bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessing the Spacing of Stages in Plug and Perf Completions in the Marcellus Shale
Authors: Baig Adam M. , Urbancic Ted , Goldstein Shoshana 
Published: June 2012

Abstract
Completion programs for hydraulic fracture stimulations are planned to optimize the spacing of wells and perforation clusters such that the largest volume of the reservoir can be accessed through the promotion of a discrete fracture network in the reservoir. Such treatments also seek to minimize costs associated with pumping proppants and fluids down wells by ensuring that these injectants reach their target formations, stay in zone, and act to promote the stimulation of the reservoir. From this viewpoint, it is seen as desirable to minimize the overlap of treatment volumes between neighbouring wells and stages to avoid the preferential diversion of proppants and fluids into the previously stimulated volumes of the reservoir. However, it has also been argued that the creation of new fractures in a previously treated volume promotes a complex fracture network enhancing drainage. When these stimulations are monitored from multiple geophone arrays surrounding the treatment zone, seismic moment tensor inversion (SMTI) analysis offers the ability to test these hypotheses by inferring if the microseismic events are related to the opening of or closure of pre-existing natural or newly created fractures. In this paper, we discuss event clusters that occur with a significant degree of overlap between neighbouring stages in the Marcellus Shale. Because the events were monitored with multi-array sensor configuration, the SMTI calculations can be conducted with a high degree of accuracy. SMTI allows for the orientations of the underlying fractures to be determined, allowing us to construct a discrete fracture. Further analysis of the orientations of the underlying fractures also enable us to assess which fractures are being activated in relation to the pre-existing structures in the reservoir, and how the activation of those structures correlates to estimates of stimulated reservoir volume which we relate to the regions of the reservoir where an complex, intersecting fracture network is being activated by the stimulation.
Optimal Well Spacing Configurations for Unconventional Gas Reservoirs
Authors: Sahai Vivek , Jackson Greg , Rai Rakesh , Coble Larry 
Published: June 2012

Abstract
Determining the optimal number of wells for infill drilling in an unconventional reservoir is a critical endeavor for shale gas operators as many leases are held only by production. To develop a given section, operators must select locations and completion designs for all wells. The planned well placement and completion design will dictate the economic viability and production of the field for the asset's life. The key factors impacting performance in shale gas reservoirs can be broadly divided into two categories: controllable and uncontrollable. Uncontrollable factors include rock properties such as porosity, water saturation, net-to-gross, initial pressure, permeability, natural fractures, and fluid properties. Controllable factors related to producibility that can be optimized include well design, completion design, well placement, surface facilities design, and operating conditions.
Development schemes must consider both engineering and economic risks that include reduction of reservoir permeability due to rock compaction and changes in completion characteristics/efficiency. To determine optimal development, these factors have to be evaluated. This paper outlines the results of well optimization studies initiated from a production performance analysis of over 100 wells in the Haynesville Shale and over 300 wells in the Marcellus Shale. Both analytical and numerical tools were used in the presented workflow. The study results indicate a threshold of reservoir and completion properties below which any well drilled may be uneconomic based on our financial assumptions. Original gas-in-place (OGIP), rock brittleness, and fracture height containment were considered with regard to stimulated reservoir volume, SRV. The effect of natural fractures was also studied. With low gas prices, optimal capital allocation is a critical development component and is an issue that all operators face. The subsequent results presented could save operators myriad hours of simulation effort while potentially saving millions of dollars by eliminating unnecessary wells.
Focus on Cement Design and Job Execution Increase Success for Shale Cementing Operations
Authors: Bassett Jessica , Watters Jeff , Sabins Fred , Febbraro Anthony 
Published: June 2012

Abstract
In recent years, drilling and production activity in US shale gas has been increasing. This high volume of work has led to the use of manufacturing-style well construction. Each area has its own challenges; however, problematic wells are prevalent in many shale plays. A major study in the Haynesville shale targeted the manufacturing-style methodology. Over the course of the study, more than 160 cement jobs were analyzed including surface, intermediate and production strings. This study implemented the use of careful engineering decisions that were focused on the issues and challenges specific to wells in this area. This was achieved through analyzing and optimizing the laboratory operations, design of cement systems, bulk plant and job site processes. This study shows by taking the proper steps to design these processes, a manufacturing style approach can be very successful when applied in challenging shale cementing operations.
Optimizing Completion Designs for Horizontal Shale Gas Wells Using Completion Diagnostics
Authors: Bartuska J. E. , Pechiney J. J. , Leonard R. S. , Woodroof R. A. 
Published: June 2012

Abstract
In horizontal shale completions, one of the primary goals is to maximize contact with the most reservoir rock and effectively drain the complex fracture network that has been created during the stimulation process. This paper covers a five-well case study in the Marcellus Shale where completion diagnostics were used to evaluate and optimize the completion process. The case histories will detail key completion parameters and how they changed over time based on various diagnostic results.
Completion diagnostics such as proppant and fluid tracers can be integrated with production, stimulation and geologic data to provide useful information as to the effectiveness of the completion design. Proppant tracers have been utilized in horizontal shale basins throughout North America to evaluate near-wellbore fracture initiation, identify un-stimulated perforations, and evaluate proppant interference between stimulated wellbores. Fluid tracers are currently being used to analyze lateral clean-up over time and to quantify fracture fluid interference between wells.
In this case study, these diagnostic technologies were instrumental in addressing several completion design questions. Proppant tracers were used to evaluate cluster and stage spacing and also identified proppant interference with adjacent wells. Fluid tracers were utilized to evaluate overall load fluid recoveries for various wellbore trajectories and helped quantify the source and amount of interference between wells.
Mean Corpuscular Volume as a Marker for Adherence to Zidovudine-Containing Therapy in HIV-Infected Adults
Authors: Mugisha Joseph O , Donegan Katherine , Fidler Sarah , Ramjee Gita , Hodson Andrew , Dunn David T , Porter Kholoud , Kaleebu Pontiano 
Published: June 2012

Objectives:To assess whether mean corpuscular volume (MCV) is useful in detecting non-adherence to AZTcontaining therapy.Design:Observational study within randomised controlled trial.Methods:We combined data from two treatment arms in SPARTAC, an RCT of short-course cART in primary HIV infection, classifying participants as responders (HIV-RNA decrease ≥1 log10or reaching <400copies/ml) or nonresponders following cART initiation. We assessed the sensitivity and specificity of using different percentage increases in MCV for accurately differentiating between responders and non-responders. We further examined changes in MCV levels up to 24 weeks after protocol-indicated cART cessation.Results:Of 119 participants included in this analysis, 73 (61%) were women, 71 of whom were randomised in Africa. Ninety-eight (88%) and 84 (85%) were classified as responders at 4 and 12 weeks respectively following cART initiation. MCV increased by a mean 3% and 1% at week 4, and 14% and <1% at 12 weeks for responders and non-responders. A 2% MCV increase at 4 weeks had 62% sensitivity and specificity for identifying virological response. At 12 weeks, an 8% increase had 89% sensitivity and specificity. In responders, MCV remained lower for individuals in African compared to non-African sites throughout and rose from 85vs90 fL at cART start to 96vs103 fL at 12 weeks post-initiation then fell to 88vs93 fL and 86vs89 fL at 12 and 48 weeks post-cessation.Conclusion:In low-income countries, where HIV RNA may be unavailable, 12-weekly MCV measurements may be useful in monitoring adherence to AZT-containing regimens.
Phosphoric Acid-Etching Promotes Bond Strength and Formation of Acid-Base Resistant Zone on Enamel
Authors: Li N , Nikaido T , Alireza S , Takagaki T , Chen J-H , Tagami J 
Published: June 2012

SUMMARY
This study examined the effect of phosphoric acid (PA) etching on the bond strength and acid-base resistant zone (ABRZ) formation of a two-step self-etching adhesive (SEA) system to enamel. An etch-and-rinse adhesive (EAR) system Single Bond (SB) and a two-step SEA system Clearfil SE Bond (SE) were used. Human teeth were randomly divided into four groups according to different adhesive treatments: 1) SB; 2) SE; 3) 35% PA etching→SE primer→SE adhesive (PA/SEp+a); (4) 35% PA etching→SE adhesive (PA/SEa). Microshear bond strength to enamel was measured and then statistically analyzed using one-way analysis of variance and the Tukey honestly significant difference test. The failure mode was recorded and analyzed by χ2 test. The etching pattern of the enamel surface was observed with scanning electron microscope (SEM). The bonded interface was exposed to a demineralizing solution (pH=4.5) for 4.5 hours and then 5% sodium hypochlorite with ultrasonication for 30 minutes. After argon-ion etching, the interfacial ultrastructure was observed using SEM. The microshear bond strength to enamel of the SE group was significantly lower (p&lt;0.05) than that of the three PA-etched groups, although the latter three were not significantly different from one another. The ABRZ was detected in all the groups. In morphological observation, the ABRZ in the three PA-etched groups were obviously thicker compared with the SE group with an irregular wave-shaped edge.
The depopulation of the Bulgarian villages
Authors: Mladenov Chavdar , Ilieva Margarita 
Published: June 2012

The depopulation of the Bulgarian villagesThe depopulation process in Bulgaria, especially in rural areas, is intensifying due to deepening unfavourable trends in the dynamics of demographic processes. Depopulation is a typical process in the fourth phase of demographic transition in rural areas of Bulgaria. The death rates exceed birth rates in the rural areas in the mid-1970s. The size of rural population and the number of villages in the country has been decreasing in the last decades. A large part of the villages were affected by depopulation processes during the period 1985-2007. A high depopulation level is observed in border and mountainous regions. The depopulation generates an array of different negative trends in the spatial aspect - in socio-economic development, technical and social infrastructure, as well as the erasure of many small villages. The regional development plans need to embed measures for infrastructural development in order to attract and retain residents, utilise natural and cultural-historical heritage, and to stimulate economic activities and the development of various types of tourism, etc.
Trajectories of the demographic development of Poland after 1989
Authors: Parysek Jerzy , Mierzejewska Lidia 
Published: June 2012

Trajectories of the demographic development of Poland after 1989
One of the major problems of contemporary Poland is its increasingly difficult and complicated demographic situation. This makes the identification of demographic trends of the recent years an important research task. The article presents an assessment of Poland's demographic situation after 1989, i.e. after the change of the country's socio-political system, using the graphic method of trajectories. It is one of the possible, though less popular, methods of studying time series, offering a new perspective on various processes, here demographic ones. The article has two aims: cognitive and methodological.
New Mississippian trilobite association from the Brno vicinity and its significance (Moravian Karst, Czech Republic)
Authors: Rak Štěpán , Kalvoda Jiří , Devuyst Francois-Xavier 
Published: June 2012

New Mississippian trilobite association from the Brno vicinity and its significance (Moravian Karst, Czech Republic)
Eleven trilobite species (Archegonus (Archegonus) aequalis philliboloides R. Hahn, 1967, Bollandia persephone (Hahn & Hahn, 1970), Bollandia cf. megaira (Hahn & Hahn, 1970), Liobole (Panibole) cf. jugovensis (Osmólska, 1968), Liobole (Sulcubole) glabroides (Richter & Richter, 1949), Semiproetus (Macrobole) drewerensis latipalpebratus (Osmólska, 1973), Proliobole vigilax (Chlupáč, 1961), Cyrtoproetus (Cyrtoproetus) cracoensis cracoensis (Reed, 1899), Carbonocoryphe (Carbonocoryphe) bindemanni Richter & Richter, 1950, Tawstockia (Beleckella) milleri (Hahn & Hahn, 1971), Cummingella (Cummingella) cf. auge Hahn & Hahn, 1968) are described for the first time from the shales of the Březina Formation in Mokrá Quarry near Brno (Bohemian Massif, Moravian Karst). This typical trilobite association — comparable to that previously described from the Erdbacher Kalken of Steeden in Hessen (Germany) — was found during excavation in the Mokrá Quarry but they do not come from the exact Tournaisian-Visean boundary. Stratigraphical correlation and comparison of material is mentioned below, as is the history of the trilobite research from the Moravian Karst.
Nannofossil record across the Cenomanian-Coniacian interval in the Bohemian Cretaceous Basin and Tethyan foreland basins (Outer Western Carpathians), Czech Republic
Authors: Švábenická Lilian 
Published: June 2012

Nannofossil record across the Cenomanian-Coniacian interval in the Bohemian Cretaceous Basin and Tethyan foreland basins (Outer Western Carpathians), Czech RepublicNannofossil biostratigraphy and mutual correlation was worked out for the Cenomanian-Coniacian deposits of the Bohemian Cretaceous Basin (BCB) and Outer Western Carpathians (OWC) in the territory of the Czech Republic. Similar assemblages of the BCB and from sediments deposited on the SE slopes of West European Platform, Waschbergždánice-Subsilesian Unit, OWC support the hypothesis that the two areas were connected by a sea way (nowadays the Blansko trough). The nannoflora of the Silesian Unit, OWC show more afinity to high latitudes as is documented by the presence ofMarthasterites furcatusin the Lower Turonian, UC6b and UC7 Zones. Turonian and Coniacian deep-water flysch sediments of the Silesian Unit and Magura Group of Nappes provide nannofossils on rare occassions. Strongly atched nannofossils dominated byW. barnesiaefrom Cenomanian black shales of the BCB are comparable to those of the Silesian Unit and reflect a similar shallow nearshore sea. In the BCB, uppermost Cenomanian is marked by the last occurrence (LO) ofAxopodorhabdus albianusand first occurrence (FO) ofQuadrum intermedium(6 and 7 elements) and lowermost Turonian by a sudden quantitative rise in nannoflora and by the FOEprolithus octopetalus.FirstEiffellithus eximiusand thus the base of the UC8 Zone was recorded in the upper part of ammonite ZoneCollignoniceras woollgariin the lower Middle Turonian.Lithastrinus grilliiis the stratigraphically youngest nannofossil species in this region and indicates the uppermost Coniacian. In the OWC, the Albian-Cenomanian boundary was recorded in the Silesian Unit and is marked by the LOCrucicribrum anglicumand FOPrediscosphaera cretaceaandCorollithion kennedyiin the uppermost Albian. The Turonian-Coniacian boundary found both in the BCB and Waschberg-Ždánice-Subsilesian Unit, OWC is indicated by the FOBroinsonia parca expansaand by the base of the interval with commonMarthasterites furcatus.In both areas, events were found closely below the FO inoceramid speciesCremnoceramus waltersdorfensis.The Coniacian-Santonian boundary interval (Waschberg-Ždánice-Subsilesian and Foremagura Units, OWC) is indicated byLithastrinus grilliioccasionally accompanied byLucianorhabdusex gr.cayeuxii, Hexalithussp. andArkhangelskiella specillata.
Validation of GOCE global gravity field models using terrestrial gravity data in Norway
Authors: Šprlák M. , Gerlach C. , Pettersen B. 
Published: June 2012

Validation of GOCE global gravity field models using terrestrial gravity data in NorwayThe GOCE (Gravity field and steady-state Ocean Circulation Explorer) satellite gravity gradiometry mission maps the Earth's gravity field. Harmonic analysis of GOCE observations provides a global gravity field model (GGFM). Three theoretical strategies, namely the direct, the space-wise and the time-wise approach, have been proposed for GOCE harmonic analysis. Based on these three methods, several GGFMs have been provided to the user community by ESA. Thereby different releases are derived from different periods of GOCE observations and some of the models are based on combinations with other sources of gravity field information. Due to the multitude of GOCE GGFMs, validation against independent data is a crucial task for the quality description of the different models.In this study, GOCE GGFMs from three releases are validated with respect to terrestrial free-air gravity anomalies in Norway. The spectral enhancement method is applied to avoid spectral inconsistency between the terrestrial and the GOCE free-air gravity anomalies.The results indicate that the time-wise approach is a reliable harmonic analysis procedure in all three releases of GOCE models. The space-wise approach, available in two releases, provides similar results as the time-wise approach. The direct approach seems to be highly affected by a-priori information.
Polyaxial figures of the Moon from the lunar reconnaissance orbiter laser altimetry and multi-mission synthesis of the lunar shape
Authors: Iz H. , Shum C. , Dai C. 
Published: June 2012

Polyaxial figures of the Moon from the lunar reconnaissance orbiter laser altimetry and multi-mission synthesis of the lunar shapeLast decade witnessed a plethora of missions to the Moon by China (Chang'E-1 and Chang-E-2), Japan (SELenological and ENgineering Explorer, SELENE), India (Chandrayaan-1) and USA (Lunar Reconnaissance Orbiter), all carried out laser altimetry measurements. This study is a follow up to a series of earlier investigations that produced a number of new models to represent the gross geometric shape of the Moon using Unified Lunar Control 2005, Chang'E-1, and SELENE laser altimetry data using the Lunar Reconnaissance Orbiter laser altimetry measurements. The symmetric and asymmetric polyaxial geometric models derived from Lunar Reconnaissance Orbiter laser altimetry data, namely, three, four and six-axial lunar figure parameters, are compared and contrasted with the corresponding model parameters estimated from the Chang'E-1 and SELENE laser altimetry. All solutions produced geometric shape, orientation parameters, and the parameters of the geometric center of lunar figure with respect to the center of mass of the Moon showing remarkable agreement with each other within 100 m. A combined solution by the fusion of uniformly sampled laser altimetry data from all three missions produced the best estimates for the lunar shape, orientation, and lunar center of figure parameters, and their realistic error estimates.
Review of Mathematical Models of Water Quality
Authors: Ziemińska-Stolarska Aleksandra , Skrzypski Jerzy 
Published: June 2012

Review of Mathematical Models of Water Quality
Water is one of the main elements of the environment which determine the existence of life on the Earth, affect the climate and limit the development of civilization. Water resources management requires constant monitoring in terms of its qualitative-quantitative values. Proper assessment of the degree of water pollution is the basis for conservation and rational utilization of water resources. Water quality in lakes and dams is undergoing continuous degradation caused by natural processes resulting from eutrophication and due to anthropogenic reasons. One of the tools that are used to solve problems of surface water pollution is modelling of changes which take place in lake waters and associated water quality changes. In the last thirty years a rapid development of mathematical modelling of water resources quality has been observed. A number of computer models have been designed which are successfully applied in practice in many countries, including Poland. This paper presents an overview of mathematical models for assessment of water quality in dam reservoirs. Description of the WASP program which will be used for modelling water quality in the Sulejow Reservoir was the focal point.
Screening of the Spatial Distribution of Risk Metals in Topsoil from an Industrial Complex
Authors: Slavík Roman , Julinová Markéta , Labudíková Martina 
Published: June 2012

Screening of the Spatial Distribution of Risk Metals in Topsoil from an Industrial Complex
For the sustainable development of urban areas, it is necessary to identify if environmental pollution exists and where hot spot pollution sources lie. In this study, 280 topsoil samples were collected from an industry estate in Zlin (the Czech Republic). In these samples, the presence of toxic metal was analyzed by energy dispersed X-Ray fluorescence (ED-XRF), and statistical analysis revealed that the major anthropogenic contaminants in the topsoil were Pb, Zn and Sn. Further contaminant analysis by atomic absorption spectrometry (AAS) determined the maximum contents of 28558.47 mg/kg for Pb, 1132.35 mg/kg for Sn and 2865.22 mg/kg for Zn in selected topsoil samples. According to soil pollution index results, the main proportion of topsoil is contaminated, with the possible sources of contamination being traffic and a nearby municipal heating plant. This study proves that the combination of preliminary ED-XRF topsoil analysis, a multivariative statistical approach, AAS analysis and the geographical information system (GIS) is effective and together form a powerful tool for mapping topsoil contamination and conducting an environmental risk assessment.
Theoretical Models for Magnetic Properties of Iron Pnictides Part II: Boson Formalism
Authors: Vujinović M. , Pantić M. , Pavkov-Hrvojević M. , Mali P. 
Published: June 2012

Theoretical Models for Magnetic Properties of Iron Pnictides Part II: Boson FormalismWe analyze theJ1-J2-JcHeisenberg model Hamiltonian by using the Dyson-Maleev representation for spin operators and keeping the terms quadratic in Bose operators (linear spin wave theory). From the resulting Hamiltonian we find the ground state magnetisation and spin wave dispersion by employing the Green's function method. We compare the results with those of random phase approximation analysis from Part I and with experimental data for parent pnictide compounds. Neither of the two approaches gives a completely satisfactory description of the magnetic properties of iron pnictides. We conclude that alterations of the model Hamiltonian are needed to get a better agreement between the theory and experiments.