Agitator Tool (Axial Oscillation Tool)

What is an agitator tool?

An agitator tool, also called an axial oscillation tool, makes the drill string move back and forth in small, fast steps. The movement breaks static friction between the string and the wellbore wall, so the string slides more easily and weight on bit reaches the bit more steadily. "Agitator" is also a product name used by one vendor, so the generic name is axial oscillation tool.

‍

How does an agitator tool work?

A typical design has two parts:

• A power section: drilling fluid drives a small positive displacement motor.
• A valve section: the motor moves a valve back and forth over a fixed plate, which changes the flow area and creates pressure pulses, usually 15 to 20 times a second.

A shock tool placed just above the agitator turns the pulses into an axial movement of about 1/8 to 3/8 inch. In coiled tubing, the pulses can act on the tubing directly (AADE-11-NTCE-47).

‍

When is an agitator tool used?

• Sliding with a mud motor: in deviated and horizontal wells, where drag makes it hard to keep weight on the bit and hold toolface.
• Long laterals: where torque and drag limit how far the string can be pushed.
• Coiled tubing: where the tubing cannot rotate to break friction.

‍

Agitator tool vs shock sub

A shock sub absorbs axial shock. An agitator creates axial movement to reduce friction. They solve different problems, and they are often run together, with the shock tool turning the agitator's pressure pulses into movement.

‍

What are the limits of an agitator tool?

• It helps more of the surface weight get through friction, but the weight still starts at surface and travels down the string.
• The pressure pulses use part of the pump pressure available for the bit and motor.
• It adds length and another tool that can fail to the BHA.

‍

Where does NexTitan fit?

An agitator helps more of the surface weight get through the drag of the string. NexTitan generates the force at the bit instead. It grips the wellbore and applies weight on bit from inside the BHA, so the force at the bit does not depend on pushing weight through the string above it.

To estimate what steadier weight at the bit is worth on your section, use the drilling cost calculator.