Method of yielding oil residues or oil containing liquids from contaminated ground layers

A method of yielding oil residues or oil containing liquids from contaminated ground layers, comprising the steps of forming at least two adjacent bore holes in a contaminated ground region;

• producing connecting passages between said bore holes by loosening and partially rinsing out components of a ground material which surrounds said bore holes by directing a liquid in any of said bore holes;
• applying an underpressure in at least one of said bore holes for aspirating a liquid column upwardly in said at least one bore hole;
• supplying a fluid in at least another of said bore holes with maintaining a pressure difference between said bore holes;
• and in said at least one bore hole which is under underpressure, aspirating oil which is separated from the liquid column inside said one bore hole or an oil containing cover layer of the liquid column.