Cementing plays a fundamental role in the construction of oil wells, as it is directly linked to their integrity and durability. A slury used for this purpose is typically composed of water, cement, and additives. Additives are essential materials for adjusting the physical and chemical properties of the slury, making it suitable for the peculiar temperature and pressure conditions found in wells. Additives can be synthesized from inorganic and natural compounds, one of which is lignin, a polymer present in lignocellulosic biomass. It has low commercial value however, when subjected to structural modification processes, it can acquire exceptional characteristics that make it highly valuable and suitable for various industrial applications. Thus, this research aimed to develop a bioadditive from green coconut lignin, via oxidative modification, for application in oil well cementing slurries. Lignin was extracted through alkaline pretreatment of green coconut biomass, and its structural modification was carried out through the oxidation process using hydrogen peroxide. After the synthesis process, unmodified lignin (LNM) and oxidized lignin (LOX) were characterized using Zeta potential, Fourier-transform infrared spectroscopy, UV spectrophotometry, and thermogravimetric analysis (TGA/DTG). The lignins were validated as retarder additives by the thickening time test, and the dispersant capacity was evaluated through rheology testing. The developed additive was compared to a commercial additive through a primary cementing simulation, where rheology tests, static filtration, and thickening time were evaluated. In characterization, the opening of aromatic rings and the increase in surface charge were confirmed in LOX. LOX provided greater retardation of setting time than LNM. A dosage of 0.5% of LOX resulted in a setting time of over 2 hours (50% more than the reference paste), validating it as a retarder additive. Additionally, LOX showed dispersant effect as a secondary property and contributed to reducing the rheological parameters of cement slurries. Technological application showed that LOX can modify the properties of cement slurries in a manner compatible with a commercial retarder additive. Its application together with other additives resulted in a slight increase in the rheological parameters of the slurries and contributed to reducing filtrate. Regarding thickening time, with just 0.1% of LOX, it was possible to delay the setting time by 71 minutes (31%) more than the reference paste. These results suggest that LOX is a promising alternative retarder additive that, in addition to benefiting the oil and gas industry, contributes to adding value to green coconut waste.

 

Keywords: Lignocellulosic biomass; lignin; natural additives; cementing; oil wells.