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Effect of supercritical CO 2 on carbonates: Savonnières sample case study
Author(s) -
Shulakova V.,
Sarout J.,
Pimienta L.,
Lebedev M.,
Mayo S.,
Clennell M.B.,
Pervukhina M.
Publication year - 2017
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1111/1365-2478.12369
Subject(s) - supercritical fluid , microstructure , porosity , dissolution , mineralogy , carbonate , geology , materials science , porous medium , chemical engineering , composite material , chemistry , metallurgy , organic chemistry , engineering
CO 2 geosequestration is an efficient way to reduce greenhouse gas emissions into the atmosphere. Carbonate rock formations are one of the possible targets for CO 2 sequestration due to their relative abundance and ability to serve as a natural trapping reservoir. The injected supercritical CO 2 can change properties of the reservoir rocks such as porosity, permeability, tortuosity, and specific surface area due to dissolution and precipitation processes. This, in turn, affects the reservoir characteristics, i.e., their elastic properties, storage capacity, stability, etc. The tremendous progresses made recently in both microcomputed X‐ray tomography and high‐performance computing make numerical simulation of physical processes on actual rock microstructures feasible. However, carbonate rocks with their extremely complex microstructure and the presence of microporosity that is below the resolution of microcomputed X‐ray tomography scanners require novel, quite specific image processing and numerical simulation approaches. In the current work, we studied the effects of supercritical CO 2 injection on microstructure and elastic properties of a Savonnières limestone. We used microtomographic images of two Savonnières samples, i.e., one in its natural state and one after injection and residence of supercritical CO 2 . A statistical analysis of the microtomographic images showed that the injection of supercritical CO 2 led to an increase in porosity and changes of the microstructure, i.e., increase of the average volume of individual pores and decrease in the total number of pores. The CO 2 injection/residence also led to an increase in the mean radii of pore throats, an increase in the length of pore network segments, and made the orientation distribution of mesopores more isotropic. Numerical simulations showed that elastic moduli for the sample subjected to supercritical CO 2 injection/residence are lower than those for the intact sample.