1) This paper focuses on estimating permeability in hydrocarbon reservoirs using the concept of hydraulic flow units (HFU), which considers geological and flow properties unlike traditional methods. 2) The researchers determined flow zone indicators and reservoir quality indexes from core measurements to identify HFUs using graphical and clustering methods. They estimated 6 HFUs for the studied carbonate reservoir in Iran. 3) Permeability was estimated for each HFU and showed good correlation with core measurements, performing better than the traditional porosity-permeability relationship. A neural network also accurately predicted properties in uncored wells.