Axial Oscillation Tools vs. Lateral Vibration Tools for Friction Reduction – What's the Best Way to Shake the Pipe?

Abstract There are many benefits to reducing friction along the drill string while drilling directional wells. Higher rates of penetration (ROP), improved tool-face control, reduced drag, and reduced stick/slip are only some of the benefits documented in previous technical papers. There are generally two types of downhole tools used to generate benign vibrations within the drill string and/or bottom-hole assembly (BHA) to reduce friction: axial oscillation tools (AOTs) and lateral vibration tools (LVTs). This paper reviews the benefits and drawbacks of each of these types of tools and presents the results of mathematical modeling and field data to conclude which type of tool is more effective at reducing friction in horizontal wells. Axial oscillation tools typically employ a valve driven by the mud flow to generate pressure pulses. A shock tool is run above or incorporated into the AOT to convert these pressure pulses into an axial oscillating motion. This motion travels up and down the drill string to reduce friction between the pipe and the borehole wall. Lateral Vibration Tools (LVTs) typically employ one or more eccentric rotating masses driven by the mud flow. This creates a vibration in the lateral direction, perpendicular to the long axis of the tool, creating motion between the tool and the borehole wall and thereby reducing friction. To investigate the potential benefits of each type of tool, a mathematical model of a BHA and drill string was created and, using finite element methods, the friction reduction effect (in terms of drag reduction) was compared between the AOT and LVT. In each scenario evaluated in the study, a benchmark calculation was first made with no oscillation. Then, the oscillation for each tool was applied and the response of the system evaluated with respect to the improvement in weight transfer along the drill string. Afterwards, the results were compared to an actual case study for verification. The research concludes that axial oscillation tools provide significantly more effective friction reduction, which enhances drilling performance in horizontal wells. The paper also provides several additional examples of comparative field results.