Offshore oil and gas well drilling rig

Claim 1

An offshore oil and gas well drilling rig comprising, in combination an offshore drilling platform a drilling mast supported by said offshore drilling platform and having an upper section and a lower section the upper section of said drilling mast being rotatably disposed on the lower section thereof a draw-works including a draw-works winch and an auxiliary winch disposed on said offshore platform at the foot of the lower section of said drilling mast a crown block mounted on the upper portion of said drilling mast adjacent the top thereof a pair of pivot supports secured to the lower end of the upper section of said drilling mast and oppositely disposed with respect to one another a load boom having its inner end pivotally connected to one of said pivot supports a balance boom having its inner end pivotally connected to the other of said pivot supports a load sheave block carried by said load boom a suitably operated positioning line connected to said load sheave block for horizontally moving the latter along said load boom a load boom topping lift mounted adjacent the upper extremity of the upper section of said drilling mast a lifting cable connected to said load boom, trained over said load boom topping lift, and directed downwardly through said drilling mast for attachment to said auxiliary winch a balance boom topping lift mounted adjacent the upper extremity of the upper section of said drilling mast a lifting cable connected to said balance boom, trained over said balance boom topping lift, and directed downwardly through said drilling mast for attachment to said auxiliary winch and a draw-works line connected at one end to said draw-works winch said draw-works line being passed around said crown block and downwardly through said drilling mast to carry a travelling block, swivel and kelly or alternatively said draw-works line being directly attached to said load sheave block for raising and lowering the load carried thereby.