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Chapter 7 Separating and Treating Well Fluids

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Title: Chapter 7 Separating and Treating Well Fluids


1
Chapter 7 Separating and Treating Well Fluids
2
Principles and Operation of Production Separators
  • - Gas, oil and water separation was achieved by
  • the difference in gravity, or weight, of
    each fluid.
  • - Production separators do the same job, except
    they
  • are built to handle a continuous-flow stream
    and
  • have features to improve separation
    efficiency
  • under flow conditions.

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Three general types of separators
  • - Horizontal separator
  • - for high-pressure and medium-pressure
    service
  • - Vertical separator
  • - for low-pressure service (generally)
  • - Spherical separator
  • - more compact and cheaper
  • - limited separation space and liquid surge
    capacity
  • - for low-volume remote platforms

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Separation methods
  • - Stage separation method
  • - Low-temperature separation method

8
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.
9
Low-temperatures separation method
  • It is used to handle the production from
    high-pressure gas wells
  • Well fluids a mixture of gas some light
    liquids
  • Dehydration the removal of water vapor from
    gas

10
  • Low temperature separation method
  • uses the cooling effect of expanding high
    pressure gas

11
Low-temperature separation method
  • For high-pressure gas wells (well fluids
    mixture of gas and some light liquids)
  • - Dehydration to remove water vapor from
    gas

12
Water-removal
  • Water-removal before the oil can be delivered
    to the pipeline
  • Free water some of the water produced with the
    oil will not be mixed with it this is known as
    free water .

13
Water removal
using
  • -Treatment of free-water Free water
    knock out (FWKO)

14
Treatment of oil-water or water-oil emulsion
  • Water and oil are immiscible.
  • These two liquids will form an emulsion only
  • (1) if there is sufficient agitation to
    disperse one liquid as
  • droplets in the other , and
  • (2) if there is an emulsifying agent , or
    emulsifier , present.
  • Emulsifying agents asphalt ?? ??
  • resinous
    substances

  • oil-soluble organic acids.

15
Emulsions
  • Emulsion a mixture in which one liquid, termed
    the
  • dispersed phase, is
    uniformly distributed (usually as
  • minute globules, in another
    liquid, called the
  • continuous phase or the
    dispersion medium (phase))
  • Oil water emulsion
  • the oil is the dispersed phase, and
  • the water (is ) the dispersion medium
    (or continuous phase )
  • Water-oil emulsion
  • the water is the dispersed phase, and
  • the oil the dispersion medium

16
Emulsions -- continue
  • Stable emulsion will not break down into its
    components
  • without some
    form of treating.
  • Tight (difficult to break) or loose (easy to
    break) emulsion
  • Depending on
  • (1) the properties
    of the oil water
  • (2) the percentage
    of each found in the emulsion
  • (3) type and amount
    of emulsifier present .

17
Treatment of oil-water or water-oil emulsion
Treatment of oil-water or water-oil
emulsion (1)Heat (2)Chemicals (3)Electricity (
4)Combination of these (heater- treater)
flow treater or emulsion treated
(5)Gun barrel or wash tank if emulsion is not
stable
18
Application of heat
  • One theory assumes that very small droplets, like
    those found in emulsions, are in constant motion
    even when the emulsion itself is not rest .
  • Application of heat
  • (1) Heat increases the movement are makes the
    droplets strike each other with greater force and
    frequency.
  • (2) Heat also reduces the viscosity the
    resistance to flow of the oil.
  • Heater (???)
  • (1) direct heater
  • (2) Indirect heaterwater bath (fig5.22 P.161)

19
Application of chemicals
  • One theory suggests that chemical should be used
    strictly to neutralize the emulsifying agent.
  • Thus, to break a water-in-oil emulsion,
  • another emulsifying agent to produce
    oil-in-water emulsion
  • should be added.
  • Another theory suggests the chemicals should make
    the film of emulsifying agent around the water
    droplet in a water-in-oil emulsion very rigid.
  • Thus, to break rigid film
  • apply heat or
  • add chemical.

20
Heater-treater
  • Heater-treater also called a flow treater or an
    emulsion treater.
  • Heater-treater (or call flow treater, or emulsion
    treater)
  • apply the effects of
  • Chemicals, heat , settling, and often
    electricity
  • Any or all of the following elements may be
    included in a treater
  • oil-gas separator,
  • free-water knockout,
  • heater,
  • water, wash, filter section,
  • stabilizing section,
  • heat exchanger, and
  • electrostatic field.

21
Treater
  • Treater can be operated at atmospheric pressure,
  • often be operated under low working
    pressure.
  • ? A low-pressure, second-stage separator
    as well as
  • treating unit.
  • When flow-line pressure are low, it
    can be used as a
  • primary separator thus eliminating
    the need for a regular
  • separator. (fig 5.25, P.164)

22
Treating natural gas
  • Field processing of natural gas consist of four
    basic processes
  • the gas must be separated from free liquids such
    as crude oil, hydrocarbon condensate, water , and
    entrained solids,
  • (2) the gas must be processed to remove
    condensable and recoverable H.C. vapors
  • (3) the gas must be treated to remove condensable
    water vapor, which might cause hydrate formation
  • (4) the gas must be treated to remove other
    undesirable components, such as hydrogen sulfide
    or carbon dioxide.

23
Treating Natural Gas
  • The primary treatments for natural gas involve
  • (1)prevention of hydrate formation
  • by applying heat and/or
  • adding hydrate inhibitor

  • ammonia

  • brine

  • glycol (???)

  • methanol (??)
  • (2)dehydration,
  • absorption (??) Liquid ???
  • adsorption (??) Solid ???
  • (3)The removal of undesirable components
    (H2S?CO2)
  • Alkanolamine process
  • Iron-sponge process
  • Glycol/amine process
  • Sulfinol process
  • Molecular-sieve removal

24
Prevention of hydrate formation
  • Water is always necessary for hydrate formation.
  • water always accelerates corrosion.

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Phase diagram for a pure single component
27
Dehydration means removal of water
  • Water vapors (as well as certain other vapor) are
    removes from gas by either
  • (1) the absorption process, or
  • (2) the adsorption process
  • Absorption process --
  • Water vapor may be removed from natural gas
    by bubbling the gas counter currently through
    certain liquids that have a special attraction or
    affinity for water.

28
Dehydration means removal of water
  • Adsorption --
  • Some solids also have an affinity for water,
    and when gas flows through a bed of such granular
    solids, the water is retained on the surface of
    the particles.
  • Desiccant --
  • The liquid or the solids that has the
    affinity for water in either process is called a
    desiccant.
  • Dehydration equipment
  • -- The liquid-desiccant dehydrator
  • -- The solid-desiccant dehydrator

29
Removal of undesirable components
  • Alkanolamine process
  • -- It is a continuous-operation liquid
    process that uses absorption for the acid-gas
    removal, with subsequent heat addition to string
    the acid-gas component from absorbent solution.
  • Other processes that are used to removal H2S
    CO2 are
  • The Iron-sponge process,
  • The glycol/amine process,
  • The sulfinol process, and
  • The molecular-sieve removal.

30
Typical Natural Gas Components
31
  • Casinghead gas
  • -- gas produced with oil from an oil well.
  • Residue gas
  • -- any gas suitable for as commercial
    natural gas that comes
  • from a processing plant.
  • Sweet gas
  • --the content of hydrogen sulfide, other
    sulfur compounds,
  • and carbon dioxide is low enough that
    gas may be sold
  • commercially without further effort to
    remove these
  • compounds.
  • Sour gas
  • --the opposite of sweet gas.

32
Types of Natural Gas Liquids
  • Commercial propane (??)
  • -- propane and/or propylene (at least
    95)
  • -- vapor pressure lt 215 psig at 100 0F
  • Commercial Butane (??)
  • -- butanes and/or Butane (at least 95)
  • -- vapor pressure lt 70 psig at 100 0F
  • -- At least 95 must evaporate at 34 0F
    or lower in a
  • standard test.
  • Liquefied Petroleum Gas (LPG)
  • -- A mixture of commercial propane and
    commercial butane.
  • -- maximum vapor pressure lt 215 psig at
    100 0F
  • At least 95 must evaporate at 34
    0F or lower in a
  • standard test.

33
Types of Natural Gas Liquids
  • Natural Gasoline
  • --This petroleum product is extracted
    from natural gas
  • --specifications
  • Vapor pressure10-34psi
  • Percentage evaporated at 140 F 24-85
  • Percentage evaporated at 275 F not less then
    90

34
  • Vapor pressure, usually referred to as Reid vapor
    pressure (RVP), used to designate grades.
  • Motor fuels 5-8psi RVP
  • Very light oils (60-70AIP) 12psi RVP
  • Natural gasoline product 14-26 psi RVP

35
The Storage System
36
The Storage System
  • Stock tanks (or storage tanks)
  • -Tank battery
  • -separation equipment
  • treating equipment
    tank battery
  • storage facilities
  • -stock tanks Bolted steel tank 500 bbls or
    larger assembled on location
  • Welded steel tank 90
    bbl to several thousand bbls

    welded in a shop and then transported
    as a
    complete unit to the site
  • -Vapor Recovery System
  • -LACT (Lease automatic custody transfer) unit
  • Oil sampling thief-sampling method
  • bottle-sampling
    method
  • Gas sampling

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

44
The well stream
  • The well stream -- high-velocity, turbulent,
  • constantly expanding mixture of gases and
    hydrocarbon liquids,
  • intimately mixed with water vapor, free water
    solids and
  • other containment.

45
The bottle test
  • -- It is used to help determine which chemical
    can most
  • effectively break the emulsion from a
    given well, lease, or
  • field.
  • Result from a bottle test also indicate the
    required ratios of treating compound to emulsion.
    That is,
  • the smallest around of the proper
    chemical need to
  • satisfactorily break the volume of
    emulsion being
  • produced.
  • Application of electric current
  • Usually in conjunction with heat
    chemicals.

46
Gun barrel or Wash tank
  • Sometimes an oil-water emulsion is not stable,
  • Given enough time, the water will settle to the
    bottom of a tank and oil will rise to the top.
  • The settling vessel used for this kind of
    separation method is called a gun barrel or wash
    tank.

47
Stock tanks (storage tanks )
  • Once the oil is clean enough to meet pipeline
    specifications, it is flowed into storage tanks,
    sometimes called stock tanks.
  • Tank battery-

48
Stock tanks (storage tanks )
  • Two basic types of stock tanks
  • bolted steel
  • welded steel
  • Bolted steel tanks
  • - 500 bbl or larger assembled on location.
  • Welded steel tanks
  • - 90 bbl to several thousand bbls.
  • Welded in a shop and then transported as
    a complete unit
  • to the site.
  • Most tanks are equipped with a bottom drain out
    let for draining off basic sediment and water
    (BSW).

49
Vapor Recovery System
  • when oil is treated under pressure and then goes
    to a stock tank at pear atmospheric pressure,
    some of the liquid hydrocarbons flash, or
    convent, to gas.
  • -- In past years, flash gas or vapor were
    vented to the atmosphere.
  • -- Governmental agencies now insist on vapor
    recovery in order to
  • reduce air pollution.
  • A vapor recovery unit consists of
  • a control pilot mounted on a tank for
    compressor control,
  • a scrubber to keep the liquid hydrocarbons
    out of the
  • compressor,
  • a compressor, and
  • a control panel.

50
Treating oil-field emulsions
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