# Well-Doublets: A First-Order Assessment of Geothermal SedHeat Systems
### Disequilibrium Processes  
Leaving aside initial geological conditions, the causes of disequilibrium that result in an inadequate or a drop in \(\mathrm{\dot{E}}\) are based on mechanical, geochemical, and heat conductivity conditions and issues, ranging from processes within the reservoir itself (flow, mineral precipitation, channelling, etc.) to the access and energy systems (wells, pumps, heat exchangers, surface tubing insulation, etc.).  
1. Chemical condition: 1. Well integrity 1. Induced primary loop corrosion (e.g., acidic waters corroding steel), both internal and external to the well casing, potentially exacerbated by high temperatures and electrochemical corrosion 2. Primary loop internal mineral precipitation--scaling (increasing pipe friction losses) 2. Reservoir condition 1. Mineral and rock dissolution (e.g., dissolving of gypsum) or other alteration (e.g., induced clay mineral swelling from changing geochemistry). 2. Microbiologically induced pore blockage or corrosion through the generation of biofilms or weak organic acids that act on minerals (mainly carbonates) 3. Chemical changes and processes induced by flow, \(\Delta\Gamma\), and \(\Delta\Gamma\), leading to solubility gradients that trigger dissolution and precipitation 4. Flushing of pipe corrosion and precipitated mineral particles into the reservoir, generating blockage of flow paths 2. Mechanical condition: 1. Rock mechanics issues: stress-strain (\(\sigma\)-\(\epsilon\)) processes and their effects on porosity and permeability, particularly in systems dominated by fracture flow and susceptible to thermoelastic impacts 2. The transition from laminar to turbulent flow regime near the well at high flow rates (short-term impacts on production and injection phases) 3. Heat conductivity and recovery condition:* Pumping rates with respect to produced fluid temperature changes and well field life-span
* Alterations of efficiency associated with thermal viscosity changes
* Interference with the natural thermal recharge system in the deep aquifer
* Channeling of flow, fracture dilation through cooling leading to flow short-circuiting, and related thermoelastic effects that lead to reductions in the subsurface heat exchange area  
The long-term result of disequilibrium processes in the reservoir may be evidenced as pore throat blockage and fracture aperture reduction, leading to reservoir fluid conductivity changes, including permeability reduction, channeling of flow, and related processes. If these changes are properly understood and predicted, project planning becomes easier, allowing answers to questions related to the drilling of new wells, workover scheduling for impaired wells, adding more injection or production wells, developing a new productive horizon (deeper or shallower), changing the electricity/heat output ratio, and so on.  
To optimize energy production, increase the project life-time, enhance the fiscal outcomes and minimize environmental impacts, many issues associated with heat extraction from a geothermal well-doublet system need to be considered; these issues are addressed in this study.