Explanation of Diffusivity Equation

[Muhammad Khurram Adil]

Hello, Assalam-o-Alikum

Someone Kindly Explain me the importance of Diffusivity Equation (especially radial and Spherical Flow). its usage, assumptions and limitations!.....

Thankyou! Timely response will be very beneficial!

[06pg22]

Walaikum Salam,

Diffusivity equation is the base of Pressure Transient Analysis and Reservoir Simulation.
It is derived from Darcy Equation, Equation of State and Material Balance equation. So it has the same underlying assumptions that are common among aforementioned 3 equations.
Its analytical solution led to Pressure Transient Analysis equations while numerical solution led to Reservoir Simulation equations.

[vinomarky]

Its actually derived from the continuity equation (essentially material balance) along with Ficks first law.

Darcy equation and EOS etc are then layered on top to create the equations required for numerical modeling