bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Fracture Hydrodynamics and In-Situ Kinetics Model Supports Comprehensive Hydraulic Fracture Simulation
Authors: Velikanov Ivan , Isaev Vadim , Bannikov Denis , Tikhonov Alexey , Semin Leonid , Belyakova Ludmila , Kuznetsov Dmitry 
Published: April 2018

Abstract
We demonstrate the advantages of a new hydraulic fracturing simulator comprising a fine-scale fracture hydrodynamics and in-situ kinetics model. In contrast to existing commercial modeling tools, it has a sufficient resolution and other functionality for adequate representation of modern stimulation technologies: pulsing injection of proppant, mixtures of multiple fracturing materials (fluids, proppants, fibers, etc.), materials degradation, etc. This simulator accounts for the influence of materials distribution on fracture propagation and calculates fracture conductivity distribution. We coupled it with a production simulation model and established a complete framework for hydraulic fracturing treatment design. In addition to the selection of the pumping schedule, this model can be used to define specifications for novel hydraulic fracturing materials. This is a step change tool for wellbore stimulation and production forecast.
An Integrated Approach to Explain Anomalous Gas Production from an Oil Bearing Reservoir
Authors: Bona Nicola , Riva Angelo , Martinenghi Carla , Mariotti Pamela , Bombaci Fabio , Rotelli Fabiana , Ragazzini Giovanna , Marco Miarelli 
Published: April 2018

Abstract
We discuss anomalous gas production data observed downdip of oil production in a thick oil reservoir. At the onset of production, the wells under consideration exhibited a sharp rise of the GOR with large disparity between estimated gas in solution and actual gas production. This was followed by a declining GOR period. After declining, the GOR rose and then fell off again in one of the wells. Such a behavior leaves little doubt that free gas exists. The reservoir pressure is approx. 20 bars above the bubble point, so these observations contrast with the general assumption that gas below the gas/oil contact must be in solution in the oil. The fact that free gas comes in peaks suggests the presence of large bubbles suspended in the oil at variable distances from wells. In order to understand how long a gas bubble can live in undersaturated oil and the conditions under which it can be mobilized, we analyze the system in terms of gravity-capillary-viscous force equilibria and investigate the kinetics of gas diffusion into the oil. We show that bubbles that are sufficiently large in width (hundreds of meters) and sufficiently small in thickness (a few meters) can move horizontally but not vertically (meaning that they remain suspended in the oil and are producible) and take hundreds of thousands of years to dissolve into the oil. The presence of these bubbles is compatible with the available geochemical data, which provide evidences that the source rock of gas is more mature than that of oil and probably still in the generation and expulsion phase. This unusual non-equilibrium situation was reproduced by means of 3D simulation approach, to confirm the conceptual model adopted.
Optimizing Laboratory cEOR Flooding Evaluations to Assess Initial Oil Saturation and Mobility Ratio
Authors: Foedisch Hendrik , Abdullah Hiwa , Hincapie Rafael E. , Ganzer Leonhard 
Published: April 2018

Abstract
We evaluate the polymer, surfactant and alkaline flooding performance in porous media by using an in-house innovative experimental setup. This, to reach an optimum experimental evaluation in an attempt to avoid repeated experimental failures reported in the literature. The workflow presented help us to understand the recorded data with high reliability and accuracy. Moreover, allow working at high temperatures and high salinities in order to mimic reservoir conditions.
The evaluation undertaken in this paper comprises four main steps: 1) Fluids preparation and optimization, beginning with an extensive rheological evaluation to define the optimum concentration/composition of the fluids. 2) Calibration of pressure sensors and pumps, and detailed determination of the system's dead volume. 3) Routine core analysis was performed, which included measuring porosity, permeability and pore volume. 4) Spontaneous imbibition experiments, secondary and tertiary mode cEOR flooding experiments. The core flooding experiments were performed at a constant flow rate of 0.15ml/min (equivalent to the field conditions of 1ft/day), then followed by a bump rate after Sor is reached.
The constructed setup proved to be beneficial on reducing the experimental failures by showing data reproducibility and precision. Small diameter tubings of 1/16″ minimized the dead volumes and core face differential pressure measurement allowed high accuracy at any injection rate. At elevated temperatures (50°C) polymer flooding in secondary mode showed 2% higher recovery compared to tertiary mode. Similar difference was observed at the ambient temperature. For the conditions evaluated in this work, HPAM polymer showed higher recoveries than those of Bio-polymer at higher temperatures. However, lower recoveries from HPAM were observed at lower temperatures. In terms of surfactant flooding experiments the observed performance is significantly better in secondary compared to tertiary mode, as well as facing significant production of emulsion from suboptimal surfactant solutions. Thoroughly examining these differences in recoveries, two key factors were considered to be of critical interest: initial oil saturation and mobility ratio. Moreover, CT scan imaging allowed assessing capillary end effects during oil saturation. A detailed comparison between dry and saturated core images was performed to insure no capillary end effects existed. Finally, a developed mathematical simulation model permitted to quality check the work and create a benchmark for further evaluations.
The workflow presented in this paper helps to close the gaps often discussed in the literature with regards to flooding experimental failures at core plug scale. Thus, it can help fellow researchers to optimize their workflow and enhance the final results to aid in fluid evaluation and assessing the optimum cEOR process.
Near Wellbore Two-Phase Effect of a Light Oil Field
Authors: Zhou Zhaocong , Lamberti Andrea , Locci Andrea , Parasiliti Valerio , Prevosti Paolo , Tripaldi Giuseppe 
Published: April 2018

Abstract
This work describes a case of a light oil field in Sub-Saharan Africa. Soon after the start up, the production wells showed a productivity index different from expectation. In particular, well test analysis showed different stabilizations between build-up and drawdown. Since the well is flowing with pressure below the bubble point, the impact of oil permeability reduction due to presence of free gas around the wellbore was considered as a possible explanation and was investigated.
We applied well test analysis on synthetic data generated by numerical simulation. The analysis confirms the different stabilizations between pressure build-up and drawdown, as observed from the real field case, when the flowing bottomhole pressure is below the bubble point pressure. The different flow capacity is caused by gas saturation around the wellbore, which reduces the effective permeability to oil, hence the productivity index.
Besides this, we experienced that a full field model with large grid size is not able to represent this phenomenon. Due to the grid size, the full field model shows less pressure drop than the radial sector model, hence different gas saturation calculation. We showed that in order to simulate the effect without impacting on simulation time, applying higher well skin instead of local grid refinement can be a way forward.
Investigating the Uniformity of In-Situ Asphaltene Deposits in Sandstone Rocks
Authors: James Abraham Jocin , Mehana Mohamed , Fahes Mashhad 
Published: April 2018

Abstract
The stability of asphaltene molecules is tied to the changes induced by temperature, pressure or composition. Therefore, the precipitation of these molecules is expected during various operations and at different stages of well life. While the deposition and remediation of asphaltenes in wellbores and pipelines are well-addressed, the deposition phenomena in reservoir rock and its impact on rock characteristics and fluid dynamics is still not well-developed. We have developed an experimental workflow to create a uniform deposit of asphaltene inside the core sample. The results show that injecting oil or a heptane/oil mixture results in a non-uniform deposition of Asphaltene, which was quantified using the TOC and density measurements. Uniform exposure to crude oil and deposition was obtained through vacuum saturation of the cores. However, permeability impairment is evident in both cases; whether the deposition is developed using vacuum-saturation or injection. Interestingly, the absolute permeability damage could be mitigated by reversing the injection flow direction which suggest that pore throat plugging is the main damage mechanism, while deposition onto the rock surface is the secondary damage mechanism for absolute permeability.
A Well Placement Optimization Constrained to Regional Pressure Balance
Authors: Al-Ismael Menhal , Awotunde Abeeb , Al-Yousef Hasan , Al-Hashim Hasan 
Published: April 2018

Abstract
Reservoir characterstics and profitability are two important constraints in any field development. Net present value (NPV) is usually used to measure the cash flow profitability profile and determine associated financial risks. On the other hand, voidage replacement ratio (VRR) is used to measure the rate of change in reservoir energy. In recent studies, VRR was used as an additional objective in well placement optimization. Such studies proposed minimizing single value of VRR that represents the entire reservoir. However, such single VRR value may not detect unbalanced distribution of reservoir pressure. Severe alteration of voidage replacement distribution could occur in the reservoir that could not be represented accurately by a single value of VRR. Therefore, we propose a more efficient method to overcome disparate regional pressure changes in well placement optimization. This new method is based on optimization of NPV constrained to regional average pressure of the reservoir. Differential evolution algorithm was applied to find the optimum well locations that yield the maximum NPV constrained to regional pressure balance. The regional pressure balance was achieved by specifying a maximum allowable difference between any two regional pressures. We evaluated four scenarios of reservoir development. The first two scenarios involve the use of predefined well patterns. In these scenarios, the well locations were selected without any optimization. The third scenario involves the optimization of well placement without constraining it to any pressure balance. The fourth scenario involves optimization of well placement constrained to regional pressure balance. The results obtained indicate that we can minimize the difference of average pressure between regions while achieving high values of NPV. This helps to have a uniformly distributed reservoir pressure throughout the production life of the reservoir.
Cyclic Flow of Two Immiscible Phases
Authors: Rabinovich Avinoam 
Published: April 2018

Abstract
We derive an analytical solution for two-phase cyclic flow assuming incompressible fluid and rock, one dimensional flow and negligible capillary pressure effects. The solution is intended to model subsequent periods of injection and production in a reservoir or core sample. It pertains to applications such as gas storage in water bearing formations or enhanced oil recovery by CO2 cyclic injection. Derivation is based on the method of characteristics and leads to an extension of the Buckeley-Leverett solution to cyclic injection. The saturation profile consists of two functions separated by a discontinuity. It is shown that the moving front advances during injection and recedes during production until returning back to the well. Some injected phase may remain in the reservoir after production and this in turn contributes to a deeper penetration during the next injection period.
The solution for saturation profile as a function of time is analyzed and shown to become steady periodic after a number of cycles. We investigate the solution dependence on the controlling parameters: relative permeability (power n in krw, krnw functions), viscosity ratio μw/μnw and nondimensional production time t˜prod.
Highlights of the TAMEST Task Force Report on Environmental and Community Impacts of Shale Development in Texas
Authors: Ehlig-Economides Christine 
Published: April 2018

Abstract
The combined horizontal well and multistage hydraulic fracturing technologies that enabled profitable hydrocarbon production from shale gas and tight oil formations were developed and originally proven in Texas. Through these technologies Texas crude oil production tripled, and natural gas production increased by 50%. The Academies of Medicine, Engineering, and Science of Texas (TAMEST) appointed a task force to report on the impacts of shale gas and tight oil development in Texas.
The task force goal was to evaluate the scientific basis of the current body of available information, both positive and negative, and effectively communicate to the public the current state of knowledge of environmental and community impacts of shale development in Texas. The task force members were selected from academia, industry, governmental agencies, and non-governmental organizations and focused on six key aspects: air, land, water, seismicity, transportation, and community social and economic impacts.
Task force members summarized the published information they found and prepared findings and recommendations. Together these represent a thorough review of the Texas shale experience. This paper will present findings most informative for regions with potential resource plays.
Tight oil development has brought the United States from a threatened condition under which oil consumption relied on nearly 60% imports to a sense of energy security. Shale gas development has enabled switching electric power generation from coal to cleaner and more efficient natural gas. Further, natural gas backs up power generation from intermittent renewable energy sources like wind and solar. Understanding the environmental and community impacts in Texas enables a more informed evaluation of the costs and benefits of these intense development practices.
Study on the Coupled Effect of Effective Stress and Methane Gas Adsorption on the Porosity and Permeability of Shale Gas Reservoirs
Authors: Tian Wei , Liu Huiqing , He Shunli , Wang Jing , Zhang Zequan , Zheng Majia , Ning Zhengfu 
Published: April 2018

Abstract
Shale gas is considered very important unconventional hydrocarbon resources. Due to the technological advances of hydraulic fracturing, the development of shale gas has become the main focus in recent years. Porosity and permeability are the most important petrophysical parameters during the production of shale gas. A considerable amount of research work has been carried out on stress law of porosity and permeability. However, nearly none of them considered the effects of methane adsorption.
This paper utilizes the simplified local-density (SLD) theory to study adsorption of supercritical gas in shale gas reservoirs. On the basis of the basic features of high pressure supercritical adsorption of shale gas, Peng—Robinson equation is used to describe adsorbed fluid. The interaction between the gas molecules and porewalls of shale is considered using Lennard-Jones potential. Finally, we establish the SLD model to do regression analysis for the adsorption experiments data. The density of adsorbed phase and free phase density could be obtained applying SLD model and then the amount of gas adsorption can be determined. The Gibbs adsorption amount calculated using the SLD model is used to establish matrix strain model. Finally, the strain model is incorporated into widely used analytical porosity and permeability models to develop the coupled model with consideration of the coupled effect of gas adsorption and stress on the porosity and permeability of shale gas reservoirs. And the trend of variation of porosity and permeability of shale rocks taking account of the effects of stress and gas adsorption can be obtained.
Lab experiments of gas adsorption of methane gas are made on three shale samples. The developed SLD model is applied to describe gas adsorption data. The outcome indicates that SLD model can properly analyze and fit the experimental data. From the results calculated by the new developed model of porosity and permeability, we can conclude that porosity ratios and permeability ratios of gas shales decrease with the increase of pore pressure, which is contrary to the tendency of changes in porosity and permeability only taking account of the effects of effective stress. This result demonstrates that gas adsorption has very large impact on pore volume, therefore the deformation of matrix induced by the adsorption of methane gas cannot be neglected.
The proposed model could further be used for the accurate evaluation of storage capacity of shale gas reservoirs and gas production of wells.
Flow Diagnostics for Naturally Fractured Reservoirs
Authors: Spooner Victoria , Geiger Sebastian , Arnold Dan 
Published: April 2018

Abstract
In this paper we describe new and innovative flow diagnostics tools for dual porosity models for naturally fractured reservoirs. Our new diagnostic tools allow us to compare and rank large numbers of geological models based on their approximate dynamic response in almost negligible time. Fast ranking methods allow us to select a representative ensemble of models that quantify geological uncertainty for robust production forecasting via full physics reservoir simulation.
Reliable production forecasting for fractured carbonate reservoirs is a challenge. Natural fractures, adverse wettability and complex matrix heterogeneity are all highly uncertain and can all negatively impact upon recovery. Ideally we should consider a large and diverse ensemble of reservoir models to quantify the impact of geological uncertainty on reservoir performance. However, the computational cost can be significant, especially for dual porosity/permeability models. A brute force approach using powerful workstations, clusters or cloud computing can be taken to reduce the time investment. But this is not always possible, rendering robust uncertainty quantification impractical for many asset teams. Often only a small subset of scenarios is considered which may collapse into a single base case, from which development decisions are made. Base cases often fail to predict future production, need frequent modifications, lack geological realism and provide incomplete risk assessments, often causing asset teams to miss economic opportunities.
Flow diagnostics can provide dynamic reservoir information in a fraction of the time for full physics simulation. We propose a workflow where we utilise flow diagnostics as a ranking tool to complement forecasting using reservoir simulation throughout. Our approach addresses the model run time, allowing us to use standard hardware. Flow diagnostics solve simplified physics to approximate the dynamic response of the reservoir, from this we can calculate and visualize key dynamic properties (e.g., time-of-flight, drained and swept reservoir volumes, time-to-breakthrough, decline rates, sweet spots, well-allocation factors). Flow diagnostics provide robust indicators of dynamic heterogeneity that allow us to select a diverse ensemble of models that captures the range of uncertainty.
In this work, novel diagnostics utilising physically based transfer models have been developed to account for the fracture-matrix exchange, which otherwise could only be obtained from lengthy simulation. A new Damköhler number based metric DaDP links the advective time-of-flight in the fractures to the transfer from the matrix. DaDP identifies fast and slow draining regions of the matrix, stagnant regions within the fracture network and wells at risk of water breakthrough. This information can subsequently be used to optimise well placement and rates to maximise production and delay water breakthrough.
Telescopic Denture
Authors: Hakkoum Mohammad Ayham , Wazir Ghassan 
Published: April 2018

Aim:This article explains the concept of telescopic denture.Procedure:It describes the different types of telescopic attachment (or double crown), and provides an overview of the advantages and the disadvantages of this type of prosthodontic treatment.Conclusion:The indications and the clinical applications of telescopic denture are discussed.
Mycobacteriosis and Tuberculosis: Laboratory Diagnosis
Authors: Azadi Davood , Motallebirad Tahereh , Ghaffari Kazem , Shojaei Hasan 
Published: April 2018

Background:Tuberculosis is one of the most important infectious diseases that has claimed its victims throughout much of known human history. With Koch's discovery of the tubercle bacillus as the etiologic agent of the disease, his sanitary and hygienic measures, which were based on his discovery and the development of a vaccine against tuberculosis by Albert Calmette and Camille Guérin in 1921, an attenuatedMycobacterium bovisstrain, bacilli Calmette-Guérin (BCG), and the discovery of the first antibiotic against tuberculosis, streptomycin by Selman Waksman in 1943, soon led to the opinion that appropriate control measures had become available for tuberculosis and it had been assumed that the disease could ultimately be eradicated.The emergence of resistant strains of this bacteria and widespread distribution of the disease in the world, and the emergence of the AIDS epidemic destroyed any possibility of global control of tuberculosis in the foreseeable future.Objectives:The purpose of this review is to highlight the current scientific literature on mycobacterial infections and provide an overview on the laboratory diagnosis of tuberculosis and non-tuberculosis infections based on conventional phenotypic and modern molecular assays.Method:In this study, a number of 65 papers comprising 20 reviews, 9 case reports, and 36 original research in association with mycobacteriosis and the laboratory diagnosis of mycobacterial infections, were reviewed.Results:Based on our analysis on the published documents methods applied for the laboratory diagnosis of tuberculosis are continually assessed and developed in order to achieve more rapid, less expensive, and accurate results. Acid-fast staining and culture for mycobacteria remain at the core of any diagnostic algorithm with the sensitivity of 20-70% and specificity of 95-98% for AFB microscopy and the sensitivity of 95% and the specificity of 98% for culture based diagnosis. Following growth in culture, molecular tests such as nucleic acid hybridization probes and DNA sequencing may be used for definitive species identification. Nucleic acid amplification methods provide the means for direct detection ofMycobacterium tuberculosisin respiratory specimens without the prerequisite to isolate or culture the organism, leading to more rapid diagnosis and better patient care.Conclusion:As the researchers in a developing country, we strongly believe that despite significant advances in laboratory capacity, in many countries reliable confirmation of suspected mycobacterial diseases is hindered by a lack of knowledge on proper standardized methods, sufficient funds, suitably trained staff and laboratory supplies.