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PENGENALAN GEOLOGI PETROLEUM (E0005). PENGENALAN. Kandungan Kursus :
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PENGENALAN GEOLOGI PETROLEUM (E0005)
PENGENALAN • KandunganKursus: 1. Pengenalankepadageologi petroleum; sejaraheksplorasi, sifatkimiadanfizik, kaedaheksplorasi, akumulasi, asalmuladanperpindahan, perangkapdan reservoir petroleum (termasukkonseprezabdansumber).
PENGENALAN 2. Rujukan: • Selly, R.C. Elements of Petroleum Geology
PENGENALAN • Apakah ‘petroleum’?: • Berasaldrpperkataan Greek bermaksud ‘rock oil’ atauminyakbatuan. • Bolehdidefinasisebagaibahanterbentuksecarasemulajadi, nonrenewable fossil fuel, terutamanyaterdiridaripadacampuranhidrokarbondalambentukfasa gas, cecairdanpepejal.
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
Gas Solid; Asphalts, Coals, Kerogen Cecair; Oil, Crude Wet ethane, propane Dry methane Sifat Fizik & Kimia Minyak dan gas Hidrokarbon: terdiri drp H dan C
ORGANIC ORIGIN INORGANIC ORIGIN Hydrocarbon Gases Methane (dry) Ethane (wet) Propane Butane Inert Gases Helium Argon Krypton Radon Nitrogen Also Carbon dioxide Hydrogen sulphide Gas Asli Cecair (NGL) Dikelaskan kpd:
Sifat Kimia Petroleum • Komponen utama hidrokarbon dibahagi kepada 2 siri: • Siri Parafin atau n-alkana (hc tepu) • 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
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
Aromatik • 3. Aromatik; sebatiangegelangtaktepu • Berdasarkpdrantaigegelangbenzena 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
141.5 - 131.5 °API = SG 60/60°F Sifat Fizik Petroleum • Warna: kuning, hijau, coklathinggacoklatgelap & hitam • Kelikatan: Pelbagai, dipermukaanbumiminyakmenjadilebihlikat. • Ketumpatan: Kebanyakanminyaklebihringandrp air. Biasanyadiukursebagaiperbezaanantaraketumpatanbandingannya (SG) denganketumpatanbandingan air: • Minyakringanmempunyai API > 40° danminyakberatmemp. API graviti < 10° (SG=1)
How do we extract oil? • Onshore drilling rigs • Semi-submersible rigs • Jack-up units • Conventional drilling • Directional Drilling • Slant Drilling
Types of Drilling: Rotary Drilling • Drill bit berputar pd hujung drill string
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.
Pembentukan Akumulasi Petroleum • Timbusansumberbahanorganik yang mencukupi. • Petroleum terbentukdaripadaorganisma. • Timbusanpadakedalamansesuai. • Kedalaman 2-6 km dansuhu 60-160º C. • Kehadiranbatuan 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 • Teoribukanorganik • Sumber Cosmic: hcdidapatidalammeteorit • Consolidation of H and C during earth cooling. • Tindakbalaslogamkarbidadalambumi: • DiperkenalolehMendele’ve (1902) danPorfir’ev (1974) – karbidabesibertindakdengan air untukmembentukmetanadanminyakhidrokarbon. • There is little evidence for the existence of iron carbide in the mantle.
Asalan Petroleum • TeoriOrganik • Terbentukdrppengubahanbahanbiologi. • Asalan petroleum drbiogenikditerimasecarameluasberdasarkajiangeokimia. • Pengendapansedimen yang kayabahanorganikdisokongdengankadarpengeluaranbahanorganik yang tinggidanpengawetan yang baik. • Terdapatduakeadaanuntukbahanorganikdiawetdenganbaik: dalamkeadaananaerobic dankadarpengedapansedimen yang cepat.
Asalan Petroleum • Contoh keadaan anaerobik (sekitaran anoxia).
Bagaimana Bahan Organik Menjadi Minyak? • Terdapat 2 peringkat: • 1. Pengubahanbahanorganik (OM) kekerogen. • 2. PengubahanKerogenkeminyakdan gas
Pengubahan OM ke Kerogen • Apabilabahanorganikditimbus, iaberubahdrpkomponenbiologikpd polymeric organic compounds danseterusnyakekerogen. • 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 • Shallow subsurface • Normal pressure and temperature • Released: CH4, CO2, H2O • Overall decrease in O • Overall increase in H and C Diagenesis • Deeper subsurface • Increased pressure and temperature • Released: oil & gas • Overall decrease in H and C Catagenesis Metamorphism High temperature and pressure Only C remains: becomes graphite Metagenesis
Konsep ‘Oil Window’ • The principal zone of oil formation during the thermal generation of petroleum hydrocarbons
Maturation: no petroleum if the source rock OM does not mature • Migration: 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)