Brine migration through fault zones: 3D numerical simulations for a prospective CO2 storage site in Northeast Germany

Tillner, Elena; Kempka, Thomas; Nakaten, Benjamin; Kühn, Michael

doi:10.1016/j.ijggc.2013.03.012

Cited by 34 publications

(32 citation statements)

References 27 publications

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“…The Rupelian basal sand is 20 m thick and located at a depth of 110 m (Grube et al, 2000). The Lower Muschelkalk Formation is at 1025 m depth and has a thickness of 140 m, while the reservoir is at 1425 m depth with a thickness of 23 m (Tillner et al, 2013a). Figure 2b shows the geological model with a regular lateral grid resolution of 250 m × 250 m. The vertical discretisation depends on the different model layers, and ranges between 10 and 19.9 m ( Table 2).…”

Section: Set-upmentioning

confidence: 99%

“…All lithological units were parameterised according to Tillner et al (2013a) and Vattenfall (2009), with values derived from borehole data and literature, and modelled as homogenous and isotropic. The Detfurth Formation has a permeability of 400 mD, while the overlying secondary reservoir (Muschelkalk Formation) is characterised by a permeability of 200 mD (Table 2).…”

Section: Parameterisationmentioning

confidence: 99%

“…Table 1 summarises the initial conditions and essential results of numerical simulations concerning this issue. The models applied are either synthetic (Birkholzer et al, 2009(Birkholzer et al, , 2011Oldenburg and Rinaldi, 2011) or refer to a certain study area (Tillner et al, 2013a;Zouh et al, 2010;Yamamoto et al, 2009;Nicot, 2008). Several studies examine pressure perturbation and resulting brine migration in a multi-barrier system without considering vertical conduits.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, a meaningful implementation of complex geological structures into a sufficiently discretised model grid is difficult, especially at a regional scale. Tillner et al (2013a) investigated the influence of permeable faults on brine displacement referring to a real study area. The authors simulated upward brine migration through complex fault systems depending on reservoir compartmentalisation and fault permeability, whereby faults were implemented by the virtual element approach (Nakaten et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

“…The authors simulated upward brine migration through complex fault systems depending on reservoir compartmentalisation and fault permeability, whereby faults were implemented by the virtual element approach (Nakaten et al, 2013). The results of Tillner et al (2013a) showed that the degree of pressurisation is the driving mechanism for brine migration, while an increase of fault permeability from 100 mD by 2 orders of magnitude had no significant impact on the salinisation of shallower aquifers. Their investigations focused on the prospective storage site Beeskow-Birkholz (in the following only referred to as Beeskow) in northeast Germany, which is also considered in this work.…”

Section: Introductionmentioning

confidence: 99%

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Fault damage zone volume and initial salinity distribution determine intensity of shallow aquifer salinisation in subsurface storage

Tillner

Langer

Kempka

et al. 2016

Hydrol. Earth Syst. Sci.

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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.

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Section: Set-upmentioning

confidence: 99%

Section: Parameterisationmentioning

confidence: 99%