The ground base was evaluated and analysed by using biological index and variation of population of benthon which are effected by bottom water and mud environment.
Specific materials are available for all types of water - and oil-basemud systems and are evaluated in static filtration tests or in various dynamic filtration tests.
The measurement results showed that the invasion of the filtrates of oil-basemud and water-basemud has a considerable effect on oil phase permeability.