14-17 May 2018
New Orleans
US/Central timezone

Pore space sealing using microbially mediated calcite precipitation: a lab to field scale study

16 May 2018, 16:34
15m
New Orleans

New Orleans

Oral 20 Minutes MS 4.05: Biochemical mineral precipitation for subsurface applications Parallel 8-A

Speaker

Dr Dominique J. Tobler (Nano-Science Center, Department of Chemistry, University of Copenhagen, Denmark)

Description

Microbially driven calcite precipitation (via ureolysis) has shown great potential in a wide range of applications, including solid-phase capture, concrete crack remediation, soil stabilisation and carbon sequestration. Here, this process is investigated as a means of reducing the primary porosity and/or secondary fracture porosity of host rocks surrounding nuclear waste repositories in order to control or prevent radionuclide transport. To determine a suitable field injection approach, a series of bench scale experiments were undertaken in the laboratory. First, batch experiments focussed on the kinetics of calcite precipitation as a function of bacterial mass, urea and Ca2+ concentration and anaerobic vs aerobic conditions. Results showed that the ureolytic bacteria performed equally well under both oxygen poor and oxygen rich conditions. In the next stage, flow-through experiments in various media (sand columns, rock cores) were carried out to examine the homogeneity and extent of the pore space fill along the column / core as a function of injection strategies. It emerged that a staged injection strategy, where we alternate between bacterial and reactant injection, yields the most homogeneous calcite fill, reducing overall porosity by up to 45 %. Ultimately, this approach was tested at the field scale, led by University of Birmingham, to seal a fractured rock (dacite) at ~28 m depth, in a quarry in Leicestershire, UK. Within few injection cycles, the single fracture was substantially plugged by calcite, yielding a significant transmissivity decrease over several meters.

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Primary authors

Dr Dominique J. Tobler (Nano-Science Center, Department of Chemistry, University of Copenhagen, Denmark) Dr Mark O. Cuthbert (School of Earth and Ocean Sciences, Cardiff University, United Kingdom) Dr Michael S. Riley (School of Geography, Earth and EnvironmentalSciences, University of Birmingham, United Kingdom) Dr Stephanie Handley-Sidhu (School of Geography, Earth and Environmental Sciences, University of Birmingham, United Kingdom) Prof. Vernon R. Phoenix (Civil and Environmental Engineering, University of Strathclyde, United Kingdom)

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