Avaliação da integridade da pasta de cimento classe G com a rocha arenito da Bacia do Paraná em condições de armazenamento geológico de CO2

• Autor(a) principal: Ortiz, Rafael Goularte
• Data de Publicação: 2017
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da PUC_RS
• Texto Completo: http://tede2.pucrs.br/tede2/handle/tede/7907
• topic: CO2 Úmido; Degradação do Cimento; Interface Pasta de Cimento/rocha; Armazenamento Gelógico de Carbono; Carbonatação em Ceio Ácido; ENGENHARIAS

Carbon geological storage in depleted wells has been identified as an important solution to mitigate the environmental impacts caused by the release of CO2 into the atmosphere. However, the degradation of the materials used in the construction of the wells over the years has been one of the major concerns of the application of this technology, due the possibility of CO2 escape to the surface. The most susceptible region of CO2 leakage is through the wellbore at the interface between the cement paste and rock formation. The degradation of the cement paste occurs due to the presence of CO2 and water or brine, occurring acid carbonation that causes loss on mechanical resistance and increase in porosity. This work aims to study the chemical alteration of the class G cement paste in the presence of arenite rock of the Rio Bonito Formation (Paraná Basin-Brazil) by humid CO2, CO2 saturated water and brine saturated with CO2, simulating the geological storage conditions with a depth of 1,500 m, corresponding to a temperature of 70°C and the pressure of 15MPa. For the degradation test, samples were made by pouring a cement into the hole of an arenite cylinder. The tests were performed in two exposure times, 28 and 180 days, and the chemical degradation of the cement phases was evaluated by Scanning Electron Microscopy (SEM / FEG) and X-Ray Diffraction. The density of cement and rock before and after exposure to CO2 was obtained by pycnometry and the surface area of the rock pores and the diameter of them were evaluated by the BJH method. In addition, the percentage of inorganic carbon present in the rock was determined before and after the degradation tests. The carbonation of the cement was less accelerated in the samples exposed to the saline solution than in the supercritical environment of CO2 and CO2 saturated water, probably due to the decreasing of CO2 solubility in the aqueous medium in the presence of salts and also due to the higher precipitation of carbonate in the pores of the rock that make difficult the CO2 percolation. The density measurements showed that there was an increase in the density of rock and cement (near the interface with the rock) after exposure to CO2 and the density increased with the time of exposure. The surface area of the rock pores, for both times and all mediums, increased after expusure to CO2 due the precipitation of CaCO3, while the radius of the pore have a tendence to decrease. In addition, an increase in the amount of carbon present in the rock after CO2 exposure was observed for the three studied environment and the two exposure times, and a higher amount of carbon was observed for the rock samples exposed to the saline solution, and in this case the carbon content significantly increased from exposure time from 28 days to 180 days.