ABSTRACT: Hydro-chemo-mechanical coupling processes are significantly affected by the evolution of porosity and permeability, which are defined by chemical kinetics and effective stress conditions. In this study, high-pressure high-temperature (HPHT) flow-through experiments with a strain monitoring system on three samples with different micro-facies from the Pennsylvanian Paradox Formation's Cane Creek clastics were conducted under 75°C and 13.8 MPa to quantify the effect of pore fluid on permeability and bulk modulus. The studied pore fluids are air, N2, and CO2. These pore fluids were injected at different pressures ranging from atmospheric pressure to 2.1 to 7.6 MPa. In the later phase of the experiment, a high salinity of 3.71M NaCl followed by a CO2-NaCl mixture was injected into the sample to study the effect of reactive transport on the mechanical properties of the reservoir rock. We found that permeability and bulk modulus decrease with increasing pore fluid density, and high salinity injection fluid reduced dissolved CO2, leading to less mineral dissolution than expected. While both shale samples experienced porosity reduction overall due to hydro-chemo-mechanical coupling, changes in bulk modulus varied. The high-dolomite sample with a heterogenous cement texture experienced mechanical weakening, while the high-calcite high-clay sample with a relatively homogeneous cement texture experienced mechanical strengthening. This study highlights the importance of quantifying the source of porosity change - whether it is induced by dissolution/precipitation or stress compaction/relaxation - as porosity is crucial for evaluating reservoir storage capacity and integrity. This study contributes to the reservoir storage capacity and integrity and benefits geologic CO2 storage in many potential unconventional oil plays.
Wu et al. (Sun,) studied this question.