The steel drill string attached to a drilling bit during typical rotary drilling operations used to drill oil and gas wells is used for a second purpose as the casing that is cemented in place during typical oil and gas well completions. Methods of operation are described that provide for the efficient...http://www.google.de/patents/US7040420?utm_source=gb-gplus-sharePatent US7040420 - Methods and apparatus for cementing drill strings in place for one pass drilling and completion of oil and gas wells
