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

\phi \cdot c_t \cdot \partial_t p + \nabla  {\bf u}  
= \sum_k q_k(t) \cdot \delta({\bf r}-{\bf r}_k)
{\bf u} = - M \cdot ( \nabla p - \rho \, {\bf g})
\int_{\Gamma} \, {\bf u} \,  d {\bf \Sigma} = q_\Gamma(t)


or
\phi \cdot c_t \cdot \partial_t p + \nabla  {\bf u}  = 0
{\bf u} = - M \cdot ( \nabla p - \rho \, {\bf g})
\int_{\Sigma_k} \, {\bf u} \,  d {\bf \Sigma} = q_k(t)
\int_{\Gamma} \, {\bf u} \,  d {\bf \Sigma} = q_\Gamma(t)

where

reservoir pressure

time

fluid density 

position vector

effective porosity 

position vector of the -th source

total compressibility 

Dirac delta function

gradient operator

formation permeability to a given fluid

gravity vector

dynamic viscosity of a given  fluid

fluid velocity under Darcy flow 

sandface flowrates of the -th source

reservoir boundary

flow through the reservoir boundary , which is  aquifer or gas cap



Derivation of linear single-phase 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 / Single-phase pressure diffusion @model