Patent ID: 8607897

Claim:
A gas turbine drill tool for minimizing formation damage during drilling and well servicing applications, comprising: (a) a housing configured to couple to a source of pressurized gas; (b) a turbine assembly disposed coaxially within the housing, the turbine assembly including a turbine shaft configured to rotate relative to the housing in response to a flow of pressurized gas through the housing, the turbine shaft defining an open ended hollow central volume; and (c) a differential planetary gear transmission disposed coaxially within the housing, the differential planetary gear transmission being configured to receive an input from the turbine shaft and produce an output having a relatively lower speed and larger torque relative to the input provided by the turbine shaft, the differential planetary gear transmission including an annular volume along a central axis of the differential planetary gear transmission, the annular volume being configured to accommodate the turbine shaft, enabling a portion of the drill tool distal of the differential planetary gear transmission to be placed in fluid communication with the central volume in the turbine shaft.