Characterization of Leaky Deep Saline Aquifer for Storing sc-CO₂

Abstract

The increase in the emissions of greenhouse gases is driving the rapid climate change in the earth's environment. Carbon dioxide is one of the most abundant greenhouse gases emitted into the atmosphere. Capturing CO 2 gas is essential to limit gas emissions released into the surrounding environment. CO 2 injection into deep geological formations is a popular method of storing CO 2 . Among these formations, deep saline aquifers are known to possess higher compatibility for the better storage of CO 2 . However, the leakage pathways formed due to poorly sealed abandonment wells, faults, and fracture networks in the caprock reduce the CO 2 storage efficiency. Determining the leakage rates is essential for understanding the storage efficiency of the aquifer. Therefore, a numerical model is developed to evaluate the leakage rates economically. The present study considers a domain consisting of two interconnected aquifers with a leakage in the caprock to understand the influence of various characteristics of the leakage path and aquifer on the CO 2 leakage rates. The normalized leakage rate is also evaluated with time during CO 2 gas injection. The results from the developed model depicted the variations in leakage path distance, thickness of the leakage path, permeability, and depth of the aquifer to affect the CO 2 migration in the bottom aquifer and storage efficiency. The evaluated normalized leakage rates varied from 0.2 to 0.175 with a change in leakage distance, and these rates significantly increased from 0.04 to 0.38 with an increase in leakage thickness. In addition, the normalized leakage rate is changed from 0.22 to 0.0004 with a decrease in permeability in orders from 10 −13 to 10 −15 m 2 and becomes uniform at 0.2 with injection time for depth variation. In addition, the porosity of the leakage path has a negligible impact on the leakage rates and gas migration into the upper aquifer. Overall, the study ascertained the influence of the leakage path on the efficacy of the aquifer for storing CO 2 .