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Petroleum is, at present, still the main energy source in the world. Most of it is stored in carbonate rock reservoirs with complex inner structures and pores ranging from nanometers to dozens of meters. Knowing the rock's entire pore network is indispensable to perform an effective petroleum extraction. X-ray microtomography, a technique that generates images from samples' inner structure and a powerful tool to evaluate the 3D pore network, was employed in this scientific research to scan four kinds of carbonate rocks (Dolomite, Desert Pink, Indiana, and Winterset) in five different pore scales (90 µm, 13 µm, 5.5 µm, 1.0 µm, and 65 nm). A multi-scale approach based on the number of pores was applied to integrate different pore scale data and assess the total porosity as well as each sample pore size distribution. The results were compared to classical Mercury Injection Capillary Pressure (MICP) results, demonstrating a fair agreement in total porosity in the two samples. Multi-scale porosity of the Dolomite sample was 17.7% against (18.9 ± 2.1)% of the MICP porosity. The Winterset sample had multi-scale porosity of 26.2%, while MICP porosity was (31.2 ± 0.6)%. Pore size distribution results were rather satisfactory, especially when overlapping regions in different scales were compared. In general, the multi-scale approach showed good potential. It still needs further evaluation to fine-tune some procedures and fluid flow simulation tests but might become a useful tool to study reservoir rocks with a wide range of pore sizes, such as carbonate rocks.

In the study of pore size distributions within microtomographic images, there is no consensus in how to group pore size distributions obtained at different spatial resolutions in a single distribution, which represents the properties of the sample in a better way. This work presents a proposition that allows to group pore size distributions obtained by microtomography images in different spatial resolutions. A Shark's Bay oolite was imaged by X-ray microtomography at 4.4μm and 1.1μm spatial resolutions. The pore size distribution and average porosity were determined for each resolution. Through a weight factor obtained from the number of pores measured on those distributions, it is possible to group the pore size distributions in a single distribution. Using the pore size distribution for the grouped function, the average porosity of the sample was determined, which was then compared to the total porosity measured by mercury porosimetry, showing that this distribution characterizes the sample in a more representative way.

Este trabalho propõe um novo modelo para compor as escalas da rede porosa de rochas carbonáticas. Quatro amostras (Desert Pink, Dolomite, Indiana e Winterset) foram medidas pela microtomografia de raios X com diferentes resoluções espaciais (90 μm, 13 μm, 5 μm, ~1 μm, 65 nm). Os resultados das medidas foram utilizados para calcular a porosidade total e a distribuição de tamanhos de poros das amostras. O modelo usa esses resultados para determinar o número de objetos (e seus tamanhos) medidos em cada escala e os projeta para o maior volume utilizado, permitindo que seja feita uma comparação direta dos resultados. Os resultados de porosidade calculados pelo modelo multiescala foram comparados com resultados obtidos pela técnica de porosimetria por injeção de mercúrio, mostrando boa concordância para duas das quatro amostras. Também foi apresentada uma nova abordagem, baseada no modelo multiescala proposto, para determinar se subvolumes das imagens microtomográficas eram representativos para o volume total. Os subvolumes considerados representativos foram utilizados no modelo multiescala gerando bons resultados. This work proposes a new model to compose the different scales of carbonate rocks’ pore network. Four samples (Desert Pink, Dolomite, Indiana and Winterset) were measured by X-ray microtomogaphy using different spatial resolutions (90 μm, 13 μm, 5 μm, ~1 μm, 65 nm). The results were used to calculate the samples total porosity and pore size distribution. The model used these results to calculate the number of objects (and their size) measured in each scale and project them to the larger volume used, allowing a direct comparison among them. The calculated porosity results were compared to results obtained by mercury injection capillary pressure, showing good agreement to two of the four samples. A new approach, based in the proposed multiscale model, to determine if subvolumes of microtomographic images are representative to the whole volume was also presented. The subvolumes found representative were used in the multiscale model bringing good results.

Carbonate rocks store more than 50% of world's petroleum. These rocks' structures are highly complex and vary depending on many factors regarding their formation, e.g., lithification and diagenesis. In order to perform an effective extraction of petroleum it is necessary to know petrophysical parameters, such as total porosity, pore size and permeability of the reservoir rocks. Carbonate rocks usually have a range of pore sizes that goes from nanometers to meters or even dozen of meters. The nanopores and micropores might play an important role in the pores connectivity of carbonate rocks. X-ray computed tomography (CT) has been widely used to analyze petrophysical parameters in recent years. This technique has the capability to generate 2D images of the samples' inner structure and also allows the 3D reconstruction of the actual analyzed volume. CT is a powerful technique, but its results depend on the spatial resolution of the generated image. Spatial resolution is a measurement parameter that indicates...

The porous systems of reservoir rocks present a complex geometry, involving aspects of shape of pores (morphology) and connectivity between the pores (topology). The macroscopic physical properties of these materials are strongly dependent of their microstructures. Based on these aspects, the present study has as main objective the characterization of the porous system geometry and computational determination of petrophysics properties of carbonate reservoir rocks through the X-ray microtomography methodology. Samples were microtomographed with the microtomographs Skyscan model 1172, installed at the PETROBRAS Research and Development Center (CENPES), Rio de Janeiro-RJ, Brazil and model 1173, installed at Sedimentary Geology Laboratory (LAGESD) in the Federal University of Rio de Janeiro (UFRJ). Two samples of carbonates were measured, Travertine and Dolomite, with spatial resolutions of 7 μm and 9.8 μm and 1.3 μm, 7 μm and 17 μm, respectively for the travertine and dolomite. With the data collected in the acquisitions, 900 transversal sections were reconstructed for each one of the referred resolutions. For the sample of dolomite, the average porosity found was 21.64%, 20.92% and 15.97% for resolutions of 1.3 μm, 7 μm and 17 μm, respectively. For the sample of travertine, the average porosity was 7.80 % and 7.52 % for resolutions of 7 μm and 9.8 μm, respectively. For the sample of dolomite, the pore size distribution showed that 50 % of the porous phase has pores with radius up to 37.6 μm, 84.6 μm and 84.4 μm, for the spatial resolutions of 1.3 μm, 7 μm and 17 μm, respectively. For the sample of travertine, 50 % of the pores have radius up to 148.1 μm and 158.1 μm, for the spatial resolutions of 7 μm and 9.8 μm.

Binarization process plays an important role in structural characterization by means of micro-CT images analysis. The choice of the correct threshold to separate porous phase from the material is the procedure for binary images creation. Slight variations of the threshold level led to substantial variations in physical parameters determination. The aim of this work is to evaluate these variations based on manual threshold settings data of five operators. Porosity and pore size distribution of a sandstone sample were determined.

X‐rays microtomography is a non‐destructive technique that generates digital images of samples’ internal structure by attenuation of an X‐rays beam. The samples’ structural parameters are obtained from these images by specific software analysis. This means that the image quality is essential to perform a suitable structural characterization. The spatial resolution is one of the main parameters that contribute to image quality. In this work the influence of spatial resolution for industrial SiC ceramic foam’s analysis was evaluated. The samples’ pore density was 60 pores per inch (ppi). This kind of foam can operate at high temperatures, which allow them to be used as liquid metal filters, heat exchangers or composite of rocket nozzles, for example. The measurements were performed with a SkyScan microtomograph, model 1172. It was operated at 50 kV and 60 kV high voltage for measurements with 24.8 μm and 2.5 μm spatial resolution, respectively. The total porosity and the pore size distribution were the stru...

X‐ray microtomography is a non‐destructive imaging technique. It consists in cross‐sections object reconstruction based in the linear attenuation coefficient maps achieved through the object illuminating by a X‐ray beam at different angular positions. It has been used by various researches to supply microstructural informations of materials as ceramic filters, pills, titanium prosthesis and reservoir rocks. An item of great interest has been the characterization of the liquid phase presence in porous space. This paper shows the X‐ray microtomography methodology employed to achieve qualitative and quantitative results about Botucatu sandstones wetting. It was used a Skyscan, 1172 model, which employs an X‐ray tube with W anode and a cone beam. This laboratory based equipment is able to provide images of until 1 μm spatial resolution. The employed samples were two cores of layered Botucatu sandstone, named ARN1 and ARN 2. These samples were scanned in two situations each one, dried and wet. 2D images, poros...

Espumas cerâmicas são amplamente utilizadas nas indústrias siderúrgica e aeroespacial. O conhecimento da estrutura interna desse material é extremamente importante para que seu uso seja realizado de forma adequada. Neste trabalho a estrutura interna de espumas industriais de carbeto de silício de densidades de poros de 30 ppi, 45, ppi, 60 ppi, 80 ppi e 100 ppi foram analisadas através das técnicas de transmissão de raios gama e microtomografia de raios-X. Essas técnicas têm a vantagem de não perturbar as amostras, permitindo que medidas posteriores sejam realizadas. O aparato de transmissão de raios gama utilizado é composto por uma fonte 241Am (cujo pico de energia utilizado foi de 59,54 keV) com atividade de 100 mCi, uma mesa micrométrica de movimentação horizontal e vertical e um detector de iodeto de sódio dopado com tálio (NaI(Tl)). As medidas microtomográficas, realizadas em duas resoluções diferentes (24,8 and 2,5 ), foram feitas com o microtomógrafo Skyscan 1172. Através da técnica de transmissão de raios gama os perfis de porosidade dentro da amostra foram medidos e foi determinada a porosidade total da mesma. As imagens obtidas pela técnica de microtomografia de raios-X permitiram avaliar a influência do limiar de binarização nos resultados de porosidade total das amostras. Também foram determinadas a porosidade total das amostras e as distribuições de tamanhos de poros e de tamanhos das paredes das células. Os resultados mostraram boa concordância com a literatura. Os valores obtidos também foram comparados entre as duas resoluções espaciais empregadas e mostraram a importância da resolução para a determinação dos parâmetros estruturais. Ceramic foams are widely used in metallurgical and aerospacial industries. The knowledge of this material’s internal structure is very important for its appropriate use. This research examines the internal structure of silicon carbide industrial foams with pore densities of 30 ppi, 45 ppi, 60 ppi, 80 ppi and 100 ppi by gamma-ray transmission and X-ray microtomography techniques. These techniques have the advantage of not disturbing the sample, thereby allowing new measurements to be performed. The gamma-rays transmission apparatus used for the research is composed of a 241Am radiation source (whose used energy peak is 59,54 keV) with 100 mCi activity, a table with micrometric horizontal and vertical movement and a NaI(Tl) detector. The microtomographic measurements, performed on two different resolutions (24,8 and 2,5 ), were carried out with a Skyscan 1172 microtomograph. Through the gamma-rays transmission technique, the profiles of samples’ porosity was plotted and the samples’ total porosity were determined. The images obtained by X-ray microtomography technique allowed for the evaluation of the influence of the binarization threshold in the samples’ total porosity results. The samples’ total porosity, pore size distribution, and cell thickness distribution was determined, too. The results were in good agreement with the literature. The obtained results of the two spatial resolutions used were compared, as well. These showed the importance of the resolution for the determination of structural parameters.