The shape of the shoe (usually tapered or rounded) helps the casing to penetrate the well easily, even if the well is uneven or curved.
Protecting the casing from damage.
The shoe prevents the pipe from hitting and jamming as it travels downhole, reducing the risk of casing deformation.
Direction of mud circulation.
Many shoes have check valves that allow drilling fluid to flow out of the string, but do not allow fluid back in. This helps prevent clogging of the pipe and ensures efficient cementing.
Facilitating the cementing process.
When cementing a well, the shoe helps distribute the cement slurry evenly around the casing, ensuring the pipe is securely anchored in the rock.
Preventing casing clogging.
The inner channel of the shoe serves to protect the casing from drill cuttings and other contaminants during the running process.
Types of shoes:
Guide shoe - has a rounded or tapered tip, used to facilitate running the string.
Shoe with check valve - prevents drilling fluid from flowing back into the string, which is especially important during cementing.
Milled shoe - made of materials that can be easily drilled out after cementing is complete.
Where used:
When drilling a well - to facilitate running the casing string and prevent it from getting stuck.
When cementing casing - to evenly distribute the cement and prevent it from getting inside the pipe.
When cementing the well - to create a strong barrier between the casing and the well wall, preventing the flow of fluids between formations.
Advantages of use:
Reduces the risk of casing getting stuck while running.
Provides tightness and strength during cementing.
Controls mud circulation and prevents pipe contamination.
Simplifies downhole operations, reducing the risk of accidents.