5:15 PM - 6:45 PM
[HCG20-P06] In-situ sealing experiment in high permeable aquifer using ‘synthetic concretion-forming resin’
Keywords:synthetic concretion-forming resin, high permeable aquifer, calcium carbonite, sealing
Spherical calcium carbonate (CaCO3) concretions observed in sedimentary rocks are characterized by their rounded shapes and distinct sharp boundaries. Well-preserved fossils are often found and the formation process has been explained by diffusion and development of rapid syn-depositional reaction front due to the supersaturated precipitation reaction, from their centers towards their outer margins. In particular, CaCO3 concretion highly reduced permeability owing to cementation and sealing by calcite. Laboratory permeability tests of those concretions show that the hydraulic conductivity value (ca. order of 10-12 ~ -9 m/s) is two to three orders of magnitude lower than that of the host rock. Also, the hardness value (HL) measured by the Equotip hardness tester indicates predominantly higher (almost equal to the hardness of igneous rocks) in the concretion than in the host rock. Due to this, fossils contained inside are well preserved by restriction of water penetration from outside the concretion, after rapid concretion formation. This sealing property can provide strong resistance to weathering in the natural environment for more than a million years.
By learning a robust sealing analogue, we have succeeded in developing “synthetic concretion-forming resin”. To test the effectiveness of the resin for sealing groundwater flow paths, we are conducting an in-situ experiment using several shallow wells drilled into an aquifer consisting of very high permeable sand and gravel formation at about 10-12mbGL. The experiment showed a decrease in permeability to 1/10 in two weeks. This sealing process can be applied to an underground facility for the geological disposal of nuclear wastes. In addition, we will continue hydraulic tests for permeability changes over time, and seismic surveys will also try to visualize the growth process of the concretions.
By learning a robust sealing analogue, we have succeeded in developing “synthetic concretion-forming resin”. To test the effectiveness of the resin for sealing groundwater flow paths, we are conducting an in-situ experiment using several shallow wells drilled into an aquifer consisting of very high permeable sand and gravel formation at about 10-12mbGL. The experiment showed a decrease in permeability to 1/10 in two weeks. This sealing process can be applied to an underground facility for the geological disposal of nuclear wastes. In addition, we will continue hydraulic tests for permeability changes over time, and seismic surveys will also try to visualize the growth process of the concretions.