Iranian Journal of Oil and Gas Science and Technology

Abstract Recently, nanoparticles have been used to improve oil and gas production volume and enhance oil recovery (EOR). Based on our recent research, using nanoparticles such as silica and calcium oxide has a good potential for changing mechanisms in the porous media, such as interfacial tension and wettability. Low permeability carbonate plugs were selected to determine the application of nanoparticles in the porous media. Two main steps were used: 1) Using CaO and SiO₂ nanoparticles for wettability alteration, interfacial tension reduction, and improving fluid flow through porous media, and 2) Surveying the application of nanoparticles to the water alternating gas (WAG) (nanoparticles (NCs)-assisted WAG) test. The zeta potential values were stable at –56.4 ± 2 mV and –44.0 ± 3 mV for calcium oxide and silica nanoparticles, respectively, at an optimum nanoparticle concentration of 15 ppm. Calcium oxide and silica nanoparticles effectively altered the wettability from oil-wet to water-wet by surveying the intersection of two-phase relative permeability. Moreover, CaO nanoparticles performed better in low permeability carbonate porous media than SiO₂ nanoparticles regarding wettability alteration to water wetness. Based on the results and a better grade of CaO, it was selected for performing NCs-assisted WAG tests at WAG ratios of 1:1, 40 ℃, and 15 ppm. The recovery factor increased from 42.9% to 73% in the presence of CaO during NC-assisted WAG tests, and residual oil saturation decreased from 40.9% to 19.4%.

Abstract Rock-Eval pyrolysis is a thermal method petroleum geologists use to evaluate source rock characteristics and obtain geochemistry parameters. However, there are misconceptions and misuses in exceptional cases that could lead to erroneous conclusions after using the Rock-Eval pyrolysis data to evaluate the properties of organic matter. However, a cross-plot of petroleum potential (S₂) versus total organic carbon (TOC) is a useful tool for solving issues and checking the accuracy of the geochemistry parameters. The graph provides the correction criteria for the S₂, hydrogen index (HI), and kerogen types. As well as the graph measures the adsorption of hydrocarbon by the mineral matrix. In addition, this article demonstrates a manner based on the data plot of S₂ versus TOC to detect bitumen or hydrocarbon contaminations. Based on our knowledge about the Garau formation as a possible source rock in the petroleum geology of Iran, a geochemistry study by Rock-Eval VI pyrolysis and LECO carbon analyzer has been conducted on many rock samples collected from different outcrops in the Lurestan province, Aligudarz region, from southwest of Iran, High Zagros. Plotting the data on a cross plot of S₂ versus TOC, drawing the regression line, and finding the regression equation are the best methods for determining the actual values of S₂ and HI parameters and bitumen/hydrocarbon contamination. Contamination creates a y-intercept in the graph of S₂ versus TOC, making geochemistry data unreliable in two study locations. The S₂ and HI data unrealistically increase, while the T_max values decline and reduce the thermal maturity of the organic matter from its actual status. The y-intercept of the graphs is removed, and the corresponding values are subtracted from the HI and S₂ to skip the effect of contamination and obtain the actual geochemistry parameters. The cause of contamination in the Garau formation is the adhesion of heavy bitumen to organic facies due to the covalent bonds between carbon and hydrogen ions.

Abstract Knowing the characteristics of suitable environments for the precipitation of oil-prone source rocks facilitates oil explorations and leads to the development of oil fields. The current study investigates the properties of organic matter and sedimentary environment conditions of the Garau formation in various outcrop sections in Lurestan province from southwest of Iran (High Zagros) using elemental analysis, visual kerogen analysis, and Rock–Eval pyrolysis data. The geochemistry parameters indicate that the Garau formation is an excellent oil-prone source rock composed of kerogen types I and II. The oxygen index (OI) is minimal, revealing that organic matter is deposited in an anoxic sedimentary environment, suitable for preserving organic matter and hydrocarbon generation. The visual analysis of isolated kerogens from source rock samples indicates the abundance of dark amorphous organic matter (AOM) with low amounts of phytoclasts and pyrite without any palynomorph. Sedimentation appears to have occurred in deep and reduced parts of a carbonate basin during a rapid transgression. In addition, due to the effect of thermal maturation, the color of amorphous organic matter has darkened. The elemental analysis and van Krevelen diagram are employed to show the type of organic matter and reveal that the thermal maturity is related to the oil window. Elemental analysis reveals the high content of organic sulfur in the structure of kerogen. Moreover, the content of pyritic sulfur (Sp) and organic sulfur (So) is calculated.

Abstract Using nanoparticles for adsorbing asphaltene is an efficient method for upgrading actual oil samples compared to other expensive mechanical treatments or even solvents, such as n-pentane and n-heptane, and surfactants. This study uses nickel–zeolite oxide nanoparticles for asphaltene adsorption and solving asphaltene precipitation problems. Although nickel–zeolite oxide nanoparticles have been used in previous studies as an asphaltene adsorbent, observing the relationship between asphaltene adsorption on their surface and asphaltene precipitation in the presence of nanoparticles during the actual process is not covered. For addressing this relation, we performed a series of experiments included Fourier-transform infrared spectroscopy (FTIR), CO₂–oil interfacial tension tests, Langmuir and Freundlich isotherm models, and natural depletion tests in the presence of nickel–zeolite oxide nanoparticles. The Langmuir model better fitted the adsorption data than the Freundlich model, which shows that the adsorption occurs on a homogeneous surface with monolayer coverage. Based on the CO₂–oil interfacial tension results, there are two different slope forms in interfacial tension readings as pressure increases from 150 to 1650 psi. Due to asphaltene aggregation, the second slope (900–1650 psi) is slower than the first one (150–900 psi). Three pressures of 1350, 1500, and 1650 psi and nickel–zeolite oxide nanoparticles at a concentration of 30 ppm were selected for the natural depletion tests, and the basis of selection was high-efficiency adsorption at these points. As pressure decreased from 1650 to 1350 psi, asphaltene precipitation changed from 8.25 to 10.52 wt % in the base case, and it varied from 5.17 to 7.54 wt % in the presence of nickel–zeolite oxide at a concentration of 30 ppm. Accordingly, nickel–zeolite oxide nanoparticles adsorbed asphaltene on their surface correctly, and the amount of asphaltene precipitation decreased in the presence of nickel–zeolite oxide nanoparticles.

Abstract One of the critical issues in the oil industry is related to asphaltene precipitation during different stages, and using nanoparticles is known as a standard method for solving this problem. Although nickel oxide and zeolite have been addressed in previous research to solve the asphaltene precipitation problem, using NiO/Na-ZSm-5 (the primary goal of this study) has not been developed to solve relevant asphaltene precipitation problems. The crystalline structure and morphology of the synthesized nanoparticles were analyzed with the help of X-ray diffraction spectrometry (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and energy-dispersive X-ray spectroscopy (EDXS). The results show that the nanoparticles were well synthesized and preserved their crystalline structure with a diameter of 13.6 nm after synthesis. The EDXS analyses also proved that the sorbent adsorbed an amount of asphaltene. In the next step, asphaltene adsorption experiments were carried out at various concentrations of asphaltene and temperatures, and the effect of different variables, including the initial concentration of asphaltene, temperature, and the ratio of heptane to toluene, on the asphaltene adsorption rate was evaluated. The results indicate that with an increase in the initial asphaltene concentration from 25 to 2000 ppm, the asphaltene adsorption rate in zeolite increases. At concentrations less than 500 ppm, a rise in the temperature reduces the asphaltene adsorption, while at concentrations higher than 500 ppm, raising the temperature from 25 to 55 °C increases asphaltene adsorption capacity on zeolite. Further, more significant adsorption is observed at a heptane-to-toluene ratio of 0.4 with q = 25.17 mg/g. Evaluating the effects of kinetic adsorption molecules of asphaltene on these nanoparticles shows that the adsorption process reaches equilibrium in less than 2 h. The experimental data were adapted according to Lagrangian pseudo-first-order and pseudo-second-order models to determine the kinetic mechanism of this process. The Langmuir and Freundlich adsorption isotherms were evaluated, and the isotherms resulting from the Langmuir isotherm model were of good conformity, indicating that adsorption at the homogenous level occurred with a single-layered coating. In the final step, after evaluating the thermodynamic conditions, the spontaneity of the asphaltene adsorption process was proved.