TANZANIA PETROLEUM DEVELOPMENT COOPERATION (TPDC)

TITLE OF THE PAPER MECHANISM OF PRODUCTION OF DRY GAS FROM GAS WELLSABSTRACT This paper aims to discuss the useful methods in production of dry gas from reservoir of naturalgas, the paper ill consist of to parts the first part ill !e the introduction hich !ase on thegeneral concept of natural gas and the second part ill !e a!out the mechanism used to o!tainthe dry gas"1. INTRODUCTION#atural gasisasu!categoryof petroleumthat isanaturallyoccurringcomple$mi$tureofhydrocar!ons, ith the minor amount of inorganic compounds"%ethane is the ma&or componentof the gas mi$ture hile other hydrocar!ons li'e ethane, propane,i(!utane, n(!utane, i(pentane,n(pentane, he$ane, heptanes and heavier may !e found on natural gas in minor components" The inorganic compounds hich may !e found in the natural gas in small amount are car!ondio$ide hydrogen sulfide, hydrogen sulfide and nitrogen"1.1. Types ! "#$%' (#s There are three types of natural gas named as)i" #on associated gas ii" Associated gasiii" *as condensate N" #ss)*#$e+ gas is the reservoir ith minimal oilAss)*#$e+ (#s is the gas dissolved in oil under natural condition in the oil reservoirG#s )"+e"s#$eis the gas ith high content of li+uid hydrocar!on at reduced pressureand temperature"1.,.Types !-e''sThere three types of ellsi" ,rude oil ellsii" *as ellsiii" ,ondensate ells-"."-" CRUDE OIL WELLS)Ra natural gas that comes from crude oil ells is called #ss)*#$e+ (#s" This gas can e$istseparate from the crude oil in the underground formation, or dissolved in the crude oil" ,rude oilells are ells ith producing /*OR0 !eing less than 1,222 scf3st!-"."." GAS WELLSTheseells typicallyproduceonlyranatural gas that does not containanyhydrocar!onli+uids" 4uch gas is called non(associated gas, *as ells are ells ith producing gas oil ration/*OR0 !eing greater than -22,222scf3st!"-"."5" CONDENSATE WELLSTheseells produceranatural gas alongithnatural gas li+uid, suchgas is alsonon(associatedgasandoftenreferredtoaset gas" ,ondensateellsarethoseithproducing/*OR0 !eing less than -22,222scf3st!"In this paper I shall concentrate on gas ells and condensate ells",. BASIC CONCEPT OF NON ASSOCIATED NATURAL GAS PROCESSINGRa natural gas after transmission through the field(gathering netor'must !e processed !efore it can !e moved into long(distance pipelinesystem for use !y consumers" The o!&ective of gas processing is toseparate"i" #atural gasii" 6ateriii" ,ondensateiv" #on condensa!lev" Acid gasThe first unit module physical separation of the distinct phasesare typicallyi" *asii" Li+uid hydrocar!ons,iii" Li+uid ater, and3oriv" 4olids"v" Phase separation of the production stream is usually performed in an inletvi" 4eparator"Phase separation of the production stream is usually performed in an inlet separator"The follo chart of natural gas processing is shon in the figure !elo",.1. TRANSPORTED RAW GASThe ra gas for non associated gas is the gas hich contains the ma&or amount of methane andsmall amount of inorganic components li'e car!on dio$ide hydrogen sulfide, hydrogen sulfideand nitrogen",.,. PHASE SEPARATIONHydrocar!on condensate recovered from natural gas may !e shipped ithout further processing!ut is typically sta!ili7ed to produce a safe transporta!le li+uid" 8nsta!ili7ed condensates containa large percentage of methane and ethane, hich ill vapori7e easily in storage tan's",... GAS TREATINGThe ne$t step in natural gas processing is acid gas treating"In addition to heavy hydrocar!ons andater vapor, natural gas often contains other contaminants that may have to !e removed" ,ar!ondio$ide /,O.0, hydrogen sulfide /H.40, and other sulfur(containingpecies such as mercaptansare compounds that re+uire complete orpartial removal" These compounds are collectively'non as 9acidgases": H.4 hen com!ined ith ater forms a ea' sulfuric acid,hereas ,O.and ater formcar!onic acid,thus the term9acid gas":#aturalgas ith H.4 orothersulfurcompounds present is called 9sourgas,: hereas gas ith only ,O. is called 9seet":;oth H.4and ,O. are very undesira!le, as they cause corrosion"

The figure a!ove is seeting process for the sour gas,./. DEHYDRATION PROCESS#atural gas dehydration is the process of removing ater vapor from the gas stream to loer thedepoint of that gas" Thedepoint is definedas thetemperatureat hichater vaporcondenses from the gas stream"The sale contracts of natural gas specify either its de point orthe ma$imum amount of ater vapor present"There are to !asic reasons for the dehydration of natural gas streams)i" To prevent hydrate formation"ii" To avoid corrosion pro!lems"The methods of dehydration are)"."