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Matrix-fracture pressure stabilization time

Time for matrix-to-fracture pressure stabilization  (Warren-Root, 1963)
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This calculator helps to illustrate the importance of fracture intensity (spacing) on matrix-fracture pressure stabilization time, i.e. how quick is the fracture pressure decline at a well impacted by matrix-to-fracture flow.

 

Input:

  • Oil saturation, the fraction of pore volume occupied by oil

  • Water saturation, the fraction of pore volume occupied by water

  • Matrix and fracture porosity (pore volume % of bulk volume)

  • Effective permeability of fracture network and/or matrix

  • Matrix and fracture Pore Volume Compressibility (change in pore volume with pore pressure)

  • Fracture spacing in x and y (assume idealized, uniform fracture spacing in 2 dimensions)

  • Wellbore radius

  • Effective total viscosity of fluids in the system

  • Oil fluid compressibility (change in oil volume with pore pressure)

  • Water compressibility (change in water volume with pore pressure)

  • Gas compressibility (change in gas volume with pore pressure)

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Note: 

rw and kfe have no impact on inflection points

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warren-root.png
Warren-root-equations.png

Output:

  • Calculated total compressibility (pore volume plus total fluid compressibility)

  • Calculated matrix shape factor (a function of fracture spacing as per equation)

  • Calculated transmissivity ratio (matrix-to-fracture flow capacity relative to fracture only flow capacity as defined in equation)

  • Storage ratio (fracture storage  capacity relative to total system storage capacity as defined in equation)

  • Inflection time (mid pressure decline inflection  point  between early (fracture only)  and late time (fracture + matrix)  in well pressure decline as defined by equation)

  • End of Early St. Line (end of early time well pressure decline  when matrix first impacts well pressure as given by equation )

  • Start of 2nd St. Line (start of late time well pressure decline when both matrix and fracture simultaneously impact pressure decline as given by equation)

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Symbols in calculator refer to figures above

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Author: James R. Gilman 

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This calculator is not designed to work on mobile devices

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JAVASCRIPT MUST BE ENABLED IN YOUR BROWSER FOR THIS CALCULATOR TO WORK PROPERLY

 

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