صائب احمدی

This paper presents the feasibility of the removal of asphaltenes from aqueous solutions by using low- cost natural adsorbents such as light expanded clay aggregate (LECA), perlite and bentonite. The structure of adsorbents was characterized by XRD, FTIR, and SEM before and after the adsorption of asphaltenes. The effect of the adsorbent type, initial asphaltene concentration, particle size of the adsorbent and temperature on the adsorption capacity was investigated. The results showed that at the initial asphaltene concentration of 125 mg L-1, contact time of 24 h, temperature of 50°C and adsorbent dosage of 1 g, the removal of asphaltenes onto LECA, perlite and bentonite was 53.59, 93.01 and 99.77%, respectively. Also Langmuir and Freundlich models were applied to describe the experimental data. The results indicated a good fit by Langmuir isotherm. Thermodynamic parameters such as ∆H, ∆S and ∆G were also calculated. It was revealed that the adsorption was spontaneous and of exothermic nature, which was evident by decreasing the randomness of the dye at the solid and liquid interfaces. The characteristic results and dimensionless separation factor (RL) showed that perlite and bentonite can be employed as an alternative to commercial adsorbents for the removal of asphaltenes from the aqueous solution and oil.

This paper presents the feasibility (or possibility) of removal of asphaltenes from aqueous solutions by using low-cost natural adsorbents; such as, light expanded clay aggregate (LECA), perlite and bentonite. The effect of adsorbent type, initial asphaltene concentration, particle size of adsorbent and temperature on the adsorption capacity was investigated. The results showed that at the initial asphaltene concentration of 125 mg L 1-, contact time of 24 hrs, temperature of °50C and adsorbent dosage of 1 g, removal of asphaltenes onto LECA, perlite and bentonite was 53.59, 93.01 and %99.77, respectively. Also, Langmuir and Freundlich models were applied to describe the experimental data; moreover, the results indicated a good fitting by Langmuir isotherm. Thermodynamic parameters; such as, ∆H, ∆S and ∆G were calculated. It was revealed that the adsorption was spontaneous and exothermic nature, which was evident by decreasing the randomness of the dye at the solid and liquid interfaces. The characteristic results and the dimensionless separation factor (RL) showed that perlite and bentonite could be employed as an alternative to commercial adsorbents in the removal of asphaltenes from aqueous solution and oil.

A considerable quantity of the world’s oil reserve is located in naturally fractured carbonate reservoirs, with very low oil recovery efficiency, due to their wettability abd tightness of matrix. Recovery efficiency can be improved considerably, if the reservoir rock wettability is changed from mostly oil-wet to water-wet, thus enhancing water imbibition into the oil saturated rock. Smart water is able to alter the carbonate rock wetability from oil-wet to intermediate to water-wet, and therefor, water imbibition into the rock matrix is facilitated. In this study, the effect of ions and different surfactants concentration in the smart water on the wettability state of carbonate rocks was investigated by contact angle measurements and spontaneous imbibition experiments. Imbibition experiments were performed at three temperature level(50, 70 and 90 C). The effect of ions, temperature, and surfactant concentration on the wettability alteration of carbonate rocks during spontaneous imbibition process were invistegated. The results showed that the presence of SO42- ions, the strongly affects the wetting state of carbonate rocks, and increasing SO42- concentration from 0.033 mol/l to 0.1 mol/l increased the oil recovery from 19% to 58%. Moreover, by increasing Mg2 concentration the oil recovery increases (from 19% to 23%). Also the presense of cationic surfactant C12TAB, strongly changed the wetting state of carbonate rocks, and also increased the oil recovery from 19% to 78%.

Fractured carbonate reservoirs have low oil recovery efficiency due to wettability and tightness of rock matrix. One of the most applicable methods for enhanced oil recovery of carbonate reservoirs is to use smart water flooding. In addition using surfactants which have been obtained from Cedar leaf extract as a rich and cheap source leads enhanced oil recovery by improving the wettability properties. In this research, the effect of Ca2, Mg2 and SO42- concentrations in the smart water and also Cedar leaves extract concentration as a biosurfactant on wettability of carbonate rocks have been investigated. The analysis which is including contact angle measurments and cre flooding eperiments have been examined. Results showed the effect of Mg2 and Ca2 concentrations from 0.01 mol/L to 1 mol/L, SO42- concentration from 0.007 mol/L to 1 mol/L and biosurfactant concentration from 0.05 %(w/v) to 0.3 %(w/v) changes the carbonate wettability to water-wet, and oil recovery has increased from 35% to 57%. The contact angle has changed from 161 degrees to 41 degrees investigated in the 0.3 % (w/v) of biosurfactant concentration, which reflects the effect of the solution on the wettability of carbonate rocks.

The importance of filters in drinking water systems is increasing because it can remove considerable percentage of bacteria and diseases-causing microorganisms with minimal cost. In this context, the use of sand filters to removes water turbidity is common. The backwashing of sand filters remove deposits which are formed on the sand bed. Optimization of the backwash operation has a particular importance due to the volume of water used for backwashing sand filters (about 2-3% of the volume of filtered water). The measurement of wastewater turbidity in the operations can be an appropriate criterion for evaluating the effectiveness of Backwash operations. In this study, the Backwash operation of three sand filters are optimized by examination of the plots of turbidity versus time during the backwash of filter. In this study, backwash operation of three sand filter beds made of quartz sand particles has been studied. The results show that the optimized pattern of backwashing operation can be proposed by changing the air blowing time of backwash operation.

One of the recently developed methods of enhanced oil recovery in carbonate reservoir is smart water flooding. Smart water can alter the wetting state of carbonate rocks from oil-wet to water-wet and increase oil production. In this study, we have investigated the effect of smart water composition on the carbonate rock wettability at different aging temperatures and pH’s through measuring the contact angle. The response surface methodology was utilized for the design of experiments. The results show that Mg+2, SO4-2, and K+ ions have important roles in wettability alteration due to interaction with carboxylic acids adsorbed on the rock surface. Not only Mg+2 and SO4-2 ions but also, inactive ions such as K+ influenced the wetting state of carbonate rock. Furthermore, an increase in temperature could cause more water wetting state and more activity of ions in solution. In addition, increasing pH could decrease the contact angle because of reduction in positive surface charge of carbonate rock surface. However, when pH was close to 8, the contact angle was raised probably due to the precipitation of Mg+2 ion.

Naturally fractured carbonate reservoirs have very low oil recovery efficiency owing to their wettability and tightness of matrix. Recovery efficiency can be considerably improved by changing reservoir rock wettability from oil-wetting to water-wetting state. In this work، the effect of different ions، pH، and temperature on wettability of carbonate rocks was investigated by means of contact angle measurements. The results indicate that the Ca2+، Mg2+ and SO42- ions can change the wetting state of carbonate rocks toward water-wetting، both individually and when they are mixed. According to our measured contact angle data، simultaneous increase of the concentration of both Mg2+ and SO42- ions has positive impact on wettability alteration of the carbonate surface more than that of obtained by variation of individual ions. It is also found that addition of NaCl salt changes the wettability to more oil-wetting. We did، moreover، measure the impact of temperature on the wettability change of the carbonate surface. It is observed that higher temperatures result in water-wet surfaces، owing to facilitating fatty acid desorption. However، the impact of pH on wettability alteration is found to be complex، resulting in various wettability states by changing pH from 3 to 10.