System to control the vertical movement of a drillstring

A system for controlling the weight on a drill bit connected to a lower end of a drillstring and connectable to a drill rig having cable draw works, comprising:

• at least one fluidic cylinder and piston assembly removably and operatively connected at an upper end thereof to a support of the drill rig and at a lower end thereof to a drillstring;
• pump means for providing fluid to said fluidic cylinder and piston assembly;
• valve means for controlling the flow of the fluid to and from said fluidic cylinder and piston assembly;
• data measurement means, connected to the drillstring adjacent the drill bit, for generating a signal representative of the weight on the drill bit;
• and
• computing means, in operative communication with said valve means for controlling the operation of the fluidic cylinder and piston assembly in response to the signal received from the data measurement means to maintain the weight on the drill bit within desired limits.