Samira Emadi, SFB 1313 doctoral researcher at the Forschungszentrum Jülich (research project C05), will give her milestone presentation on "Non-invasive imaging of enzyme-induced calcite precipitation in porous media" on 3 February 2025.
Date: Monday, 3 February 2025
Time: 3 pm CET
Title: "Non-invasive imaging of enzyme-induced calcite precipitation in porous media"
Place: Online presentation. If you are interested in Samira Emadi's milestone presentation, please contact Samaneh Vahid Dastjerdi to receice the Webex link >>> samaneh.vahiddastjerdi@mechbau.uni-stuttgart.de
Abstract
Induced calcite precipitation, where CaCO3 closes voids inside porous media and unconsolidated samples are solidified, is an important technique in geotechnical engineering. To optimize these applications, it is crucial to understand how the dynamics of mineral precipitation affect flow and transport in porous media. The aim of this study is to investigate how different injection strategies affect the spatial and temporal development of calcite precipitation using time-lapse non-invasive imaging with magnetic resonance imaging (MRI) and X-ray microcomputed tomography (µXRCT).
We performed two distinct types of experiments to induce precipitation by simultaneous injection of a cementing solution consisting of 0.5 M CaCl2 and 0.5 M urea and an enzyme solution containing 5.0 g/l of Jack Bean meal into homogeneous sand packings prepared in 30 mm long sample cuvettes with a diameter of 15 mm. Two injection strategies were realized. In a first experiment, a constant flow rate of 0.01 mL/s was maintained during six injection cycles. Pressure development was monitored in parallel. In a second experiment, the solutions were injected at a constant pressure that was increased stepwise during six cycles from initially 50 mbar to 300 mbar to maintain moderate flow rates. Following each cycle, both samples were imaged using XRCT and MRI and the intrinsic permeability was determined.
Imaging results indicate that calcite preciptation occured more strongly close to the inlet, as manifested by water content and relaxation maps from MRI and density maps from XRCT. Only during the last two injection cycles, zones with increased precipitation became visible in the center of the column. The MRI relaxation maps suggest a reduction in pore size due to precipitation, which agreed with increased surface-to-volume ratio of the pores. Vertical porosity profiles derived from XRCT showed an average change of 12 and 11 vol.% for the constant flow and constant pressure inection strategies, respectively, and confirmed the non-uniform distribution observed with MRI. The permeability decreased by two orders of magnitude for both injection strategies.