Modelling Techniques to Monitor the Injection of Carbon Dioxide in Deep Saline Aquifers

In this thesis we want to model all steps of a CO2 injection in deep saline aquifers, from the injection to the monitoring by means of seismic methods. After outlining the main physical and chemical processes which allow the CO2 to be trapped for very long periods of time, we present two numerical examples. In the first one, CO2 is injected in a complex aquifer, part of an anticlinal structure, with characteristics resembling those of the Sleipner field. The injection is monitored via an active cross-hole seismic experiment; in particular, we perform a tomographic inverion of the direct arrivals. In the second example, CO2 is injected at a constant rate for one hour in a homogenous aquifer. It is then monitored with a passive seismic method. In fact, the overpressure caused by the injection, may lead to the formation of microcracks and therefore to the emission of seismic waves. We approximate the position of the CO2 plume by finding these emitting points by means of a reverse-time migration algorithm.