Formation of carbonate minerals by CO2 sequestration is a potential means to reduce atmospheric CO2 emissions. Vast amount of alkaline and alkali earth metals exist in silicate minerals that may be carbonated. Laboratory experiments carried out to study the dissolution rate in Pahang Sandstone, Malaysia, by CO2 injection at different flow rate in surficial condition. X-ray Powder Diffraction (XRD), Scanning Electron Microscope (SEM) with Energy Dispersive X-ray Spectroscopy (EDX), Atomic Absorption Spectroscopy (AAS) and weight losses measurement were performed to analyze the solid and liquid phase before and after the reaction process. The weight changes and mineral dissolution caused by CO2 injection for two hours CO2 bubbling and one week' aging were 0.28% and 18.74%, respectively. The average variation of concentrations of alkaline earth metals in solution varied from 22.62% for Ca(2+) to 17.42% for Mg(2+), with in between 16.18% observed for the alkali earth metal, potassium. Analysis of variance (ANOVA) test is performed to determine significant differences of the element concentration, including Ca, Mg, and K, before and after the reaction experiment. Such changes show that the deposition of alkali and alkaline earth metals and the dissolution of required elements in sandstone samples are enhanced by CO2 injection.
Due to partial understanding of mechanisms involved in application of ultrasonic waves as enhanced oil recovery method, series of straight (normal), and ultrasonic stimulated water-flooding experiments were conducted on a long unconsolidated sand pack using ultrasonic transducers. Kerosene, vaseline, and SAE-10 (engine oil) were used as non-wet phase in the system. In addition, a series of fluid flow and temperature rise experiments were conducted using ultrasonic bath in order to enhance the understanding about contributing mechanisms. 3-16% increase in the recovery of water-flooding was observed. Emulsification, viscosity reduction, and cavitation were identified as contributing mechanisms. The findings of this study are expected to increase the insight to involving mechanisms which lead to improving the recovery of oil as a result of application of ultrasound waves.
Engineered aluminum oxide (Al2O3), titanium dioxide (TiO2), and silicon dioxide (SiO2) nanoparticles (NPs) are utilized in a broad range of applications; causing noticeable quantities of these materials to be released into the environment. Issues of how and where these particles are distributed into the subsurface aquatic environment remain as major challenges for those in environmental engineering. In this study, transport and retention of Al2O3, TiO2, and SiO2 NPs through various saturated porous media were investigated. Vertical columns were packed with quartz-sand, limestone, and dolomite grains. The NPs were introduced as a pulse suspended in aqueous solutions and breakthrough curves in the column outlet were generated using an ultraviolet-visible spectrophotometer. It was found that Al2O3 and TiO2 NPs are easily transported through limestone and dolomite porous media whereas NPs recoveries were achieved two times higher than those found in the quartz-sand. The highest and lowest SiO2-NPs recoveries were also achieved from the quartz-sand and limestone columns, respectively. The experimental results closely replicated the general trends predicted by the filtration and DLVO calculations. Overall, NPs mobility through a porous medium was found to be strongly dependent on NP surface charge, NP suspension stability against deposition, and porous medium surface charge and roughness.
In this work, the potential of CO₂ mineral carbonation of brucite (Mg(OH)2) derived from the Mount Tawai peridotite (forsterite based (Mg)₂SiO4) to produce thermodynamically stable magnesium carbonate (MgCO3) was evaluated. The effect of three main factors (reaction temperature, particle size, and water vapor) were investigated in a sequence of experiments consisting of aqueous acid leaching, evaporation to dryness of the slurry mass, and then gas-solid carbonation under pressurized CO2. The maximum amount of Mg converted to MgCO₃ is ~99%, which occurred at temperatures between 150 and 175 °C. It was also found that the reduction of particle size range from >200 to <75 µm enhanced the leaching rate significantly. In addition, the results showed the essential role of water vapor in promoting effective carbonation. By increasing water vapor concentration from 5 to 10 vol %, the mineral carbonation rate increased by 30%. This work has also numerically modeled the process by which CO₂ gas may be sequestered, by reaction with forsterite in the presence of moisture. In both experimental analysis and geochemical modeling, the results showed that the reaction is favored and of high yield; going almost to completion (within about one year) with the bulk of the carbon partitioning into magnesite and that very little remains in solution.
The impact of ionic strength (from 0.003 to 500mM) and salt type (NaCl vs MgCl2) on transport and retention of titanium dioxide (TiO2) nanoparticles (NPs) in saturated limestone porous media was systematically studied. Vertical columns were packed with limestone grains. The NPs were introduced as a pulse suspended in aqueous solutions and breakthrough curves in the column outlet were generated using an ultraviolent-visible spectrometry. Presence of NaCl and MgCl2 in the suspensions were found to have a significant influence on the electrokinetic properties of the NP aggregates and limestone grains. In NaCl and MgCl2 solutions, the deposition rates of the TiO2-NP aggregates were enhanced with the increase in ionic strength, a trend consistent with traditional Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Furthermore, the NP aggregates retention increased in the porous media with ionic strength. The presence of salts also caused a considerable delay in the NPs breakthrough time. MgCl2 as compared to NaCl was found to be more effective agent for the deposition and retention of TiO2-NPs. The experimental results followed closely the general trends predicted by the filtration and DLVO calculations. Overall, it was found that TiO2-NP mobility in the limestone porous media depends on ionic strength and salt type.
Treated Rhizopora mucronata tannin (RMT) as a corrosion inhibitor for carbon steel and copper in oil and gas facilities was investigated. Corrosion rate of carbon-steel and copper in 3wt% NaCl solution by RMT was studied using chemical (weight loss method) and spectroscopic (FTIR) techniques at various temperatures in the ranges of 26-90°C. The weight loss data was compared to the electrochemical by the application of Faraday's law for the conversion of corrosion rate data from one system to another. The inhibitive efficiency of RMT was compared with commercial inhibitor sodium benzotriazole (BTA-S). The best concentration of RMT was 20% (w/v), increase in concentration of RMT decreased the corrosion rate and increased the inhibitive efficiency. Increase in temperature increased the corrosion rate and decreased the inhibitive efficiency but, the rate of corrosion was mild with RMT. The FTIR result shows the presence of hydroxyl group, aromatic group, esters and the substituted benzene group indicating the purity of the tannin. The trend of RMT was similar to that of BTA-S, but its inhibitive efficiency for carbon-steel was poor (6%) compared to RMT (59%). BTA-S was efficient for copper (76%) compared to RMT (74%) at 40% (w/v) and 20% (w/v) concentration respectively. RMT was efficient even at low concentration therefore, the use of RMT as a cost effective and environmentally friendly corrosion inhibiting agent for carbon steel and copper is herein proposed.
Theoretically, Ultrasound method is an economical and environmentally friendly or "green" technology, which has been of interest for more than six decades for the purpose of enhancement of oil/heavy-oil production. However, in spite of many studies, questions about the effective mechanisms causing increase in oil recovery still existed. In addition, the majority of the mechanisms mentioned in the previous studies are theoretical or speculative. One of the changes that could be recognized in the fluid properties is viscosity reduction due to radiation of ultrasound waves. In this study, a technique was developed to investigate directly the effect of ultrasonic waves (different frequencies of 25, 40, 68 kHz and powers of 100, 250, 500 W) on viscosity changes of three types of oil (Paraffin oil, Synthetic oil, and Kerosene) and a Brine sample. The viscosity calculations in the smooth capillary tube were based on the mathematical models developed from the Poiseuille's equation. The experiments were carried out for uncontrolled and controlled temperature conditions. It was observed that the viscosity of all the liquids was decreased under ultrasound in all the experiments. This reduction was more significant for uncontrolled temperature condition cases. However, the reduction in viscosity under ultrasound was higher for lighter liquids compare to heavier ones. Pressure difference was diminished by decreasing in the fluid viscosity in all the cases which increases fluid flow ability, which in turn aids to higher oil recovery in enhanced oil recovery (EOR) operations. Higher ultrasound power showed higher liquid viscosity reduction in all the cases. Higher ultrasound frequency revealed higher and lower viscosity reduction for uncontrolled and controlled temperature condition experiments, respectively. In other words, the reduction in viscosity was inversely proportional to increasing the frequency in temperature controlled experiments. It was concluded that cavitation, heat generation, and viscosity reduction are three of the promising mechanisms causing increase in oil recovery under ultrasound.
Ascorbic acid was used for the first time to synthesize cellulose nanoparticles (CNP) extracted from okra mucilage. The physical properties of the CNP including their size distribution, and crystalline structures were investigated. The rheological properties of the cellulose nanofluid (CNF) were compared with the bulk okra mucilage and commercial polymer xanthan. The interfacial properties of the CNF at the interface of oil-water (O/W) system were investigated at different concentrations and temperatures. The effects of the interaction between the electrolyte and ultrasonic were determined. Core flooding experiment was conducted at reservoir condition to justify the effect of the flow behaviour and disperse phase behaviour of CNF on additional oil recovery. The performance of the CNF was compared to conventional EOR chemical. The combined method of ultrasonic, weak-acid hydrolysis and nanoprecipitation were effective in producing spherical and polygonal nanoparticles with a mean diameter of 100 nm, increased yield of 51% and preserved crystallinity respectively. The zeta potential result shows that the CNF was stable, and the surface charge signifies long term stability of the fluid when injected into oil field reservoirs. The CNF, okra and xanthan exhibited shear-thinning and pseudoplastic behaviour. The IFT decreased with increase in concentration of CNF, electrolyte and temperature. The pressure drop data confirmed the stability of CNF at 120°C and the formation of oil bank was enough to increase the oil recovery by 20%. CNF was found to be very effective in mobilizing residual oil at high-temperature high-pressure (HTHP) reservoir condition. The energy and cost estimations have shown that investing in ultrasonic-assisted weak-acid hydrolysis is easier, cost-effective, and can reduce energy consumption making the method economically advantageous compared to conventional methods.
Ultrafiltration has been proven to be very effective in the treatment of oil-in-water emulsions, since no chemical additives are required. However, ultrafiltration has its limitations, the main limits are concentration polarization resulting to permeate flux decline with time. Adsorption, accumulation of oil and particles on the membrane surface which causes fouling of the membrane. Studies have shown that the ultrasonic is effective in cleaning of fouled membrane and enhancing membrane filtration performance. But the effectiveness also, depends on the selection of appropriate membrane material, membrane geometry, ultrasonic module design, operational and processing condition. In this study, a hollow and flat-sheet polyurethane (PU) membranes synthesized with different additives and solvent were used and their performance evaluated with oil-in-water emulsion. The steady-state permeate flux and the rejection of oil in percentage (%) at two different modes were determined. A dry/wet spinning technique was used to fabricate the flat-sheet and hollow fibre membrane (HFMs) using Polyethersulfone (PES) polymer base, Polyvinylpyrrolidone (PVP) additive and N, N-Dimethylacetamide (DMAc) solvent. Ultrasonic assisted cross-flow ultrafiltration module was built to avoid loss of ultrasonic to the surrounding. The polyurethane (PU) was synthesized by polymerization and sulphonation to have an anionic group (-OH; -COOH; and -SO3H) on the membrane surface. Changes in morphological properties of the membrane had a significant effect on the permeate flow rate and oil removal. Generation of cavitation and Brownian motion by the ultrasonic were the dominant mechanisms responsible for ultrafiltration by cracking the cake layers and reducing concentration polarization at the membrane surface. The percentage of oil after ultrafiltration process with ultrasonic is about 90% compared to 49% without ultrasonic. Ultrasonic is effective in enhancing the membrane permeate flux and controlling membrane fouling.
Ascorbic acid was used for the first time to synthesize crystalline starch nanoparticles (CSNP). The physical properties of the CSNP were investigated. Rheological properties of the crystalline starch nanofluid (CSNF) were compared with native cassava starch (CS) and commercial polymer xanthan. Interfacial properties of the CSNF at the interface of oil and water (O/W) were investigated at different concentrations and temperatures. Wettability alteration efficiency of CSNF on oil-wet sandstone surface was investigated using the sessile drop method. Core flooding experiment was conducted at reservoir conditions. The methods were effective in producing spherical and polygonal nanoparticles with a mean diameter of 100 nm and increased in crystallinity of 7%. Viscosity increased with increase in surface area and temperature of the CSNF compared to a decrease in viscosity as the temperature increases for xanthan. Interfacial tension (IFT) decreased with increase in concentration of CSNF, electrolyte and temperature. The results show that CSNF can change the wettability of sandstone at low concentration, high salinity and elevated temperature. Pressure drops data shows stability of CSNF at 120 °C. The formation of oil bank was enough to increase oil recovery by 23%.