An innovative approach to permeability estimation of the fractured-vuggy carbonate reservoirs based on 2D images

Permeability analysis is an essential process in reservoir characterization, especially when evaluating those highly heterogeneous reservoirs such as fractures-vuggy carbonate reservoirs. Because of the biased sampling, no laboratory measurement can obtain the exact permeability values of the carbonate samples that contain fractures or large vugs. Besides this fact, the heterogeneity of the secondary pore distribution could cause unstable test results of permeability, which can bring out significant uncertainty in reservoir modeling if the problem is ignored. There are two widely used indirect methods for permeability estimation: one is based on the Kozeny-Carman equation, and the other one is based on the Navier-Stokes equations. Both two estimations need to evaluate the geometry properties of the rock pore-fracture system, which will introduce artificial uncertainty into the estimation results. This paper proposed an innovative approach to permeability estimation established through counting the pores, fractures, and vugs on 2D images. By considering the area distribution of those porous objects identified on the 2D images in a specified statistical interval, the absolute permeability values of the fractured-vuggy carbonate will be calculated directly without any artificial influence. The new approach is a general way to estimate permeability and does not consider rock facies and pore types. The estimation results show a more stable manner than core analysis data, which could help to select permeability values in reservoir modeling. On the other hand, by comparing the estimation results from different statistical intervals, the heterogeneity of the parameter is revealed.

Automated summary

Permeability analysis is crucial for highly heterogeneous reservoirs like fractures-vuggy carbonate reservoirs, as traditional laboratory measurements may not accurately capture the permeability values of such samples. This research proposed an innovative approach for permeability estimation based on 2D image analysis of pores, fractures, and vugs, which allows for direct calculation of absolute permeability values with more stability than core analysis data, aiding in the selection of permeability values for reservoir modeling. Comparing estimation results from different statistical intervals can reveal the heterogeneity of the parameter.