Mobile hydraulic workover rig

Abstract

A rig including a base structure, a derrick extending from the base structure, a hydraulic lift cylinder connected to the upper end of the derrick, a lower slip assembly connected to the base structure, an upper slip assembly, and at least two snub cylinders connected to the base and the upper slip assembly. A distal end of a piston rod of the lift cylinder is connectable to a pipe string extendable through the upper and lower slip assemblies such that both a lifting force and a snubbing force may be applied simultaneously to the pipe string.

What is claimed is: 
     
         1 . A rig for raising and lowering a pipe string, comprising:
 a base structure;   a derrick extending from the base structure and having an upper end; and   a single hydraulic lift cylinder including a cylinder and a piston rod, the cylinder having an upper end and a lower end, and the rod having a proximal end and a distal end, the lower end of the cylinder being fixed to the upper end of the derrick and the rod extending downwardly from the lower end of the cylinder and movable between a retracted condition and an extended condition,   wherein the piston rod of the lift cylinder is axially aligned with the pipe string when the piston rod is connected to the pipe string.   
     
     
         2 . The rig of  claim 1 , wherein the base structure includes a first row of storage containers and a second row of storage container arranged in a parallel, spaced relationship to the first row of storage containers. 
     
     
         3 . The rig of  claim 2 , wherein each of the storage containers has a rectangular configuration, wherein the storage containers of the first row of storage containers are arranged in an end-to-end relationship, and wherein the storage containers of the second row of storage containers are arranged in an end-to-end relationship. 
     
     
         4 . The rig of  claim 2 , wherein the first row of storage containers is slidably mounted on a first skid, and wherein the second row of storage containers is slidably mounted on a second skid. 
     
     
         5 . The rig of  claim 2 , wherein the base structure further comprises a work platform mounted on the storage containers, and wherein the derrick includes a base member mounted on the work platform centrally between the first row of containers and the second row of containers. 
     
     
         6 . The rig of  claim 5 , wherein the derrick is supported by the base member, and wherein the base member is movable relative to the work platform. 
     
     
         7 . The rig of  claim 6 , wherein the first row of storage containers is slidably mounted on a first skid, and wherein the second row of storage containers is slidably mounted on a second skid. 
     
     
         8 . The rig of  claim 1 , wherein the derrick has an open side extending from an upper end to a lower end thereof.