In majority of practical well tests the pressure diffusion in multi-phase segregation of reservoir flow the pressure response can be approximated by single-phase pressure diffusion model with a specific from of fluid/reservoir properties.
This approximation can be done in one of three ways:
| Non-linear multi-phase diffusion | the most generic way |
| Linear Perrine multi-phase diffusion | the simplest multi-phase model |
| Pseudo-linear multi-phase diffusion |