Hydrocarbon Chemistry

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By:

Ahmed Barifcani Stefan Iglauer Muhammad Arif

1

Hydrocarbon Phase Behaviour

Tutorial - Week 7

Gas Hydrate Calculations

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Hydrates – An introduction

 Hydrates can form in the oil and gas production/transmission system when specific conditions are met.

 They can cause pipe blockage; causing reduction in production rates.

 Important element to be considered for flow assurance.

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Hydrates as Energy Resource

Can be future source of energy after depletion of conventional reservoir and tight sands.

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Contents

 Activity 01 • Guided example - to determine the rate of inhibitor for prevention of hydrate

formation.

 Activity 02 • In Class Activity - Solve the problem yourself – Find the rate of methanol for

prevention of hydrate formation

 Activity 03 • Descriptive questions

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Learning Outcomes

 To predict whether hydrates will form under given set operating conditions

 To be able to design hydrate mitigation treatment related to oil and gas well tubing, pipelines or transmission lines

5

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Separator

Wellhead

Tubing

Hydrocarbon bearing formation

Flowlines

Transmission Lines

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Where can hydrate form?

Separator

Wellhead

Tubing

Hydrocarbon bearing formation

Flowlines Transmission

Lines

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Activity 01: Determine injection rate of methanol to prevent hydrate formation.

 Input (given) data:

 Given gas composition is as follows:

Parameter Value

Reservoir pressure 90 bar

Reservoir temperature 71 oC

Molecular weight of air 28.96 g/mol

Pipeline pressure 90 bar

Pipeline temperature 4 oC

Component Volume fraction MW (g/mol)

Methane 0.82 16.04 Ethane 0.055 30.07 Propane 0.04 44.1 Carbon dioxide 0.002 44.01 Nitrogen 0.083 28.01

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Gas Hydrate Formation Control

 Step 01: Calculate Specific gravity of gas using the given composition:

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Component Volume fraction MW (g/mol) Volume Fraction*MW

Methane 0.82 16.04 13.1528 Ethane 0.055 30.07 1.65385 Propane 0.04 44.1 1.764 Carbon dioxide 0.002 44.01 0.08802 Nitrogen 0.083 28.01 2.32483

Sum = 18.98

𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺𝐺𝐺 = d = 𝑀𝑀𝑀𝑀 𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 𝑀𝑀𝑀𝑀 𝑎𝑎𝑚𝑚𝑚𝑚

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 Step 02:

Calculation of Hydrate formation temperature:

10

𝐺𝐺𝑓𝑓 deg 𝐶𝐶 = −6.44 − 3.79 𝑑𝑑2

+ 7.68𝑙𝑙𝑙𝑙 𝑃𝑃 𝑏𝑏𝐺𝐺𝐺𝐺𝑏𝑏

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 Step 02:

Calculation of Hydrate formation temperature:

11

𝐺𝐺𝑓𝑓 = −6.44 − 3.79

0.6552 + 7.68𝑙𝑙𝑙𝑙 90

𝐺𝐺𝑓𝑓 = 19.284 ℃

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 Make a Judgement whether hydrate will form or not?

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 Yes, Hydrates will form.

 The reason is that the pipeline temperature (4 oC) is well below the hydrate formation temperature (calculate in previous step as 19.28 oC).

 If the pipeline temperature is well above the hydrate formation temperature, then hydrates do not form.

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 Step 03:

a) Determine water content of saturated gas leaving the separator:

Pressure = 90 bar = 1305 psia

Temperature = 71 ℃ = 160 ℉

Use McKetta and Wehe Graphical Correlation

℉ = (℃ ∗ 9/5) +32

1 𝑏𝑏𝐺𝐺𝐺𝐺 =14.5 psi

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220 lb/MMSCF

160 oF

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0.995

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 Step 03 :

From McKetta and Wehe Graphical Correlation

𝑏𝑏𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆𝑑𝑑 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺 𝑆𝑆𝑐𝑐𝑙𝑙𝐺𝐺𝑆𝑆𝑙𝑙𝐺𝐺 𝑆𝑆𝑐𝑐𝐺𝐺𝐺𝐺𝑆𝑆𝑆𝑆𝐺𝐺𝑆𝑆𝑑𝑑 = 220 × 0.995

𝑏𝑏𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆𝑑𝑑 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺 𝑆𝑆𝑐𝑐𝑙𝑙𝐺𝐺𝑆𝑆𝑙𝑙𝐺𝐺 𝑆𝑆𝑐𝑐𝐺𝐺𝐺𝐺𝑆𝑆𝑆𝑆𝐺𝐺𝑆𝑆𝑑𝑑 = 219 𝑙𝑙𝑏𝑏/𝑀𝑀𝑀𝑀𝑆𝑆𝐶𝐶𝑀𝑀

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 Step 03 :

b)Determine water content of saturated gas at the pipeline conditions:

Use values obtained from McKetta and Wehe Graphical Correlation

Pipeline pressure 90 bar

Pipeline temperature 4 oC

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7 lb/MMSCF

~40 oF

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1 40oF

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 Step 03 :

From McKetta and Wehe Graphical Correlation, at pipeline conditions:

𝑏𝑏𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆𝑑𝑑 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺 𝑆𝑆𝑐𝑐𝑙𝑙𝐺𝐺𝑆𝑆𝑙𝑙𝐺𝐺 𝑆𝑆𝑐𝑐𝐺𝐺𝐺𝐺𝑆𝑆𝑆𝑆𝐺𝐺𝑆𝑆𝑑𝑑 = 7 × 1

𝑏𝑏𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆𝑑𝑑 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺 𝑆𝑆𝑐𝑐𝑙𝑙𝐺𝐺𝑆𝑆𝑙𝑙𝐺𝐺 𝑆𝑆𝑐𝑐𝐺𝐺𝐺𝐺𝑆𝑆𝑆𝑆𝐺𝐺𝑆𝑆𝑑𝑑 = 7 𝑙𝑙𝑏𝑏/𝑀𝑀𝑀𝑀𝑆𝑆𝐶𝐶𝑀𝑀

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 Step 04 :

Determine the reduction in saturated water content:

𝑏𝑏𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆𝑑𝑑 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺 𝑆𝑆𝑐𝑐𝑙𝑙𝐺𝐺𝑆𝑆𝑙𝑙𝐺𝐺 = 𝑏𝑏𝐺𝐺𝐺𝐺. 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺 𝑏𝑏𝑆𝑆𝑆𝑆𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝑐𝑐𝐺𝐺 − 𝑏𝑏𝐺𝐺𝐺𝐺. 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺(𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑙𝑙𝑆𝑆𝑙𝑙𝑆𝑆)

𝑏𝑏𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆𝑑𝑑 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺 𝑆𝑆𝑐𝑐𝑙𝑙𝐺𝐺𝑆𝑆𝑙𝑙𝐺𝐺 = 219 − 7 = 212 𝑙𝑙𝑏𝑏/𝑀𝑀𝑀𝑀𝑆𝑆𝐶𝐶𝑀𝑀

1 𝑙𝑙𝑏𝑏 𝑀𝑀𝑀𝑀𝑆𝑆𝐶𝐶𝑀𝑀⁄ = 0.01602 𝑔𝑔/𝑆𝑆𝑚𝑚3

𝑏𝑏𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆𝑑𝑑 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺 𝑆𝑆𝑐𝑐𝑙𝑙𝐺𝐺𝑆𝑆𝑙𝑙𝐺𝐺 = 3.4 𝑔𝑔/𝑆𝑆𝑚𝑚3

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 Step 05:

Determine Mole fraction of water using Neilson and Bucklin equation:

𝑥𝑥𝑤𝑤 = 𝑆𝑆𝑥𝑥𝑆𝑆 ∆𝐺𝐺 −72

∆𝐺𝐺 = ℎ𝐺𝐺𝑑𝑑𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆 𝑆𝑆𝑐𝑐𝐺𝐺𝑚𝑚𝐺𝐺𝐺𝐺𝑆𝑆𝑐𝑐𝑙𝑙 𝐺𝐺𝑆𝑆𝑚𝑚𝑆𝑆𝑆𝑆𝐺𝐺𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝑆𝑆 − 𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑙𝑙𝑆𝑆𝑙𝑙𝑆𝑆 𝐺𝐺𝑆𝑆𝑚𝑚𝑆𝑆𝑆𝑆𝐺𝐺𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝑆𝑆

∆𝐺𝐺 deg 𝐶𝐶 = −72 𝑙𝑙𝑙𝑙 𝑥𝑥𝑤𝑤

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 Step 05:

Determine Mole fraction of water using Neilson and Bucklin equation:

𝑥𝑥𝑤𝑤 = 𝑆𝑆𝑥𝑥𝑆𝑆 ∆𝐺𝐺 −72

= 𝑆𝑆𝑥𝑥𝑆𝑆 15.284 −72

= 0.776

∆𝐺𝐺 = ℎ𝐺𝐺𝑑𝑑𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆 𝑆𝑆𝑐𝑐𝐺𝐺𝑚𝑚𝐺𝐺𝐺𝐺𝑆𝑆𝑐𝑐𝑙𝑙 𝐺𝐺𝑆𝑆𝑚𝑚𝑆𝑆𝑆𝑆𝐺𝐺𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝑆𝑆 − 𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑙𝑙𝑆𝑆𝑙𝑙𝑆𝑆 𝐺𝐺𝑆𝑆𝑚𝑚𝑆𝑆𝑆𝑆𝐺𝐺𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝑆𝑆

∆𝐺𝐺 = 19.284 − 4 = 15.284

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 Step 06:

Determine Mole fraction of methanol:

𝑥𝑥𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚 = 1 − 𝑥𝑥𝑤𝑤

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 Step 06:

Determine Mole fraction of methanol:

𝑥𝑥𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚 = 1 − 0.776 = 0.224

These are mole fractions – we require weight fraction to be able to specify injection rate in useful units

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 Step 07:

Determine weight fraction of methanol:

𝑤𝑤𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚 = 𝑥𝑥𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚𝑀𝑀𝑀𝑀𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚

𝑥𝑥𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚𝑀𝑀𝑀𝑀𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚 + 𝑥𝑥𝑤𝑤𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚𝑀𝑀𝑀𝑀𝑤𝑤𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚

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 Step 07:

Determine weight fraction of methanol:

𝑤𝑤𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚 = 𝑥𝑥𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚𝑀𝑀𝑀𝑀𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚

𝑥𝑥𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚𝑀𝑀𝑀𝑀𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚 + 𝑥𝑥𝑤𝑤𝑀𝑀𝑀𝑀𝑤𝑤𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚

𝑤𝑤𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚 = 0.224 × 32

0.224 × 32) + (0.776 × 18

𝑤𝑤𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚 = 34 𝑤𝑤𝑆𝑆𝑆𝑆𝑔𝑔ℎ𝐺𝐺 %

𝑤𝑤𝑤𝑤𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚 = 100 − 34 = 66 𝑤𝑤𝑆𝑆𝑆𝑆𝑔𝑔ℎ𝐺𝐺 %

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 Step 08:

Determine required methanol in aqueous phase:

𝐺𝐺𝑆𝑆𝑟𝑟d. methanol in aq. phase = 0.34 0.66

∗ 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺 𝑆𝑆𝑐𝑐𝑙𝑙𝐺𝐺𝑆𝑆𝑙𝑙𝐺𝐺

𝐺𝐺𝑆𝑆𝑟𝑟d. methanol in aq. phase = 0.515 ∗ 3.4

𝐺𝐺𝑆𝑆𝑟𝑟d. methanol in aq. phase = 1.751 g/𝑆𝑆𝑚𝑚3

𝑐𝑐𝐺𝐺, 𝐺𝐺𝑆𝑆𝑟𝑟d. methanol in aq. phase = 109𝑙𝑙𝑏𝑏/𝑀𝑀𝑀𝑀𝑆𝑆𝐶𝐶𝑀𝑀

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 Step 09 :

Determine required methanol in vapor phase:

Using the graphical correlation, determine the methanol fraction in vapor phase:

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 To find methanol in vapour phase

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 To find methanol in vapour phase

0.92

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 Step 09 :

Determine required methanol in vapor phase:

𝑚𝑚𝑆𝑆𝐺𝐺ℎ𝐺𝐺𝑙𝑙𝑐𝑐𝑙𝑙 𝑆𝑆𝑙𝑙 𝐺𝐺𝐺𝐺𝑆𝑆𝑐𝑐𝐺𝐺 𝑆𝑆ℎ𝐺𝐺𝑏𝑏𝑆𝑆 = 0.92 × 𝑤𝑤𝑆𝑆𝑆𝑆𝑔𝑔ℎ𝐺𝐺 𝑆𝑆𝑆𝑆𝐺𝐺𝑆𝑆𝑆𝑆𝑙𝑙𝐺𝐺 𝑐𝑐𝑆𝑆 𝑚𝑚𝑆𝑆𝐺𝐺ℎ𝐺𝐺𝑙𝑙𝑐𝑐𝑙𝑙 𝑆𝑆𝑙𝑙 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺

𝑚𝑚𝑆𝑆𝐺𝐺ℎ𝐺𝐺𝑙𝑙𝑐𝑐𝑙𝑙 𝑆𝑆𝑙𝑙 𝐺𝐺𝐺𝐺𝑆𝑆𝑐𝑐𝐺𝐺 𝑆𝑆ℎ𝐺𝐺𝑏𝑏𝑆𝑆 = 0.92 × 34% = 31.28 𝑙𝑙𝑏𝑏/𝑀𝑀𝑀𝑀𝑆𝑆𝐶𝐶𝑀𝑀

𝑐𝑐𝐺𝐺, 𝑚𝑚𝑆𝑆𝐺𝐺ℎ𝐺𝐺𝑙𝑙𝑐𝑐𝑙𝑙 𝑆𝑆𝑙𝑙 𝐺𝐺𝐺𝐺𝑆𝑆𝑐𝑐𝐺𝐺 𝑆𝑆ℎ𝐺𝐺𝑏𝑏𝑆𝑆 = 31.28 𝑙𝑙𝑏𝑏

𝑀𝑀𝑀𝑀𝑆𝑆𝐶𝐶𝑀𝑀 = 0.5 𝑔𝑔/𝑆𝑆𝑚𝑚3

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 Step 10 :

Determine Total Injection rate of methanol:

𝑇𝑇𝑐𝑐𝐺𝐺𝐺𝐺𝑙𝑙 𝐼𝐼𝑙𝑙𝐼𝐼𝑆𝑆𝑆𝑆𝐺𝐺𝑆𝑆𝑐𝑐𝑙𝑙 𝑅𝑅𝐺𝐺𝐺𝐺𝑆𝑆 = 𝑉𝑉𝐺𝐺𝑆𝑆𝑐𝑐𝐺𝐺 𝐺𝐺𝑆𝑆𝑟𝑟𝑠𝑠𝑆𝑆𝐺𝐺𝑆𝑆𝑚𝑚𝑆𝑆𝑙𝑙𝐺𝐺 + 𝐴𝐴𝑟𝑟𝑠𝑠𝑆𝑆𝑐𝑐𝑠𝑠𝑏𝑏 𝐺𝐺𝑆𝑆𝑟𝑟𝑠𝑠𝑆𝑆𝐺𝐺𝑆𝑆𝑚𝑚𝑆𝑆𝑙𝑙𝐺𝐺

𝑇𝑇𝑐𝑐𝐺𝐺𝐺𝐺𝑙𝑙 𝐼𝐼𝑙𝑙𝐼𝐼𝑆𝑆𝑆𝑆𝐺𝐺𝑆𝑆𝑐𝑐𝑙𝑙 𝑅𝑅𝐺𝐺𝐺𝐺𝑆𝑆 = 0.5 + 1.715 = 2.251𝑔𝑔/𝑆𝑆𝑚𝑚3

𝑇𝑇𝑐𝑐𝐺𝐺𝐺𝐺𝑙𝑙 𝐼𝐼𝑙𝑙𝐼𝐼𝑆𝑆𝑆𝑆𝐺𝐺𝑆𝑆𝑐𝑐𝑙𝑙 𝑅𝑅𝐺𝐺𝐺𝐺𝑆𝑆 = 2.251𝑔𝑔 𝑆𝑆𝑚𝑚3

= 140.5 𝑙𝑙𝑏𝑏/𝑀𝑀𝑀𝑀𝑆𝑆𝐶𝐶𝑀𝑀

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ACTIVITY 02: Solve the problem yourself:

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Activity 02: Determine injection rate of methanol to prevent hydrate formation.

 Input (given) data:

 Given gas composition is as follows:

Parameter Value

Reservoir pressure 76 bar

Reservoir temperature 80 oC

Molecular weight of air 28.96 g/mol

Pipeline pressure 76 bar

Pipeline temperature 4 oC

Component Volume fraction

Methane 0.82

Ethane 0.055

Propane 0.04

Carbon dioxide 0.002

Nitrogen 0.083

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Gas Hydrate Formation Control

 Step 01: Calculate Specific gravity of gas using the given composition:

38

Component Volume fraction MW (g/mol) Volume Fraction*MW

Methane 0.82

Ethane 0.055

Propane 0.04

Carbon dioxide 0.002

Nitrogen 0.083

𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺𝐺𝐺 = d = 𝑀𝑀𝑀𝑀 𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 𝑀𝑀𝑀𝑀 𝑎𝑎𝑚𝑚𝑚𝑚

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Gas Hydrate Formation Control

 Step 01: Calculate Specific gravity of gas using the given composition:

39

Component Volume fraction MW (g/mol) Volume Fraction*MW

Methane 0.82 16.04 13.1528 Ethane 0.055 30.07 1.65385 Propane 0.04 44.1 1.764 Carbon dioxide 0.002 44.01 0.08802 Nitrogen 0.083 28.01 2.32483

Sum = 18.98

𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺𝐺𝐺 = d = 𝑀𝑀𝑀𝑀 𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 𝑀𝑀𝑀𝑀 𝑎𝑎𝑚𝑚𝑚𝑚

= 18.98 28.96

= 0.655

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 Step 02:

Calculation of Hydrate formation temperature:

40

𝐺𝐺𝑓𝑓 deg 𝐶𝐶 = −6.44 − 3.79 𝑑𝑑2

+ 7.68𝑙𝑙𝑙𝑙 𝑃𝑃 𝑏𝑏𝐺𝐺𝐺𝐺𝑏𝑏

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 Step 02:

Calculation of Hydrate formation temperature:

41

𝐺𝐺𝑓𝑓 = −6.44 − 3.79

0.6552 + 7.68𝑙𝑙𝑙𝑙 76

𝐺𝐺𝑓𝑓 = 18 ℃

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 Make a Judgement whether hydrate will form or not?

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 Yes, Hydrates will form.

 The reason is that the pipeline temperature (4 oC) is well below the hydrate formation temperature (calculate in previous step as 18 oC).

 If the pipeline temperature is well above the hydrate formation temperature, then hydrates do not form.

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 Step 03:

a) Determine water content of saturated gas leaving the separator:

Pressure = 76 bar = 1103 psia

Temperature = 80 ℃ = 176 ℉

Use McKetta and Wehe Graphical Correlation

℉ = (℃ ∗ 9/5) +32

1 𝑏𝑏𝐺𝐺𝐺𝐺 =14.5 psi

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380 lb/MMSCF

176 oF

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0.995

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 Step 03 :

From McKetta and Wehe Graphical Correlation

𝑏𝑏𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆𝑑𝑑 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺 𝑆𝑆𝑐𝑐𝑙𝑙𝐺𝐺𝑆𝑆𝑙𝑙𝐺𝐺 𝑆𝑆𝑐𝑐𝐺𝐺𝐺𝐺𝑆𝑆𝑆𝑆𝐺𝐺𝑆𝑆𝑑𝑑 = 380 × 0.995

𝑏𝑏𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆𝑑𝑑 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺 𝑆𝑆𝑐𝑐𝑙𝑙𝐺𝐺𝑆𝑆𝑙𝑙𝐺𝐺 𝑆𝑆𝑐𝑐𝐺𝐺𝐺𝐺𝑆𝑆𝑆𝑆𝐺𝐺𝑆𝑆𝑑𝑑 = 378.1 𝑙𝑙𝑏𝑏/𝑀𝑀𝑀𝑀𝑆𝑆𝐶𝐶𝑀𝑀

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 Step 03 :

b)Determine water content of saturated gas at the pipeline conditions:

Use values obtained from McKetta and Wehe Graphical Correlation

Pipeline pressure 76 bar

Pipeline temperature 4 oC

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8.5 lb/MMSCF

~40 oF

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1 40oF

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 Step 03 :

From McKetta and Wehe Graphical Correlation, at pipeline conditions:

𝑏𝑏𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆𝑑𝑑 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺 𝑆𝑆𝑐𝑐𝑙𝑙𝐺𝐺𝑆𝑆𝑙𝑙𝐺𝐺 𝑆𝑆𝑐𝑐𝐺𝐺𝐺𝐺𝑆𝑆𝑆𝑆𝐺𝐺𝑆𝑆𝑑𝑑 = 8.5 × 1

𝑏𝑏𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆𝑑𝑑 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺 𝑆𝑆𝑐𝑐𝑙𝑙𝐺𝐺𝑆𝑆𝑙𝑙𝐺𝐺 𝑆𝑆𝑐𝑐𝐺𝐺𝐺𝐺𝑆𝑆𝑆𝑆𝐺𝐺𝑆𝑆𝑑𝑑 = 8.5 𝑙𝑙𝑏𝑏/𝑀𝑀𝑀𝑀𝑆𝑆𝐶𝐶𝑀𝑀

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 Step 04 :

Determine the reduction in saturated water content:

𝑏𝑏𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆𝑑𝑑 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺 𝑆𝑆𝑐𝑐𝑙𝑙𝐺𝐺𝑆𝑆𝑙𝑙𝐺𝐺 = 𝑏𝑏𝐺𝐺𝐺𝐺. 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺 𝑏𝑏𝑆𝑆𝑆𝑆𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝑐𝑐𝐺𝐺 − 𝑏𝑏𝐺𝐺𝐺𝐺. 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺(𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑙𝑙𝑆𝑆𝑙𝑙𝑆𝑆)

𝑏𝑏𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆𝑑𝑑 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺 𝑆𝑆𝑐𝑐𝑙𝑙𝐺𝐺𝑆𝑆𝑙𝑙𝐺𝐺 = 378.1 − 8.5 = 369.6 𝑙𝑙𝑏𝑏/𝑀𝑀𝑀𝑀𝑆𝑆𝐶𝐶𝑀𝑀

1 𝑙𝑙𝑏𝑏 𝑀𝑀𝑀𝑀𝑆𝑆𝐶𝐶𝑀𝑀⁄ = 0.01602 𝑔𝑔/𝑆𝑆𝑚𝑚3

Or, 𝑏𝑏𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆𝑑𝑑 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺 𝑆𝑆𝑐𝑐𝑙𝑙𝐺𝐺𝑆𝑆𝑙𝑙𝐺𝐺 = 5.92 𝑔𝑔/𝑆𝑆𝑚𝑚3

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 Step 05:

Determine Mole fraction of water using Neilson and Bucklin equation:

𝑥𝑥𝑤𝑤 = 𝑆𝑆𝑥𝑥𝑆𝑆 ∆𝐺𝐺 −72

∆𝐺𝐺 = ℎ𝐺𝐺𝑑𝑑𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆 𝑆𝑆𝑐𝑐𝐺𝐺𝑚𝑚𝐺𝐺𝐺𝐺𝑆𝑆𝑐𝑐𝑙𝑙 𝐺𝐺𝑆𝑆𝑚𝑚𝑆𝑆𝑆𝑆𝐺𝐺𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝑆𝑆 − 𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑙𝑙𝑆𝑆𝑙𝑙𝑆𝑆 𝐺𝐺𝑆𝑆𝑚𝑚𝑆𝑆𝑆𝑆𝐺𝐺𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝑆𝑆

∆𝐺𝐺 deg 𝐶𝐶 = −72 𝑙𝑙𝑙𝑙 𝑥𝑥𝑤𝑤

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 Step 05:

Determine Mole fraction of water using Neilson and Bucklin equation:

𝑥𝑥𝑤𝑤 = 𝑆𝑆𝑥𝑥𝑆𝑆 ∆𝐺𝐺 −72

= 𝑆𝑆𝑥𝑥𝑆𝑆 14 −72

= 0.823

∆𝐺𝐺 = ℎ𝐺𝐺𝑑𝑑𝐺𝐺𝐺𝐺𝐺𝐺𝑆𝑆 𝑆𝑆𝑐𝑐𝐺𝐺𝑚𝑚𝐺𝐺𝐺𝐺𝑆𝑆𝑐𝑐𝑙𝑙 𝐺𝐺𝑆𝑆𝑚𝑚𝑆𝑆𝑆𝑆𝐺𝐺𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝑆𝑆 − 𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑙𝑙𝑆𝑆𝑙𝑙𝑆𝑆 𝐺𝐺𝑆𝑆𝑚𝑚𝑆𝑆𝑆𝑆𝐺𝐺𝐺𝐺𝐺𝐺𝑠𝑠𝐺𝐺𝑆𝑆

∆𝐺𝐺 = 18 − 4 = 14.0𝑐𝑐𝐶𝐶

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 Step 06:

Determine Mole fraction of methanol:

𝑥𝑥𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚 = 1 − 𝑥𝑥𝑤𝑤

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 Step 06:

Determine Mole fraction of methanol:

𝑥𝑥𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚 = 1 − 0.823 = 0.177

These are mole fractions – we require weight fraction to be able to specify injection rate in useful units

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 Step 07:

Determine weight fraction of methanol:

𝑤𝑤𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚 = 𝑥𝑥𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚𝑀𝑀𝑀𝑀𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚

𝑥𝑥𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚𝑀𝑀𝑀𝑀𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚 + 𝑥𝑥𝑤𝑤𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚𝑀𝑀𝑀𝑀𝑤𝑤𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚

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 Step 07:

Determine weight fraction of methanol:

𝑤𝑤𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚 = 𝑥𝑥𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚𝑀𝑀𝑀𝑀𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚

𝑥𝑥𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚𝑀𝑀𝑀𝑀𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚 + 𝑥𝑥𝑤𝑤𝑀𝑀𝑀𝑀𝑤𝑤𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚

𝑤𝑤𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚 = 0.177 × 32

0.177 × 32) + (0.823 × 18

𝑤𝑤𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚 = 0.276 𝑤𝑤𝑆𝑆𝑆𝑆𝑔𝑔ℎ𝐺𝐺 fraction = 27.6 weight %

𝑤𝑤𝑤𝑤𝑎𝑎𝑚𝑚𝑚𝑚𝑚𝑚 = 1 − 0.276 = 0.724 = 72.4 𝑤𝑤𝑆𝑆𝑆𝑆𝑔𝑔ℎ𝐺𝐺 %

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 Step 08:

Determine required methanol in aqueous phase:

𝐺𝐺𝑆𝑆𝑟𝑟d. methanol in aq. phase = 0.276 0.724

∗ 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺 𝑆𝑆𝑐𝑐𝑙𝑙𝐺𝐺𝑆𝑆𝑙𝑙𝐺𝐺

𝐺𝐺𝑆𝑆𝑟𝑟d. methanol in aq. phase = 0.382 ∗ 5.92 = 2.26

𝐺𝐺𝑆𝑆𝑟𝑟d. methanol in aq. phase = 2.26 𝑔𝑔 /𝑆𝑆𝑚𝑚3 𝑐𝑐𝐺𝐺, 𝐺𝐺𝑆𝑆𝑟𝑟d. methanol in aq. phase = 141 𝑙𝑙𝑏𝑏/𝑀𝑀𝑀𝑀𝑆𝑆𝐶𝐶𝑀𝑀

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 Step 09 :

Determine required methanol in vapor phase:

Using the graphical correlation, determine the methanol fraction in vapor phase:

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 To find methanol in vapour phase

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 To find methanol in vapour phase

~ 0.94

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 Step 09 :

Determine required methanol in vapor phase:

𝑚𝑚𝑆𝑆𝐺𝐺ℎ𝐺𝐺𝑙𝑙𝑐𝑐𝑙𝑙 𝑆𝑆𝑙𝑙 𝐺𝐺𝐺𝐺𝑆𝑆𝑐𝑐𝐺𝐺 𝑆𝑆ℎ𝐺𝐺𝑏𝑏𝑆𝑆 = 0.94 × 𝑤𝑤𝑆𝑆𝑆𝑆𝑔𝑔ℎ𝐺𝐺 𝑆𝑆𝑆𝑆𝐺𝐺𝑆𝑆𝑆𝑆𝑙𝑙𝐺𝐺 𝑐𝑐𝑆𝑆 𝑚𝑚𝑆𝑆𝐺𝐺ℎ𝐺𝐺𝑙𝑙𝑐𝑐𝑙𝑙 𝑆𝑆𝑙𝑙 𝑤𝑤𝐺𝐺𝐺𝐺𝑆𝑆𝐺𝐺

𝑚𝑚𝑆𝑆𝐺𝐺ℎ𝐺𝐺𝑙𝑙𝑐𝑐𝑙𝑙 𝑆𝑆𝑙𝑙 𝐺𝐺𝐺𝐺𝑆𝑆𝑐𝑐𝐺𝐺 𝑆𝑆ℎ𝐺𝐺𝑏𝑏𝑆𝑆 = 0.92 × 27.6% = 26 𝑙𝑙𝑏𝑏/𝑀𝑀𝑀𝑀𝑆𝑆𝐶𝐶𝑀𝑀

𝑐𝑐𝐺𝐺, 𝑚𝑚𝑆𝑆𝐺𝐺ℎ𝐺𝐺𝑙𝑙𝑐𝑐𝑙𝑙 𝑆𝑆𝑙𝑙 𝐺𝐺𝐺𝐺𝑆𝑆𝑐𝑐𝐺𝐺 𝑆𝑆ℎ𝐺𝐺𝑏𝑏𝑆𝑆 = 26 𝑙𝑙𝑏𝑏

𝑀𝑀𝑀𝑀𝑆𝑆𝐶𝐶𝑀𝑀 = 0.416 𝑔𝑔/𝑆𝑆𝑚𝑚3

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 Step 10 :

Determine Total Injection rate of methanol:

𝑇𝑇𝑐𝑐𝐺𝐺𝐺𝐺𝑙𝑙 𝐼𝐼𝑙𝑙𝐼𝐼𝑆𝑆𝑆𝑆𝐺𝐺𝑆𝑆𝑐𝑐𝑙𝑙 𝑅𝑅𝐺𝐺𝐺𝐺𝑆𝑆 = 𝑉𝑉𝐺𝐺𝑆𝑆𝑐𝑐𝐺𝐺 𝐺𝐺𝑆𝑆𝑟𝑟𝑠𝑠𝑆𝑆𝐺𝐺𝑆𝑆𝑚𝑚𝑆𝑆𝑙𝑙𝐺𝐺 + 𝐴𝐴𝑟𝑟𝑠𝑠𝑆𝑆𝑐𝑐𝑠𝑠𝑏𝑏 𝐺𝐺𝑆𝑆𝑟𝑟𝑠𝑠𝑆𝑆𝐺𝐺𝑆𝑆𝑚𝑚𝑆𝑆𝑙𝑙𝐺𝐺

𝑇𝑇𝑐𝑐𝐺𝐺𝐺𝐺𝑙𝑙 𝐼𝐼𝑙𝑙𝐼𝐼𝑆𝑆𝑆𝑆𝐺𝐺𝑆𝑆𝑐𝑐𝑙𝑙 𝑅𝑅𝐺𝐺𝐺𝐺𝑆𝑆 = 2.26 + 0.416 = 2.675𝑔𝑔/𝑆𝑆𝑚𝑚3

𝑇𝑇𝑐𝑐𝐺𝐺𝐺𝐺𝑙𝑙 𝐼𝐼𝑙𝑙𝐼𝐼𝑆𝑆𝑆𝑆𝐺𝐺𝑆𝑆𝑐𝑐𝑙𝑙 𝑅𝑅𝐺𝐺𝐺𝐺𝑆𝑆 = 2.675𝑔𝑔 𝑆𝑆𝑚𝑚3

= 167 𝑙𝑙𝑏𝑏/𝑀𝑀𝑀𝑀𝑆𝑆𝐶𝐶𝑀𝑀

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Descriptive Questions:

 What are the favourable conditions for gas hydrates?

 What are the remedial treatments to prevent hydrate formation?

 What is the structure of gas hydrate?

 Please consult lecture slides for ‘Week 6’

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