Sealing of fractures in a representative CO2 reservoir caprock by migration of fines

The impact of fines migration on fracture transmissivity reduction was investigated by injecting a brine solution containing a suspension of 0.1 wt.% kaolinite particles with a mean particle size distribution of 9.6 mu m through fractured shale core samples. The fractures had apertures estimated to be approximately 100 mu m. A mass balance approach was used to determine the quantity of kaolinite that was deposited within the fractures (influent - effluent = amount deposited in fractures). Large fractions (44-90%) of the suspended kaolinite pumped through the fractures were deposited within the fractures. Based on fracture volumes estimated with X-ray computed tomography, it was determined that approximately 10 to 17% of the fracture volume was filled with kaolinite at the point when flow was completely restricted. These results indicate that 100 mu m fractures in CO2 reservoir caprocks could be sealed within hours if the brines passing through the fractures contain a proportional volume of particulates to the tests performed in this laboratory study. (c) 2021 Battelle Memorial Institute. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons Ltd.