PNEUMATIC HAMMER DRILLING ASSEMBLY FOR USE IN DIRECTIONAL DRILLING

摘要

A drilling assembly and a method for directional drilling using the drilling assembly. The drilling assembly comprises a drilling bit, a near bi t stabilizer and an adjustable gauge stabilizer. The near bit stabilizer is located a fir st axial distance from a distal end of the drilling assembly and has a near bit stabilizer gauge which is greater than a nominal drilling assembly gauge. The adjustable gaug e stabilizer is located a second axial distance from the distal end, which is greater than the first axial distance, and is adjustable between an extended and retracte d gauge. The retracted gauge is less than the near bit stabilizer gauge. A bit drop angle is created between the drilling assembly and the drilling bit, while a stabiliz er angle is created between the near bit stabilizer and the adjustable gauge stabilizer. The combination of the bit drop angle and the stabilizer angle results in a net build angle of the drilling assembly, when the adjustable gauge stabilizer is adjusted t o the retracted gauge, and a net drop angle when adjusted to the extended gauge.