Banca de QUALIFICAÇÃO: FÁBIO PEREIRA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : FÁBIO PEREIRA
DATE: 10/10/2024
TIME: 10:00
LOCAL: Auditório do Lacbim - Núcleo Tecnológico de Cimentação de Poços de Petróleo (NTCPP)
TITLE:

ANTI-RETROGRESSION EFFECT OF ALTERNATIVE SILICAS COMPARED TO CRYSTALLINE SILICA IN HIGH TEMPERATURE AND HIGH-PRESSURE OILWELL CEMENTING

KEY WORDS:

Microstructure. Semi-crystalline phases. Alternative silicas. High temperature. Xonotlite. Tobermorite.

PAGES: 22
BIG AREA: Engenharias
AREA: Engenharia Civil
SUBÁREA: Construção Civil
SPECIALTY: Materiais e Componentes de Construção
SUMMARY:

Oil well cementing in high-temperature scenarios is critical for constructing wells under high temperature and pressure gradients. In high-temperature environments, challenges increase significantly, as the cement must withstand elevated temperatures without compromising its stability and mechanical properties. Temperatures above 110°C trigger chemical changes in the cement hydration products, converting semicrystalline Calcium Silicate Hydrate (C-S-H) into crystalline phases (conversion of hydrated calcium silicate into lime-rich phases), such as Alpha-Dicalcium Silicate Hydrate (α-C2SH). Quartz-based (SiO2) materials are generally added to the cementitious pastes to mitigate strength regression at high temperatures. The main contribution of these materials to cementitious systems exposed to high-temperature conditions is the formation of semicrystalline calcium silicate hydrate-rich phases, mainly Xonotlite in systems where only crystalline silica (SiO2 with a minimum purity of 97%) is added, and Tobermorite in systems where mineral sources are primarily used, which, in addition to SiO2, contain aluminum. These two crystalline phases are responsible for combating strength regression. This study aimed to evaluate the contribution of different substitution percentages in the combined use of two silica-rich (SiO2) residues derived from industrial mortar production and thermal treatment of biomass in cement pastes. Specimens were molded according to international standards and cured directly in a curing chamber at a temperature of 180°C for 7, 14, and 28 days. After these curing periods, the specimens were subjected to uniaxial compressive strength tests to evaluate their mechanical strength. Samples were collected for microstructural analyses, including X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), in addition to qualitative analyses by energy-dispersive spectroscopy (EDS). The results showed that the reference paste with 35% crystalline silica substitution predominantly formed the Xonotlite phase at all three curing ages. On the other hand, the ternary pastes, with 50% combined substitution of residues from industrial mortar production and biomass thermal treatment, predominantly formed the Tobermorite phase at all three curing ages. These findings can provide a solid foundation for optimizing formulations used in wells.

COMMITTEE MEMBERS:
Presidente - 2621720 - ANA CECILIA VIEIRA DA NOBREGA
Externo ao Programa - ***.236.044-** - BRUNO LEONARDO DE SENA COSTA - UFRN
Externo ao Programa - ***.031.714-** - GLAUCO SOARES BRAGA - IFRN