Self filling float provides barrier on demand
22 October 2012
Churchill Drilling Tools’ self-filling float provides an effective barrier on demand and reduces costly intervention, combats pressure surge and is set to enhance global drilling practices following successful deployments in the North Sea.
The self-filling float is being used by two major operators in varied applications in the region. Churchill’s patent pending Self-Filling Float allows the operator to select the timing of float activation. Formation damage from running into hole (RIH) surge pressures can be avoided with the float in the open position and full pumping capability is retained at all times
A steel dart is dropped while the final few stands are RIH. A pressure cycle activates the float and stores the dart in the core chamber. Optimized internal geometries and high durability surface finishes ensure pressure loss is minimal and the float can handle any anticipated flow rate.
Pumping is possible in dormant mode without risk of activating the tool, allowing shallow hole tests to be performed with no danger of the floats becoming inadvertently activated.
At the appropriate time, the dart is dropped into place. When the pumps are turned on, pressure immediately rises as the dart presses down on the seat.
The dart continues to experience increasing pressure until its sleeve pins shear, allowing it to fall towards the storage core, where it forms a low profile centralized 'bullet' around which flow can freely pass through the floats and onto the bit.
“The aim of a float is to create an effective safety barrier for the rig within the drillpipe, and while we all welcome anything that increases safety, traditional floats do have operational drawbacks. They can require a top-filling intervention when they create a vacuum in the pipe, and they will also add to surge pressure on the formation,” said Churchill Drilling Tools’ director, Mike Churchill. “The self-filling float is an effective and practical solution. It enables operators to comply with safety requirements yet gives them the choice of when to activate.”
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