Drainage volume of a given well which can be formed in case a given well is working alone on the whole field (no interference with other wells).
It is going to be the same as Jointly drained volume of a group if all wells in a group are draining the same pack of reservoirs.
See Dynamic drainage volume in case a reservoir is shared by two or more producing or injecting wells.
See also
Physics / Fluid Dynamics / Percolation
Petroleum Industry / Upstream / Subsurface E&P Disciplines / Field Study & Modelling / Drainage (fluid flow)