CO2SHALESTORE

CO2 Sorption and Flow in Shale Reservoirs

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 Obiettivo del progetto (Objective)

'Carbon dioxide storage in geological porous media (oil bearing rocks, coals, aquifers) has been the focus of attention in Europe for the last decade. The most desirable case of geological storage is when injected CO2 is enhancing production of energy source such as is the case of Enhanced Oil Recovery (EOR) or Enhanced Coalbed Methane (ECBM). Recently discovered shale gas reservoirs Poland might be also a target for carbon dioxide storage. The mechanism of gas trapping in shale gas is similar to that of coal. Gas is physically adsorbed on the surface of porous shale structure and moves with diffusive flow. If the fracture is created, gas moves in fractures according to Darcy’s law and desorbed from pores according to Fickean’s diffusive flow. Hence, if the fractures are created it might be possible to inject CO2 in order to store it in a similar manner as in case of ECBM. Two issues regarding CO2 storage in porous media are important: its capacity to store intended volume of CO2 and injectivity to receive CO2 at the supply rate. In case of shale reservoirs these two parameters can be measured as sorption capacity and permeability. Shale gas reservoirs are known to be low permeable (0.001 md to 0.1 md). However, permeability of such reservoirs can be significantly increased by hydraulic fracturing. Therefore, the objectives of this research proposal are: assessing the possibilities of CO2 storage in gas bearing shale and to investigate the possibility of enhanced shale gas recovery by CO2 injection. For the purpose of the study gas bearing shale samples from Poland will be investigated. First part of the research will involve CO2 interactions with shale gas reservoirs. Whereas the second part will investigate the possibility of enhanced gas recovery from gas shale by CO2 injection in simulated in-situ conditions and artificial fracture. Obtained parameters will serve as the basics for mathematical models of CO2 storage and flow in tight reservoirs.'

Introduzione (Teaser)

A recent EU-funded project investigated whether depleted shale gas reservoirs can be used to sequester carbon dioxide (CO2).

Descrizione progetto (Article)

Long-term storage of CO2 gas in porous rock is considered a promising route for decreasing CO2 emissions. In some cases, this storage can even improve yields from associated fossil-fuel mining activities.

The 'CO2 sorption and flow in shale reservoirs' (CO2SHALESTORE) project investigated whether gas-bearing shale can be used to store CO2. They also looked at whether CO2 injection could be used to improve yields from gas-bearing shale fracturing activities.

Five shale samples were collected from an area in Poland and sent to the laboratory for analysis. The project first analysed the composition of these shales to understand any changes that would occur after long-term CO2 storage.

Researchers also assessed the CO2 storage capacity of these shales by injecting CO2 gas at high pressure. The project found that without the presence of organic carbon in the shale, CO2 storage was dependent on high clay content.

Overall, CO2SHALESTORE showed that the shales could not store large amounts of CO2. Further, the presence of CO2 did not improve methane recovery.

Researchers concluded that more work was required to find a successful way to store CO2 in gas-bearing shales.