Session 1 : Reservoir geomechanics and reservoir management
Keynote speaker : Brice Lecampion, École Polytechnique Fédérale de Lausanne
Summary : Fundamentals in fluid flow and geomechanics for sustainable geothermal reservoir developement and management
This presentation will discuss the workflow and methods to characterize and manage fluid circulation in geothermal reservoirs from a geomechanical point of view. We will in particular focus on the following key-points: i) in-situ stress field characterisation, ii) hydraulic stimulation design and monitoring, and iii) multi-scale reservoir geo-mechanical response. Incorporation of uncertainties in engineering decision will be highlighted.
Session 2 : Earthquake mechanics
Keynote speaker : Serge Shapiro, Freie Universität Berlin
Summary : Seismic Hazard Induced by Production of Hydrocarbon and Geothermal Energy
Productions and injections of fluids in rocks can induce significant earthquakes. Induced seismicity is observed by hydraulic fracturing of shale and stimulation of enhanced geothermal systems.
Earthquakes can be caused by long-term developments of oil and gas fields. Understanding and monitoring of fluid-induced seismicity is necessary for controlling its seismic risk. The talk provides an overview of physical and geomechanical fundamentals of the seismic hazard, of approaches to its control and of various relevant case studies.
Session 3 : Faults characteristics and properties
Keynote speaker : Thomas Mitchell, University College London
Session 4 : Modelling of geothermal processes
Keynote speaker : Inga Berre, University of Bergen
Summary : Modelling of fault slip in hydraulic stimulation of geothermal reservoirs: governing mechanisms and process-structure interaction
Hydraulic stimulation of geothermal reservoirs in basement or crystalline igneous rock can enhance permeability by reactivation and shear-dilation of existing fractures. The process is characterized by interaction between fluid flow, thermal transport, rock deformation and the fractured structure of the formation. For example, the flow is highly affected by the fracture network, which in turn is deformed because of thermo-hydro-mechanical stress changes caused by the fluid injection. This process-structure interaction is decisive for the outcome of a stimulation and, in analysis of governing mechanisms, physics-based modeling has potential to complement field and experimental data. Here, we show how recently developed mathematical models and simulation technology are valuable as tools to understand governing mechanisms of thermo-hydro-mechanical coupled processes and the reactivation and deformation of faults. The methodology fully couples flow in faults and matrix with thermoporoelastic matrix deformation and a contact mechanics model for the faults, including dilation because of slip.
Final words: Applied geothermal case studies / introduction to geothermal site visits
Keynote speaker: Christian Boissavy, G²H Conseil
Summary: Deep geothermal energy for district heating network: case histories in Paris Basin and lessons learned since 50 years
During the last 50 years, about 90 geothermal plants have been installed in the Paris basin, of which 90% are located in the central region of Ile de France. The Dogger limestones are the key geothermal target with more than 80% of the reservoirs tapped compared to others geological formations made of various sands and sandstones (Albian, Neocomian and Triassic).
The first geothermal doublet was drilled in Melun l’Almont in 1969 and more than 100 wells have been drilled before 1988. The corrosion and scaling problems caused by the geothermal water has affected deeply the exploitation of the doublets with casing perforation and /or diameter reduction, electrical submersible pumps broken, surface equipment plugged…At that time many plants have been closed for both technical and financial problems. Strong efforts in R&D, supported by the BRGM and much new experimental equipment where tested to overcome this bottleneck. Many good achievements have been successful with new technologies to clean the wells, new bio- chemical approach of the phenomenon, installation of downhole line injecting inhibitors at the bottom of the production wells and evolution of the well design towards bigger well diameter. This learning phase for exploitation and management of new doublets has allowed the developers to restart the deployment 15 years ago using the improved new technologies and also benefitting of the subsidies of the new Heat Fund administrated by ADEME. Since 2006, 25 new plants have been created and old one been revamped with the use of new tools such as, horizontal drilling, multi-drains in the reservoir and more frequent use of composite casings. The planned power to be installed in the next ten years, in Ile de France, is ambitious (240 MWth) following the PPE (Energy Programing of the Ministry of Ecological transition). This target is attainable but the Risk Mitigation System managed by SAF Environment, to cover the geological and hydrogeological risk, remains even after 50 years of deployment, the main tool since 1980, in order to achieve the development of geothermal district heating network in Paris area.