The implemented Moench solutions calculate drawdowns in fractures and in blocks of fractured-porous media for various shapes of blocks and fractures. ANSDIMAT uses algorithm of DP_LAQ code (A.F. Moench, 1990) for parameter estimation.
See: Moench A.F. Double-porosity models for a fissured groundwater reservoir with fracture skin // Water Resources Research. 1984. Vol. 20, N 7. P. 831–846.
Solutions are available for the following types of the porous media: 1) slab-shaped blocks, 2) sphere-shaped blocks; 3) orthogonal fracture system (model of Warren-Root).
The figure above shows the slab-shaped blocks and the sphere-shaped blocks. The figure below shows the orthogonal fracture system.
z – distance from the block center to the fracture; the point in which drawdown is calculated is specified in the "Offset" editor.
Unsteady-state flow equations
1. Drawdown in fracture (s) and block (s') for slab-shaped blocks and sphere-shaped blocks
2. Drawdown in the aquifer with orthogonal fracture system
Solutions take into account storage capacity and skin effect of the pumping well. For slab-shaped blocks and sphere-shaped blocks skin effect in the fracture is additionally accounted for.
Laplace transform solution
Drawdown in fracture
Drawdown in pumping well
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drawdown in block |
Slab-shaped blocks |
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Sphere-shaped blocks |
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Model Warren-Root: drawdown in observation well
and pumping well
The table below explains notations for Moench’s solutions
Parameter |
Explanation |
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Hydraulic conductivity of the fracture system , m/day |
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Hydraulic conductivity of the block system, m/day |
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Hydraulic conductivity of an "average" fracture, m/day |
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Hydraulic conductivity of an "average" block, m/day |
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Specific storage of the fracture system, 1/m |
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Specific storage of the block system, 1/m |
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Specific storage of an "average" fracture, 1/m |
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Specific storage of an "average" block, 1/m |
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Volume of the fracture system, m3 |
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Volume of the block system, m3 |
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Total volume, m3 |
