Under-reaming is used to allow a wider clearance for running and cementing casing correctly as a result of poor wellbore quality. Active under-reamers are typically employed. ECR fulfils this requirement for limited enlargement needs without the complexity and cost of active tools.
- Cutting structure on active blades provides near gauge hole enlargement
- Blade ends with tungsten carbide dome inserts for easier run-in-hole inside casing
- Blade mid-section with hard facing pads for casing protection
- Spiral blades provide 120 coverage for smoother drilling
- Large mud-ways provide around 60% of annulus area for flow-by