1. n. [Well Testing]

The simultaneous flow of both oil and free gas into a wellbore. This is thought to occur through common pore spaces, where the fluids flow simultaneously. In actuality, the situation is much more complicated, and much two-phase flow occurs in a stratified manner, with lighter fluids flowing primarily through the top of a producing zone and heavier ones flowing through the bottom layers.

See related terms: free gas,  relative permeability