Method and device for making geophysical measurements within a wellbore

A device for making geophysical measurements within a wellbore comprising:

• drive means disposed at the ground surface;
• traction means within the wellbore and operatively connected to said drive means so that said drive means controls continuous displacement of said traction means within the wellbore;
• at least one double-acting jack having two moving portions, one of said moving portions being operatively associated with said traction means so that said one moving portion is displaced with said traction means, and the other of said moving poirtions is relatively movable with respect to said one moving portion so that said other of said moving portions is non-continuously displaceable with respect to said wellbore;
• at least one measuring tool operatively associated with said other of said moving portions so that said at least one measuring tool is displaceable with said other of said moving portions;
• and
• means for controlling the relative displacement between said two moving portions of said jack;
• so that said traction means is displaced in continuous motion with the speed of displacement controlled by said drive means, said double-acting jack is adapted to provide the measuring tool with a relative velocity which is equal and opposite to the absolute velocity of traction means for reducing the absolute velocity of the measuring tool to zero during measurement periods, and said measuring tool is provided between two consecutive measurement periods with a relative velocity which is in the same direction as the absolute velocity of said traction means so that the absolute velocity of said measuring tool is higher than the absolute velocity of said traction means.