Transcript 4.3systems model and offshore oil

Unit 4: Primary Resources
World Geo 3200/3202
February 2011
4.3: Demonstrate an application of the systems
model to offshore oil recovery, including the following
delineations:
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 4.3.1 Identify physical factors that influence the decision to
recover offshore oil and gas. (k)
 4.3.2 Identify human factors that influence the decision to
recover offshore oil and gas. (k)
The systems model is useful in helping determine
the viability of an oil reserve.

The determination must be made whether cost of
inputs and processing will be offset by the value of
the out-put oil.
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This lesson looks at the physical and human factors
that influence the decision to recover oil and gas from
an off-shore reserve.

Ocean related factors include; 1) Ocean Depth 2)
Ocean currents 3) Icebergs & pack ice
 Climate/weather related factors include; 1) Wind
speeds 2) Storms
 Oil Related factors include; 1) size of the reserve 2)
Oil quality
 Environmental protection factors; How do these
other physical factors affect the chances of an oil
spill? Other resources like fish stocks, marine
mammals, and spawning grounds would be affected
in the event of an oil spill.

Worker Safety; How safe can the drill rig and
production platform be for the workers?
 Financial Factors include:

 cost of inputs like building a rig to withstand icebergs, building a
rig to drill at great depths or building a production platform that
can withstand hurricane winds;
 cost of processes like transporting the oil from off-shore to land,
maintaining the platform's equipment, and pressurizing the
reserve
 price of oil which is set by world markets and determines if
enough money is recovered from the oil to exceed the cost of
production.
The decision whether to drill or not often comes
down to the question: will the cost of overcoming the
all other factors be offset by the price oil can be sold
for and make the venture financially viable?

The topics covered in this lesson are spread
throughout chapter 11 in your book. Therefore a quick
read through pages 182-196.


Developing Hibernia case study
1. Millions of years ago plants and animals of the
oceans died & settled on the ocean floor.
2. Sediments piled up and pressed the remains into
layers of sedimentary rock.
3. This caused extreme pressure, heat, and bacterial
action.
4. These natural processes then converted the
organic material into oil and gas over a long period
of time.

Oil reserves form when non-porous rock (won’t let
water through) lies above porous rock ( lets water
through). Oil seeps up through the porous rock and is
trapped by non-porous rock.

Figure 11.1 in our book shows 4 types of oil
reserves.

You will notice that all four have a nonporous rock cap and a porous
rock source.
The porous rock allows the oil to seep into the cavity and the
nonporous rock prevents the oil from leaving.


the up fold or anticline in the layers of the earth's crust form the
reservoir.

the vertical movement of the earth's crust forms
a v-shaped reservoir.

The salt dome forms an up-fold in the earth's
crust not unlike the anticline caused by tectonic
forces

has a former limestone reef as its porous rock
feeding the reservoir.
Before 1900’s
Search was limited to the search for oil seeping to the surface along
fault lines.

After 1900’s
Geologists knew to drill in gentle anticlines or faulted sedimentary
rock where reservoirs of oil might occur.

Modern oil exploration on the seas
1.
Ships tow sound emitters and
hydrophones. Different rock layers
reflect sound differently.
2.
Computers convert the sound data
into 3D pictures of the ocean’s rock
layers
3.
“Wild cat” wells are drilled to test for
oil. If they….
* strike oil > drill delineating wells
* miss oil > examine core samples
for evidence

Oil quality varies with viscosity
 Heavy, viscous (thick slow running) oil is used for asphalt and
electric generating stations
 Light less viscous oil is easier and cheaper to refine. It is used for
gasoline, jet fuel, and petroleum products.

Refer to Fig 11.2 in your text (Also shown on
previous slide)
 Most oil regions of the world are located on-land.
 The ones that are located under the ocean floor are
concentrated in the North Sea around the United Kingdom and
in the Gulf of Mexico.
Figure 11.3 (on previous slide) show the oil
production by non- OPEC countries.

North Sea and Gulf of Mexico are regions of high
offshore oil production.

Offshore oil production is increasing faster than
land production of oil.

West Africa, around the Ivory Coast seem to have
high oil reserves and is also increasing in
production.


Physical Factors
 Ocean Related Factors which include; 1.Ocean Depth, 2.Ocean
Currents, 3.Icebergs and 4.Pack Ice.
 Climate/Weather Factors including; 1.Wind Speeds, 2.Storms.
 Oil Related Factors including; 1.Size of Reserve, 2.Oil Quality.
 Environmental Protection Factors 1.How does the other physical
factors affect the chances of an oil spill? 2.Other resources like fish
stocks, marine mammals and spawning grounds that may be
affected by an oil spill.

Human Factors
 Worker Safety including; 1.How safe can the drill rig and
production platform be for the workers?
 Financial Factors including; 1.Cost of inputs like building a
rig to withstand icebergs or building a rig to drill at great
depths. 2. Cost of processes like transporting the oil from
offshore to land, or maintaining the platforms equipment.
3. Price of oil set by world markets.
Offshore Oil
Usually occurs in the shallow waters on the
continental shelf (20 to 200m in depth)
Can occur in water as deep as 2000 meters
deep.
Once an oil reserve is found and the oil rig is
developed, they can start extracting the oil.
Extraction of oil is done through an offshore
oil rig.
Oil is then transferred to land on oil tankers or
pumped through pipes.
Oil Rig
Oil Tanker
There are four different types of oil rigs.

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1. Submersible
2. Jack-Up
3. Anchored Semi-Submersible
4. Dynamically Positioned Semi-Submersible

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
1. Submersible
Rests on columns
attached to pontoons.
Once towed to site
pontoons flooded until
platform rests on ocean
bottom.
Restricted by depth to
(20m).
No storage capability.
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Jack-Up
Supported by legs resting
on sea floor
Built to replace drill ships
Access to deeper water
restricted to 100m
More open to elements
To relocate, “legs” must
be lifted (time consuming
under hazardous conditions)
No storage capability

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Semi-Submersible
Allows to get into
deeper water (200m) &
heavy seas
Partial submergence to
keep it stable
To maintain stability
water pumped in or out
of pontoons
Oil stored in pontoons
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Dynamically Positioned
Semi-Submersible
Can reach depths up to
2000m
In unstable conditions can
detach quickly
Easy to relocate
Partially submerged to keep
it stable
Stores oil in pontoons
To maintain stability water is
pumped in or out of pontoons
Our Life style depends on energy (Oil and Gas
being dominant)

Oil is valued as a fuel because it produces large
amounts of heat and power per unit of mass. It is
relatively easy to store, move, and convenient as a
source of energy for transportation.

Also, oil is a raw material that can be processed
into refined products.

This move to offshore oil production has
occurred for three reasons



1. Reduced exploration costs due to improved treedimensional imaging and other exploratory techniques
2. Improved design of rigs, storage facilities, and offloading
systems
 3. Most importantly, directional drilling (see fig. 11.5 p. 187)
which allows rigs to reach deposits several Km away from the
rig.


World oil prices:
1. High prices, encourage companies to develop oil
production
2. Low prices discourage companies due to
reduced profit. Ex. 1984-1990 Hibernia did not
begin due to low oil prices.
Government policy:
1. Tax breaks encourage companies to develop oil
production
2. Tax increases discourage companies due to
reduced profit

The decision
whether to drill or not
often comes down to
the question: will the
cost of overcoming all
other factors be
offset by the price oil
can be sold for and
make the venture
financially viable?




Keeping the Connection to Land
In the 1860’s wharves were built extending
365m out into the ocean to facilitate ocean
drilling off California.
Letting go of Shore
In the 1920’s a drill rig was built on wooden
pilings in lake Maracaibo , Venezuela
Moving to Steel
In the 1930’s a drill rig was built on steel
structures in the Gulf of Mexico but it was
limited to 7m of water or less.
Letting go of the Ocean Floor
In 1956 the first drill ship was built allowing
drilling in deeper water. These types of drill
ships (on following slide) allowed
exploration off the shores of
Newfoundland.
NFLD
Oil Drill Ship
We will investigate 4 different types of oil rigs used to
recover oil from under the ocean floor. Figure 11.4 in your
book shows all four rig types.

Submersible Rigs: fixed columns ground them on the
ocean floor

Jack-up Rigs: extendable legs ground them on the ocean
floor

Semi-submersible Anchored rigs: are anchored above the
drill site.

Semi-submersible Dynamically Positioned: use thrusters to
maintain position above the drill site.
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Submersible rigs are
normally limited to ocean
depths of 20 m. For this
reason they are limited to
continental shelves,
relatively close to shore.
The rigs are floated as they
are towed to drill site. Once
in position ballast tanks are
flooded until columns rest
on ocean floor.
The picture to the right
shows a small submersible
rig.
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
Jack-up rigs are able to drill in
deeper water than submersible
rigs. However, jack-up rigs are
limited to a maximum ocean
depth of 100 m. The jack-up is
similar to the submersible in that
it rests on the ocean floor.
However its steel legs (Not
columns) rest on ocean floor.
These are distinguishable by
high X-braced steel legs which
extend above the platform.

Semi-Submersible Anchored
rigs float on the ocean.
Because they are anchored to
the ocean floor they are are
limited to a maximum ocean
depth of 200 meters. The rigs
are built on land which is
flooded upon completion so
the rig floats. Then the rig is
towed to the drill site. Water
is pumped in and out of
Ballast tanks to help stability
along with anchor lines. Oil is
stored in pontoons until
shipped on-shore.
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Semi-Submersible Dynamically Positioned rigs are
able to drill outside the continental shelf. However,
they are still limited to a maximum ocean depth of
2000 meters. Like other rigs they are towed to the
drill site. Water is pumped in and out of Ballast
tanks to help stability but there are no anchor lines.
Note: dynamic means changing or moving.
Thrusters position the rig over the drill site. Like the
Anchored rigs oil is stored in pontoons until shipped
on-shore.

Directional Drilling is depicted in figure 11.5 on
page 187 of your text. This technique allows drill
companies to reduce movement from one small oil
pocket to the next. It also increases the drill holes
exposure to source (porous) rock.
The Hibernia case study in your book serves as a
great example of a number of the topics we are
looking at. It is not important for you to remember
every fact, detail, piece of technology at Hibernia as
much as it is important for you to recognize this as
an example of:

Types of drill rig platforms & reasons for using
them

Stages and components of oil field development
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