Use Of A Coupled Thermo-Hydro-Mechanical Model To Constrain The Risk Of Ground Surface Deformation Due To Subsurface Energy Storage And Production
The production of hydrocarbons and/or hot fluids for geothermal energy cause changes in subsurface porepressure and temperature, which can lead to thermo- and poro-elastic stresses and strains. These stresses and strains can cause geotechnical problems at the surface and wellbore integrity problems in the subsurface. In this work, we investigate ground surface deformation for high-temperature (>25 ºC) aquifer thermal energy storage (HT-ATES). The goal of HT-ATES is to store heat in the summer and extract it for district heating in the winter, which can reduce greenhouse gas emissions and potentially decrease heating costs. But the technical and economic feasibility of HT-ATES is uncertain, partially because research on ground surface deformation in the context of HT-ATES has been very limited. We run simulations based on a proposed HT-ATES pilot project in Geneva, Switzerland. Possible target formations at the site include: (a) Tertiary sandstone layers interbedded within lower-permeability sedimentary rock and (b) fractured Mesozoic limestone structures. We use the Multiphysics Object Oriented Simulation Environment (MOOSE) to solve the equations of thermo-poro-elasticity. MOOSE is a generalized finite element code that solves the fully-coupled equations monolithically, and it takes advantage of the Portable, Extensive Toolkit for Scientific Computation (PETSc) for parallelization. Preliminary results show that surface deformation is a function of target formation depth and the rock properties. Coupled thermal-hydraulic-mechanical (THM) models are useful to evaluate the risk of surface deformation prior to drilling (since drilling costs are high) and throughout operations (since different operating procedures could cause more or less deformation). THM models can be calibrated to reflect specific sites if surface deformation data is available (for example from InSAR). Our approach to model the risk of surface deformation is applicable to other subsurface energy projects, especially when reservoir pressure and temperature need to be managed (e.g. enhanced oil recovery and geothermal energy production).
AAPG Datapages/Search and Discovery Article #90346 ©2019 AAPG European Region, 3rd Hydrocarbon Geothermal Cross Over Technology Workshop, Geneva, Switzerland, April 9-10, 2019