9. Well Control.ppt
Transcript of 9. Well Control.ppt
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PETE 661
Drilling Engineering
Lesson 9Well Control Concepts
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Lesson 9 - Well Control Concepts
The Anatomy of a KICK
Kicks - Definition
Kick Detection
Kick Control
(a) Dynamic Kick Control
(b) Other Kick Control Methods
* Driller’s Method
* Engineer’s Method
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Read:
Applied Drilling Engineering, Ch.6
HW # 6
Kick Control
due Monday, Oct. 13, 2003
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Causes of Kicks
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Causes of Kicks
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Causes of Kicks
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What?
What is a kick?
An unscheduled
entry of
formation
fluid(s) into the
wellbore
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Why?
Why does a kick occur?
The pressure inside thewellbore is lower
than the formation
pore pressure (in apermeable formation).
pw < pf
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How?
How can this occur?
Mud density is too low
Fluid level is too low - trips or lost circ.
Swabbing on trips
Circulation stopped - ECD too low
)pp( FW
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What ?
What happens if a kick is not
controlled?
BLOWOUT !!!
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Typical Kick Sequence
1. Kick indication
2. Kick detection - (confirmation)
3. Kick containment - (stop kick influx)
4. Removal of kick from wellbore
5. Replace old mud with kill mud (heavier)
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Kick Detection and Control
Kick Detection Kick Control
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1. Circulate Kick out of hole
Keep the BHP constant throughout
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2. Circulate Old Mud out of hole
Keep the BHP constant throughout
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Kick Detection
Some of the preliminary events that maybe associated with a well-control
problem, not necessarily in the order of
occurrence, are:
1. Pit gain;
2. Increase in flow of mud from the well
3. Drilling break (sudden increase in
drilling rate)
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Kick Detection
5. Shows of gas, oil, or salt water
6. Well flows after mud pumphas been shut down
7. Increase in hook load8. Incorrect fill-up on trips
4. Decrease in circulating pressure;
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Dynamic Kick Control[Kill well “on the fly”]
For use in controlling shallow gas kicks
• No competent casing seat
• No surface casing - only conductor
• Use diverter (not BOP’s)
• Do not shut well in!
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Dynamic Kick Control
1. Keep pumping. Increase rate!
(higher ECD)
2. Increase mud density0.3 #/gal per circulation
3. Check for flow after each
complete circulation
4. If still flowing, repeat 2-4.
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Conventional Kick Control{Surface Casing and BOP Stack are in place}
Shut in well for pressure readings.
(a) Remove kick fluid from wellbore;
(b) Replace old mud with kill weight mud
Use choke to keep BHP constant.
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Conventional Kick Control
1. DRILLER’S METHOD
** TWO complete circulations **
Circulate kick out of hole
using old mud
Circulate old mud out of hole
using kill weight mud
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Conventional Kick Control
2. WAIT AND WEIGHT METHOD
(Engineer’s Method)
** ONE complete circulation **
Circulate kick out of hole
using kill weight mud
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Driller’s Method - Constant Geometry
Information required:
Well Data:
Depth = 10,000 ft.
Hole size = 12.415 in. (constant)
Drill Pipe = 4 1/2” O.D., 16.60 #/ft
Surface Csg.: 4,000 ft. of 13 3/8” O.D. 68 #/ft
(12.415 in I.D.)
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Driller’s Method - Constant Geometry
Kick Data:
Original mud weight = 10.0 #/gal
Shut-in annulus press. = 600 psi
Shut-in drill pipe press. = 500 psi
Kick size = 30 bbl (pit gain)
Additional Information required:
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Constant
Annular
Geometry.
Initial
conditions:
Kick has just
entered the
wellbore
Pressures
have
stabilized
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Successful Well Control
1. At no time during the process of
removing the kick fluid from the
wellbore will the pressure exceed the
pressure capability of
the formation
the casing
the wellhead equipment
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Successful Well Control
2. When the process is complete the wellboreis completely filled with a fluid of
sufficient density (kill mud) to control the
formation pressure.
Under these conditions the well will not flow
when the BOP’s are opened.
3. Keep the BHP constant throughout.
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Calculations
From the initial shut-in data we can
calculate:
• Bottom hole pressure
• Casing seat pressure
• Height of kick• Density of kick fluid
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PB = SIDPP + Hydrostatic Pressure in DP
= 500
+ 0.052 * 10.0 * 10,000
= 500 + 5,200
PB = 5,700 psig
Calculate New Bottom Hole Pressure
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Calculate Pressure at Casing Seat
P4,000 = P0 + DPHYDR. ANN. 0-4,000
= SICP + 0.052 * 10 * 4,000
= 600 + 2,080
P4,000
= 2,680 psig
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This corresponds to a pressure gradient of
Equivalent Mud Weight (EMW) =
psi/ft670.0ft
psi
000,4
680,2
lb/gal88.12)gal/lb)(ft/psi(
ft/psi 052.0
670.0
Calculate EMW at Casing Seat
( rmud = 10.0 lb/gal )
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Annular capacity per ft of hole:
bbls/ft0.13006
gal42
bbl
in231
gal*in12*)5.4415.12(
4
L)DD(4v
3
322
2
P
2
Hx
Calculate Initial Height of Kick
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ft231
ft7.230bbl/ft0.13006
bbl30
v
Vh
x
BB
hole,of bottomatkick of Height
Calculate Height of Kick
hB
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Calculate Density of Kick Fluid
The bottom hole pressure is the pressure at
the surface plus the total hydrostatic pressure
between the surface and the bottom:
Annulus Drill String
P SICP P P SIDPP PB MA KB MD D D D
600 0052 10
. *
*(10,000-231) P 500 (0.052*10*10,000)KBD
600 5,080 P 500 5,200KB D
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Density of Kick Fluid
(must be primarily gas!)
lb/gal67.1231*052.0
20KB r
DP psiKB 20
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NOTE:
The bottom hole
pressure is kept
constant while the kickfluid is circulated out of
the hole!
In this case
BHP = 5,700 psig
Circulate Kick Out of Hole
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Constant
Annular Geometry
Driller’s Method.
Conditions When
Top of Kick Fluid
Reaches the Surface
BHP = const.
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Top of Kick at Surface
As the kick fluid moves up the annulus, it
expands. If the expansion follows the gas
law, then
[bottom] ]surface[
RTnZ
VP
RTnZ
VP
BBB
BB
000
00
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Top of Kick at Surface
Ignoring changes due to compressibility
factor (Z) and temperature, we get:
Since cross-sectional area = constant
.)constv(v
hPhP.e.i
hvPhvP VPVP
B0
BB00
BBB000
BB00
f S f
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Top of Kick at Surface
We are now dealing two unknowns, P0
and
h0. We have one equation, and need a
second one.
BHP = Surface Pressure + Hydrostatic Head
5,700 = Po + DPKO + DPMA
5,700 = Po
+ 20 + 0.052 * 10 * (10,000 - hO
)
5,700 - 20 - 5,200 = Po - 0.52 *o
BB
P
hP
T f Ki k S f
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Top of Kick at Surface
psi102,1862240P
2
684,684*4480480P
0684684P480P
231*5700*52.0PP480
0
2
0
0
2
0
2
00
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40 1,200502,000/40 2,000
8001,100
40
1,200 + 800 2,000
800 / (0.052 * 14,000) 1.10
13.514.6
1,200 * 14.6 / 13.5
1,298 psi
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2,000
bbls200
1,298
0
0
0
5 10 15 20 30 4025 35 45
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Csg DS DS Csg
Pressure When Circulating
Static Pressure
First Circulation Second Circulation
Driller’s
Method
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Csg DS DS Csg
Volume Pumped, Strokes
Drillpipe Pressure
Driller’s
Method
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65
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2
Engineer’s
Method