Regional CO2 Storage Simulations on the Troll Aquifer Model

Abstract

Abstract In this work, we present a workflow of first-order static approximations together with dynamic simulations on the Troll Aquifer model. The first-order static approximations consist of pressure-limited storage capacity based on maximum allowable overpressure (with respect to fracture pressure threshold) of a closed system, and injectivity index calculations to map suitable areas of the model to place injection sites. Based on conservative choices of parameters, the pressure-limited storage capacity of the Troll Aquifer model was 300-500 Mt. The injectivity index calculations showed that areas in the northern part of the model were most suited for injection sites, but areas in the south could be used with lower injection rates. Based on the first-order static approximations, dynamic simulations were set up to assess potential injection sites. It was shown that wells spread across the northern and southern parts of the model could handle injection of 500 Mt over 25 years in terms of pressure constraints in the injection period. Further simulation of a 500-year post-injection period showed that the CO2 plumes were fairly contained around the injection sites, with almost 30% of the CO2 being dissolved into brine. The pressure distribution at the end of simulation reached, in most places, an equilibrium of around 25 bar, where the fracture pressure limit was exceed by a very small amount (at most around 0.6 bar) after approximately 225 years in locations far from the CO2 plumes. This showed that the pressure-limited storage capacity was a good estimation of the actual capacity in our case study.