In addition to interactions with CCP2-funded experiments, headed by Charles Christopher of BP, Celia’s group has been considering how the most critical, and most uncertain, parameters associated with well leakage might be determined. For the well leakage models, by far the most important parameter is the effective permeability of the bulk materials that make up the well and its immediate surroundings. This includes the well cement, the casing, and any damage zone in the rock immediately surrounding the well. In the team’s models, a value of (bulk) permeability is assigned to this collection of materials, with a different value assigned to each vertical segment of each well, as field experiments to determine these values do not yet exist.
Celia and colleagues have proposed one such test, and analyzed the ranges of sensitivity in regard to what values of well permeability can be identified from the experimental measurements. If the method proposed is found to be reasonable, it can form the basis of a targeted field measurement campaign whose result would be a great reduction in the uncertainty associated with the most critical parameter in all leakage models. Such a reduction of uncertainty could significantly enhance prediction reliability, and thereby contribute to timely development of a regulatory and permitting framework for CO2 injection.