Casing and cement is needed to prevent caving in the hole; protect freshwater zones from pollution; exclude water from the producing formation; and permanently seal off high-pressure zones, zones of lost circulation, and other troublesome formations. This video follows the progress of a well and crew as the casing string is run and cemented, then cuts away to a Halliburton lab and classroom when explanations are needed to cover the basic theory and the equipment and procedures involved in cementing an oil or gas well in an informative and dramatic manner