Patent ID: 7628229
Filing Date: 2009-12-08
Classification: E21B

Abstract:
1. A mobile drilling rig, comprising: a carrier frame adapted for selective attachment to one of a first dolly assembly and a second dolly assembly, the carrier frame having a rearward portion and an opposing forward portion for connecting to a powered tractor; a mast pivotally connected in a lowered position to the rearward portion of the carrier frame during transport and raised to an operative position over a well; a top drive supported on the mast when in an operative position and moveable along the mast; a coil tubing injector supported on the mast when in an operative position for injecting coil tubing into the well; the first dolly assembly supporting at least a portion of the carrier frame when attached thereto, the first dolly assembly comprising a first plurality of wheels on a first plurality of axles, the first dolly assembly adapted for selective attachment to and detachment from the rearward portion of the carrier frame; and the second dolly assembly supporting at least a portion of the frame when attached thereto, the second dolly assembly comprising a second plurality of wheels on a second plurality of axles, the first plurality of wheels on the first plurality of axels differing in at least one of number and spacing from the second plurality of wheels on the second plurality of axels, the second dolly assembly adapted for selective attachment to and detachment from the rearward portion of the carrier frame.