The Valhall chalk reservoir is weak and started to compact when oil production began in 1982. The reservoir compaction soon was observed at the scafloor in the form of seafloor subsidence. As reservoir depletion, compaction, and subsidence continued into the 1990s, drilling strategies were developed to handle the reduction in fracture gradient as well as high-angle extended-reach-drilling (ERD) wells in the overburden. An important factor for the drilling teams in their decision-making process has been development of wellbore-stability models and integration of drilling engineering, rock mechanics, and subsurface technology. The full-length paper details the drilling history at Valhall.