Patent ID: 8118114

Claim:
A downhole steering tool configured to operate in a borehole, the steering tool comprising: at least three blades deployed on a housing, the blades disposed to extend radially outward from the housing and engage a wall of the borehole, said engagement of the blades with the borehole wall operative to eccenter the housing in the borehole; a hydraulic module including a fluid chamber disposed to provide pressurized fluid to each of the plurality of blades, the pressurized fluid operative to extend the blades, each of the blades including at least a first valve in fluid communication with high pressure fluid and at least a second valve in fluid communication with low pressure fluid, each of the blades further including a pressure sensor disposed to measure a fluid pressure in the blade and a position sensor disposed to measure a radial position of the blade; and a controller configured to (i) lock at least one of the blades in a predetermined radially extended position by closing both the corresponding first and second valves, (ii) receive pressure measurements for each of the locked blades from the corresponding pressure sensors; and (iii) radially further extend or retract at least one of the locked blades by opening the corresponding first valve when the corresponding pressure measurement is less than a first predetermined threshold or opening the corresponding second valve when the corresponding pressure is greater than a second predetermined threshold.