Gas Processing and Treatment-Lecturer 7

 

GAS PROCESSING AND TREA TREATMENT TMENT •

 This chapter will look at field treatment and processing operations of natural gas and oth ther er

asso as soci ciat ate ed

prod pr oduc ucts ts..

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ope op era rattio ions ns

inc in clu lude de

,de dehy hyd dra rattio ion, n,

acid ac id

gass ga

removal,(H removal,( H2S ,CO2) and the separator and fractionation of liquid HC(NLG). •

 Sweetening of natural gas almost always precedes dehydration and other gas plant processes carried out for the separation of NGL.

 

GAS PROCESSING AND TREA TREATMENT TMENT •

 Dehydration on the other hand is usually required before the gas can be sold for pipeline marketing and it is necessary step is the requirement of NGL from natural gas.

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  For convince a system involving field treatment of a gas project could be divided

Into 2 main stages.

 

GAS PROCESSING AND TREA TREATMENT TMENT H2S H2O

Natural gas

Removal of acidic gases and impurities STAGE 1

C2

Fractionati on of NGL

Recovery of NGL

STAGE 2

Figure 1: Operations involved in processing and treatment of natural gas

C3 C4+

 

GAS PROCESSING AND TREA TREATMENT TMENT •

  Natural gas field processing and removal of various components is complex and tends to involve complex and expensive processes.

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  Natural gas leaving the field can have some components that need to be removed before the gas is sold to pipelin pipeline e transmission company. company.

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 All the H2S ,CO2,water vapour and nitrogen should be removed from the gas before export.

 

TREATMENT TMENT GAS PROCESSING AND TREA •

  Gas compression is required in all these processes.

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 A sour gas leaving GOSP might require an amine unit to remove the acidic gasses, glycol unit to dydrate it and a compressor to compress it before its sold off.

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  Its always reasonable to recover NGL in gas in appreciable quantities;   This includes normally hydro carbons known as C3+(ethane,propane,butane,isobutane C3+(ethane,propane,butane,isobutane and pentane)

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  In some cases ethane (C2) can be removed and sold sold as a petro chemical feed stock

 

GAS PROCESSING AND TREA TREATMENT TMENT •

  NGL recove recovery ry is the the first first opera operation tion in stage stage 2.

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  To recover and separate NGL from a bulk of gas stream requires a change in phase meaning a new phase has to be developed for separation to take place by using one of the following.

1.An 1. An en ener ergy gy se sepa para rati ting ng ag agen ent: t: li like ke re refr frig iger erat atio ion n fo forr pa part rtia iall or to tota tall li liqu quef efac acti tion on an and d fractionation 2. Mass separating agent: examples are adsorption and absorption(using selective hydrogen carbons)

 

TREATMENT TMENT GAS PROCESSING AND TREA •

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In designing a system for field gas processing the following parameters parameters should be placed into consideration.

  Estimate the gas reserve(both associated associ ated and free gas)

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  The gas flow rate and composition of the feed gas.

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  Market demand for the products both local and export.

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  Geographical location locati on and method of shipping the finished products.

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  Environmental factors.

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  Risks involved in implementing the project and its economics.

 

GAS PROCESSING AND TREA TREATMENT TMENT •

Natural gas refers to the gas obtained from underground reservoirs either a free gas or associated with crude oil.

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  It generally contains methane(CH4) with decreasing amounts of other hydro carbons.

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 Impurities such as H2S ,CO2,N2 are found within the gas.

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 It also comes saturated with water vapour.

 

Typical Natural Gas Components

 

TREATMENT TMENT GAS PROCESSING AND TREA •

  The principle principle market for natural gas is achiev achieved ed via trans transmissio mission n lines which distribute it to different consuming centers such as com comme merc rcia ial, l, in indu dustr stria iall an and d do dome mesti stic. c.

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  Fi Fiel eld d pr proc oces essi sing ng op oper erat atio ions ns ar are e th thus us en enfo forc rced ed to tr trea eatt th the e na natu tura rall ga gass to me meet et th the e specification and requirements set by the transmission companies.

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  The main objective is to obtain natural gas as the main product product free from impurities.

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 In addition it should be recognized that field processing units are economically justified by NGL recovery above that obtained by conventional separation.

 

Processing Natural Gas

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 Natural gas, as it is used by consumers, is much different from the natural gas that is brought from underground up to the wellhead.

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  Although the processing processing of natural gas is in many respects less less complicated than the processing and refining of crude oil, it is equally as necessary before its use by end users.

 

Processing Natural Gas •

 The natural gas used by consumers is composed almost entirely of methane. However, natural gas found at the wellhead, although still composed primarily of methane, is not yet pure.

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  Raw natural gas comes from three types of wells: oil wells: oil wells, gas wells, and condensate wells.

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  Natural gas gas that comes comes from oil wells wells is typically termed termed ‘associated gas’ gas’.

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  This gas can exist separate from oil in the formation formation (free gas), or dissolved in the crude oil oil (dissolved gas).

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  Natu Natural ral gas from gas and condensate condensate wells, wells, in whi which ch there is little or no crud crude e oil, is ter termed med ‘non associated gas’ gas’..

 

Processing Natural Gas •

 Gas wells typically produce raw natural gas by itself, while condensate wells produce free natural gas along with a semi-liquid hydrocarbon condensate.

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  Whatever the source of the natural gas, once separated from crude oil (if present) present) it commonly exists in mixtures with other hydrocarbons; principally et etha hane ne,, pr prop opan ane, e,

buta bu tane ne,, an and d pe pent ntan anes es.. •

  In addition, raw natural gas contains water vapor, hydrogen sulfide (H2S), carbon dioxide, helium, nitrogen, and other compounds.

 

Processing Natural Gas •

  Natural gas processing consists of separating all of the various hydrocarbons and fluids from the pure natural gas, to produce what is known as ‘pipeline quality’ quality’ dry natural gas.

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  Major transportation pipelines usually impose restrictions on the make-up of the natural gas that is allowed into the pipeline.

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  That means that before the the natural gas can be transported it must be purified. purified.   While the ethane, propane, butane, and pentanes  must be removed from natural

gas, this does not mean that they are all was waste te pro produc ducts ts .  

Processing Natural Gas

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 In fact, associated hydrocarbons, known as ‘natural ‘natural   gas liquids’ liquids’ (NGLs)  (NGLs) can be very valuable by-products of natural gas processing.

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  NGLs include ethane, propane, butane, iso-butane, and natural gasoline.   These NGLs are sold separately and have a variety of different uses; including enhancing oil recovery in oil wells, providing raw materials for oil refineries or petrochemical plants, and as sources of energy

 

Processing Natural Gas •

 While some of the needed processing can be accomplished at or near the wellhead (field processing), the complete processing of natural gas takes place at a processing plant, usually located in a natural gas producing region.

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  The ex extr tract acted ed na natu tural ral ga gass is tr tran ansp spor orte ted d to th thes ese e pr proc oces essi sing ng pla plant ntss th thro roug ugh h a network of gathering pipelines, which are small-diameter small-diameter,, low l ow pressure pipes.

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  A comple lex x gathering system can consist of thousan and ds of mile less of pipes, interconnecting the processing processing plant to upwards of 100 wells in the area.

 

Processing Natural Gas •

 The actual practice of processing natural gas to pipeline dry gas quality levels can be quite com quite comple plex, x, but usu usually ally invo involve lvess four main processes   to remove the various impurities:

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  Oil and Condensate Removal Removal

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 Water Removal

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 Separation of Natural Gas Liquids

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  Sulfur and Carbon Dioxide Removal

 

Processing Natural Gas •

 In addit addition ion to the four processes above, heaters and scrubbers scrubbers are installed, usually at or near the wellhead.

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  The scrubbers serve primarily to remove sand and other large-particle impurities. The heaters ensure that the temperature of the gas does not drop too low.

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  With natural gas that contains even low quantities of water, natural gas hydrates have a tendency to form when temperatures drop.

 

Processing Natural Gas

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  The These se hyd hydrat rates es are sol solid id or sem semi-s i-soli olid d com compou pounds nds,, res resemb embling ling ice like cry crysta stals. ls. Shou Sh ould ld th thes ese e hy hydr drat ates es ac accu cumu mula late te,, th they ey ca can n im impe pede de th the e pa pass ssag age e of na natu tura rall ga gass through valves and gathering systems.

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  To reduce the occurrence of hydrates, small natural gas-fired heating units are typically installed along the gathering pipe wherever it is likely that hydrates may form.

 

Oil and Condensate Removal •

  In order to process and transport associated dissolved natural gas, it must be separated from the oil in which it is dissolved.

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  This separation of natural gas from oil is most often done using equipment installed at or near the wellhead.

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  The actual process used to separate oil from natural gas, as well as the equipment that is used, can vary widely.   Although dry pipeline quality natural natural gas is virtually identical across different geographic areas, raw natural gas from different regions may have different diffe rent compositions and separation

requirements.  

Oil and Condensate Removal •

  In many instances, instances, natural gas is dissol dissolved ved in oil under undergrou ground nd primarily due to the pressure that the formation is under.

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 When this natural gas and oil is produced, it is possible that it will separate on its own, simply due to decreased pressure; much like opening a can of soda pop allows the release of dissolved carbon dioxide.

 

Oil and Condensate Removal •

 In these cases, separation of oil and gas is relatively easy, and the two hydrocarbons are sent separate ways for further processing.

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  The most basic basic type of separator separator is known as a conve convention ntional al separ separator ator..

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  It consists of a simple closed closed tank, where the force of gravity serves serves to separate the heavier liquids like oil, and the lighter gases, like natural gas.

 

Oil and Condensate Removal •

  In certain instances, however, however, specialized equipment is necessary to separate oil and natural gas.

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  An example of this type of equipment equipment is the Low-T Low-Temperature emperature Separator (L (LTX). TX).

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  This is most often used used for wells producing high pressure pressure gas along with light crude oil or condensate.

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Oil and Condensate Removal •

 These separators use pressure differentials to cool the wet natural gas and separate the oil and condensate.

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  Wet gas enters the separator separa tor,, being cooled slightly sli ghtly by a heat exchanger. exchanger.   The gas then travels through a high pressure liquid ‘knockout’,   which serves to remove any liquids into a low-temperature separator.

 

Oil and Condensate Removal •

 The gas then flows into this low-temperature separator through a choke mechanism, which expands the gas as it enters the separator separator..

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  This rapid expansion of the gas allows allows for the lowering of the temperature in the separator. separator.   After liquid removal, the dry gas then travels back through the heat exchanger and is warmed by the incoming wet gas.

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  By varying the pressure of the gas in various sections of the separator, separator, it is possible to vary the temperature, which causes the oil and some water to be condensed out of the wet gas stream. This stream.  This basic pressure-temperature relationship can work in reverse as well, to extract

gas from a liquid oil stream.  

Water Removal

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  In addition to separating oil and some condensate from the wet gas stream, it is necessary to remove most remove  most of the associated water.

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  Most of the liquid, free water associated associated with extracted natural natural gas is removed by simple separation methods at or near the wellhead.

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  Howev However er,, the remov removal al of the water vapor that exists in solution in natural gas requires a more complex treatment.

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Water Removal

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 This treatment consists of ‘dehydrating’ of  ‘dehydrating’ the  the natural gas, which usually involves one of two processes: either processes: either absorption, or adsorption. adsorption.

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 Absorpt  Ab sorption ion occu occurs: rs:   when when th the e wa wate terr vap vapor or is tak taken en ou outt by a de dehy hydr drati ating ng ag agen ent. t. Adsorption occurs: when occurs: when the water vapor is condensed and collected on the surface.

 

Glycol Dehydration •

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  An example of absorption dehydration dehydration is known as Glycol Dehydration. Dehydration.   In this process, a liquid desiccant desiccant dehydrator dehydrator serves to absorb water water vapor from the gas gas stream.   Glycol, the principal agent in this process, process , has a chemical affinity for water. water.   This means that, when in contact with a stream of natural gas that contains water, water, glycol will serve to ‘steal’ the water out of the gas stream. ‘steal’ the  Essentially, glycol dehydration involves using a glycol solution, usually either diethylene glycol (DEG) or tri ethylene glycol (TEG), which is brought into contact with the wet gas stream in what is called the ‘contactor ‘contactor’’.

 

Glycol Dehydration •

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  The glycol solution will absorb water from the wet wet gas.   Once absorbed, absorbed, the glycol particles particles become heavier and sink to the botto bottom m of the contactor where they are removed.

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  Th The e na natu tura rall ga gas, s, ha havi ving ng be been en st stri ripp pped ed of mo most st of it itss wa wate terr co cont nten ent, t, is th then en transported out of the dehydrator.

 

Glycol Dehydration •

 The glycol solution, bearing all of the water stripped from the natural gas, is put through a specialized boiler designed to vaporize only the water out of the solution. While water has a boiling point of 212 degrees Fahrenheit, glycol does not boil until 400 degrees Fahrenheit.

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  This boiling point differential makes it relatively easy to remove water from the glycol solution, allowing it be reused in the dehydration process.

 

adsorption -Solid-Desiccant -Solid-Desiccant Dehydration •

 Solid-desiccant dehydration is the primary form of dehydrating natural gas using adsorption, and an d us usua uall lly y co cons nsis ists ts of tw two o or mo more re ad adso sorp rpti tion on to towe wers rs,, wh whic ich h are fil fille led d wi with th a so soli lid d desiccant.

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  Typical desiccants include activated include activated alumina or a granular silica gel material. material .   Wet natural gas gas is passed through these towers, from top top to bottom.  As the wet gas passes around the particles of desiccant material, water is retained on the surface of these desiccant particles.

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  Passing through the entire desiccant bed, almost all of the water is adsorbed onto the

desiccant material, leaving the dry gas to exit the bottom of the tower. tower.  

Solid-Desiccant Dehydration •

 Solid-desiccant dehydrators are typically more effective than glycol dehydrators, and are usually installed as a type of straddle system along natural gas pipelines.

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 These types of dehydration systems are best suited for large volumes of gas under very high pressure, and are thus usually located on a pipeline downstream of a compressor station.

 

Solid-Desiccant Dehydration •

 Two or more towers are required due to the fact that after a certain period of use, the desiccant in a particular tower becomes saturated with water water..

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  To ‘regenerate’ ‘regenerate’ the  the desiccant, a high-temperature heater is used to heat gas to a very high temperature. Passing this heated gas through a saturated desiccant bed vaporizes the water in the desiccant tower, leaving it dry and allowing for further

natural gas dehydration.  

Absorption Towers and Gas Pro Processin cessing g Plant with Absorp Absorption tion Towers

 Adso  Ad so rp ti on Tow ers

Gas Ga s Processing Plant with Absorp tion Towers

 

Separation of Natural Gas Liquids •

 Natural gas coming directly from a well contains many natural gas liquids that are commonly removed.

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  In mo most st in inst stan ance ces, s, na natu tura rall ga gass liq liqui uids ds (NG (NGLs Ls)) ha have ve a hi high gher er va valu lue e as se separ parat ate e products, and it is thus economical to remove them from the gas stream.

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  The removal of natural gas liquids usually takes place in a relatively centralized processing plant, and uses techniques similar to those used to dehydrate natural

gas.

 

Separation of Natural Gas Liquids •

 There are two basic steps to the treatment of natural gas liquids in the natural gas stream.

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  First, the liquids must be be extracted from the natural gas.

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  Second, these natural gas liquids must be separated, separated, down to their base components

 

NGL Extraction

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  There are two principle techniques for removing NGLs from the natural gas stream

the abs absorp orptio tion n met method hod and the cr cryo yoge geni nic c ex expa pand nder er pr proc oces esss. According to the Gas the  Gas Processors Association, Association, these two processes account for around 90 percent of total natural gas liquids production.

 

Absorption Method The Absorption •

  The absorption method of NGL extraction is very similar to using absorption for dehydration.

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  The main difference is that, in NGL absorption, absorption, an absorbing oil is used as opposed opposed to glycol.

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  This absorbing oil has an ‘affinity’ ‘affinity’ for  for NGLs in much the same manner as glycol has an affinity for water.

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  Before the oil has picked up any NGLs, it is termed ‘lean lean’’ absorption oil.

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 As the natural gas is passed through an absorption tower, it is brought into contact with the absorption oil which soaks up a high proportion of the NGLs.

 

Absorption Method The Absorption •

  The ‘rich’ ‘rich’ absorption  absorption oil, now containing NGLs, exits the absorption tower through the bottom.

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  It is now a mixture of absorption absorption oil, propane, butanes, pentanes, and other heavier hydrocarbons.

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  The rich oil is fed into lean oil stills stills,, where the mixture is heated to a temperature temperature above the boiling point of the NGLs, but below but below that of the oil.

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 This process allows for the recovery of around 75 percent of butanes, and 85 –   90

percent of pentanes and heavier molecules from the natural gas stream  

Absorption Method The Absorption •

 The basic absorption process above can be modified to improve its effectiveness, or to target the extraction of specific NGLs.

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  In the refrigerated oil absorption method, where the lean oil is cooled through refr re frig iger erat atio ion, n, pr prop opan ane e re reco cove very ry ca can n be up upwar wards ds of 90 pe perc rcen ent, t, an and d ar arou ound nd 40 percent of ethane can be extracted from the natural gas stream.

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  Extraction of the other, other, heavier NGLs NG Ls can be close to 100 percent using this process.

 

The Cryogenic Expansion Process •

  Cryogenic processes are also used to extract NGLs from natural gas.

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 While absorption methods can extract almost all of the heavier NGLs, the lighter hydrocarbons, such as ethane, are often more difficult to recover from the natural gas stream.

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  In certain instances, it is economic to simply leave the lighter NGLs in the natural gas stream.

 

The Cryogenic Expansion Process •

  Ho Howe weve verr, if it is ec econ onom omic ic to ex extr trac actt et etha hane ne an and d ot othe herr li ligh ghte terr hy hydro droca carb rbon ons, s,

cryoge cry ogenic nic pro proces cesses ses are required for high recovery rates. •

  Ess Essent ential ially ly,, cry cryoge ogenic nic pro proces cesses ses con consis sistt of dro droppi pping ng the tem temper peratu ature re of the gas stream to around -120 degrees Fahrenheit.

 

The Cryogenic Expansion Process •

 There are a number of diffe different rent ways of chillin chilling g the gas to these temperature temperatures, s, but one of the most effective is known as the tu turb rbo o ex expa pand nder er pr proc oces esss.

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  In this process, external refrigerants are used to cool the natural gas stream.   Then, an expansion turbine is used to rapidly expand the chilled gases, which causes the temperature to drop significantly.

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 This rapid temperature drop condenses ethane and other hydrocarbons in the gas stream, while maintaining methane in gaseous form.

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The Cryogenic Expansion Process •

  This process allows for the recovery of about 90 to 95 percent of the ethane originally origi nally in the gas stream.

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  In addition, the expansion turbine turbine is able to convert some of the energy released when the natural gas stream is expanded into recompressing the gaseous methane effluent, thus saving energy costs associated with extracting ethane.

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 The extraction of NGLs from the natural gas stream produces both cleaner cleaner,, purer natural

gas, as well as the valuable hydrocarbons that are the NGLs themselves.  

Natural al Gas Liquid Fractionation Natur •

 Once NGLs have been removed from the natural gas stream, they must be broken down into their base components to be useful.

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 That is, the mixed stream of different NGLs must be separated out. The process used to accomplish this task is called   fractionation. fractionation. Fractionation works based on the different boiling points of the different hydrocarbons in the NGL stream.

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  Essentially Essentially,, fractionation occurs in i n stages consisting of the boiling boil ing off of hydrocarbons one by one.

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Natural Gas Liquid Fractionation •

  The name of a particular fractionator gives an idea as to its purpose, as it is conventionally named for the hydrocarbon that is boiled off.

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  The entire fractionation process is broken down into steps, starting with the removal of the lighter NGLs from the stream.

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  The particular fractionators fractionators are used in the following order:

 

Natural Gas Liquid Fractionation •

Deethanizer – this step separates the ethane from the NGL stream.

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Depropanizer – the next step separates the propane.

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Debutanizer – this step boils off the butanes, leaving the pentanes and heavier hydrocarbons in the NGL stream.

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Butane Splitter or Deisobutaniz Deisobutanizer er – this step separates the iso and normal butanes.   By proceeding from the lightest hydrocarbons to the heaviest, it is possible to separate the

different NGLs reasonably easily.  

Sulfur and Carbon Dioxide Removal •

 In addition to water, oil, and NGL removal, one of the most important parts of gas processing involves the removal of sulfur and carbon dioxide.

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  Na Natu tural ral ga gass fr from om so some me we wells lls co cont ntain ainss si sign gnif ific ican antt am amou ount ntss of su sulf lfur ur an and d ca carb rbon on dioxide.

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  This natural gas, because of the rotten smell provided by its sulfur content, is commonly called ‘sour gas’.

 

Sulfur and Carbon Dioxide Removal

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 Sour gas is undesirable because the sulfur compounds it contains can be extremely harmful, even lethal, to breathe.

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  Sour gas can can also be extremely corrosive. corrosive.  In addition, the sulfur that exists in the natural gas stream can be extracted and marketed on its own.

 

Sulfur and Carbon Dioxide Removal •

  Sulfur exists in natural gas as hydrogen hydrogen sulfide (H2S), and the gas is usually considered sour if the hydrogen sulfide content exceeds 5.7 milligrams of H 2S per cubic meter of natural gas.

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  The process for removing hydrogen sulfide from sour gas is commonly referred referred to as ‘sweetening’ the gas.

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  The primary process for sweetening sour natural gas is quite similar to the processes

of glycol dehydration and NGL absorption.  

Sulfur and Carbon Dioxide Removal . In this case, however, amine however,  amine solutions are solutions are used to remove the hydrogen sulfide. This process is known simply as the ‘am ‘amine ine pro proces cess’, s’, or  or alternatively as the Girdler process, and is used in 95 percent of U.S gas sweetening operations The sour gas is run through a tower, which contains the amine solution. This solution has an affinity for sulfur, and absorbs it much like glycol absorbing water.

 

Sulfur and Carbon Dioxide Removal There are two are  two principle amine solutions used, used , mono ethanolamine (MEA) and di ethanolamine (DEA). Either of these compounds, in liquid form, will absorb sulfur compounds from natural gas as it passes through. The effluent gas is virtually free of sulfur compounds, and thus loses its sour gas status. Like the process for NGL extraction and glycol dehydration, the amine solution used can be regenerated (that is, the absorbed sulfur is removed), allowing it to be reused to treat more

sour gas.  

Sulfur and Carbon Dioxide Removal •

 Although most sour gas sweetening involves the amine absorption process, it is also possible to use so soli lid d de desi sicc ccan ants ts like iron sponges to remove the sulfide and carbon dioxide.

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  Sulfur can be sold and used if reduced to its elemental form.

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 Elemental sulfur is a bright yellow powder like material, and can often be seen in

large piles near gas treatment plants, as is shown.  

Sulfur and Carbon Dioxide Removal

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  In or orde derr to re reco cove verr el elem emen enta tall su sulf lfur ur fr from om th the e ga gass pr proc oces essin sing g pl plan ant, t, th the e su sulf lfur ur containing discharge from a gas sweetening process must be further treated.

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  The process used to recover sulfur is known as the the Cla Claus us pr proc oces esss, and involves using thermal and catalytic reactions to extract the elemental sulfur from the hydrogen sulfide solution.

 

Sulfur and Carbon Dioxide Removal •

 In all, the Claus process is usually able to recover 97 percent of the sulfur that has been removed from the natural gas stream.

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  Since it is such a polluting and harmful substance, substance, further filtering, incineration, and ‘tai ‘t aill ga gas’ s’ clean  clean up efforts ensure that well over 98 percent of the sulfur is recovered.

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  Gas processing is an instrumental piece of the natural natural gas value chain.

 

Sulfur and Carbon Dioxide Removal •

 It is instrumental in ensuring that the natural gas intended for use is as clean and pure as possible, making it the clean burning and environmentally sound energy choice.

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  Once the natural gas has been been fully processed, and is ready to to be consumed, it must be tr tran ansp spor orte ted d fr from om th thos ose e ar area eass th that at pro produ duce ce na natu tura rall ga gas, s, to th thos ose e ar area eass th that at

require it.  

Gas Treat reatment ment •

 When the gas is exported, many gas trains include additional equipment for further gas processing, to remove unwanted components such as hydrogen sulfide and carbon dioxide.

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 These gases are called ac aciids an and d sw swee eete ten ning /a /aci cid d re remo mov val is the process of taking them out.

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  Natural gas sweetening methods include absorption absorption processes, cryogenic processes;

adsorption processes (PSA, TSA and iron sponge) and membranes.  

Gas Treat reatment ment •

 Gas treatment could also include calibration. If the delivery specification is for a specific calorific value (BTU per scf or) gas with higher values can be adjusted by adding an inert gas, such as nitrogen. This is often done at a common point such as a pipeline gathering system or a pipeline onshore terminal.

 

Oil and Gas Storage, Metering and Export •

  The final stage before the oil and gas leaves the platform consists of storage, pumps and pipeline terminal equipment. •

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Fiscal Metering

  Partners, authorities and customers all calculate invoices, taxes and payments based

on the actual product shipped out. •

 Often custody transfer also takes place at this point, means a transfer of responsibility or

title from the producer to a customer, customer, shuttle tanker operator or pipeline operator.

 

Oil and Gas Storage, Metering and Export •

  Gas metering is less accurate than liquid, typically ±1.0% of mass.

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  There is usually not a prover loop, instead the instruments and orifice plates are calibrated in separate equipment.

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  LNG is often metered with mass flow meters that can operate at the required low temperature.

 

Storage •

  On most production sites, the oil oil and gas is piped directly to a refinery or tanker terminal. Gas is difficult to store locally locally,, but occasionally underground mines, caverns or salt deposits can be used to store gas.

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  On platforms without pipeline, oil is stored in onboard storage tanks to be transported by shuttle tanker.

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  The oil is stored in storage cells around the shafts on concrete platforms, and in tanks on floating platforms.  

Storage •

 On some floaters, a separate storage tanker is used. In both cases ballast handling is important to balance the buoyancy when the oil volume varies.

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  For onshore fixed roof tanks are used used for crude, floating roof for condensate. condensate.

 

STORAGE •

  Special tank gauging systems such as Level radars, Pressure or Float are used to measure the level in storage tanks, cells and caverns.

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 The level measurement is converted to volume via tank strapping tables (dependent on tank geometry) and compensated for temperature to provide standard volume. Float gauges can also calculate density, density, and so mass can be provided.

 

STORAGE •

 Accurate records of volumes and history is kept to document what is received and dispatched. For installations that serve multiple production sites, different qualities and product blending must also be handled.

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  Another planning task is forecasting for future received and delivered product to make sure that the required amount of sold product is available and that sufficient

capacity is reserved for future received  

STORAGE TANK  •

a. Bolte Bolted-ste d-steel el tank b. Welde Welded-steel d-steel tank c. Flat Flat-si -sided ded tan tank k d. FieldField-welde welded d tank e. Fix Fixed ed ro roof of f. Flo Floati ating ng roo roof  f  g. Cone Cone-bott -bottom om tank

TYPES of storage tanks

h. Pi Pipe pe Stora Storage ge  

BOLTED STEEL TANK  •

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  Designed & furnished as segmental elements assembled on location – Can be vertical, cylindrical, aboveground, closed and open-top steel tanks

– Fabricated from 12 or 10 gauge steel – API nominal capacity: 100 – 10,000 bbl

– Atmosphe  Atmospheric ric internal pressure –  

Advantages  Easy

transportation

 Easy

erected

 Easy

part by part replacement (corroded etc)

 Easy

to a section to be removed

 Easy

to installed a new connection



Available Av ailable with painted, galvanized, special coating

 

Welded-steel tank •

 Shop-fabricated welded

•

 vertical & cylindrical, Fabricated steel

3/16 inch or heavier, heavier, API-12F Spec : vertical shop-welded tanks • API nominal capacity: 90 -500 bbls • Pro Provide vide immediate storage

 

Flat-sided tank: • Shape: rectangular • Good for limited space operation

: offshore operation • Atmospheric pressure storage

• Advantages: – Easy fabricated – Less space  

Field-welded tank Provide large storage capacity @ single unit • API Spec 12D size size range: 500 – 10,000 bbl (nominal capacity) • API Spec. 650 size range : > 10,000 bbl -> more than 150,000 bbl • Heavier gauge steel : min. thickness ¼ inch (bottom), 3/16 inch (shell & deck)

 

Fixed roof  • Pe Permanently rmanently attached to tank shell • Welded tanks >500 bbl frangible Floating roof  • Tank roof floats on stored contents • Used for storage @ atmospheric pressure • Move vertically within tank shell Fabricated type: – Exposed to weather – Fixed roof 

• Popular: with external fixed roof   

Cone-bottom tank • Can be bolted or welded tank • Provide 100% draining and removing water, water cut oil from bottom of tank w/o coning oil into drain marketable oil at above • Minimum corrosion on tank bottom

• Easy cleaning  

Pipe Storage • Special for storing & handling liquid petroleum components • Consists of number of line pipe section laid parallel to each other & interconnected to operate as a single unit • P  Protected rotected from corrosion by cathodes cathodes protection or coating coating paint

 

Cathodic Protection •

 To control electrochemical corrosion

•

 Can be :

– internal : self-contained sacrificial anodes – External : direct current flow onto entire surface area

cathodic Recommended Re commended for pipe storage, pipelines, casing  

Transportation of Natural Gas The Transportation •

 The efficient and effective movement of natural gas from producing regions to consumption

•

regions requires an extensive and elaborate transportation system.   In many instances, instances, natural gas produced produced from a particular particular well will have to travel a great distance to reach its point of use.

•

  The The tr tran ansp spor orta tatio tion n sy syst stem em fo forr na natu tura rall ga gass co cons nsis ists ts of a co comp mple lex x ne netw twor ork k of pi pipe peli line nes, s, designed to quickly and efficiently transport natural gas from its origin, to areas of high natural gas demand.

•

  Transp ransportat ortation ion of natu natural ral gas is closely linked to its storage: should the natural gas being

transported not be immediately required, it can be put into  storage  storage facilities  facilities for when it is needed.  

The Transportation Transportation of Natural Gas •

•

  There are three major types of pipelines along the transportation route:   the gat gather hering ing sys system tem,, the int interst erstate ate pip pipeli eline ne sys system tem,, and the dis distrib tributi ution on sys system tem.. The gather gat hering ing sys system tem con consis sists ts of low pre pressu ssure, re, sma small ll dia diamete meterr pip pipeli elines nes tha thatt tra transp nsport ort raw natural gas from the wellhead to the processing plant.

•

  Should natural gas from a particular particular well have high sulfur and carbon dioxide contents contents (sour

gas), a specialized sour gas gathering pipe must be installed. i nstalled. •  

Transportation of Natural Gas The Transportation •

 Sour gas is corrosive, thus its transportation from the wellhead to the sweetening plant must be done carefully.

•

  Pe Pelines lines can be characterized as in inte ters rsta tate te or in intr tras asta tate te..

•

  Interstate pipelines are similar to in the interstate highway system:

•

  Th They ey ca carr rry y na natu tura rall ga gass ac acro ross ss st stat ate e bo boun unda dari ries es,, in so some me cas cases es cle clear ar acr acros osss th the e country.

 

Transportation of Natural Gas The Transportation •

  Intrastate pipelines, on the other hand, transport natural gas within a particular state.

•

 This section will cover only the fundamentals of interstate natural gas pipelines, however the technical and operational details discussed are essentially the same for intrastate pipelines.

 

Interstate Natural Gas Pipelines •

  The interstate natural gas pipeline network transports processed natural gas from proc pr oces essi sing ng pl plan ants ts in pr prod oduc ucin ing g re regi gion onss to th thos ose e ar area eass wi with th hi high gh na natu tura rall ga gass requirements, particularly large, populated urban areas.

•

 

Interstate Natural Gas Pipelines •

  Natural gas that is transported through interstate pipelines travels at high pressure in the pipeline, at pressures anywhere from 200 to 1500 pounds per square inch (psi). ( psi). This reduces the volume of the natural gas being transported (by up to 600 times), as well as propelling natural gas through the pipeline