bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nanoparticle Stabilized Carbon Dioxide in Water Foams for Enhanced Oil Recovery
Authors: Worthen Andrew J. , Bagaria Hitesh G. , Chen Yunshen , Bryant Steven L. , Huh Chun , Johnston Keith P. 
Published: April 2012

Abstract
Viscous C/W foams were generated without the use of polymers or surfactants by shearing CO2 and an aqueous phase containing partially hydrophobic silica nanoparticles in a beadpack filled with 180μm glass beads. Silica particles with 50% SiOH coverage were chosen because they have a hydrophilicity that falls between the 42% SiOH optimum foaming ability for A/W foams (Binks and Horozov 2005) and the 67% SiOH which gave maximum O/W emulsion stability (Binks and Lumsdon 2000). These 50% SiOH silica nanoparticles were found to be interfacially active for CO2-water systems, and stabilized the desired curvature of C/W foams. When the HCB of the nanoparticles is tuned to give contact angles less than 90°, the particles reside primarily in the water phase and C/W foams can be formed. Formation of C/W emulsions stabilized solely with nanoparticles is desirable because it does not require solvation of surfactant tails or polymer chains by CO2. Interfacially active nanoparticles can adsorb at the CO2 water interface without the need for solvation in CO2.
Properly designed nanoparticles generated foams that were more stable than foams generated with polymer-coated nanoparticles or with the nonionic surfactant Tergitol™ 15-S-20 alone. Macroscopic observations showed foams generated solely with 50% SiOH nanoparticles stayed bright white and opaque over 23 hours, while foams generated with PEG-coated silica particles or with surfactant alone resolved nearly completely. Foams generated solely with Tergitol™ 15-S-20 were unstable because surfactant molecules dynamically enter and leave the interface and thus do not provide long-term stabilization. Foams generated with PEG-coated silica particles, though initially very viscous, showed poor long-term stability because of the small particle size and poor solvation of PEG chains in CO2. The larger 50% SiOH nanoparticles strongly adsorbed at the CO2-water interface and provided a barrier around the CO2 bubbles, resulting in very stable foams.
Three-Phase Flow during Steam Chamber Rise
Authors: Murtaza Muhammad , Dehghanpour Hassan 
Published: April 2012

Abstract
During Steam Assisted Gravity Drainage (SAGD) process, a steam chamber is formed due to continous steam injection. This steam chamber first moves upward to the top of the reservoir and then spreads side ways. The upward displacement of the steam chamber is the key parameter, for determining the optimum rate of steam injection. Slow injection rate will give low oil recovery where as high injection rate will cause steam loss. Furthermore, the cost of steam is more than half of the total cost of the project. Therefore it is necessary to determine the accurate rate of steam chamber rise to make the process economic.
Recent experiments show that oil flow is coupled to water flow during three-phase gravity drainage in water-wet system. In this paper, we argue that this type of flow coupling can be significant during SAGD. We extend Butler (1987) analytic model for the rise of interfering steam chambers to account for three phase flow and flow coupling.
We also show the significance of flow coupling by solving a simple numerical example. We observe that by including three-phase drainage and the coupling flow in the steam chamber, the vertical rise velocity of steam chamber increases. Moreover the steam chamber rise velocity is sensitive to viscosity-temperature characterstics (m) of oil. As the value of m decreases the rise velocity increases. Furthermore, we compre the model predictions with measured values from five fields, and one experiment.
2-D Visualisation of Unstable Waterflood and Polymer Flood for Displacement of Heavy Oil
Authors: Skauge Arne , Ormehaug Per Arne , Gurholt Tiril , Vik Bartek , Bondino Igor , Hamon Gerald 
Published: April 2012

Abstract
Waterflooding and polymer assisted waterflood in heavy oil reservoirs has currently gaining great attention. Enhanced water injection schemes represent an alternative in cases where thermal methods are either impractical or uneconomic. This study describes and analyses the oil mobilization by imaging the oil displacement at adverse mobility by injection of brine and polymer. The objectives were to improve description of viscous instabilities, mechanisms for finger growth, water channeling at adverse mobility ratio, and oil mobilization by polymers.
Experiments have been made on 2D (30cmx30cm Bentheimer slabs) studying waterflooding and tertiary polymer injection in extra heavy oils (2000cp and 7000cp). The sandstone represents a relatively homogeneous and high permeability porous medium. The experiments utilize gamma and X-ray source for porosity and saturation measurements, and an X-ray imaging system to visualize displacements and thereby quantify the underlying flow mechanisms and oil recovery.
At water wet condition capillary smears the front and prevents viscous fingers even at high adverse viscosity ratio. Changes in wettability (aging the rock material) dampen the capillarity and fingers then become more pronounced. High microscopic recovery to waterfloods (up to 30% after 5 PV injected) were achieved, and most importantly a rather impressive further gain in oil recovery after polymer flooding reaching final recoveries of more than 60%. The waterflood creates multiple thin sharp fractal-like fingers that propagate in the Bentheimer sandstone material. The 2D X-ray imaging describes the finger formation, growth, and also the later water channels formed. Polymer injection gives a fast increase in oil production, and analysis from the imaging proves that the oil is mainly produced through the established water channels.
The 2-D experiments demonstrate the mechanisms of how heavy oil is mobilized by polymer injection. Saturation maps were accurately measured by means of X-ray scans and this enabled the visualization of flow instability, establishment of water channels and oil mobilization with high resolution.
Rheology and Transport of Improved EOR Polymers under Harsh Reservoir Conditions
Authors: Kulawardana Erandimala U. , Koh Heesong , Kim Do Hoon , Liyanage Pathma J. , Upamali Karasinghe A. , Huh Chun , Weerasooriya Upali , Pope Gary A. 
Published: April 2012

Abstract
New polymers that are stable in harsh environments (high salinity/hardness and high temperature) are in high demand because of the need for chemical EOR in oil reservoirs with these conditions. Commonly used partially hydrolyzed polyacrylamides (HPAM) have been successfully used in the field for decades, but they hydrolyze at high temperature and eventually precipitate in the presence of high concentrations of divalent cations. This paper mainly focuses on rheology and transport behavior of scleroglucan (non-ionic polysaccharide) and N-vinylpyrrolidone (NVP)-polyacrylamide (AM) co-polymer. The rigid, rod-like, triple helical structure of scleroglucan imparts exceptional stability and its non-ionic functionality makes it insensitivity to salinity and hardness. By a different mechanism, NVP in modified HPAM protects the polymer's amide group against thermal hydrolysis, i.e., by sterically hindering the amide group. This allows maintaining high viscosity even in high salinity brines at high temperature. Both scleroglucan and NVP co- or ter-polymers show good filterability and transport properties in sandstone and carbonate cores at high temperature and in brine with high salinity and hardness. Therefore, both polymers are promising candidates for polymer flooding, surfactant-polymer flooding and alkali-surfactant-polymer flooding in hard brine at high temperature, but must be evaluated under specific reservoir conditions.
Potential for In Situ Combustion in Depleted Conventional Oil Reservoirs
Authors: Moore R. G. , Mehta S. A. , Ursenbach M. G. , Gutiérrez D. 
Published: April 2012

Abstract
In oil producing regions like the US Mid-Continent, there are a large number of mature conventional oil fields that have reached or are approaching their production limit by conventional techniques, however, current strong oil prices and security issues justify additional EOR/IOR efforts. Air injection-based techniques (fireflooding or in situ combustion) have been demonstrated to provide commercially successful recovery from medium and light oils reservoirs. While the history of air injection-based EOR is littered with the perception of failed projects, many of the failures were associated with low oil prices. In other cases, failures were due to compressor problems, or incorrect concepts of how air injection processes operate. Ineffective ignitions, failure to inject enough air, and applications in reservoirs that had no hope of success explain the trouble with many past projects.
This paper reviews some of the successful air injection projects in higher gravity oil reservoirs and discusses the elements that are critical for success. These include the ability to ignite and continuously burn a fraction of the oil at reservoir conditions, the suitability of the reservoir for a gas-injection based recovery process, the availability and suitability of preexisting infrastructure, and a reasonable prediction of how much air should be injected and how much oil recovery could be expected. The paper also discusses possible options for taking advantage of the product gas stream.
The purpose of this paper is to arm the petroleum engineer with the relevant information and the right set of questions to ask when considering the application of air injection in a given field.
Experimental and Modeling Study of Multicontact Miscible Displacements
Authors: Shojaei Hasan , Rastegar Reza , Jessen Kristian 
Published: April 2012

Abstract
In order to estimate the potential incremental hydrocarbon recovery by CO2 injection, compositional reservoir simulators are commonly used in the industry. Successful design and implementation of CO2 injection processes rely in part on the accuracy by which the available simulation tools can represent the physics that govern the displacement behavior in a reservoir. In this paper, we investigate the accuracy of some physical models that are frequently used to describe dispersive mixing and mass transfer in compositional reservoir simulation.
We have designed a quaternary analog fluid system (alcohol-water-hydrocarbon) that mimics the phase behavior of CO2- hydrocarbon mixtures at high pressure and temperature. A porous medium was designed using PolyTetraFlouroEthylene (PTFE) materials to ensure that the analog oil acts as the wetting phase, and the properties of the porous medium were characterized in terms of porosity, permeability and dispersivity. Relative permeability and interfacial tension (IFT) measurements were also performed to delineate interactions between the fluid system and the porous medium.
The effluent concentrations from 2-component first-contact miscible displacement experiments exhibit a tailing behavior that is attributed to imperfect sweep of the porous medium: a feature that is not captured by normal dispersion models. To represent this behavior in displacement calculations, we use a dual-porosity model including mass transfer between flowing and stagnant porosities. Two 4-component two-phase displacement experiments were performed at multicontact miscible conditions and the effluent concentrations were interpreted by numerical calculations.
We demonstrate that the accuracy of our displacement calculations relative to the experimental observations is sensitive to the selected models for dispersive mixing, mass transfer between flowing and stagnant porosities, and IFT scaling of relative permeability functions. We also demonstrate that numerical calculations substantially agree with the experimental observations for some physical models with limited need for model parameter adjustment.
The work presented in this paper is directly applicable to the study and design of EOR/sequestration processes through an improved understanding of dispersive mixing and mass transfer in these processes.
Nanofluid System Improves Post Frac Oil and Gas Recovery in Hydrocarbon Rich Gas Reservoirs
Authors: Penny Glenn , Zelenev Andrei , Lett Nathan , Paktinat Javad , O’Neil Bill 
Published: April 2012

Abstract
The primary purpose of using surfactants in stimulating hydrocarbon rich gas reservoirs is to reduce interfacial tension, and/or modify contact angle and reservoir wettability. However, many surfactants either adsorb rapidly within the first few inches of the formation, or negatively impact reservoir wettability, thus reducing their effectiveness in lowering capillary pressure. These phenomena can result in phase trapping of the injected fluid adversely impacting oil and gas production.
This study describes experimental and field studies comparing various common surfactants used in oil bearing formations including alcohol ethoxylates, EO-PO block copolymers, ethoxylated amines and a multi-phase complex nano fluid system to determine their impact on oil recovery and adsorption tendencies when injected through 5-foot and 1 ft sand columns. Ammot cell tests were used to evaluate imbibition of oil and water and a core flow apparatus was used to evaluate regained relative permeabilities. The results are correlated with surface energies of actual formation materials, oils and treating fluids. The results are used to select formulations containing surfactant, solvents and co-solvents to apply within the fracturing fluid to decrease adsorption, eliminate post treatment emulsions and improve oil and gas recovery in hydrocarbon rich gas wells.
Double-Layer Expansion: Is It A Primary Mechanism of Improved Oil Recovery by Low-Salinity Waterflooding?
Authors: Nasralla Ramez A. , Nasr-El-Din Hisham A. 
Published: April 2012

Abstract
Several mechanisms which could contribute to improved oil recovery (IOR) by low-salinity waterflooding have been proposed. However, the main mechanism is still debated. Nasralla et al. (2011a) showed that low-salinity water has an impact on the electrical charges at oil/brine and rock/brine interfaces, and it causes expansion of the double layer, which is the main reason behind wettability alteration and high oil recovery. Nevertheless, double-layer expansion by low-salinity water might contribute, but not be the primary mechanism. Therefore, this paper investigates this mechanism and shows how it is involved in the process of IOR.
Electrical surface charge is a function of brine's pH, so the injected brine's pH was manipulated to show how oil recovery during low-salinity waterflooding depends on changes in electrical charges. Coreflood experiments were conducted using Berea sandstone cores 20 in. long; different brines (TDS varies from 0.5 to 55 kmg/l) were injected. Furthermore, zeta potential at rock/brine and oil/brine interfaces was measured for the brines used at different pHs. The contact angle technique was used to evaluate the alteration of rock wettability by the same brine at a different pH.
Zeta potential results showed that decreasing low-salinity brines’ pH makes the electrical charges at both oil/brine and brine/rock interfaces weakly negative, which reduces the repulsion forces between oil and rock, and as a result the rock becomes more oil-wet, which was confirmed by contact angle measurements. Moreover, coreflood experiments indicated that injecting low-salinity brine at lower pH recovered less amount of oil compared to the original pH because of the elimination of the low-salinity water effect on electrical charges. In conclusion, expansion of the double layer is a dominant mechanism of oil recovery improvement by low-salinity waterflooding.
Polymer Flooding a ~500-cp Oil
Authors: Moe Soe Let K. P. , Manichand R. N. , Seright R. S. 
Published: April 2012

Abstract
Relatively high oil prices, modest polymer prices, and advances that promote higher injectivity for polymer solutions have allowed polymer flooding to be applied in reservoirs with notably more viscous oils than in previous years. This paper describes a polymer flooding pilot project in the Tambaredjo field in Suriname. The average viscosity of the produced oil is ~1,700 cp, but solution gas reduces the effective oil viscosity in the reservoir to 400–600 cp (through the "foamy oil" mechanism). Interestingly, the primary drive mechanism in the pilot area is compaction—leading to ~20% OOIP recovery. Because various restrictions preclude application of thermal methods, polymer flooding was explored as a means to enhance oil recovery. The average permeability of the sand exceeds 4darcys, but the level of heterogeneity is significant (&gt;10:1 permeability contrast is common). The first simulation efforts suggested that injection of 25–40-cp polymer solutions might be optimum, considering both displacement and injectivity. Consequently, ~40-cp polymer solutions were injected during the first part of the pilot. However, later analysis revealed that sweep efficiency could be improved significantly using polymer solutions up to 160 cp. Although injection was done at pressures below what was believed to be the formation parting pressure, injectivity data from several water injection cycles shows that partition of the formation followed by partial sustenance of the fracture did occur. Analysis of produced water salinities, polymer and tracer concentrations, water/oil ratios (WOR), and inter-well pressure responses all indicated that severe channeling (i.e., through fracture-like features) did not occur. Instead, analysis of the project response indicated that (1) sweep could benefit from injecting more viscous polymer solutions, (2) injectivity for more viscous polymers would not be a problem because of controlled (i.e., not detrimental) fracture extension, and (3) oil production rates could be enhanced (without sacrificing WOR) by increasing injection rates. Consequently, these ideas are currently being field tested in our project. This paper details results to date for this polymer pilot.
Biomechanical In Vitro - Stability Testing on Human Specimens of a Locking Plate System Against Conventional Screw Fixation of a Proximal First Metatarsal Lateral Displacement Osteotomy
Authors: Arnold Heino , Stukenborg-Colsman Christina , Hurschler Christof , Seehaus Frank , Bobrowitsch Evgenij , Waizy Hazibullah 
Published: April 2012

Introduction:The aim of this study was to examine resistance to angulation and displacement of the internal fixation of a proximal first metatarsal lateral displacement osteotomy, using a locking plate system compared with a conventional crossed screw fixation.Materials and Methodology:Seven anatomical human specimens were tested. Each specimen was tested with a locking screw plate as well as a crossed cancellous srew fixation. The statistical analysis was performed by the Friedman test. The level of significance was p = 0.05.Results:We found larger stability about all three axes of movement analyzed for the PLATE than the crossed screws osteosynthesis (CSO). The Friedman test showed statistical significance at a level of p = 0.05 for all groups and both translational and rotational movements.Conclusion:The results of our study confirm that the fixation of the lateral proximal first metatarsal displacement osteotomy with a locking plate fixation is a technically simple procedure of superior stability.
Cryopreservation Effect on Proliferative and Chondrogenic Potential of Human Chondrocytes Isolated from Superficial and Deep Cartilage
Authors: Muiños-López Emma , Rendal-Vázquez Mª Esther , Hermida-Gómez Tamara , Fuentes-Boquete Isaac , Díaz-Prado Silvia , Blanco Francisco J 
Published: April 2012

Objectives:To compare the proliferative and chondrogenic potential of fresh and frozen chondrocytes isolated from superficial and deep articular cartilage biopsies.Materials and Methodology:The study included 12 samples of fresh and frozen healthy human knee articular cartilage. Cell proliferation was tested at 3, 6 and 9 days. Studies of mRNA quantification, protein expression and immunofluorescence for proliferation and chondrogenic markers were performed.Results:Stimulation of fresh and frozen chondrocytes from both superficial and deep cartilage with fetal bovine serum produced an increase in the proliferative capacity compared to the non-stimulated control group. In the stimulated fresh cells group, the proliferative capacity of cells from the deep biopsy was greater than that from cells from the superficial biopsy (0.046vs0.028, respectively, p<0.05). There was also a significant difference between the proliferative capacity of superficial zone fresh (0.028) and frozen (0.051) chondrocytes (p<0.05).CCND1mRNA and protein expression levels, and immunopositivity forKi67revealed a higher proliferative capacity for fresh articular chondrocytes from deep cartilage. Regarding the chondrogenic potential, stimulated fresh cells showed higherSOX9andCol IIexpression in chondrocytes from deep than from superficial zone (p<0.05,Tstudent test).Conclusions:The highest rate of cell proliferation and chondrogenic potential of fresh chondrocytes was found in cells obtained from deep cartilage biopsies, whereas there were no statistically significant differences in proliferative and chondrogenic capacity between biopsy origins with frozen chondrocytes. These results indicate that both origin and cryopreservation affect the proliferative and chondrogenic potential of chondrocytes.
Derivation and Validation of a Cytokine-Based Assay to Screen for Acute Rejection in Renal Transplant Recipients
Authors: De Serres Sacha A. , Mfarrej Bechara G. , Grafals Monica , Riella Leonardo V. , Magee Ciara N. , Yeung Melissa Y. , Dyer Christine , Ahmad Usaila , Chandraker Anil , Najafian Nader 
Published: April 2012

Summary

Background and objectives
Acute rejection remains a problem in renal transplantation. This study sought to determine the utility of a noninvasive cytokine assay in screening of acute rejection.

Design, setting, participants, & measurements
In this observational cross-sectional study, 64 patients from two centers were recruited upon admission for allograft biopsy to investigate acute graft dysfunction. Blood was collected before biopsy and assayed for a panel of 21 cytokines secreted by PBMCs. Patients were classified as acute rejectors or nonrejectors according to a classification rule derived from an initial set of 32 patients (training cohort) and subsequently validated in the remaining patients (validation cohort).

Results
Although six cytokines (IL-1β, IL-6, TNF-α, IL-4, GM-CSF, and monocyte chemoattractant protein-1) distinguished acute rejectors in the training cohort, logistic regression modeling identified a single cytokine, IL-6, as the best predictor. In the validation cohort, IL-6 was consistently the most accurate cytokine (area under the receiver-operating characteristic curve, 0.85; P=0.006), whereas the application of a prespecified cutoff level, as determined from the training cohort, resulted in a sensitivity and specificity of 92% and 63%, respectively. Secondary analyses revealed a strong association between IL-6 levels and acute rejection after multivariate adjustment for clinical characteristics (P<0.001).

Conclusions
In this pilot study, the measurement of a single cytokine can exclude acute rejection with a sensitivity of 92% in renal transplant recipients presenting with acute graft dysfunction. Prospective studies are needed to determine the utility of this simple assay, particularly for low-risk or remote patients.
Realization of a fuzzy controller with fuzzy dynamic correction
Authors: Vichuzhanin Vladimir 
Published: April 2012

Abstract
This article features results from a fuzzy controller with fuzzy dynamic correction for the non-linear control of objects with variable parameters. The methods described herein have been used on a fuzzy proportional-differential (PD) controller, and our results show that fuzzy dynamic correction can reduce overshoot and shorten the settling time of the controlled parameters.