Title: Chapter 7 Separating and Treating Well Fluids
1Chapter 7 Separating and Treating Well Fluids
2Principles 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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4Three 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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7Separation methods
- - Stage separation method
- - Low-temperature separation method
8Stage separation method (two stage separation)
Any number of separators may be used in stage
separation as long as stage operates at
successively lower pressures.
9Low-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
11Low-temperature separation method
- For high-pressure gas wells (well fluids
mixture of gas and some light liquids) - - Dehydration to remove water vapor from
gas
12Water-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 .
13Water removal
using
- -Treatment of free-water Free water
knock out (FWKO)
14Treatment 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.
15Emulsions
- 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
16Emulsions -- 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 .
17Treatment 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
18Application 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)
19Application 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.
20Heater-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.
21Treater
- 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)
22Treating 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.
23Treating 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
24Prevention of hydrate formation
- Water is always necessary for hydrate formation.
- water always accelerates corrosion.
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26Phase diagram for a pure single component
27Dehydration 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.
28Dehydration 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
29Removal 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.
30Typical 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.
32Types 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.
33Types 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
35The Storage System
36The 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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43Treatment 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 )
44The 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.
45The 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.
46Gun 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.
47Stock 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-
48Stock 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).
49Vapor 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.
50Treating oil-field emulsions