A Simulation of a Trap Mechanism for the Sequestration of CO2 into Gorae V Aquifer, Korea

This article presents the numerical modeling study to investigate the effect of CO2 sequestration in deep saline aquifer at Gorae V structure, Korea. This structure includes the Donghae-1 gas field, which is the only one producing in Korea. A simulation for 20 years of injection and 1,000 years of monitoring was conducted by using generalized equation-of-state model compositional reservoir simulator (GEM), which can simulate the flow of the CO2-water mixture to verify major trap mechanisms and sequestration characteristics in this system. By a number of simulations in reservoir conditions, the 3,000 ton/day of optimum injection rate was obtained within the limits of the rock fracturing pressure. As a result of simulation, since most of injected CO2 rises by a buoyancy and moves horizontally by the effect of cap rock, the radius of CO2 flowed out in the top layer is larger than bottom layer. Also, the change of dominant trap mechanism among structural, solubility, and residual trapping mechanism with time was examined. As residual gas saturation increases, the contact area between CO2 and formation water decreases. Thus, the quantity sequestrated by a solubility trap is reduced, and a greater amount of gas remains in the grid block. Also, gas saturation in some block was decreased below residual gas saturation due to the continuous dissolution and the formation water, accordingly, the formation water which its density was increased than surrounding blocks, sank to lower part of structure.