Abstract
A core flooding experiment has been conducted to investigate the potential of imaging CO2-hydrate formation in reservoir rock. A sandstone core was flooded with CO2 at a pressure of 100 bar and then subjected to stepwise decreasing temperatures, from initial 10 °C, down to −6 °C in steps of 4 °C. The core was imaged using an industrial X-ray μ-CT at each temperature step. The initial brine saturation of the sandstone at the start of the cold CO2 flooding was around 50 %. A severe reduction of permeability was observed at temperatures of 2 °C and lower.
The permeability reduction is interpreted to be due to the formation of CO2-hydrate throughout the core, as evident from analysis of the μ-CT images. Formation of CO2-hydrate and resulting blockage is one of the risks connected to high-pressure CO2 injection into reservoir rock for geological storage sites. A thorough understanding of under which conditions CO2-hydrates can form in real reservoir rock and how the hydrate is distributed through the pore space of the rock is crucial to enable proper design of the injection operation and prevent issues of reduced CO2 injectivity in the storage operation.
The permeability reduction is interpreted to be due to the formation of CO2-hydrate throughout the core, as evident from analysis of the μ-CT images. Formation of CO2-hydrate and resulting blockage is one of the risks connected to high-pressure CO2 injection into reservoir rock for geological storage sites. A thorough understanding of under which conditions CO2-hydrates can form in real reservoir rock and how the hydrate is distributed through the pore space of the rock is crucial to enable proper design of the injection operation and prevent issues of reduced CO2 injectivity in the storage operation.