Efficient models for Microbially Induced CAlcite Precipitation as a seal for CO2 storage (Project MICAP)

Storage of CO2 in North Sea formations can make a significant contribution to mitigate climate change if several gigatonnes per year are stored. These high injection rates will be linked to large pressure buildup, especially near injection wells, leading to a concern for leakages.A promising method to stop leakages is to produce biofilms that clog the top of the storage formation in the tens of meters around the injection well that experience the highest pressure buildup. The activity of some bacteria will also lead to formation of calcite, which further seals the rock. This is called microbially induced calcite precipitation.

So far, laboratory measurements and simulation tools have mainly focused on the sub-meter scale.For field-scale application of this method, it is important to be able to design a strategy for injection of microbes and other components that favors a seal at the top of the formation while maintaining the possibility to inject CO2 further down. To be able to answer questions such as these, current models must be upscaled. It is well known that use of subsurface flow models that include reactions can produce large errors if not properly upscaled.

Small-scale variability in concentration of microbes and solutes due to variable rock properties is a key factor here. Thus, this project will develop a robust and efficient model that includes small-scale variability within a large-scale simulation tool.

A combination of methods will be used that take into account transfer of components between zones of different flow rate and variability within large grid cells, and these models will be carefully coupled on the field scale. As a practical outcome of the project, the developed simulation tool will be used to test and improve strategies that are favorable for obtaining an extensive seal without compromising the injection of CO2. As such, the project will contribute to safe and efficient CO2 storage.