fimbul-overview

name	fimbul-overview
description	High-level Fimbul workflow, geothermal case factories, and result inspection

Fimbul orientation

When to use

Use this skill for any geothermal task on Fimbul — aquifer or borehole thermal energy storage (ATES, BTES, FTES, HTATES), conventional and enhanced geothermal systems (doublet, EGS, AGS, closed-loop coaxial BHE), or analytical sanity checks.

Mental model

Fimbul extends JutulDarcy with an energy-conservation equation that transports heat by advection and conduction. A Fimbul simulation is structurally a JutulDarcy reservoir simulation with a temperature field, so JutulDarcy's primitives (grids, reservoir_domain, wells, simulate_reservoir) carry over unchanged.

The simplest entry point is a case factory — a function in Fimbul that returns a JutulCase for a named example geometry:

using Fimbul, JutulDarcy
case = egg_geothermal_doublet()        # case object
result = simulate_reservoir(case; info_level = 1)  # run it; info_level = 2 if convergence struggles
T = result.states[end][:Temperature]   # final-state temperature field

When you need a custom case, drop down to JutulDarcy primitives and add geothermal physics through the same Fimbul/JutulDarcy API surface.

Finding what you need

Fimbul's source is read-only depot source; its path is given to you up front, so browse it directly with the file tools (see the workspace-and-source skill):

# Fimbul source path is in your system prompt -> /.../Fimbul/<hash>
glob("/.../Fimbul/examples/**/*.jl")              # analytical / production / storage
grep("function egg_geothermal", path="/.../Fimbul/src")   # a case factory's source
read_file("/.../Fimbul/examples/production/doublet_demo.jl")

Fimbul builds on JutulDarcy, whose source sits alongside at pkgdir(JutulDarcy). Reach for it (and the JutulDarcy skills) for the grid, mesh, and well primitives Fimbul reuses:

glob("/.../JutulDarcy/examples/**/*.jl")          # reservoir + well setup
grep("setup_well", path="/.../JutulDarcy/src")

For docstrings, stay in the REPL: run_julia("@doc egg_geothermal_doublet").

Result inspection

Fimbul cases return JutulDarcy result objects. The key extra field is :Temperature on each state:

states = result.states
T_end = states[end][:Temperature]            # temperature at the final step
T_at_cell = [s[:Temperature][cell] for s in states]   # series at one cell

Well data (result.wells) and reservoir states follow the same conventions as JutulDarcy. See jutuldarcy-overview for result unpacking and jutuldarcy-wells for well construction details that apply here too.

Produced-water quantities come from the well series, not the reservoir field: result.states[end][:Temperature] is the grid; what a well delivers over time is

prod_T = result.wells.wells[:Producer][:temperature]   # K, one value per step

(keys(result.wells.wells) lists the well names of the active case.)

All quantities are SI: temperatures are Kelvin, not Celsius. When the user asks for degrees Celsius, convert (T - 273.15) before reporting; a "temperature" near 350 in a geothermal answer is almost certainly an unconverted Kelvin value.

Plotting

Fimbul reuses JutulDarcy's native plotters (GLMakie, the default backend), captured by plot_julia automatically — headless or interactive:

• plot_reservoir(case.model, result.states) — 3D reservoir (e.g. key = :Temperature)
• plot_well_results(result.wells) — well dashboard
• plot_cell_data! / plot_mesh_edges! to compose a custom 3D view
• Fimbul's own plot_well_data! / plot_mswell_values! for multi-segment wells

Just call them — no backend juggling. In an interactive session a live window opens for the user by default (window=false to suppress); pass view=true to inspect a plot yourself. For a custom 2D view, build inline against the live result object (probe keys / propertynames first).