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Impacts of Mixed-Wettability on Brine Drainage and Supercritical CO2 Storage Efficiency in a 2.5-D Heterogeneous Micromodel

Citation

Chang, Chun et al. (2020), Impacts of Mixed-Wettability on Brine Drainage and Supercritical CO2 Storage Efficiency in a 2.5-D Heterogeneous Micromodel, Dryad, Dataset, https://doi.org/10.7941/D14P62

Abstract

Geological carbon storage (GCS) involves unstable drainage processes that affect CO2 storage efficiency and plume distribution. Drainage is greatly complicated by the mixed-wet nature of rock surfaces common in hydrocarbon reservoirs where supercritical CO2 (scCO2) is used in enhanced oil recovery. We performed scCO2 injection (brine drainage) experiments at 8.5 MPa and 45 °C in heterogeneous micromodels, two mixed-wet with varying water- and intermediate-wet patches, and one water-wet. The flow regime changes from capillary fingering through crossover to viscous fingering in the micromodels of same pore geometry but different wetting surfaces at displacement rates with logCa (capillary number) increasing from −8.1 to −4.4. While the mixed-wet micromodel with uniformly distributed intermediate-wet patches yields ~0.15 scCO2 saturation increase at both capillary fingering and crossover flow regimes (–8.1 logCa−6.1), the one heterogeneous wetting to scCO2 results in ~0.09 saturation increase only at the crossover flow regime (−7.1 ≤logCa≤−6.1). The interconnected flow paths in the former are quantified and compared to the channelized scCO2 flow through intermediate-wet patches in the latter by topological analysis. At logCa>−6.1 (near well), the effects of wettability and pore geometry are suppressed by strong viscous force. Both scCO2 saturation and distribution suggest the importance of wettability on CO2 storage efficiency and plume shape in reservoirs, and capillary leakage through caprock at GCS conditions.