Application of a Linked Methodology for Probabilistic Evaluation of Three-Dimensional Carbon Dioxide Storage Capacities: A Case Study of the Pohang Basin, Korea

Abstract

The linked methodology is applied to perform probabilistic evaluation of individual gas-, liquid-, supercritical-, and whole fluid-phase carbon dioxide (CO2) storage capacities. In order to perform probabilistic evaluation of individual gas-, liquid-, supercritical-, and whole fluid-phase CO2 storage capacities, grid-based geologic formation volume, grid-based CO2 density, and grid-based CO2 storage capacity are evaluated through three-dimensional geologic modeling and grid-based Monte Carlo simulation sequentially as the linked methodology. The two clastic saline formations, which are the sandstone-dominant Fluvial Conglomerate and Sandstone (FCSS) and Shallow Marine Sandstone (SMSS) in the Pohang Basin, are selected as the target clastic saline formations. The results of the three-dimensional geologic modeling show that the six geologic formations are distributed very complicatedly both onshore and offshore with irregular depths and thicknesses, and they are partly dissected and offset by the eight major faults. The two clastic saline formations SMSS and FCSS are deep and thick at the three prospective areas such as Areas 1, 2, and 3 in the modeling domain. The results of the grid-based Monte Carlo simulation show the following three main contents. First, in the two clastic saline formations SMSS and FCSS, CO2 exists as gas, liquid, and supercritical phases with the corresponding distinctive density ranges depending on the pressure and temperature with depth. Second, the theoretical individual gas-, liquid-, supercritical-, and whole fluid-phase CO2 storage capacities all show asymmetric normal distributions. On the other hand, the effective individual gas-, liquid-, supercritical-, and whole fluid-phase CO2 storage capacities of the saline formations all show log-normal distributions, and their values are much lower than the values of the theoretical individual gas-, liquid-, supercritical-, and whole fluid-phase CO2 storage capacities. Third, in the SMSS, the grid-wise (elemental) theoretical and effective fluid-phase CO2 storage capacities are probabilistically higher at Area 1 (mainly as supercritical and liquid phases), intermediate at Area 2 (mainly as liquid and gas phases), and lower at Area 3 (mainly as a gas phase). However, in the FCSS, the grid-wise theoretical and effective fluid-phase CO2 storage capacities are probabilistically higher at Area 2 (mainly as supercritical and liquid phases), intermediate at Area 1 (mainly as a supercritical phase), and lower at Area 3 (mainly as a gas phase). Finally, four key criteria (parameters) for selecting or ranking the optimal CO2 storage locations are decided by summarizing and analyzing the results of the three-dimensional geologic modeling and grid-based Monte Carlo simulation. On the basis of the four key criteria (parameters), the overall suitability ranks of Areas 1, 2, and 3 for geologic CO2 storage are determined to be the first, second, and third, respectively.