Casing While Drillng "CWD" The concept of drilling and casing the hole in the same time is, of course, valuable by combining two time consuming processes. So the main purpose of Casing Drilling, or Casing while Drilling (CwD), is to eliminate classic casing runs and isolate formations while drilling. By using Standard casing string instead of conventional drill string, the drilling and casing are executed simultaneously, section by section. Casing while Drilling is also a hazard mitigation solut