Moench Solution for Fractured Aquifers
Description
A mathematical solution by Moench (1984) is useful for determining the hydraulic properties (hydraulic conductivity of fractures and matrix, specific storage of fractures and matrix, wellbore and fracture skin) of double-porosity fractured aquifers. Analysis involves matching the solution to drawdown data collected during a pumping test. The Moench solution accounts for flow in a double-porosity system consisting of consisting of low-permeability, primary porosity blocks and high-permeability, secondary porosity fissures with wellbore storage, wellbore skin and fracture skin. The matrix may contain either slab or spherical blocks. Moench (1988) added partial penetration and anisotropy capabilities.
AQTESOLV provides visual and automatic methods for matching the Moench solution to pumping test data. This easy-to-use and intuitive software promotes rapid and accurate determination of aquifer properties.
Assumptions
The following assumptions apply to the use of the Moench solution for double-porosity fractured aquifers:
- aquifer has infinite areal extent
- aquifer has uniform thickness
- aquifer potentiometric surface is initially horizontal
- wells are fully or partially penetrating
- fractured aquifer represented by double porosity system consisting of low-permeability, primary porosity blocks and high-permeability, secondary porosity fissures
- matrix consists of slab-shaped or spherical blocks
- flow is unsteady
- water is released instantaneously from storage with decline of hydraulic head
Solution Options
AQTESOLV provides the following options for the Moench pumping test solution:
- large-diameter pumping wells
- partial penetrating wells
- hydraulic conductivity anisotropy
- variable pumping rates
- multiple pumping wells
- multiple observation wells
- boundaries
Benchmark
AQTESOLV benchmark for Moench (1984) solution using data for pumped and observation wells (symbols) from Moench (1984).
References
Moench, A.F., 1984. Double-porosity models for a fissured groundwater reservoir with fracture skin, Water Resources Research, vol. 20, no. 7, pp. 831-846.
Moench, A.F., 1988. The response of partially penetrating wells to pumpage from double-porosity aquifers, Proceedings of the International Conference on Fluid Flow in Fractured Rocks, Atlanta, GA, May 16-18, 1988.
See also: solution methods, pumping tests