bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of High Pressure-Dependent Leakoff (PDL) and High Process-Zone Stress (PZS) on Stimulation Treatments and Production
Authors: Ramurthy Muthukumarappan , Towler Brian F. , Harris H. Gordon , Barree Robert D.
Published: November 2013

Hydraulic fracturing continues to be the primary mechanism to produce hydrocarbons out of unconventional reservoirs like tight gas sands, tight coals and shale reservoirs. Over the last few decades it has been studied extensively. However, all the issues that arise during a stimulation treatment have not been understood correctly, yet, leading to costly trial and error approaches to fix them. Assuming that a majority of the perforations (or sleeves) are open and there are no issues with the stimulation fluids, screen-outs and/or pressure-outs during stimulation treatments in any type of reservoir can be attributed to either high pressure-dependent leakoff (PDL) or high process-zone stress (PZS). With high PDL the end result will be a screen-out if it is not addressed properly. However, with high PZS, it is the first indicator and in conjunction with fracture gradient and local stress environment one can understand the reasons for pressure-outs or screen-outs. With high PZS pressure-outs are more common than screen-outs. The objective of this work is to clearly explain and quantify these reservoir-related issues and once identified present solutions such that screen-outs and pressure-outs can be avoided in re–fracture and new well treatments. The effect of damage zone and the fluid lag or negative net stress zones and their contribution to the fracture tip effects will be presented. This work will also clearly show that zones that exhibit high PZS (greater than 0.20 psi/ft), irrespective of the formation type, are economically poor producers.

The tools for identifying these reservoir-related parameters include a diagnostic fracture-injection test (DFIT) and a grid-oriented fully functional 3D fracture simulator with shear decoupling. The relationship between high PZS and the local stress environments and their contribution to issues during a stimulation treatment are presented based on the analysis of 3000 plus DFIT's from the Rockies. Coal, tight gas sand and shale formations are part of the 3000 plus DFIT dataset presented in this work. Examples from coal and shale formations presented earlier by the author are referred in this work. Finally, guidelines (Ramurthy 2012) are presented such that stimulation treatments in high PZS zones that contribute to poor production can be avoided and high PDL zones that lead to good production can be optimized, thereby saving completion costs.
Application of Rate Transient Analysis Workflow in Unconventional Reservoirs: Horn River Shale Gas Case Study
Authors: Virués C.. , Chin A.. , Turco F.. , Anderson D..
Published: November 2013

The Horn River Basin is a shale gas play located along the northern border between British Columbia and the North West Territories, in the Western Canadian Sedimentary Basin. This unconventional reservoir utilizes horizontal wells with multistage fracture completions in order to produce fluids from the very low permeability shale. As with many other emerging shale plays, the Horn River play presents significant challenges to operators who are tasked with understanding, developing and producing the play as optimally as possible. Rate Transient Analysis (RTA) utilizes continuous production and flowing pressure data to characterize the reservoir and completion, for the purposes of reserves assessments, supporting field development and completion strategy and for supporting decisions around capital allocation. It has proved to be a very helpful tool for accelerating the "learning curve" of well performance in new plays, for which well - established best practices do not exist.

The purpose of this work is to illustrate how RTA can be applied in the Horn River, using a reliable, repeatable and technically sound workflow. To accomplish this, daily production data from eight multi-stage horizontal wells in the Horn River was analyzed using standard RTA techniques, including type curves, flowing material balance, specialized plots and analytical models. In addition to the standard approach, a probabilistic approach to RTA using Monte Carlo simulation is also included in this work, to address the significant non-uniqueness that exists in modeling unconventional reservoirs. The findings of this paper will include long term production forecasts, as well as our best estimation of reservoir and completion characteristics.
Scale Effect of 3D Heterogeneous Porous Media on Geo-Fluid Characteristics: Insight from Massively Parallel Lattice Boltzmann Computing
Authors: Gao Jinfang , Xing Huilin , Li Qin , Rudolph Victor , Golding Sue D.
Published: November 2013

Micro-CT scans provide visualization of core samples that can be used to quantify physical properties important for subsurface flow including, as examples, porosity and pore size distribution, pore connectivity and permeability, amongst many others. 3D scans can deliver a very high level of detail, but at a cost of many hours of scan time. This also implies enormous numerical datasets and associated computational processing load. It is therefore important to understand (1) the voxel resolution that is required to retain physical structure fidelity (e.g., pore size and tortuosity) and (2) the smallest sample size that provides reliable and representative transport calculations (e.g., directional permeability and connectivity). As an application example, we analyze a 3D sandstone sample from the Chinchilla area of the Surat Basin comprising a cuboid of 6.6 mm × 6.6 mm × 12.276 mm. The CT image at 6.6 μm voxel resolution generates 1.86 billion grid elements. The work then examines the effect on physical properties and flow simulation of coarsening the voxel resolution, and reducing the physical size of the sample. For each of the different cases relating to voxel size, the major physical properties are evaluated. For different sample sizes at constant (small) voxel size, the fluid flow is modeled using a lattice Boltzmann method (LBM) on multicore supercomputers. The LBM is efficient and convenient for application in parallel computing, which is required to meet the computational resources needs of 3D simulations with large datasets. Comparison of the results obtained at different resolution scales reveals the minimum representative elementary volume (REV) for voxels to characterize the physical features of porous media, and for sample sizes that effectively eliminate boundary effects, capturing and describing the transport phenomena that underpin reservoir analysis.
The Use of Net Pay Concepts in the Exploitation of Shale-Gas Deposits
Authors: Worthington Paul F. , Majid Azlan A.
Published: November 2013

The role of net pay in unconventional reservoirs continues to evolve as a design criterion for reservoir stimulation and well completions. Unlike conventional reservoirs, shale-gas development is not yet at the stage where longstanding net pay protocols have been tried and tested. Therefore, any protocol has to be regarded as being at a pilot stage, especially in view of the pronounced complexity of shale-gas systems. This state of affairs is progressed by adopting a set of net pay criteria and transposing this into a generic petrophysical workflow that interfaces with other key disciplines such as geochemistry and geomechanics. Essential parameters are total organic carbon (in the setting of thermal maturity), fracturability (based on sand volume fraction and thence brittleness), natural fracture density, effective gas permeability, and total porosity as an input to gas in place. The deliverables in the form of target net pay intervals are based on functional cut-offs for each given reservoir system and for different appraisal fronts within the same reservoir system. This is important because different methods of reservoir zonation can result in very different zonal characteristics and associated parametric relationships. The estimation of uncertainty in cut-off specifications and its impact on the resulting net pay intervals has been approached with reference to a commensurate suite of characterizing well logs groundtruthed by core analysis in at least one key well. These considerations lead to specific ranges of cut-offs for immediate application. Thus, the identification of net pay and thence candidate intervals for completion is placed on a quantitative footing. This is an important contribution to development planning in these highly complex unconventional systems.
The Future of Integrated Groundwater and CSG Simulation - Modeling the Surat Basin, Queensland, Australia
Authors: Howell S , Guiton S , de Verteuil D , Campbell L , Vaughan R , Ryan D , Curum N , Coulibaly K
Published: November 2013

This paper will present a workflow describing the integration of hydrogeological and coal-seam gas (CSG) simulation models into one regional 3D numerical flow model covering an area of 197,000km2 of the Surat B asin, Queensland, Australia. The model is designed to allow QGC to further understand and quantify the potential impacts of CSG production from the QCLNG project on the regional groundwater system and to synthesise geological, hydrogeological and engineering data into a one-Earth model.

The model combines knowledge and concepts from previous work including regional-scale single-phase hydrogeological models using MODFLOW, and more local-scale modeling of the Walloon Subgroup using ECLIPSE* 100. It incorporates a hydrogeological conceptualization, a structural and stratigraphic interpretation; property modeling (taking into account public and QGC well data); an ECLIPSE* model and several calibration steps together with the dual-porosity/dual-phase flow behavior inherent to CSG simulation. This paper will demonstrate that via one model, it is possible to simulate the potential effects of CSG production on the groundwater environment, including both the localised dual-phase effects of CSG production and more regional-scale single-phase groundwater movement.
New Integrated Method for Petrophysical Evaluation of Shale Gas: A Case Study in Weiyuan Field
Authors: Yu D. G. , Zhao Z. A. , Wang Y..
Published: November 2013

Exploration for shale gas plays has proved economically viable in North America and has changed the way E&P companies address unconventional reservoirs. After Chinese governments drafted the 12th Five-Year Plan—an initiative designed to rebalance economics in various themes, including energy—gas shale exploration became a hot topic. Shale reservoirs comprise the source, seal, and the reservoir, and production is stimulated by hydraulic fracturing treatments. Modeling that predicts economic productivity and optimal fracture stimulation design is critically based on the detailed, integrated petrophysical evaluation for gas shale plays.

This paper presents an integrated approach to the petrophysical evaluation of resources in the Weiyuan field, the biggest gas shale play in China. Our approach integrates different types of data, including standard formation evaluation logs, geochemical logs and advanced acoustic logs. These data, when combined, provide answers about the reservoir quality and the completion quality. The reservoir quality is established by the information from conventional formation evaluation log and geochemical logs, which include TOC, mineralogy, porosity and gas in place etc. The completion quality is established by the analysis of advanced sonic measurement and resistivity image log, which include geomechanical parameters, natural fractures and induced fractures etc. In this new integrated petrophysical evaluation method, elemental capture spectrometry and advanced acoustic measurements are the keys for estimating reservoir and completion quality. Capture spectrometry measurements provide the accurate mineral content information that is important for ascertaining reservoir quality. Advanced acoustic data can provide the 3D geomechanical parameters and stress estimates required for fracture job design. After integrating reservoir and completion quality, the fracture design is optimized; components include outlining stages, perforation methods, intervals and fracturing fluids.

This integrated evaluation method is being used to establish the petrophysical and geomechanical properties of the Weiyuan gas shale target and also can be applied to other gas shales in China.
An Integrated Disciplinary Approach Towards Hydraulic Fracturing Optimization of Tight Oil Wells in the Ordos Basin, China
Authors: Li Xi Sheng , Wu Liu Pei , Yin Luo , Judd Tobias
Published: November 2013

Exploiting the vast quantities of in-place oil in some of China's large sedimentary basins will require understanding and identifying where new technologies and techniques can be applied to maximize production. Exploration in the Ordos basin in north-central China has demonstrated that tight oil reservoirs, such as the Chang 7 formation, are widely distributed; however, they remain relatively underdeveloped. These reservoirs are buried below the conventional oil layers, differ from them by geological composition, and their thin pay zones and low permeability present development challenges.

As part of a standard exploration and appraisal program, multiple vertical wells have been drilled to characterize the Chang 7 reservoir quality, and many were completed with only one hydraulic fracturing stage. Unfortunately, average hydrocarbon production was often low, and horizontal well completions with multiple transverse hydraulic fracturing treatments were required to obtain commercial flow rates. Part of the integrated workflow developed for the stimulation program requires the capture of reservoir, geological, and geomechanical properties for use in the design of the stages. The perforations were designed to allow for effective fracturing treatments across the lateral and were placed using the abrasive perforating technique. Additionally, one of these vertical wells was used for real-time microseismic fracturing monitoring to evaluate fracture geometry, fracture orientation, and azimuth.

Real-time technology and an integrated workflow effectively increased the understanding of where, when, and how to deploy hydraulic fracturing treatments in the lateral section of the study well. This optimization has resulted in more than an 8-fold increase in production compared to that from vertical wells. Considered a breakthrough, this project has resulted in the planning for additional horizontal wells.
Production Data Analysis of CBM Wells in Surat Basin
Authors: Sugiarto I.. , Jiang J.. , Sharma V.. , Mazumder S..
Published: November 2013

The advancement in Production Data Analysis (PDA) techniques allows the determination of useful reservoir properties such as permeability, drainage radius and original gas in place (OGIP). Recent publications (Clarkson8 et al 2007; Clarkson9 et al 2008) demonstrate the modification of production type-curves and material balance methods for Coalbed Methane (CBM) reservoirs.

One of Arrow Energy's projects is located in the Surat basin in Queensland. The coals intersected in the Surat Basin are members of the Walloon Coal Measures (Walloon Subgroup) which are divided into the Juandah Coal Measure and the Taroom Coal Measure. The Walloon Coal Measure architecture is an inter-bedded coal, siltstone and sandstone sequence. The coals are generally thin with permeability ranging from 5–5000 mD. The Walloon subgroup coals are classified as high volatile bituminous. The Surat Basin has been developed using vertical and deviated wells penetrating the whole sequence. The Surat Basin coal reservoirs can be undersaturated or saturated. In the undersaturated case, single phase flow of water occurs during the early dewatering period. In the saturated case, two-phase flow of gas and water occurs at initial production.

Arrow Energy has produced from the Surat Basin since 2006. The large amount of production data serves as a valuable source for PDA. Results indicate that the flow regime is dominated by linear flow during the transient period followed by boundary-dominated flow. A flowing material balance method is used to validate reservoir parameters from well simulation history matching and type-curves methods. The reservoir parameters such as permeability, drainage radius and OGIP obtained from all the methods are compared and quality checked. The decline curve analysis (DCA) method is performed on wells which have entered boundary-dominated flow to obtain the estimated ultimate recovery (EUR) and recovery factor.

The PDA study is carried out for approximately 250 existing production wells in the Surat Basin. The reservoir parameters obtained from the various methods agree with one another, indicating reliable results. The permeability values obtained from this study are within the range of the Drill Stem Test (DST) results in the Surat Basin.
Water Saturation Evaluation of Murteree and Roseneath Shale Gas Reservoirs, Cooper Basin, Australia Using Wire-line Logs, Focused Ion Beam Milling and Scanning Electron Microscopy
Authors: Ahmad Maqsood , Haghighi Manouchehr
Published: November 2013

Roseneath and Murteree organic shales in Nappamerrie trough are part of most prolific unconventional gas reservoirs in Cooper Basin, South Australia. The cumulative effect of rocks, minerals, fluids and organic content in these shale gas reservoirs has been investigated and incorporated using Archie's equation and other resistivity models such as Indonesian, Siamandoux and total shale model for water saturation evaluation. In this study, wireline logs have been calibrated with QEMSCAN and FIB/SEM images.

We have found that the shale content in Murteree formation is around 50% using QEMSCAN analysis. Also, it is found that using Steiber formula, the shale volume is close to 50%. Therefore, the Steiber formula is selected as the proper correlation to estimate shale content for Murteree formation. Furthermore, the free porosity of Roseneath and Murteree shale was measured to be 2% based on QEMSCAN and CT scanning. Then, Using Wyllie formula for sonic porosity with Hilchie's correction factor, the porosity was also determined close to 2%. Thus, Wyllie formula with Hilchie's correction factor was also found to be the appropriate correlation for porosity calculation in Roseneath and Murteree shale.

For water saturation, both Simandoux and Indonesian correlations were shown to give reasonable results. However, it is found that if free porosity is more than 9%, both total shale and Archie models can also give acceptable results. The sensitivity of true resistivity in water saturation calculation was investigated as well. Furthermore, the evaluation of Archie's parameters (cementation exponent, m, tortuosity factor, a, and saturation exponent, n) were examined. Also, FIB/SEM images show that brine and organic matters are both attached to the clay particles which have caused a modified true resistivity for the shale.
Implementation of Wireline Formation Testing Configuration for the Evaluation of Coal Seam Gas Plays in Surat and Bowen Basins in Australia
Authors: Pourabed Hamid Reza , Harfoushian Jack H. , North Tim
Published: November 2013

A coal seam gas (CSG) to liquefied natural gas (LNG) project in Queensland, Australia, has an active exploration and appraisal program in support of future development activities. Critical to exploration and appraisal is the evaluation of permeability, skin, and reservoir pressure. Drill stem testing (DST) has been the most common form of evaluation since the inception of the industry in Queensland over the last 10 years. DSTs commonly used in the CSG industry are modified ‘slug’ tests in which a water cushion provides hydrostatic backpressure on the formation to reduce the likelihood of gas break-out and two-phase flow. Although DSTs have become an industry-accepted method for evaluating permeability, skin, and extrapolated reservoir pressure, there are some disadvantages to this approach.

A new wireline formation testing technique addresses the evaluation objectives of CSG testing in the Surat and Bowen basins. In addition to efficiency and cost-effectiveness, the approach provides additional testing flexibility; this includes the ability to manage a broad range of drawdown and inflow rates, extending its applications from very low to high permeability coals. Additional applications include step-rate tests, across both the Walloon coal measures of the Surat basin and the Bowen basin's Bandanna formation.
Evaluating Treatment Methods for Enhancing Microfracture Conductivity in Tight Formations
Authors: Nguyen Philip D. , Vo Loan K. , Mock Brian D. , Loghry Ray A.
Published: November 2013

Most microfractures generated within a complex fracture network return to a closed state soon after the release of hydraulic pressure, unless propping agent has been successfully placed inside these fractures. However, particle size and proppant density control the success of such placement. This paper presents the results of a laboratory study that demonstrates and quantifies the effectiveness of methods for enhancing and sustaining the conductivity of microfractures in tight formations.

This study examines the conductivity performance of placing microproppant particulates compared to performing an acid fracturing treatment in a created fracture. Various shale core samples were obtained and split along the core length to create artificial fracture faces. Before placement of microproppant into the fracture, the split core fracture faces were first treated with an aqueous-based surface modification agent (ASMA) solution that creates tacky sites to capture any proppant exposed to the treated surface and to mitigate proppant settling. This was then followed by exposure to microproppant slurry. The core halves were then reassembled for core flow testing under closure stress. An acid fracturing treatment administered through the split core fracture involved injection of a sequence of materials that slowly releases organic acid and inorganic acid to etch fracture faces, forming gaps or channels within the fractures, by allowing acid to efficiently dissolve the solid structures on the split core fracture faces.

The experimental results are presented by examining the reliability of ASMA treatments to mitigate proppant settling. A permeability comparison of the fractured cores, with and without treatment with ASMA and proppant slurry, demonstrates a dramatic increase to permeability in the treated cores. Permeability measurements of acidized split cores also demonstrate a drastic improvement compared to those of untreated split cores, indicating the importance of maintaining acid activity to maximize fracture etching effectiveness.
Technology Advances in the Understanding of Reservoir Performance in the Woodford Shale Gas Field, Arkoma Basin, USA
Authors: Carragher Paul , French Samuel
Published: November 2013

Since drilling of the very first horizontal well in 2005, more than 1500 horizontal wells have been brought into production in the Devonian-aged Woodford shale gas field in the Arkoma Basin of Oklahoma, USA. In 2008, through a combination of trades and purchases of acreage, BP consolidated its position as the first Major International Oil Company in the Woodford field and has subsequently drilled more than 200 horizontal wells and gained a working interest in a further 981 wells.

Across the field area of more than 3000sqkm, initial stabilised production rates range from 2 to 8 million standard cubic feet per day and estimated per-well recovery (EUR) ranges from 2 to 7 bcf per well. Improvement in the prediction of this highly variable well performance in this unconventional reservoir is seen as critical in the economic design of the field development. To assist in understanding and prediction of this large variation in well performance, BP has designed and applied a number of evaluation technologies that have enabled the integration of well operations data and reservoir characteristics. In a core operations area covering approximately 340sqkm, BP has conducted closely controlled operational experiments in numerous aspects of reservoir management and well completion. These have included research in determination of optimal well spacing, selection of horizontal well lateral lengths and variation in frac stage spacing. Through analysis of all the available production and operational data, it has been possible to construct a Performance Indicator (PI) tool through which production variations across the field could be visualized. This approach has demonstrated that the variation of well performance is best related to geological or more general subsurface trends rather than well-completion or other operational design issues. Integration of these data has enabled BP to significantly improve the accuracy of production forecasts for both short and long-term field performance. Critical elements in the success of this project include key advances in understanding the importance of subsurface structural complexity, the impact and prediction of local variation in the shale reservoir characteristics and the careful management of changes in well design and completion methods. Together, these have enabled the accurate prediction of reservoir geological risk and allowed better definition of specific areas of the field where well performance could be expected to be at its best. Direct benefits of this integrated evaluation have included the the prediction of reservoir performance of new infill wells, identification of areas in the field where development well spacing could be reduced and gaining manangement support for a proposed refraccing programme.
Acid Stimulation of Onnagawa Tight Oil Formation in Ayukawa Field, Japan
Authors: Kamitsuji Ryohei , Okajima Takuro , Yokoi Satoru
Published: November 2013

The Onnagawa shale is Miocene, bio-siliceous and known as the main source rock in Japan. Frequent and intensive oil shows are observed through the Onnagawa formati on around the Ayukawa field. The thickness of this layer is about 1,600 ft around this field. The porosity is around 30%. The Permeability ranges from 0.01 mD to 1 mD. Onnagawa is considered to be similar to Monterey shale. Acidizing in Monterey shale has a long history of success. Though the production is generally improved by removing the drilling and completion damage, unexpected favorable responses from low permeability rock are also reported. These improvements are considered to result from dissolving the calcite and clay minerals in natural fractures and enhancing the wellbore connection into natural fracture network. The acid stimulation test was conducted to verify this acidizing effect in Onnagawa shale. The target well showed very low productivity. The perforation interval is 40 m (130 ft) long. Weakly fracture distribution is detected from wellbore images. No skin and low permeability on the order of 0.01 mD were estimated from the well test analysis. So the objective of this stimulation is not the removal of drilling and completion damage, but the improvement of natural fracture conductivity. The stimulation program was comprised of three stages that alternated 15% HCl preflush, 12% HCl + 3% HF main acid, NH4Cl overflush, and particulate diverting agent. The volumes of preflush and main acid were 80 gallon/foot each. The significant pressure drops indicating the injectivity improvement were observed during both preflush and main acid injection. The oil production dramatically increased from 1.5 kl/day (10 BOPD) to 50.0 kl/day (315 BOPD). The productivity index also increase from 0.3 kl/day/MPa to 45.0 kl/day/MPa. This test is the first successful stimulation of the tight oil formation in Japan.
Fracturing Technology of Coalbed Methane in Qinshui Basin
Authors: Xianpeng Jin , Zhongxiao Lan , Chengyu Lan , Wenjun Wang , Rui Wang , Donghong Zheng , Tao Wu , Taizhen Yue , Hongyan Zhou , Haifei Wen
Published: November 2013

Coalbed methane (CBM) reservoir with Lower Young's Modulus, higher Poisson's ratio, and lower permeability is different from conventional sandstone reservoir in composition, structure, tectonic and mechanical property, therefore, the fracturing technique and mechanism are much more different. Qinshui Basin located in the southeast of Shanxi Province is of simple synclinorium structure, less of faults, and it has up to 10 layers of coal seams, total thickness 1.2–23.6m and the maximum 6.5m. By far, No.3 and No.15 coal seam of Qinshui Basin have been developed for CBM production, depth from 600m to 900m, and the rank of the coal are mainly meager-lean coal and anthracite. No.3 coal seam of Shanxi Formation is 0.53–7.84m thick, gas content 11.94m3 / t on average, mainly semi-bright coal and semi-dull coal, reservoir pressure gradient 0.7149MPa/100m on average, well-testing permeability 1.589mD on average, Langmuir volume 39.03m3/t on average, Langmuir pressure 2.902 MPa. No.15 coal seam of Taiyuan Formation is 0.6– 9.9m thick, gas content 12.45m3/t on average, mainly bright coal and semi-bright coal, reservoir pressure gradient 0.7727MPa/100m on average, well-testing permeability 1.14mD on average, Langmuir volume 40.91m3/t, Langmuir pressure 2.5417 MPa. Through optimizing the fracturing designs, evaluating fracturing fluid systems and implementing control measures, a set of ‘network fracturing’ treatments with casing injection, high displacement and activated water fracturing fluid as key techniques were developed and applied successfully for coalbed methane in Qinshui Basin with the rate of success more than 95%. The study also showed that the multi-fracture treatment by plugging perforation with plastic ball can be used in separate layer treatment of coalbed methane reservoir. Furthermore, variable injection rate and slug injection of proppant can also be used to achieve the purpose of controlling extension of fractures. In five years,1264 layers (at 1096 wells) were treated by using this fracturing technology in QinShui Basin, and the gas production rate is over 2000 m3/d in 60% fracturing wells.
Microstructure Characterization for a Shale Gas Reservoir by Combining Visualization Technique and Physical Measurement
Authors: Wei Chenji , Qin Guan
Published: November 2013

We characterize the nano-pore structure of the Longmaxi Shale that is a Lower Silurian marine shale play in China with huge potentials according to preliminary explorations. Scanning Electron Microscope (SEM) is used to visualize the pore structure of the samples. In addition, we present nitrogen adsorption experimental results and other petrophysical data (including total organic content, mineralogy, and on-site gas content measurement) for core samples from the target layer of the Longmaxi Shale. Nitrogen adsorption experiments are conducted on the samples from the target layer of the Longmaxi Shale and measure the nano-pores with diameter ranges from 2 nm to 100 nm at 77°K. Adsorption and desorption isotherms are obtained. BET and BJH models are used to determine the specific surface area and pore-size distribution respectively. Results of adsorption experiments and SEM images indicate that the pore structure of Longmaxi Shale is complex and has multi-scale pore dimensions. The micropores plus the mesopores contribute 90.8% to the total nanopore volume and 99.4% to the specific surface area respectively. Based on our analysis and discussion, nanopores contribute the majority of gas storage space. Organic matters play an important role in governing the nano-pores volume and specific surface area. Clay content and brittle minerals do not have direct relationship with the nanopore volume and the specific surface area, however, they may also provide pore spaces those may be measured by the nitrogen adsorption experiment, such as pores with micronscale or micro-fractures.
Understanding Reservoir Properties through High-Definition Microresistivity Images in Horizontal Shale Oil Wells Drilled with OBM in China
Authors: Yun Xie , Huijun Hou , Hui Guan , Laronga Robert J. , Zhongbin Xin
Published: November 2013

Oil-base mud (OBM) is an increasingly popular drilling fluid used to protect the wellbore stability in horizontal wells drilled in China targeting shale gas or oil. In these reservoirs, an in-depth understanding of fracture attributes is critical for stimulation design and well placement optimization, but the resolution and coverage of traditional imaging technology for OBM limits the extent to which this objective may be achieved. A microresistivity imager achieving resolution and coverage similar to established technology for conductive water-base mud (WBM), fully capable to distinguish fractures and formation structural features in OBM, has been a much needed technology development to provide critical insight required for shale oil exploration.

The paper presents a case study from the Bohai Bay basin in Eastern China, where oil shale formed in the faulted depression lacustrine sub-basins of the Lower Oligocene. One horizontal exploration shale oil well was drilled with OBM for reservoir evaluation. Only a gamma ray log and new, high-definition microresistivity image logs were acquired due to difficult operating conditions, which made it a great challenge to interpret reservoir properties and optimize stimulation design. Fortunately, two nearby vertical wells were drilled and evaluated in detail prior to design of the horizontal well, making use of geochemical, advanced acoustic, and microresistivity image logs to optimize placement of the lateral, thus providing a reference for estimation of the reservoir properties.

The results showed that the new, high-definition resistivity imaging tool gives detailed images suitable for full fracture and structure characterization, and that such high-quality images are feasible even in wells drilled with OBM. Interpretation of high-definition microresistivity images to build a near-well structural model provided a framework for correlation of fracture, reservoir, and mechanical properties from the vertical wells to the horizontal well. This provided a clear picture as to how the lateral well trajectory progressed stratigraphically within the shale section, as well as the distribution of the fractures, reservoir and non-reservoir rocks, total organic carbon (TOC) and minimum geo-stress along the well trajectory. Subsequently, this rich model provided the needed critical inputs to decide how and where to complete the well with an optimized stimulation design.
Multidrug-resistant tuberculosis in Uzbekistan: results of a nationwide survey, 2010 to 2011
Authors: Ulmasova D J , Uzakova G , Tillyashayhov M N , Turaev L , van Gemert W , Hoffmann H , Zignol M , Kremer K , Gombogaram T , Gadoev J , du Cros P , Muslimova N , Jalolov A , Dadu A , de Colombani P , Telnov O , Slizkiy A , Kholikulov B , Dara M , Falzon D
Published: November 2013

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Epidemiological investigation of Pseudomonas aeruginosa isolates from a six-year-long hospital outbreak using high-throughput whole genome sequencing
Authors: Snyder L A , Loman N J , Faraj L A , Levi K , Weinstock G , Boswell T C , Pallen M J , Ala’Aldeen D A
Published: November 2013

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Study of a measles outbreak in Granada with preventive measures applied by the courts, Spain, 2010 to 2011
Authors: Navarro E , Mochón M M , Galicia M D , Marín I , Laguna J
Published: November 2013

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Arsenic Contamination in the Deep and Shallow Groundwater of Kathmandu Valley, Nepal
Authors: Shrestha SM , Rijal K , Pokhrel MR
Published: November 2013

Scientific World, Vol. 11, No. 11, July 2013, page 25-31 DOI: http://dx.doi.org/10.3126/sw.v11i11.8548
Mutations or Exclusion: An Uncommon Parentage Assessment Case
Authors: Jha Dinesh Kumar , Rijal Jiwan Prasad , Tuladhar Bhinu Shova , Pokharel Basanta Raj
Published: November 2013

Scientific World, Vol. 11, No. 11, July 2013, page 74-76 DOI: http://dx.doi.org/10.3126/sw.v11i11.8556
Bacterial Contamination in the Surface Waterbodies in Sagarmatha National Park and Buffer Zone, Nepal
Authors: Ghimire Narayan Prasad , Caravellol GU , Jha Pramod Kumar
Published: November 2013

Scientific World, Vol. 11, No. 11, July 2013, page 94-96 DOI: http://dx.doi.org/10.3126/sw.v11i11.8560
Asymbiotic Seed Germination and Plantlet Development of Coelogyne Fuscescens Lindl., A Medicinal Orchid of Nepal
Authors: Koirala Dharma , Pradhan Shreeti , Pant Bijaya
Published: November 2013

Scientific World, Vol. 11, No. 11, July 2013, page 97-100 DOI: http://dx.doi.org/10.3126/sw.v11i11.8561
Spectrophotometric Determination of Total Iron in Rice and Maize Samples
Authors: Rajbhandari Armila , Subedi Tara
Published: November 2013

Scientific World, Vol. 11, No. 11, July 2013, page 101-104 DOI: http://dx.doi.org/10.3126/sw.v11i11.8562
Control of Cell Differentiation by Mitochondria, Typically Evidenced in Dictyostelium Development
Authors: Maeda Yasuo , Chida Junji
Published: November 2013

In eukaryotic cells, mitochondria are self-reproducing organelles with their own DNA and they play a central role in adenosine triphosphate (ATP) synthesis by respiration. Increasing evidence indicates that mitochondria also have critical and multiple functions in the initiation of cell differentiation, cell-type determination, cell movement, and pattern formation. This has been most strikingly realized in development of the cellular slime mold Dictyostelium. For example, the expression of the mitochondrial ribosomal protein S4 (mt-rps4) gene is required for the initial differentiation. The Dictyostelium homologue (Dd-TRAP1) of TRAP-1 (tumor necrosis receptor-associated protein 1), a mitochondrial molecular chaperone belonging to the Hsp90 family, allows the prompt transition of cells from growth to differentiation through a novel prestarvation factor (PSF-3) in growth medium. Moreover, a cell-type-specific organelle named a prespore-specific vacuole (PSV) is constructed by mitochondrial transformation with the help of the Golgi complex. Mitochondria are also closely involved in a variety of cellular activities including CN-resistant respiration and apoptosis. These mitochondrial functions are reviewed in this article, with special emphasis on the regulation of Dictyostelium development.
1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) Signaling Capacity and the Epithelial-Mesenchymal Transition in Non-Small Cell Lung Cancer (NSCLC): Implications for Use of 1,25(OH)2D3 in NSCLC Treatment
Authors: Upadhyay Santosh , Verone Alissa , Shoemaker Suzanne , Qin Maochun , Liu Song , Campbell Moray , Hershberger Pamela
Published: November 2013

1,25-dihydroxyvitamin D3 (1,25(OH)2D3) exerts anti-proliferative activity by binding to the vitamin D receptor (VDR) and regulating gene expression. We previously reported that non-small cell lung cancer (NSCLC) cells which harbor epidermal growth factor receptor (EGFR) mutations display elevated VDR expression (VDRhigh) and are vitamin D-sensitive. Conversely, those with K-ras mutations are VDRlow and vitamin D-refractory. Because EGFR mutations are found predominately in NSCLC cells with an epithelial phenotype and K-ras mutations are more common in cells with a mesenchymal phenotype, we investigated the relationship between vitamin D signaling capacity and the epithelial mesenchymal transition (EMT). Using NSCLC cell lines and publically available lung cancer cell line microarray data, we identified a relationship between VDR expression, 1,25(OH)2D3 sensitivity, and EMT phenotype. Further, we discovered that 1,25(OH)2D3 induces E-cadherin and decreases EMT-related molecules SNAIL, ZEB1, and vimentin in NSCLC cells. 1,25(OH)2D3-mediated changes in gene expression are associated with a significant decrease in cell migration and maintenance of epithelial morphology. These data indicate that 1,25(OH)2D3 opposes EMT in NSCLC cells. Because EMT is associated with increased migration, invasion, and chemoresistance, our data imply that 1,25(OH)2D3 may prevent lung cancer progression in a molecularly defined subset of NSCLC patients.
An Ionic Liquid Solution of Chitosan as Organocatalyst
Authors: Heckel Tatjana , Konieczna Dagny , Wilhelm René
Published: November 2013

Chitosan, which is derived from the biopolymer chitin, can be readily dissolved in different ionic liquids. The resulting homogeneous solutions were applied in an asymmetric Aldol reaction. Depending on the type of ionic liquid used, high asymmetric inductions were found. The influence of different additives was also studied. The best results were obtained in [BMIM][Br] without an additive.
Recent Approaches to Controlling the Nanoscale Morphology of Polymer-Based Bulk-Heterojunction Solar Cells
Authors: Hammed Wasiu , Yahya Rosiyah , Bola Abdulra'uf , Mahmud Habibun
Published: November 2013

The need for clean, inexpensive and renewable energy has increasingly turned research attention towards polymer photovoltaic cells. However, the performance efficiency of these devices is still low in comparison with silicon-based devices. The recent introduction of new materials and processing techniques has resulted in a remarkable increase in power-conversion efficiency, with a value above 10%. Controlling the interpenetrating network morphology is a key factor in obtaining devices with improved performance. This review focuses on the influence of controlled nanoscale morphology on the overall performance of bulk-heterojunction (BHJ) photovoltaic cells. Strategies such as the use of solvents, solvent annealing, polymer nanowires (NWs), and donor–acceptor (D–A) blend ratios employed to control the active-layer morphologies are all discussed.
Microbial Profile of Soil-Free versus In-Soil Grown Lettuce and Intervention Methodologies to Combat Pathogen Surrogates and Spoilage Microorganisms on Lettuce
Authors: Sirsat Sujata , Neal Jack
Published: November 2013

Aquaponics is an effective method to practice sustainable agriculture and is gaining popularity in the US; however, the microbial safety of aquaponically grown produce needs to be ascertained. Aquaponics is a unique marriage of fish production and soil-free produce (e.g., leafy greens) production. Fish are raised in fresh water tanks that are connected to water filled beds where fruits and vegetables are grown. The fish bi-products create nutrient-rich water that provides the key elements for the growth of plants and vegetables. The objective of this study was to perform a comparative analysis of the microbial safety and quality of aquaponic lettuce and soil grown lettuce (conventional, bagged, certified organic, and field lettuce). Following this, an intervention study was performed to combat foodborne pathogen surrogates (Salmonella and E. coli), spoilage, and fecal microorganisms using 2.5% acetic acid. The results of the comparative analysis study showed that aquaponically grown lettuce had significantly lower concentration of spoilage and fecal microorganisms compared to in-soil grown lettuce. The intervention study showed that diluted vinegar (2.5% acetic acid) significantly reduced Salmonella, E. coli, coliforms, and spoilage microorganisms on fresh lettuce by 2 to 3 log CFU/g. Irrespective of growing methods (in-soil or soilless), it is crucial to incorporate good agricultural practices to reduce microbial contamination on fresh produce. The intervention employed in this study can be proposed to small farmers and consumers to improve quality and safety of leafy greens.
Strategic Voting in Heterogeneous Electorates: An Experimental Study
Authors: Tyszler Marcelo , Schram Arthur
Published: November 2013

We study strategic voting in a setting where voters choose from three options and Condorcet cycles may occur. We introduce in the electorate heterogeneity in preference intensity by allowing voters to differ in the extent to which they value the three options. Three information conditions are tested: uninformed, in which voters know only their own preference ordering and the own benefits from each option; aggregate information, in which in addition they know the aggregate realized distribution of the preference orderings and full information, in which they also know how the relative importance attributed to the options are distributed within the electorate. As a general result, heterogeneity seems to decrease the level of strategic voting in our experiment compared to the homogenous preference case that we study in a companion paper. Both theoretically and empirically (with data collected in a laboratory experiment), the main comparative static results obtained for the homogenous case carry over to the present setting with preference heterogeneity. Moreover, information about the realized aggregate distribution of preferences seems to be the element that best explains observed differences in voting behavior. Additional information about the realized distribution of preference intensity does not yield significant further changes.
Did We Get Our Money’s Worth? Bridging Economic and Behavioral Measures of Program Success in Adolescent Drug Prevention
Authors: Griffith Kevin , Scheier Lawrence
Published: November 2013

The recent U.S. Congressional mandate for creating drug-free learning environments in elementary and secondary schools stipulates that education reform rely on accountability, parental and community involvement, local decision making, and use of evidence-based drug prevention programs. By necessity, this charge has been paralleled by increased interest in demonstrating that drug prevention programs net tangible benefits to society. One pressing concern is precisely how to integrate traditional scientific methods of program evaluation with economic measures of “cost efficiency”. The languages and methods of each respective discipline don’t necessarily converge on how to establish the true benefits of drug prevention. This article serves as a primer for conducting economic analyses of school-based drug prevention programs. The article provides the reader with a foundation in the relevant principles, methodologies, and benefits related to conducting economic analysis. Discussion revolves around how economists value the potential costs and benefits, both financial and personal, from implementing school-based drug prevention programs targeting youth. Application of heterogeneous costing methods coupled with widely divergent program evaluation findings influences the feasibility of these techniques and may hinder utilization of these practices. Determination of cost-efficiency should undoubtedly become one of several markers of program success and contribute to the ongoing debate over health policy.
Age-Related Changes in Physical Fall Risk Factors: Results from a 3 Year Follow-up of Community Dwelling Older Adults in Tasmania, Australia
Authors: Bird Marie-Louise , Pittaway Jane , Cuisick Isobel , Rattray Megan , Ahuja Kiran
Published: November 2013

As the population ages, fall rates are expected to increase, leading to a rise in accidental injury and injury-related deaths, and placing an escalating burden on health care systems. Sixty-nine independent community-dwelling adults (60–85 years, 18 males) had their leg strength, physical activity levels and their annual fall rate assessed at two timepoints over three years, (summer 2010 and summer 2013) monitoring balance. Force platform measures of medio-lateral sway range increased significantly under conditions of eyes open (mean difference MD 2.5 cm; 95% CI 2.2 to 2.8 cm) and eyes closed (MD 3.2 cm; 95% CI 2.8 to 3.6 cm), respectively (all p < 0.001) indicating worsening static balance control. Dynamic balance showed similar changes (p < 0.036). Leg strength was not significantly different between visits (p > 0.26). Physical activity reduced significantly (MD −909 Cal/week; 95% CI −347 to −1,470 Cal/week; p = 0.002) during the course of the study. Participants maintained aerobic activities, however resistance and balance exercise levels decreased non-significantly. The likelihood of falling was higher at the end of the study compared to the first timepoint (odds ratio 1.93, 95% CI 0.94 to 3.94; p = 0.07). Results of this study indicate that despite maintenance of leg strength there was an increase in medio-lateral sway over a relatively short time frame, with higher than expected increases in fall rates.