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Petroleum Engineering 406

Petroleum Engineering 406. Lesson 6 Well Control Unusual Operations. Read. Well Control Manual Chapter 13 Homework 4 Due Feb. 17, 1999. Pipe off bottom or out of hole Stripping Snubbing Excessive casing pressure Lost circulation Hole in casing string. Plugged drillpipe or bit

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Petroleum Engineering 406

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  1. Petroleum Engineering 406 Lesson 6 Well Control Unusual Operations

  2. Read • Well Control Manual • Chapter 13 • Homework 4 • Due Feb. 17, 1999

  3. Pipe off bottom or out of hole Stripping Snubbing Excessive casing pressure Lost circulation Hole in casing string Plugged drillpipe or bit Hole in drillpipe H2S kicks Trapped pressure Gas kicks in OB mud Gas cut mud Determine SPP after kick Contents

  4. Pipe off bottom or out of hole • Kick is below bit • Cannot circulate kick out with bit at this point. • Must get to bottom • Stripping • Snubbing

  5. Stripping - tripping into or out of the well under pressure through closed preventers Buoyed weight of the drillstring > force exerted by the wellbore pressure Snubbing - tripping into or out of the well under pressure through closed preventers Buoyed weight of the drillstring < force exerted by the wellbore pressure Pipe off bottom or out of hole

  6. Forces acting on drillstring • Down • weight of drillstring • downward forces from pressure on upsets • Up • buoyancy effects • upward forces from pressure on upsets

  7. Forces acting on drillstring • Net effect • down • buoyed weight of drillstring • up • force from pressure acting on cross sectional area of pipe inside the BOP • =Pressure x area

  8. Stripping through annular • Install safety valve in top of drillstring (inside BOP)

  9. Stripping through annular

  10. Stripping through annular

  11. Stripping through rams

  12. Stripping through rams

  13. Stripping through rams

  14. Stripping through rams

  15. Snubbing Snubbing

  16. Snubbing calculations • F=PxA • Example: A well has 450 psi pressure. • 2-7/8”, 6.5 lb/ftpipe in well with BOP closed. What is the upward force on the pipe. • F=450x.07854x2.875^2=2919 lbf • =449 ft of pipe if suspended in air

  17. Snubbing calculations • What is the buoyed weight of 279’ of 2.875”, 6.5 lb/ft pipe (pipe empty) suspended in 13.2 ppg mud? • W=Lx[Pipe wt.-{(OD)2x.0408xMWo}] • W=572 lbf

  18. Snubbing calculations • What is the increase in buoyed weight if the tubing is filled with 13.2 ppg mud? • Wi=Lx(ID)2x.0408xMWi • 894 lbf

  19. Snubbing calculations • General form of buoyed weight of pipe in the wellbore • W=Lx [Pipe wt.-{(OD)2x.0408xMWo}+ {(ID)2x.0408xMWi}]

  20. Excessive casing pressure • Casing pressure exceeds: • MASP • Rated pressure of BOP • Rated pressure of casing

  21. Partial loss Total loss Pump LCM keep circulating. ? Lost circulation during kick

  22. Lost circulation during kick • Circulating out kick • Casing seat fractures • Underground blowout • Determine where thief zone is • Pump heavy mud on bottom, light on top • Spot barite plug

  23. Lost circulation during kick • Drilling into thief zone • Upper zone kicks • Gunk squeeze on bottom • Kill upper zone

  24. Hole in casing string • Treat similar to lost circulation • Can set casing patch • Cement

  25. If you can continue to circulate adjust kill sheet to reflect the increase in pressure loss If you cannot continue to circulate May have to “blow” the jets out, or perforate Plugged drillpipe or bit

  26. Hole in drillpipe • Must plug the hole • strokes to bet incorrect • SPP incorrect • wash DP in two • Pump softline or panty hose • Set plugs, strip out, replace leaky joint, strip back in

  27. H2S kicks • Hydrogen Sulfide • very poisonous, • explosive • accumulates in low areas • Some people bullhead

  28. Trapped pressure • Record SIDPP and SICP • Bleed small amounts of mud from annulus • Close choke, record SIDPP and SICP • If both pressures are lower than before, repeat bleeding. • If SIDPP is the same and SICP is slightly higher, stop bleeding.

  29. Gas kicks in OB mud • Solubility of gas in OB mud can mask the kick indicators. • Look for small pit gains, and small flow increases • Gas remains in solution until near the surface, where it comes out of solution (sometimes violently) and expands rapidly

  30. Gas Cut Mud • What is it? • Where does it come from? • How dangerous is it? • Are we loosing much HSP?

  31. Gas Cut Mud • Determine where gas came from by: • circulating BU • If gas goes away with circulation • probably drilled gas • If gas does not go away with circulatio • raise MW • Causes very little loss of HSP • almost all expansion near the surface

  32. Gas Cut Mud

  33. Gas Cut Mud

  34. Gas Cut Mud

  35. Gas Cut Mud

  36. Gas Cut Mud

  37. Gas Cut Mud

  38. Gas Cut Mud

  39. Determine SPP after kick • Slowly increase pump speed to kill speed while • maintaining casing pressure = SICP • When pumps are up and stable at kill speed • record circulating DPP • SPP=Circulating DPP - SIDPP

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