Isothermal Adsorption of CO2 in Shale as a Caprock at Different TOC

Abstract

Abstract Carbon dioxide (CO2) emissions are a significant contributor to global carbon and the resulting greenhouse effect. Reducing CO2 emissions, and even achieving carbon neutrality, has become a primary goal of environmental conservation worldwide. Carbon capture and storage (CCS) is a potential solution for reducing CO2 emissions by injecting captured CO2 into formations, such as shale. While shale formations have excellent sealing characteristics, CO2 diffusion into shale can limit the retention and maintenance of injected CO2. Understanding the adsorption behavior of CO2 in shale at different levels of total organic content (TOC) is therefore crucial. This study used a gravimetric approach to quantify the adsorption isotherm of CO2 in Eagle Ford shale sample with TOC value of 2.70 wt% using Magnetic Suspension Balance (MSB) at pressure up to 1.5 MPa and temperature at 25°C with another samples from literature review which from Silurian Longmaxi shale and Ordovician Wufeng shale. The results showed that LMX 1, sample from Silurian Longmaxi shale, which had the highest TOC content (3.04 wt.%), had the highest adsorption capacity for CO2. The Freundlich model was found to be the most accurate in describing the adsorption behavior with an R2 of 0.99 and an ARE (%) of less than 2%. This study highlights the importance of modelling the TOC of shale with adsorption isotherms to determine adsorption properties, especially for predicting the adsorption capacity of organic matter.