Banca de QUALIFICAÇÃO: RAPHAEL RIBEIRO DA SILVA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : RAPHAEL RIBEIRO DA SILVA
DATE: 12/12/2025
TIME: 09:00
LOCAL: LABCIM
TITLE:

Brazilian Rock-Based One-Part Geopolymers: Development, Optimization, and Application to Oilwell Cementing

KEY WORDS:

Geopolymers; JAW systems; Hydrothermal activation; Aluminosilicate precursor; Sustainable cementitious materials

PAGES: 30
BIG AREA: Engenharias
AREA: Engenharia Química
SUMMARY:

The increasing global demand for safe, sustainable cementing operations in the oil & gas industry has intensified the search for alternative cementitious materials that can outperform or complement Ordinary Portland Cement (OPC) under harsh downhole conditions. As thousands of wells approach the end of their productive life, the industry faces challenges related to long-term zonal isolation, chemical durability, and temperature–pressure resilience. In this context, geopolymers have emerged as promising candidates due to their low-carbon footprint, superior thermal stability, and chemical resistance. This work explores the development of one-part rock-based geopolymers derived from a Brazilian aluminosilicate precursor, aiming to provide a technically robust, environmentally favorable solution for Oil & Gas cementing applications. In the first phase, the precursor was blended with ground granulated blast furnace slag (GGBFS) and microsilica and activated using potassium silicate to evaluate its performance as a well-cementing system. Fresh-state properties—rheology, consistency, and thickening time—were systematically evaluated. At the same time, hardened-state behavior was assessed through compressive strength testing at multiple curing ages and temperatures relevant to downhole conditions. The geopolymer exhibited pronounced temperature- and pressure-sensitive behavior, underscoring the importance of optimized formulations for P&A scenarios. The second phase focused on precursor activation through a hydrothermal process to enhance reactivity and mechanical performance. A structured Design of Experiments (DoE) methodology was adopted, employing a Box–Behnken Design (BBD) to examine the roles of water-to-solid ratio (0.4–1.0), NaOH content (12–36 g per 100 g precursor), activation temperature (150–200 °C), and activation time (4–8 h). Thirty-one experimental runs, including replicated center points, enabled robust estimation of the main effects, interactions, and curvature. Comprehensive characterization (XRD, XRF, PSD, FTIR, NMR, and SEM) revealed significant mineralogical transformations, including the formation of analcime, indicating enhanced structural reorganization under hydrothermal conditions. To further optimize performance, a Central Composite Design (CCD) was implemented to assess how precursor composition and water-to-solid ratio influenced compressive strength at 70 °C. The resulting formulations achieved compressive strengths of up to 50 MPa under laboratory curing, demonstrating their suitability for oil well cementing applications. Microstructural observations by SEM and EDS confirmed the development of amorphous geopolymeric gels and suggested the incorporation of Si and Al into a cohesive three-dimensional matrix. Collectively, these results confirm that hydrothermal pre-activation is an effective strategy to improve the reactivity and engineering performance of the Brazilian rock-based precursor. Overall, this research advances understanding and practical development of sustainable one-part geopolymers for Oil & Gas well cementing, offering a viable pathway to improve long-term integrity in P&A operations while reducing environmental impact and enhancing operational reliability.

COMMITTEE MEMBERS:
Presidente - 1979301 - RENATA MARTINS BRAGA
Externa ao Programa - 2621720 - ANA CECILIA VIEIRA DA NOBREGA - UFRNExterno ao Programa - 1913849 - EDGAR PERIN MORAES - UFRNExterno ao Programa - 1804366 - JÚLIO CÉZAR DE OLIVEIRA FREITAS - UFRN