Crude Oil is delivered out of the reservoir together with saline formation water, gas and solids; therefore, it has to be separated from the associated materials in a subsequent oil treatment. The formation water, which is accumulated at this production step, often has to be re-injected into the reservoir, as a discharge into surface water is not possible because of the contained harmful substances and the high salinity. Furthermore, the reduction in formation pressure due to producing fluids should be counteracted by injecting the produced water again as well as the recovery ratio of production should be increased through a well-directed displacement of crude oil to the production well. Due to the fact that the formation water passes through different temperature and pressure steps along its way from production well to injection well, different precipitations are formed. These depositions are mainly iron sulfide as well as various carbonate and sulfate precipitations, also known as Scale, which lead together with the solids that are contained in the formation water to problems during the re-injection into the reservoir as well as to deposits in the piping. In order to reduce, respectively prevent, these precipitations, the application of chemicals is a promising approach; therefore, the application of chelating agents is examined technically and economically in this thesis on basis of already available results in literature as well as laboratory experiments. Special attention is paid to the efficiency and compatibility of the chemicals with reservoir rock as well as the already existing materials and oilfield chemicals in the system of the field-network Voitsdorf of Rohöl-Aufsuchungs AG. While on basis of information found in the literature, the chelating agents HEDTA and THPS showed good performance to prevent precipitations, the various EDTA-compounds were convincing in the laboratory tests. By means of the laboratory experiments and already executed field tests, it was found out that a continuous addition of average concentration of the chelating agent after the oil treatment into the system would be most promising; however, further field tests have to be carried out to verify these results.