The importance of polymeric transportation systems has been steadily increasing over the past years. Polymer pipes offer distinct advantages over metal transportation lines regarding corrosion and abrasion resistance, beneficial mechanical strength to weight ratio, and lower life cycle costs. One particular aspect of polymer pipes in onshore oilfield applications is the requirement of a high permeation resistance against low-molecular-weight hydrocarbons. The present work reports experiments on influencing factors on the permeation process of aromatic and aliphatic substances. The permeation rate mainly depends on the structure and size of the permeant, the concentration of the substances and the temperature. A new measuring method has been developed to investigate the permeation of individual hydrocarbons which are components of crude oil. The permeation of the low-molecular-weight hydrocarbons has been evaluated using conventional testing methods (gravimetric analyses) and has been compared against a newly developed measuring system using gas chromatographic detection techniques. Further on, the accumulation of the volatile organic substances in water has been studied with a developed experimental set-up. Governmental limits regarding the hydrocarbon concentration in potable water have been exceeded by a greater margin due to the permeation of the low molecular weight substances. As a consequence, a modification of the polyolefin is required to use polyethylene pipes in oilfield applications. By means of cross-linking of the polymeric material (by chemical cross-linking with organosilanes or irradiation with high-energy electrons) the barrier properties of polyethylene have been increased and a reduction of the permeation of linear alkanes has been achieved.