Top drive drilling apparatus with improved wrench assembly

摘要

A top drive well drilling apparatus, having a drive unit for rotating a drill string. The drive unit is connected to a carriage, which guides the drive unit along a vertical guide track. A wrench assembly, for making and breaking connections between the stem of the drive unit and the drill string, can be moved between a working position along the stem and a retracted position away from the stem. The wrench assembly can also be moved vertically, and is mounted on the carriage.