Adsorption of Nonionic Surfactants (Nonylphenols) on Sandstone Rock via Alcoholic Micellar Solution

The adsorption of surfactants on rock surfaces can modify their hydrophobicity, surface charge, and other important properties that govern advanced oil recovery processes, such as decreasing the interfacial tension between water and oil and increasing permeability. Generally, the need to control and/or reduce surfactant adsorption on reservoir rock surfaces has been a challenging task in enhanced oil recovery (EOR) methods, as it directly impacts the project's economics. This requires a comprehensive study and understanding of the adsorption mechanism on rocks. This work investigates the adsorption process of nonionic surfactants from the family of ethoxylated nonylphenols in alcoholic micellar solutions on sandstone rock surfaces. The systems used in the experiments consisted of NP 9.5EO, NP 11EO, and NP 15EO, butanol as an amphiphilic solvent, and a saline solution (2% KCl) as the aqueous phase. The experiments were conducted according to the Scheffé network and showed an adsorption efficiency of 66.89% for NP-15EO, 67.15% for NP-11EO, and 70.60% for NP-9.5EO, thus proving that the higher the degree of ethoxylation of nonylphenols, the lower the adsorption capacity. Point F was chosen as the optimum point since this point remained constant during the experiments, besides being a water-rich region with low butanol content. The sandstone exhibited oil-favorable wettability, which after treatment resulted in wettability inversion, with a decrease in the contact angle with water, a factor that can increase oil recovery. Adsorption isotherm modeling was also performed to investigate the adsorption mechanism. All adsorption tests followed and best fit the Redlich-Peterson isotherm, showing that the adsorption process occurs in monolayers and multilayers. The experimental methodology also involves analyses of mineralogy, morphology, thermal stability, and surface charge of the sandstone rock.