PDF™ (Pressure Differential Equipment) Float Collars and Shoes
Allows casing fill while running in hole (RIH), permits circulation without losing the self-fill option.
Halliburton’s Pressure Differential Fill (PDF™) float collars and shoes allow operators to maintain a constant fluid height inside the casing of a well. As fluid is allowed to enter through the bottom of the casing, the system maintains a constant differential pressure between the inside and outside of the casing at the floats to ensure constant fluid height within the casing.
PDF floating equipment is supplied in the differential fill mode and is ready to be RIH. After all casing runs have been completed, the differential fill option is deactivated by dropping a weighted plastic ball from the surface and pumping the ball through the tool. After the ball passes the float collar and/or shoe, the PDF valve is converted to a one-way cementing valve that allows cement to flow into the annulus, where it is prevented from re-entering the casing.
A spring-loaded valve in the fill-up unit regulates filling. When hydrostatic pressure outside the casing exceeds the spring tension, fluid is allowed to enter the casing; when pressure inside the casing combines with spring tension to exceed the pressure outside the casing, the valve closes. The differential pressure between the inside and outside of the casing is the sum of the spring rates of all PDF floating equipment in the casing string. The hole may be circulated at any time while casing is run without affecting the fill-up unit.
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