Geomechanical and Geochemical impact of CO2 injection at the North Sea Cranberry Opportunity

Abstract

In an effort to reduce CO2 emissions, but still provide society with much used natural gas, Circular Energy wants to simultaneously produce natural gas and inject CO2, that is a result from production of electricity from natural gas. The effects of CO2 injection are researched, but not injection in a still full reservoir. Effects that need further research are dissolution of minerals, fluid-rock ratio, strain due to simultaneous production and injection, increased stress around the well bore due to delayed pressure distribution, possible injection into an aquifer and the precipitation of minerals, especially around the injection well bore, which would decrease permeability. Options to look into several of these effects are reactive transport modelling and reservoir modelling. Basic calculations indicate that the strength of the reservoir is high enough to produce natural gas and to inject CO2 at the onset. However the parameters used are hypothetical and the effective stress was not looked into. Especially ongoing injection might cause problems of unsure nature. Basic calculations indicate that flexural bending is probably not a severe effect as the maximum expected compaction is 3 cm and that due to the simultaneous injection the pores will not empty completely.