A methodology to estimate maximum probable leakage along old wells in a geological sequestration operation

► We present a methodology to help geological sequestration regulators and operators. ► We model the leakage of CO2 through old wells using a semi-analytical model within a Monte Carlo approach. ► Two scenarios on how to assign effective well permeability are explored. ► Maximum probable leakage after 50 years is compared with percent-per-year leakage rates.