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Chapter 8

Chapter 8. Separating and Treating Well Fluids. Chapter 8 Separating and Treating Well Fluids. Principles and Operation of Production Separators. ─ Gas, oil and water separation was achieved by the difference in gravity, or weight, of each fluid.

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Chapter 8

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  1. Chapter 8 Separating and Treating Well Fluids

  2. Chapter 8 Separating and Treating Well Fluids

  3. Principles and Operation of Production Separators ─ Gas, oil and water separation was achieved by the difference in gravity, or weight, of each fluid. ─ Production separator do the same job, except they are built to handle a continuous-flow stream and have features to improve separation efficiency under flow conditions.

  4. 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

  5. Separation methods ─ Stage separation method ─ Low-temperature separation method

  6. 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.

  7. 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

  8. 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

  9. 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 瀝青 柏油 resinous substances oil-soluble organic acids.

  10. Stable emulsion – will not break down into its components without some form of treating. • Emulsion – tight (difficult to break) or loose (easy to break) 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 .

  11. Treating oil-field emulsions

  12. Water removal using ─Treatment of free-water Free water knock out (FWKO) ─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

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

  14. 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.

  15. 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.

  16. Treater • Treater can be operator 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)

  17. 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.

  18. Treating Natural Gas The primary treatments for natural gas involve （1）prevention of hydrate formation Heat Hydrate inhibitor: ammonia brine glycol (乙二醇) methanol (甲醇) （2）dehydration, absorption (吸收) – Liquid 乾燥劑 adsorption (吸附) – Solid 乾燥劑 （3）The removal of undesirable components (H2O、CO) Alkanolamine process Iron-sponge process Glycol/amine process Sulfinol process Molecular-sieve removal

  19. 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.

  20. Typical Natural Gas Components

  21. 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.

  22. Types of Natural Gas Liquids • Commercial propane (丙烷) -- propane and/or propylene (at least 95%) -- vapor pressure < 215 psig at 100 0F • Commercial Butane (丁烷) -- butanes and/or Butane (at least 95%) -- vapor pressure < 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 < 215 psig at 100 0F At least 95% must evaporate at 34 0F or lower in a standard test.

  23. Types of Natural Gas Liquids • Natural Gasoline --This petroleum product is extracted from natural gas --specifications: • Vapor pressure:10-34psi • Percentage evaporated at 140 F: 24-85% • Percentage evaporated at 275 F: not less the 90%

  24. The Storage System

  25. 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 Botlle – sampling method Gas sampling

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

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