3. Shallow Gas
• Many shallow gas sands are abnormally
pressured
• Total pressure (psi) may be low high EMW
– e.g. FP = 452 psi (8.7 ppg eq.) at 1000’
– Drill with 9.0 ppg mud - 0.3 ppg overbalanced
only 16 psi = 35’ of fluid
4. Shallow Gas
• If we shut-in on kick
• we lose circulation
and possibly broach to
surface
5. Shallow Gas Kicks
• Pick up Kelly until lower kelly cock clears
rotary
• Shut down pumps
• Check for flow
• If flowing, open the down wind diverter
valve
• Close annular
6. Shallow Gas Kicks
• Start circulating heavy mud with both
pumps
• If all heavy mud used up, pump all mud in
mud pits
• When this mud is gone, pump sea water
• Continue until well is under control
– may deplete
– or bridge
7. Subsea Well Control
• Floating rigs
• BOP stack on sea floor
• Communication from the wellbore to
surface through riser
9. Subsea Well control
• Riser is not designed to contain pressure
• If the riser is evacuated, it will collapse
• There is a telescoping joint at the top
• Choke and kill lines to circulate kicks
through
• PVT and flow indicators affected by heave
of vessel
10. Effect of choke and kill line
• Possibly high CLFP during kicks
• u-tube effect as gas hits choke line
• Gas in top of BOP stack
• Kill riser after killing well
