l15-subsea flowlines [compatibility mode]

8/7/2019 L15-Subsea Flowlines [Compatibility Mode]

1/15

Lecture15:SubseaSubsea Flow line Design, Transient Flow

& Terrain Slug Prediction

Arun S Chandel

Assistant Professor. . .

09997200339


2/15

This lecture focuses on Flow lines andSlugging

w

Slu in

Riser

slug

Downwardpipe


3/15

Flow lines tie fields back to a productionplatform in shallower waters


4/15

Any vertical undulation in flow line w ill allow one

w w w r r

The erratic regime that results from gas liquidflow slippage between phases is known as slugflow


5/15

Slug accumulation: the liquid can not flowout of the riser due to low velocity

Riser

slug

Downwardpipe

Slug accumulation


6/15

Slug production: liquid eventually flow sinto separator w ith a high velocity w ithlittle or no gas production.

Downwardpipe

Slug production


7/15


8/15

d) Gas blowout large volume of gas surge intoe separa or a g ve oc y w e or no

liquid flow into separator

Downwardpipe


9/15

The possibility of occurrence of slug canbe predicted using Pots number

g ZRTW

)1(

lgl

ss

HgLMW

ss = Pots number

gW lW, = gas and liquid mass flowrate

Z = gas compressibility factorR = universal gas constant

T = pipeline temperature

gM = gas molecular weightg = acceleration due to gravity

l = average qu o up ns e t e p pe ne


10/15

Slug length prediction is done byempirical correlation

5.0=Brill et al

ms

sl = length of slug, ft

D = diameter of pipe, inch

m = m x ure ve oc y, s


11/15

Slug frequency is determined by usingempirical correlations

2.12.1

6.2120226.0

+

= msl

s VU

f

Greskovich and Shrier2.1

25276.79

0226.0

+=V

f ms mg

gsls

ls

UU

U

+

=


slU = super icia iqui ve ocity, t s

mV = mixture velocity, ft/ s

sg = super c a gas ve oc ty, t s


12/15

Slug frequency is determined by using

He wood and RichardsonZabaras

2.125276.790434.0

+=gD

V

Df ms

(sin75.2836.06.212

0226.025.0

2.12.1

+

+

= sl VU

gsls

ls

UU

U

+

=

mVgD


sl = super c a qu ve oc y, s

mV = mixture velocity, ft/ s

sg = super c a gas ve oc y, s


13/15

Several options are available to eliminateterrain-induced slugging

Favourable pipeline bathymetry: Upward flowline is better in reducing slugging

Gas-lift riser: Severe slugging can be mitigated by injecting

gas at the riser base

characteristics from slug flow to churn andannular flow .


14/15

Several options are available to eliminateterrain-induced slugging

Topside chocking: Size and frequency of slugging can be reduced

Subsea se aration: Severe slugging can be eliminated by

separating gas and oil at the bottom of the seaand then allowin oil and as to flow throu h

different


15/15

In summary, flow line should be designedw ith consideration for flow assurance

Slugging is a severe problem forcontinuous production for later life of a

available to predict slugging

Various mechanisms are available toreduce slugging problem

l15-subsea flowlines [compatibility mode]

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