One of the challenges in cleaning or milling long lateral wells is getting coiled tubing to the target depth.
As the pipe gets deeper into the well, it starts to experience more friction, and more force is required at the surface to continue running in the hole.
At the same time pipe starts to buckle and the contact area and normal force between the casing and the coil start to increase and this increases frictional force even further.
In many cases, chemical friction reducers (lubricants) are used to decrease the friction coefficient between the pipe and the casing or open hole.
However, on deeper wells, it is usually not enough and that’s why agitators are used.
Most downhole agitators work by momentarily stopping the flow of fluid through the coiled tubing which creates a pulse that shakes the coiled tubing string and allows it to get a little deeper in the well.
During coiled tubing jobs, it is usually pretty clear at the surface whether the vibrational tool is working because the is pipe shaking.
However, if a weaker vibration tool is used it might be more challenging to know if the tool is still working unless there is eline in the coil that transmits downhole data back to the surface.
To decide whether an agitator is required, usually coiled tubing simulations are performed before the job.
Related: What is Coiled Tubing?
Things to Keep in Mind When Using Downhole Vibration Tools
Whenever using an agitator it is important to take into account the increase in pumping pressure created by the vibrating tool.
In addition depending on the agitator that is used, you might be restricted to what size of solids can be pumped through the tool.
This is might be an issue if you are planning to pump some type of diverting material or sand.
There is also the potential for vibrational tools to damage surface equipment if a strong tool is used close to the surface.
That’s why in some cases weaker vibration tools are used if the well is not very deep.
Not every agitation tool is able to handle straight gas like nitrogen and the ones that can are not always able to provide enough friction reduction because gasses are highly compressible.
Another option to get the pipe deeper in the well without using agitators is a downhole tractor that pulls the pipe into the well.
Read next: Coiled Tubing Bottom Hole Assembly (BHA) Components