Due to the declining oil rates in brown fields, a common strategy to reach the annual oil production at OMV Austria is to increase the gross production rates in wells with good inflow. The results of such gross rate increases differ. In some cases a wells water cut drops while in others it raises. The third observed behaviour is a constant water cut trend without showing reactions on the rate increase. This master thesis identifies the reasons for the different production profiles and water cut reactions and shows, that a gross rate increase, beside a faster oil production, improves the vertical sweep efficiency leading to a higher oil recovery factor. The improvement of vertical sweep is due to a combination of several factors from which the permeability distribution represents the deciding one.The rating of success for a wells gross increase and the analyzing methods are based on the WOR behaviour. By the application of the WOR Recovery Plot, a new success rating approach was introduced and the wells were classified according to their WOR behaviour before and after the rate increase. The higher vertical sweep efficiency is achieved by the improvement of the velocity profile due to the gross rate increase as result of a favourable permeability distribution and a reduction of the residual oil saturation.