Investigation of porosity and permeability effects from microstructure changes during limestone dissolution

Abstract

[1] We studied experimentally the dissolution of a porous limestone core during CO 2 -enriched water injection. We measured the changes in porosity and permeability arising from modifications of the pore network geometry and the fluid-rock interface. A methodology based on periodic X-ray microtomography imaging was implemented to record the evolution of the time-and scale-dependent microstructures with a spatial resolution of 4.91 mm. Two processes were successively involved in the rapid permeability increase of the sample, as documented from microscale to core-scale measurements. First, the microcrystalline phase was partially dissolved, associated with displacement of mineral particles. During this process, the exponent n of the power law k $ f n decreased continuously. Secondly the sparitic phase dissolved, accompanied by a decrease of the pore wall roughness and an increase of the pore connectivity. This second period was characterized by a constant value of n. The reactive surface decreased noticeably during the transition from the microcrystalline to the sparitic dissolution periods, whereas the effective porosity increased strongly.

Upscaling calcium carbonate precipitation rates from pore to continuum scale

“…By using an appropriate image processing procedure, it is possible to distinguish the different materials (e.g air, glass beads, and calcite) and accurately quantify parameters characterizing the sample geometry, i.e. porosity distribution, pore connectivity as well as geometric surface-area of the fluid-rock interface (Noiriel et al [2004], Noiriel et al [2005]). Each of these parameters is based on averaging of a single 4.46 micron slice through the column.…”

3D Quantification of Pore Scale Geometrical Changes Using Synchrotron Computed

“…Before and after those percolation stages, the sample is removed from the cell and imaged by X-Ray microtomography. Precise description of the experiment can be found in Noiriel et al (2004 and, here we will only consider the treatments necessary to quantitatively characterize the four 3D images obtained from microtomographic acquisitions: initial state, state 1 (after the first percolation stage, 1 h 24 min), state 2 (after the second percolation stage, 12 h 30 min), and state 3 (after the third percolation stage, 8 h 30 min).…”

“…The use of microtomography in material science thus requires that the studied material presents differences of internal absorption, which can be measured within the studied volume elements (voxel). This technique is thus well adapted to multimaterials or porous materials that evolve according to external conditions; examples are glass sintering (Bernard et al, 2005a), pressure solution in rocks (Renard et al, 2004), dissolution by reactive percolation (Noiriel et al, 2004), mortar leaching (Burlion et al, 2005), transport in semi-solid alloys (Bernard et al, 2005b) or composites damage evolution (Babout et al, 2001).…”

“…X-ray microtomography has been used to follow the evolution of the core micro-geometry in details. Preliminary results have been presented elsewhere (Noiriel et al, 2004;Noiriel et al, 2005) and we want here to describe more precisely the way microtomographic data treatments have been conducted. The project is still in progress and improvements in the methods that are necessary will be discussed.…”

Quantifying fracture geometry with X-ray tomography: Technique of Iterative Local Thresholding (TILT) for 3D image segmentation

“…xCT imaging has been used to provide valuable insights in core-flow experiments designed to investigate fractures in the context of geohydrological, geochemical, and geomechanical processes of the deep subsurface, such as CO 2 geological storage [20,30,40] and oil and gas operations [13-15, 17, 41-46]. Quantitative characterizations of fracture geometries have advanced our understanding of fracture hydrodynamics [13,17,21,[47][48][49], reactivity [11,24,25,35,36,47,[50][51][52][53], and mechanics [16,19,37].…”