Modeling, simulation, and optimization of geothermal energy production from hot sedimentary aquifers

Abstract

Geothermal district heating development has been gaining momentum in Europe with numerous deep geothermal installations and projects currently under development. With the increasing density of geothermal wells, questions related to the optimal and sustainable reservoir exploitation become more and more important. A quantitative understanding of the complex thermo-hydraulic interaction between tightly deployed geothermal wells in heterogeneous temperature and permeability fields is key for a maximum sustainable use of geothermal resources. Motivated by the geological settings of the Upper Jurassic aquifer in the Greater Munich region, we develop a computational model based on finite element analysis and gradient-free optimization to simulate groundwater flow and heat transport in hot sedimentary aquifers, and numerically investigate the optimal positioning and spacing of multi-well systems. Based on our numerical simulations, net energy production from deep geothermal reservoirs in sedimentary basins by smart geothermal multi-well arrangements provides significant amounts of energy to meet heat demand in highly urbanized regions. Our results show that taking into account heterogeneous permeability structures and a variable reservoir temperature may drastically affect the results in the optimal configuration. We demonstrate that the proposed numerical framework is able to efficiently handle generic geometrical and geological configurations, and can be thus flexibly used in the context of multi-variable optimization problems. Hence, this numerical framework can be used to assess the extractable geothermal energy from heterogeneous deep geothermal reservoirs by the optimized deployment of smart multi-well systems. Keywords Porous and fractured geothermal reservoir modeling • Geothermal multi-well configurations • Finite element method • Thermo-hydraulic coupling • Optimization • Open-source software PACS 65M60 • 76S05 • 86-08 • 86A20 Publisher's note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Closed-Loop Systems for Geothermal Energy Exploitation from Hydrocarbon Wells: An Italian Case Study

“…In coaxial WBHEs, the steel downward is in contact with the hole in the well. The energy balance of the fluid in the injection pipe can be expressed with the following equation [14,35]:…”

“…By assuming steady heat transfer and constant heat flux in wellbore components (e.g., insulation, casing and cement), heat extraction from the formation dQ/dz can be assumed to be equal to the heat flux through the outside surface of the wellbore (interface of the wellbore and rock formation) to the injected fluid [14,35]:…”

“…Although geothermal open-loop systems in sedimentary formations may provide a sustainable solution where the geothermal potential and heat demand coincide [14,15], these technologies are subject to some technical problems, including groundwater recession, corrosion and scaling. Further important issues are represented by the reinjection of fluids [16,17] and by the complex additional exploration activities [18].…”

Impact of Well Placement in the Fractured Geothermal Reservoirs Based on Available Discrete Fractured System

“…Several optimization techniques are available for determining well placement in a reservoir [5]. Some of these methods are gradient free methods including genetic algorithms, particle swarm optimization algorithm [6], fast marching method [7] and simultaneous perturbation stochastic approximation [8,9] and gradient based optimization methods including adjoint methods [10,11,12,13]. These models lack in geological uncertainty while considering well placement optimization [14].…”

“…[1 -6].A fully coupled thermo-hydro-mechanical model is developed in this study. If the effective stress is 𝝈 𝒆𝒇𝒇 𝒊𝒋 = 𝝈 𝒊𝒋 + 𝜶 𝒑 𝒑𝜹 𝒊𝒋 and the volumetrix expansion coefficient of porous media is 𝜷 𝑻 = 𝝓 𝒍 𝜷 𝒍 + (𝟏 − 𝝓 𝒎 )𝜷 𝒎 , then the stress-strain relationship considering fully coupled thermoelastic and poroelastic stress can be written as: 𝝈 𝒊𝒋 = 𝟐𝑮𝜺 𝒊𝒋 + 𝝀𝒕𝒓𝜺𝜹 𝒊𝒋 − 𝜶 𝒑 𝒑𝜹 𝒊𝒋 − 𝑲 ′ 𝜷 𝑻 𝑻𝜹 𝒊𝒋[7] The reservoir deformation equation can be written as: 𝑮𝒖 𝒊,𝒋𝒋 + (𝑮 + 𝝀)𝒖 𝒋,𝒋𝒊 − 𝜶 𝒑 𝒑 ,𝒊 − 𝑲 ′ 𝜷 𝑻 𝑻 ,𝒊 + 𝒇 𝒊 = 𝟎…”