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PETE 661 Drilling Engineering

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Overkill Mud Weights. Spotting a Balanced Heavy-Weight Pill. Reverse Circulation. Bullheading ... Overkill Mud Weights. 50. ATM. Overkill Mud Weights. 51. ATM ... – PowerPoint PPT presentation

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Title: PETE 661 Drilling Engineering


1
PETE 661 Drilling Engineering
  • Lesson 21
  • Well Control Complications

2
Well Control Complications
  • Volumetric Well Control
  • Lubrication
  • Complications During Conventional Kill
  • Techniques to Reduce Annular Friction

3
HW 12 - due Dec 02, 2002
  • Review

4
Gas Kick Migration
  • While a well is shut in the casing pressure
    increase by 1,040 psi in 2 hours.
  • Mud Weight 10 lb/gal
  • How fast is the kick migrating?

5
Gas Kick Migration
p p 1,040
0.052 10 X 1,040 psi
X 2,000 ft (in 2 hrs.)
Migration rate 1,000 ft/hr
X ft ?
  • How fast is the kick migrating?

6
Volumetric Well Control
  • Non-Circulating method of well control.
  • Allows a gas bubble to migrate to the surface
    while systematically allowing the bubble to
    expand. It also maintains the BHP at or above
    formation pressure
  • Used whenever circulation cannot be used to kill
    the well.

7
Two situations can be present
  • Drillpipe can be used to monitor pressure
  • Drillpipe cannot be used

8
Drillpipe can be used
  • When
  • Bit is on bottom
  • Bit is not plugged
  • No float in drillstring

9
Drillpipe can be used
  • Procedure
  • Determine a safety margin for the casing pressure
    (usually 50 - 100 psi above initial stabilized
    SICP and SIDPP)
  • Determine working margin (50 - 100 psi above
    safety margin)
  • As bubble migrates, casing pressure will
    eventually reach the safety margin

10
Drillpipe can be used
  • Procedure
  • Allow the casing pressure to reach the upper
    limit of the working margin
  • Very slowly bleed a small volume of mud from the
    annulus (approximately 1/4 bbl) into a calibrated
    tank. Then close the choke.
  • Let Drillpipe pressure stabilize

11
Drillpipe can be used
  • Procedure, contd
  • If new SIDPP gt Initial SIDPP Safety margin,
    repeat bleeding procedure.
  • If SIDPP Initial SIDPP Safety margin, stop
    bleeding and allow casing pressure to increase
    again.
  • Repeat until circulation can be restored or
    bubble has reached the surface

12
Drillpipe Pressure, psi
Working Margin
Safety Margin
SIDPP
Volume of Mud Bled, bbl
13
Drillpipe cannot be used
  • Plugged bit
  • Migrating fluid is below the bit (bit is off
    bottom)
  • Drillpipe has parted or has a hole that is
    above the influx

14
Drillpipe cannot be used
  • Well closed in on the blind rams
  • Pumps are inoperable and the drillstring is not
    full of mud
  • Gas has entered the drillstring
  • If drillpipe pressure cannot be used, what can we
    do?

15
Volumetric Procedure
  • 1. Record the initial SICP
  • 2. Allow the casing pressure to increase by the
    predetermined safety margin.
  • 3. Allow the casing pressure to further increase
    by the predetermined working margin.

16
Volumetric Procedure
  • 4. Bleed mud from the choke manifold into a
    measuring tank while maintaining a relatively
    stable casing pressure.
  • Continue to bleed mud until the volume in the
    measuring tank is equivalent to the muds HSP of
    the working margin buildup.
  • The HSP is based on the hole dimensions at the
    depth of the rising influx.

17
Volumetric Procedure
  • 6. Repeat steps 3 through 5 until choke
    pressures stabilize, secondary control can be
    regained, or the influx surfaces.
  • 7. Stop the bleed process if gas exits the
    choke. Monitor annulus pressures for further
    buildup.

18
Volumetric Procedure
  • Allowable increase in surface casing pressure
  • 0.052 MW h

h
  • Volume of mud bled from casing
  • A h

BHP constant
19
Example 6.1
pipe on the bank means pipe is out of hole
DATA D10,000ft MW8.7ppg Pit Gain20bbl
Blind Rams Closed ISICP100psi
increasing w/ time 9 5/8in
36lb/ft casing set at 2500ft Open hole diam8
3/4in where fracg0.70psi/ft Tempg70F0.009F/ft
. Write vol proc.
20
Example 6.1
0.0528.7 ppg 0.452 psi/ft
(MAASP)
MAASP Max Allow Annulus Surf. P.
(8.7 lb/gal brine)
21
Example 6.1
(max BHP)
22
Example 6.1
23
Example 6.1
24
Example 6.1
DVMUD is due to being in the casing (17.10 bbl
instead of 16.46 bbl.)
25
Example 6.1
26
Casing Pressure, psig
Working Margin
200
Safety Margin
100
Pit Gain, bbl
27
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28
16.46 bbl of mud
Casing Pressure, psi
Volumetric Drillers Method
Time, min
29
Casing Pressure
Time
30
Lubrication
  • Process of replacing gas at the surface of a
    wellbore with mud.
  • Pump mud into the wellbore
  • Let mud fall
  • Bleed gas
  • Repeat

31
Lubrication
32
Lubrication Procedure
h
  • Desired decrease in surface casing pressure
  • 0.052 MW h

h
  • Volume of mud added to casing
  • A h

BHP constant
33
Example 6.2
  • Consider the final condition in Example 6.1 where
    all the gas has migrated to the surface.
  • Write a lubrication procedure for replacing the
    gas with mud.

34
Example 6.2
35
Example 6.2
36
Example 6.2
37
Example 6.2
38
Example 6.2
39
Example 6.2
40
Example 6.2
41
Example 6.2
42
Example 6.2
43
Off Bottom Well Control
  • Volumetric
  • Use same procedure as before
  • Staging in the Hole
  • Entails circulating mud of sufficient density to
    control BHP at the current position of the bit
    (off bottom)
  • Tripping in the hole some distance
  • Repeat

44
Off Bottom Well Control
Note changes in pressure as the kick migrates
past the bit
(no float in drillstring)
45
Off Bottom Well Control
46
Complication During Conventional Kill
47
Techniques to Reduce Annular Friction
  • Low choke procedure
  • Overkill Mud Weights
  • Spotting a Balanced Heavy-Weight Pill
  • Reverse Circulation
  • Bullheading
  • Dispersing or Segmenting a Gas Kick

48
Low choke procedure
  • Operator intentionally opens the choke to reduce
    the surface casing pressure.
  • I do not recommend this although some operators
    choose to use this procedure

49
Overkill Mud Weights
50
Overkill Mud Weights
51
Example 6.6
  • Estimate the maximum shoe pressure if a 10 ppg
    mud were used to kill the well and prepare a
    drillpipe pressure schedule
  • Calculate the pressure at the shoe if the well
    had to be shut-in at the instant the string was
    filled with the new mud.

52
Example 6.6
53
Example 6.6
54
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55
Example 6.6
The shut-in results in a shoe pressure 181 psi
higher than fracture pressure
56
Spotting a Heavy-Weight Pill
57
Spotting a Heavy-Weight Pill
58
Spotting a Heavy-Weight Pill
59
Spotting a Heavy-Weight Pill
60
Reverse Circulation
61
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62
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63
Bullheading
  • Pump into a shut-in well and attempt to place the
    influx back into the formation.
  • Reasons
  • H2S kicks
  • Inability to circulate on bottom
  • Loss zone below the kick disallows adequate
    circulation rates for a kill
  • To buy time
  • Inability to withstand the maximum surface
    pressures during conventional kill

64
Example 6.8
65
(No Transcript)
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