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TM-3142 TEKNIKPRODUKSI GAS BUMI
Prepared by:
David Maurich, ST, MT.
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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
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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.
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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
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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]
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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
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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
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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
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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
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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.
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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
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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
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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$112.73/bbl)
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Indonesia Natural Gas Proved Reserve
800
900
1000
1100
1200
1300
1400
2002 2004 2006 2008 2010 2012
TCM
Year
Indonesia Natural Gas Proved Reserve
Reserve/Production: 41.2 Years
World Share : 1.6%
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Indonesia Natural Gas Production &Consumption
0.0
1.02.0
3.0
4.0
5.06.0
7.0
8.0
9.0
1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 2010 2014
BCF/D
Year
Indonesia Natural Gas Production & Consumption
Natural GasProduction
Natural GasConsumption
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Gas Prices
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
1984 1988 1992 1996 2000 2004 2008 2012
US$/MMBTU
Year
Gas Prices
LNG
Natural Gas
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Energy Prices Play A Key Role
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Gas Demand Growth Is Driven By Non-OECDNeeds
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BP Statistical Review of World Energy 2013 BP 2013
Gas reserves-to-production (R/P) ratiosYears
2012 by region History
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BP Statistical Review ofWorld Ener 2013
Distribution of proved gas reserves in 1992, 2002 and 2012Percentage
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BP Statistical Review ofWorld Ener 2013
Gas production/consumption by regionBillion cubic metres
Consumption by regionProduction by region
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BP Statistical Review ofWorld Ener 2013
Source: Includes data from Cedigaz.
Gas consumption per capita 2012Tonnes oil equivalent
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BP Statistical Review ofWorld Ener 2013
Gas prices$/Mmbtu
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BP Statistical Review ofWorld Ener 2013
Source: Includes data from Cedigaz, CISStat, GIIGNL, IHS CERA, Poten, Waterborne.
Major gas trade movements 2012Trade flows worldwide (billion cubic metres)
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Shale Gas & Tight Oil Resources &Production
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Shale Gas Growth Will Gradually SpreadBeyond The US
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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/8/10/2019 Introduction to Natural Gas Production Engineering.ppt
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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
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Tonggak Sejarah Dalam Industri MigasIndonesia (PricewaterhouseCoopers, 2011)
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Cadangan Minyak dan Gas Bumi dan
sebarannya di Indonesia
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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.
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Cadangan Hidrokarbon di Dunia
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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.
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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.
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Energy Resources
Renewable Energy Resources
(Solar, Wind, Bio-mass, hydal)
Non-Renewable Energy Resources
(Natural Gas, Petroleum, Coal)
General Classification of Fuels
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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.
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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
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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).
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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)
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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
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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
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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
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History of Natural Gas
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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
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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.
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SCHEMATIC ILLUSTRATION
OF DEPOSITIONAL SYSTEM
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SEDIMENTATION
ACCUMULATION TRANSFORMATION
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ACCUMULATION, TRANSFORMATIONAND MIGRATION
CnH2n+2COOH or CnH2nO2 +Temperatures
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WHAT MAKES OIL STAY IN THERE: TRAPS
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Exploration Production Shipping RefiningChemical
ManufacturingUses
Oil and Gas Process
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Concept of Natural Gas System
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A General Scheme
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CL SSIFIC TION OF THE E RTHS ORG NIC SEDIMENTS
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(termasuk isomernya)
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Classification of hydrocarbon
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Polydispersivity
GAS BUMI
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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.
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Contoh Komposisi dan Karakteristik Gas
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dan Minyak Bumi
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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
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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
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PHASE BEHAVIOR: RETROGRADE GAS
Kondisiawaldi reservoir
Kondisi didasar sumur
Separator
Temperatur
Tekanan
Diagram Fasa (P-T Diagram) Gas Kondensat
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g s ( g ) G s o de s
FLUID SYSTEM: WET GAS
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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
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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
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PHASE BEHAVIOR: WET GAS
Tekana
n
Temperatur
Kondisi awaldi reservoir
Kondisi didasar sumur
Separator
FLUID SYSTEM: DRY GAS
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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
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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.
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PHASE BEHAVIOR: DRY GAS
Tekanan
Temperatur
Kondisi awaldi reservoir
Dry gas
Kondisi di
dasar sumur
Separator
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EQUATION FOR IDEAL GAS
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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
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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
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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
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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
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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
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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
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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
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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
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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
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pressure at constant temperature
Law of Corresponding States
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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
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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
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properties of natural
gases
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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)
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gas (Standing & Katz)
Pseudocritical Properties
of Natural Gases
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of Natural Gases
Thepseudocriticalproperties ofgases can becomputedfrom the basiccomposition
but can also beestimatedfrom the gasgravity.
Impact of Nonhydrocarbon Components on z
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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
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factor () correlation
Where:
B = Mole fraction of H2S in the gas mixtureor (yH2S)
The Carr-Kobayashi-Burrows Correction Method
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(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
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pseudocritical properties
for non hydrocarbon
gases
(Wichert & Aziz)
Physical Properties for Pure Components
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EXERCISE-1
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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
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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
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Calculate the Z factor of gas from Exercise-1for P = 5420 psia and T = 275 oF?
solution
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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
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