Um estudo preliminar sobre o envelhecimento de fluidos de perfuração de poços de petróleo

Abstract

Drilling fluids play an essential role in the petroleum industry, being responsible for pressure control, wellbore stability, and cuttings transport. During operations, these fluids may remain stagnant under elevated thermal conditions, which can alter their properties and compromise their performance. In this context, the present study aimed to evaluate the effect of accelerated aging on solids sedimentation and the rheological behavior of water-based drilling fluids, as well as to investigate the influence of thermal aging on the behavior of xanthan gum in isolation. For this purpose, fluids supplied by Petrobras (BRCARB10) were used and subjected to aging at 65 °C for 0, 16, 32, and 48 hours. Sedimentation was monitored using the Gamma-Ray Attenuation Technique (TARG), while physicochemical parameters were subjected to one-way ANOVA statistical analysis (α = 0.05). Concurrently, xanthan gum solutions at concentrations of 0.2% and 0.4% (w/w) were aged at different temperatures for isolated polymer analysis. The results showed that the density of fluid BRCARB10 exhibited a statistically significant variation during aging (p = 0.00833), with a reduction between 0h and 32h and a subsequent increase between 32h and 48h, although initial and final values did not differ statistically. Solids concentration, filtrate volume, and salt content parameters remained stable, evidencing the compositional robustness of the system. Rheological analyses indicated an increase in the consistency index and a decrease in the flow behavior index after 48 hours for the drilling fluid, suggesting structural rearrangements that favor solids suspension, confirmed by the absence of significant sedimentation for up to 150 days. Sedimentation tests revealed high gravitational stability, with no concentration gradients forming along the column over long periods. The xanthan gum study evidenced progressive thermal degradation, especially at higher temperatures, characterized by a reduction in the consistency index, an increase in the flow behavior index, and a decrease in the system's restructuring capacity. Thus, this work contributed to observing that moderate thermal aging primarily affects the rheological behavior of the fluids without compromising their sedimentation stability, highlighting the importance of component interactions in maintaining operational performance.