Webinar cycle in Hydrogeology and Geochemistry
HYDROGEOLOGY GROUP (Associated Unit CSIC-UPC, Barcelona)
Date: Thursday, 22nd September 2022
Starting time: 3:00 pm (Central European Time)
Duration: 1h
Guest Speaker: Iman Vaezi, PhD student
Title: Numerical modeling of coupled processes in hydraulic stimulation of fractured rock employing a continuum approach
Venue: UPC, Module D2, 2nd floor, 214 Classroom or
Live in: https://meet.google.com/snb-qdkn-eex (free of charge)
Abstract:
A global desire toward a CO2 nuclear-free world has promoted interest in deep geothermal energy as an alternative source potentially providing continuous energy output independent of seasonal fluctuations. The concept of an enhanced geothermal system is to exploit regions with high thermal gradients through the creation (hydrofracturing) or reactivation (hydroshearing) of a fracture network by increasing rock permeability to enhance fluid circulation. Numerical simulation faces some challenges to study these coupled processes while considering a large number of fractures. To diminish those challenges, we first focus on a simple problem to fully understand the hydro-mechanical behavior of a single fracture represented by an equivalent fracture layer subjected to a constant injection flow rate. The equivalent fracture layer implicitly represents the fracture with a thickness that is several orders of magnitude thicker than the actual fracture aperture. The equivalent fracture layer provides identical results for pore pressure, flow, displacement and stress evolution and distribution. Once this upscaling approach is verified, we employ it to model the hydraulic stimulation of a fracture in crystalline rock performed at the Bedretto underground laboratory to investigate poromechanical processes due to fluid injection. To reproduce the pore pressure evolution, it is necessary to include slip-weakening friction and dilatancy. Simulation results have been permitted to identify the onset of fracture reactivation and provide insight into the processes that occur during stimulation of hard low-permeable rock.