Abstract An integrated approach to evaluating the causes of severe wellbore instability in the Cusiana field is described. The field is located in a tectonically active region of Colombia. Deterioration of the hole during drilling operations has led to excessive nonproductive time and expensive wells. The scale of the problem is unprecedented in the world. In wells costing tens of millions of dollars, millions per well could be attributed to poor hole conditions. This paper describes how the problem was addressed and what actions were taken to improve operational performance, resulting in reduced drilling costs. The improved understanding has contributed to better well planning, and improved drilling performance, and has underlined the need to consider all aspects of the drilling process to achieve improved hole conditions in a difficult geological setting.