Determination of Principal Permeability Directions in Reservoir Rocks from Micro-CT Data

Abstract

The routine measurement of direction-dependent reservoir rock properties like permeability often takes place along the axial direction of core samples. As permeability is a tensor property of porous materials, it should be fully described by a tensor matrix or by three main permeabilities in principal directions. Due to compaction, cementation, and other lithification processes, which take place after sedimentation, or later distortion and fractionation of the regional earth's crust, the axial direction of core samples, may not be always one of the main permeability directions. In this paper, a computational technique to find principal permeability directions from micro-CT images of core samples was developed by us. Moreover, an assumed cube inside the core sample data with dimensions small enough to be able to imaginarily rotate inside the core limits has been chosen by us. Also, connected pore network was extracted from micro-CT data, and permeability was calculated in all space directions. In addition, stepwise rotation process continued until all possible space directions were covered. Then calculated permeabilities from all directions have been compared with each other by us. Afterwards, maximum and minimum values have been found by us. In this paper, two micro-CT datasets, which were taken from the Imperial College website, are used. Finally, the obtained results showed that the direction of maximum permeability within the carbonate core sample is about 30° deviation from the axial core direction. In addition to the main direction, the proposed computational technique can be effectively used to describe the permeability tensor of the reservoir rocks.