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8/13/2019 Geol 415 an Introduction 121
1/23
Geol 415
Petroleum GeologyGeology of Petroleum: An Overview
Lecture # 1
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Petroleum Geology
Introduction
Exploration for HC
Source Rocks
HC Generation & Maturation
HC Migration
Seal or cap rocks
Traps Reservoirs
Petroleum in Saudi Arabia
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Petroleum Geology
Petroleum geology comprises those
geological disciplines which are of greatest
significance for the findingand recoveryof
oil and gas
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6.HC GENERATION AND MATURATION
7. SOURCE ROCKS
5.PRIMARY HC MIGRATION
4.SECONDARY HC MIGRATION
3.SEAL OR CAP ROCK
2.TRAP
1.RESERVOIR
Seven important factors in forming petroleum accumulation
Data
LogicalOrd
er
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Geological Map of Saudi Arabia
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Stratigraphic cross-section across the Arabian shelf
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HC Exploration: Geophysical Seismic Survey
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Wire line log correlation of Arab Formation offshore Abu Dhabi
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Evolution of Exploration Concepts & Techniques
New advances in exploration technology is remote sensing from satellite
from surface geochemical & geophysical methods, and identification of
gas micro seepsand electrical conductivity of rocks above oil
accumulation
Petroleumis attributed to two origins: inorganic and organic.
Chemists and astronomers argued for an organic originsometime
igneous, sometimes extraterrestrial, or a mixture of both
Most petroleum geologists believe that petroleum forms fromthe
diagenesis of buried organic matter, note that it is indigenous to
sedimentary rocks rather than igneous one
Chemical analytical techniquesallowed petroleum source rocksto be
studied and identify potential source, tendency to generate oil or gas
and their level of thermal maturation
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Evolution of Exploration Concepts & Techniques
Commercial oil accumulation requires five
conditions:
1. Organic rich source rocksto generate the oil and/or gas
2. The source rocks must have been heated sufficientlyto yield
petroleum
3. There must be reservoir, porous to contain the HCand
permeable to permit fluid flow
4. The reservoir must be sealed by an impermeablecap rock to prevent the upward escape of petroleum to the earths surface
5. Source, reservoir, and sealmust be arranged in such a way as to trap
the petroleum
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Qusaiba Formation: Main Organicrich Source Rock
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Sandstone & shale sequences
Source Generation Migration Trap/Seal Reservoir
shale
sandstone
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Petroleum ExplorationReservoir
Trap
Seal or Cap Rock
Secondary Migration
Primary Migration
Hydrocarbon
Generation
And Maturation
Source
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Relationship of Petroleum Geology to Science
1. Petroleum geology is the application of geology to the exploration and production of oil and gas
2. Geology itself is firmly based on chemistry, physics, and biology and involves
the application of essentially abstract concepts to observed data (Fig 3).
3. The application of chemistry to the study of rocks ( geochemistry) has many
uses in petroleum geology
4. Detailed knowledge of the mineralogical compositionof rocks is important at many levels
5. Mineralogy of reservoir enables estimates to be made of the rate at which
they may los porosity during burial
6. Mineralogy is essential for accurate interpretation of geophysical well logs
through reservoirs
7. Chemistryof pore fluids and their effect on the stability of minerals can be used to predict porosity
8. Organic chemistry used in analysis of oil and gas study of diagenesis of plant
and animals tissues in sediment and the way in which the resultant organic
compound, kerogen, generates petroleum.
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The relationship of petroleum geology to the pure sciences
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Relationship of Petroleum Geology to Science
1. The application of physics to the study of rocks(geophysics) is
very important in petroleum geology
2. Geophysics makes a major contribution to understanding of the
earth's crust (plate tectonics) to the genesis and petroleumpotential
of sedimentary basins
3. Physical concepts are required to understand folds, faults, and
diapirs, and their role in oil entrapment
4. Magnetic, gravity and seismicsurveys are powerful in finding potential petroleum traps
5. Wireline well logs are effective toolin evaluating any finds interms of
lithology, porosity and petroleumcontent of a reservoir
Relationship of Biolog to Petrole m Geolog
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Relationship of Biology to Petroleum Geology
1. Biology is applied though the study of fossil, establishing
biostratigraphic zonesand regional stratigraphical correlation
2. Study of relationship between organisms and their environments
(ecology)is also important in petroleum geology
3. Carbonate sediments and reefs in particular can only be studied
with the aid of detailed knowledge of the ecology of modern faunaand flora
4. Biochemistryis important in studying the transformation of plant and
animals tissues into kerogen during burial and the generation of oil
and gas
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Petroleum geology & Petroleum Exploration and Production
1. Petroleum geologyis only one aspects of petroleum exploration
and production
2. Petroleum explorationnow involves integrated teams of people
3. The teams posses a wide range of professional skills(Fig 1.4)
4. These skills include political & social skills expertise which
involved in acquisition of prospective acreage
5. Geophysical surveyingis involved in preparing the initial data
on which leasing and, later, drilling recommendations are base
6. Geological conceptsare applied to the interpretation of the
geophysical dataone they have been acquired and processed
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Fig 1.4. Petroleum geology is part of a continuum of displine employed in exploration &
production of oil & gas. Geophysics now extends beyond the beginning of production.
Repeated seismic surveys can monitor the migration of fluid interfaces within fieldsduring their productive lifetime (4 D seismic)
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Petroleum geology & Petroleum Exploration and Production
7.Once an oil well has been drilled, the engineering aspects ofthe discovery need appraisal
8.Petroleum engineering is concerned with establishing the
reservesof a field, the distribution of petroleum within the
reservoir, and the most effective way of producingit
9. Petroleum geology lies within a continuum of disciplines,
beginning with geophysics and ending with petroleum
engineering
10. These disciplines overlap both in time and subject matter
(Fig 1.5)
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Fig 1.5 Flow chart showing how petroleum geology is only one aspect of
petroleum exploration & production, and how these enterprises themselves
are part of a continuum of events subjected to various constraints andexpedited by many disciplines
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Petroleum geology & Petroleum Exploration and Production
10. Underlying this sequence of events (Fig 1.5) is the control
of economics
11. Every stage from leasing to drilling, to productionand
enhanced recoveryis monitored by accountants and
economist.
12. Activities in petroleum exploration and production
accelerates and decelerates when oil prices increase or
decrease.