Gas Flow in a Permeable Earth Formation Containing a Crack

Abstract

Gas flow in a permeable earth formation following an experimental underground nuclear explosion is analyzed to predict conditions that might lead to venting of radioactive gases to the atmosphere. A three-dimensional analysis considers flow of the explosion gas through the permeable earth formation as well as flow of the gas through a propagating crack. Effects of variations in permeability, k, from 10−6 to 1.0 (μm)2 and ratio of the maximum resistive overburden pressure to the initial gas-driving pressure of explosions, Prmax /P1 from 0.1–0.9 are delineated. Initial dimensions of the crack range from 30–110 m in the vertical direction, 30–170 m in the horizontal direction and 10–50 mm in thickness. Propagation of a crack to the earth’s surface following a typical experimental underground nuclear explosion buried at a depth of 500 m would require unusual conditions such as when k < 10−4 (μm)2 and Prmax /P1 < 0.75.