Application of hybrid numerical and analytical solutions for the simulation of coupled thermal, hydraulic, mechanical and chemical processes during fluid flow through a fractured rock

Abstract

In many subsurface engineering geoscience applications the impact of thermal, hydraulic, mechanical and chemical (THMC) processes needs to be evaluated. Coupled process models require solution of the partial differential equations describing energy or mass balance. Ignoring the coupling of these processes can lead to a significant oversimplification which may not adequately represent the systems being modelled. Incorporation of coupled processes and associated phenomena inevitably leads to numerical stability issues due to very different scales in terms of spatial distribution, time and parametrical heterogeneity. One approach to simplify the computational demands is to integrate analytical and physical models into standard numerical modelling techniques (in this case finite elements), effectively adding sub-grid scale and sub-time scale information to the model. We present such an approach for the simulation of fluid flow through a fracture validated against experimental data and cross comparison with results of other modelling teams within the DECOVALEX 2015 (development of coupled models and their validation against experiments) project (http:// www.decovalex.org). By replacing the mechanical behaviour and chemical transport processes with physical models, and by utilising the static nature of the temperature changes, only the hydraulic system required numerical solution in a highly coupled problem. Physical models for fracture closure due to pressure solution, fracture opening due to chemical dissolution, the development of channel flow and a change in the reactive transport characteristics with time were implemented and are described here. The main features of the experimental data could be replicated, although lying outside of the parameter range suggested by the literature. Comparison with other teams using different modelling approaches indicated internal consistency.

Utilizing supercritical geothermal systems: a review of past ventures and ongoing research activities

“…This international collaboration (http://www.decovalex.org), which began in 1992, has focused on advancing the understanding and mathematical modeling of coupled thermo-hydro-mechanical (THM) and thermo-hydro-chemical (THC) processes in geological systems related to radioactive waste disposal. The participating groups have utilized many different modeling tasks, constrained by field data, to compare modeling approaches and methods-some recent examples include evaluating the effects of thermal, hydrologic, chemical, and mechanical processes on the permeability of fractured rocks (e.g., Bond et al 2016;Hokr et al 2016;McDermott et al 2015;Rutqvist 2014). The geothermal community could emulate this type of international collaboration to advance the use of numerical simulations in supercritical systems.…”

Experimental Investigation of Hydraulic Fracturing and Stress Sensitivity of Fracture Permeability Under Changing Polyaxial Stress Conditions

“…The topography of fracture surfaces leads to significantly more complex behaviours, such as channelization (e.g. Guo et al, 2016;McDermott et al, 2015), non-linear flow (Konzuk & Kueper, 2004;Zhang & Nemcik, 2013;Zhou et al, 2015), non-linear relationships between fracture normal stress and effective hydraulic aperture (e.g. Bandis et al, 1983;Barton et al, 1985;Pyrak-Nolte et al, 1987;Witherspoon et al, 1980;Zimmerman & Main, 2003), and potential effective hydraulic aperture change when displacement juxtaposes fracture surface asperities (Chen et al, 2000;Lee & Cho, 2002;Shen et al, 2020;Vogler et al, 2016).…”

“…The hydromechanical behavior of rock fractures is of fundamental importance for a wide variety of subsurface applications. These include groundwater resources (Gaus et al, 2000), geotechnical applications such as tunnel excavation (Bossart et al, 2002), radioactive waste disposal (Birkholzer et al, 2018; Fraser Harris et al, 2015; Hudson et al, 2005; McDermott et al, 2015), carbon capture and storage (McCraw et al, 2016; McDermott et al, 2016), energy storage (e.g., strategic gas storage, compressed air storage or hydrogen storage Bai et al, 2018; Heinemann et al, 2018; Kabuth et al, 2017), tight conventional and unconventional hydrocarbons (Aybar et al, 2014; Fatahi et al, 2017; Guo et al, 1993, 2014), and geothermal energy (Hu et al, 2020; McClure & Horne, 2014; McDermott et al, 2006; Tomac & Sauter, 2018). In low permeability rocks, extraction technologies such as unconventional hydrocarbons and geothermal energy, fractures represent desirable high permeability pathways that facilitate economic fluid flow.…”

“…However, fractures are not simply planar parallel plates, and many authors have shown that taking the mean mechanical aperture (determined from fracture surface characteristics and used to represent the aperture between parallel plates) will not result in an accurate prediction of fluid flow (Kulatilake et al, 2008; Renshaw, 1995). The topography of fracture surfaces leads to significantly more complex behaviors, such as channelization (e.g., Guo et al, 2016; McDermott et al, 2015), nonlinear flow (Konzuk & Kueper, 2004; Zhang & Nemcik, 2013; Zhou et al, 2015), nonlinear relationships between fracture normal stress and effective hydraulic aperture (e.g., Bandis et al, 1983; Barton et al, 1985; Pyrak‐Nolte et al, 1987; Witherspoon et al, 1980; Zimmerman & Main, 2003), and potential effective hydraulic aperture change when displacement juxtaposes fracture surface asperities (Chen et al, 2000; Lee & Cho, 2002; Shen et al, 2020; Vogler et al, 2016).…”

Coupled Hydraulic-Thermal Modelling and Related Numerical Analysis on Rock Fractures

“…McDermott et al [1] presented such an approach for the simulation of fluid flow through a fracture validated against experimental data and cross-comparison with results of other modelling teams within the DECOVALEX 2015 project by replacing the mechanical behavior and chemical transport process within physical models, and some results of thermal-hydraulic-mechanical-chemical conditions for fracture rock were attained. Cacace and Jacquey [2] developed theory and numerical implementation describing groundwater flow and the transport of heat and solute mass in fully saturated rocks with elastoplastic mechanical feedbacks; in the model, fractures were considered being of lower dimension than the hosting deformable porous rock.…”