Modelling of CO2 storage in naturally fractured reservoirs

Abstract

Geological storage of CO2 is regarded as an important technology to achieve the targets of temperature increase established in the last decade. Naturally fractured reservoirs (NFRs) are ubiquitous across the world, but so far have received little attention as potential CO2 storage sites. Among the main concerns regarding storage in NFRs are the fast flow of the CO2 plume in the fracture network and the high capillary contrast between fractures and matrix that may keep CO2 in the fractures,which have very low pore volume. This thesis provides a systematic study of CO2 storage in NFRs. The dual-porosity method, which is typically used for simulating flow in NFRs, is used to evaluate under what geological conditions fractured formations can be used for storage. The dual-porosity method relies on transfer functions that model the matrix-fracture fluid exchange. New transfer functions that capture the transfer physics more accurately than existing models available in the literature are developed. These transfer functions are then applied to understand storage capacity and CO2 plume flow for conceptual fractured aquifers.The results presented in this thesis show that in principle fractured formations have storage potential if the geological conditions are suitable and injection rates are managed appropriately.