bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Black Oil Simulator that Includes the Impact of Capillary Pressure on Phase Behavior in Nano-Porous Unconventional Reservoirs
Authors: Ozgen Chet , Calisgan Tugce , Firincioglu Tuba , Ozkan Erdal 
Published: April 2016

Abstract
Black oil simulators that are commonly used in the industry are not formulated to handle the impact of capillary pressure on phase behavior, and they do not evaluate fluid properties at corresponding gas and oil phase pressure values. This may be a significant problem in simulation of nano-porous unconventional reservoirs where fluid phase equilibrium calculations are affected due to capillary forces in confinement. Studies have shown that the confinement manifests itself as suppression in bubble point pressure which extends the under-saturated portion of the formation volume factor curve for oil. The objective of this study is to evaluate the simulator behavior when the formulation of a black oil simulator is enhanced to include the capillary pressure impact on phase behavior. For the initialization step of the simulator, to achieve gravity-capillary equilibrium phase densities and suppression due to capillary pressure are calculated in an iterative manner while using fluid properties at the pressure of corresponding phase. For the flow simulation formulation, rather than a phase pressure, the (unconfined) bulk pressure was assigned as one of the solution variables to be solved in the discretized continuum equations. Individual phase pressures are derived from the bulk pressure using excess pressure and corresponding capillary pressure values. A correlation that represents the bubble point suppression as a function of solution gas oil ratio (Rs) and capillary pressure (Pc) was introduced into the simulator. Sensitivity tests were performed to show the impact of phase behavior change due to confinement on fluid flow and production from wells. Various simulation models were built to study the impact of single-, dual-, triple- and quintuple-porosity formulations on calculated oil and gas production profiles at different capillary pressure values. Results show that depending on the magnitude of the confinement and the formulation that is used, oil and gas production profiles of the simulation models are affected.
Rate-Transient Analysis of Liquid-Rich Tight/Shale Reservoirs Using the Dynamic Drainage Area Concept: Examples from North American Reservoirs
Authors: Qanbari F. , Clarkson C. R. 
Published: April 2016

Abstract
The early-time performance of multi-fractured horizontal wells is mainly controlled by fracture geometry, total effective area of the fractures, and conductivity of the primary fracture system. Rate-transient analysis (RTA) methods have historically been used to characterize MFHWs at different stages of well life, including this early-time performance. In particular, linear flow analysis is used to estimate the total effective fracture area from online production data, provided that reservoir and fluid properties are known. However, a primary complication in linear flow analysis is the incorporation of nonlinearities such as multi-phase flow and pressure-dependent rock/fluid properties into the calculations.
A new linear flow analysis technique is presented in the current study, which can be applied to tight/shale systems with multi-phase flow and pressure-dependent rock/fluid properties. The method combines three important reservoir engineering concepts for linear flow analysis: dynamic drainage area (DDA), material balance, and decoupling of saturation and pressure (which is analogous to the decoupling of geomechanics and fluid flow). The DDA concept, which uses a time-dependent well productivity index equation for the transient flow period, facilitates the incorporation of any sort of nonlinearity (including decoupled saturation functions) and operational constraints in modeling and RTA of linear flow in MFHWs.
The method is validated against numerical simulation and applied to various sets of field production data from tight/shale gas and oil wells with different levels of condensate- (oil-) gas ratio. For all the field cases, total effective fracture area obtained from the new analytical RTA method is in reasonable agreement with numerical modeling results.
Regarding accuracy and practicality, the new method represents an improvement in RTA of liquid-rich tight/shale reservoirs, particularly for cases with multi-phase flow and pressure-dependent rock/fluid properties. Further, the concepts used in the new model development are easy to understand and implement.
A New Friction-Reducing Agent for Slickwater Fracturing Treatments
Authors: Ibrahim Ahmed F. , Nasr-El-Din Hisham A. , Rabie Ahmed , Lin Genyao , Zhou Jian , Qu Qi 
Published: April 2016

Abstract
Friction reducers (FRs) represent an essential component in any slickwater fracturing fluid. While the majority of the previous research focused on evaluating the friction-reduction performance of these chemicals, only a few studies addressed the potential damage these chemical can cause to the formation.
Because of the polymeric nature of these chemicals (typically PAM, polyacrylamide), a friction reducer can either filter out onto the surface of the formation or penetrate deeply to plug the pores. In addition, breaking these polymers at temperatures lower than 200°F remains a problem. This work introduces a new and non-damaging friction reducer that can be a replacement for liner gel with enhanced proppant-carrying capacity.
Friction-reduction performance, proppant settling, viscosity, and coreflood studies were conducted with the following objectives: (1) investigate the effect of using the new FR on the permeability of tight sandstone formation compared to two conventional FRs, (2) test the performance of the new FR in different salinity environments from fresh to saline water, and (3) examine the effectiveness of breaking the new FR using different breakers.
The friction reduction of the new chemical was higher than 65% in fresh water or 2 wt% KCl in the presence of calcium chloride or choline chloride. The presence of 1 gpt of different types of breaker did not affect the friction reduction performance. The friction-reduction of 1 gpt of the new FR1 was higher than the guar-based FR3 at load of 4 gpt at the same conditions. The results also showed that the new friction reducer is easily breakable in any of the three tested breakers: ammonium persulfate, sodium persulfate, and hydrogen peroxide. Among the three, ammonium persulfate was the most efficient breaker. Static and dynamic proppant settling tests indicated a superior performance of FR1 compared to another conventional polyacrylamide friction reducer (FR2).
Coreflood experiments showed that the new friction reducer FR1 did not result in any residual damage to the formation permeability compared to 10 and 7% damage when the other two conventional friction reducers FR2 and FR3 were tested, respectively. Coreflood tests also showed that the new friction reducer is breakable using a weaker breaker such as sodium bromate with a minimum of 2.5% damage. The results showed that higher salinity did not affect the breakability of the new friction reducer.
Laboratory Evaluation of Multiphase Permeability Evolution in Tight Sandstones: Impact of Slickwater and Friction Reducers
Authors: Abaa Kelvin , Yilin-Wang John , Elsworth Derek , Ityokumbul Mku 
Published: April 2016

Abstract
Fracture fluid filtrate in low permeability sandstones may severely reduce the effective gas permeability.
This work investigates the role that fluid filtrate from slickwater fracturing has on rock-fluid and fluid-fluid interactions and to quantify the resulting multiphase permeability evolution during imbibition and drainage of the filtrate by means of specialized core testing techniques. Three suites of experiments were conducted. In the first suite of experiments, fluid leak-off tests were conducted on selected core samples to determine the extent of invasion and leakoff characteristics. In the second suite, multiphase relative permeability measurements were conducted on sandstone plugs saturated with fracture fluid filtrate. Pulse decay permeability techniques were employed to measure liquid and gas effective permeability for both drainage and imbibition cycles. These experiments capture dynamic permeability evolution during invasion and cleanup of the fracture fluid (slickwater). The final suite of experiments consist of adsorption flow tests to investigate, identify and quantify possible mechanisms of adsorption of the polymeric molecules of friction reducers present in the fluid filtrate to the pore walls of the rock sample. Imbibition tests and observation of contact angles were conducted to investigate possible changes in wettability.
Results from multiphase permeability flow tests show an irreversible reduction in end-point brine permeability and relative permeability with increasing concentration of friction reducer. Our results also show that effective gas permeability during drainage of the imbibed slickwater fluid is principally controlled by trapped gas saturation rather than by changes in interfacial tension. Adsorption flow tests identified adsorption of polymeric molecules of the friction reducer present in the fluid to the pore walls of the rock. The adsorption friction reducer increases wettability of the rock surface and results in the reduction of liquid relative permeability. The originality of this work is to derive a set of multiphase and petrophysical parameters from laboratory experiments that adequately captures multiphase permeability evolution specific to slickwater fluid systems, during imbibition and flowback. This will be useful in diagnosing formation damage from aqueous phase retention and optimizing fracturing fluid selection.
Potential Application of Atomic Force Microscopy in Characterization of Nano-pore Structures of Bakken Formation
Authors: Liu Kouqi , Ostadhassan Mehdi , Jabbari Hadi , Bubach Bailey 
Published: April 2016

Abstract
The Bakken Formation, an unconventional reservoir with very low permeability, is the main production zone in the Williston Basin, ND. Reliable numerical simulation of production performance of this formation requires an accurate description of the rock structures. Characterizing the pore structures is very important in understanding the storage capacity and also the mass transport potential of hydrocarbon. This has been the subject of number of studies by many researchers in the past few years. It has been found that the conventional methods are not applicable to characterize the nano-pore structures of shale formations due to several factors, including low resolution or the most important one, the potential damage to the tight sample during lab testing. This calls for methods which are specifically applicable to characterizing ultra-small pore structures.
In this paper, first we analyze mineral compositions of the samples that are from the Bakken Formation by XRD2. Then we use FESEM to analyze the microstructures of the samples and identify the existence of nano-pores. Then Atomic Force Microscopy (AFM) is acquired for more detailed characterization. We focused to show the great potential of this method in characterizing and quantifying the pore structures in the Bakken Formation. Finally future research work regarding how AFM can provide more insight to the shale nano world are noted.
Towards energy neutrality by optimising the activated sludge process of the WWTP Bochum-Ölbachtal
Authors: Marner S. T. , Schröter D. , Jardin N. 
Published: April 2016

Abstract
As a result of Ruhrverband's regularly performed energy audits the wastewater treatment plant (WWTP) Bochum-Ölbachtal shows substantial deficits concerning energy efficiency. Due to the energy consumption of internal recirculation, mixers and return activated sludge (RAS) pumping the existing pre-denitrification process configuration offers a specific energy consumption for biological treatment of 23 kWh (PE · a)−1. In order to optimise the energy situation and to improve the treatment efficiency, the process layout was changed completely to a three-stage step-feed process. By optimising the hydraulic conditions, it was possible to reconstruct the plant with a free flow throughout the whole biological treatment system without any additional pumping. The total investment costs for this process scheme were 3.9 million €. These costs could be partly offset against the wastewater charge paid (2.9 million €). Compared to the overall energy consumption before the process modification, today the energy consumption for biological treatment amounts to 12.4 kWh (PE · a)−1. The highest saving potential has been achieved by optimising mixing and reducing the energy demand for internal recirculation and RAS pumping. In the case of the WWTP Bochum-Ölbachtal, the modification of the treatment process not only results in an improved energy situation but also increased the treatment efficiency in such a way that the nitrogen concentration in the effluent could be constantly kept below 5 mg L−1 Ntot, which provides the basis for being exempted from the wastewater discharge for nitrogen. As a result of all these measures, the rate of self-sufficiency by using biogas from the digester in combined heat and power units has been increased substantially from 60% before process modifications to 97%. With the upcoming optimisation measures, a further increase of self-sufficiency is expected to finally achieve energy neutrality based on yearly averages. The example of the WWTP Bochum-Ölbachtal clearly shows that it is worthwhile to consider further measures for improving the energy and treatment efficiency, although most of the machinery was not fully depreciated at the time of implementing the new concept. It is also evident that the regular energy monitoring is essential for identifying potential for improvement. In this context and based on Ruhrverband's experience, it is highly suggested that energy audits are performed regularly for larger WWTPs.
Prognostic Classification Factors Associated With Development of Multiple Autoantibodies, Dysglycemia, and Type 1 Diabetes—A Recursive Partitioning Analysis
Authors: Xu Ping , Krischer Jeffrey P. ,   on behalf of the Type 1 Diabetes TrialNet Study Group
Published: April 2016

OBJECTIVE
To define prognostic classification factors associated with the progression from single to multiple autoantibodies, multiple autoantibodies to dysglycemia, and dysglycemia to type 1 diabetes onset in relatives of individuals with type 1 diabetes.

RESEARCH DESIGN AND METHODS
Three distinct cohorts of subjects from the Type 1 Diabetes TrialNet Pathway to Prevention Study were investigated separately. A recursive partitioning analysis (RPA) was used to determine the risk classes. Clinical characteristics, including genotype, antibody titers, and metabolic markers were analyzed.

RESULTS
Age and GAD65 autoantibody (GAD65Ab) titers defined three risk classes for progression from single to multiple autoantibodies. The 5-year risk was 11% for those subjects &gt;16 years of age with low GAD65Ab titers, 29% for those ≤16 years of age with low GAD65Ab titers, and 45% for those subjects with high GAD65Ab titers regardless of age. Progression to dysglycemia was associated with islet antigen 2 Ab titers, and 2-h glucose and fasting C-peptide levels. The 5-year risk is 28%, 39%, and 51% for respective risk classes defined by the three predictors. Progression to type 1 diabetes was associated with the number of positive autoantibodies, peak C-peptide level, HbA1c level, and age. Four risk classes defined by RPA had a 5-year risk of 9%, 33%, 62%, and 80%, respectively.

CONCLUSIONS
The use of RPA offered a new classification approach that could predict the timing of transitions from one preclinical stage to the next in the development of type 1 diabetes. Using these RPA classes, new prevention techniques can be tailored based on the individual prognostic risk characteristics at different preclinical stages.
La Fête-Dieu à Colmar à la fin du Moyen Âge
Authors: Kehr Monique Debus 
Published: April 2016

La Fête-Dieu, célébrée tous les ans le jeudi après la fête de la Trinité, est instaurée en 1264 par la bulle Transiturus de hoc mundo du pape Urbain IV. À Colmar, à la fin du Moyen Âge, cette fête et la procession qui l’accompagne sont le privilège de la paroisse Saint-Martin et l’un des événements majeurs de l’année liturgique. Elles réunissent les membres des couvents et du clergé, ainsi que les corps constitués de la ville. Deux sources essentielles, la « Kirchenordnung » de 1556, de François d’Apponex, et un sermon du diacre protestant Joachim Klein, prononcé le 4 juin 1667, nous permettent d’entrer dans le détail de la fête. Elles relatent le déroulement des offices de ce jour, le tracé de la procession au cœur de la ville et son décorum, indiquent son importance sacrée et sociale, son interdiction, enfin, lorsque la Réforme est introduite à Colmar en 1575.
Marseillaise, paradis tricolore et drapeaux par milliers
Authors: Schmauch Joseph 
Published: April 2016

La signature de l’Armistice du 11 novembre 1918 et la perspective du retour à la France s’accompagnent d’une vague de festivités inédite en Alsace. L’entrée dans les villes des généraux français, ou encore la visite du président de la République, sont l’occasion de cortèges militaires et de réceptions officielles. Ces événements s’inscrivent dans le droit fil de manifestations semblables observées pendant la guerre, lors de l’éphémère conquête de Mulhouse en août 1914 ou dans le cadre de l’administration française des vallées de la Thur et de la Doller. Ces journées comportent une dimension spontanée dont témoigne l’implication massive et volontaire des populations : au sortir d’une guerre longue, la fête permet d’exorciser un passé récent douloureux et offre aux populations une perspective d’avenir prometteuse. Elle permet aussi aux Alsaciens, qui ont vécu la guerre du côté allemand, de s’approprier un ensemble de rituels républicains, participant ainsi d’une découverte réciproque. L’unanimité n’est cependant pas totale : les nombreux démobilisés de l’armée allemande sont absents des réceptions et, les réjouissances à peine terminées, apparaissent déjà les premiers signes du « malaise alsacien ».
Combined fluvial and pluvial urban flood hazard analysis: concept development and application to Can Tho city, Mekong Delta, Vietnam
Authors: Apel Heiko , Martínez Trepat Oriol , Hung Nguyen Nghia , Chinh Do Thi , Merz Bruno , Dung Nguyen Viet 
Published: April 2016

Abstract. Many urban areas experience both fluvial and pluvial floods, because locations next to rivers are preferred settlement areas and the predominantly sealed urban surface prevents infiltration and facilitates surface inundation. The latter problem is enhanced in cities with insufficient or non-existent sewer systems. While there are a number of approaches to analyse either a fluvial or pluvial flood hazard, studies of a combined fluvial and pluvial flood hazard are hardly available. Thus this study aims to analyse a fluvial and a pluvial flood hazard individually, but also to develop a method for the analysis of a combined pluvial and fluvial flood hazard. This combined fluvial–pluvial flood hazard analysis is performed taking Can Tho city, the largest city in the Vietnamese part of the Mekong Delta, as an example. In this tropical environment the annual monsoon triggered floods of the Mekong River, which can coincide with heavy local convective precipitation events, causing both fluvial and pluvial flooding at the same time. The fluvial flood hazard was estimated with a copula-based bivariate extreme value statistic for the gauge Kratie at the upper boundary of the Mekong Delta and a large-scale hydrodynamic model of the Mekong Delta. This provided the boundaries for 2-dimensional hydrodynamic inundation simulation for Can Tho city. The pluvial hazard was estimated by a peak-over-threshold frequency estimation based on local rain gauge data and a stochastic rainstorm generator. Inundation for all flood scenarios was simulated by a 2-dimensional hydrodynamic model implemented on a Graphics Processing Unit (GPU) for time-efficient flood propagation modelling. The combined fluvial–pluvial flood scenarios were derived by adding rainstorms to the fluvial flood events during the highest fluvial water levels. The probabilities of occurrence of the combined events were determined assuming independence of the two flood types and taking the seasonality and probability of coincidence into account. All hazards – fluvial, pluvial and combined – were accompanied by an uncertainty estimation taking into account the natural variability of the flood events. This resulted in probabilistic flood hazard maps showing the maximum inundation depths for a selected set of probabilities of occurrence, with maps showing the expectation (median) and the uncertainty by percentile maps. The results are critically discussed and their usage in flood risk management are outlined.
Insights on high-grade deformation in quartzo-feldspathic gneisses during the early Variscan exhumation of the Cabo Ortegal nappe, NW Iberia
Authors: Fernández Francisco José , Llana-Fúnez Sergio , Valverde-Vaquero Pablo , Marcos Alberto , Castiñeiras Pedro 
Published: April 2016

Abstract. High-grade, highly deformed gneisses crop out continuously along the Masanteo peninsula and constitute the upper part of the lower crustal section in the Cabo Ortegal nappe (NW Spain). The rock sequence formed by migmatitic quartzo-feldspathic (qz-fsp) gneisses and mafic rocks records the early Ordovician (ca. 480–488 Ma) injection of felsic dioritic/granodioritic dykes at the base of the qz-fsp gneisses, and Devonian eclogitization (ca. 390.4 ± 1.2 Ma), prior to its exhumation. A SE-vergent ductile thrust constitutes the base of quartzo-feldspathic gneissic unit, incorporating mafic eclogite blocks within migmatitic gneisses. A NW-vergent detachment displaced metasedimentary qz-fsp gneisses over the migmatites. A difference in metamorphic pressure of ca. 0.5 GPa is estimated between both gneissic units. The tectono-metamorphic relationships of the basal ductile thrust and the normal detachment bounding the top of the migmatites indicate that both discrete mechanical contacts were active before the recumbent folding affecting the sequence of gneisses during their final emplacement. The progressive tectonic exhumation from eclogite to greenschist facies conditions occurred over ca. 10 Ma and involved bulk thinning of the high-grade rock sequence in the high pressure and high temperature (HP–HT) Cabo Ortegal nappe. The necessary strain was accommodated by the development of a widespread main foliation, dominated by flattening, that subsequently localized to a network of anastomosing shear bands that evolved to planar shear zones. Qz-fsp gneisses and neighbouring mafic granulites were exhumed at > 3 mm yr−1, and the exhumation path involved a cooling of  ∼  20 °C/100 MPa, These figures are comparable to currently active subduction zones, although exhumation P–T trajectory and ascent rates are at the hotter and slower end in comparison with currently active similar settings, suggesting an extremely ductile deformation environment during the exhumation of qz-fsp gneisses within a coherent Cabo Ortegal nappe.
Deformación del Pico en el Caracara Común (Caracara cheriway), Tratamiento y Recuperación
Authors: Aceituno Francisco 
Published: April 2016

Se reporta el registro de un caracara común (Caracara cheriway) con una deformación en el pico. El ave fue recibida en el Zoológico Rosy Walther en Tegucigalpa, Honduras. Esta anormalidad del pico no permitía que el ave se alimentara de forma normal ya que la maxila medía 12.5 cm y la mandíbula 5.5 cm. No se determinó la causa específica de la deformación. Al ave la mantuvieron ilegalmente como mascota y generalmente en estas condiciones la alimentación ofrecida a las especies no suple sus requerimientos alimenticios y puede provocar este tipo de deformaciones. Para tratar esta deformación se utilizó una herramienta Dremel, lo que permitió corregir la forma y el tamaño del pico.