Chapter 7 Chapter 7 Separating and Treating Well FluidsSeparating and Treating Well Fluids

waterand gas oil, of Separation

gravity of force the

waterand gas oil, of Mixture -- produced fluids Well--

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Principles and Operation of Production SeparatorsPrinciples and Operation of Production Separators

─ ─ Gas, oil and water separation was achieved by Gas, oil and water separation was achieved by

the difference in gravity, or weight, of each fluid.the difference in gravity, or weight, of each fluid.

─ ─ Production separators do the same job, except they Production separators do the same job, except they

are built to handle a continuous-flow stream and are built to handle a continuous-flow stream and

have features to improve separation efficiency have features to improve separation efficiency

under flow conditions.under flow conditions.

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Three general types of separatorsThree general types of separators

─ ─ Horizontal separatorHorizontal separator ─ ─ for high-pressure and medium-pressure servicefor high-pressure and medium-pressure service

─ ─ Vertical separator Vertical separator ─ ─ for low-pressure service (generally)for low-pressure service (generally) ─ ─ Spherical separator Spherical separator ─ ─ more compact and cheapermore compact and cheaper ─ ─ limited separation space and liquid surge capacitylimited separation space and liquid surge capacity ─ ─ for low-volume remote platformsfor low-volume remote platforms

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Separators of Structure Internal

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Separation methodsSeparation methods

─ ─ Stage separation methodStage separation method

── Low-temperature separation methodLow-temperature separation method

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Stage separation method (two stage separation)Stage separation method (two stage separation)

Any number of separators may be used in stage separation as long as stage operates at successively lower pressures.

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Low-temperatures separation methodLow-temperatures separation method

It is used to handle the production from high-pressure gas It is used to handle the production from high-pressure gas wellswells

Well fluids – a mixture of gas & some light liquids Well fluids – a mixture of gas & some light liquids

Dehydration – the removal of water vapor from gasDehydration – the removal of water vapor from gas

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Low – temperature separation method Low – temperature separation method uses the cooling effect of expanding high – pressure gas uses the cooling effect of expanding high – pressure gas

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Low-temperature separation methodLow-temperature separation method

For high-pressure gas wells (well fluids: mixture of gas and For high-pressure gas wells (well fluids: mixture of gas and some light liquids)some light liquids)

─ ─ Dehydration to remove water vapor from gasDehydration to remove water vapor from gas

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Water-removal — before the oil can be delivered to the pipeline Water-removal — before the oil can be delivered to the pipeline

Free water – some of the water produced with the oil will not be Free water – some of the water produced with the oil will not be mixed with it ; this is known as free water .mixed with it ; this is known as free water .

Water-removalWater-removal

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Water removalWater removal

─ ─Treatment of free-water Free water knock out (FWKO)Treatment of free-water Free water knock out (FWKO)using

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Treatment of oil-water or water-oil emulsionTreatment of oil-water or water-oil emulsion

Water and oil are immiscible. Water and oil are immiscible. These two liquids will form an emulsion only These two liquids will form an emulsion only (1) if there is sufficient agitation to disperse one liquid as (1) if there is sufficient agitation to disperse one liquid as droplets in the other , and droplets in the other , and (2) if there is an emulsifying agent , or emulsifier , present.(2) if there is an emulsifying agent , or emulsifier , present. Emulsifying agents – asphalt Emulsifying agents – asphalt 瀝青 柏油瀝青 柏油 resinous substances resinous substances oil-soluble organic acids.oil-soluble organic acids.

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EmulsionsEmulsions Emulsion – a mixture in which one liquid, termed the Emulsion – a mixture in which one liquid, termed the dispersed phase, is uniformly distributed (usually as dispersed phase, is uniformly distributed (usually as minute globules, in another liquid, called the minute globules, in another liquid, called the continuous phase or the dispersion medium (phase))continuous phase or the dispersion medium (phase))

Oil – water emulsion –Oil – water emulsion – the oil is the dispersed phase, and the oil is the dispersed phase, and the water (is ) the dispersion medium (or continuous phase )the water (is ) the dispersion medium (or continuous phase )

Water-oil emulsion –Water-oil emulsion – the water is the dispersed phase, and the water is the dispersed phase, and the oil the dispersion mediumthe oil the dispersion medium

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Emulsions -- Emulsions -- continuecontinue

Stable emulsion – will not break down into its components Stable emulsion – will not break down into its components without some form of treating.without some form of treating.

Tight (difficult to break) or loose (easy to break) emulsionTight (difficult to break) or loose (easy to break) emulsion Depending on – Depending on – (1) the properties of the oil & water (1) the properties of the oil & water (2) the percentage of each found in the emulsion (2) the percentage of each found in the emulsion (3) type and amount of emulsifier present .(3) type and amount of emulsifier present .

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Treatment of oil-water or water-oil emulsionTreatment of oil-water or water-oil emulsion

Treatment of oil-water or water-oil emulsionTreatment of oil-water or water-oil emulsion

（（ 11 ）） HeatHeat

（（ 22 ）） ChemicalsChemicals

（（ 33 ）） ElectricityElectricity

（（ 44 ）） Combination of these (heater- treater) Combination of these (heater- treater)

flow treater or emulsion treated flow treater or emulsion treated

（（ 55 ）） Gun barrel or wash tank if emulsion is not stableGun barrel or wash tank if emulsion is not stable

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Application of heatApplication of heat One theory assumes that very small droplets, like those found iOne theory assumes that very small droplets, like those found i

n emulsions, are in constant motion even when the emulsion itn emulsions, are in constant motion even when the emulsion itself is not rest .self is not rest .

Application of heat Application of heat (1) Heat increases the movement are makes the droplets strike ea(1) Heat increases the movement are makes the droplets strike ea

ch other with greater force and frequency. ch other with greater force and frequency. (2) Heat also reduces the viscosity – the resistance to flow – of th(2) Heat also reduces the viscosity – the resistance to flow – of th

e oil.e oil.

Heater (Heater ( 加熱器加熱器 ))(1) direct heater (1) direct heater (2) Indirect heater—water bath (fig5.22 P.161)(2) Indirect heater—water bath (fig5.22 P.161)

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Application of chemicalsApplication of chemicals

One theory suggests that chemical should be used strictly to One theory suggests that chemical should be used strictly to neutralize the emulsifying agent. neutralize the emulsifying agent.

Thus, to break a water-in-oil emulsion, Thus, to break a water-in-oil emulsion, another emulsifying agent to produce oil-in-water emulsion another emulsifying agent to produce oil-in-water emulsion should be added.should be added.

Another theory suggests the chemicals should make the film Another theory suggests the chemicals should make the film of emulsifying agent around the water droplet in a water-in-oil of emulsifying agent around the water droplet in a water-in-oil emulsion very rigid. emulsion very rigid.

Thus, to break rigid film Thus, to break rigid film apply heat or apply heat or add chemical.add chemical.

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Heater-treaterHeater-treater

Heater-treater also called a flow treater or an emulsion treater.Heater-treater also called a flow treater or an emulsion treater.

Heater-treater (or call flow treater, or emulsion treater) Heater-treater (or call flow treater, or emulsion treater) apply the effects ofapply the effects of Chemicals, heat , settling, and often electricityChemicals, heat , settling, and often electricity

Any or all of the following elements may be included in a treater: Any or all of the following elements may be included in a treater: • oil-gas separator, oil-gas separator, • free-water knockout, free-water knockout, • heater, heater, • water, wash, filter section, water, wash, filter section, • stabilizing section, stabilizing section, • heat exchanger, and heat exchanger, and • electrostatic field.electrostatic field.

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Treater Treater

Treater can be operated at atmospheric pressure, Treater can be operated at atmospheric pressure, often be operated under low working pressure. often be operated under low working pressure. A low-pressure, second-stage separator as well as A low-pressure, second-stage separator as well as treating unit. treating unit. When flow-line pressure are low, it can be used as a When flow-line pressure are low, it can be used as a primary separator thus eliminating the need for a regular primary separator thus eliminating the need for a regular separator. (fig 5.25, P.164)separator. (fig 5.25, P.164)

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Treating natural gasTreating natural gas

Field processing of natural gas consist of four basic processes:Field processing of natural gas consist of four basic processes:

(1)(1) the gas must be separated from free liquids such as crude oil, the gas must be separated from free liquids such as crude oil, hydrocarbon condensate, water , and entrained solids,hydrocarbon condensate, water , and entrained solids,

(2) the gas must be processed to remove condensable and (2) the gas must be processed to remove condensable and recoverable H.C. vaporsrecoverable H.C. vapors

(3) the gas must be treated to remove condensable water vapor, (3) the gas must be treated to remove condensable water vapor, which might cause hydrate formationwhich might cause hydrate formation

(4) the gas must be treated to remove other undesirable (4) the gas must be treated to remove other undesirable components, such as hydrogen sulfide or carbon dioxide.components, such as hydrogen sulfide or carbon dioxide.

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Treating Natural GasTreating Natural GasThe primary treatments for natural gas involveThe primary treatments for natural gas involve（（ 11 ）） prevention of hydrate formationprevention of hydrate formation by applying heat and/or by applying heat and/or adding hydrate inhibitor: adding hydrate inhibitor: ammonia ammonia brine brine glycol (glycol ( 乙二醇乙二醇 )) methanol (methanol ( 甲醇甲醇 ) ) （（ 22 ）） dehydration, dehydration, absorption (absorption ( 吸收吸收 ) – Liquid ) – Liquid 乾燥劑乾燥劑 adsorption (adsorption ( 吸附吸附 ) – Solid ) – Solid 乾燥劑乾燥劑（（ 33 ）） The removal of undesirable components (HThe removal of undesirable components (H22SS 、、 COCO22)) Alkanolamine processAlkanolamine process Iron-sponge processIron-sponge process Glycol/amine processGlycol/amine process Sulfinol processSulfinol process Molecular-sieve removalMolecular-sieve removal

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Prevention of hydrate formationPrevention of hydrate formation

Water is always necessary for hydrate formation.Water is always necessary for hydrate formation. water always accelerates corrosion.water always accelerates corrosion.

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Phase diagram for a pure single componentPhase diagram for a pure single component

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Dehydration Dehydration meansmeans removal of water removal of water Water vapors (as well as certain other vapor) are removes Water vapors (as well as certain other vapor) are removes

from gas by eitherfrom gas by either (1) the absorption process, or(1) the absorption process, or (2) the adsorption process(2) the adsorption process

Absorption process --Absorption process -- Water vapor may be removed from natural gas by bubbling the Water vapor may be removed from natural gas by bubbling the

gas counter currently through certain liquids that have a gas counter currently through certain liquids that have a special attraction or affinity for water.special attraction or affinity for water.

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Dehydration Dehydration meansmeans removal of water removal of water

Adsorption --Adsorption -- Some solids also have an affinity for water, and when gas Some solids also have an affinity for water, and when gas

flows through a bed of such granular solids, the water is flows through a bed of such granular solids, the water is retained on the surface of the particles.retained on the surface of the particles.

Desiccant --Desiccant -- The liquid or the solids that has the affinity for water in either The liquid or the solids that has the affinity for water in either

process is called a desiccant.process is called a desiccant.

Dehydration equipmentDehydration equipment -- The liquid-desiccant dehydrator-- The liquid-desiccant dehydrator -- The solid-desiccant dehydrator-- The solid-desiccant dehydrator

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Removal of undesirable componentsRemoval of undesirable components

Alkanolamine processAlkanolamine process -- It is a continuous-operation liquid process that uses absorptio-- It is a continuous-operation liquid process that uses absorptio

n for the acid-gas removal, with subsequent heat addition to strin for the acid-gas removal, with subsequent heat addition to string the acid-gas component from absorbent solution.ng the acid-gas component from absorbent solution.

Other processes that are used to removal HOther processes that are used to removal H22S & COS & CO22 are are The Iron-sponge process,The Iron-sponge process, The glycol/amine process,The glycol/amine process, The sulfinol process, andThe sulfinol process, and The molecular-sieve removal.The molecular-sieve removal.

gases acid)(CO dioxideCarbon

S)(H sulfideHydrogen

2

2

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Typical Natural Gas ComponentsTypical Natural Gas Components

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Casinghead gasCasinghead gas -- gas produced with oil from an oil well.-- gas produced with oil from an oil well.

Residue gas Residue gas -- any gas suitable for as commercial natural gas that comes -- any gas suitable for as commercial natural gas that comes from a processing plant.from a processing plant.

Sweet gasSweet gas --the content of hydrogen sulfide, other sulfur compounds, --the content of hydrogen sulfide, other sulfur compounds, and carbon dioxide is low enough that gas may be sold and carbon dioxide is low enough that gas may be sold commercially without further effort to remove these commercially without further effort to remove these compounds.compounds.

Sour gas Sour gas --the opposite of sweet gas.--the opposite of sweet gas.

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Types of Natural Gas LiquidsTypes of Natural Gas Liquids Commercial propane (Commercial propane ( 丙烷丙烷 )) -- propane and/or propylene (at least 95%)-- propane and/or propylene (at least 95%) -- vapor pressure < 215 psig at 100 -- vapor pressure < 215 psig at 100 00FF

Commercial Butane (Commercial Butane ( 丁烷丁烷 )) -- butanes and/or Butane (at least 95%)-- butanes and/or Butane (at least 95%) -- vapor pressure < 70 psig at 100 -- vapor pressure < 70 psig at 100 00FF -- At least 95% must evaporate at 34 -- At least 95% must evaporate at 34 00F or lower in a F or lower in a standard test.standard test.

Liquefied Petroleum Gas (LPG)Liquefied Petroleum Gas (LPG) -- A mixture of commercial propane and commercial butane.-- A mixture of commercial propane and commercial butane. -- maximum vapor pressure < 215 psig at 100 -- maximum vapor pressure < 215 psig at 100 00FF At least 95% must evaporate at 34 At least 95% must evaporate at 34 00F or lower in a F or lower in a standard test. standard test.

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Types of Natural Gas LiquidsTypes of Natural Gas Liquids

Natural GasolineNatural Gasoline

--This petroleum product is extracted from natural gas--This petroleum product is extracted from natural gas --specifications:--specifications:

• Vapor pressure:10-34psiVapor pressure:10-34psi• Percentage evaporated at 140 F: 24-85%Percentage evaporated at 140 F: 24-85%• Percentage evaporated at 275 F: not less then 90%Percentage evaporated at 275 F: not less then 90%

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Vapor pressure, usually referred to as Reid vapor pressure (RVVapor pressure, usually referred to as Reid vapor pressure (RVP), used to designate grades.P), used to designate grades.

Motor fuels: 5-8psi RVPMotor fuels: 5-8psi RVP Very light oils (60-70AIP): 12psi RVPVery light oils (60-70AIP): 12psi RVP Natural gasoline product: 14-26 psi RVPNatural gasoline product: 14-26 psi RVP

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The Storage SystemThe Storage System

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The Storage SystemThe Storage SystemStock tanks (or storage tanks)Stock tanks (or storage tanks)

──Tank batteryTank battery ─ ─separation equipment separation equipment treating equipment tank batterytreating equipment tank battery storage facilities storage facilities

──stock tanks Bolted steel tank – 500 bbls or larger; assembled on locationstock tanks Bolted steel tank – 500 bbls or larger; assembled on location Welded steel tank – 90 bbl to several thousand bbls; Welded steel tank – 90 bbl to several thousand bbls;

welded in a shop and then transporte welded in a shop and then transported d as a complete unit to the site as a complete unit to the site

──Vapor Recovery SystemVapor Recovery System──LACT (Lease automatic custody transfer) unitLACT (Lease automatic custody transfer) unit Oil sampling thief-sampling methodOil sampling thief-sampling method bottle-sampling methodbottle-sampling method Gas samplingGas sampling

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Treatment of emulsionTreatment of emulsion

Therefore, Therefore, To break down a petroleum emulsion To break down a petroleum emulsion the properties of emulsifying agent must be the properties of emulsifying agent must be neutralized or destroyed .neutralized or destroyed .By application of By application of (1) heat(1) heat (2) chemicals(2) chemicals (3) electricity, or(3) electricity, or (4) combination of these (heater – treater )(4) combination of these (heater – treater )

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The well streamThe well stream

The well stream -- high-velocity, turbulent, The well stream -- high-velocity, turbulent,

constantly expanding mixture of gases and hydrocarbon liquids,constantly expanding mixture of gases and hydrocarbon liquids,

intimately mixed with water vapor, free water solids and intimately mixed with water vapor, free water solids and

other containment.other containment.

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The bottle testThe bottle test

-- It is used to help determine which chemical can most -- It is used to help determine which chemical can most effectively break the emulsion from a given well, lease, oreffectively break the emulsion from a given well, lease, or field.field.

Result from a bottle test also indicate the required ratios of Result from a bottle test also indicate the required ratios of treating compound to emulsion. That is, treating compound to emulsion. That is,

the smallest around of the proper chemical need to the smallest around of the proper chemical need to satisfactorily break the volume of emulsion being satisfactorily break the volume of emulsion being produced.produced.

Application of electric currentApplication of electric current Usually in conjunction with heat & chemicals.Usually in conjunction with heat & chemicals.

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Gun barrel or Wash tankGun barrel or Wash tank

Sometimes an oil-water emulsion is not stable,Sometimes an oil-water emulsion is not stable, Given enough time, the water will settle to the bottom of a Given enough time, the water will settle to the bottom of a

tank and oil will rise to the top.tank and oil will rise to the top. The settling vessel used for this kind of separation method is The settling vessel used for this kind of separation method is

called a gun barrel or wash tank.called a gun barrel or wash tank.

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Stock tanks (storage tanks )Stock tanks (storage tanks )

Once the oil is clean enough to meet pipeline specifications, it Once the oil is clean enough to meet pipeline specifications, it is flowed into storage tanks, sometimes called stock tanks.is flowed into storage tanks, sometimes called stock tanks.

Tank battery-Tank battery-

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Stock tanks (storage tanks )Stock tanks (storage tanks ) Two basic types of stock tanks:Two basic types of stock tanks: bolted steelbolted steel welded steelwelded steel

Bolted steel tanksBolted steel tanks - 500 bbl or larger; assembled on location.- 500 bbl or larger; assembled on location.

Welded steel tanksWelded steel tanks - 90 bbl to several thousand bbls.- 90 bbl to several thousand bbls. Welded in a shop and then transported as a complete unit Welded in a shop and then transported as a complete unit to the site.to the site.

Most tanks are equipped with a bottom drain out let for draininMost tanks are equipped with a bottom drain out let for draining off basic sediment and water (BS&W).g off basic sediment and water (BS&W).

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Vapor Recovery SystemVapor Recovery System when oil is treated under pressure and then goes to a stock tank at when oil is treated under pressure and then goes to a stock tank at

pear atmospheric pressure, some of the liquid hydrocarbons flash, or pear atmospheric pressure, some of the liquid hydrocarbons flash, or convent, to gas.convent, to gas.

-- In past years, flash gas or vapor were vented to the atmosphere.-- In past years, flash gas or vapor were vented to the atmosphere. -- Governmental agencies now insist on vapor recovery in order to -- Governmental agencies now insist on vapor recovery in order to reduce air pollution.reduce air pollution.

A vapor recovery unit consists of A vapor recovery unit consists of * a control pilot mounted on a tank for compressor control, * a control pilot mounted on a tank for compressor control, * a scrubber to keep the liquid hydrocarbons out of the * a scrubber to keep the liquid hydrocarbons out of the compressor,compressor, * a compressor, and* a compressor, and *a control panel.*a control panel.

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Treating oil-field emulsionsTreating oil-field emulsions

oil)in (water Emulsion oil- Water

phase dispersed - oil

phase continuous

dispersion -water

in water) (oilEmulsion Water -Oil

Emulsion

之定義

acid organic soluble-oil

substances resinous

asphalt

exist emulsifieror agent gemulsifyin (2)

agitation sufficient (1)

onlyemulsion an form water toand Oil

瀝青

breaktoeasy

breaktodifficultEmulsion

Loose

Tight