Phase Behaviour Modeling of Complex Hydrocarbon Systems Applicable to Solvent Assisted Recovery Processes

2014 ◽  
Author(s):  
Bita Bayestehparvin ◽  
Hossein Nourozieh ◽  
Mohammad Kariznovi ◽  
Jalal Abedi
Keyword(s):  
Phase Behaviour ◽  
Recovery Processes

scholarly journals Simulation of Surfactant Oil Recovery Processes and the Role of Phase Behaviour Parameters

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 983 ◽  
Author(s):  
Pablo Druetta ◽  
Francesco Picchioni
Keyword(s):  
Oil Recovery ◽  
Phase Behaviour ◽  
Residual Oil ◽  
Two Phase ◽  
Oil Saturation ◽  
Recovery Processes ◽  
Fluid Properties ◽  
Injection Water ◽  
Finitedifference Method

Chemical Enhanced Oil Recovery (cEOR) processes comprise a number of techniques whichmodify the rock/fluid properties in order to mobilize the remaining oil. Among these, surfactantflooding is one of the most used and well-known processes; it is mainly used to decrease the interfacialenergy between the phases and thus lowering the residual oil saturation. A novel two-dimensionalflooding simulator is presented for a four-component (water, petroleum, surfactant, salt), two-phase(aqueous, oleous) model in porous media. The system is then solved using a second-order finitedifference method with the IMPEC (IMplicit Pressure and Explicit Concentration) scheme. The oilrecovery efficiency evidenced a strong dependency on the chemical component properties and itsphase behaviour. In order to accurately model the latter, the simulator uses and improves a simplifiedternary diagram, introducing the dependence of the partition coefficient on the salt concentration.Results showed that the surfactant partitioning between the phases is the most important parameterduring the EOR process. Moreover, the presence of salt affects this partitioning coefficient, modifyingconsiderably the sweeping efficiency. Therefore, the control of the salinity in the injection water isdeemed fundamental for the success of EOR operations with surfactants.

Observations of Frozen-Hydrated Microtubules

1990 ◽  
Vol 48 (1) ◽  
pp. 504-505
Author(s):  
D. Chrétien ◽  
D. Job ◽  
R.H. Wade
Keyword(s):  
Fourier Transforms ◽  
Structural Complexity ◽  
Image Contrast ◽  
Phase Behaviour ◽  
Experimental Conditions ◽  
Thin Sections ◽  
Surface Lattice ◽  
Cilia And Flagella ◽  
Outstanding Question

Microtubules are filamentary structures found in the cytoplasm of eukaryotic cells, where, together with actin and intermediate filaments, they form the components of the cytoskeleton. They have many functions and show various levels of structural complexity as witnessed by the singlet, doublet and triplet structures involved in the architecture of centrioles, basal bodies, cilia and flagella. The accepted microtubule model consists of a 25 nm diameter hollow tube with a wall made up of 13 paraxial protofilaments (pf). Each pf is a string of aligned tubulin dimers. Some results have suggested that the pfs follow a superhelix. To understand how microtubules function in the cell an accurate model of the surface lattice is one of the requirements. For example the 9x2 architecture of the axoneme will depend on the organisation of its component microtubules. We should also note that microtubules with different numbers of pfs have been observed in thin sections of cellular and of in-vitro material. An outstanding question is how does the surface lattice adjust to these different pf numbers?We have been using cryo-electron microscopy of frozen-hydrated samples to study in-vitro assembled microtubules. The experimental conditions are described in detail in this reference. The results obtained in conjunction with thin sections of similar specimens and with axoneme outer doublet fragments have already allowed us to characterise the image contrast of 13, 14 and 15 pf microtubules on the basis of the measured image widths, of the the image contrast symmetry and of the amplitude and phase behaviour along the equator in the computed Fourier transforms. The contrast variations along individual microtubule images can be interpreted in terms of the geometry of the microtubule surface lattice. We can extend these results and make some reasonable predictions about the probable surface lattices in the case of other pf numbers, see Table 1. Figure 1 shows observed images with which these predictions can be compared.

How to Evaluate Clinically Relevant Literature: Five Simple Rules for the Practicing Clinician in Stroke Neurorehabilitation

2020 ◽  
Author(s):  
Jonathan Sanching Tsay ◽  
Carolee Winstein
Keyword(s):  
Clinical Decision Making ◽  
Relevant Literature ◽  
Clinical Decision ◽  
Balance Sheets ◽  
Neural Connections ◽  
Recovery Processes ◽  
Immediate Recovery ◽  
Simple Rules ◽  
Busy Clinician ◽  
New Generation

Neurorehabilitation relies on core principles of neuroplasticity to activate and engage latent neural connections, promote detour circuits, and reverse impairments. Clinical interventions incorporating these principles have been shown to promote recovery while demoting compensation. However, many clinicians struggle to find evidence for these principles in our growing but nascent body of literature. Regulatory bodies and organizational balance sheets further discourage evidence-based, methodical, time-intensive, and efficacious interventions because practical needs often outweigh and dominate clinical decision making. Modern neurorehabilitation practices that result from these pressures favor strategies that encourage compensation over those that promote recovery. With a focus on helping the busy clinician evaluate the rapidly growing literature, we put forth five simple rules that direct clinicians toward intervention studies that value more enduring but slower biological recovery processes over the more alluring practical and immediate “recovery” mantra. Filtering emerging literature through this critical lens has the potential to change practice and lead to more durable long-term outcomes. This perspective is meant to serve a new generation of mechanistically minded clinicians, students, and trainees poised to not only advance our field but to also erect policy changes that promote recovery-based care of stroke survivors.

Phase Transitions in Phospholipid Monolayers Studied by Atomic Force Microscopy and Langmuir-Blodgett Technique

2008 ◽  
Vol 59 (11) ◽  
Author(s):  
Maria Tomoaia-Cotisel ◽  
Aurora Mocanu
Keyword(s):  
Atomic Force Microscopy ◽  
Lipid Membrane ◽  
Phase Behaviour ◽  
Membrane Interface ◽  
Force Microscopy ◽  
Langmuir Blodgett ◽  
Atomic Force ◽  
Phospholipid Monolayers ◽  
Air Water Interface ◽  
Condensed Liquid

The phase behaviour and surface structure of dipalmitoyl phosphatidyl choline (DPPC) monolayers at the air/water interface, in the absence and the presence of procaine, have been investigated by Langmuir-Blodgett (LB) technique and atomic force microscopy. The LB films were transferred on mica, at a controlled surface pressure, characteristic for the expanded liquid to condensed liquid phase transition of pure DPPC monolayers. The results indicate that procaine penetrates into and specifically interacts with phospholipid monolayers stabilizing the lipid membrane interface.

scholarly journals Double-Chain Cationic Surfactants: Swelling, Structure, Phase Transitions and Additive Effects

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3946
Author(s):  
Rui A. Gonçalves ◽  
Yeng-Ming Lam ◽  
Björn Lindman
Keyword(s):  
Phase Transitions ◽  
Phase Behaviour ◽  
Double Chain ◽  
Scanning Calorimetry ◽  
Alkyl Chains ◽  
X Ray Scattering ◽  
Amphiphilic Compounds ◽  
Liquid Phases ◽  
Lamellar Phases ◽  
Water Layers

Double-chain amphiphilic compounds, including surfactants and lipids, have broad significance in applications like personal care and biology. A study on the phase structures and their transitions focusing on dioctadecyldimethylammonium chloride (DODAC), used inter alia in hair conditioners, is presented. The phase behaviour is dominated by two bilayer lamellar phases, Lβ and Lα, with “solid” and “melted” alkyl chains, respectively. In particular, the study is focused on the effect of additives of different polarity on the phase transitions and structures. The main techniques used for investigation were differential scanning calorimetry (DSC) and small- and wide-angle X-ray scattering (SAXS and WAXS). From the WAXS reflections, the distance between the alkyl chains in the bilayers was obtained, and from SAXS, the thicknesses of the surfactant and water layers. The Lα phase was found to have a bilayer structure, generally found for most surfactants; a Lβ phase made up of bilayers with considerable chain tilting and interdigitation was also identified. Depending mainly on the polarity of the additives, their effects on the phase stabilities and structure vary. Compounds like urea have no significant effect, while fatty acids and fatty alcohols have significant effects, but which are quite different depending on the nonpolar part. In most cases, Lβ and Lα phases exist over wide composition ranges; certain additives induce transitions to other phases, which include cubic, reversed hexagonal liquid crystals and bicontinuous liquid phases. For a system containing additives, which induce a significant lowering of the Lβ–Lα transition, we identified the possibility of a triggered phase transition via dilution with water.

scholarly journals Phase Behaviour of Methane Hydrates in Confined Media

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 201
Author(s):  
Hao Bian ◽  
Lu Ai ◽  
Klaus Hellgardt ◽  
Geoffrey C. Maitland ◽  
Jerry Y. Y. Heng
Keyword(s):  
Phase Behaviour ◽  
Methane Hydrates ◽  
Scanning Calorimetry ◽  
Macroporous Silica ◽  
Interfacial Energies ◽  
Temperature Method ◽  
Hydrate Phase ◽  
Dissociation Temperature ◽  
Confined Media ◽  
Decomposition Behaviour

In a study designed to investigate the melting behaviour of natural gas hydrates which are usually formed in porous mineral sediments rather than in bulk, hydrate phase equilibria for binary methane and water mixtures were studied using high-pressure differential scanning calorimetry in mesoporous and macroporous silica particles having controlled pore sizes ranging from 8.5 nm to 195.7 nm. A dynamic oscillating temperature method was used to form methane hydrates reproducibly and then determine their decomposition behaviour—melting points and enthalpies of melting. Significant decreases in dissociation temperature were observed as the pore size decreased (over 6 K for 8.5 nm pores). This behaviour is consistent with the Gibbs–Thomson equation, which was used to determine hydrate–water interfacial energies. The melting data up to 50 MPa indicated a strong, essentially logarithmic, dependence on pressure, which here has been ascribed to the pressure dependence of the interfacial energy in the confined media. An empirical modification of the Gibbs–Thomson equation is proposed to include this effect.

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