Technical Committee Underground Storage Technology

Influence of Carbon Dioxide on Underground Gas Storage - Literature Study

This literature study was written to survey the effect of CO2 in underground gas storage. In the context of an increase of the proportion of renewable energies, biogas is inferred to increase CO2 amounts compared to the current CO2 level in natural gas (<1 %). This shift in CO2 concentration is assumed to reach the present EASEE-gas-standard value of 2.5 % in the German gas grid, coincide with the penetration of CO2 into underground storage. The effects of this situation are investigated.

For natural gas of similar CO2 concentrations, no effects on underground storage are published. Therefore, the following "extreme cases” with CO2 related effects to gas production and storage were analyzed: Sour gas (CO2 + H2S), EOR (100 % CO2), CCS-technology (100 % CO2) and town gas underground storage (CO2, CO, H2, O2).

In Conclusion, an increase of CO2 content up to 2.5% (EASEE-gas-standard) does not cause negative effects on integrity and reservoir properties of the facilities because they were designed for this CO2-content. The consequence of an increase up to 4 % (due to biogas processing) is not described in the literature but every increase in CO2 content will cause an increase in corrosion of wellbores and surface facilities, which may require corrosion control by material selection and inhibition methods. The interaction in reservoir with other associated materials of biogas is uncertain. A transferability of the experience of CO2 elevation in the injected gas and a subsequent increase in H2S concentration of the produced gas of several French UGS is not attestable. The acting mechanisms need to be clarified in order to assess the risk for German UGS for gas quality influence.