Research paperPermeability estimation based on thin-section image analysis and 2D flow modeling in grain-dominated carbonates

- K2D/K3D is evaluated based on Kozney-Carman equation.
- K2D is obtained through flow simulation on 2D thin section image.
- K2D/K3D is quantified through thin section analysis.
- A fast but reliable method is established for permeability estimation for grain-dominated carbonates.

Permeability estimation based on image analysis is a good alternative when an intact core-plug is not available for laboratory measurement. While there is much research on permeability estimation from 2D and 3D images or models, accurately estimating permeability for carbonates, a type of rock with substantial heterogeneity, is still challenging. In this study, a method for permeability estimation based on thin-section image analysis and 2D permeability simulation is developed for grain-dominated carbonates based on semi-theoretical analysis of 2D and 3D permeability (K2D and K3D) relationship. The mathematical expression of the K2D/K3D is examined and validated with a grainstone carbonate sample, for which both K2D and K3D were obtained through permeability simulation based on micro-CT images. The method was applied to 24 grain-dominated carbonate samples collected from different locations with a large variation in rock textures and fabrics and a broad range of permeability from 0.1 mD to 3200 mD. Representativeness of the thin section and the correct determination of the effective pores are the key for accurate estimation. The estimated permeability was compared to the measured value, and 92% of the results are within a factor of ±5, and 46% are with a factor of ±2. Potential sources of systematic error are discussed both qualitatively and quantitatively.