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

LaTeX Math Block
anchorPZ
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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)
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anchoruu
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{\bf u} = - M \cdot ( \nabla p - \rho \, {\bf g})
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anchorqGamma
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{\rm F}_{\Gamma}(p, {\bf u}) = 0

where

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

reservoir pressure

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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
body

q_k(t)sandface flowrates of the
LaTeX Math Inline
bodyk
-th source

M = k / \mu

LaTeX Math Inline
body\nabla

gradient operator

LaTeX Math Inline
body

M =

k

/ \muphase mobilityformation permeability to a given

formation permeability to a given fluid

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

gravity vector

LaTeX Math Inline
body

k

\mu

dynamic viscosity of a given 
 fluid

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

fluid velocity under Darcy flow 

LaTeX Math Inline
bodyq_k(t)

sandface flowrates of the

LaTeX Math Inline
body

\mu

k
-th well

LaTeX Math Inline
body\Gamma

reservoir boundary

LaTeX Math Inline
body--uriencoded--%7B\rm F%7D_%7B\Gamma%7D(p, %7B\bf u%7D)

reservoir boundary flow condition through the reservoir boundary

LaTeX Math Inline
body\Gamma
, which is usually the aquifer or gas cap

dynamic viscosity of a given  fluid



Expand
titleDerivation
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Derivation of Single-phase pressure diffusion @model



The alternative form is to write down equations 

LaTeX Math Block Reference
anchorPZ
 and 
LaTeX Math Block Reference
anchoruu
 in reservoir volume outside wellbore and match the solution to the fluid flux through the well-reservoir contact:

LaTeX Math Block
anchor

...

PZ1
alignmentleft
\phi \cdot c_t

...

 \cdot \partial_t p + \

...

nabla  {\bf u}  
+ 

...

c \cdot 

...

( {\bf u} \, \nabla p)
= 0
LaTeX Math Block
anchoruu1
alignmentleft
{\bf u} = - M \cdot ( \nabla 

...

p - 

...

\rho \

...

, {\

...

bf g})
LaTeX Math Block
anchorqk
alignmentleft
\int_{\Sigma_k} \, {\bf 

...

u} \

...

,  d {\

...

bf \Sigma} = 

...

q_k

...

(t)
LaTeX Math Block
anchorqGamma
alignmentleft
{\rm F}_{\Gamma}(p, {\bf 

...

u}

...

) = 0

where

LaTeX Math Inline
body

--uriencoded--\displaystyle \Psi(p) =2 \, \int_0%5ep \frac%7Bp \, dp%7D%7B\mu(p) \, Z(p)%7DPseudo-Pressure

\Sigma_k

well-reservoir contact of the 

LaTeX Math Inline
body

\mu(p)dynamic fluid viscosity

k
-th well

LaTeX Math Inline
body

Z(p)fluid compressibility factor

...

titleDerivation

--uriencoded--d %7B\bf \Sigma%7D

normal vector of differential area on the well-reservoir contact, pointing inside wellbore

LaTeX Math Inline
bodyq_k(t)

sandface flowrates at the 

LaTeX Math Inline
bodyk
-th well (could be injecting to or producing from the reservoir )

...

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...


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-linearLinear and Non-linear

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

...


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.

...

Fractured vertical well

...

...

Multifrac horizontal well

...

See also

...

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

[ Aquifer Drive Models ] [ Gas Cap Drive Models ]

[ Linear single-phase pressure diffusion @model ]