Multi-scale X-ray tomography analysis of carbonate porosity

Abstract: The porosity (from values of,1 % up to more than 50%, with a mean value of 36.5%) and permeability (from very low values to 20.4 D, with a mean value around 800 mD) of 38 plugs, with a diameter 40 mm, have been measured. These plugs were taken approximately every 1.5 m along a 100 m-long core, sampling a series of reefal carbonate platform lithofacies. A non-unique relationship between porosity and permeability is obtained. In addition, the porosity was measured from processing X-ray micro-tomography images with resolutions ranging from 0.42 to 190.0 mm and sampling volumes ranging from less than 1 mm3 to few cm3. Depending on the structure of the pore network, the computed porosity is, in some cases, controlled by the X-ray image resolu-tion and the sampled volume. While high resolution is required to image micro-porous mate-rial, large samples with lower resolution images are necessary for identifying distributed vugs and millimetre-scale structures. This study shows that multi-resolution X-ray micro-tomography is an effective tool for characterizing the multi-scale pore structure of carbonate rocks and under-standing how it may control key petrophysical parameters such as porosity and permeability. Carbonate reservoirs are known to be heterogene-ous over a wide range of scales. The heterogeneit