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.
