Quick check for the historians here: was the first recorded electrical resistivity log run at Pechelbronn in Alsace in 1927, before SP became standard, or am I missing an earlier field test? I’m chasing down the original plot to show how the resistivity contrast flagged a water leg vs oil pay, and would love a citation or scan if you’ve got one.
Pechelbronn, 1927 is the canonical first resistivity log — Schlumberger called it “electrical coring”; the SLB history page has the scan: https://www.slb.com/about/our-history/1920s/first-well-log. The go-to citation is Marcel Schlumberger (1929), “Electrical Coring” (Trans. AIME), though a few sources mention a 1926 field trial that wasn’t the full commercial run.