Experimental Study on the Density-Driven Carbon Dioxide Convective Diffusion in Formation Water at Reservoir Conditions

Abstract

Density-driven convection, which can accelerate the dissolution rate of carbon dioxide (CO 2 ) in resident brine, is critical for the long-term fate of the injected CO 2 permanence and security of CO 2 geological storage. Visualization experiments and pressure–volume–temperature (PVT) testing were conducted to investigate the influence from gravitational convection. For investigate gravitational instabilities and convective diffusion, we designed a Hele-Shaw cell rated to 70 MPa and Rayleigh number of 346 to conduct visualization experiments with the micro-schlieren technique. The average diffusion coefficient and time-dependent values were measured in the PVT experiments. We also calculated the convection parameters, including Rayleigh number and critical onset time, with a series of PVT testing at the temperature ranging 293.15–423.15 K and pressure ranging 14–24 MPa by using the constant-pressure method. Through visualization experiments, we observed convective currents triggered by the density gradient in the gas–liquid interface, which noticeably enhanced the CO 2 dissolution rate. The PVT testing confirmed that the diffusion coefficient increased sharply under the influence of the gravitational convection at the early stage and then decreased toward the average diffusion coefficient with time. The PVT testing also demonstrated the Rayleigh number increasing with temperature or pressure increasing under the reservoir conditions. The gravitational convection will be more likely to occur and more rapid with a greater pressure or higher temperature.

Visual investigation of CO2 dissolution and convection in heterogeneous porous media at reservoir temperature and pressure conditions

“…10 The convection-driven dissolution has been extensively studied experimentally for accelerated CO 2 dissolution in saline water under gravity for CO 2 storage inside two-dimension (2-dim) Hele-Shaw cells or 3-dimension (3-dim) cylindrical cells. [11][12][13][14][15][16][17][18][19][20][21][22] To make the CO 2 convective flow inside fluids (water or oil) analogous to 2-dim, Hele-Shaw cells are used. 23 Hele-Shaw cells are constructed by two parallel flat plates with a small gap in between (generally less than 10 mm).…”

Diffusion coefficients of CO2–SO2–water and CO2–N2–water systems and their impact on the CO2 sequestration process: Molecular dynamics and dissolution process simulations

“…1,2 There are extensive body of published works about the experimental and numerical aspects of this process. [3][4][5][6][7][8][9] However, high costs of CO 2 sequestration projects are a barrier in this topic. Based on this fact that large amount of costs is invested to purify CO 2 from the flue gas stream of the emission sources, some researchers introduced impure CO 2 sequestration as a way to tackle the economic issues.…”

Convective-reactive transport of dissolved CO2 in fractured-geological formations

“…Interactions between these processes during CO2 sequestration have been the subject of several theoretical, numerical, and experimental studies. A widely discussed issue is the CO2 dissolution in resident brine (i.e., solubility trapping) during sequestration in saline aquifers (Emami-Meybodi et al, 2015;Jafari Raad et al, 2019;Mojtaba et al, 2014;Tang et al, 2019). A comprehensive review of modeling and experimental works related to convective dissolution of CO2 in saline aquifers is presented in (Emami-Meybodi et al, 2015).…”