Ch. 11
Energy from the Oceans
(pgs. 182 – 196)
Introduction:
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Although energy comes in different forms, the fossil fuels of coal and petroleum are the
dominant sources of energy today.
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Today petroleum is valued as a fuel because:
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2.
3.
4.
It produces large amounts of heat and power per unit of mass.
It is relatively easy to store.
It is convenient as a source of energy for transportation.
It is a raw material that can be processed into refined products (such as gasoline)
and chemicals (such as fertilizers).
Characteristics of oil that determine its quality:
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Viscosity: resistance to flow.
High Viscosity: when the oil is thick and slow flowing.
Low Viscosity: oil that is thin and fast flowing.
Oil Quality and Cost of Production:
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Higher viscose oil requires more energy to extract and process.
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This petroleum resource is used to produce asphalt, fuel for ships, etc.
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Therefore the return on investment is not as high when compared to low viscosity oil
extraction.
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Low viscose oil requires less energy to extract and process, and is more economically
lucrative because it is processed for use in automobiles, home heating, etc.
How Oil Reserves Form:
(obj. 4.51)

Approximately 250 million years ago Pangaea began to break up due to continental
drifting and large ocean basins were formed.
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Ancient rivers and streams carrying sediment (sand, mud and organic matter) drained into
the ocean basins depositing the sediment for many kilometers.
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The organic matter from the rivers, streams and ocean settled to the bottom of the ocean
and became covered with sediment.
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This process continued for millions of years, eventually forming the continental shelves
(layers of sediment containing organic matter in varying amounts).
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The organic material in the sediment, under extreme pressure from the weight of the
sediment, combined with increased temperature, and bacterial action is transformed into
oil and gas.
Oil and Gas Traps:
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Due to convergent and divergent forces these horizontal layers of sediment become bent
and buckled forming faults, anticlines, etc.
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Under this pressure the source rock is squeezed releasing the oil and gas into a porous,
permeable layer allowing the oil and gas to flow sideways along the layers until they
become trapped in rock (geological) formations such as anticlines and faults.

The geological structures that are created can become OIL TRAPS when certain
conditions are present:
1. There must be a source rock in the area. SOURCE ROCK is the fine grained
rock in which the organic material was originally present and was converted into
hydrocarbons (oil and gas).
2. There must be a porous and permeable rock layer to provide a reservoir in which
the hydrocarbons can accumulate (such as shale and sandstone)
3. There must be an impermeable sealing or cap rock layer above the reservoir rock
to trap the hydrocarbons.
Types:
(Refer to diagrams on page 183)
1. Fold Trap:
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Natural gas and oil, having less mass than water, float to the top of the fold in the
layer of sandstone.
Natural gas and oil are unable to continue their upward movement because they
cannot go through the impervious shale layer.
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2. Fault Trap:
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Oil and natural gas form in the impervious shale layer (source rock).
The oil and natural gas migrate upward in a layer of porous sandstone (reservoir
rock) above the source rock.
A fault develops, cutting off the sandstone layer and tilting it on an angle.
A porous layer is blocked by impervious shale (cap rock).
The oil and natural gas are trapped.
3. Salt Dome Trap:
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Oil and natural gas form in the impervious shale layer (source rock).
Oil and natural gas migrate upward in a layer of porous sandstone (reservoir
rock).
A salt dome develops, cutting through the porous layers.
The salt dome deflects the layers upward.
The oil and natural gas are trapped in pockets between the salt dome and the
impervious shale layers (cap rock).
4. Stratigraphic Trap:
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A coral reef develops.
The reef becomes buried in layers of sediment.
Oil and natural gas form in the source rock.
Oil and natural gas migrate upward in the ancient reef (reservoir rock).
Impervious layers of shale (cap rock) prevent the oil and natural gas from moving
any farther up.
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IMPERVIOUS means fluid does not flow through.
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NON-POROUS means fluids are not held in the pores of the layer
Techniques used to locate Oil and Gas Reserves in the Offshore: (obj. 4.5.2)
1. Gravity and Magnetic Surveys:
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A type of reconnaissance survey done from ships to find sedimentary basins in
offshore areas.
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A reconnaissance survey is undertaken to define broad areas of interest that have
the potential to contain hydrocarbon traps.
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By taking magnetic measurements throughout an area an estimate of the
geological structure of the basement and sedimentary rocks can be determined.
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2. Seismic Surveys:
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The most common technique used to obtain detailed geological structural
information.
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Involves sending shockwaves down through the water and recording the echoes
that bounce back off the various sedimentary layers tens of kilometers below the
surface.
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Hydrophones (underwater microphones), attached to a floating cable, are towed
behind a ship and record the echoes which are transmitted to the ships computer.
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Three dimensional images are produced to identify hydrocarbon traps.
After the geologists have identified the likely locations of oil traps, they drill exploratory
wells (WILDCAT WELLS) to confirm the oil - trap locations and to determine the
quantity and quality of the oil.
The Search for Oil in the Sea:
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Ocean depth influences the design of drilling platforms.
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For reasonably shallow depths (about 20m), the SUBMERSIBLE has chambers that can
be flooded so that it can rest on the ocean floor.
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On its long legs the JACK-UP rig can also sit on the ocean floor, but only in depths of up
to 100m.
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In deeper water, floating platforms can be used. The ANCHORED SEMISUBMERSIBLE can withstand heavy seas because part of it remains underwater.
Because it requires anchors, it can be used only in depths up to about 200m.
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In very deep water, only the DYNAMICALLY POSITIONED SEMISUBMERSIBLE is practical, as it can be positioned to help withstand heavy seas.
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Elements of an off-shore oil recovery operation:
a. Exploration: Using seismic technology oil traps are identified. Semi-submersive
platforms are then used to confirm the presence of oil by drilling wild cat
drills.
b. Development: Once the location of the oil is confirmed an oil platform needs to be
developed. The oil company must consider the physical and climatic
environment when making this decision. Once constructed the platform is
towed into place.
c. Extraction: Oil from the reservoirs is extracted, processed onsite (topside facilities of the
platform) and stored (for example in the caisson of Hibernia).
d. Transportation: The oil is offloaded from the platform onto shuttle tankers using risers
(flexible pipe). From there the oil travels to a trans-shipment terminal, is
stored in large tanks before it shipped by smaller tankers to markets in
Canada, Western Europe and the eastern U.S.
How Directional Drilling saves cost in offshore oil production:
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Fig. 11.5 shows a directional drilling rig.
A significant part of the cost of extracting offshore oil involves the drilling platform.
An oil company would prefer to have as few rigs as possible involved in a project.
Directional drilling allow a platform to tap into several fields at once, thereby eliminating
the need for one drill rig per field or moving drill rigs frequently.
Directional drilling reduces costs significantly.
Risks Associated with Off-Shore Oil and Gas Operations: (obj. 4.3.1 and 4.3.2)
a. Environmental Risks:
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Wildlife habitat along coastline
Marine habitat
b. Human Risks:
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Working in extreme conditions
Loss of life - Ocean Ranger
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c. Economic Risks:
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There are several economic risks associated with off-shore oil and gas operation that
effect the following:
1. Oil Company:
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Loss of revenue due to climatic conditions - oil cannot be extracted or
transported from the platform.
Loss of revenue due to loss of tanker or platform, environmental clean-up.
Cost of environmental disaster in the off-shore.
2. Governments:
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Cost of environmental disaster in the off-shore.
Loss of royalties due to limited extraction.
3. Fishing Industry:
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Loss of livelihood due to environmental disaster.
Areas of high risk in the recovery of oil and gas:
A. Climatic Influences:
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Extreme range of temperatures
High winds/waves
Icebergs
Hurricanes
B. Physical Geography Influences:
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Water depth
C. Political Influences:
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An example would be the Persian Gulf
How trends in world oil and gas prices and government policies influence investor
decisions to commence production?
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Factors that influence investor decisions to commence production of oil and
gas:
1. Supply and demand for oil world wide (a positive situation would be an increase in the
price of oil per barrel and a dwindling supply of oil world wide).
2. The cost of exploration.
3. The cost of development of the oil field.
4. The policies outlined by governments, both federally and provincially, that can influence
the price per barrel. For example provincial royalties or insisting that the oil has to be
processed in the province.
5. If the cost of exploration, development, production, and royalties are less than the
projected value of the oil and gas to be recovered (by a sufficient amount) the investors
will commence production.
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