CO2 Plume Estimation with Automatic Calibration of TOUGH Model for Carbon Sequestration in Geological Formations

In order to assure safe carbon sequestration in geological formations, estimation of the CO2 plume from monitoring data is needed. We investigate methodologies to use field measurements and numerical simulations to find the plume position and to obtain a better understanding of the interaction of different mechanisms that govern the CO2 flow in the geological formation. The challenge is to be able to give an accurate prognosis of the plume location while dealing with uncertainties and model error. We use the TOUGH2 program, which is a numerical simulator for multi-phase fluid and heat flow in porous and fractured media, along with the ECO2N module, specific for CO2 flow in brine. This model describes the coupling of flow and geological processes. We also use the optimization program ORBIT to calibrate the model parameters. ORBIT (Optimization by Radial Basis Function Interpolation in Trust-Regions) has proven to be computationally efficient for environmental models that are computationally expensive. It is a derivative-free method, which makes it easier to use in conjunction with a complex nonlinear simulation model. We use a three-dimensional saline aquifer for the application.