ccl logging of the open borehole 22 will then continue as the drill pipe 20 is withdrawn until the casing shoe 23 is reached at which stage the calliper arm 45 will close fig7 again by use of induction measurement and casing collar locator the logging operation is then completed with the data being recorded inside the logging tool 40 a repeat section can be made once the calliper 45 has closed the mud flow 26 is then reversed as indicated by arrows 260 and this reverse mud flow will lift the tool string incorporating the logging tool 40 and the tool 40 will be received and captured in holding device 30 23 with appropriate reverse flow pressures the tool 40 may be received at the well head from a depth of 10 000 ft in approximately 50 minutes and data can be downloaded in approximately 10 to 20 minutes the method according to the present invention has several advantages over known systems firstly by forcing the logging tool 40 to the bottom of the well 10 inside the drill pipe 20 the tool 40 is protected from any wash out regions as it passes down the pipe 20 when the logging tool 40 reaches the end of the drill pipe 20 it is still fully within the drill pipe 20 the drill pipe 20 is withdrawn from the logging tool 40 the logging tool 40 thereby remaining stationary relative to the well 10 the calliper 45 and the sensoring end of the logging tool 40 will therefore not have to be forced into an open bore and therefore will be protected at all times.