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Simulation of Gravitational Instability and Thermo‐Solutal Convection During the Dissolution of CO 2 in Deep Storage Reservoirs
Author(s) -
Singh Mrityunjay,
Chaudhuri Abhijit,
Stauffer Philip H,
Pawar Rajesh J
Publication year - 2020
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2019wr026126
Subject(s) - caprock , dissolution , plume , convection , supercritical fluid , brine , geology , instability , materials science , petroleum engineering , petrology , thermodynamics , mechanics , chemistry , physics
The temperature of deep hydrothermal sedimentary reservoirs varies between 50 and 250 °C, while the temperature of injected CO2can be much below the reservoir temperature. Most past studies did not consider temperature effect on the CO2dissolution trapping in storage reservoirs. We have performed numerical simulations of coupled multiphase flow, solute, and heat transport for liquid/supercritical CO2injection in a storage reservoir for different reservoir temperature, injection temperature, and reservoir permeability. During the injection of relatively cool CO2in a warmer storage reservoir, brine density increases with CO2concentration causing solutal fingering in the diffusive boundary layer and the creation of an isolated dissolved CO2plume (gravity trunk) below the injection zone. We have found that in many cases, the formation of a gravity trunk creates a large convection roll beneath the injection point. For low and moderate reservoir temperatures (100 and 175 °C), solutal fingers are pulled towards the injection zone by the large gravity trunk convection roll. In contrast, for higher temperature reservoirs (>206 °C), brine density decreases with dissolved CO2concentration. Hence, for a reservoir temperature of 250 °C, solutal fingers do not develop, but reverse fingering from a dissolved CO2mound is visible. We conclude that dissolution trapping achieves greater effectiveness for a reservoir temperature of 175 °C than those at 100 and 250 °C. We have also observed that free‐phase CO2below the caprock spreads faster for higher reservoir temperature and higher permeability, but it is not sensitive to injection temperature.