Floating hoop and shoes are the key tools for casing cementing operation, and their core functions and characteristics can be summarized as the following five aspects:

I. Core Functions

Guiding casing into the well

Floating shoes are located at the end of casing column, and the hemispherical design can effectively guide the casing string to be lowered smoothly and reduce the friction resistance with the well wall, which is especially suitable for complex borehole trajectories.

Adjusting buoyancy and sealing to prevent backflow

The buoyancy of the casing string is automatically balanced by an internal check valve, which reduces the pressure on the bottom of the well from its own weight.

After cement injection is completed, the pressure return valve closes to prevent cement slurry or drilling fluid from flowing back into the casing, ensuring the integrity of the cement ring.

Cement plug height control

The floating hoop serves as a rubber plug touching seat, which can accurately limit the height of the cement plug in the casing to ensure the quality of cement bonding in the casing shoe area.

Plug Support and Pressure Indication

When injecting cement, the floating hoop provides the position of the rubber plug touching pressure, and confirms the completion of cement slurry injection through the signal of sudden increase of pump pressure.

Structural design features

Drillability and adaptability of diameter

Internal components (e.g. spool, spring, etc.) are designed with drillable materials, and the through diameter is consistent with the casing, which is convenient for subsequent drilling and removal operations.

Anti-rotation design optimization

The anti-rotation floating shoe is optimized to enhance drilling efficiency through the combination of the internal anti-rotation flower head and anti-rotation rubber plug, which is suitable for PDC drilling operations.

Material Strength and Sealability

The material strength is equivalent to API P-110 steel grade, which meets the requirements of high-pressure well conditions.

Vulcanized rubber spool and alloy valve seat form a reliable seal, resistant to acid and alkali corrosion and high temperature.

Application Scenarios

Adaptability to complex well conditions

By improving the spool material (e.g. alloy or high-temperature resistant composite material), the floating shoe can be used in ultra-deep wells, horizontal wells and other complex wells.

Matching use specification

Floating shoes are usually installed at the bottom of casing columns, while floating hoops are connected at intervals of 1-2 pieces of casing to form a double holder, which is the core tool in drilling and cementing engineering, mainly used to maintain the centered position of drilling tools or casing, optimize the trajectory of wellbore and improve the quality of work. Its function and design can be divided into the following categories according to the differences in application scenarios:

I. Functional Classification

Drilling tool centering device

Anti-slope and azimuth control: control the trajectory of the borehole by increasing the rigidity of the drilling tool combination, act as a pivot point to change the force state of the drilling tool in the slope-increasing and slope-decreasing sections, and stabilize the slope and azimuth of the well.

Vibration reduction and protection of instruments: Stabilize the position of MWD (Measurement with Drilling) instruments, cushion lateral vibration, and reduce measurement error and equipment loss.

Trimming the well wall: smoothing the curvature change of the borehole and ensuring the regularity of the wellbore.

Casing Corrector

Centering casing: Ensure the casing column is centered in the wellbore, so that the cement ring is evenly distributed and the cementing quality is improved.

Reducing lowering resistance: Reduce the friction between casing and well wall through the structure of rollers and spring plates to avoid the risk of sticking and jamming.

Adapt to complex wells: Adjustable design (such as the spring plate bending degree adjustment in the patent) meets the needs of oil wells of different diameters and adapts to horizontal wells, large displacement wells and other complex working conditions.

Structure type

Spring Type Corrector

Adopting riveted or articulated spring plates, the initial outer diameter matches with the casing coupling, and after being lowered into the casing, it expands through the spring return force to realize dynamic diameter change.

Rigid righting device

Like a lantern-shaped frame, it provides stable support through high-strength composite materials and is commonly used in high-pressure or high-temperature well sections.

Intelligent Adjustment

Integrated adjustment mechanism (such as the mounting groove and roller in the patent) can adjust the bending degree of the spring sheet in real time to optimize the effect of drag reduction.

Application Scenarios

Conventional boreholes: Standardized spring plates or rigid hold-downs to meet centering and anti-slope requirements.

Special Boreholes

Horizontal wells/large displacement wells: give priority to adjustable diameter or wear-resistant rollers to reduce casing string friction.

High-temperature and high-pressure wells: adopt alloy reinforced structure to withstand extreme environment.

Instrument protection: Installation of a holder in the MWD instrument section ensures that the sensor is centered and prolongs the life of the equipment.

The design and selection of the correcting device need to take into account the well depth, well type, formation characteristics and operating costs, in order to achieve a balance between safety and economy. Anti-backflow protection.