Oil Search well ADD-5 on Papua New Guinea, August 2009
Challenging environment for testing the NSD system because:
- Foam drilled 17 ½” section 200m to 1500m
- Injected foam fluid - 2000 scfm air, 32gpm water, 1% foaming agent, 2 lb/bbl Barazan D
- Maximum standpipe pressure of 1600 psi
- Maintained constant circulation over whole section, 28 drill pipe connections
- The NSD valves were in the open hole
- Hole angle 20 degrees inclination
- Extreme vibration due to shallow drilling depth
- Seal off against 1600psi compressed air pressure
- Drilled solids contaminated environment, with cuttings not suspended in lubricating and viscous mud
The NSD system allowed Oil Search to accomplish the following:
- Drilling with stands, compared to drilling in doubles conventionally due to need to make connections one single off bottom.
- Reduced connection time from 35-45 mins to only 10-15 mins, by eliminating need to depressurise the drillpipe, and re-establish stable foam circulating conditions after each connection.
- Elimination of high injection pressure spikes up to 2500psi, experienced during conventional foam drilling connections.
- Substantial risk reduction of stuck pipe during connections, due to drilled solids drop out, or formation collapse due to cyclic pressure variations in the wellbore.
- No stuck pipe incidents.
- Allowed section to be drilled to planned TD. On conventional foam and air drilling jobs, circulation can not be re-established after a connection beyond a certain depth.