Petroleum Geoscience and Geophysics Chapter 1

7/24/2019 Petroleum Geoscience and Geophysics Chapter 1

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MKPP 1213

APPLIED GEOSCIENCE &GEOPHYSICS

LECTURER: PROF. DR. RADZUAN JUNIN


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MKPP 1213

CHAPTER 1

INTRODUCTION


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Introduction

What isApplied Geoscience & Geophysics orPetroleum Geoscience?

The disciplines of geology and geophysicsapplied to understanding the originand

distribution, andpropertiesof petroleum and

petroleum-bearing rocks.

Theimportanceof petroleum geoscience is tofind petroleum (petroleum province) andhelp

produce it.


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Basic Geological Principles

To become a petroleum province, fiveingredientsor elements are involved;

the source,Seal (cap rock),

reservoir, and overburden rock

trap formation, and

timing of petroleum migration (Generationmigrationaccumulation of hydrocarbons).

These elements Petro leum system


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A petroleum system contains a pod of active

source rockand all genetically related oil and

gas accumulations. It includes all the geologic elements and

processesthat are essential if an oil and gas

accumulation is to exist.

Practical application of petroleum systems can

be used in exploration, resource evaluation, and

research.


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(Foreland Basin Example)

Overburden Rock

Seal Rock

Reservoir Rock

Source Rock

Underburden Rock

Basement Rock

Top Oil Window

Top Gas Window

Geographic Extent of Petroleum System

Petroleum Reservoir (O)

Fold-and-Thrust Belt

(arrows indicate relative fault motion)

Essential

Elements

of

Petroleum

System

O O

Sedimentary

B

asinFill

OStratigraphic

Extent ofPetroleum

System

Pod of Active

Source Rock

Extent of Prospect/FieldExtent of Play

Cross Section Of A Petroleum System


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The source:

Asource rock is a

sedimentary rock thatcontains sufficient

organic matter, when it is

buried and heated it will

produce petroleum. Good examples: shale

and claystone/mudstone.


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High concentrations of organic matter tend to

occur insedimentsthat accumulate in areas

of high organic matter productivity and

stagnant water. To preserveorganic matter, the oxygen

contents of the bottom waters and interstitial

waters of the sediment need to be very low

or zero, and a rapid sedimentation rate.


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The Seal:

Seals tend to be fine-grained

or crystalline, low-permeability

rocks. Typical examples

include mudstone/shale,

cemented limestones, cherts,

anhydrite, and salt (halite).


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Seals to fluid flow can also develop along fault

planes, faulted zones, andfractures.

The presence of a seal or seals is critical forthe development of accumulations of

petroleum in the subsurface.


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The Trap:

The geometryof the sealed petroleum-bearing

container.

The simplest trapping configurations are domes(four-way dip-closed anticlines) and faultblocks.

The mapping and remapping of trap geometry is

a fundamental part of petroleum geoscience.


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The Reservoir:

The rock plus void space

contained in a trap.

The petroleumtogether withsome wateroccurs in the pore

spaces between the grains (or

crystals) in the rock.

Reservoir rocks are most

commonly coarse-grained

sandstonesor carbonates..


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Porous rock and porosity:

Porosityis the void spacein the rock, reported

either as a fractionof one or as a percentage.

Most reservoirs contain >0% to


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The timing of petroleum migration:

The timing of petroleum migration relative to the

time of deposition of the reservoir/seal

combinations and the creation of structure withinthe basin.

In order to determine whether the reservoir,

seal, and trap are available to arrest migrating

petroleum, it is necessary to reconstruct the

geologic historyof the area under investigation.


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Petroleum Systems

Petroleum System Investigation:

Identifies,

names,

determines the level of certainty, and

maps the geographic, stratigraphic, and

temporal extent of a petroleum system.


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Petroleum Systems

To identifya petroleum system, the

explorationist must find some petroleum.

Any quantity of petroleum, is proof of a

petroleum system. An oil or gas seep, a show of oil or gas in a

well, or an oil or gas accumulation

demonstrates the presence of a petroleum

system.


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Petroleum Systems

The nameof a petroleum system contains

several parts that name the hydrocarbon fluid

system:

1. The source rock in the pod of active sourcerock

2. The name of the reservoir rock that contains

the largest volume of in-place petroleum

3. The symbol expressing the level of certainty.


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Petroleum Systems

A petroleum system has three important

temporal aspects:

1.Age- the time required for the process of

generation

migration

accumulation of hydrocarbons 2. Critical moment - the time that best depicts the

generationmigrationaccumulation of hydrocarbons in

a petroleum system.

3. Preservation time - begins immediately after thegenerationmigrationaccumulation process occurs

and extends to the present day.


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Prudhoe Bay: Event Timing Favors

Accumulation of Shublik Oil and Gas


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Timing of formation of the major elements of apetroleum system, Maracaibo basin, Venezuela.

From Schlumberger Oilfield Glossary


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Timescales: Petroleum maturation, migrationand trappingof

oil can occur in a few million years.

Geologic timeis divided, using a hierarchicalscheme, into a variety of named units.

The basic unit in this scheme is the period.

The sequence of periods with their attendant

subdivisions and supra-divisions makes up thestratigraphic column.


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The Geologic Timescale

The geologic timescale - a calendar of Earthhistory.

The largest defined unit of time shown on thegeologic timescale is the supereon, composed

of eons. Eon - the greatest expanse of time.

The earliest is the Hadean (beneath the Earth)Eon, ranging from 4.6 to 3.8 billion yrs ago.

The earliest-known life forms appear in rock fromtheArchean (ancient) Eon, about 3.8 to 2.5billion yrs ago.


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Generalized Stratigraphy of Malay Basin


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TheArchean Eon gave way to the Proterozoic(early life) Eon (2,500-543 mya).

The beginning of the Phanerozoic (visible life)Eon, 543 mil years ago, marks the first point at

which we find abundant fossil evidence. Phanerozoic subdivided into threeeras: the

Paleozoic (543-252 mya) , Mesozoic (252-65mya) , and Cenozoic (65 mya-present day) .

The first part of the Paleozoic (ancient life) Erawas dominated by marine invertebrates, suchas corals, clams, trilobites, and later fish andamphibians.


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TheMesozoic (middle life) Era was dominatedby marines and terrestrial reptiles, including thedinosaurs.

TheCenozoic (recent life) Era, which continues

today, is distinguished by its rich variety ofmammals.

Eras are subdivided intoperiods.

Periods are subdivided intoepochs.


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Plate Tectonic Context of

Petroleum Basins

Basinsare generated by plate tectonics, the

process responsible for continental drift.

The Earth's crust is made up of about 20 rigid

plates.

Plates may be stretched and broken or pushed

together, or may rotate past each other. Each of

these processes

divergence(extension),convergence(compression), and strike-slip(or

wrench)can lead to the formation of basins.


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Continental Drift

The idea that continents,particularly South America and

Africa, fit together like pieces ofa jigsaw puzzle.

However, little significance wasgiven this idea untilAlfredWegener(1915) proposed acontroversial hypothesis ofcontinental drift.


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Continental Drift

Wegener suggested that thecontinents floaton a denserunderlying interior andperiodicallybreak up and drift

apart. Today the concepts of seafloor

spreadingand plate tectonicsare firmly established.


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Petroleum Basins


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Seafloor Spreading

The rates of spreading(frommid-ocean ridges) on either siderange from 1 to 6 cm/year ortotal rate from 2 to 12cm/year.

At this rate it would have takenabout 200 millionyears for thepresent Atlantic Ocean to attainits present width.

An interesting feature about themid-ocean spreading ridges isthat they are sites for bothvolcanic and earthquakeactivities.


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Plate Tectonics

In the 1960s, an exciting new hypothesiscalled plate tectonicsrevolutionized ourunderstanding on how the outer portion ofthe Earth functions.

According to this theory, the uppermostmantle, along with the overlying crust,behave as a strong, rigid layer, known asthe lithosphere, which is broken intopieces called plates and their movementasplate tectonics.


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Plate Tectonics


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Plate Tectonics Context of

Petroleum Basins

The lithosphere(rigid plate) overlies a weakerregion in the mantle known as theasthenosphere.


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Petroleum Basins

Plate Boundaries: there are three basic typesof plate boundaries or margins.

Divergentplate boundaries

Convergentplate boundaries

Transformplate boundaries


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Plate Tectonics

Where two plates converge, they produce anarrow, deep depressionas the subductingplate bends downward into the mantle. Suchdepressions are calledoceanic trenches.


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Petroleum Geoscience and Geophysics Chapter 1

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