COPYRIGHTcloud1.activelearner.com/contentcloud/portals/hosted3/PetroAcademy/GAS... · 1Rafael Mendes, “Rheological behavior and modeling of waxy crude oils in transient flows”,

Introduction

Welcome to the Introduction to Production and Gas Processing Facilities core module

In this module, we are going to do a high-level review of production facilities and gasprocessing facilities

Introduction

SectionOne

State typical crude oil and produced water specifications Describe process flows for each stream in production facilities List problems associated with and strategies to deal with solids production,

e.g. sand, wax, asphaltenes

SectionTwo

List the components, including contaminants, found in produced gas streams State typical natural gas sales or transportation specifications Calculate higher heating value and Wobbe number List the products of a typical natural gas processing plant, their associated

markets, and describe common terminology

SectionThree

Describe typical process flows for each stream in gas processing facilities Explain the difference between gas conditioning to meet a HCDP

specification and gas processing to recover NGLs Describe shrinkage and how it is calculated

SectionOne

State typical crude oil and produced water specifications Describe process flows for each stream in production facilities List problems associated with and strategies to deal with solids production,

e.g. sand, wax, asphaltenes

SectionTwo

List the components, including contaminants, found in produced gas streams State typical natural gas sales or transportation specifications Calculate higher heating value and Wobbe number List the products of a typical natural gas processing plant, their associated

markets, and describe common terminology

SectionThree

Describe typical process flows for each stream in gas processing facilities Explain the difference between gas conditioning to meet a HCDP

specification and gas processing to recover NGLs Describe shrinkage and how it is calculated

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Introduction to Production and Gas Processing Facilities Core ═════════════════════════════════════════════════════════════════════════

© PetroSkills, LLC. All rights reserved._____________________________________________________________________________________________

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Production Facilities

Introduction to Production and Gas Processing Facilities Core

This section will cover the following learning objectives:

Learning Objectives

State typical crude oil and produced water specifications

Describe process flows for each stream in production facilities

List problems associated with and strategies to deal with solids production(e.g., sand, wax, asphaltenes)COPYRIG

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Crude Oil Value Chain

Why Is Processing Necessary?

To meet sales/disposal specifications• Crude oil / natural gas / NGLs

– Specifications are set contractually by:

1) The buyer

2) The transporter, or

3) By subsequent processing requirements

• Water– Disposal specifications are set externally by regulatory bodies or internally by reservoir/production

requirements

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Crude Oil Specifications

Water content (BS&W)• Typically varies from 0.3 to 3.0 vol%

• May be set by salt specification

Crude Oil Dehydration or TreatingWash Tanks/Settling Tanks/GunbarrelsHeater TreatersElectrostatic Treaters

Heater Treaters:

Used to heat the oil to lower its viscosity,

which makes it easier for water droplets to settle out of the oil.


Water content (BS&W)• Typically varies from 0.3 to 3.0 vol%

• May be set by salt specification

Crude Oil Dehydration or TreatingWash Tanks/Settling Tanks/GunbarrelsHeater TreatersElectrostatic Treaters

Electrostatic Treaters:

A high voltage electric field that causes water droplets to vibrate and collide and form larger droplets that can more

easily settle out by gravity.

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Vapor pressure• Typically near 1 atm, e.g., 10 psia [69 kPa],

12 psia [83 kPa], etc.

• Can be specified as a True Vapor Pressure(TVP) or Reid Vapor Pressure (RVP)

Crude Oil StabilizationStage SeparationCrude Oil Stabilizers

Stage Separation:

The most common way to meet a vapor pressure specification is to simply flash the oil from higher

pressures to lower pressures using a series of separators. The volatile components vaporize in

each separator and are removed from the oil.


Vapor pressure• Typically near 1 atm, e.g., 10 psia [69 kPa],

12 psia [83 kPa], etc.

• Can be specified as a True Vapor Pressure(TVP) or Reid Vapor Pressure (RVP)

Crude Oil StabilizationStage SeparationCrude Oil Stabilizers

Crude OilStabilizers:

A distillation process that flashes out the volatile components

by the addition of heat.

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Salt• Typical specification is 10 lb/1000 Bbl [30

g/m3]

• When the salt content > 200,000 to 300,000ppm, the BS&W of the oil leaving the lastdesalter stage should be 0.1% or lower

DesaltingDesalters (basically crude oil dehydration but salt content of water is diluted by injecting fresh water into the oil)

Desalting crude oilrequires two steps:

1) Dilute the salt content of theproduced water by mixing fresh

water into the oil stream.

2) Dehydrate the oil to a verylow BS&W specification to

minimize the amount of water in the oil.


H2S• Typical specification is 50 ppmw

• Don’t confuse with organic sulfur

H2S StrippingHeat and stripping gas

Heat and Stripping Gas:

When we talk about an H2S specification, we're not talking

about organic sulfur, we're talking about soluble H2S in the crude oil. The most common way to meet

the H2S specification is to heat the oil and inject sweet natural gas to

strip the H2S out of the oil.

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Produced Water Specifications

Typical disposal options• Onshore

– Reinject into reservoir or waste water aquifer

– Surface disposal

– Evaporation ponds

• Offshore

– Reinjection

– Disposal to sea


Hydrocarbon content• Dispersed/dissolved

• Offshore specifications vary from 15-50 mg/l

• Lower in inland and coastal waters

• No fixed specification for reinjection—set byreservoir characteristics

DeoilingSkim TanksCorrugated Plate and Parallel Plate Interceptors (CPI and PPI)HydrocyclonesGas Flotation Units

Deoiling:

The process of removing

hydrocarbons from the water.

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Solids• Sand, corrosion products, scales

• Control of solids is very important inreinjection systems

FiltrationSettling tanksSeveral different types of flow-through filters

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Production Facility Block Diagram

Production Facility Block Diagram

Crude Oil / Condensate

Storage

Compression (optional)

Compression

Gas Processing

Crude Oil / Condensate

Stabilization & Dehydration

Produced Water Treating

Gas

Oil

Oil

Water

Water OilWater to Disposal

(Reinjection or Sea)

Crude Oil / Condensate Sales

NGL Sales

Gas Sales or Reinjection

CO2 and / or Sulfur Sales

Untreated Gas To Reinjection (optional)

Reservoir

Compression (optional)

Gas / Oil Water Separation

Oil Storage Oil StorageWater

Storage

Treater

VaporRecovery Unit

Circ. Pump

Pump

Oil

Vent

To Pit

Test Separator

GAS

GAS

Water

Production Separator

Inlet Production Manifold

Field Flow Lines

Heated FWKO

Example Onshore Oil Production Facility

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Oil export1850 psig [128 barg]

Gas export1850 psig [128 barg]

To FuelGas System

110°F [43°C]1200 psig [83 barg]

120°F [49°C]1200 psig [83 barg] 120°F

[49°C]500 psig[34 barg] 130°F

[54°C]180 psig

[12.4 barg] 150°F[66°C]

50 psig[3.5 barg]

150°F[66°C]4 psig

[0.3 barg]

Example Deepwater GoM Platform

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Paraffin (Wax) Deposition

1Rafael Mendes, “Rheological behavior and modeling of waxy crude oils in transient flows”, University of Paris-Est, 2015.

• You will remember that one of the topics we mentioned inthe crude oil value chain discussion was the presence ofsolids in the production stream.

• The first solid we will discuss is wax or paraffin.

• Waxy crude oils will have a significant quantity of long,usually straight-chain alkane type molecules, that at roomtemperature, exist as a solid.

• As an example, n-C20, also referred to as isocane, has amelting point of 27°C [80°F].

• A crude oil containing significant amounts of alkane (orparaffin) hydrocarbon molecules heavier than about C18 willoften exhibit wax deposition in production and pipelinesystems.

Paraffin Deposits in Piping

Waxy Crude Oil Sample1



2. Pour pointThe temperature at which a fluid ceases to flow. Highpour points usually occur in crude oils that havesignificant paraffin content. This phenomenon can occurwith light oils as well as heavy oils

1. Cloud pointThe temperature at which wax crystals first start to formin a crude oil. Also referred to as the Wax AppearanceTemperature (WAT).



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• Wax can precipitate in production tubing, flowlines, surfaceproduction facilities and crude oil or condensate pipelines.

• Wax precipitation increases with decreasing temperatureresulting in a rapid increase in viscosity.

• Waxy crudes are non-Newtonian fluids which means theviscosity of the crude changes with the shear rate.

• The fluid’s resistance to flow depends on the amount ofenergy imparted to the fluid to make it flow.

• Crude will exhibit residual shear stress at zero shear rate.Meaning that once flow stops, it may not be possible to restartthe flow with the available pumping power.



Complex, polar, high MW organic moleculesconsisting of aromatic and naphthenic ringcompounds and alkane (paraffin) chains

May contain oxygen, nitrogen, and sulfuratoms as well as heavy metals such asvanadium and nickel

Are insoluble in paraffin solvents such asn-heptane but are soluble in aromatic solventssuch as toluene or xylene

Tend to precipitate as a hard crystalline solidin tubing, flowlines, surface equipment andproducing formations

Can also stabilize water-in-oil emulsionsmaking crude oil dehydration more difficult

Increasin

g A

sph

altene C

on

centratio

n in

Cru

de

Asphaltenes

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Complex, polar, high MW organic moleculesconsisting of aromatic and naphthenic ringcompounds and alkane (paraffin) chains

May contain oxygen, nitrogen, and sulfuratoms as well as heavy metals such asvanadium and nickel

Are insoluble in paraffin solvents such asn-heptane but are soluble in aromatic solventssuch as toluene or xylene

Tend to precipitate as a hard crystalline solidin tubing, flowlines, surface equipment and producing formations

Can also stabilize water-in-oil emulsionsmaking crude oil dehydration more difficult

Asphaltenes

Asphaltene Deposits in Piping

Increasin

g A

sph

altene C

on

centratio

n in

Cru

de

Asphaltenes

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Asphaltenes

Function of both temperature and pressure.

Asphaltene Precipitation Envelope1

1Numerous Authors, “Asphaltenes--Problematic but Rich in Potential”, Oilfield Review, Summer 2007

Asphaltenes



A reduction in pressure can cause asphaltenes to precipitate

Typically, this deposition occurs in the producing formation near the wellbore

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Asphaltenes



As the pressure continues to decrease, asphaltene deposition increases until we reach the bubblepoint of the crude oil

Asphaltenes



At the bubble point, gas starts to break out of the crude. Further reductions in pressure decreasedeposition

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Asphaltenes



It is important to test your crude oil in a laboratory for asphaltene precipitation before designing theproduction system

Wax and Asphaltenes: Prevention/Remediation Options

Paraffin ScraperCourtesy National Oilwell Varco

Wax Prevention• Thermal insulation and/or heat

tracing

• Dilution with a lighter substance suchas naphtha or condensate

• Paraffin inhibitors which interfere withcrystal growth

Wax Remediation• Hot oil treatments

• Paraffin scrapers

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Wax and Asphaltenes: Prevention/Remediation Options

Paraffin ScraperCourtesy National Oilwell Varco

Asphaltene Prevention

• Operate outside of the ashphalteneprecipitation envelope

• Asphaltene dispersants which keepasphaltene nanoaggreagatessuspended in the oil by preventingthem from forming clusters

Asphaltene Remediation

• Dissolve in solvent such as xylene orde-asphalted oil

• Mechanical removal such as scrapers,water blasting, steam injection

Sand

Formation Sand Production

Perforations

Sand is frequently produced with thereservoir fluids

Problems• Erosion in locations where high velocity or a

change of flow direction occurs

• Chokes, control valves, flowlines, pipingelbows, impingement plates, nozzles,pumps

• Plugging in piping and equipment where lowvelocities exist

• Lost capacity in separators due toaccumulation of sand

• Disposal: facility location or environmentalrestrictions may limit options

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Sand

Hydrocyclones

Mitigation and Remediation

Monitoring• Sand probes• Regular inspections

Equipment/Procedures• Sand traps/desanders• Jetting with HP water (often used in

separators)

Design• Proper piping layout and erosional velocity

limits• Use of erosion resistant and/or abrasion

resistant coatings• Use of gravel packs or sand screens

subsurface

Sand

Mitigation and Remediation

Monitoring• Sand probes• Regular inspections

Equipment/Procedures• Sand traps/desanders• Jetting with HP water (often used in

separators)

Design• Proper piping layout and erosional velocity

limits• Use of erosion resistant and/or abrasion

resistant coatings• Use of gravel packs or sand screens

subsurface

Centrifugal Separators

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Production Chemicals

Produced fluids often containa wide variety of chemicals.

Chemicals often interactcreating unforeseen operatingproblems in facilities• For example, corrosion inhibitors

often contain surfactants whichcan stabilize emulsions

Can contaminate product streams• A common hydrate inhibitor

like methanol can contaminatecondensate or NGL streams

Mitigation• Test for possible interactions and

their consequences prior to designof a chemical injection program

• Be aware of chemical properties,disposal regulations and productspecifications

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This section has covered the following learning objectives:

Learning Objectives

State typical crude oil and produced water specifications

Describe process flows for each stream in production facilities

List problems associated with and strategies to deal with solids production(e.g., sand, wax, asphaltenes)

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Natural Gas Value Chain and Introduction to Gas Processing



Learning Objectives

List the components, including contaminants, found in produced gas streams

State typical natural gas sales or transportation specifications

Calculate higher heating value and Wobbe number

List the products of a typical natural gas processing plant, their associated markets,and describe common terminology

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Natural Gas Value Chain


Gas processing facilityand the markets fornatural gasCOPYRIG

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Plant condensate is theliquid that condenses inthe pipeline system fromthe production facility tothe gas processing plant

As the gas cools in thepipeline, liquidhydrocarbons condense

It is similar to fieldcondensate, but is amuch lighter stream

Plant condensate has alower boiling point thanfield condensate


Sulfur recovery is oftenrequired when we havesour gas, which is gascontaining hydrogensulfide, H2S, and othersulfur components

These sulfur componentsare limited to very lowconcentration in the salesgas, so they have to beremoved in theprocessing plant

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Carbon dioxide is used ina particular type ofEnhanced Oil Recoveryproject called a miscibleflood

Carbon dioxide isreinjected back into theproducing reservoirwhere it increases oilrecovery

It is not unusual for theCO2 concentration in thesolution gas to be as highas 60-70 mol%


Gas lift is an artificial liftoption to reduce the backpressure on the reservoirso that we can maintainhigher production ratesand maximize oilrecovery

Gas lift valves on thetubing open periodicallyand allow the lift gas toenter the tubing

Lift gas is a recyclestream

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LNG is natural gas thatexists as a liquid atatmospheric pressure

Temperature is generallyabout -160° Celsius or-260° Fahrenheit

Transported in specialships (LNG tankers orLNG carriers)

About 10% of the naturalgas sold around the worldis transported as LNG


Compressed Natural Gasor CNG is compressed toapproximately 240 barg(3500 psig)

The volume reduction forCNG is around 300 to 1

Used in short haulapplications and is alsoused as a transportationfuel in vehicles such aspassenger vehicles anddelivery vans

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There are 3 primarymarkets for natural gas:

• Residential andCommercial

• Power Generation

• Industrial


The residential andcommercial market isnatural gas that is used inhomes and businessesfor space heating, waterheating, cooking, etc.

This market is highlyseasonal, with maximumdemand in the winter andminimum demand in thesummer

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The second market fornatural gas is electricpower generation

These plants havethermal efficiencies inexcess of 50%, which ismuch higher than otheroptions

This market is alsoseasonal, with highestdemand in the summerdue to air conditioning


The industrial market isdivided into two separateuses

One is as a fuel forrefineries, chemicalplants, steel mills, etc.

Natural gas is also usedas a feedstock to makechemicals

Accounts for only a smallportion of total demand

The least seasonal of thethree main natural gasmarkets

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Supply and demand arebalanced in two ways:• Adjusting production rate

• Natural gas storage

Adjusting productionrequires no addedinfrastructure

The most commonmethod of balancingsupply and demand is tostore gas in reservoirs

Aquifers, salt caverns orpeak shaving LNGfacilities are also used

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Contaminants

Natural gas is primarily methane, but alsocontains NGL components

Hydrogen Sulfide (H2S)• Extremely toxic• Flammable: combustion products are sulfur dioxide

(SO2) and water (H2O)• Corrosion in water-wet systems

– Pitting– Sulfide stress cracking

Other sulfur compounds• Mercaptans (RSH)• Example: methyl mercaptan (CH3SH)

– Strong odor

– Can cause fouling in amine solutions

– Toxic

• Carbonyl Sulfide (COS)

– Reacts to form H2S in the presence of water• Several others including elemental sulfur• All of these can cause corrosion• Contribute to total sulfur content

Nitrogen (N2)• Decreases heating value

Water (H2O)• Corrosion• Hydrates• Ice

Carbon Dioxide (CO2)• Corrosion in water-wet systems• Decreases heating value• Freezing in low temperature processes

– NGL extraction, LNG liquefaction

Mercury (Hg)• Toxic• Corrosion

– Aluminum corrosion

– Liquid metal embrittlement (brazed aluminum heat exchanges)

Oxygen• Corrosion in water-wet systems• Decreases heating value

Gas Quality Specifications

Energy Content• Heating value (Calorific value)

• Almost always refers to the higher or gross heating value, HHV or GHV

• The higher heating value is most commonly used in gas transportation and sales contracts

• The difference between the higher and lower heating value is simply the latent heat of the water that wasformed in the combustion process

• The higher heating value includes this latent heat; the lower heating value does not

𝐻𝐻𝑉 𝐻𝐻𝑉 𝑦

Heating value ofeach component

Mol fraction ofeach component

Higher heatingvalue

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Gas Quality Specifications

Wobbe Number (interchangeability)• Provides a simple, efficient and robust measure of gas interchangeability

WO

BB

E N

UM

BE

R

Upper Wobbe

Lower Wobbe

CO, NOx, Yellow Tipping

Lift Off, CO, Blow Out

OperatingRange

HEATING VALUE

Gas relative density

𝑊𝑁𝐻𝐻𝑉

𝑟𝑒𝑙. 𝜌 .

Heating value of the gasWobbe number

Impact of rel. ρ (s.g.): Gas flow through burner tip slows down as the gas gets heavier

HHV & rel. ρ (s.g.)

Exercise 1: HHV and Wobbe Number Calculation

𝑟𝑒𝑙 𝜌18.6628.96


𝑟𝑒𝑙 𝜌 .

𝑀𝑊 𝑀𝑊 𝑦 𝐻𝐻𝑉 𝐻𝐻𝑉 𝑦

𝑟𝑒𝑙 𝜌18.6628.96


𝑟𝑒𝑙 𝜌 .

𝑀𝑊 𝑀𝑊 𝑦 𝐻𝐻𝑉 𝐻𝐻𝑉 𝑦

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Gas Quality Specifications (cont’d.)

Hydrocarbon dew point (HCDP) temperature• Temperature and pressure at which liquid

hydrocarbons condense in the system

• Must specify a pressure or pressure range

• Often a cricondentherm specification

• Sometimes specified as a liquid content, e.g., mg/Nm3

• Typically higher in warm, tropical climates

Water• Can be expressed as a water dew point temperature,

e.g., -10 C @ 70 bar(14 F at 1000 psig)

– Must specify a pressure

• Can be expressed as a water concentration,e.g., 55 mg/Nm3 (3.5 lb/MMscf)

– Does not require a pressure

• Typically higher in warm tropical climates

Pressure

Temperature

Example Natural Gas Phase Envelope

Pressure

Temperature

Example Water Dewpoint Curve

Dew Point Line

BubblePoint Line

Critical Point

Gas Quality Specifications (cont’d.)

Sulfur compounds• Hydrogen Sulfide (H2S)

• Mercaptans (RSH)

• Total Sulfur– Includes all sulfur containing components in the gas stream

• Generally expressed in ppmv, mg/Nm3 or grains/100 scf(see conversion table)– Based on elemental sulfur

Other contaminants• CO2

• N2 + inerts (He, Ar, etc.)

• O2

• Other

– Dust, gums, waxes, glycol, methanol, Hg, etc.

Unit x = Unit

ppmv 1.43 mg/Nm3

ppmv 0.059 gr/100 scf

mg/Nm3 0.70 ppmv

gr/100 scf 16.9 ppmv

Shall be commercially free from objectionable odors, dust, or

other solid or liquid matter which might interfere with its

merchantability or cause injury to or interference with proper

operation of the lines, regulators, meters or other appliances

through which it flows

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EASEE1 Recommended Gas Specifications

Specification Units Min Max Comments

Wobbe Number kWh/m3 13.6 15.8

MJ/m3 49 57

Rel. Density 0.555 0.7

HCDP oC @ 1 to 70 bar ‐ ‐2

Water Dewpoint oC @ 70 bar ‐ ‐8 approx. 68 mg/Nm3

H2S + COS mg/Nm3 ‐ 5 Expressed as S

ppmv ‐ 3.5 "

Mercaptans (RSH) mg/Nm3 ‐ 6 Expressed as S

ppmv ‐ 4.2 "

Total Sulfur mg/Nm3 ‐ 30 Expressed as S

ppmv ‐ 21 "

CO2 mol % ‐ 2.5

O2 mol % ‐ 0.01

1 European Association for the Streamlining of Energy Exchange




MJ/m3 49 57





ppmv ‐ 3.5 "


ppmv ‐ 4.2 "


ppmv ‐ 21 "

CO2 mol % ‐ 2.5

O2 mol % ‐ 0.01


Wobbe Number from previous

slide:

49.89 MJ/m3COPYRIGHT



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MJ/m3 49 57





ppmv ‐ 3.5 "


ppmv ‐ 4.2 "


ppmv ‐ 21 "

CO2 mol % ‐ 2.5

O2 mol % ‐ 0.01


Impliedheating value specification:

36.5 – 47.7 MJ/m3

Example US Specifications - Rocky Mtn. Region


HHV Btu/scf 950 1200

MJ/Nm3 37.4 47.3

HCDP oF @ 100 to 1000 psi ‐ 15

Water Content lb/MMscf ‐ 5 25 oF DP@ 1000 psig

H2S grains/100 scf ‐ 0.25 Expressed as S

ppmv ‐ 4.2 "

Mercaptans (RSH) grains/100 scf ‐ 0.25 to 2 Often not specified

ppmv ‐ 4.2 to 34 Expressed as S

Total Sulfur grains/100 scf ‐ 0.5 to 20 Expressed as S

ppmv ‐ 8.4 to 340 "

CO2 mol % ‐ 2 to 3

O2 ppmv ‐ 10‐10000

N2 mol % 3 Often not specified

CO2 + N2 + other inerts mol % 5

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Gas Quality Specifications (cont’d)

For gas entering a transmission system serving many customers, the specifications are typicallyset by the gas transporter and are generally non-negotiable.

For gas entering a transportation system where there is only one customer, such as a power plantor a chemical complex, the specifications are based on the buyer’s requirements and are typicallynegotiated between the buyer and the seller.

For example, a common CO2 specification for an open, multi-customer, transportation systemmight be 2.5 mol%. But for a pipeline system dedicated to one customer, the buyer might be ableto accept a gas with a much higher concentration of CO2, say 10 mol%. This could dramaticallydecrease the cost of the seller’s gas processing facility.

You will also see some flexibility in H2S specifications. As we have seen, a common specificationfor H2S in an open transmission system is about 4 ppmv. But there are some users, particularlypower plants, where an H2S concentration of 20 to 30 ppmv might not be an issue. If the buyer willagree to a higher H2S concentration, the cost of processing the gas can be reduced.

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Wobbe Number Specification Exercise

Question

Refer to the gas composition in the guided exercises

presented earlier. Assume this gas is transported in a

gas pipeline system with the EASEE specifications

discussed previously. It has been proposed to extract

the propane from this gas stream to serve a local LPG

market. If the propane is extracted, the new sales gas

composition is shown in the table on the left.

If the propane is extracted, will this gas still meet the Wobbe number

specification?

Answer: Without propane, the gas stream does not meet the minimum Wobbe

number specification, 48.87 vs. 49.

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Wobbe Number Specification Exercise Solution

New Wobbe number calculation shown below:

Comp mol% MW (yi)(Mwi) HHV, MJ/m3 (yi)(HHVi)

N2 3.09 28.01 0.87 0 0.00

CO2 1.03 44.01 0.45 0 0.00

C1 88.66 16.04 14.22 37.707 33.43

C2 7.22 30.07 2.17 66.067 4.77

C3 0.00 44.10 0.00 93.936 0.00

MW = 17.71 HHV = 38.20

rel. ρ = 0.611 Wobbe Number = 48.87

Without propane, the gas stream does not meet the minimum Wobbe numberspecification, 48.87 vs. 49

This exercise shows how gas sales or transportation specifications may limitextraction of NGL components

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CompLean Sweet

Non-Associated GasVery Lean Sweet

Shale GasLean High CO2

Gas Condensate GasRich SweetShale Gas

He 0.060 0.000 0.000 0.000

N2 2.408 0.078 0.654 0.380

CO2 0.472 1.921 10.071 0.633

H2S 0.000 0.000 0.000 0.000

C1 91.660 97.302 86.345 79.689

C2 3.896 0.645 1.840 12.020

C3 0.956 0.038 0.487 3.803

iC4 0.166 0.004 0.111 0.553

nC4 0.214 0.004 0.106 1.117

iC5 0.077 0.000 0.044 0.336

nC5 0.062 0.000 0.025 0.409

C6 0.062 0.000 0.036 0.473

C7+ 0.027 0.008 0.279 0.587

Total 100.000 100.000 100.000 100.000

Example Separator Gas Compositions, mol%

CompHP Sweet

Solution GasLP Sweet

Solution GasRich High CO2

Gas Condensate GasRich Sour

Gas Condensate Gas

He 0.000 0.000 0.000 0.000

N2 0.956 0.883 0.866 0.302

CO2 1.291 1.649 10.696 4.127

H2S 0.000 0.000 0.006 8.958

C1 83.518 65.352 74.089 73.478

C2 6.309 10.187 7.696 7.549

C3 4.574 12.277 3.827 2.617

iC4 0.496 1.581 0.379 0.503

nC4 1.454 4.459 1.068 1.007

iC5 0.375 0.919 0.227 0.403

nC5 0.364 0.843 0.314 0.302

C6 0.234 0.596 0.403 0.503

C7+ 0.427 1.255 0.429 0.252

Total 100.000 100.000 100.000 100.000

Example Separator Gas Compositions, mol%

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NGL Products

This slide provides an overview of NGL products and their markets as well as a reminder ofcommon terminology used in the oil and gas business

NGL Products

C2Petrochemical feedstock for manufacture of ethylene

C3Petrochemical feedstock for manufacture of propylene Fuel (LPG): Commercial and residential fuel in areas not on a natural gas gridGrain dryingOutdoor grillsMotor vehicle fuel

C4Iso: Refinery feedstock to alkylation unitPetrochemical feedstock for manufacture of iso-butylene and other light olefinsGasoline (petrol) blendingComponent in LPGNormal: Petrochemical feedstock for manufacture of n-butylene and other light olefinsFeedstock to isomerization unit for conversion to iC4

Gasoline (petrol) blendingComponent in LPG

C5+In refining and petrochemical business often known as light naphthaPetrochemical feedstock for manufacture of a range of light olefinsRefinery feedstock to reformer or isomerization unit

NGL: Natural Gas Liquid

LPG: Liquefied Petroleum Gas

LNG: Liquefied Natural Gas

CNG: Compressed Natural Gas

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Learning Objectives

List the components, including contaminants, found in produced gas streams

State typical natural gas sales or transportation specifications

Calculate higher heating value and Wobbe number

List the products of a typical natural gas processing plant, their associated markets, anddescribe common terminology

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NGL Recovery



Learning Objectives

Describe typical process flows for each stream in gas processing facilities

Explain the difference between gas conditioning to meet a HCDP specification and gasprocessing to recover NGLs

Describe shrinkage and how it is calculatedCOPYRIGHT



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Gas Processing Plant – Block Diagram

Gas Processing Objectives (Conditioning)

Meet sales gas specifications only – no further processing• Water removal

• CO2/Sulfur compound removal

• Hydrocarbon dew point (HCDP) control

Used when no profitable NGL market exists and/or NGL transportation/storage/distribution systemsare undeveloped

In addition to meeting sales gas specifications – further processing is undertaken to increase NGLrecovery

• NGLs more valuable as a saleable product than as a natural gas component– Ethane

– Propane

– Butanes

– Natural Gasoline (iC5+)

Extraction levels are limited by gas sales specifications (typically heating value) and economics

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NGL Extraction Levels

Gas conditioning to meet a hydrocarbon dew point specification which requires removalof a portion (60-70%) of the C5+ hydrocarbons in the gas stream

The heating value and Wobbe number of the sales gas are low and in some cases NGLrecovery may be limited by these gas quality specifications

NGL Extraction Economics

In general, we choose to extract NGLs from a gas stream when their value as an NGLproduct is greater than their value as a component in the sales gas stream

The reduction in the value of the sales gas stream due to the extraction of an NGLproduct is referred to as “shrinkage”

Example:• A natural gas stream contains 5 mol% propane (C3). The flowrate is

1.0 x 106 sm3/d [35.4 MMscfd]. If all of the propane is extracted from the gas in a gasprocessing plant, calculate the following:

– The reduction in the energy content of the gas stream due to propane extraction

– The value of this energy content reduction

– The amount of propane product recovered in tonnes/d [US gal/day]

– The value of the propane product if sold to an LPG buyer

– The net revenue from propane extraction

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• Reduction of energy content: As a gas, propane has a heating value of 93.936 MJ/sm3 [2,516.2 Btu/scf]– (1000000 sm3/d)(0.05)(93.936 MJ/sm3) = 4,697 GJ/d

– (35,400,000 scf/d)(0.05)(2516.2 Btu/scf) = 4,454 MMBtu/d

• Value of the energy content reduction (shrinkage): The gas price is $2.84/GJ [$3.00/MMBtu]– (4697 GJ/d)($2.84/GJ) = $13,350/d– (4,454 MMBtu/d)($3.00/MMBtu) = $13,350/d

• Quantity of propane is extracted in tonnes/d [US gal/day]: The volume ratio of propane is 0.5362 sm3/kg[36.404 scf/US gal]

– (1000000 sm3/d)(0.05)/(0.5362 sm3/kg)/1000 kg/mt = 93.25 tonnes/d– (35,400,000 scf/d)(0.05)/(36.404 scf/US gal)= 48,600 US gal/d

• Value of propane extracted: The propane price is $260/tonne [$0.499/US gal]– (93.25 tonnes/d)($260/mt) = $24,250/d– (48,600 US gal/d)($0.499/USgal) = $24,250/d

• Net revenue from propane extraction:– $24,250 – $13,350 = $10,900/d

The values shown in blue were taken from Tables 3A1(a) and (b)

in Chapter 3 of Volume 1


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Example

If the gas price in the previous example rose to $5.00/MMBtu [$4.74/GJ], would it still beeconomically viable to extract propane from the gas stream?

• Shrinkage:– (4697 GJ/d)($4.74/GJ) = $22,270/d

– (4,454 MMBtu/d)($5.00/MMBtu) = $22,270/d

• Net Revenue:– $24,250 – $22,270 = $1,980/d

Shrinkage Values for NGLs (US Units)

$0.455/US gal

$5.00/MMBtu

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Shrinkage Values for NGLs (SI Units)

$226/tonne

$4.74/GJ

Example

If the gas price is $5.00/MMBtu [$4.74/GJ] the net revenue from propane extraction isstill positive but not nearly as attractive as in the base case. What are some otherfactors you might consider in the decision to recover propane?

• Are the plant operating costs different if propane is not extracted from the gas?

• Will the recovery of butanes be adversely affected if propane is not extracted?

• Can we still meet the gas quality specifications if propane is not extracted?

– Heating value or Wobbe Index are the most likely gas properties that could fall outside of thespecification range.

• Are we obligated to pay “capacity reservation fees” for NGL pipeline and/or fractionationfacilities regardless of whether we extract propane or not?

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Example

NGL prices are closely related to crude oil prices because NGLs are usually sold intomarkets where they compete with crude oil products.

The shrinkage value of the NGL product is set by natural gas prices; so, when crudeoil prices are high relative to natural gas prices, NGL extraction economics aregenerally quite favorable.

On the other hand, when crude oil prices and natural gas prices are the same, theextraction of NGLs is difficult to justify.

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Gas Processing Facility Exercise

Question

A gas processing facility has the option of extracting ethane from the feed gas or

rejecting ethane to the export gas stream. The current price for ethane $0.21/US

gal [$156/tonne].

Use the following figures to answer the question.

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If the natural gas price is $4.00/MMBtu [$3.79/GJ], would they be more

likely to extract ethane or reject ethane?

Answer: The operator would be more likely to reject ethane than extract it since

ethane is worth more in the gas stream than as an NGL product.

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Gas Processing Facility Exercise Solution

$189/tonne

$0.26/US gal

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Learning Objectives

Describe typical process flows for each stream in gas processing facilities

Explain the difference between gas conditioning to meet a HCDP specification and gas processing to recover NGLs

Describe shrinkage and how it is calculated

Hydrocarbon Components and Physical Properties Core


Qualitative Phase Behavior and Vapor Liquid Equilibrium Core

Water / Hydrocarbon Phase Behavior Core

Thermodynamics and Application of Energy Balances Core

Fluid Flow Core

Relief and Flare Systems Core

Separation Core

Heat Transfer Equipment Overview Core

Pumps and Compressors Overview Core

Refrigeration, NGL Extraction and Fractionation Core

Contaminant Removal – Gas Dehydration Core

Contaminant Removal – Acid Gas and Mercury Removal Core

Gas Conditioning and Processing Core

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Documents

COPYRIGHTcloud1.activelearner.com/contentcloud/portals/hosted3/PetroAcademy/GAS... · 1Rafael Mendes, “Rheological behavior and modeling of waxy crude oils in transient flows”,