Speaker
Description
Near-wellbore effects play a key role in controlling the performance of CO₂–WAG injection in carbonate reservoirs, particularly in complex environments such as the Brazilian Pre-Salt. The skin factor, which quantifies changes in flow capacity resulting from formation damage or well stimulation, directly affects injectivity and strongly influences both hydraulic behavior and geochemical processes. This study investigates the impact of skin factor variability on the long-term performance of WAG injection and CO₂ storage through numerical simulations performed in a heterogeneous carbonate reservoir model representative of Pre-Salt conditions. A fully compositional formulation coupled with geochemical reactions was adopted to capture fluid–rock interactions associated with CO₂-enriched injection cycles over a 31-year operational period. The simulation results indicate that stimulated scenarios promote earlier oil production, whereas damaged cases yield higher final cumulative oil recovery. Analysis of injector bottom-hole pressure shows that stimulated wells consistently require lower injection pressures than damaged wells, with the largest differences observed during the water injection phases. The average salinity in the reservoir decreases over time due to the lower salinity of the injected water and the occurrence of salt precipitation. Calcite dissolution is observed during the initial years as a result of carbonic acid formation, followed by calcite precipitation at later times, with the highest precipitation levels occurring in the most stimulated case. Gas saturation behavior was also evaluated as an indicator of CO₂ storage efficiency. In the early years, highly stimulated scenarios exhibit higher gas saturation; however, a trend inversion is observed over time. After 31 years of operation, the more damaged wells present higher gas saturation in the porous medium. This result indicates that higher well stimulation does not necessarily lead to improved long-term CO₂ storage performance, highlighting the importance of properly accounting for near-wellbore conditions in the design and optimization of WAG projects aimed at both enhanced oil recovery and geological CO₂ sequestration.
| Country | Brazil |
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