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CLIMIT-Forskning, utvikling og demo av CO2-håndtering

Pore-Scale Mechanism for CO2 Storage in a Fracture-Matrix System: Physical and Geometrical Effects

Awarded: NOK 9.0 mill.

An important property of potential storage sites for CO2 is the ability of the cap rock to serve as a geologic seal for the CO2 phase. Generally, capillary trapping of CO2 below internal low-permeable formation layers is one of the most relevant mechanism s for CO2 storage. Storage sites may also be fractured, and hence it is important to evaluate the possibility of the CO2 fluid to escape through fractured systems, leading to less efficient pore volume exploitation and at worst leakage if the cap rock int egrity is poor. For a safe and efficient long-term storage it is important that CO2 can enter the surrounding matrix blocks and remain stored in the pore space. Reservoir simulation studies of CO2 storage processes thus require accurate capillary pressure curves for the individual layers of different permeability, as well as for the fracture and matrix interactions, if fractures are present. In this project a pore-scale model will be developed for the computation of fluid distributions and capillary pre ssure functions for matrix-fracture systems by the level set and variational level set based methods, and hence extending previously published work in this field. Computations will be performed on 3D imaged pore space fracture-matrix geometries with narro w fractures. The conditions for which the fluids form continuous pathways across the fractures, or otherwise become trapped, will be analysed during the computations. The entry conditions for CO2 invasion into the matrix will be estimated to evaluate the capillary seal efficiency of the rocks. The effects of wettability will be explored. An increased understanding of fracture-matrix interactions is important to simulate CO2 storage processes at larger scales. Important mechanisms, such as CO2 dissolution in water, and mineral trapping by chemical reactions, is envisioned to be incorporated in the future, possibly by combining the level set based model with other approaches.

Funding scheme:

CLIMIT-Forskning, utvikling og demo av CO2-håndtering