bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Modeling of the Viscous Drive in Oil-wet Naturally Fractured Reservoirs
Authors: Romero Rene , Behr Aron 
Published: April 2018

Abstract
Recent experiments have shown that gels can promulgate the viscous drive recovery mechanism in fractured oil-wet matrix cores. The large viscosity of gels can increase the pressure gradient in the fractured network, generating higher local pressures in the fractures that can overcome the capillary entrance pressure of the oil-wet matrix. When that occurs, the water leaking-off from the gel invades the matrix and displaces the oil to the fractures, promoting the viscous drive as the dominant recovery mechanism. The goal of this research is to comprehend whether the viscous drive recovery mechanism could enhance the oil recovery in oil-wet NFR under realistic conditions and furthermore to determine the range of applicability. The laboratory tests executed by Brattekås et al. (2013), where the gel was injected at high velocity in the fracture provoking matrix invasion, allowed generating a conceptual model of the process that was adapted in a numerical reservoir simulator to reproduce the experiments. As a step forward, the lab-scale simulations are scaled up to field conditions to analyze the phenomenon in real reservoirs. Multiple simulations were performed to evaluate the influence of different parameters such as the gel viscosity, the velocity of injection and the matrix block size on the recovery rate and the ultimate recovery factor. The simulation results demonstrated on the one hand that in smaller matrix blocks higher values of velocity-viscosity are needed to initiate the process, and additionally the capillary end-effect significantly affects oil production. On the other hand, in the larger matrix blocks the recovery time is considerably longer and could be unrealistic for practical applications. The dimensionless criterion controlling this process is derived as the viscous-capillary ratio relating the differential pressure along the fracture to the capillary pressure of the oil-wet matrix. To provoke the matrix invasion by the viscous drive, this dimensionless number should overcome a critical value which was estimated for this study. The novelty of this work has a significant contribution for the EOR implementation in oil-wet NFR. It is demonstrated that the viscous drive recovery mechanism can have a strong contribution on oil recovery.
Comprehensive Evaluation of the Dynamic Sealing Capacity of Clayey Caprocks in a Large Underground Gas Storage
Authors: Sun Junchang , Zheng Dewen , Wang Jieming , Liu Jiandong , Shi Lei , Xu Hongcheng , Li Chun , Zhong Rong , Zhao Kunshan 
Published: April 2018

Abstract
An effective caprock is crucial for safe operation of an underground gas storage (UGS). However, the caprock's initial seal capacity can be changed due to many factors such as micro-deformation of the caprock's pore structure and fatigue damage under cyclic loading caused by UGS annual storage which may all lead to gas leakage. Consequently, the caprock's dynamic sealing capacity including capillary sealing effciency and mechanical integrity under alternating stress must be comprehensively evaluated.
A total of 21 clayey caprock plugs drilled from the HB large UGS in western China were prepared to perform laboratory tests. Nitrogen breakthrough (BT) pressure was both measured before and after 50 cycles’ loading-unloading on the fully kerosene-saturated plugs. Specially, the cyclic amplitude was designed based on the UGS planned operational pressure bounds and local dynamic in-situ stresses. Triaxial compression fatigue and subsequent failure tests were conducted to investigate the strain dynamic evolution and its effect on the mechanical behaviors of clayey caprocks. Seventeen sandstone reservoir plugs were also selected to carry out mechanical tests as a comparison.
Experimental results indicate that the BT pressure of the HB caprock ranges from 3.88 to 8.79MPa which is much higher than the critical value (~2MPa) for the HB trap seal. Average reduction of the BT pressure is 14.8% after 50 cycles’ loading demonstrating that the alternating in-situ stresses may have a relatively minor effect on the capillary sealing capacity of the HB UGS caprock. This finding is also supported by the mechanical tests that the maximum cyclic loading is always below the yield point of the HB caprock. Compaction is the main deformation behavior and shear expansion has not occurred within the disturbed in-situ stresses variation during the HB UGS operations according to the dynamic evolution of the axial and lateral strain. However, the stress-strain curves exhibit significant hysteresis especially within the first several cycles and the plastic strain continuously develops. The average cumulative plastic strain is around 0.14% after 50 cycles’ loading which is much lower than the 1% benchmark of caprock failure suggested by Schlumberger. However, the cyclic loading has a more severe weakening effect on the caprock mechanical strength parameters and it cannot be neglected in geomechanical simulation compared with the sandstone reservoir plugs.
This study gives an in-depth understanding of the dynamic capillary sealing capacity and mechanical properties of the clayer caprocks under cyclic loading-unloading. Based on the above experimental finds, the more accurate evaluation will be obtained through 3D geomechanical model simulation.
Open Source Toolkit for Micro-Model Generation Using 3D Printing
Authors: Seers Thomas D. , Alyafei Nayef 
Published: April 2018

Abstract
Here, we present an open source toolkit for the generation of micro-fabricated transparent models of porous media (micro-models) from image datasets using optically transparent 3D polymer additive manufacturing (3D printing or sintering). These micro-models serve as both a research and pedagogical tool, facilitating the direct visualization of drainage and imbibition within quasi-2D porous media, generated from a range of image modalities (e.g. thin section micrographs, μCT orthoslices, and conventional digital photography).
Written in the MATLAB™ language and readily extendible, this open source toolkit is intended to act as enabler for community research for the study of transport in a porous media. In this work, we demonstrate the toolkit's capabilities using X-ray micro-tomographic image data. Orthoslices of scanned rocks (Berea sandstone) are cropped and segmented (binarized), then used to generate watertight 3D meshes of micro-models, which are exported as stereolithography (.stl) files: a native format to most commercially available 3D printers. The generated models are self-contained, with the inlet-outlet ports, synthetic rock matrix and transparent viewing panels printed as a single integrated unit.
The open source toolkit presented here offers a more accessible and adaptive approach to micromodel fabrication, when compared to conventional etched/molded equivalents, which require highly specialized manufacturing facilities. We suggest that the availability of such a toolset will act as a major enabler for community research in porous media transport phenomena, allowing experimental quasi-2D pore networks to be generated rapidly and cost effectively using readily available additive manufacturing technologies.
Reservoir and Economic Uncertainties Assessment for Recovery Strategy Selection: Use of Stochastic Decision Trees
Authors: Vincent Philippe , Schaaf Thomas 
Published: April 2018

Abstract
The field development phase prior to investment sanction is characterized by relatively large uncertainties at the time important decisions have to be made. It is, for instance, crucial to select an appropriate recovery strategy (depletion or injection) to obtain optimal hydrocarbon cumulative production whilst ensuring good profitability of the project. Evaluation of reservoir as well as economic uncertainties and quantification of their impact are needed before the field development concept selection.
This paper describes how to stochastically assess reservoir and economic uncertainties and the screening process used to select the best recovery strategy. The chosen methodology is the combination of uncertainty studies, including both continuous, discrete and controllable parameters. The different screened scenarios are combined in a stochastic decision tree, built-up through decision and chance nodes, to establish a distribution of recoverable volumes and rank the recovery strategies given a chosen criterion. A second uncertainty study is performed by adding economic uncertainties to the initial set of reservoir uncertain parameters. Eventually a new decision tree is established and scenarios ranked using economic criteria.
The application of this methodology to an oil field from the Norwegian continental shelf and how recovery strategies are ranked are presented in this paper. The described methodology has exhibited the risks and uncertainties carried by the project, as it was possible to rank the different solutions based on the dispersion of the recoverable volumes distribution and/or on the net present value (NPV). In the context of a marginal or large capex project, a robust P90 case is required and this may therefore influence the choice of the recovery strategy. For instance, a scenario yielding the largest hydrocarbon volume may not be selected because it requires too many wells and/or too large investment if one of these criteria is defined as the most important. In addition, the combination of uncertainty studies enabled a full economic evaluation covering the entire recoverable volumes distribution whereas in many projects economic evaluation is focused on the P90, Mean and P10 scenarios.
The two-step integrated approach allows a decision to be made whilst taking into account both reservoir and economic aspects. Having a combined stochastic approach to the reservoir and economic uncertainties avoids a biased decision. All cases are stochastically covered and screened using a systematic and unified methodology that gives the same weight to each scenario.
A New Method for Economic Prediction of Carbonate Reservoirs Based on Expert Library and Small Database
Authors: Chen Wenbin , Jiang Hanqiao , Li Junjian , Jiang Shan , Yang Hanxu , Qiao Yan 
Published: April 2018

Abstract
The karst caves and fractures are widely developed in carbonate reservoirs, which results in strong spatial heterogeneity. So the parameters obtained from its cores and numerical simulation are limited to reflect its production situation of the entire reservoir, which causes that the traditional economic prediction method for carbonate reservoirs has a high risk. To solve these problems, this paper proposes a new method to accomplish the economic prediction based on expert library and oilfield database, named Delphi-AHP-TOPSIS-MLS-FNPV complex algorithm (DATMF). DATMF method can take account of geological factors, such as sedimentary facies, reservoir types, the characteristics and heterogeneity of caves and fractures. It also considered the impact of production factors on the economic prediction, such as oil production, annual decline rate of production, well spacing density. The process of the DATMF method is as follows: First, establishing a set of hierarchical structure to describe the carbonate reservoirs in the database; Secondly, optimizing the database and analyzing the data based on the expert library; Thirdly, predicting the key development parameters of the new reservoir according to its geological data; Finally, substituting these parameters into the future net present value (FNPV) method to complete the economic prediction of the new carbonate reservoir. Through the calculation example of T7-444CH reservoir, it is found that DATMF method can predict oil production, investment recovery period, and the future net present value, etc. quickly and accurately. On the one hand, it greatly reduces the time and money cost of using traditional economic prediction methods. On the other hand, comparing with the popular big data analysis method, it improves the data's quality and increases the result's professionalism and practicality by using experts’ experience to constraint data, which makes the DATMF method can work on the smaller database. It is very suitable for the DATMF method to be applied in the early or middle stage of oilfield information construction.
A Composite Transient Model for Multi-Fractured Horizontal Well in Tight Gas Reservoirs Based on Multi-Factor Effect
Authors: Cao Lina , Lu Lize , Li Xiaoping , Wang Hehua , He Wei , Deng Yong , Xu Bing , Jiang Liping 
Published: April 2018

Abstract
In low-permeability tight reservoirs, the natural gas transient flow is affected by multi-factor including stress-sensitivity, threshold pressure gradient, or both. This paper aims to synthetically study transient pressure response as well as transient rate behavior of a multi-fractured horizontal well in tight gas reservoirs. With the new mathematics model, the flow characteristics coupled with such multi-factor can be described.
The new composite seepage model of a line-sink incorporating both stress-sensitive permeability and threshold pressure gradient was established. Employing fractures discretization and superposition principle yielded the final model of a multi-fractured horizontal well. The model was semi-analytically solved by Pedrosa's transformation, perturbation theory, and integration transformation method. Not only pressure transient analysis, but also rate transient analysis are separately performed with relevant parameters.
A total of six flow periods can be divided according to the same standard of time stages for pressure type curves and rate type curves. It is found that stress-sensitivity results in upward tendencies in both of pressure and rate derivative curves reflecting larger pressure drop during intermediate and late flow regimes; threshold pressure gradient leads to more difficult fluid flow acting a steeper upwarping on pressure curve and downwarping on production rate curve. Finally the variation trend of the corresponding curve will be more apparent under the combined impact of stress-sensitivity and threshold pressure gradient. The research of this paper can provide some insights into well dynamic forecasting during exploiting such reservoirs, and contribute to establish the theoretical basic for transient analysis efficiently.
Pressure Detrending for Harmonic Pulse Test Data Preprocessing
Authors: Viberti Dario , Salina Borello Eloisa , Verga Francesca 
Published: April 2018

Abstract
Harmonic Pulse testing was developed as a form of well testing that can be applied during ongoing production or injection operations. A pulsed signal is superimposed to the background pressure trend thus no interruption of well and reservoir production is required before and during the test. The pulsed pressure and rate signal analysis is performed in the frequency domain; to this end, the pressure and the rate signals need to be decomposed into harmonic components. The derivative of the harmonic components in the frequency domain can then be analyzed similarly to a conventional well test. In practice the interpretability of the derivative of the harmonic components can be significantly improved if the pressure trend to which the pressure pulses are superimposed is removed, i.e. a detrending of the pressure data is performed prior to well test interpretation.
In the present paper, the results obtained after applying different detrending methodologies to pressure data recorded during pulse tests in different reservoir conditions are presented and discussed.
Analyses on synthetic test data proved that polynomial detrending is effective in removing the pressure trend induced by field depletion and constant well interference but cannot deal with transient effect related to preexisting rate history or ongoing production changes. Conversely, some of the detrending algorithms based on a heuristic approach are very effective to remove both. Moreover, detrended data can be further regularized by excluding anomalous cycles from the analysis, i.e. cycles that do not respect the designed test periodicity, such as in the case of well interference and/or temporary interruption of the pressure pulses during the execution of the test.
The adoption of an effective detrending strategy can considerably improve the quality of the pressure data obtained from harmonic pulse tests and thus the test interpretability. Therefore, it offers the possibility of overcoming the limitation of applicability due to the difficulty of imposing a regularly pulsing rate for the whole test duration (typically lasting several days). This makes harmonic pulse tests very attractive for well performance monitoring, as in gas storage fields.
AVALIAÇÃO DA CAPACIDADE DOS PROCESSOS DE GOVERNANÇA CORPORATIVA DE TI BASEADA NO COBIT 5
Authors: Santos Diana Leite Nunes dos , Souza Neto João 
Published: April 2018

O COBIT 5 traz a separação dos processos de governança e gerenciamento e uma nova abordagem de avaliação com foco na capacidade dos processos. Esse artigo descreve a aplicação deste tipo de avaliação em uma instituição governamental brasileira, que resultou em 40% dos processos de governança no nível 0 – processo incompleto, e 60% no nível 1 - processo executado. Dado o papel da governança, fragilidades em seus processos podem refletir negativamente no gerenciamento da TI da instituição e pesquisas adicionais devem incluir um aprofundamento neste relacionamento. Para esta instituição, em particular, é esperado que todos os processos de governança passem a ser executados (nível 1) nos próximos dois anos, que é um objetivo no rumo de um sistema de governança eficiente e eficaz. As seguintes barreiras na aplicação desta auto-avaliação foram encontradas: falta de conhecimento dos processos do COBIT 5 por parte da instituição avaliada e extensão do questionário, que chegou a 33 perguntas em sua versão final. Quando comparado com o modelo de avaliação do COBIT 4.1, os resultados foram inferiores, com a mesma organização sendo classificada no nível 2 – repetível mas intuitivo, . O modelo anterior é também mais rápido e fácil de aplicar. Essa comparação deve ser feita com cuidado já que os modelos são muito diferentes em seu desenho e uso. Finalmente, os objetivos propostos foram alcançados: o mecanismo é repetível e pode ser usado futuramente para criar uma base histórica; ele pode ser aplicado como uma auto-avaliação e é esperado que seja completado, numa instituição com uma área de TI de médio porte, em até quatro horas.
Enhanced nitrogen removal and energy saving in a microalgal–bacterial consortium treating real municipal wastewater
Authors: Foladori P. , Petrini S. , Nessenzia M. , Andreottola G. 
Published: April 2018

Abstract
The optimization of total nitrogen removal from municipal wastewater was investigated in a laboratory-scale photo-sequencing batch reactor (PSBR) operated with a mixed microalgal–bacterial consortium spontaneously acclimatized to real wastewater. No external aeration was provided in the PSBR to reduce energy consumption: oxygen was only supplied by the microalgal photosynthesis. The enhancement of total nitrogen removal was achieved through: (1) feeding of wastewater in the dark phase to provide readily biodegradable COD when oxygen was not produced, promoting denitrification; (2) intermittent use of the mixer to favor simultaneous nitrification–denitrification inside the dense flocs and to achieve 41% energy saving with respect to continuous mixing. Efficient COD removal (86 ± 2%) was observed, obtaining average effluent concentrations of 37 mg/L and 22 mg/L of total COD and soluble COD, respectively. TKN removal was 97 ± 3%, with an average effluent concentration of 0.5 ± 0.7 mg NH4+-N/L. Assimilation of nitrogen by heterotrophic bacteria accounted only for 20% of TKN removal, whilst the major part of TKN was nitrified. In particular, the nitrification rate was 1.9 mgN L−1 h−1 (specific rate 2.4 mgN gTSS−1 h−1), measured with dissolved oxygen near zero, when the oxygen demand was higher than the oxygen produced by photosynthesis. Total nitrogen of 6.3 ± 4.4 mgN/L was measured in the effluent after PSBR optimization.
99mTc-labeled Small Molecules for Diagnosis of Alzheimer’s Disease: Past, Recent and Future Perspectives
Authors: Molavipordanjani Sajjad , Emami Saeed , Hosseinimehr Seyed Jalal 
Published: April 2018

Background:
Alzheimer’s disease (AD) is an age-related progressive neurodegenerative disease.
Its prominent hallmarks are extracellular deposition of β-amyloids (amyloid plaques), intracellular
neurofibrillary tangles (NTFs), neurodegeneration and finally loss of cognitive function. Hence, AD diagnosis
in the early stage and monitoring of the disease are of great importance.

Methods:
In this review article, we have reviewed recent efforts for design, synthesis and evaluation of
99mTc labeled small molecule for AD imaging purposes.

Results:
These small molecules include derivatives of Congo red, benzothiazole, benzofuran, benzoxazole,
naphthalene, biphenyl, chalcone, flavone, aurone, stilbene, curcumin, dibenzylideneacetone,
quinoxaline, etc. The different aspects of 99mTc-labeled small molecules including chemical structure,
their affinity toward amyloid plaques, BBB permeation and in vivo/vitro stability will be discussed.

Conclusion:
The findings of this review confirm the importance of 99mTc-labeled small molecules for AD
imaging. Future studies based on the pharmacophore of these designed compounds are needed for improvement
of these molecules for clinical application.
NAChR α4β2 Subtype and their Relation with Nicotine Addiction, Cognition, Depression and Hyperactivity Disorder
Authors: Laikowski Manuela M. , Reisdorfer Fávero , Moura Sidnei 
Published: April 2018

Background:Neuronal α4β2 nAChRs are receptors involved in the role of neurotransmitters regulation and release, and this ionic channel participates in biological process of memory, learning and attention. This work aims to review the structure and functioning of the α4β2 nAChR emphasizing its role in the treatment of associated diseases like nicotine addiction and underlying pathologies such as cognition, depression and attention-deficit hyperactivity disorder.Methods:The authors realized extensive bibliographic research using the descriptors “Nicotine Receptor α4β2” and “cognition”, “depression”, “attention-deficit hyperactivity disorder”, besides cross-references of the selected articles and after analysis of references in the specific literature.Results:As results, it was that found 179 relevant articles presenting the main molecules with affinity to nAChR α4β2 related to the cited diseases. The α4β2 nAChR subtype is a remarkable therapeutic target since this is the most abundant receptor in the central nervous system.Conclusion:In summary, this review presents perspectives on the pharmacology and therapeutic targeting of α4β2 nAChRs for the treatment of cognition and diseases like nicotine dependence, depression and attention-deficit hyperactivity disorder.