Cross-international boundary effects of CO2 injection

The Bunter Sandstone Formation in the Southern North Sea is a regional saline aquifer that extends across the median line between UK and Netherlands territorial waters. Numerical simulations of CO2 injection into a brine-saturated structural closure located in the UK sector have modelled the temporal development of an injection-induced pressure footprint, together with the potential role of faults in brine migration and pressure dissipation in the aquifer. The modelled pressure footprint extends into the Netherlands Sector and if the faults are considered migration pathways, brine expulsion rates of the order of 50 m3/day/km2 could be expected along the fault zones. This is equivalent to just over 105 Ml, during a 50 year injection period, of which approximately 40% is expelled along a fault beneath Netherlands territorial waters. The simulations have shown that brine displacement will facilitate CO2 injection into the Bunter Sandstone by alleviating pressure build-up, but an understanding of potential brine migration pathways, rates and environmental impacts must be demonstrated to regulators prior to injection.