PENGENALAN

GEOLOGI PETROLEUM

(E0005)

PENGENALAN

• Kandungan Kursus:

1. Pengenalan kepada geologi petroleum; sejarah eksplorasi, sifat kimia dan fizik, kaedah eksplorasi, akumulasi, asalmula dan perpindahan, perangkap dan reservoir petroleum (termasuk konsep rezab dan sumber).

PENGENALAN

2. Rujukan:

1. Selly, R.C. Elements of Petroleum Geology

PENGENALAN

• Apakah ‘petroleum’?:

• Berasal drp perkataan Greek bermaksud ‘rock oil’ atau minyak batuan.

• Boleh didefinasi sebagai bahan terbentuk secara semulajadi, nonrenewable fossil fuel, terutamanya terdiri daripada campuran hidrokarbon dalam bentuk fasa gas, cecair dan pepejal.

PENGENALAN: Sejarah Ringkas

• Ringkasan Sejarah Eksplorasi Petroleum:

• Herodotus 450 BC – tirisan (seeps) asli

• Kegunaan awal: perubatan, waterproofing, warfare Nabi Noh guna pitch untuk gegala kapal

• Sehingga pertengahan kurun 19: semua minyak dikeluarkan dari tirisan, lubang cetek dan perigi digali dengan tangan

• James Young: cerakin minyak dari carboniferous shales, Scotland 1847: “oil-shales”

PENGENALAN: Sejarah Ringkas

• Perigi pertama utk cari minyak = Pechelbronn, Peranchis, 1745

• Perigi pertama mengeluar minyak: Oil creek, Pennsylvania oleh “Colonel” Drake pd tahun 1859.

• Pemangkin utama pengeluaran minyak bermula apabila diperkenal internal combustion engine dlm tahun 1870 dan 1880.

• Peningkatan penggunaan bertambah WWI (1914-18)

PENGENALAN: Sejarah Ringkas

• Tahun 1920 industri minyak di dominasi oleh “seven sisters”

• Selepas WWII, syarikat minyak mula mencari keuntungan dgn eksplorasi dari satu kawasan pengeluaran ke kawasan lain.

• 1960: Organization of Petroleum Exporting Countries (OPEC) ditubuh di Baghdad (Iraq) Objective: control the power of the

independent oil companies by price control & appropriation of company assets

Sifat Fizik & Kimia Minyak dan gas

Hidrokarbon: terdiri drp H dan C

Gas Cecair;Oil, Crude

Solid;Asphalts, Coals, Kerogen

Wetethane, propane

Drymethane

Gas Asli Cecair (NGL)

Dikelaskan kpd:

Hydrocarbon Gases

Methane (dry)

Ethane (wet)PropaneButane

ORGANIC ORIGIN

Inert GasesHeliumArgon

KryptonRadon

NitrogenAlso

Carbon dioxideHydrogen sulphide

INORGANIC ORIGIN

Sifat Kimia Petroleum

• Komponen utama hidrokarbon dibahagi kepada 2 siri:

1. Siri Parafin atau n-alkana (hc tepu)

2. Siri Naftena

1. Siri Parafin Hc berantai lurus yg memp. formula CnH2n+2

CH4 metana…C2H6 etana

Cecair pertama adalah n-pentana (C5H12)

Pepejal pertama adalah n-heksadekana C16H34

Parafin / Alkana

Naftena atau Sikloparafin

• 2. Siri Naftena

• Formula umum CnH2n

• Terdiri drp hc gegelang atau sikloparafin.

• C3H6 siklopropana and C4H8 siklobutana = gas

• Cecair pertama adalah siklopentana C5H10

Sikloparafin

Aromatik

• 3. Aromatik; sebatian gegelang tak tepu

• Berdasar kpd rantai gegelang benzena CnH2n-6

So What’s the Best Oil?

• Parrafin-based crudes – historically and still the best prized Relatively rare in world terms

• Asphalt based crudes Dominant naphthenic components ~15% world crudes including nearly all Middle

East

Komponen Lain A Typical GC Trace

Sifat Fizik Petroleum

• Warna: kuning, hijau, coklat hingga coklat gelap & hitam• Kelikatan: Pelbagai, di permukaan bumi minyak menjadi

lebih likat. • Ketumpatan: Kebanyakan minyak lebih ringan drp air.

Biasanya diukur sebagai perbezaan antara ketumpatan bandingannya (SG) dengan ketumpatan bandingan air:

Minyak ringan mempunyai API > 40° dan minyak berat memp. API graviti < 10° (SG=1)

°API = 141.5

SG 60/60°F - 131.5

KAEDAH EKSPLORASI

Stage Data & Objektif Aktiviti Result

Eksplorasi Seismic lines

Cadangan telaga eksplorasi

Anggaran Rezab dan Perolehan

Data acquisitionProcessingInterpretasi

Drilling & Evaluation of oil shows & Geology

Evaluation of: well logs production tests, pressure data & Geological data

Mengenal prospek

Recovery

Konsep model reservoir, pengiraan oil/gas in place, cadangan telaga appraisal

Onshore drilling rigs Semi-submersible rigs Jack-up units

Conventional drilling Directional Drilling Slant Drilling

How do we extract oil?

Getting the Oil: Drilling Rigs

Types of Drilling: Rotary Drilling

• Drill bit berputar pd hujung drill string

Drilling A Well

Drilling A Well

PENILAIAN FORMASI

• Selepas digerudi, untuk mendapat informasi tentang formasi maka dilakukan pengukuran sifat geofizik dgn mengguna wireline logs.

• Parameter batuan boleh direkod, spt formation resistivity, sonic velocity, density, dan radioactivity.

• Data direkod boleh diinterpretasi untuk menentu litologi dan porosity formasi, dan jenis dan kuantiti bendalir (minyak, gas, atau air) dalam liang batuan.

SP Log – menentu litologi

Density log – ukur porosity

Sonic Log – ukur porosity

Resistivity Log – kandungan bendalir

Pembentukan Akumulasi Petroleum

1.Timbusan sumber bahan organik yang mencukupi. Petroleum terbentuk daripada organisma.

2.Timbusan pada kedalaman sesuai. Kedalaman 2-6 km dan suhu 60-160º C.

3.Kehadiran batuan reservoir berkualiti.A porous storage space. Sandstone and limestones are the most common reservoir rocks. To be a reservoir they must have: Porosity, to hold the hydrocarbons Permeability, to allow fluid flow

Pembentukan Akumulasi Petroleum

4. Presence of an adequate seal A seal is an impermeable bed (such as a shale or a

bed of salt) that sits on top of the trap and prevents the hydrocarbons rising any further.

5. Presence of a trap In order to prevent the hydrocarbons rising to the

surface and escaping they must be caught in a confined space, termed a trap. i.e. the source, reservoir and seal must be arranged in such a way that the petroleum is trapped.

Asalan Petroleum

Teori bukan organik– Sumber Cosmic: hc didapati dalam meteorit

• Consolidation of H and C during earth cooling.– Tindakbalas logam karbida dalam bumi:

• Diperkenal oleh Mendele’ve (1902) dan Porfir’ev (1974) – karbida besi bertindak dengan air untuk membentuk metana dan minyak hidrokarbon.

• There is little evidence for the existence of iron carbide in the mantle.

Asalan Petroleum

• Teori Organik• Terbentuk drp pengubahan bahan biologi.

• Asalan petroleum dr biogenik diterima secara meluas berdasar kajian geokimia.

• Pengendapan sedimen yang kaya bahan organik disokong dengan kadar pengeluaran bahan organik yang tinggi dan pengawetan yang baik.

• Terdapat dua keadaan untuk bahan organik diawet dengan baik: dalam keadaan anaerobic dan kadar pengedapan sedimen yang cepat.

Asalan Petroleum

Asalan Petroleum

• Contoh keadaan anaerobik (sekitaran anoxia).

Bagaimana Bahan Organik Menjadi Minyak?

• Terdapat 2 peringkat:

1.1. Pengubahan bahan organik (OM) ke kerogen.

•

• 2. Pengubahan Kerogen ke minyak dan gas

Pengubahan OM ke Kerogen

• Apabila bahan organik ditimbus, ia berubah drp komponen biologi kpd polymeric organic compounds dan seterusnya ke kerogen.

• What is kerogen? Insoluble in organic solvents Complex mixture of high molecular weight organic

materials• Kerogen is composed of varying proportions of C, H,

and O. General composition may be described as:

• (C12H12ON0.16)x

Pengubahan Kerogen ke minyak dan gas

KEROGEN

Diagenesis

Catagenesis

Metagenesis

Shallow subsurfaceNormal pressure and temperatureReleased: CH4, CO2, H2O• Overall decrease in O• Overall increase in H and C

Deeper subsurfaceIncreased pressure and temperatureReleased: oil & gas• Overall decrease in H and C

MetamorphismHigh temperature and pressure Only C remains: becomes graphite

Konsep ‘Oil Window’

• The principal zone of oil formation during the thermal generation of petroleum hydrocarbons

The Petroleum SystemThe Petroleum System

Maturation: no petroleum if the source rock OM does not matureMigration: no accumulation if the petroleum doesn’t migrate

Batuan Punca dan Perpindahan Petroleum

Kematangan (Maturation): no petroleum if the source rock OM does not mature

Perpindahan (Migration): no accumulation if the petroleum doesn’t migrate

The Source Rock

• This shale typically contains >1% of organic carbon, by weight. The shale is very widespread, and is by far the most important source rock for the oil that has been found in the Sea Basin.

Perpindahan Petroleum

• Oil (& gas) berpindah dari batu punca, menerusi lapisan penyalur dan berkumpul dalam batuan reservoir.

• Primary migration From source rock to “carrier bed”

• Secondary migration Through the carrier bed/ structure to the reservoir

Primary Migration

• Hypotheses 1. Migration of hc’s in clay compaction water 2. Migration by molecular solution in water Migration in micellar solution Migration in gas charged solution Migration via microfracturing of source rocks Diffusion along kerogen network

• Arguable that all of these processes are in operation

Secondary Migration

• Oil must be capable of continuous phase flow

• Availability of continuous pore spaces allows continuous flow

• Physical requirements for secondary migration are: 1. Adequate supply of hydrocarbons 2. Adequate continuous migration pathways 3. Adequate pressure gradient to drive

migration

Migration by Gas Flushing

• 2 fluids of different densities try to occupy the same trap

• Heaviest fluid is displaced as lighter one moves above it

• Different stages in the migration and accumulation of oil and gas in interconnected traps (after Gussow, 1968)