Feasibility of Injecting Large Volumes of CO2 into Aquifers

Abstract

Although it is recognized that deep aquifers offer a very large potential storage capacity for CO2 sequestration it is not clear how to fill the storage with a large volume of CO2 in a relatively short period of time. The typical benchmark for the rate of CO2 injection is 1 Mt/year when studying storage performance. This rate is very low compare to the scale necessary for the storage technology to play a significant role in managing global emissions. In this study we perform numerical simulations of a large volume of injection, 20 Mt/year during 50 years of continuous injection resulting in a total sequestration of 1 Gt CO2. A sensitivity analysis of the results (plume area and CO2 storage capacity) is presented within the range of aquifer parameters: thickness (50-100 m); permeability (25-100 mD); rock compressibility (from 9u10 -10 to 2u10 -9 (1/Pa)) as well as different injection arrangements. The implementation of this study to a particular case of injection of 1 Gt total over 50 years into the Nisku aquifer located in Wabamun Lake Area, Alberta, Canada [1] is presented. In this area, large CO2 emitters including four coal-fired power plants with emission between 3 to 6 Mt/year each are present. The Nisku aquifer is believed to be a suitable choice for future sequestration projects. In this case study a few injection scenarios (number of wells and their placement, which control the ability to inject without exceeding the aquifer’s fracture pressure) are presented. The evolution of plume size and pressure field in the aquifer for these scenarios is shown. As opposed to the generic sensitivity study, the case study includes the heterogeneity of the aquifer and its dip angle. Both generic and Nisku studies have shown that the capacity of the reservoir in the case of large injection volumes should be evaluated not by available pore volume, but by ability to inject some amount without exceeding fracture pressure of formation.