Reasons for Using Cementing Plugs
• Remove mud sheath
• Separate cement and Mud
• Prevent over displacement
• Surface indication
• Pressure test casing
Five Wiper Cementing Plugs
• Available with:– aluminum inserts
– plastic inserts
– non-rotating (NR) plastic inserts
• 350 psi rupture diaphragm in bottom plugs
• Surface release or sub-surface release (SSR)
• Compatible with water-based or oil-based muds
NR Cement Plug System
• Reduces drillout time
• PDC drillable
• 350 psi rupture diaphragm
• Use with NR float collar
• All plastic inserts
Pumping Cement without Cement Plugs
• Much cement contamination
• No surface indication of cement placement
Displacement fluid
Cement
Casing
Mud sheath
Drilling mud
Pumping Cement with Top Plug Only
• Top plug wipes mud sheath from casing ID
• Separates cement from displacement fluid
• Surface indication when cement placement is complete
• Require additional shoe track length
Casing
Top plug
Accumulatedmud
Mud sheath
Drilling mud
Accumulated Mud Volume Ahead of Cement Plug
Fill up per 1,000 ft. casing
1/16 51 ft. 40 ft. 28 ft. 20 ft.
1/32 25 ft. 20 ft. 12 ft. 10 ft.
1/64 13 ft. 10 ft. 7 ft. 5 ft.
Mudsheath
thickness(Inches)
5-1/2 inchcasing
7 inchcasing
9-5/8 inchcasing
13-3/8 inchcasing
Pumping Cement with Top & Bottom Plugs
• Preferred method
• Bottom plug wipes mud sheath from casing ID
• Surface indication when cement placement is complete
• Maximum cement/mud separation
Displacementfluid
Top plug
Accumulatedmud
Casing
Drilling mud
Cement
Bottom plug
Polycrystalline Diamond Compact Bits (PDC)
• Soft – medium formations
• Improves rate of penetrate (ROP)
• Longer service life