Deep ocean storage of CO2 could help reduce the atmospheric level of greenhouse gas as part of a climate change mitigation strategy. In this paper, a multiphase flow model of CO2 sequestration into deep ocean sediments was designed associated with the formation of CO2 hydrates. A simplified assumption was proposed to predict the critical time of CO2 leakage from marine sedimentary strata into seawater. Moreover, some principal parameters, which include the permeability, anisotropy, total injection amount, and length of the injection part of wellbores, were investigated by numerical simulations. The numerical estimates are used to assess the feasibility and effectiveness of CO2 storage in deep ocean sediments. Accurately predicting the actual fate of liquid CO2 sequestered into the marine sedimentary strata at depths greater than 500 m is complicated by uncertainties associated with not only the chemical-physical behavior of CO2 under such conditions but also the geo-environment of disposal sites. Modeling results have shown some implications that the effectiveness of CO2 ocean sequestration depends mainly on the injection conditions (such as injection rate, total injection amount, and the depth of injection), the site geology (such as permeability and anisotropy of disposal formations), and the chemical-physical behavior of CO2 in marine environment. (c) 2008 Elsevier Ltd. All rights reserved.