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 installation of a cemented steel cased well wherein the
drill string and the drill bit are cemented into place during one single
drilling pass down into the earth. Methods are provided to selectively
cause a drilling trajectory to change during drilling with casing. A
one-way cement valve is installed near the drill bit of the drill string
that allows the cement to set up efficiently under ambient hydrostatic
conditions while the drill string and drill bit are cemented into place
during one single drilling pass into the earth.