Due to the laboratory investigations, new experimental data allow to make a conclusion about the heterogeneity of fluid properties on Vankor deposit. It is not possible to reveal any trends if the traditional formation testers are used. The sampling process of fluid with modular subsurface formation tester of samples allows to control the formation fluid flow to the tester by optical analyzers, thus, the downhole quality control is provided. The consequent laboratory investigations show the natural trend of gas solubility and other oil properties along the formation.