Milling of cast iron bridge plug

Challenge
Water shut-off
MIL.OFF.ABZ.10.03.V1 MILLING OF CAST IRON BRIDGE PLUG
  • Total operational time 67 hours (rig up to rig down)
  • Actual milling time 9 hours
  • Unique operation All milled material was recovered

Background

An operator in the UK needed to remove a cast iron bridge plug at 15,000 ft. The well was a gas producer with a high water-cut and a low bottom hole pressure of 2,000 psi and therefore continued gas production was threatened by water ingress. Well test figures were 0 BOPD, 781 BWPD and 15-9 MMscf/D. A PLT carried out indicated that all water production was coming from a depth below 16,295 ft. From this data, it was proposed to set a permanent bridge plug at 16,280 ft MD (Measured Depth).

However, the attempt to set the cast iron bridge plug was unsuccessful due to a setting tool failure. The tool string freefell for 50 ft, which caused the bridge plug to be set at 16,200 ft MD - 80 ft too high.

Operation

The Well Miller® and Well Tractor® were chosen to mill out the plug on electric wireline, which was a world’s first. This technology was chosen due to:

• Avoiding any additional fluid handling associated with CT milling operations

• Personnel and deck space restrictions prevented a CT operation on short notice

• Loss in potential well production was costing +USD 115,000/day

Achievements

Value-creation: Investment returned quickly due to increased production. The challenges of controlling rate and milling penetration were overcome.

Using Welltec’s technology significantly reduces environmental risks. Due to the light design, the Well Tractor reduces fuel consumption and greenhouse gas emissions associated with transporting heavy equipment into environmentally sensitive areas.

BOPD*
Before: 0
After 60

BWPD**
Before: 781
After: 0

*Barrels of Oil Per Day **Barrels of Water Per Day