Pipeline b

Oil/Gas Pipelines

Facilities Engineering, Transportation and Storage

© 2012 UTP Slide No. 1MBB4513

W. K-S. Pao

1. Identify suitable techniques and equipment for petroleum productionand export facilities design and optimisation

2. Apply cost estimating methods for project feasibility study to analyseproject economics

3. Apply risk/reliability assessment in equipment design and selection

Course Outcome


4. Design the pipeline and storage system

Where Are We in the Big Picture?

Separator

Oil Gas Water

piping

pump Compressor pump


Oil/Gas

Terminal

Storage

Sales

Venting

Flaring

Treatment

Injection

Meter

Gas Flow in Pipes


Pipeline Equations

•• WeymouthWeymouth•• PanhandlePanhandle•• ModifiedModified PanhandlePanhandle

UsingUsing thesethese threethree equations,equations, variousvarious combinationcombination ofof pipepipediameterdiameter andand wallwall thicknessthickness forfor aa desireddesired raterate ofof fluidfluid

throughputthroughput cancan bebe calculatedcalculated


throughputthroughput cancan bebe calculatedcalculated

Pipeline Equations

••WeymouthWeymouth equationequation isis preferredpreferred forfor smallersmaller--diameterdiameter lineslines((DD << 1515 inin))..

••PanhandlePanhandle equationequation andand thethe ModifiedModified PanhandlePanhandle equationequation arearebetterbetter forfor largerlarger--sizedsized lineslines..


Weymouth Equation for Horizontal Flow

• Weymouth proposed that f vary as a function ofdiameter in inches as follows:

where q = scfh


where qh = scfh

D = pipe internal diameter, in f = Moody friction factor

••WeymouthWeymouth equationequation isis preferredpreferred forfor smallersmaller--diameterdiameter lineslines ((DD << 1515 inin))•• ForFor partiallypartially developeddeveloped flowflow regimeregime

Weymouth Equation for Horizontal Flow

• Assumptions for use of the Weymouth equation including

• no mechanical work,

• steady flow,

• isothermal flow,

• Constant compressibility factor,


• Constant compressibility factor,

• horizontal flow,

• and no kinetic energy change.

• These assumptions can affect accuracy of calculationresults.

Example 1

For the following data given for a horizontal pipeline, predict gas flow rate in ft3/hr

through the pipeline given Z=0.9188 and viscosity 0.0099cp.

Solution[ ] [ ] 459.67R F= +


[ ] [ ] 459.67

1' 12"

R F= +

=

For the following data given for a horizontal pipeline, predict gas flow rate in ft3/hr through the pipeline by using Weymouth.

Diameter of pipeline = 16 inLength = 220 miles

Average temperature = 80 deg FSpecific gravity of gas = 0.7

Upstream pressure = 650-psia

Downstream pressure = 230-psia

Exercise 1


Downstream pressure = 230-psiaAbsolute roughness of pipe= 0.0006-in

Standard temperature = 60 deg F

Standard pressure = 14.7 psiaAverage z factor = 0.8533

Viscosity of gas = 0.0099

Ans: ~2.4 MMscf/hr

Panhandle A Equation-Horizontal Flow

pipeline flow equation is thus


where q is the gas flow rate in ft3/d measured at Tb and pb,and other terms are the same as in the Weymouth equation.

Panhandle B Equation-Horizontal Flow

(Modified Panhandle)

Long transmission and Delivery lines


q = gas flow rate (ft3/d)

Units are same as in Panhandle A Eqn

Panhandle B Equation-Horizontal Flow

(Modified Panhandle)

A section of a pipeline system is to handle 200 MMSCFD gas flow. The pipeline inlet pressure is 900 psig and the gas flows to a dehydrator operating at 800 psig.

The allowable working pressure of the pipeline is 1480 psi. The following data are given: STC 14.73 psi, 60oF, average temperature 80oF, compressibility 0.67,

specific gravity of gas 0.85, viscosity 0.01 cp, length 5 miles. Determine D.

Soln:


( )0.510

2 21.02

6 2.530

0.961

914 814520200 10 737

14.73 (540)(0.67)(5)(0.85)D

− × =

Example

A natural gas pipeline, NPS 16, 0.25”, 50 mi long, with a branch pipe (NPS 8,

0.25”, 15 mi long), as shown in Figure below, is used to transport 100 MMSCFD gas (gravity = 0.6, viscosity 0.000008 lb/ft-s) from A to B (20 mi long). At B, a delivery of 30 MMSCFD occurs into the branch pipe BE. The delivery pressure at

E must be maintained at 300 psig. The remaining volume 70 MMSCFD is shipped to terminal C at the delivery pressure of 600 psig. Assume a constant gas temperature of 60F, pipeline efficiency of 0.95, base temperature and pressure at

60F and 14.7 respectively. The compressibility factor Z=0.88.


Cont.

a) Using Panhandle A, calculate the inlet pressure at Ab) Is a pressure regulator required at E?


Cont.


Empirical Pipeline Equation

A general non-iterative pipeline flow equation is written as

[ft3/day]

The values of the constants are given in Table for the different

pipeline flow equations.


pipeline flow equations.

Plant Piping – Low Pressure Flow

Short run of gas piping < 100 psi

=∆

5

2000336.0

100

d

fWP

m

ρ

W, Rate of flow, (1000 Ib/hr)


1 2

100 1

m

2

2 9

5

(10 ) ; where C

336,000f and C

d

or

C C WP

ρ ρ

−

∆ = =

=

The solution is a pressure gradient in psi/100 ft

Operationally...

Rate of flow, W

(1000 Ib/hr)


Example

Calculate the pressure drop in a 10-in.,Schedule 40 pipe for a flow of 150,000 Ib/hr of

methane. Temperature is 60°F and pressure is 750 psia. The compressibility factor is

0.905


3(16.042)(750)2.38lb/ft

(10.73)(460 60)(0.905)

Mp

RTzρ = = =

+

Example

C1 = 22.5

C2 = 0.0447

∆P = 22.5(0.0447)/2.38

=0.423 psi/100 ft


Example

Calculate the required line size (of Schedule 40 pipe)to give ∆P100 = 1 psi or less when

flowing 75,000 lb/hr of methane at 400 psia and 100°F. The compressibility factor is

0.96

C1 = 5.6

3(16.042)(400)1.11lb/ft

(10.73)(460 100)(0.96)

Mp

RTzρ = = =

+


C1 = 5.6

C2 = (∆P100)ρ/C1

= 1(1.11)/5.6 = 0.2

Example

The smallest size of Schedule 40 pipe with C2 less than

0.20 is 8-in pipe.

For 8-in. Sch 40 pipe, C2 is 0.146. The actual pressure drop

can then be calculated as

∆P = 5.6(0.146)/1.11 = 0.74 psi/100ft


Pipeline b

Environment

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