ERD wells are very long (laterally) but not necessarily deep (vertically). The vertical component is the important one when assessing geothermal heat gradient. "Total measured depth" includes the lateral component, and so can be misleading when considering vertical depth. The wells you've referenced are very long, but less than 3,000 meters in vertical depth. https://www.drillingcontractor.org/erd-advances-push-limits-...