Quantifying the interaction between a single kerogen molecule and shale fluids from the perspective of elements and chemical groups

Abstract

During the implementation of underground H₂ storage (UHS), geological CO₂ sequestration (GCS), and CO₂-enhanced oil recovery (CO₂-EOR) measures in shale reservoirs, kerogen will interact with typical shale fluids (H₂, CO₂, shale oil and gas). These interactions will thereby affect the implementation effects of the above industrial measures. Kerogen at various maturity degrees exhibits complex interactions with shale fluids due to its different molecular structures, which are shaped by factors such as reservoir type, maturation time, and geological environment. Despite this complexity, the types of elements (C, H, O, N, and S) and chemical groups that constitute kerogen molecules are limited. In this study, we utilized molecular dynamic (MD) simulations to reveal the interaction mechanism between a single kerogen molecule and typical shale fluid (H₂, CH₄, Neopentane, and CO₂) from the perspective of component elements and chemical groups. In addition, we developed an interaction energy fitting formula to quantify these interactions without relying on MD simulations, thereby facilitating the rapid assessment of the difficulty in separating shale fluids from shale organic matter. Lastly, we proposed two simplification strategies to reduce the experimental procedures involved in constructing kerogen molecules, while allowing for a certain degree of evaluation of the interaction between kerogen and shale fluids.