Petroleum Engineering 406

1
Petroleum Engineering 406

• Lesson 6
• Well Control
• Unusual Operations

2
Read

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

3
Contents

• 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

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
Pipe off bottom or out of hole

• 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 by the wellbore pressure

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

• FPxA
• 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.
• F450x.07854x2.87522919 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?
• WLxPipe wt.-(OD)2x.0408xMWo
• W572 lbf

18
Snubbing calculations

• What is the increase in buoyed weight if the
  tubing is filled with 13.2 ppg mud?
• WiLx(ID)2x.0408xMWi
• 894 lbf

19
Snubbing calculations

• General form of buoyed weight of pipe in the
  wellbore
• WLx 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
Lost circulation during kick

• Partial loss
• Total loss

• Pump LCM keep circulating.
• ?

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
Plugged drillpipe or bit

• 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

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
• SPPCirculating DPP - SIDPP