Influence of highly permeable faults within a low‐porosity and low‐permeability reservoir on migration and storage of injected CO2

Abstract

AbstractFaults in CO2 storage reservoirs affect the migration and spatial distribution of injected CO2 in reservoir formations. Based on geological data from the Ordos CO2 geological storage demonstration project site, A 2D numerical model of the CO2 storage reservoir was constructed to study the influence of high‐porosity and high‐permeability faults within a low‐porosity and low‐permeability reservoir. The results show that the faults had a significant effect on CO2 migration and storage. If the permeability of the fault zone increased by 2–3 orders of magnitude (a common range of variation in fault zone) and porosity increased correspondingly compared to the base case (no fault in strata), the CO2 migration distance in the reservoir after 100 years was approximately 1.18 times larger than that of the base case without faults, and the total CO2 storage amount in the entire reservoir increased by 1.40–1.61 times. The faults weakened the sealing ability of the local interlayer caprocks (mudstone), which resulted in CO2 migrating through mudstone and entering in the neighboring interlayer storage stratum. When highly permeable faults existed, the CO2 migration distance and storage amount in the neighboring interlayer storage stratum were approximately two times and 19.41 times (maximum value) higher, respectively, compared with the case without a fault. Therefore, the faults distributed in strata should be given sufficient attention when selecting a CO2 sequestration site.