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The general form of non-linear single-phase pressure diffusion model@model is given by: 

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anchorNL_SPD
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\beta({\bf r},p) \, \frac{\partial p}{\partial t} = \nabla \Big( M({\bf r},p, \nabla p) \cdot \nabla p \Bigphi \cdot c_t \cdot \partial_t p -   \nabla  \left( M \cdot ( \nabla p - \rho \cdot \mathbf{g} )   \right)  - c \cdot M \cdot (\nabla p)^2  = \sum_k q({\bf r}) \cdot \delta({\bf r}-{\bf r}_k)

with non-linear dependence of fluid mobility 

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bodyM
on reservoir pressure 
LaTeX Math Inline
bodyp
and spatial pressure gradient 
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body\nabla p
:

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c_t({\bf r},p)  = c_r({\bf r},p) + \sum_\alpha s_\alpha({\bf r}) c_\alpha(p) 

where

LaTeX Math Inline
bodyM(p, \nabla p)

Fluid mobility as function of reservoir pressure 

LaTeX Math Inline
bodyp
 and spatial pressure gradient 
LaTeX Math Inline
body\nabla p

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bodyM_r(p, \nabla p)

Relative mobility as function of reservoir pressure 

LaTeX Math Inline
bodyp
 and spatial pressure gradient 
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body\nabla p

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body \beta(p)

Compressivity as function of reservoir pressure 

LaTeX Math Inline
bodyp
 

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bodyc_t({\bf r},p)

Total compressibility as function of reservoir pressure 

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bodyp
 and location
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body\bf r

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body c_r({\bf r},p)

Rock compressibility as function of reservoir pressure 

LaTeX Math Inline
bodyp
 and location
LaTeX Math Inline
body\bf r

LaTeX Math Inline
body c_\alpha(p)

LaTeX Math Inline
body\alpha
-phase compressibility as function of reservoir pressure 
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bodyp
 for
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body\alpha = \{ w, \, o, \, g \}

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body s_\alpha({\bf r})

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body\alpha
-phase reservoir saturation for
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body\alpha = \{ w, \, o, \, g \}

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body\phi_e({\bf r}, p)

Effective porosityas function of reservoir pressure 

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bodyp
 and location
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body\bf r

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bodyk_{air}({\bf r})

Formation permeability at initial formation pressure

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bodyp_0
as function of location
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body\bf r

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body\mu(p_0)

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body\xi (p, |\nabla p|)

Some function of reservoir pressure 

LaTeX Math Inline
bodyp
 and spatial pressure gradient 
LaTeX Math Inline
body\nabla p
with the following asymptotic behaviour:
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body\xi (p \rightarrow p_0, |\nabla p| \rightarrow 0) \rightarrow 1


The same account for non-linearity can be applied for non-linear multi-phase pressure diffusion when Pressure Diffusion Model Validity Scope is met and multi-phase pressure dynamics can be modeled as effective single-phase pressure dynamics.

Below is the list of popular physical phenomena and their mathematical models which can be covered by 

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anchorNL_SPD
 model.

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Forchheimer Equation


Pressure diffusion equation is going to be:

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\с_t \phi_e \frac{\partial p}{\partial t} = \nabla ( \frac{k(\nabla p)}{\mu} \nabla p)

where

LaTeX Math Inline
bodyk(\nabla p)

Dynamic fluid viscosity as function of reservoir pressure 

LaTeX Math Inline
bodyp
 

LaTeX Math Inline
bodyk(p)

Formation permeability as function of reservoir pressure 

LaTeX Math Inline
bodyp
 

LaTeX Math Inline
bodyc_f(p)

Total compressibility as function of reservoir pressure 

LaTeX Math Inline
bodyp
 


See also

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Pressure diffusion / Pressure Diffusion @model /  Single-phase pressure diffusion model  / Non-linear single-phase pressure diffusion @model

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