1,720,968 research outputs found
Effect of Nanoparticles and Solvent Based Emulsion on Heavy Oil Viscosity
Full text linkConsidering the fact that heavy oil and bitumen constitutes about 70% of world’s total oil resources, it is not surprising that the quest to produce heavy oil has attained industry wide attention. Because of extremely high viscosity, heavy oil reservoirs generally yield low-energy and low-productivity wells. Technical and economic challenges associated with heavy oil production, indicate a need for extensive research and development activities.
The objective of study presented in this document is to investigate three different approaches for reducing viscosity of heavy oil. In the first set of experiments, three types of metal oxide nanoparticles (CuO, Fe2O3, and NiO) were employed and their effect on heavy oil viscosity was investigated at different concentrations. The second approach was to mix a solvent-in-water (S/W) emulsion with heavy oil sample in different proportions and inspect rheological changes in resultant emulsion. In third phase of the study, both nanoparticles and solvent based emulsion were added to heavy oil sample and viscosity of resultant nano-emulsion was examined. For all test fluids, rheological measurements are presented at four different temperatures ranging from 100°F to 160°F. This unprecedented experimental work was conducted with two extremely viscous heavy oil samples having viscosity of approximately 77,000 cP and 350,000 cP at room temperature.
Addition of nanoparticles resulted in notable reduction in viscosity of both heavy oil samples. For each type of nanoparticles, viscosity reduction of 50 to 70% was achieved. The degree of viscosity alteration was observed to be a function of type of nanoparticles, their concentration, and fluid temperature. Moreover, optimum concentrations for maximum viscosity reduction, were identified for each metal oxide nanoparticles at different temperatures.
Using S/W emulsion, depending on volume fraction, viscosity reduction varying from 20 to 93% was achieved. In case of S/W emulsion containing nanoparticles, viscosity alteration strongly depended on type of nanoparticles added. Addition of copper oxide nanoparticles in S/W emulsion resulted in additional viscosity reduction of 10 to 30%. Iron oxide nanoparticles had adverse effect, if any, on the performance of S/W emulsion. Interestingly, nickel oxide nanoparticles either had improving or deteriorating effect depending on its concentration in S/W emulsion.
Cost analysis revealed that some of the test fluids cost less than $16 per barrel of oil and provided 40 to 50% viscosity reduction. The results are promising considering the fact that the cost presented were calculated based on purchase quote for a very small quantity and they will reduce significantly for field scale applications.
Remarkable results obtained in this study, confirm efficacy of nanoparticles and solvent based emulsion in reducing viscosity of heavy oil. This work rekindles the interest in non-thermal heavy oil recovery techniques such as chemical flooding, and provides a foundation for future core flooding studies
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Experimental and advanced computational modelling study of downhole elastomer seal assemblies
Full text linkElastomers seals are widely used in various drilling, completion, and production equipment. One such equipment is liner hanger which has become integral part of modern well designs. Failure of liner hanger seal assembly can compromise well integrity, and lead to severe health, safety, and environmental consequences. Concerns regarding reliability of elastomer seals in liner hanger assemblies have been raised by the regulators as well as industry.
This dissertation work provides detailed investigation of design, and failure of downhole elastomer seal assemblies using experimentally supported advanced computational modeling techniques. This work is partially supported by Bureau of Safety and Environmental Enforcement (BSEE) and it is set in the context of liner hanger assemblies. However, major outcomes of this research also applies to other downhole seal assemblies. Specific objectives of this dissertation are - (i) investigate performance of liner hanger seal assembly under various design, operational, and failure scenarios, (ii) develop operating envelops and identify critical parameters influencing performance of the elastomer seal assembly, (iii) develop a modelling tool for predicting leakage through elastomer seal interface considering surface characteristics, (iv) generate guidelines for design and qualification of elastomer seals and provide regulatory recommendations.
Novel technical aspects of this research work are – (i) studying material behavior of different elastomer material (NBR, EPDM, FKM, FEPM, FFKM, PTFE) under normal and downhole conditions, (ii) using the elastomer material data in true-scale finite element (FEA) models to evaluate equipment level performance of seal, (iii) scaled laboratory tests and analytical calculations to validate FEA models, and (iv) development of a leakage modelling tool that can predict leakage rates as a function of surface topography of seal interface and operating conditions.
Results from this dissertation indicate that type and design of seal equipment determines which elastomer properties need to be qualified. Hardness and elastic modulus alone may not be good predictors of fitness-for-service of seal assembly. For example, performance of expandable liner hanger seal assembly primarily depends on seal dimensions and elastomer shear modulus while performance of conventional liner hanger seal assembly mainly depends on elastomer bulk modulus. Selection of appropriate elastomer material for a certain application depends not only on chemical environment and temperature but also on assembly design, operational constraints, and thermal changes. Comparative evaluation demonstrated that conventional liner hanger seal assembly outperforms expandable liner hanger seal assembly in terms of contact pressure generated per unit energization but it is more prone to failure than expandable assembly.
Contact pressure at seal-pipe interface, as predicted by macro-scale FEA models, does not accurately indicate fluid pressure that can be effectively sealed. Leakage modelling studies demonstrated that surface characteristics of elastomer and fluid properties determines the contact pressure needed to achieve complete sealability. Leakage modelling approach developed in this work can be an invaluable tool in seal design workflow for determining target seal energization needed for complete sealability
Analysis and synthesis of conical coil springs
No full textSprings are mechanical devices that are employed to resist forces, store energy, absorb shocks, mitigate vibrations, or maintain parts contacting each other. Spring strips are commonly coiled in the forms of helixes for either extension or compression. Helical springs usually have cylindrical shapes that have constant coil diameter, constant pitch, and constant spring rate. Unlike
conventional cylindrical coil springs, the coil diameter of conically coiled springs is variable. They have conical or tapered shapes with a large coil diameter at the base and a small coil diameter at the top. The variable coil diameter enables conical coil springs to generate desired load-deflection relationships, have high lateral stability, and low buckling liability. In addition, conical compression springs can have significantly larger compression or shorter compressed height than conventional helical compression springs. The compressed height of a conical compression spring can reach its limit that is, the diameter of the spring wire if it is appropriately synthesized. The
height of an undeformed conical extension spring can have the height of its spring wire if the spring pitch is chosen to be zero. The shape of an undeformed conical extension spring can be flat if it is needed. The variable coil diameter of conical coil springs provides them with unique features but also raises their synthesis difficulties. Synthesizing conical coil springs that require large spring
compression or short, deformed spring height or constant spring rate is challenging. This research is motivated by surmounting the current challenges facing conical coil springs. In this research, different conical compression and extension springs will be modeled. Their performances will be simulated using the created models. The force-deflection relationships of conical coil springs will
be analyzed. The results from this research will provide useful guidelines for developing conical compression and extension springs
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Constrained Motion Analysis of Spacecraft Trajectory in Restricted Three Body Problem
Full text linkDue to the popularity of libration points, many satellites are being maintained on their desired trajectory. Indian space research organization has planned to launch the Aditya-L1 spacecraft to study about the Sun by 2021. James Webb Space Telescope has also been designed to observe deep space at L2 in the Sun-Earth system by 2021. The combined gravity of the Earth and the Sun keep satellite’s orbit locked at libration points. Though satellites enjoys an uninterrupted view of Sun and Earth all the time, they are affected by the solar radiation pressure (SRP) continuously. Due to the instability of collinear libration points, the certain amount of thrust is required to maintain the desired trajectory. This thesis introduces the Udwadia-Kalaba (UK) formulation of constrained dynamics as applied to the restricted three-body problem of the Sun-Earth-Spacecraft. A dynamic model of the restricted three-body system is presented to analyze the unconstrained motion of spacecraft. The results show the instability due to perturbation from the SRP. Then, the Udwadia-Kalaba formulation is applied to derive the equation of motion of spacecraft with additional constraints such that spacecraft maintains the desired trajectory at libration points. The results of exact amount of control acceleration with the directions are provided for spacecraft for the following three cases: i) maintaining position at the L1 considering the Earth’s circular orbit (i.e. CR3BP) ii) maintaining position at the L1 and L4 or L5 considering the Earth’s elliptical orbit (i.e. ER3BP) and iii) maintaining the three-dimension halo orbit around the L1 and L2 in CR3BP. The UK formulation is modified using Baumgarte’s stabilization method to allow to compute the results for the incorrect initial conditions (i.e. initial state deviations). In this case, the results are analyzed for the underdamped, overdamped and critically-damped systems. In addition, the delta-v is compared for the transient response with time-varying linear quadratic regulator (LQR). For fully constrained system, the control accelerations required to maintain the desired trajectory obtained by the UK technique are shown identical to those obtain via feedforward part of the time-varying LQR, as expected
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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