Annular Pressure Calculationsinfohost.nmt.edu/~petro/faculty/Kelly/APC.pdf · Annular Pressure...
3
Annular Pressure Calculations To find the pressure at any point X in the annulus start with f m kx B X P L X D P P − − − − = ρ ) ( (1) The key here is to find L kx which is pressure dependent. Using the gas law x kx x B kB B zT V P zT V P = B B kB x B kx T z V zT P V = a B kB x B kx C zT V zT P L = Sub this into first equation f a B kB x B m B X P C zT V zT P X D P P − ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − − − = ρ In quadratic form ( ) [ ] a B kB x m B X f m B X C zT V zT P P P X D P P ρ ρ − − − − − 2 ac ac b b 4 2 + + a=1 a B kB X m B C zT V zT P c ρ =
Transcript of Annular Pressure Calculationsinfohost.nmt.edu/~petro/faculty/Kelly/APC.pdf · Annular Pressure...
Annular Pressure Calculations
To find the pressure at any point X in the annulus start with fmkxBX PLXDPP −−−−= ρ)( (1) The key here is to find Lkx which is pressure dependent. Using the gas law
x
kxx
B
kBB
zTVP
zTVP
=
BB
kBxBkx Tz
VzTPV =
aB
kBxBkx CzT
VzTPL =
Sub this into first equation
faB
kBxBmBX P
CzTVzTPXDPP −⎟⎟
⎠
⎞⎜⎜⎝
⎛−−−= ρ
In quadratic form ( )[ ]
aB
kBxmBXfmBX CzT
VzTPPPXDPP ρρ −−−−−2
ac
acbb 42 ++
a=1
aB
kBXmB
CzTVzTPc ρ
=
( )2
4))((
2
2
aB
kBXmfmB
fmBX
CzTVzTPXDPPXDP
P
ρρρ +−−−+
−−−=
( )( )
14
)(
2
2
aB
kBXmfmB
fmBX
CzTVzTPXDP
PXDPP
ρρρ +
−−−
+−−−
=
a
kBkB C
VL =
( )( )
1
4)(
2
2
B
kBXmfmB
fmBX
zTLzTPXDP
PXDPP
ρρρ
+−−−
+−−−
=
fmB PXDPAb −−−== ρ)(
B
kBXmBX zT
LzTPAAP ρ++=
42
Other problems controlling wells Volumetric Control If you cannot pump down the drill pipe, or completely out of the hole with drill string. The plan here is allow the gas to migrate up the hole using successive mud bleeding off periods. Procedure Phase one
1) Allow casing pressure to increase by 100 psi 2) Allow additional increase in pressure Δp 3) Bleed through the choke a volume of mud which corresponds to
the additional pressure Δp. mm CV ρ/962= 4) Repeat till gas reaches the surface
Phase two 1) Calculate the mud weight needed to kill the well. Inject a volume
of this mud until the casing pressure is increased by 100 psi. Measure the volume. mV
2) Convert this volume to pressure kmm C Vp ρ/052. Δ=Δ
3) Allow time for the mud to fall down the well. Then bleed the gas through the choke until the casing pressure drops by 100+Δp
4) Repeat till well is full of kill mud.
