1 earths structure

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Petroleum Geology (Distance Delivery)

Understanding Earths Structure


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This publication The Northern Alberta Institute of Technology 2006. All rights are reserved. No part ofthis publication may be reproduced, or transmitted in any form or by any means, or stored in a database

and retrieval system, without the prior written permission of the copyright holder.

Address all inquiries to:

THENORTHERNALBERTAINSTITUTEOFTECHNOLOGY11762 106 Street, Edmonton, Alberta, Canada T5G 2R1Attention: Rick Wilson, Petroleum Engineering Technology

Basic Computer knowledge. Ability to navigate the internet.

TEXTBOOK: Basic Petroleum Geology by Peter K. LinkAvailable at NAITs Campus Reads and Needs bookstore

Or from:Petroskills website (http://www.petroskills.com/prodserv_main.asp)Follow the links: Products and Services/Technical Publications/

Must have access to internet and printer.


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Learning Outcome Guide

Upon successful completion of this Learning Outcome Guide, you will be able todescribe how earths processes determine the formation of reservoirs.

Learning Objectives

To successfully complete the Learning Outcome Guide, you should be able to:

Describe the structure of the earth using a cross section. Relate plate tectonics and continental margins to common geological events and

familiar geologic features.

describe and explain how the rock cycle relates to the main types of rocks (igneous,metamorphic and sedimentary).


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If you live on the prairies of Western Canada, the countryside tends to be relatively flatwith only rivers and creeks interrupting the continuity. If you dig a hole in your backyard,you would encounter dirt, clay, gravel and rocks. You would probably get very tiredbefore you hit solid bedrock. We live on top of glacial deposits which are a thin layer(relatively) of sediments deposited by glaciers during the last ice age. Underneath allthis dirt and gravel and clay lies solid rock. A lot of that solid rock is made from oldersediments that have lithified (turned to rock) to become sedimentary rock. We tend todirect our hydrocarbon exploration to sedimentary rock as it has the best chance ofpossessing the features required to produce and hold hydrocarbons.

Under the sedimentary rock lies metamorphic rock with characteristics found in theCanadian Shield. In fact, the Canadian Shield is ancient rock that is exposed at surfacein places like Northern Saskatchewan, Manitoba, Northern Ontario and Quebec.

Look at the map above showing the location of exposed Canadian Shield. This is notgood hydrocarbon rock. Draw a line from the USA border up into the North showing thelocation of the Rocky Mountains. The mountains are also fairly poor hydrocarbonlocations because the sedimentary rock tends to be uplifted and exposed. Look at the

region between the mountains and the shield. This is prime geology for findinghydrocarbons.

Understanding the structure of the earth, how that structure changes and movesprovides a basis for understanding geology and hydrocarbon resource locations.


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OBJECTIVE ONETo successfully complete this Learning Outcome Guide, you should be able to describethe structure of the earth using a cross section.

Read pages 1-6 of Basic Petroleum Geology textbook. Focus on section "Structure ofthe Earth"

Reading a textbook can be difficult. Let the questions in the experiential activity(immediately following) guide your reading. Look at the question and then searchthrough the readings to find the answer.

1. Draw a cross section of the earth from the Asthenosphere to surface. Show how acontinental crust and undersea crust differ from each other.

3. What is the density of rock in the crust compared to the density of the entire earth?How do we account for this difference?

4. What is the typical temperature gradient of the earth's crust (in metric units)?


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OBJECTIVE TWOTo successfully complete this Learning Outcome Guide, you should be able to relateplate tectonics and continental margins to common geological events and familiargeologic features.

Read pages 6 to 16 (section called Plate Tectonics) of Basic Petroleum Geologytextbook.

Google Plate Boundaries to find additional information to help with theexperiential activity.

1. Who originated the plate tectonic or continental drift theory?

2. Give two factors which geologists point to as evidence that continents were onceconnected.

3. Draw a sketch of a divergent plate boundary and name a location where such aboundary can be found today.


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4. Draw a sketch of a convergent plate boundary and name a location where such aboundary can be found today.

5. Oil fields can be found near plate boundaries. Use the textbook to find 2examples each of fields found at divergent, convergent and transform plateboundaries.


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OBJECTIVE THREETo successfully complete this Learning Outcome Guide, you should be able to describeand explain how the rock cycle relates to the main types of rocks (igneous,metamorphic and sedimentary).

Read pages 53 to 59 and 69 to 76 in the Basic Petroleum Geology text.

Definitions:

Mineral: a naturally occurring inorganic crystalline element or compound. It has adefinite chemical composition and characteristic physical properties such ascrystal shape, melting point, colour and hardness. Most minerals found in rocks

are not pure.

Rock: a hardened collection of different minerals. Rocks are divided into threegroups on the basis of their mode of origin: igneous, metamorphic andsedimentary.

Think of a mineral as a pure compound or element while a rock is made up of minerals.

- Quartz is a mineral (SiO2) but it is uncommon to find a pure, clear quartz crystal.You would often find it with a collection of other minerals in something like asandstone.

- In both cases (sandstone or quartz) you would be looking at a rock. In only one

case (pure quartz), you would be looking at a mineral.


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1. Draw a simple diagram showing how the different types of rocks relate to therock cycle (see page 76).

2. Explain how a metamorphic rock and an igneous rock is formed.


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Google "Earthquakes Canada" to find the Natural Resources Canada website. Explorethis website and links to get an understanding of regions in Canada that have atendency to experience earthquakes.

Assignment:

Print out a PDF map of Canadian earthquakes (find it by following the link to HistoricEarthquakes). Use this map to discuss plate tectonics in Western Canada, plateboundaries in relation to the Rocky Mountains and plate tectonics in relation to Alberta,where most of Canadas oil and gas is found.

This discussion is to be approximately one page long and attached to the map of

Canadian Earthquakes.

The relationship between plate tectonics and hydrocarbon reservoirs is not immediately apparent. What is key (from abig picture perspective) in finding hydrocarbons, is finding the type of rock that has porosity and permeability tocontain hydrocarbons. Sedimentary rock provides this. Sedimentary rock is found in areas where there was oncewater (inland oceans, continental boundaries, rivers, deltas etc.)Plate tectonics is important in that the constantly shifting plates are continuously changing the shape of the continentsand subsequently, the places where sediments (and sedimentary rocks) are deposited. Places where there areprairies or deserts may have once been seas.

Dont be misled by this earthquake assignment. Earthquakes are an indicator of shifting plate boundaries and plateboundaries are not necessarily good places to find reservoirs. Often the underlying rock has been fractured anduplifted, exposing any hydrocarbons to a free path to the atmosphere.

Butknowing where the plate boundaries are can lead to an understanding of places where the earth's structure hasbeen deformed. This is a good place to find structural traps for hydrocarbons (such as the foothills of Alberta).Sedimentary rock in Alberta and the Western Canada Sedimentary Basin (WCSB) was formed because an inlandsea existed there. Later, when the Rockies were formed from plate movement, many meters of sand, gravel, pebbles,mud and clay were deposited from the erosion of the fresh mountains. This formed a thick layer of sedimentary rockduring the Cretaceous period.

Plate movement, sedimentary basins, sedimentary rock, sediments and hydrocarbon development all work in aunified cycle.

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