Fariborz Rashidi

In this study, surface modification of a general purpose activated carbon is achieved through impregnation of three common amino acids namely, glycine, serine and lysine for CO₂ adsorption in post-combustion processes at temperature range 298–358 K. Glycine, due to its smaller molecular size, higher nitrogen content, and enhanced pore accessibility caused the adsorption to increase by 25% compared to original activated carbon uptake. N₂ adsorption isotherms were measured to comparatively evaluate adsorption preference and infer potential CO₂/N₂ selectivity. The modified adsorbents with glycine exhibited similar N₂ uptake to initial activated carbon at 358 K. All adsorbents exhibited physisorption behavior, with isosteric heat of adsorption values ranging from − 11 to − 33.9 kJ/mol for CO₂ and − 15.6 to − 17.8 kJ/mol for N₂. Overall, the results demonstrate that functionalizing by glycine, significantly enhances CO₂ adsorption capacity of activated carbon. These findings provide valuable insights for designing tailored adsorbents for post combustion CO₂ capture.

Understanding how mineral heterogeneity and brine salinity influence the electrical double layer (EDL) structure is crucial for optimizing low-salinity water injection strategies in carbonate reservoirs. In this study, molecular dynamics (MD) simulations were conducted to elucidate the mechanisms governing EDL behavior at the interface of a novel composite carbonate surface (87% calcite, 13% quartz) in contact with diluted water (DW), seawater (SW), and high-salinity formation water (FW) in presence of complex model oil including wide variety of nonpolar oil hydrocarbon. Results indicated that increasing brine salinity compressed the Stern layer significantly, strengthening electrostatic interactions at the mineral surface and promoting oil adhesion due to enhanced ion bridging by divalent cations (Ca²⁺, Mg²⁺). This process resulted in a pronounced shift toward hydrophobic (oil-wet) surface characteristics under FW conditions, compared to SW and DW. Additionally, the observed differences in water–surface interactions between calcite and quartz were explained mechanistically: the highly charged calcite surface enabled strong inner-sphere coordination of water molecules at 2.37 Å, whereas the neutral quartz surface supported only weaker outer-sphere hydration at 3.1 Å. Ion mobility analysis further revealed enhanced dynamics of Na⁺ ions in SW system, facilitating disruption of oil–surface ionic bridges, while FW promoted ion clustering and reduced ionic mobility, stabilizing oil attachment. These insights emphasize the critical role of mineral surface chemistry and salinity-dependent electrostatic interactions in governing wettability and oil recovery efficiency during low-salinity waterflooding.

In low-salinity water flooding (LSWF), modifying the injected brine composition leads to greater oil recovery from carbonate reservoirs. The processes that control improved recovery during LSWF are not totally clear, which could lead to ambiguities in finding optimum brine composition regarding wettability alteration (WA) toward water wetness. One of the methods to determine WA is bound product sum (BPS) calculation using geochemical tools. In the case of wettability improvement, the BPS value of a crude oil-brine-rock (COBR) system should be at its minimum value. In this study, an improved geochemical model is developed, which includes the effects of oil composition (i.e., acid number, base number, and weight percent of nonhydrocarbon components) and physical properties of oil (i.e., density, viscosity, and solution gas-oil ratio) on COBR interactions. The proposed method generates BPS as a function of temperature, pressure, oil and brine composition, and pH for carbonate rocks. The model applicability was validated using several experimental data sets available in the literature. The results of the improved BPS model were in line with the results of contact angle and zeta potential measurements as the major indices of rock wettability. BPS calculations using the available geochemical tools sometimes failed to predict the correct WA trend since they overlooked the impact of oil properties on COBR interactions. The model predictability was also compared with the results of an available geochemical tool, PHREEQC, and the results demonstrate just how important the effect of oil properties and composition inclusion on wettability determination is. The improved BPS approach could be successfully utilized as an optimization tool to optimize the water composition during LSWF for a given COBR system.

Experimental measurements of zeta potential could be employed for the disjoining pressure calculation to determine wettability alteration during low salinity water injection. However, due to the instability of zeta potential measurements at high temperatures (∼>80ͦc) which are representative of hydrocarbon reservoir temperature, this approach has been rarely recommended for hydrocarbon reservoirs. To avoid the zeta potential measurement, a theoretical approach is presented in this study. A numerical model is developed which considers the involved equilibrations, including chemical and thermodynamic equilibriums. The model presents an in-house MATLAB platform that includes interface charge alteration which affects surfaces zeta potential for a given Crude Oil-Brine-Rock system (i.e., oil-brine and rock-brine interfaces). The proposed model conducts phase equilibrium calculation. It considers the effect of soluble components of each phase on the composition and thickness of the electrical double layer that determines the stability of the water film between oil and rock surfaces. Consequently, the zeta potential is related to pressure, temperature, oil and brine composition, and pH for the carbonate rocks. The model is validated using the data sets from the literature. Results show that the developed model correctly represents zeta potential trends arising from changes in brine composition.

Adsorption of oil molecules, especially surface active components, to the calcite surface plays a vital role in the wettability state and oil recovery from carbonate reservoirs. Through the simulation of classical molecular dynamics, we demonstrate the formation of adsorption sites on calcite surfaces of non-polar (decane and toluene) and polar (benzoic acid) oil molecules and the act of water molecules on detachment from the surface of adsorbed molecules. Two systems, oil-calcite and water-oil-calcite, are investigated, and the simulations are conducted at low (300 degrees K) and high temperatures (393.15 (K) over circle). The studied properties are number density, distribution of the center of mass, and radial distribution function. The results show that the minimum distance between the oxygen of calcite and oxygen of ben-zoic acid, hydrogen of decane, and toluene are 1.437, 2.437, and 2.562 angstrom, respectively. It is concluded that benzoic acid is adsorbed stronger to the calcite surface than decane and toluene at both temperatures. In the presence of water, non-polar molecules are desorbed from the surface at T = 393.15 (K) over circle, and water molecules are strongly adsorbed to the calcite surface compared to the non-polar molecules. Furthermore, it is revealed that water molecules do not desorb polar molecules from the calcite surface, even at elevated temperatures. Radial distribution function analysis indicates that the strong attachment of the polar molecule to the calcite surface is more significant than the water molecule, which implies the role of oil's polar components in changing the wettability of pore wall to oil-wet. The results of this work are applicable in further studies on using enhanced oil recovery methods to detach polar oil components from the carbonated reservoirs.

In this study, by employing a novel analytical model for well test analysis, characterization is performed for a fractured-vuggy reservoir containing volatile oil with flowing wellbore pressure below the bubble-point pressure. Well test analysis in such medium is challenging due to complications in reservoir geology and fluid behavior. Rock complications arise because of existence of three media which interact with one another due to different flow behavior. Fluid related challenges are caused by gas liberation and two phase flow near the well bore. To perform the analysis, a synthetic model was investigated and pressure data were generated. Pressure data in such reservoir exhibited a radial composite behavior. Subsequently, a triple porosity radial composite model was developed for analysis and parameter estimations in such reservoirs. It is shown that reservoir parameters could be predicted with acceptable accuracy using the proposed model. The estimated effective permeabilities in all cases were close to the actual value, with absolute relative error less than 0.1. However the obtained interporosity flow parameters were slightly different from single phase parameters due to the presence of gas bank near the wellbore.