Theoretical and experimental investigation of effect of salinity and asphaltene on IFT of brine and live oil samples

Several factors influence the IFT of oil and formation water. These factors are rooted in the complex composition of oil, presence of different salts in water, water salinity, temperature, and pressure of reservoir. In the first part of this paper, effect of salinity on IFT between brine and an Iranian live oil sample has been studied experimentally. It is observed that IFT increases almost linearly with brine concentration. Also, linear increasing behavior of IFT with respect to pressure is obviously seen. Then, using thermodynamic properties such as surface excess concentration, chemical potential, chemical activity, and activity coefficient, results were analyzed and observed effect of salinity and pressure were justified thermodynamically. In the second part, the effect of asphaltene on IFT reduction has been studied. In previous works, the investigators extracted resin and asphaltene and then examined their effects on IFT in the absence of other fractions of oil phase. We believe that all fractions play a role in this phenomenon so, in this paper, the effect of natural surfactants of oil phase on IFT has been investigated in presence of all fractions of oil. Hence, SARA test was performed on all samples. Then, IFT between oil samples and brine were measured using captive drop instrument at 25 °C and 3000 psia. Results showed that neither asphaltene content nor asphaltene/resin ratio is a good indicator for effect of asphaltene on IFT, whereas colloidal instability index could be a useful tool to predict asphaltene effect on IFT.

Obtaining artificial carnallites from magnesium chloride brines

The excess of magnesium chloride brines is formed during the polymineral ores processing in order to obtain potassium sulfate. One way to regenerate such brines is to produce artificial carnallite. It is necessary to purify these brines from sulfates for their further use as raw materials for the artificial carnallite production. In this work, the process of desulfurization of magnesium chloride brines with a solution of calcium chloride is studied. The temperature and the processing time, the magnesium chloride solutions concentration and the consumption of desulfurizing agent (calcium chloride) influence on the degree of magnesium chloride solutions purification from sulfate ions was determined. It has been established that almost all sulfate ions interact with calcium ion in 15 minutes and the desulfurization degree reaches 98,08 %. The increase in duration of the suspension mixing is necessary in order to establish equilibrium in the system and relieve the supersaturation in the solution. It has been shown that with increasing solutions saturation with MgCl2, the degree of the magnesium chloride brines purification from SO4 2– ion increases. Complete precipitation of calcium sulfate requires a certain excess concentration of calcium chloride.

An Interaction of Anionic- and Cationic-Rich Mixed Surfactants in Aqueous Medium through Physicochemical Properties at Three Different Temperatures

The mixed micellization of aqueous binary mixtures of DTAB-rich and SDS-rich surfactants, comprising sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB) is studied in aqueous solution by using the physicochemical properties (PCPs) at three different temperatures (T = 293.15, 298.15, and 303.15 K) and P=0.1 MPa. The DTAB concentration is varied from 0.0001 to 0.03 M/mol·L−1 in the ∼0.01 M/mol·L−1 SDS solution, while the concentration of SDS is varied from 0.001 to 0.015 M/mol·L−1 in the ∼0.005 M/mol·L−1 DTAB. The stable formulations have been obtained by employing the DTAB-rich and SDS-rich surfactants solutions in 3 : 1 ratio. Therefore, different phases and aggregated states formed in the ternary combinations of DTAB/SDS/H2O have been identified and described. The calculated PCPs have been utilized for determining the nature of the solute-solvent interaction (SLS0I). With increasing surfactants concentration, the polarisation of the solution also increases along with an increase in relative viscosity (ηr), viscous relaxation time (τ), and surface excess concentration (Γmax). However, the surface area of the molecule (Amin), hydrodynamic volume (Vh), and hydrodynamic radius (Rh) decrease along with an increase in surfactants concentration.

Fabrication and Characteristics of Yb-Doped Silica Fibers Produced by the Sol-Gel Based Granulated Silica Method

Combining the sol-gel method for fiber material production with the granulated silica method for preform assembly results in a robust method that offers a high degree of freedom regarding both the composition and the geometry of the produced fiber. Using this method, two types of Yb-doped silica glass composition, that feature an excess in P concentration with respect to Al, have been prepared. The elemental distributions in a fiber core were analyzed by scanning transmission electron microscopy (STEM). The elemental mapping shows a similar localization of Al, P and Yb through the microstructure. In addition, the influence of the variation in the co-dopant concentration, with respect to Yb, on the fiber properties has been investigated. The results show an increase in the refractive index step and in the fiber’s transmission loss as the excess concentration of P increases. A significant contribution to the losses can be assigned to the existence of impurities such as iron, which was detected in our samples by mass spectrometer. Single exponential fluorescence decays with lifetimes of around 0.88 ms were measured for the two compositions. Finally, pumping at 976 nm a laser slope efficiency of 67% at 1031 nm was achieved for one of the fiber compositions.

Mixed Adsorption of Cetyltrimethylammonium Bromide and Triton X-100 Surfactants on Carbon Black

Adsorption of cationic cetyltrimethylammonium bromide (CTAB) and nonionic Triton X100 surfactants from their mixed aqueous solutions on graphitized carbon black (CB) have been studied. The adsorption isotherms of CTAB or Triton X100 from single solutions on CB surface shown to be of the Langmuir type. In the mixed solutions of CTAB and Triton X100 surfactants, the adsorption of CTAB or Triton X100 on CB decreased in the presence of the other surfactant due to competitive adsorption of the components. It was shown that the mole fraction of Triton X-100 on CB surface has been essentialy changed depending on total concentration of the surfactants mixture. At mixture concentration corresponding to the unsaturated monolayer, a strong synergetic effect was found when the surface excess concentration Triton X100 at the CB surface in the presence of CTAB is higher than that for Triton X-100 in the absence of CTAB.