Department of Earth Sciences

Flow in fractured rocks and deep hydrogeological systems

Flow in Fractured Rocks

Contact person: Auli Niemi

Study of fractured rocks is important for a number of important applications, from nuclear waste investigations, to pollution control and remediation as well as various energy applications. We have a long tradition in this research, from modeling to experimental characterization, with some key publications listed below.

Present research project financed by Swedish Geological Survey (SGU) investigates the hydromechanical and chemical processes in the deep borehole COSC-1. The objective is to study and analyze all collected data to identify possible correlations, in order to build an integrated geohydrological, geochemical and geohydromechanical model of the COSC-1. For example, the available hydrogeological information gathered at the COSC-1 site has to be compared to other datasets, such as indicators of the stress field or geochemical/mineralogical data, in order to identify converging interpretations. 

In a project financed by Swedish Nuclear Authority (SSM) we are investigating the effect of flow channeling and sparse fracture networks and how such influence the interpretation of hydraulic and tracer tests. It is commonly accepted that conceptual model uncertainty is high for flow and transport in deep crystalline rock, due to the inherent heterogeneity of the medium. In a single rock fracture, it has been shown that the heterogeneity in aperture and permeability leads to strongly channelized flow (e.g. Tsang and Neretnieks, 1998; Larsson et al, 2012). Some field evidence points towards sparse networks of long channels as a suitable conceptual model to describe flow in good crystalline rock in the deep subsurface (Black et al., 2016).The objectives of this project is to develop and apply the sparse channel network model to examine the effect of sparseness on field measurements such as transient pressure tests or tracer tests, calibrate the models with existing data and apply them to estimate the probability of channels intersecting tunnels/deposition holes and the impact of sparseness on long term predictions relevant for the safety assessment of deep waste repositories. An additional objective is to identify relevant sets of channel parameters, taking into account the disparity in stress regimes between the interior of the rock mass and the fracture mappings/measurements on outcrops and cores.

Flow though percolating clusters simulated by PYCHAN3, from Dessirier et al (2017)

Flow though percolating clusters simulated by PYCHAN3 (Dessirier et al., 2017)

We are also addressing the effect of coupled hydro-mechanical processes in fractures and fracture networks in a number of different applications, from geological storage of CO2, to unconventional hydrocarbon recovery and Enhanced Geothermal Systems (EGS). For all of these applications it is common that fluid needs to be injected in a manner that does not cause unwanted pressure effects. Properly addressing this requires coupled modelling of the hydraulic flow processes and the mechanical processes.

Example scenarios of geometries for hydromechanical simulations in unconventional hydrocarbon recovery (Figueiredo et al, 2017)

Example scenarios of geometries for hydromechanical simulations in unconventional hydrocarbon recovery (Figueiredo et al, 2017)

Two-phase flow and transport in fractures

Contact person: Zhibing Yang

Two-phase flow in fractures occurs as a “competition” between the fluids for the pore or void space under the combined influence of capillary, gravitational, viscous, and inertial forces. The interplay of these forces is in turn influenced by the fluid and fracture properties. We perform carefully controlled experiments and develop mechanistic models to improve the understanding of the two-phase flow behavior in rock fractures.

Fracture aperture topologies strongly control fluid-fluid displacement. The figure below shows drastically different drainage patterns for various combinations of the geostatistical parameters of the aperture field (more details can be found here and here). These patterns cast decisive influence on macro-scale flow properties such as relative permeabilities, residual trapping, and interphase mass transfer coefficient, which are needed in modeling two-phase flow and transport at the continuum scale. 

Groundwater contamination by dense non-aqueous phase liquids (DNAPLs) poses a significant environmental issue. Entrapment and dissolution behavior of DNAPLs in fractured media is complicated due to the heterogeneity at different scales, arising from aperture variability within individual fractures as well as from fracture connectivity in a network. Understanding the dissolution behavior of dense non-aqueous phase liquids (DNAPLs) in rock fractures is critical for remediation strategy design and risk assessment. We experimentally study the DNAPL trapping and dissolution in transparent analog fractures using light transmission techniques. We develop high-resolution numerical models to improve our fundamental understanding of the dissolution process. The figure below summarizes some of our experimental and simulation results. More details are given here and here.

Relevant recent publications

Figueiredo B, Tsang CF, Rutqvist J, Niemi A, 2017. Study of hydraulic fracturing processes in shale formations with complex geological settings. Journal of Petroleum Science and Engineering 152: 361-74

Figueiredo, B, C-F Tsang, A. Niemi and G. Lindgren (2016) A review of the state-of-art of sparse channel model and its applicability to radioactive waste repository in deep fractured crystalline formation. Hydrogeology Journal. Volume: 24   Issue: 7   Pages: 1607-1622

Figueiredo, B,  CF. Tsang, A. Niemi, J. Rutqvist and J. Bensabat (2015) Study of the Potential Fault Reactivation  induced by CO2 injection in a three-layer storage formation. Proceedings ISRM International Society of Rock Mechanics. 13th International ISRM Congress 2015, Montreal, Canada

Tsang Chin-Fu, Jan-Erik Rosberg, Prabhakar Sharma, Theo Berthet, Christopher Juhlin, and Auli Niemi (2016). Hydrologic testing during drilling: Application of flowing fluid electric conductivity (FFEC) logging method to drilling of a deep borehole. Hydrogeology Journal. Volume: 24   Issue: 6   Pages: 1333-1341   

Yang, Z., Neuweiler, I., Meheust,Y., Fagerlund, F. and Niemi, A (2016) Fluid trapping during capillary displacement in fractures Advances in Water Resources. Advances in Water Resources. Volume: 95    Pages: 264-275   Published: SEP 2016

Sharma, P., Tsang, C-F, Kukkonen, I and Niemi, A. (2015) Analysis of 6-year Fluid Electric Conductivity logs to evaluate the hydraulic structure of the deep drill hole at Outokumpu, Finland. International Journal of Earth Sciences. Int J Earth Sci (Geol Rundsch) DOI 10.1007/s00531-015-1268-x. Volume: 105   Issue: 5   Pages: 1549-1562    

Figueiredo, B., Tsang, C.F., Rutqvist, J., Niemi, A. (2015). A study of changes in deep fractured rock permeability due to coupled hydro-mechanical effects. International Journal of Rock Mechanics and Mining Sciences 79C: 70-85. DOI: 10.1016/j.ijrmms.2015.08.011

Figueiredo, B, Tsang, CF , Rutqvist, J, Bensabat, J and Niemi, A (2015) Coupled hydro-mechanical processes and fault reactivation induced by Co2 Injection in a three-layer storage formation Int Jour Greenhouse Gas Control, Volume: 39, Pages: 432-448, DOI: 10.1016/j.ijggc.2015.06.008

Yang, Z., A. Niemi, F. Fagerlund, T. Illangasekare and R. Detwiler (2013), Dissolution of dense non-aqueous phase liquids in vertical fractures: effect of finger residuals and dead-end pools, Jour Cont Hydrology, Vol 149, 88-99.  DOI: 10.1016/j.jconhyd.2013.03.006.

Larsson, M., Doughty, C., Tsang, CF and Niemi, A. (2013) Understanding the effects of single fracture heterogeneity from single well injection withdrawal (SWIW) tests. Hydrogeol Jour. 21(8):1691-1700.

Larsson, Oden, Niemi, Neretnieks and Tsang (2013) A new approach to account for fracture  aperture variability when modeling solute transport in fracture networks. Water Resour Res. 49(4): 2241-2252  

Yang, Z., A. Niemi, F. Fagerlund and T. Illangasekare (2013), Two-phase flow in rough-walled fractures: comparison of continuum and invasion-percolation models. Water Resources Research. 49(2), 993–1002, DOI:10.1002/wrcr.20111

Tsang, C-F and Niemi, A (2013) Deep Hydrogeology - A discussion of the issues and research needs. Hydrogeol J  (21(8):1687-1690)

Yang, Niemi, Fagerlund and Illangasekare. (2012). A generalized approach for estimation of in-plane curvature in invasion percolation models for drainage in fractures.  Water Resour Res. Vol 48

Yang, Niemi, Fagerlund and Illangasekare. (2012). Effects of single-fracture aperture statistics on entrapment, dissolution and source depletion behavior of dense non-aqueous phase liquids. J. Contam Hydrol, 133, 1-1

Larsson, Niemi, Tsang, (2012), A study of flow-wetted surface area in a single fracture as a function of its hydraulic conductivity distribution,  Water Resour Res. 48 DOI:10.1029/2011WR010686

Odén, Niemi, et al (2008), Regional channelized transport in fractured media with matrix diffusion and linear sorption,  Water Resour Res, 44, W02421