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. When considering with greenhouse effect and global warming, carbon dioxide is the main agent. As the major contributors to the increase in global temperature, large companies and corporations have been encouraged to look for ways to reduce the emission of CO 2 into the atmosphere. In the geological aspect, two techniques have been applied in the use of CO 2 . The first is the carbon capture and storage, CCS, which refers to carbon dioxide injection into saline aquifers, reservoirs and coal deposits, helping to limit CO 2 emissions. The second is the enhanced oil recovery, or EOR, which refers to the injection of CO 2 in heavy oil reservoirs to decrease the viscosity and increase the recovery factor. Because CO 2 can interact with rock, changing its porosity or changing the direction of flow due to lower permeability zones, periodic monitoring of CO 2 must be performed. In this work, methods of dealing with the poor conditioning of the inverse problem were discussed, applying the methods of singular value decomposition and ray tracing. The Gassmann equation was used to simulate the velocity change within the reservoir due to fluid substitution. The above methods were incorporated into traveltime seismic tomography, which was applied to monitor the carbon dioxide injection in reservoirs. Several simulations in a synthetic model validated the proposed methodology. Keywords:  traveltime tomography, reservoir monitoring, geological storage, CO 2 injection. RESUMO. Quando tratamos do efeito estufa e aquecimento global temos como seu principal agente o dioxido de carbono. Por serem grandes contribuintes do aumento da temperatura do planeta, grandes empresas e corporacoes tem sido incentivadas a buscar formas de reduzir a emissao de CO 2 na atmosfera. No aspecto geologico, duas tecnicas tem sido aplicadas no aproveitamento do CO 2 . Aprimeira e o armazenamento geologico de CO 2 ou CCS, do ingles carbon capture and storage , que trata da injecao de dioxido de carbono em aquiferos salinos, reservatorios e camadas de carvao, ajudando a limitar a emissao de CO 2 . A segunda e a recuperacao avancada de petroleo ou EOR (do ingles enhanced oil recovery ), que se refere `a injecao de CO 2 em reservatorio de oleo pesado com o intuito de diminuir a viscosidade e aumentar seu fator de recuperacao. Devido ao fato do CO 2 poder interagir com a rocha, alterando sua porosidade ou mudando a direcao do fluxo devido a regioes de menor permeabilidade, e necessario realizar um monitoramento periodico do CO 2 . Neste trabalho foram abordadas formas de lidar com o mau condicionamento do problema inverso, onde aplicamos o metodo de decomposicao em valores singulares juntamente com o tracado de raios. Utilizou-se a equacao de Gassmann para simular a variacao da velocidade dentro do reservatorio devido a uma substituicao de fluidos. As tecnicas acima foram incorporadas a tomografia sismica de tempos de trânsito para o monitoramento da injecao do dioxido de carbono nos reservatorios. As diversas simulacoes num modelo sintetico validaram a metodologia proposta. Palavras-chave: tomografia de tempos de trânsito, monitoramento de reservatorios, armazenamento geologico, injecao de CO 2 .

ACOUSTIC TRAVELTIME TOMOGRAPHY FOR CO2 INJECTION MONITORING IN RESERVOIRS