Alteration Experiments of Formation Barrier due to Super Critical CO2

In order to reduce the volume of CO2 emission to the air, for mitigating global warming, the sequestration of CO2 into deep reservoirs is a desirable technique. To keep the CO2 sequestration safe over a very long period, it is required to know the degree of the effect of supercritical CO2 on the reservoir rock. We propose a long-term laboratory experiment to study these effects. In this experiment four rock samples are selected as surrounding materials of a reservoir. We selected two types of casing cement and two types of mudstone. They were soaked in super critical CO2 (60 degrees centigrade, 1500psi) for three months.

Some changes are observed on both the outside and inside of all cement samples. Many crystals of aragonite precipitate on the surface and in the pore space of cement samples. The porosity of samples is thus reduced by these crystals in the pore spaces. On the other hand, no change was observed in the mudstone samples. The sealing ability of the mudstone appears these unchanged over time, whereas the decreased porosity and permeability of the cement samples increases its sealing ability over time.