Gas Pressure Dorp in Pipelines....
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Transcript of Gas Pressure Dorp in Pipelines....
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8/12/2019 Gas Pressure Dorp in Pipelines....
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PRESSURE DROP IN GAS PIPELINES
Jn Steinar Gumundsson
TPG4140 Natural Gas
September 16, 2010
Importance of pressure drop and different pipes
Pressure drop in pipelines (depends on d5) Equations for liquid and gas flow
North Sea gas pipelines
Friction factor and roughness R&D on friction (roughness) and pressure drop
Summary
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A: Wells, B: Flowlines, C: Risers, D: Process pipes, E: Off-Loading, F: Pipelines
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Importance of pressure drop Transport capacity, we want to be able to push as much gas as
possible through existing pipelines to customers. Norwegian export
pipelines 100 BCM annually. Expensive gas compression (power and emissions) needed to give
sufficient inlet pressure to overcome pressure drop. Gas turbines
drive centrifugal compressors offshore (and on land?). Largest
consumption of power offshore.
Export pipelines have epoxy coating to make wall smoother to
reduce wall friction and hence greater production rate.
Production capacity (subsea-to-beach), we want to maintain
wellhead pressure as low as possible to sustain large production
rate from gas fields with time. Eventually we need subseacompression.
Large diameter pipelines used to avoid compression platforms along
export gas pipelines. On land, compressor stations along pipeline.
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Pressure and Temperature With Distance
Booster compressor duty: 15.5 MW (most likely roughness)
sgard Transport (69.4 vs. 76.9 MSm/d)
110
120
130
140
150160
170
180
190
200
210
0 200 400 600 800Distance KP (km)
Pressur
e(barg)
0
5
10
15
2025
30
35
40
45
50
Tempera
ture(C)
Pressure Booster_press Temperature Booster_temp
Aamodt (2006)
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Natural Gas Pipeline
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Pressure Drop in Pipelines
where g (gravitation), a and f stand for hydrostatic, acceleration and
friction, respectively. The three terms can be expressed as
fag pppp
Lud
fp
uup
Lgp
f
a
g
21
2
sin
The total pressure drop in pipelines and wells consists of three terms
The angel is measured from horizontal and the lenght is the pipe lenght,
not height over/under the surface. The pressure drop due to friction is
the Darcy-Weisbach equation.
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Darcy-Weisbach Equation
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Darcy-Weisbach EquationLiquid Flow and When Gas Average Density Used
Lrrp 22
L
pr
2
2
8
1
uf
2
81
2uf
L
pr
2
2ud
Lfp
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Darcy-Weisbach Equation
Force balance, steady-state pipe flow
wrdLrdp 22
dL
dprw2
2
8
1ufw
2
8
1
2uf
dL
dpr
2
2 ud
Lf
pf
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North Sea Pipelines
Sletfjerding, E. (1999): Friction Factor in Smooth and Rough Gas Pipelines, Dr.Ing.,
Petroleum, NTNU.
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North Sea Pipelines
Sletfjerding, E. (1999): Friction Factor in Smooth and Rough Gas Pipelines, Dr.Ing.,
Petroleum, NTNU.
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North Sea Pipelines
Sletfjerding, E. (1999): Friction Factor in Smooth and Rough Gas Pipelines, Dr.Ing.,
Petroleum, NTNU.
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North Sea Pipelines: Pressure Gradient
Sletfjerding, E. (1999): Friction Factor in Smooth and Rough Gas Pipelines, Dr.Ing.,
Petroleum, NTNU.
6,06
348,406,30812,895,5146,7H
167,6010,66227,0112,1136,3G
334,109,4448,567,4572,03F
334,106,95619,086,8129,85E
185,403,2648,563,6465,22D
185,402,23619,094,16107,97C
383,506,81303,5145,59166,26B
205,502,81812,485,59108,42A
kg/sbar/100 kmkmbarbar
m(p1-p2)/LLp2p1
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Pressure Gradient in Gas Pipelines
6 (average 8 pipelines)
15-25
North Sea, Sletfjerding
(1999)
Canada, Hughes (1993)*
Gradient (bar/100 km)
* Mokhatab o.a. (2006, s. 419)
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Maximum Gas Velocity*
*NORSOK P-001 (1999)
Sletfjerdings (1999) North Sea Pipelines A-H, uaverage (m/s), only 10-20 % av NORSOK umaximum
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Pressure Drop Horizontal Gas Pipeline
0ln2
1
2
22
1
2
22
2
L
p
p
f
dpp
zRTfm
MdA
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Frictional Pressure Drop Gas Pipeline
Horizontal Pipeline, Inclined Well
2
2ud
Lfpf 0Lp
plnfdpp
RTzmfMAd
2
1
2
221
222
2
Laggab
Lagpp
sin2exp1sinsin2exp 22
1
2
2
zRT
Ma
dA
fmb
2
2
2
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Friction Factor in Pipelines
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Nikuradses Sand-Grain Data
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Moody Chart
Add reference to fluid mechanics text book.
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Blasius Equation
000.100Re
Re316,025,0
rrglatteHydraulisk
f
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Haalands Equation
vskeforn
gassforn
dk
nf
nn
1
3
75,3Re9,6log8,11
11,1
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Wall Roughness in Pipes
5.1
12.5
30.033.0
35.1
38.1
53.3
0.20010-3
0.49210-3
1.1810-3
1.3010-3
1.3810-3
1.5010-3
2.1010-3
Internally plastic coated pipeline
Honed bare carbon steel
Electropolished bare 13CrCement lining
Bare carbon steel
Fiberglass lining
Bare 13Cr
Average
Absolut
Roughness(m)
Average
Absolut
Roughness(inch)
Material
Farshad og Rieke, JPT, oktober 2005, side 82-86.
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Blasius, Colebrook-White and Haaland
d
k
ff 7,3Re
51,2log2
1
nn
d
k
nf
11,1
75,3Re
9,6log8,11
Haaland n=1 for liquids, same as Coolebrook-White
Haaland n=3 for gases, same as AGA data
25,0Re
316,0
f
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Haaland Friction Factor
Gases, n=3, Hydraulically smooth and k/d=0.001
0,00000
0,00500
0,01000
0,01500
0,02000
0,02500
0,03000
0,03500
0 200000 400000 600000 800000 1000000 1200000
Reynolds-tall
Fri
ctionfaktor
Haaland for gas based on AGA data, lower than for liquids, transition different
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Haaland Friction Factor
Liquid n=1 and gas n=3, k/d=0.001
0,00000
0,00500
0,01000
0,01500
0,02000
0,02500
0,03000
0,03500
0 200000 400000 600000 800000 1000000 1200000
Reynolds-tall
Friksjonsfaktor
Gas 3.8 % lower than liquid at Re=106
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Nikuradses Sand Grain and Real Roughness
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Sletfjerding
Ra = Arithmetic mean roughness
Rq = Root-mean-square roughness
Rz = Mean peak-to-valley roughness
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Pipes Used by Sletfjerding
Sand-grain roughness ks, Measured roughness Rq , Hurste exponent H
4.5 < (ks/Rq) < 5.8
21 < ks
< 181
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Summary Equation for pressure drop in horizontal gas pipelines; the
natural logarithm term can often be neglected (gentle
decrease in pressure)
Blasiuss equation used for smooth pipes and when Re