Controlling or reducing the adsorption of surfactants on reservoir rock surfaces has been a challenging task in enhanced oil recovery (EOR) methods, as it directly affects the cost-effectiveness of the projects. The adsorption of surfactants on rock surfaces can modify their hydrophobicity, surface charge, and other important parameters that govern EOR processes, such as reducing the interfacial tension between water and oil and increasing permeability. Therefore, understanding the adsorption mechanism on rocks is essential for developing alternatives that improve the effectiveness of these processes. In this work, the adsorption of surfactants on carbonate materials was evaluated considering variations in temperature, contact time, and surfactant concentration. The surfactants used were derived from vegetable oils, aiming for a sustainable approach: saponified coconut oil (SCO), saponified babassu coconut oil (SBCO), and saponified castor oil (SMO). The finite bath method was used, resulting in adsorption efficiencies of 85.74%, 82.52%, and 45.30% for SCO, SBCO, and SMO, respectively. The Sips isotherm and the pseudo-second-order model were found to be suitable for characterizing these systems. The simulation of SCO adsorption isotherms on limestone by the Langmuir model was more accurate than that using the Freundlich model. The limestone showed a negative surface charge of approximately −35.0 mV at pH 6.5; this negative charge varied over a wide pH range. These zeta potential data for the samples confirmed that hydrophobic interactions played an important role in the adsorption of the surfactants. Thermodynamic evaluation indicated spontaneous and endothermic adsorption of SCO on limestone. The systems were also characterized by FTIR, TG/DTG, XRD, XRF, SEM, and zeta potential.

Formation damage caused by wellbore fluids remains a key concern in carbonate reservoirs, where pore plugging and filtrate invasion can severely reduce permeability. This study investigates the influence of filtrate-control components in cellulose-based polymeric fluids on the potential for formation damage in carbonate rocks and evaluates the performance of HPA starch as an alternative to cellulose, focusing on its comparative effects on formation permeability. Experimental tests were performed using Indiana Limestone cores to measure filtration behavior and permeability recovery after exposure to different polymeric solutions. The results revealed distinct mechanisms associated with each additive: PAC LV controlled fluid loss mainly by adsorption and pore plugging, while HPA starch formed more deformable and permeable structures. Glycerin, when used alone, did not induce formation damage but increased fluid viscosity, favoring more stable dispersion of the polymeric phase. Micronized calcite enhanced external cake consolidation through particle bridging. The combined use of PAC LV, glycerin, and calcite provided the most efficient filtration control and minimized formation damage. These findings contribute to understanding the isolated and synergistic roles of filtrate-control agents and support the design of optimized polymer-based fluids for well intervention and abandonment operations.

BaCeO₃-based ceramics are ionic and electronic conductors that can be applied to oxygen sensors, solid oxide fuel cells and oxygen permeable membranes. However, the low chemical stability at high temperatures of these materials motivates studies involving doping of A and/or B sites of the perovskite structure. In this context, the present work aimed to synthesize a new BaCe_0.8Pr_0.05Cu_0.15O_3-δ material using the chemical route of complexation which combines EDTA-Citrate with pH variation. The powders obtained at pH 3 or 11 and calcined up to 900 ºC are thermally unstable. The cubic perovskite BaCe_0.8Pr_0.05Cu_0.15O_3-δ with crystallite size between 99.4 nm and 131.6 nm was obtained along with barium carbonate traces. In the powders calcined at 1000 ºC the pH increase decreases the amount of barium carbonate (17.3% to pH 3, 3.4% to pH 7 and 1.8% to pH 11), but increases the size of grains with irregular shapes.