2019 Volume 62 Issue 6 Pages 309-318
Preventing channeling flows during enhanced oil recovery targeting heterogeneous or fracture type reservoirs and leakage flows from saline aquifers containing CO2 remains a challenge. This study evaluated the potential of in-situ gelation as a blocking agent in a heterogeneous reservoir using the reaction between aqueous solution of sodium metasilicate (Na2SiO3 · 9H2O; S–MS) and dissolved carbon dioxide (CO2). Both Raman and scanning electron microscopy/energy dispersive X-ray (SEM-EDS) spectroscopy revealed that the gel was a sodium carbonate type (S–C-gel). Physical characterization of the S–C-gel including the gelation time, gel strength and stability, were investigated in respect of S–MS concentration, temperature, salinity (NaCl), divalent ion concentration (calcium, Ca2+) as well as CO2 injection pressure. Gelation time after CO2 gas injection was around 1 to 24 h depending on temperature and pressure. Gel strength increased with higher S–MS concentration (≤ 10 wt%) and CO2 gas pressure (≤ 5.5 MPa). Threshold pressure gradient (TPG) and gas permeability of the sandstone core filled with in-situ gel increased by 2.6 times and decreased about 1/10, respectively, compared with the water saturated core. These promising findings herein could be extended to CO2 sequestration.