Fervo_Project_Cape-4 Stimulation Costs Update

[softwareengineerprogrammer]

Description

1. Adjust Fervo_Project_Cape-4 stimulation cost to $4.6M per well.
   1. Started with baseline stimulation cost of $4M per well based on informal discussions with experts which indicated $2M/well is a significant underestimate and that current rule of thumb is that stimulation costs approximately the same as drilling.
   2. $4M/well baseline cost corresponds to ~$39k/frac stage for 102 stages, which corroborates with high-intensity U.S. shale costs (Baytex Energy, 2024; Quantum Proppant Technologies, 2020), which are the closest technological analogue for multi-stage EGS (Gradl, 2018).
      1. Average Shale Well Cost (Operated; drilling, completion, equipment, and tie-in) = $10.5M (Baytex, p. 16)
      2. "frac stimulation and completion programs, [together] account for up to 70% of total well costs." (Quantum, p. 2)
      3. $10.5M * 0.7 = $7.35M
      4. Assuming ~16m spacing, a 9800 foot lateral requires 187 stages.
      5. $7.35M/187 = $39,270 per stage
   3. The baseline assumes standard sand proppant. The 15% contingency (~$0.6M) accounts for the necessary upgrade to ceramic proppant, which is required to resist mechanical crushing and geochemical degradation (diagenesis) over a 30-year well life at 200°C (Ko et al., 2023; Shiozawa & McClure, 2014).
   4. $4.6M/well aligns closely with with Project InnerSpace's 1 GW data center cost model drilling:stimulation cost ratio of 46%:54% (Yusifov & Enriquez, 2025):
2. Removed 15% inflation during construction hedge since we'll consider the unexpectedly-higher stimulation costs to have eaten it. (Inflation during construction is now $59.82M as dictated by 1-year construction time + 2.3% inflation rate)

Documentation

Testing & Verification

1. Regenerated example result
2. Updated case study documentation test accordingly
3. Input/result on web interface: https://gtp.scientificwebservices.com/geophires/?shared-geophires-result-id=0f092c73-1108-4b2c-ad12-d456eead26c7

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TODO:

1. Communicate that this is a new version (CHANGELOG entry, or mayyyybe break off as new Fervo_Project_Cape-5 example...)
2. markdown documentation unit test for stimulation costs: 9785819
3. double-check project payback period: created separate issue: Remove or clarify SAM-EM project payback period NREL/GEOPHIRES-X#413

[softwareengineerprogrammer]

Closing in favor of NREL#414. I want to get SME approval on this one before merging it into my fork's main branch (unlike most PRs where I feel confident enough to merge fork PR into main and then cut PR to main repo from my fork)