406 lesson 7

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406 lesson 7

  1. 1. Petroleum Engineering 406 Lesson 7 Well Control Shallow gas and Subsea Well Control
  2. 2. Read• Well Control Manual – Chapter 10,15
  3. 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. 4. Shallow Gas• If we shut-in on kick• we lose circulation and possibly broach to surface
  5. 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. 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. 7. Subsea Well Control• Floating rigs• BOP stack on sea floor• Communication from the wellbore to surface through riser
  8. 8. Subsea Well controlKill Line Choke Line Booster Line BOP
  9. 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. 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

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