Formulação de fluidos de perfuração à base água a partir do rejeito de rochas ornamentais: Uma análise para aplicação na perfuração de rochas carbonáticas
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Data
2025-08-28
Autores
Moreira, Kelly Costa Cabral Salazar Ramos
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Universidade Federal do Espírito Santo
Resumo
Xanthan gum (GX), widely used in drilling fluids, undergoes polymer chain degradation and changes in its properties at high temperatures. Minerals such as bentonite are also common additives used to adjust fluid properties. However, their limitations in carbonate formations have driven the search for alternative mineral additives. Ornamental Rock Waste (RRO), a byproduct of granite and marble processing, is an available mineral whose disposal presents a significant challenge. In this context, this study proposes the use of RRO as a partial or total substitute for bentonite in aqueous fluids with GX, evaluating its influence on the polymer’s thermal stability. Two types of waste (RRO FD and FH) were characterized, with RRO FD selected for the formulations. The characterization of GX confirmed its structure, and thermogravimetric analysis revealed mass losses at 79 °C and 277 °C, associated with adsorbed water and volatiles, respectively. Kinetic evaluation (30–55% conversion) indicated an average activation energy of 177 kJ·mol⁻¹, typical of biopolymers. The z Master plot analysis suggested that degradation begins with rapid nucleation in the side chains, exposing the main chain to progressive thermal fragmentation. The pseudoplastic behavior of GX solutions was confirmed, and aging tests showed greater polymer degradation at temperatures above 140 °C (static) and above 100 °C (dynamic, 600 rpm). Thus, in dynamic aging, degradation was more severe due to the early loss of side chains. The addition of RRO to the polymeric fluid reduced viscosity, yield stress, and thixotropy, and also resulted in unstable suspensions. To improve this interaction, RRO was treated with terephthalic acid (TPA), stabilizing the particles in an alkaline medium. The reaction with ethylenediamine (EDA) and GX produced the RTPEX composite, confirmed by FTIR through the formation of amide bonds (C=O at 1653 cm⁻¹ and N-H at 1546 cm⁻¹). Fluids containing RTPEX showed improved rheological performance, especially at low shear rates. As the shear rate increased, the composite structure was broken, reducing its rheological properties. Flow curves adjusted using the Herschel-Bulkley and Power-Law models revealed shear-thinning behavior. The fluid with 100% bentonite (B 100%) exhibited the highest viscosity and yield stress (2.7412 Pa) due to its interaction with GX. The fluid combining RTPEX and bentonite at a 50:50% ratio (m/m) (RTPEX_B) showed comparable rheological performance to B 100%, indicating the formation of a stable three-dimensional network. Adjusting the pH to 10 improved the rheological parameters of the fluids containing RTPEX and bentonite, including the 100% RTPEX fluid, due to deprotonation of acidic groups. In thixotropy tests, RTPEX_B showed the largest hysteresis loop area (1431.6 Pa·s⁻¹), surpassing B 100% (1347.39 Pa·s⁻¹), reinforcing the synergy between components. After dynamic thermal aging, RTPEX_B maintained superior parameters, indicating greater resistance to degradation under shear. The results demonstrate the potential of RTPEX as a partial substitute for bentonite. To assess the economic viability of this reuse, a case study was conducted at an ornamental stone company in Espírito Santo, indicating the potential for significant reductions in operational costs for the ornamental stone industry
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Degradação térmica , Funcionalização , Reologia , Envelhecimento térmico , Compósitos , Engenharias , Thermal degradation , Functionalization , Rheology , Thermal aging , Composites , Engineering