Abstract: A method and apparatus for completing and backside pressure testing petroleum product wells for production, with one or more differential pressure valves being present at spaced intervals within a tubing string and with a well fluid transfer device being located in the tubing string. Either after or preferably before well casing perforation, after setting of the tubing string, casing pressure is elevated to a backside test pressure, above differential pressure causing closure of the differential pressure responsive valves to ensure the integrity of seals and packers. Casing pressure is then increased to a transfer valve opening pressure, above backside test pressure, to open unidirectional flow communication of well fluid from the well casing to the production tubing.