Abstract:
The porosity contained in rocks is object of study by geoscientists due to the various genetic implications of these features. However, what have been motivating the search for new analytical techniques to study pores are the petrophysical analyses. The experimental techniques for porosity analysis, such as mercury or gas injection, allow a quantitative approach, but do not allow the visualization of the porous framework. Petrographic analysis by optical microscopy allows the visualization and quantification of intergranular pores, but it is restricted to the two-dimensional space and quantifications are less representative. Technological advances in X-ray computed microtomography (micro-CT) allowed three-dimensional analysis of pore geometry in microscale, in addition to automated volume measurements. The analyses of marble, quartzite, sandstone and dolomite breccia represented in this work and performed under the Project Falhas/PETROBRAS/UFPR, show the shape, size, connectivity, tortuosity, pore volume and distribution in these rocks, demonstrating the differences in the rocks’ porous frameworks. The integration of micro-CT to petrography allows the identification of mineral phases with attenuation of contrasting X-rays, placing the incidence of porosity in the mineralogical context in three dimensions, in addition to the contribution to the consistency of the method. Although the resolution is limited in the X-ray microtomograph that was used (the Skyscan model 1172), which does not reach the smallest pore size of some rocks, the integration of both techniques provides new information, of extreme importance for the research about micro-features related to the pores in rocks, helping in genetic interpretations and significantly contributing for the analyses of reservoirs.
Keywords:
X-ray computed microtomography; porosity; rocks