Whole core analysis, which provides characteristics on a larger scale closer to that of the reservoir, is particularly important for heterogeneous formations such as vuggy carbonate or fractured rocks. Consequently, the authors previously developed an X-ray CT based method to numerically analyze fluid flows through fractured rock cores. This method provides a 3D fracture aperture distribution of a fractured rock, which can be utilized to analyze fluid flow within the rock, with a local cubic law-based fracture flow model simulation. The numerical models of fractured rock and fluid flow, respectively, can reproduce experimentally determined porosity and permeability, and therefore can provide realistic fracture flow characteristics. In the present study, a new X-ray CT based method to numerically analyze fluid flows through vuggy carbonate rock cores has been developed, and has been applied to different types of vuggy carbonate rock core samples. 3D distributions of CT number of the samples, which consists of 0.4-mm cubic voxels, are converted into 3D porosity distributions, using the partial volume effect (i.e., a linear relationship between CT number and porosity). The porosity distributions can reproduce experimentally determined porosities within factors of approximately 1.1–1.4. To simulate Darcy flow in the samples, 3D permeability distributions are obtained by assuming that the permeability-porosity relation of non-vuggy carbonate rocks is valid locally within a vuggy carbonate rock. As a result of a fluid flow simulation, experimentally determined permeabilities, which show large differences among the samples, are reproduced within factors of 1.6–3.6, and heterogeneous fluid flows (i.e, channeling flows) within the samples.

This content is only available via PDF.
You can access this article if you purchase or spend a download.