Um estudo multidisciplinar sobre o monitoramento, a medição e a verificação do dióxido de carbono (MMV de CO2) aplicado aos resultados do projeto piloto brasileiro de CO2

Abstract

This dissertation presents and assesses the experimental results gathered throughout the deployment and testing of two sets of atmospheric detection techniques for the Monitoring, Measurement and Verification of carbon dioxide (CO2 MMV), carried out on a field lab sponsored by PETROBRAS, at the Ressacada Farm, owned by the Federal University of Santa Catarina, UFSC. A short campaign was carried out in September 2013, in which discrete, very small volumes of commercial, food-grade gaseous CO2 were injected into the ground at shallow levels, through a 3-m depth vertical well, and then let release in the atmosphere, thus enabling the simulation of a leak event. The field campaign was run continuously over 12 days, at a maximum CO2 mass injection rate of ca 150g. h-1. While the gas was injected, pressure and mass flow were also continuously monitored. The specific objectives of this thesis are: (1) to present and assess the results of the CO2 atmospheric measurements, which were carried out by means of (a) an Eddy Covariance and a meteorological tower, for the measurement of turbulent atmospheric fluxes and atmospheric concentration monitoring; (b) CO2 atmospheric concentration measurements resorting to direct absorption spectroscopy using a broadband light source spectral band in parallel with the monitoring of the isotopic ratio 13C/12C; (2) to present and assess the results of the dispersion modeling of the CO2 seepage plume, using the atmospheric model AERMOD 8.8.9. The simultaneous use of both methodologies allowed the measurement of a subtle increase in the local CO2 atmospheric levels, likely to be closely associated with the seepage experiment: average concentration ranging from 410 to 450 ppmV, atmospheric fluxes from -30 to + 20 µmols.s-1.m-2 and isotopic ratio within the vicinities of -17 ppmil. These figures are consistent with the modest magnitude of the leakage experiment. The modeling studies also portrayed consistent trends: a negligible increase in the maximum ground-level atmospheric concentrations (less than 20 ppmV, within the experimental cell boundaries for the base case). For the hypothetical scenarios, no potential risks to human health were forecasted, even for the 100 X the release rate case, while confronting the model outputs to the benchmarks retrieved from the occupational health standards, the maximum estimated concentrations were substantially lower than the limits currently in practice. The direct benefits of this thesis are: (1) the unique nature of the field study, that brought forth on field CO2 seepage levels compatible with and similar to local background concentration levels and effluxes; (2) the pioneer and innovative initiative of the study : this is the First National Laboratory built and installed in Brazil, as well as in Latin America, specially designed to test CO2 MMV technologies; (3) the multidisciplinary nature of the study, both in terms of experimentation techniques deployed on field, as well as in the comprehensive, consolidated analysis of the results achieved