Jaquiel S. Fernandes

Effects of manual threshold setting on image analysis results of a sandstone sample structural characterization by X-ray microtomography.

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.

Influence of Spatial Resolution on SiC Industrial Foam’s Structural Parameters Obtained by X‐ray Microtomography

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...

Accuracy evaluation of an X-ray microtomography system.

Microstructural parameter evaluation of reservoir rocks is of great importance to petroleum production companies. In this connection, X-ray computed microtomography (μ-CT) has proven to be a quite useful method for the assessment of rocks, as it provides important microstructural parameters, such as porosity, permeability, pore size distribution and porous phase of the sample. X-ray computed microtomography is a non-destructive technique that enables the reuse of samples already measured and also yields 2-D cross-sectional images of the sample as well as volume rendering. This technique offers an additional advantage, as it does not require sample preparation, of reducing the measurement time, which is approximately one to three hours, depending on the spatial resolution used. Although this technique is extensively used, accuracy verification of measurements is hard to obtain because the existing calibrated samples (phantoms) have large volumes and are assessed in medical CT scanners with millimeter spatial resolution. Accordingly, this study aims to determine the accuracy of an X-ray computed microtomography system using a Skyscan 1172 X-ray microtomograph. To accomplish this investigation, it was used a nylon thread set with known appropriate diameter inserted into a glass tube. The results for porosity size and phase distribution by X-ray microtomography were very close to the geometrically calculated values. The geometrically calculated porosity and the porosity determined by the methodology using the μ-CT was 33.4±3.4% and 31.0±0.3%, respectively. The outcome of this investigation was excellent. It was also observed a small variability in the results along all 401 sections of the analyzed image. Minimum and maximum porosity values between the cross sections were 30.9% and 31.1%, respectively. A 3-D image representing the actual structure of the sample was also rendered from the 2-D images.

Multi-scale analysis in carbonates by X-ray microtomography: Characterization of the porosity and pore size distribution

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.

Investigation of Sandstones Wetting by X‐ray Microtomography

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...