a single derivative. Such alternative bases of derivation reflect stemformation that may result from inflectional means and be eventually used for derivational purposes.
Measuring Specificities of Dissipation Factor of Electrical Equipment in Substations
Authors: Gavrilovs Gerards , Vītoliņa Sandra 
Published: January 2011

Measuring Specificities of Dissipation Factor of Electrical Equipment in SubstationsMeasuring techniques of dielectric losses tanδ of high voltage equipment are discussed and compared in this paper. There are several methods for determining tanδ and capacitance values in high voltage substation on site.Simple measuring methods like GST and UST can be put into practice without result corrections in ideal conditions. However electrical field in substation originates negative affect on measuring results, therefore different connection schemes of measuring methods have to be used.
Application of Integrated Hardware and Software System "PRIZNAK-10M" for Measuring Power-Frequency Electric and Magnetic Fields in Electric Networks
Authors: Kurbatsky Victor 
Published: January 2011

Application of Integrated Hardware and Software System "PRIZNAK-10M" for Measuring Power-Frequency Electric and Magnetic Fields in Electric NetworksOne of the urgent problems in modern power industry is to provide safety of man staying in the affected area of electric and magnetic fields generated by operating electric facilities. The paper presents integrated hardware and software system "PRIZNAK-10M", intended for measurement of power-frequency electric and magnetic fields in electric networks. Integrated hardware and software system put into practice the methods of measurements, met the regulatory documents effected in electric networks of Russia. The recommendations have been developed to provide the man safely at the facilities studied.
Practical Design Guidelines of qZSI Based Step-Up DC/DC Converter
Authors: Zakis Janis , Vinnikov Dmitri , Roasto Indrek , Jalakas Tanel 
Published: January 2011

Practical Design Guidelines of qZSI Based Step-Up DC/DC ConverterThis paper presents some design guidelines for a new voltage fed step-up DC/DC isolated converter. The most significant advantage of proposed converter is voltage buck-boost operation on single stage. The most promising application for proposed converter is in the field of distributed power generation e.g. fuel cells or photovoltaic.The most sensitive issues - such as power losses caused by high currents in the input side of converter and high transient overvoltages across the inverter bridge caused by stray inductances were discussed and solved. The proposals and recommendations to overcome these issues are given in the paper. The Selection and design guidelines of converter elements are proposed and explained.The prototype of proposed converter was built and experimentally tested. Some results are presented and evaluated.
Switch-Off Behaviour of 6.5 kV IGBT Modules in Two-Level Voltage Source Inverter
Authors: Blinov Andrei , Jalakas Tanel , Vinnikov Dmitri , Janson Kuno 
Published: January 2011

Switch-Off Behaviour of 6.5 kV IGBT Modules in Two-Level Voltage Source InverterThis paper presents an analysis of the switch-off process of 6.5 kV/200 A IGBT modules in a two-level half-bridge voltage source inverter. During experiments, it was stated that real switching process is far from ideal switch-off since parasitic inductance and capacitance in the circuit cause voltage spikes and high frequency oscillations during transition processes. Operation states of the inverter are described and analyzed. Experimental and simulation results are compared, the main transients are analyzed and mathematically expressed and possible problems and solutions are discussed.