(389c) Risk Assessment In CO2 Sequestration

A main concern for any sequestration system is whether it may leak CO2 over a long-term time horizon consisting of hundreds or thousands of years. The outcome depends on the competition between sequestration and leakage processes. Leakages after sequestration in an abandoned reservoir, for instance, may occur from failure of the manmade cement seal, or through naturally existing fractures in the caprock. On the other hand, the CO2 source pool may dissolve into formation water, migrate to water of surrounding formations, or react and mineralize. Modeling all these processes from first principles involves a number of parameters, such as various permeability and porosity values, that are not known with certainty.

To deal with uncertainty in model parameters, we develop a Monte Carlo simulator with analytical equations for geologic sequestration based on the CQUESTRA model [1]. To assess the uncertain long-term fate of CO2, we carried out multiple simulations with parameter values drawn from probability distributions based on data from the literature. The proposed methodology was also parallelized on a Graphics Processing Unit, where 100 times speedup was achieved compared to a four-threaded CPU implementation. Computational results will be presented for several failure scenarios, suggesting that most of the CO2 is safely trapped underground. Sensitivity plots further suggest that the leakage percentage is most sensitive to the permeability of the target reservoir.

Reference:

1. D. M. LeNeveu, ?CQUESTRA, A Risk and Performance Assessment Code for Geological Sequestration of Carbon Dioxide,? Energy Conversion and Management, 49(1), 32? 46, 2008.