Abstract
The migration of CO2 is stochastic in heterogeneous porous media. This paper considers the CO2 diffusion with the case of steady flow in heterogeneous porous media. The partial differential equations of CO2 diffusion in random velocity field are established based on the mass conservation equations of CO2- brine two-phase flow with the change of time scale and spatial scale under the influence of heterogeneity such as permeability and porosity. The random travel process of CO2 is quantified by joint probability distributions and joint statistical moments (mean and variance), and the diffusion model of CO2 particle in random velocity field is established under the condition of non-linear and immiscibility in heterogeneous porous media. The micro mechanism of diffusion in heterogeneous porous media is revealed by numerical simulation. The general conclusion of steady state flow of CO2 diffusion in heterogeneous porous media was verified by simulating Sleipner CO2-brine storage in Norway.
Highlights
Over the past few decades, CO2 concentration will increase by 2.1% per year due to human activities, and the CO2 emissions are expected to increase to 3.72 billion tons per year by 2035 from global energy[1]
In order to study the influence of particle velocity on CO2 diffusion, the stochastic partial differential equations of particle velocity and CO2 saturation is needed
The diffusion of CO2 particle in heterogeneous porous media is studied in this paper
Summary
Over the past few decades, CO2 concentration will increase by 2.1% per year due to human activities, and the CO2 emissions are expected to increase to 3.72 billion tons per year by 2035 from global energy[1]. According to the latest report, the global average temperature has risen by 1°C compared with that before the industrial revolution due to the greenhouse effect caused by CO2 emissions. In order to ensure that CO2 can be safely stored in the formation for a long time, it is necessary to know the migration mechanism of CO2 in geological structures. Diffusion and advection will accelerate the rate of CO2 dissolution in brine, so that CO2 can be effectively and safely stored for a long time. The analysis of multiphase flow in porous media is of great significance. The nonlinear analysis of multiphase flow must be carried out according to the randomness of formation parameters for the migration of CO2 in heterogeneous porous media. The analysis of multiphase flow in heterogeneous porous media is usually more difficult than that of single-phase flow. The significant advantage of stochastic method is that the spatial heterogeneity of any reservoir is described by limited statistical properties such as mean and variance
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