Construction of Reliable Flow Simulation Domain and Estimation of Permeability Based on Nuclear Magnetic Resonance and 3D X-ray Computed Tomography for Reservoir Carbonate Rocks

Due to the heterogeneity of carbonate rocks, some small pores partially undertaking flows are unresolved in X-ray CT images, therefore have been not appropriately considered in direct flow simulation. By the data fusion of two non-destructive measurements from X-ray CT imaging and nuclear magnetic resonance measurement, this study proposes the construction of ternary-phase domain including resolved apparent-pore, unresolved gray-pore, and resolved solid voxels. Gray-pore voxel containing the unresolved pore is characterized as a microporous structure with equivalent local hydraulic properties according to CT number and pore size distribution. From X-ray CT images of reservoir carbonate rocks from Abu Dhabi, ternary-phase domains are constructed consistently to figure out local and overall flow behaviors despite the different image resolutions. Stokes–Brinkman flow simulation shows that although some apparent-pore volumes are disconnected from each other due to limited resolution, fluid flow can be passed by the gray-pore region. Additionally, a modified hydraulic tortuosity model is proposed to evaluate the tortuosity of the ternary-phase domain because the conventional hydraulic tortuosity model for the binary-phase domain underestimates the tortuosity of the ternary-phase domain.