introduction to natural gas production engineering.ppt

8/10/2019 Introduction to Natural Gas Production Engineering.ppt

1/105

TM-3142 TEKNIKPRODUKSI GAS BUMI

Prepared by:

David Maurich, ST, MT.


2/105

Sistem Evaluasi

Kriteria Penilaian: Absensi Kehadiran = 10 % Tugas (PR) = 20 % Ujian Tengah Semester (UTS) = 30 %

Ujian Akhir Semester (UAS) = 40 %

Sumber Bahan Ujian:

1. Text Book2. Catatan Kuliah di Kelas3. PR4. Slide


3/105

Pustaka

Lee, W.J. and Wattenbarger, R.A.: GasReservoir Engineering, SPE (1996).

Ikoku. Chi U. (1984), Natural Gas Reservoir

Engineering, John Wiley & Sons,. Other text/reference materials will be given out

as needed-either in paper or electronic form.


4/105

SATUAN ACARA PERKULIAHAN

Pertemuan Pokok Bahasan

Minggu 1 Pengenalan & sifat-sifat gas alamMinggu 2 Perkiraan cadanganMinggu 3 DeliverabilityMinggu 4 Pengaruh komplesi sumur

Minggu 5 Aliran gas dalam pipaMinggu 6 Aliran gas dalam pipa: pengaruh adanya fluida di dalam aliran gas

Minggu 7 Analisis nodal untuk aliran gasMinggu 8 Pengukuran laju alir gasMinggu 9 Ujian Tengahan Semester (UTS)Minggu 10 Decline curve analisis

Minggu 11 Kinerja reservoirMinggu 12 Kinerja reservoirMinggu 13 Reservoir gas kondensat

Minggu 14 Studi kasus dan praktek dengan menggunakan Tools: Prosper, PipesimMinggu 15 Ujian Akhir Semester


5/105

Format Laporan PR

Tugas-tugas Pekerjaan Rumah (PR) memiliki bobot20% dari total nilai akhir mata kuliah.

PR harus dikerjakan sendiri, menyontek/kecuranganakan diberi nilai 0bagi yang mencontek dan yangmemberi contekan (indikasi: jawaban persis

sama/sangat mirip sekali). Untuk menyeragamkan Laporan, maka dibuat format

laporan seperti di Lampiran. Laporan PR boleh dikerjakan dengan komputer atau

tulisan tangan yang rapi. Untuk plot, grafik, gambar atau perhitungan yang

rumit sebaiknya dikerjakan dengan bantuankomputer.

Informasi lain yang belum jelas dapat ditanyakanlewat email saya: [email protected]


6/105

Anggaran Pendapatan dan Belanja NegaraPerubahan 2013 (APBNP 2013) yang dinyatakandalam Undang-Undang Nomor 15 Tahun 2013,pemerintah dan DPR menyepakati:

1. Penerimaan negara dari pajak penghasilan (PPh)migas adalah Rp.74,28 triliun atau 4,95% dari targetpenerimaan negara 2013.

2. Penerimaan negara bukan pajak (PNBP) dari sektormigas ditargetkan Rp.180,61 triliun atau 12,02% daritotal penerimaan negara.

3. Total penerimaan negara dari sektor migas adalahRp.254,89 triliun atau 16,97% dari total pendapatannegara.

Peranan Migas Dalam Pembangunan Nasional


7/105

Peranan Migas Dalam APBN

0

200

400

600

800

1,000

1,200

1,400

1,600

2005 2006 2007 2008 2009 2010 2011 2012 2013

495.22

637.99707.81

981.61

848.76

995.27

1,210.60

1,358.21

1,502.01

138.91

201.27

168.78

288.64

175.80211.61

266.59 266.23 254.89

3.19 6.78 5.88 10.45 10.77 12.99 16.93 15.62 18.62Pendapatan(Rp.Triliun)

Tahun

Pendapatan+Hibah (Negara)Pendapatan Migas

Pendapatan Tambang+Panas Bumi


8/105

Persentase Penerimaan Negara (APBN) DariSektor Migas

28.05

31.55

23.85

29.40

20.7121.26

22.02

19.60

16.97

15

17

19

21

23

25

27

29

31

33

2005 2006 2007 2008 2009 2010 2011 2012 2013

Persenta

se(%)

Tahun


9/105

Subsidi BBM

95.6

64.2

83.8

139.1

45.0

82.4

165.2

137.4

199.9

0

50

100

150

200

250

2005 2006 2007 2008 2009 2010 2011 2012 2013

Su

bsisdi(Rp.Triliun)

Tahun


10/105

Latar elakang

Setelah tahun 2002 konsumsi minyak Indonesialebih besar dari produksi minyak nasional.

Cadangan minyak terbukti Indonesia tahun 2012sebesar 3,74 MMMBbls dan cenderung turun

terus. Produksi minyak sebesar 917,75 MBbl/D. Peningkatan produksi minyak hanya bisa

dicapai dengan kegiatan eksplorasi danimplementasi teknologi EOR.


11/105

Produksi Minyak Cenderung Turun Terus Di BawahJumlah Konsumsi Minyak Yang Cenderung Naik

-

200

400

600

800

1000

1200

1400

1600

1800

1965 1975 1985 1995 2005 2015

MBbls/D

Year

Indonesia Oil Production & Consumption

Consumption

Production

2012: Produksi = 917,75 MBbl/D;Konsumsi =1565,24 Mbbl/D

Total impor minyak tahun 2012 = 77.963.403 BOE,Impor produk BBM tahun 2011 = 27.366 ribu kL


12/105

1

7

13

19

25

31

37

1980 1984 1988 1992 1996 2000 2004 2008 2012

MMMBbls

Year

Oil Proved Reserves History

US China India Indonesia Malaysia

Cadangan Minyak Terbukti Indonesia Pada Akhir Tahun 2012Sekitar 3,74 Milyar bbls & Cenderung Turun Dari Tahun Ke Tahun


13/105

10

2030

40

50

60

70

80

90

100

110120

1975 1980 1985 1990 1995 2000 2005 2010 2015

US$/Bbl

Year

Spot Crude Prices

Mix (Dubai, Brent, Nigerian Forcados, West TexasIntermediate)ICP (Indonesia Crude Price)

Harga Minyak Cenderung Naik Terus Sejak Tahun 1995(Tahun 2012: US$112.73/bbl)


14/105

Indonesia Natural Gas Proved Reserve

800

900

1000

1100

1200

1300

1400

2002 2004 2006 2008 2010 2012

TCM

Year

Indonesia Natural Gas Proved Reserve

Reserve/Production: 41.2 Years

World Share : 1.6%


15/105

Indonesia Natural Gas Production &Consumption

0.0

1.02.0

3.0

4.0

5.06.0

7.0

8.0

9.0

1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 2010 2014

BCF/D

Year

Indonesia Natural Gas Production & Consumption

Natural GasProduction

Natural GasConsumption


16/105

Gas Prices

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

1984 1988 1992 1996 2000 2004 2008 2012

US$/MMBTU

Year

Gas Prices

LNG

Natural Gas


17/105

Energy Prices Play A Key Role


18/105

Gas Demand Growth Is Driven By Non-OECDNeeds


19/105

BP Statistical Review of World Energy 2013 BP 2013

Gas reserves-to-production (R/P) ratiosYears

2012 by region History


20/105

BP Statistical Review ofWorld Ener 2013

Distribution of proved gas reserves in 1992, 2002 and 2012Percentage


21/105


Gas production/consumption by regionBillion cubic metres

Consumption by regionProduction by region


22/105


Source: Includes data from Cedigaz.

Gas consumption per capita 2012Tonnes oil equivalent


23/105


Gas prices$/Mmbtu


24/105


Source: Includes data from Cedigaz, CISStat, GIIGNL, IHS CERA, Poten, Waterborne.

Major gas trade movements 2012Trade flows worldwide (billion cubic metres)


25/105

Shale Gas & Tight Oil Resources &Production


26/105

Shale Gas Growth Will Gradually SpreadBeyond The US


27/105

No. Country Date No. Country Date

1 AUSTRALIA 7-Jun-71 18 JAPAN 28-Apr-64

2 AUSTRIA 29-Sep-61 19 KOREA 12-Dec-96

3 BELGIUM 13-Sep-61 20 LUXEMBOURG 7-Dec-61

4 CANADA 10-Apr-61 21 MEXICO 18-May-94

5 CHILE 7-May-10 22 NETHERLANDS 13-Nov-61

6 CZECH REPUBLIC 21-Dec-95 23 NEW ZEALAND 29-May-737 DENMARK 30-May-61 24 NORWAY 4-Jul-61

8 ESTONIA 9-Dec-10 25 POLAND 22-Nov-96

9 FINLAND 28-Jan-69 26 PORTUGAL 4-Aug-61

10 FRANCE 7-Aug-61 27 SLOVAK REPUBLIC14-Dec-00

11 GERMANY 27-Sep-61 28 SLOVENIA 21-Jul-10

12 GREECE 27-Sep-61 29 SPAIN 3-Aug-61

13 HUNGARY 7-May-96 30 SWEDEN 28-Sep-61

14 ICELAND 5-Jun-61 31 SWITZERLAND 28-Sep-61

15 IRELAND 17-Aug-61 32 TURKEY 2-Aug-61

16 ISRAEL 7-Sep-10 33 UNITED KINGDOM 2-May-61

17 ITALY 29-Mar-62 34 UNITED STATES 12-Apr-61

Organisation for Economic Co-operation andDevelopment (OECD)
http://www.oecd.org/australia/http://www.oecd.org/japan/http://www.oecd.org/austria/http://www.oecd.org/korea/http://www.oecd.org/korea/http://www.oecd.org/belgium/http://www.oecd.org/belgium/http://www.oecd.org/luxembourg/http://www.oecd.org/luxembourg/http://www.oecd.org/canada/http://www.oecd.org/mexico/http://www.oecd.org/chile/http://www.oecd.org/netherlands/http://www.oecd.org/netherlands/http://www.oecd.org/czech/http://www.oecd.org/czech/http://www.oecd.org/newzealand/http://www.oecd.org/denmark/http://www.oecd.org/norway/http://www.oecd.org/estonia/http://www.oecd.org/poland/http://www.oecd.org/finland/http://www.oecd.org/portugal/http://www.oecd.org/portugal/http://www.oecd.org/france/http://www.oecd.org/slovakia/http://www.oecd.org/slovakia/http://www.oecd.org/germany/http://www.oecd.org/germany/http://www.oecd.org/slovenia/http://www.oecd.org/greece/http://www.oecd.org/spain/http://www.oecd.org/hungary/http://www.oecd.org/hungary/http://www.oecd.org/sweden/http://www.oecd.org/sweden/http://www.oecd.org/iceland/http://www.oecd.org/switzerland/http://www.oecd.org/switzerland/http://www.oecd.org/ireland/http://www.oecd.org/turkey/http://www.oecd.org/israel/http://www.oecd.org/unitedkingdom/http://www.oecd.org/unitedkingdom/http://www.oecd.org/italy/http://www.oecd.org/unitedstates/http://www.oecd.org/unitedstates/http://www.oecd.org/italy/http://www.oecd.org/unitedkingdom/http://www.oecd.org/israel/http://www.oecd.org/turkey/http://www.oecd.org/ireland/http://www.oecd.org/switzerland/http://www.oecd.org/iceland/http://www.oecd.org/sweden/http://www.oecd.org/hungary/http://www.oecd.org/spain/http://www.oecd.org/greece/http://www.oecd.org/slovenia/http://www.oecd.org/germany/http://www.oecd.org/slovakia/http://www.oecd.org/france/http://www.oecd.org/portugal/http://www.oecd.org/finland/http://www.oecd.org/poland/http://www.oecd.org/estonia/http://www.oecd.org/norway/http://www.oecd.org/denmark/http://www.oecd.org/newzealand/http://www.oecd.org/czech/http://www.oecd.org/netherlands/http://www.oecd.org/chile/http://www.oecd.org/mexico/http://www.oecd.org/canada/http://www.oecd.org/luxembourg/http://www.oecd.org/belgium/http://www.oecd.org/korea/http://www.oecd.org/austria/http://www.oecd.org/japan/http://www.oecd.org/australia/


28/105

Visi Pengusahaan Migas Di Indonesia:

Memanfaatkan migas untuk sebesar-besarnyakemakmuran rakyat (pasal 33 UUD 1945).

Strategi Pengelolaan Migas di Indonesia:

Kontrak Bagi Hasil (Production Sharing Contract-PSC)sebagaimana diatur dalam Undang-Undang RepublikIndonesia Nomor 22 Tahun 2001 Tentang Minyak & GasBumi dimana manajemen ada ditangan pemerintah.

Tujuan Jangka Panjang PSC:Mengusahakan minyak kita sedapat mungkin oleh kitasendiri.

Tinjauan Industri Migas Indonesia


29/105

Tonggak Sejarah Dalam Industri MigasIndonesia (PricewaterhouseCoopers, 2011)


30/105

Cadangan Minyak dan Gas Bumi dan

sebarannya di Indonesia


31/105


32/105


33/105


34/105

Tantangan Ke Depan dalam ProsesPeningkatan Produksi dan Perolehan MInyak

Peningkatan produksi minyak hanya bisa dicapaidengan kegiatan eksplorasi dan implementasiteknologi EOR atau pemanfaatan unconventionalresources (heavy oils, oil & gas sand/shale, CBM,

gas hydrate, dll.) yang membutuhkan teknologidan keahlian yang tinggi.

Kegiatan eksplorasi migas butuh investasi & biayayang sangat besar,tingkat keberhasilan untukmenemukan migas hanya sekitar 30%-40% danbanyaknya di laut dalam sementara anggaranminim.


35/105

Cadangan Hidrokarbon di Dunia


36/105

GAS HYDRATES

Gas Hydrate Value of X

Methane CH4. XH2O 6to 7

Ethane C2H6. XH2O 6to 8

Propane C3H8. XH2O 7to 18

Carbon dioxide CO2. XH2O 6to 7Natural gas NG . XH2O 9

1 ft3of liquid methane@ 260oF 630 ft3of gaseous methane

Temperatures > 260oF can be used if the liquid state is maintained at 325 psigand

155oF.


37/105

LIQUEFIED NATURAL GASLNG

1 Gallon of LNG@ 263oF

weighs 3.46 lbs

has a specific gravityof 0.42

has a heating valueof approximately86,000 Btu

Heat of Vaporizationof LNG at 1 atm 10 Btu/SCF

It requires 6575 Btuto vaporise 1 cu ftof liquid methane.


38/105

Energy Resources

Renewable Energy Resources

(Solar, Wind, Bio-mass, hydal)

Non-Renewable Energy Resources

(Natural Gas, Petroleum, Coal)

General Classification of Fuels


39/105

General Classification of Fuels

FUELS

Conventional Nuclear

Natural or Fossil Manufactured or Synthetic 238U92;238U92;

239Pu93

Solid

Liquid

Gaseous

Wood , Coal

Petroleum

Natural GasCoal Bed Methane(CBM)

Marsh Gas

Solid

Liquid

Gaseous

Coke , Charcoals

Alcohols

Coal gasCoke oven gasProducer gas

Water gasHydrogen , etc.


40/105

What is natural gas? Natural gas is a subcategory of petroleum that is a naturally

occurring, complex mixture of hydrocarbons, with a minoramount of inorganic compounds.

Geologists and chemists agree that petroleum originatesfrom plants and animal remains that accumulate on thesea/lake floor along with the sediments that formsedimentary rocks

The processes by which the parent organic material isconverted into petroleum are not understood.

The contributing factors are thought to be bacterial action;

shearing pressure during compaction, heat, and naturaldistillation at depth; possible addition of hydrogen fromdeep-seated sources; presence of catalysts; and time(Allison and Palmer 1980).

NATURA GAS


41/105

NATURAL GAS

Definition(in normal usage) :

Natural Gas in normal usage, is considered to be a

naturally occurring mixture of hydrocarbons[C1, C2, C3, C4, C5, C6+]and non-hydrocarbons

[CO2, N2, He , H2O , H2S, RSH, COS, CS2,

etc.]associated with petroliferous geologicformations (rocks in earths crust).


42/105

Natural Gases as supplied by the utility gas companies,

usual ly

contain 80to 95% CH4, with C2H6,C3H8 ,N2,etc. making up the remainder.

have heatingor calorific valueranging from 900 to 1200 Btu/SCF.

have specific gravity(w.r.t. air = 1.0) varying from 0.58 to 0.79.

Methane (CH4) (Some properties )

Auto- or Spontaneous-ignition Temperature : 1004oF (540oC)

Flammability Limits : 5% to 15% v

Critical Pressure : 673 psia (45.8 atm)

Critical Temp.: 116.3oF (343.7 oR) OR 82.4oC (191 oK)

( For other properties, see literature)


43/105

Generally,

1000 sft3( 1 MSCF )ofNatural Gas is equivalent to :

58 kg of Wood

52 kg of (indigenous)Coal

28 liters of Kerosene

0.168 barrel of Crude Oil(petroleum)

285 kwh of Electricity

0.024 tonne of Furnace Oil

21 kg of LPG


44/105

Raw Gas

Water

Helium

Nitrogen

Carbon dioxide

Hydrogen sulphide

Methane

Ethane

Propane

N-Butane

i-Butane

Pentanes +

GasProcessing

Product Slate

Water

HeliumNitrogen

Carbon dioxide

Hydrogen sulphide

Pipeline gas(Methane)

Ethane

Propane

n-Butane

i-Butane

Natural gasoline

Hydrocarbons Combustiblesvs


45/105

Hydrocarbons Non-hydrocarbons

Water H2O

Carbon dioxide CO2

Nitrogen N2

Helium He

Hydrogen sulphide H2SMercaptans RSH

Carbon oxysulphide COS

Carbon disulphide CS2

Methane C1

Ethane C2

Propane C3

n-Butane n-C4

i-Butane i-C4

Pentanes C5

Hexanes+ C6+

Natural GasConstituents

Hydrocarbons Non-hydrocarbons

Water H2O

Carbon dioxide CO2

Nitrogen N2

Helium He

Hydrogen sulphide H2SMercaptans RSH

Carbon oxysulphide COS

Carbon disulphide CS2

Methane C1

Ethane C2

Propane C3

n-Butane n-C4

i-Butane i-C4

Pentanes C5

Hexanes+ C6+

Natural GasConstituents

Combustibles

Natural Gas

Constituents

Non-combustibles

H2O

CO2

N2

He

HCs

H2S

RSH

COS

CS2

Combustibles

Natural Gas

Constituents

Non-combustibles

H2O

CO2

N2

He

HCs

H2S

RSH

COS

CS2

vsNon-hydrocarbons

vsNon- combustibles


46/105

History of Natural Gas


47/105

PETROLEUM ORIGIN

Petroleum occurs underground, at various pressuresdepending on the depth.

Because of the pressure, it contains considerablenatural gas in solution.

Petroleum is derived from aquatic plants and animals

that lived and died hundreds of millions of years ago. Their remains mixed with mud and sand in layered

deposits that, over the millennia, were geologicallytransformed into sedimentary rock.

Gradually the organic matter decomposed andeventually formed petroleum, which migrated fromthe original source beds to more porous andpermeable rocks, such as sandstone and siltstone,where it finally became entrapped. Such entrapped

accumulations of petroleum are called reservoirs.

IDEAL CONDITION FOR OIL AND


48/105

IDEAL CONDITION FOR OIL ANDGAS FORMATION

Hydrocarbon Oil: Temperature between180oF and 295 oF (7,00015,000 ft)

Hydrocarbon gas: Temperature between295 oF and 450 oF (15,00025,000 ft).

CO2and H2O: Temperature above 450oF.


49/105

SCHEMATIC ILLUSTRATION

OF DEPOSITIONAL SYSTEM


50/105

SEDIMENTATION

ACCUMULATION TRANSFORMATION


51/105

ACCUMULATION, TRANSFORMATIONAND MIGRATION

CnH2n+2COOH or CnH2nO2 +Temperatures


52/105

WHAT MAKES OIL STAY IN THERE: TRAPS


53/105

Exploration Production Shipping RefiningChemical

ManufacturingUses

Oil and Gas Process


54/105

Concept of Natural Gas System


55/105

A General Scheme


56/105

CL SSIFIC TION OF THE E RTHS ORG NIC SEDIMENTS


57/105

(termasuk isomernya)


58/105


59/105


60/105

Classification of hydrocarbon


61/105


62/105

Polydispersivity

GAS BUMI


63/105

GAS BUMI

Gas bumi adalah campuran hidrokarbon ringan dengan komponenutamanya C1atau metana. Kandungan (fraksi mol) C1didalamsuatu reservoir dapat berbeda dibanding dengan reservoir lain.

Kandungan C1di suatu reservoir dapat mencapai lebih dari 95%,tetapi banyak reservoir memiliki kandungan C1hanya 70% atau

bahkan kurang dengan komponen sisanya adalah C2, C3, C4, dst.plus seringkali gas non-hidrokarbon seperti N2, CO2, H2S, He.

Gas bumi pada kondisi awal didalam reservoir berbentuk fasa gas.

Gas bumi bila diproduksikan dari dalam reservoir akan

menghasilkan di permukaan hanya gas saja ataugas dan cairanhidrokarbon (kondensat), tergantung dari komposisi gas itudidalam reservoir.

Oleh karena itu, reservoir gas dapat dikatagorikan atas: reservoirgas kering, reservoir gas basah, dan reservoir gas kondensat.


64/105

Contoh Komposisi dan Karakteristik Gas


65/105

dan Minyak Bumi


66/105

Karakteristik Gas Bumi

1. Reservoir gasdapat dikelompokkan atas reservoir gaskering, reservoir gas basah dan reservoir gas kondensat.

2. Reservoir gas keringmenghasilkan sangat sedikit

sekali hidrokarbon cair dipermukaan.

3. Reservoir gas basahmenghasilkan hidrokarbon cair dipermukaan dengan GORjauh diatas 15000 SCF/STB.

4. Reservoir gas kondensatbisa menghasilkanhidrokarbon cair dipermukaan dengan GORdi atas 3500SCF/STB.

FLUID SYSTEM: RETROGRADE GAS


67/105

FLUID SYSTEM: RETROGRADE GAS

Retrograde Gas

Mid 50s < oAPI < 70

Condensate = 0.25 cp1.5 < B < 2.5 to 3.53300 < Rinitial< 15,000 to 50,000

Gas at initial condition

Large quantities ofcondensate drop out inthe surface facilities

Condensate drop outin the formation

PHASE BEHAVIOR RETROGRADE GAS


68/105

PHASE BEHAVIOR: RETROGRADE GAS

Kondisiawaldi reservoir

Kondisi didasar sumur

Separator

Temperatur

Tekanan

Diagram Fasa (P-T Diagram) Gas Kondensat


69/105

g s ( g ) G s o de s

FLUID SYSTEM: WET GAS


70/105

Wet Gas

o

API >60Condensate = 0.25 cp

1.5 < B < 2.5 to 3.515,000 to 50,000 < Rinitial< 100,000

Gas at initial condition

Condensate drop out inthe surface facilities

Diagram Fasa (P-T Diagram) untuk Gas Basah


71/105

Ciri-ciri Gas Basah (Wet Gas): gas yg diproduksikan ke permukaan (separator)menghasilkan cairan hidrokarbon (kondensat) dengan Gas-Oil Ratio atau Gas-Condensate Ratio dapat mencapai puluhan ribu SCF/STB. Komponen C1 dapatmencapai 85% dan kandungan C2 C6 lebih banyak dibanding gas kering.Komposisi gas separator beda dengan komposisi gas di reservoir. Air terkondensasi

seringkali juga dihasilkan di separator.

PHASE BEHAVIOR WET GAS


72/105

PHASE BEHAVIOR: WET GAS

Tekana

n

Temperatur

Kondisi awaldi reservoir

Kondisi didasar sumur

Separator

FLUID SYSTEM: DRY GAS


73/105

Gas is composed primarily of methanewith only small amounts of ethane,propane and butane

Produce no condensate

Diagram Fasa (P-T Diagram) untuk Gas Kering


74/105

g s ( g ) u u G s e g

Ciri-ciri gas kering (Dry Gas): gas yg diproduksikan ke permukaan (separator)menghasilkan kondensat hidrokarbon sedikit sekali atau bahkan tidak NOL.Komponen C1 dominan plus sedikit C2 C4 dan mungkin ada C5+. Komposisigas di reservoir boleh dikatakan samna dengan komposisi di separator dan SG-nya juga sama. Seringkali kondensat air (H2O) dihasilkan juga.


75/105

PHASE BEHAVIOR: DRY GAS

Tekanan

Temperatur

Kondisi awaldi reservoir

Dry gas

Kondisi di

dasar sumur

Separator


76/105


77/105

EQUATION FOR IDEAL GAS


78/105

EQUATION FOR IDEAL GAS

For n moles the equation becomes:

T= absolute temperature oK or oR where

K=273 +o

C ando

R=460 +o

F To find the volume occupied by a quantity

of gas, when the conditions of

temperature and pressure are changedfrom state 1 to state 2 we note that:

The Density of an Ideal Gas


79/105

The Density of an Ideal Gas

Density is defined as the weight per unitvolume, the ideal gas law can be used tocalculate densities.

For 1 mole; m = MW

Standard Conditions


80/105

Sta da d Co d t o s

Oil and gas at reservoir conditions clearly occurunder a whole range of temperatures andpressures.

It is common practice to relate volumes toconditions at surface, ie 14.7 psia and 60F.

This relationship assumes that reservoirproperties behave as ideal.

sc - standard conditions res - reservoir conditions

Mixtures of Ideal Gases


81/105

Mixtures of Ideal Gases

Petroleum engineering is concerned notwith single component gases but mixturesof a number of gases.

Laws established over early yearsgoverning ideal gas mixtures includeDaltons Law and Amagats Law.

Apparent Molecular Weight


82/105

Apparent Molecular Weight

A mixture does not have a molecularweight although it behaves as though ithad a molecular weight. This is called theapparent molecular weight(AMW)

If yjrepresents the mole fraction of the jthcomponent:

AMW for air = 28.97, a value of 29.0 isusually sufficiently accurate

Specific Gravity of a Gas


83/105

Specific Gravity of a Gas

The specific gravity of a gas, gis the ratio

of the density of the gas relative to that ofdry air at the same conditions.

Where:

Assuming that the gases and air are ideal.

Mg= AMW of mixture, Mair= AMW of air.

BEHAVIOUR OF REAL GASES


84/105

BEHAVIOUR OF REAL GASES

The ideal gas law, therefore, is not tooapplicable to light hydrocarbons and theirassociated fluids and it is necessary to usea more refined equation.

There are two general methods ofcorrecting the ideal gas law equation:

(1) By using a correction factor in theequation PV = nRT

(2) By using another equation-of-state(EOS)

Compressibility Factor (Z) for Natural Gases


85/105

The correction factor z which is a function ofthe gas composition, pressure and temperatureis used to modify the ideal gas law to:

z is an expression of the actual volume to whatthe ideal volume would be.

The factor z is known as the compressibilityfactor & the equation is known as thecompressibility equation-of-state or thecompressibility equation.

Compressibility Factor (Z) for Natural


86/105

Compressibility Factor (Z) for Natural

Gases

The compressibility factor is not a constantbut varies with changes in gascomposition, temperature and pressure

and must be determined experimentally. To compare two states the law now takes

the form:

Typical plot of the compressibility factor as a function of


87/105

pressure at constant temperature

Law of Corresponding States


88/105

p g

The law of corresponding states shows that the properties ofmany pure liquids and gases have the same value at the same

reduced temperature (Tr) and pressure (Pr) where:

Where, Tcand Pcare the pure component critical temperature

and pressure. Although in many cases pure gases follow the Law of

Corresponding States, the gases associated with hydrocarbonreservoirs do not. The Law has however been used to apply tomixtures by defining parameters calledpseudo criticaltemperature and pseudocritical pressure.

For mixtures a pseudocritical temperature and pressure, Tpcand Ppcis used such that:

the pseudo-critical pressure


89/105

and pseudo-critical temperature of gases correlation

Brown et al. (1948) presented in a graphical method. Standing (1977) expressed this graphical correlation in

the following mathematical forms:

Natural Gas Systems

Gas-Condensate Systems

Pseudo-critical

properties of natural


90/105

properties of natural

gases


91/105

For mixtures the compressibility factor (z)has been generated with respect to naturalgases, where z is plotted as a function of

pseudo reduced temperature, Tprandpseudo reduced pressure Pprwhere

Compressibility factors for natural

gas (Standing & Katz)


92/105

gas (Standing & Katz)

Pseudocritical Properties

of Natural Gases


93/105

of Natural Gases

Thepseudocriticalproperties ofgases can becomputedfrom the basiccomposition

but can also beestimatedfrom the gasgravity.

Impact of Nonhydrocarbon Components on z


94/105

value

Components like hydrogen sulphide, and carbondioxide have a significant impact on the value of z. Ifthe method previously applied is used large errors inz result.

Wichert and Aziz have produced an equation whichenables the impact of these two gases to becalculated.

T'pcand P'pcare used to calculate Tprand Ppr. Thevalue for is obtained from the Wichert and Azizchart or correlation.

Wichert and Aziz pseudo-critical temperature adjustment


95/105

factor () correlation

Where:

B = Mole fraction of H2S in the gas mixtureor (yH2S)

The Carr-Kobayashi-Burrows Correction Method


96/105

(1954)

A simplified procedure to adjust thepseudo-critical properties of natural gaseswhen nonhydrocarbon components arepresent.

The method can be used when thecomposition of the natural gas is notavailable.

Adjustment factors for

pseudocritical properties


97/105

pseudocritical properties

for non hydrocarbon

gases

(Wichert & Aziz)

Physical Properties for Pure Components


98/105


99/105


100/105


101/105

EXERCISE-1


102/105

By using Wichert and Aziz method,calculate the pseudo critical properties ofthe gas which is made up of the following

components; 25 lb of methane, 3 lb ofethane and 1.5 lb of propane, if it alsocontained 3 lb of hydrogen sulphide, 10 lb

of carbon dioxide and 2.5 lb of nitrogen.

solutionC W i h M l F i P T


103/105

From Wichert & Azis chart for compositions of H2S and CO2, it is obtained = 19

Components(j)

Weight(lb)

MW lb moleMole Fraction

(Yj)P

c

(Psi)Y

jP

cj

Tc

(oR)Y

jT

cj

C1 25 16.04 1.5586 0.743 667 495.783 344 255.696

C2 3 30.07 0.0998 0.048 708 33.686 550 26.169C

3 1.5 44.09 0.0340 0.016 616 9.995 666 10.806

H2S 3 34.08 0.0880 0.042 1306 54.827 673 28.253

CO2 10 44.01 0.2272 0.108 1071 116.056 548 59.383

N2 2.5 28.02 0.0892 0.043 493 20.977 227 9.659

Total 45 2.0969 1 731.324 389.965

EXERCISE-2


104/105

Calculate the Z factor of gas from Exercise-1for P = 5420 psia and T = 275 oF?

solution


105/105

From solution of Exercise-1 it is found that: T'pc= 371

oR

P'pc = 694.3 psia

Thus; Tpr = T/Tpc= (275

oF+460)/371 oR= 1.98

Ppr = P/Ppc= 5420 psia/694.3 psia = 7.81

From Standing & Katz chart, Z is found to be1.05

introduction to natural gas production engineering.ppt

Documents