Uncertainty Quantification of Gas Transport in Fractured Rocks Resulting from Underground Nuclear Explosions: Exploring the Damage-Permeability Relationship

Gas migration following underground nuclear explosions (UNEs) is tightly coupled to the resulting rock damage and pressure driven fractures, which create pathways for the gas to escape the near field and potentially reach the surface. High fidelity simulations of rock damage from UNEs can sufficiently resolve the true damage patterns from UNEs; however, to predict the breakthrough of gas at the surface, one needs to convert rock damage, a relatively non-intuitive parameter, to hydraulic parameters (e.g., permeability, porosity) for flow and transport simulation codes to model gas transport through the subsurface fracture network and rock matrix. Despite this critical need, there has not been in depth study of how to link damage to permeability. In this work, we approach this problem from an uncertainty quantification perspective by defining a truncated exponential relationship between damage and permeability with an unknown coefficient and exponent. We reduce the range of possible input space using historical data, but explore ranges of the input space and their effects on the breakthrough behavior of gas at the surface, while fixing the other boundary and initial conditions. We find that the gas breakthrough behavior is sensitive to the initial choices of coefficient and exponent, underscoring the need for additional comparisons to historical testing and analog data.