Unique Axial Oscillation Tool Enhances Performance of Directional Tools in Extended Reach Applications

Abstract The effect of having an axial oscillation generator tool (AGT) in the drill string has been demonstrated to be the difference between the premature termination of drilling a section and successful completion of the section to planned TD. The AGT tool has traditionally been used in commercial applications where sliding with steerable motors has been problematic. Axial oscillation in the drill string is generated through a series of pressure pulses coming from one part of the AGT. The pressure pulses act on the pump open area of the shock tool, generating the axial motion required to reduce friction, improve the weight transfer to the bit, reduce reactive torque (and thus overall) downhole torque. The hydraulic vibration also enhances the performance through reducing friction. Combined together, the hydraulic vibration and the axial vibration have proven extremely effective in reducing friction and improving weight transfer with steerable motor assemblies. This had led to increase step-out capabilities, improved tool face control, reduced vibration, and higher penetration rate. This paper provides an overview of the tool technology and application with motors. However, it also focuses on expansion of the tool application with both conventional rotary and also rotary steerable BHA’s. Test results discussed include; A study on rotary drilling with AGT to evaluate and quantify improvement in weight transfer to the bit, revealing significant improvement in DWOB and reduced torque-at-bit.Overview of the compatibility of the AGT with rotary steerable system (RSS) and MWD tools, in particular the dynamic of the AGT which influences the weight transfer. Significant improvements in drilling performance are revealed when combining AGT and RSS. Case studies are included, displaying the breadth of benefits with the AGT with all forms of drive systems (rotary, motor, and RSS).