Formation Strength Band Lookup

Two limits worth knowing before you use this. First, published strength bands scatter widely inside every lithology, so treat the output as indicative rather than as a design value. Second, IADC series numbers classify formation hardness qualitatively — no published authority assigns compressive-strength thresholds to them, so the IADC column here is a typical-application note and not a standardised mapping. Anhydrite, chert and unconsolidated sand are shown without a band because we could not source defensible published values for them.