Comment on “Double‐Porosity Models for a Fissured Groundwater Reservoir With Fracture Skin” by Allen F. Moench

Abstract

)This paper constitutes a commendable effort to summarize and expand the theoretical basis for the analysis of drawdown data for fractured terrane that can be characterized by matrix blocks. The method applies porous media theory to fractured rocks by defining saturated hydraulic conductivity of the fracture system as the product of the hydraulic conductivity by the ratio of the total volume of the openings to the bulk volume of the rock (block or fracture) according to the method described by Gringarten [1982). Moench 1984] incorporated the effect of a mineralized film (skin) on the wall of the fractures where the skin has its own separate hydraulic conductivity and its own thickness. The geometries of the block are considered in the controlling equation for the fissured network via the control of the geometry on permeability distribution and on boundary conditions. In several respects this approach is similar to the standard approach for leaky aquifers when leakage is derived from storage in the confining layer. except for the addition.of the hydraulic properties and thickness of the mineralized layer on the walls of the fractures. By varying the values of the hydraulic properties of the fracture system and the mineralized layer on the walls of the fractures, virtually any drawdown curve can be simulated by the theory. Not surprisingly the drawdown curves produced by the method (type curves) are similar in shape to standard leaky aquifer curves within the influence of boundaries or with the influence of partial penetration. The method could in fact produce curves identical to those of Hantush 1960] see Lohman. 1979] given appropriate geometry and the absence of a skin on the fractures.