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OIL AND GAS
OPERATIONS
MODULE 1
HYDROCARBON
INDUSTRY OVERVIEW
1
MODULE 1 – HYDROCARBON INDUSTRY OVERVIEW
OIL GURU ACADEMY & ARJ CONSULTANTS
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TABLE OF CONTENTS
1. Module Objectives
4 2. The Origins of Crude Oil and Natural Gas
5 3. Oil Traps
7 4. Searching For Formations That Might Contain Hydrocarbons
9 5. Drilling For Oil and Gas
10 6. The Hoisting Equipment
10 7. The Rotating Equipment
10 8. The Circulating Equipment
10 9. Types of Drilling Rigs
11 10. Down Hole Tubulars
11 11. Surface Casing
12 12. Intermediate Casing
12 13. Production Casing
13 14. Production Tubing
14 15. The Wellhead
15 16. Surface Casing Head
16 17. Intermediate Casing Head
16 18. Production Casing Head
16 19. Production Tubing Head
16 20. Christmas Tree
17 21. Directional Drilling
18 22. Horizontal Drilling
18 23. Crude Oil Recovery
19 24. Reservoir Pressure Maintenance
20 25. Well Stimulation
21 26. Acid Stimulation
21 27. Hydraulic Fracturing
21 28. Movement of Crude Oil to Processing Plants
22 29. Oil Production Degassing Plants
23 30. Production Degassing Separator
23 31. Gas Processing
24 32. Refining of Crude Oil
25 33. Petroleum Products
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TABLE OF FIGURES
Figure 1 - Precambrian Period .................................................................................... 5 Figure 2 - Physics of Typical Oil Bearing Rock ........................................................... 6 Figure 3 - Typical Anticline Trap ................................................................................. 7 Figure 4 - Fault Trap ................................................................................................... 8 Figure 5 - Statigraphic Trap ........................................................................................ 8 Figure 6 - Types of Traps ............................................................................................ 8 Figure 7 - Seismic Survey ........................................................................................... 9 Figure 8 - Different Types of Drilling Rigs ................................................................. 11 Figure 9 - Surface Casing ......................................................................................... 12 Figure 10 - Production Casing .................................................................................. 13 Figure 11 - Casing, Tubing and Production Packer .................................................. 14 Figure 12 - Stages of Shaped Charge Perforations .................................................. 15 Figure 13 - Single String Wellhead and Xmas Tree .................................................. 17 Figure 14 - Typical Onshore Wellhead and Xmas Tree ............................................ 18 Figure 15 - Combination of Gas Cap and Water Drive ............................................. 19 Figure 16 - Water Injection ........................................................................................ 20 Figure 17 - Propogation of Acid Stimulation .............................................................. 21 Figure 18 - Simplified Production Flow ..................................................................... 22 Figure 19 - Production Inlet Manifold ........................................................................ 22 Figure 20 - Distribution of Various Oil and Gas Deposits and Associated Wells ...... 23 Figure 21 - Horizontal Production 2 Phase Separator .............................................. 24 Figure 22 - Typical Onshore Crude Oil Refinery ....................................................... 25 Figure 23 - Distribution of Light End Hydrocarbons .................................................. 26 Figure 24 - Simplified Crude Fractionating Tower ..................................................... 27 Figure 25 - Refinery Petroleum Products .................................................................. 28 3
MODULE 1 – HYDROCARBON INDUSTRY OVERVIEW
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1. MODULE OBJECTIVES
Any process operator should have a general knowledge and
understanding of how companies operate their hydrocarbon industry.
This module will teach you the following:
•
How crude oil and natural gas were formed
•
How underground locations for oil and gas are found.
•
How we drill into those underground formations.
•
How we bring the oil and gas to the surface.
•
How the crude oil and gas move from the well head to different
processing plants.
•
What happens to the crude oil and gas in the processing plants.
•
This unit is your introduction to the orgins of oil and gas and is generic
in its approach. Detailed modules will follow taking you from reservoir
to point of delivery.
•
To achieve the module certificate you must complete the online course
and pass the final test with 80% or more.
•
Take the online course and gain your certificate of achievement here:
http://oilguru.org/oil-guru-academy/
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2. THE ORIGINS OF CRUDE OIL AND NATURAL GAS
Millions of years ago many plants and animals died and became
deposited in various locations, predominately in the sea. The remains of
these plants and animals built up upon each other together with dust,
sand and debris.
This dust and sand covered the remains of the plants and animals. (See
Figure 1).
Figure 1 - Precambrian Period
This process continued for many, many, years.
The weight of the thick layers of dust and sand increased with time and
squeezed the remains of the plants and animals.
The pressure changed the remains of the plants and animals to
hydrocarbons. (Oil and Gas)
The pressure also changed the dust and sand to rock.
Solids that fall to the bottom of a liquid are called sediments so the rock
that formed from the dust and sand is called sedimentary rock.
Because sedimentary rock was formed under the sea all the gaps and
holes in the rock are filled with water.
These gaps and holes in the sedimentary rock are called “pores” so
sedimentary rock is “porous” rock. Porosity means how many gaps and
holes the rock contains.
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There is sometimes a mixture of salt water and hydrocarbons in the pores
of the sedimentary rock.
The hydrocarbons are lighter than water (oil floats on top of water) so the
hydrocarbons will try to rise up through the water. If the pores in the rock
are joined together the rock is permeable and the hydrocarbons can move
through it.
The ability of a rock to let liquids move through it is called “permeability”.
A rock that is porous and permeable will let liquids pass through it. (See
Figure 2).
Figure 2 - Physics of Typical Oil Bearing Rock
Hydrocarbons in sedimentary rock move upwards through the rock until
they are above the water. They can rise all the way to the surface where
they can be lost into the air or form lakes of heavy hydrocarbons.
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3. OIL TRAPS
In may situations hydrocarbons formed in sedimentary rock can not rise
all the way to the surface if there is something to stop them. They are
trapped.
If the porous sedimentary rock is covered by a non porous rock the
hydrocarbons stop moving when they meet the non-porous rock.
This is because non-porous rock is “impermeable”, which means fluid
cannot pass through it. (See Figure 3). Because the impermeable rock is
on top of the trap it is called a “cap rock”.
Figure 3 - Typical Anticline Trap
There are many different types of oil traps. The type depends on how the
trap was formed.
Anticline traps are formed by the movement of the earth’s crust.
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The other types of traps found are fault traps and stratigraphic traps. (See
Figures 4 and 5).
Figure 4 - Fault Trap
Figure 5 - Statigraphic Trap
Figure 6 - Types of Traps
The sedimentary rock where the hydrocarbons have been trapped is
called the “reservoir rock”.
The trap itself is also called a “formation”. The trap is formed by the
shape of different rocks.
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4. SEARCHING FOR FORMATIONS THAT MIGHT CONTAIN HYDROCARBONS
We cannot see under the ground. We cannot know if there are oil traps 4
to 5 kilometres below the surface of the earth.
We have to use scientific methods in our search for oil and gas
formations.
The main method used is the “seismic survey”.
In simple terms, vibrations are made at the surface of the earth. This is
done with a number of explosions or a heavy vibrator on a truck.
The vibrations travel down through the layers of rock under the ground.
Some of the vibrations bounce off the layers of rock and others continue
through the layers of rock. We are able to measure the speed and
strength of the vibrations as they return to the surface.
Computers take all these measurements and draw a picture of the shape
of the rocks under the ground.
When we know the shape of the rocks we can see if there are any
formations that might be oil traps. (See Figure 7).
Figure 7 - Seismic Survey
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5. DRILLING FOR OIL AND GAS
When the survey team find a place where they think there might be oil
they have to drill a hole down into that formation.
The method for drilling holes is called “Rotary Drilling”.
The drilling rig equipment is powered by diesel electric. This means that
very large diesel engines turn electric generators to produce direct electric
current.
The direct current is then used to power pumps, hoists, compressors and
other equipment.
The mechanical equipment used on a rotary drilling rig is grouped into
three areas.
•
The hoisting equipment
•
The rotating equipment
•
The circulating equipment
6. THE HOISTING EQUIPMENT
The hoisting equipment lifts the drilling column in and out of the hole.
7. THE ROTATING EQUIPMENT
The rotating equipment turns the drilling column so that the drill bit can
make a hole.
8. THE CIRCULATING EQUIPMENT
The circulating equipment pumps liquid down the hollow drilling column. It
comes back up to the surface through the space between the drilling
column and the walls of the hole which is called the annulus.
The main job of this liquid is to remove the small pieces of broken rock
made by the drill bit. It also lubricates and cools the drill bit and drill pipe.
It prevents blow outs and supports the walls of the hole. A blow out is
when the well flows out of control.
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9. TYPES OF DRILLING RIGS
Different types of drilling rigs are used for different areas (see figure 8).
Even though the drilling rigs are different they all operate the same way.
Figure 8 - Different Types of Drilling Rigs
10. DOWN HOLE TUBULARS
Different sizes of steel pipe are installed in the well as it is drilled deeper.
The hole is wide at the surface, 75cm and narrow when it reaches the
depth were the oil is, 24cm, or 18cm.
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11. SURFACE CASING
The earth has soft sandy and sticky layers near to the surface. There is
also good fresh water near the surface. A large size hole is drilled
through these layers and a large steel pipe is inserted.
This steel pipe is called “casing”. Because it is at the surface of the well it
is called surface casing.
This surface casing is cemented in place. It seals off the water zones and
supports the walls of the hole. (See Figure 9).
Figure 9 - Surface Casing
12. INTERMEDIATE CASING
As the well is drilled deeper and deeper into the ground problems can
occur. These problems could make it difficult to continue to drill.
A second string of casing is then put into the well and cemented in place.
This casing string is called intermediate casing. (Intermediate means
between two points). There can be more than one intermediate casing.
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13. PRODUCTION CASING
The well is drilled down through the formation that contains the oil. Then
the final casing string is put into the well and cemented in place.
This string of casing is called production casing.
The production casing goes all the way to the surface (see fig. 10).
If the production casing does not go all the way to the surface, which can
happen due to high cost, it is called a production liner.
Figure 10 - Production Casing
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14. PRODUCTION TUBING
This the final string of steel pipe put into the well. It is NOT cemented in
place.
The bottom of the production tubing is held in place and sealed inside the
production casing by a device called a packer. The top of the production
tubing is hung and sealed at the surface.
All gas and oil produced from the well flows up the inside of the production
tubing.
When the production tubing gets old and worn it can be pulled out of the
well and replaced. That is why it is not cemented in place (see fig. 11).
Figure 11 - Casing, Tubing and Production Packer
a Typical Single String Well Completion
Recall that the production casing is cemented in the well through the
formation that contains the oil.
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There is no way for the oil or gas to enter the well through the sides of the
bore. (The bore is the hole made by the drill).
Holes have to be made through the production casing and through the
cement into the oil bearing rocks.
This is done by using special explosive charges. The process is called
perforating and the holes are called perforations. (See Figure 12).
Figure 12 - Stages of Shaped Charge Perforations
15. THE WELLHEAD
The wellhead is the equipment at the top of the well. It is used to keep
control of the well. It forms a seal to prevent well fluids blowing or leaking
at the surface.
How strong the well head is depends on how high the pressure is in the
well.
The wellhead is made up of casing and tubing heads, the christmas tree
and pressure gauges.
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16. SURFACE CASING HEAD
This is attached to the surface casing which is the first and largest
diameter casing put into the well.
17. INTERMEDIATE CASING HEAD
This is attached to the casing that was run into the well to overcome
problems when drilling. This casing covers formations that may cause
blow outs or fall in and fill the hole.
This casing head is put on top of the surface casing head.
18. PRODUCTION CASING HEAD
This is attached to the production casing that goes all the way to the
bottom of the well.
This casing head is put on top of the intermediate casing head.
19. PRODUCTION TUBING HEAD
The tubing head is attached to the production tubing. Because the
production tubing is not cemented into the well the tubing head also
supports the weight of the production tubing.
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20. CHRISTMAS TREE
This is the collection of valves that goes on the top of the well head. The
well is controlled at the surface, and serviced by using these valves.
Figure 13 - Single String Wellhead and Xmas Tree
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Figure 14 - Typical Onshore Wellhead and Xmas Tree
21. DIRECTIONAL DRILLING
Normally wells are drilled straight down vertically. Sometimes it is
necessary or better to drill at an angle, especially offshore on a platform.
Drilling at an angle is called directional drilling.
Some offshore reservoirs need many wells. With directional drilling more
than one well can be drilled from offshore platforms and towers.
22. HORIZONTAL DRILLING
This is a relatively new technique which some companies use a lot.
Some oil producing formations are not very thick and the rocks have low
permeability. It is difficult for the crude oil to flow into the well bore.
By drilling horizontally through the oil bearing formation much more rock is
in contact with the well bore. Then it is easier for the oil to flow into the
well bore.
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23. CRUDE OIL RECOVERY
The word “recovery” refers to the movement of crude oil from an
underground reservoir, up a well, to the surface of the earth.
Oil recovery depends on the principle that:
A FLUID WILL MOVE FROM A PLACE WHERE PRESSURE IS HIGHER
TO A PLACE WHERE PRESSURE IS LOWER.
In oil production, oil moves from the reservoir, where the pressure is
relatively high, up the well to the surface of the earth, where the pressure
is relatively low.
PRIMARY RECOVERY uses pressures that exist naturally in a reservoir
to push oil up to the surface. The source of this natural pressure is called
a DRIVE.
Some oil fields have a combination drive, with a gas cap above the oil and
water below it. Both the gas cap and the water push the oil into the well
and up to the surface. (See Figure 15).
Figure 15 - Combination of Gas Cap and Water Drive
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24. RESERVOIR PRESSURE MAINTENANCE
Recall that a fluid will move from a place where pressure is higher to a
place where pressure is lower.
The bigger the difference in pressure the more force there is to move the
fluid.
As the oil flows out of a reservoir the pressure in that reservoir drops.
There is less force available to move the fluid.
One method used to overcome this problem is to inject water into the
water zone underneath the oil. (See Figure 16).
Figure 16 - Water Injection
Water is injected by pumping treated water down water wells to raise the
level of the water under the oil. Oil and water do not mix. The water lifts
the oil which is squeezed between the water and the gas cap. This
makes more pressure. More pressure, more flow of oil.
Companies also use gas injection to keep up the pressure. Gas produced
with the oil is removed from the crude oil, compressed, and injected down
wells into the gas cap.
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25. WELL STIMULATION
To make oil flow more easily and quickly to the well bore we can stimulate
a well. To stimulate the well, new or bigger channels are cut in the rock.
26. ACID STIMULATION
This is done by pumping acid down the well at high pressure. The acid
dissolves the limestone rocks making the cracks and channels in the rock
larger. (See Figure 17).
Figure 17 - Propogation of Acid Stimulation
Special chemicals are added to the acid to help it do its job better, and to
protect the downhole equipment.
27. HYDRAULIC FRACTURING
Fluids containing sand are pumped down the well very fast and at very
high pressure. The force pushing on the rock is very strong. The rock
splits, opening up large cracks. The sand enters the cracks in the rock.
The sand grains keep the cracks open when the pumping is stopped. The
cracks make it easier for the oil to flow from the reservoir into the well
bore.
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28. MOVEMENT OF CRUDE OIL TO PROCESSING PLANTS
Oil that is produced from wells moves through a flow line, then trunk line
system to the production degassing plants.
Figure 18 shows such a system. Flow lines carry crude oil from individual
wells. These flow lines can go direct to the plant or they can go into a
trunk line which goes to the plant.
It is like the small roads leading to the bigger roads in a town.
Figure 18 - Simplified Production Flow
The production manifold system at the entry to the plant is similar to the
one seen in figure 19.
Figure 19 - Production Inlet Manifold
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29. OIL PRODUCTION DEGASSING PLANTS
Degassing means removing the gas from the crude oil.
This is the first step of the many steps that are needed to process the
crude oil into the products that we want.
The degassing of the crude oil takes place in separators in the oil field.
(See Figure 20).
Figure 20 - Distribution of Various Oil and Gas Deposits and Associated Wells
30. PRODUCTION DEGASSING SEPARATOR
The production separator removes the gas that comes up with the crude
oil. The separator is a large diameter cylinder closed at the ends.
The oil and gas mixture enters this large cylinder. The speed or velocity
of flow slows down and the pressure is reduced.
The reduction in pressure causes the gas to escape (come out) from the
crude oil. (It is just like when you remove the cap on a bottle of Pepsi.
The gas bubbles appear from nowhere and float to the top because you
have reduced the pressure).
Because the flow has slowed down the gas has enough time to escape
from the oil. The gas then goes out of the top of the separator and the oil
goes out of the bottom. It is that simple (see figure 21).
There is a lot of equipment inside and outside the separator to help this
happen.
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The principle is always the same.
-
light things go up
heavy things go down
Figure 21 - Horizontal Production 2 Phase Separator
There are many different types of separator used in the process plants.
You will learn about these in later modules. Included in these future
modules are topics such as operational difficulties associated with
separation, and how these may be resolved.
31. GAS PROCESSING
All natural gas that was produced with the crude oil is called associated
gas.
Once the gas is separated from the crude oil it has any water vapour
removed from it.
The gas is then compressed by large compressors and sent through pipe
lines to the gas processing plants.
At the gas processing plants the components that make up natural gas
are separated by distillation.
These processes will be covered in detail in future modules.
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32. REFINING OF CRUDE OIL
The basic job of a refinery is to change crude oil into useful products.
The crude oil must pass through a series of processes, one after the
other. These processes change the crude oil into the finished products
used in our homes and industries. (See Figure 22).
The first and most important process is fractional distillation.
Figure 22 - Typical Onshore Crude Oil Refinery
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The crude oil is heated to 385ºC (725ºF) so that it boils. The hot vapours
and liquids are then passed into a tall vertical steel cylinder called a
fractionating tower.
The lightest vapours go to the top of the tower, the heaviest go to the
bottom of the tower.
The vapours then condense (cool and become liquid) at different levels in
the tower. This is because they have different boiling points (see figure
23).
Figure 23 - Distribution of Light End Hydrocarbons
There are trays in the tower to collect the condensed vapour. There are
pipes from the trays so the liquids can flow out of the tower.
Any vapours that come out with the liquids are sent back into the tower.
(See Figure 24).
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Figure 24 - Simplified Crude Fractionating Tower
Remember that products from the crude distillation are only the first stage
of refinery processing. Reduced crude is further processed to get asphalt,
fuel oil, diesel oil and kerosene.
Naphtha is separated into several fractions, which in turn are further
processed.
Temperature and pressure are very important in the distillation process.
Specific temperatures must be maintained at each distillation point in the
tower. This is so the fractions will condense correctly. You will learn how
process temperature and pressure are controlled in later modules. You
will also learn about refinery operations in much greater detail.
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33. PETROLEUM PRODUCTS
Many more products come from crude oil. Refer to the following table for
a detailed list.
Figure 25 - Refinery Petroleum Products
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OP09 224