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The general form of non-linear 
single-phase pressure diffusion @model with the finite number of sources/sinks is given by: 


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\phi \cdot c_t \cdot \partial_t p + \nabla  {\bf u}  
+ c \cdot ( {\bf u} \, \nabla p)
= \sum_k q_k(t) \cdot \delta({\bf r}-{\bf r}_k)



LaTeX Math Block
anchoruu
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{\bf u} = - M \cdot ( \nabla p - \rho \, {\bf g})


where

LaTeX Math Inline
body--uriencoded--p(t, %7B\bf r%7D)

reservoir pressure

LaTeX Math Inline
bodyt

time

LaTeX Math Inline
body--uriencoded--\rho(%7B\bf r%7D,p)

fluid density 

LaTeX Math Inline
body--uriencoded--%7B\bf r %7D

position vector

LaTeX Math Inline
body--uriencoded--\phi(%7B\bf r%7D, p)

effective porosity 

LaTeX Math Inline
body--uriencoded--%7B\bf r %7D_k

position vector of the

LaTeX Math Inline
bodyk
-th source

LaTeX Math Inline
body--uriencoded--c_t(%7B\bf r%7D,p)

total compressibility 

LaTeX Math Inline
body\delta ( \bf r )

Dirac delta function

LaTeX Math Inline
bodyq_k(t)

volumetric flowrate of the

LaTeX Math Inline
bodyk
-th source

LaTeX Math Inline
body\nabla

gradient operator

LaTeX Math Inline
body--uriencoded--%7B \bf u %7D

fluid velocity

LaTeX Math Inline
body--uriencoded--%7B \bf g %7D

gravity vector

LaTeX Math Inline
bodyM = k / \mu

phase mobility



LaTeX Math Inline
bodyk

formation permeability to a given fluid



LaTeX Math Inline
body\mu

dynamic viscosity of a given  fluid




Expand
titleDerivation


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Derivation of Single-phase pressure diffusion @model



The alternative form is:

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anchorXSQUE
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\phi \cdot c_t \cdot \mu \cdot \partial_t \Psi -   
 \nabla \cdot \left( k \cdot  \Big( \vec \nabla \Psi  - \frac{\rho^2}{\mu}  \, {\bf g} \Big)  \right) 
  = \sum_k q({\bf r}) \cdot \delta({\bf r}-{\bf r}_k)

where

LaTeX Math Inline
body--uriencoded--\displaystyle \Psi(p) =2 \, \int_0%5ep \frac%7Bp \, dp%7D%7B\mu(p) \, Z(p)%7D

Pseudo-Pressure

LaTeX Math Inline
body\mu(p)

dynamic fluid viscosity

LaTeX Math Inline
bodyZ(p)

fluid compressibility factor



Expand
titleDerivation


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Derivation of Single-phase pseudo-pressure diffusion @model



Physical models of pressure diffusion can be split into two categories: Newtonian and Rheological (non-Newtonian) based on the fluid stress model.

Mathematical models of pressure diffusion can be split into three categories: LinearPseudo-linear and Non-linear

These models are built using Numerical, Analytical or Hybrid pressure diffusion solvers.

Many popular 1DR solutions can be approximated by Radial Flow Pressure Diffusion @model which has a big methodological value.


The simplest analytical solutions for pressure diffusion are given by 1DL Linear-Drive Solution (LDS) and 1DR Line Source Solution (LSS)


The table below shows a list of popular well and reservoir pressure diffusion models.


Wellbore storage modelWell modelReservoir modelBoundary model
ConstantSkin-factorHomogeneousInfinite
FairVertical wellDual-porosityCircle No Flow
Rate-dependant

Fractured vertical well

Dual-permeabilityCircle Constant Pi

Limited entry wellAnisotropic reservoirSingle fault

Horizontal wellMulti-layer reservoirParallel faults

Slanted wellLinear-compositeIntersecting Faults

Multifrac horizontal well

Radial-composite


See also


Physics / Mechanics / Continuum mechanics / Fluid Mechanics / Fluid Dynamics / Pressure Diffusion / Pressure Diffusion @model