Foam flooding is an established approach in Enhanced Oil Recovery (EOR) to recover a significant quantity of the residual oil left in the reservoir after primary and secondary recovery. However, foam flooding faces various problems due to low viscosity effect, which reduces its efficiency in recovering oil. Using surfactant to stabilize CO2foam may reduce mobility and improve areal and vertical sweep efficiency, but the potential weaknesses are such that high surfactant retention in porous media and unstable foam properties under high temperature reservoir conditions. Nanoparticles have higher adhesion energy to the fluid interface, which potentially stabilize longer lasting foams. Thus, this paper is aimed to investigate the CO2foam stability and mobility characteristics at different concentration of nanosilica, brine and surfactant. Foam generator has been used to generate CO2foam and analyze its stability under varying nanosilica concentration from 100 - 5000 ppm, while brine salinity and surfactant concentration ranging from 0 to 2.0 wt% NaCl and 0 – 10000 ppm, respectively. Foam stability was investigated through observation of the foam bubble size and the reduction of foam height inside the observation tube. The mobility was reduced as the concentration of nanosilica increased with the presence of surfactant. After 150 minutes of observation, the generated foam height reduced by 10%. Liquid with the presence of both silica nanoparticles and surfactant generated more stable foam with lower mobility. It can be concluded that the increase in concentration of nanosilica and addition of surfactant provided significant effects on the foam stability and mobility, which could enhance oil recovery.

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Extraction of tannin Rhizophora Mucronata barks by using two methods, which were soxhlet extraction and boiling were demonstrated in this study in order to evaluate the effective technique for extraction. Several parameters such as the type of solvent used, time of extraction, and sample size were specified. The extractant was then evaporated using vacuum rotary evaporator. The percentage of extractives and the characterization of condensed (Stiasny Index) and hydrolyzable tannins were all quantified. The milled barks with different sizes were introduced to the extraction using water, methanol, acetone, and toluene as a solvent for three, six and nine hours for Soxhlet extraction while for boiling only water were used as a solvent and at four, six and eight hours. Results demonstrated that extraction from the bark of Rhizophora Mucronata with water for six and nine hours extracted approximately 29 wt% and 13wt % for both soxhlet extraction and boiling respectively when coupled with vacuum rotary evaporator. The Soxhlet extraction method was superior as compared to boiling. The optimum parameters for the Soxhlet extraction were water as the solvent at six hours extraction with 0.5 mm of milled bark particles size that extracted 29 wt% of extractives. The condensed tannin and hydrolyzable tannin of the extractives using soxhlet extraction were approximately 76 wt% and 0.00133 wt% respectively.

The effect of different drying methods using spray dryer and rotary evaporator towards the physico-chemical properties and thermal stability of powdered tannin extractives from Rhizophora Mucronata bark was investigated. Prior to spray drying at 130°C and rotary evaporating at 80°C, tannin was extracted using water-based boiling extraction at temperature ranging from 80 to 90°C. Powdered tannin extractives obtained by spray dryer decomposed at higher temperature (at 270°C) than those using rotary evaporator (at 210°C). The powdered tannin extractives from spray dryer was higher in thermal stability due to the high crystallinity peak appeared from X-ray Powder Diffraction (XRD) analysis. Condensed and hydrolysable tannins were also quantified using Reverse-phase High Performance Liquid Chromatography (RP-HPLC) for both methods. Powdered tannins extractives using spray dryer contained 27.8% condensed tannins and 0.001% hydrolysable tannins, in which the condensed tannins are slightly higher in concentration than those formed using rotary evaporator which was 26.5%. The findings revealed that the used of spray dryer is more beneficial to obtain a stronger thermal stability and a higher concentration of powdered Rhizophora Mucronata bark tannins extractives