To suspend drilling operations while allowing cement slurries to solidify, harden and develop compressive strength. The drilling crew usually uses this time to catch up on maintenance items, to rig down one BOP and rig up another one for the new casing, to get tools and materials ready for the next hole section, and other non-drilling tasks. The WOC time ranges from a few hours to several days, depending on the difficulty and criticality of the cement job in question. WOC time allows cement to develop strength, and avert development of small cracks and other fluid pathways in the cement that might impair zonal isolation.