Volume 33: CCUS Technologies for the Carbon Neutrality: Part I

Quantitative Characterization of CO2 Storage Mechanisms in Low-permeability Reservoirs Li Jiehan, Jin Songhe, Liao Xinwei

Abstract

CCUS is widely seen as a practical solution to the challenge of rising global temperatures. Enhanced oil recovery (EOR) using CO2 flooding, as part of CCUS, can achieve both long-term geological sequestration of greenhouse gases and improved crude oil recovery, bringing significant economic benefits. In a low-permeability field, long-term water flooding is no longer able to achieve good oil recovery results, and CO2 flooding methods are then adopted. Previous studies on CO2 storage in reservoirs have often used qualitative and static characterization methods for CO2 storage mechanisms. In this paper, based on the CO2 storage mechanisms in depleted reservoirs, a method for characterizing the CO2 storage mechanisms in low-permeability reservoirs is developed through quantitative characterization and dynamic analysis of the key parameters of the four storage mechanisms. A low permeability reservoir mechanism model is established, and the various characteristics of the four storage mechanisms with time and space as well as the distribution law are analyzed. Through this study, it can be concluded that structural and stratigraphic trapping and residual gas trapping are the main CO2 storage methods in low permeability reservoirs, while non fluid gas in the reservoir is the main contributor to residual gas trapping. In the later stage of storage, some CO2 is converted into residual gas in the reservoir. The effect of dissolution trapping is poor, and the influence of mineralization reaction on reservoir porosity in low permeability reservoirs is relatively small.

Keywords CCUS, Low permeability reservoirs, CO2 storage mechanisms, Quantitative analysis, Evolution patterns