In this pattern, the reactive fluid was consumed over small parts of the mineral surface area leading to the formation of a few highly conductive flow channels, i.e. In contrary to the observation on the oolitic sample, visual observations of the images of the second sample reveal a different dissolution pattern which is called conical wormhole dissolution pattern. Side-view registered slices of the oolitic sample in (top) pre-dissolution and (bottom) post-dissolution states, at different positions.įigures 3 and 4 illustrate examples of registered slices of the wackestone-packstone sample from top and side views, respectively. The slices are at different distances to the front (injection face) of the samples: (left) 6.42 mm, (middle) 9.50 mm, and (right) 11.55 mm.įigure 2. (Top) pre-dissolution micro-CT slices of the oolitic sample (Bottom) the corresponding registered post-dissolution images. This pattern belongs to local non-equilibrium dissolution category in which there is no sharp interface between the reactive fluid zone and the porous medium.įigure 1. Visual observations of the images clearly illustrate that the reactive fluid locally increased the pore diameters across most parts of the sample and hence led to a quasi-uniform dissolution pattern. Hence, in monomineralic rock, such as the samples studied in this paper, micro-CT images are 3D porosity maps.įigures 1 and 2 show examples of registered slices of the oolitic sample from top and side views, respectively. In the micro-CT image, the grey-scale values of the pixels correspond to the density and composition of the material imaged.
![the creative flow ct the creative flow ct](https://www.frontiersin.org/files/Articles/416995/fpsyg-10-00137-HTML/image_m/fpsyg-10-00137-g001.jpg)
#THE CREATIVE FLOW CT REGISTRATION#
The post-dissolution image was superposed to the pre-dissolution image using a 3D registration technique developed by Latham, et al. The pre- and post-dissolution dry samples were imaged using a high resolution micro-CT scanner at the Australian National University (ANU) with at least 8.5×8.5×8.5 mm field of view and resolutions of less than 5 µm. Details of the experimental procedure were described in. The experiments were performed at ambient conditions and were terminated after significant changes occurred in the cores as indicated by the pressure transducers. Dissolution experiments were conducted in core plugs of 7 mm diameter using ethylenediaminetetraacetic acid (EDTA) solution at pH 12 as the reactive fluid. The first sample was an oolitic limestone with multi-modal pore size distribution, while the second one was a wackestone-packstone carbonate with a bimodal pore size. In this work, two carbonate core samples were considered for the dissolution experiments. Among them, X-ray micro-computed tomography (micro-CT) is a superior non-destructive imaging method which can create high-resolution images with large field of view. Ī number of imaging techniques such as Wood’s metal casting, neutron radiography and scanning electron microscopy have been used to study the dissolution patterns.
![the creative flow ct the creative flow ct](https://cyberleninka.org/viewer_images/422950/f/1.png)
Several studies have revealed a variety of dissolution patterns from face dissolution to uniform dissolution depending on the injection rate and fluid/mineral properties. Natural heterogeneity of the porous rocks for the case of rapid dissolution of the mineral by the reactant fluid results in localization of the flow path and the formation of highly conductive channels called wormholes. At the pore-scale, the dissolution mechanism consists of mass transport of the reactant by diffusion and advection to the solid surface, chemical reaction at the fluid-mineral interface, and the product mass transport away from the surface. The evolution of rock microstructure is a result of complex interactions between the rock surface and reactive fluids and depends on the thermodynamic conditions, the rock and fluid composition and the flow regime.