Preliminary fractal analysis of fracture spacing inferred from an acoustic televiewer log run in the Basel-1 geothermal well (Switzerland)

Development of a geological model for an Enhanced Geothermal System (EGS) reservoir requires a characterization of the fracture network. Previous studies have identified fractures from an acoustic
image log run in the crystalline basement section of the Basel-1 well and described fracture sets and fracture zone characteristics. Using the Cantor’s Dust method, we investigated the fractal behavior of four major natural fracture sets intersected by the Basel-1 well. These sets are differently distributed between 2600m and 5000m
(i.e., the logged depth) along the well below the rotary table of the rig. The obtained fractal dimensions (D) vary between 0.35 and 0.60 for the four fracture sets. Similar D values ranging for sets 1–3 in the interval between 2600m and 3000m emphasize the role of the geological setting in the distribution of fractures. Moreover, the
spacing distribution of sets 2 and 3 show a clear power-law distribution.

, 2023