Effect of hydrophobic modification of scleroglucan on its adsorption behavior onto carbonate rock surface of oil reservoir

In this study, the effect of chemical modification on adsorption behavior of scleroglucan polymer on carbonate rock of oil reservoir was studied. The chemical modification was performed to increase hydrophobicity of scleroglucan while substituting ionic and hydrophobic groups on its structure simultaneously. Investigation of adsorption behavior of the samples on carbonate rock surfaces revealed an increase in uptake of the modified samples compared to the original one. Evaluation of various factors affecting the adsorption process showed that the Langmuir isotherm can describe the adsorption behavior of primary and hydrophobic scleroglucan samples better that Freundlich & Temkin isotherms. However, the adsorption behavior of the ionic-hydrophobic sample was hard to explain using the Langmuir model. A pseudo-second-order & Intra-particle diffusion models could express uptake kinetics of the samples. Thermodynamic studies indicated the temperature-dependency of free energy, ΔG, and the dominant role of entropic phenomena, rather than enthalpic phenomena, in the adsorption process of samples. In addition, ΔH values of different samples (about 6 KJ/mol for the primary scleroglucan, 5 KJ/mol for the hydrophobic scleroglucan and 9 KJ/mol for the ionic-hydrophobic scleroglucan) suggested the physical adsorption of samples onto the carbonate particles surface in both water and brine solutions.