Float equipment is installed near the bottom of the casing string, typically as a float shoe (the bottommost joint) and one or more float collars (positioned 1-3 joints above the shoe). These components contain a one-way check valve that allows cement to be pumped down the casing and out into the annulus, but prevents cement from flowing back into the casing (U-tubing) after the cementing operation is complete.
Without functioning float equipment, cement would flow back into the casing, leaving a cement sheath of unknown height, compromising well integrity, zonal isolation, and potentially creating a path for formation fluids to migrate to surface.
Why Float Equipment Is Essential
Function
Importance
Preventing U-Tubing
After cement placement, the hydrostatic pressure of the cement in the annulus is higher than the displacement fluid inside the casing. Without a check valve, cement flows back into the casing, leaving the annulus uncemented.
Cement Placement Assurance
Ensures the cement top remains at the designed height. Critical for zonal isolation and regulatory compliance.
Guide Function (Float Shoe)
The rounded nose guides the casing past ledges, doglegs, and irregularities in the open hole, preventing the casing from hanging up.
Wiper Plug Landing
Float collars provide the landing seat for the bottom wiper plug during cementing, and the top wiper plug at the end of displacement.
Backpressure Control
After cementing, the closed float valve holds pressure on the formation, preventing gas or fluid influx during the cement setting period (WOC – Waiting on Cement).
Float Equipment Types
Float Shoes
Installed as the very bottom joint of the casing string. Combines a guide nose with an integral float valve.
Type
Description
Application
Float Shoe (Ball Valve Type)
Round nose with a spring-loaded ball check valve. Most common
Standard onshore and offshore wells
Float Shoe (Flapper Valve Type)
Round nose with a spring-loaded flapper check valve. Larger flow area than ball type
High flow rate cementing jobs, large-diameter casing
Float Shoe (Plunger / Poppet Valve)
Guided plunger with spring return. Positive sealing
Slimhole, small-diameter casing
Double Valve Float Shoe
Two check valves in series (primary + backup). If one fails, the second holds
Critical wells requiring highest reliability
Non-Rotating Float Shoe
Nose profile designed to prevent bit rotation during drill-out. Reduces bit wear
Where shoe must be drilled out with PDC bits
High-Flow Float Shoe
Large internal flow area for high-rate cementing
Large-diameter casing, deepwater
Self-Fill Float Shoe
Allows casing to fill with drilling fluid while it is being run in the hole. Valve closes when circulation starts
Reduces surge pressure during casing running. Prevents formation breakdown
Stage Cementing Float Shoe
Used with stage cementing collars for two-stage cement jobs
Long casing intervals, lost circulation zones
Float Collars
Installed 1-3 joints above the float shoe. Provides a secondary check valve and the landing seat for cementing wiper plugs.
Type
Description
Application
Float Collar (Ball Valve)
Standard spring-loaded ball check
Most common. Backup to float shoe
Float Collar (Flapper Valve)
Spring-loaded flapper. Large flow area
High-rate cementing
Double Valve Float Collar
Two check valves in series
Increased reliability
Latch-Down Float Collar
Check valve is latched into place and locked. Cannot be pumped out
Critical wells. Eliminates risk of valve displacement
Non-Rotating Float Collar
Internal profile prevents bit rotation during drill-out
PDC bit friendly
Self-Fill Float Collar
Allows casing to fill while running. Closes on circulation
Managed pressure, surge control
Stage Cementing Collars (DV Tools)
Allows the cement job to be performed in two or more stages. Used when the cement column height would fracture the formation if pumped in a single stage, or when selective zonal isolation is required.
Type
Description
Hydraulic Stage Collar
Opened by applied pressure after the first stage cement is displaced. Cement is pumped through the open ports into the annulus. Closed by a closing plug
Mechanical Stage Collar
Opened by a mechanical shifting tool on drill pipe or workstring
Integral Stage Collar
Combined float collar and stage tool in one assembly
Guide Shoes
A simple rounded nose at the bottom of the casing string. Unlike a float shoe, a guide shoe has no check valve. It only guides the casing past obstructions and does not prevent backflow.
Type
Description
Plain Guide Shoe
Simple rounded profile. No valve
Internal Bevel Guide Shoe
Beveled internally for smooth drill-out
Bull Nose Guide Shoe
Blunt, heavy nose for tough hole conditions
Note: Guide shoes are used when float equipment is located in float collars above, or in non-cemented casing strings (liners, some intermediate strings where backflow is not a concern).
Float Equipment Material & Construction
Component
Material Options
Body / Shell
API 5CT grade matching the casing string (L80, N80, P110, etc.). Alloy steel for HPHT
