@misc{TillnerLangerKempkaetal.2016,
  author    = {Tillner, Elena and Langer, Maria and Kempka, Thomas and K{\"u}hn, Michael},
  title     = {Fault damage zone volume and initial salinity distribution determine intensity of shallow aquifer salinisation in subsurface storage},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {548},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-41185},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-411854},
  pages     = {19},
  year      = {2016},
  abstract  = {Injection of fluids into deep saline aquifers causes a pore pressure increase in the storage formation, and thus displacement of resident brine. Via hydraulically conductive faults, brine may migrate upwards into shallower aquifers and lead to unwanted salinisation of potable groundwater resources. In the present study, we investigated different scenarios for a potential storage site in the Northeast German Basin using a three-dimensional (3-D) regional-scale model that includes four major fault zones. The focus was on assessing the impact of fault length and the effect of a secondary reservoir above the storage formation, as well as model boundary conditions and initial salinity distribution on the potential salinisation of shallow groundwater resources. We employed numerical simulations of brine injection as a representative fluid. Our simulation results demonstrate that the lateral model boundary settings and the effective fault damage zone volume have the greatest influence on pressure build-up and development within the reservoir, and thus intensity and duration of fluid flow through the faults. Higher vertical pressure gradients for short fault segments or a small effective fault damage zone volume result in the highest salinisation potential due to a larger vertical fault height affected by fluid displacement. Consequently, it has a strong impact on the degree of shallow aquifer salinisation, whether a gradient in salinity exists or the saltwater-freshwater interface lies below the fluid displacement depth in the faults. A small effective fault damage zone volume or low fault permeability further extend the duration of fluid flow, which can persist for several tens to hundreds of years, if the reservoir is laterally confined. Laterally open reservoir boundaries, large effective fault damage zone volumes and intermediate reservoirs significantly reduce vertical brine migration and the potential of freshwater salinisation because the origin depth of displaced brine is located only a few decametres below the shallow aquifer in maximum. The present study demonstrates that the existence of hydraulically conductive faults is not necessarily an exclusion criterion for potential injection sites, because salinisation of shallower aquifers strongly depends on initial salinity distribution, location of hydraulically conductive faults and their effective damage zone volumes as well as geological boundary conditions.},
  language  = {en}
}
@article{SieberYaxleyHermann2020,
  author    = {Sieber, Melanie Jutta and Yaxley, Gregory M. and Hermann, J{\"o}rg},
  title     = {Investigation of fluid-driven carbonation of a hydrated, forearc mantle wedge using serpentinite cores in high-pressure experiments},
  series = {Journal of petrology},
  volume    = {61},
  journal   = {Journal of petrology},
  number    = {3},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  issn      = {0022-3530},
  doi       = {10.1093/petrology/egaa035},
  pages     = {24},
  year      = {2020},
  abstract  = {High-pressure experiments were performed to investigate the effectiveness, rate and mechanism of carbonation of serpentinites by a carbon-saturated COH fluid at 1.5-2.5 GPa and 375-700 degrees C. This allows a better understanding of the fate and redistribution of slab-derived carbonic fluids when they react with the partially hydrated mantle within and above the subducting slab under pressure and temperature conditions corresponding to the forearc mantle. Interactions between carbon-saturated CO2-H2O-CH4 fluids and serpentinite were investigated using natural serpentinite cylinders with natural grain sizes and shapes in piston-cylinder experiments. The volatile composition of post-run fluids was quantified by gas chromatography. Solid phases were examined by Raman spectroscopy, electron microscopy and laser ablation inductively coupled plasma mass spectrometry. Textures, porosity and phase abundances of recovered rock cores were visualized and quantified by three-dimensional, high-resolution computed tomography. We find that carbonation of serpentinites is efficient at sequestering CO2 from the interacting fluid into newly formed magnesite. Time-series experiments demonstrate that carbonation is completed within similar to 96 h at 2 GPa and 600 degrees C. With decreasing CO2, aq antigorite is replaced first by magnesite + quartz followed by magnesite + talc + chlorite in distinct, metasomatic fronts. Above antigorite stability magnesite + enstatite + talc + chlorite occur additionally. The formation of fluid-permeable reaction zones enhances the reaction rate and efficiency of carbonation. Carbonation probably occurs via an interface-coupled replacement process, whereby interconnected porosity is present within reaction zones after the experiment. Consequently, carbonation of serpentinites is self-promoting and efficient even if fluid flow is channelized into veins. We conclude that significant amounts of carbonates may accumulate, over time, in the hydrated forearc mantle.},
  language  = {en}
}