SKC Undip

1. introduction to :
OFFSHORE OPERATION
delivered by : Arif Fajar Utomo
L2C008118
in sharing knowledge class
Semarang, April 17th 2012

2. Presentation Including :
• The reason why we need offshore drilling.
• Historical review towards offshore drilling.
• Steps in Offshore Drilling.
• Mobile drilling platforms.
• Offshore production platforms.
• About Offshore Engineers.

3. The reason why we need offshore drilling
Based on the fact that we consume more than 80 million barrels of oil
every day in 2011 (source: CIA) and it is increasing until now due to
economic and population growth. In fulfilling this demand, we can’t
just rely on the onshore exploitation of petroleum. And since oceans
cover nearly three-quarters of Earth’s surface, so logically there were
bigger chance of having reservoirs on the offshore.

4. Historical review towards offshore drilling
The idea of offshore drilling is already being initiated from many years ago:
In 1897, the first platform was constructed at the end of a wharf in California.
In 1928, first mobile oil platform for drilling in wetlands is unveiled, the structure
was similar with a barge.
In 1947, a consortium of oil companies built the first platform on the ocean, in the
Gulf of Mexico.
And the development continues, as today, oil rigs are truly gigantic structures
employing and housing hundreds of people. Some rigs, have a 4,000 feet or 1.2 km
in height.

5. Steps in Offshore Drilling
Steps in offshore drilling are including:
• Exploration
• Own the land
• Spud-in
• Drilling a hole for second string of casing
• Cementing the first two casing sections in place
• Connecting BOP and marine riser on top of the wellhead
• Drilling the remaining section of the well
• Determining if a well has a produceable amount of petroleum
(source: www.treesfullofmoney.com)

6. Exploration
Exploration is the first thing we do in order to find the petroleum reservoirs under
the sea. There are many methods that can be used to, one of them is using seismic
surveying or also known as sparking.

8. Exploration
We can also implement the magnetic method in the offshore by using sensitive
magnetic survey equipment that is attached on the ship that pass over an area and
map any magnetic anomalies that occur. This method can also give us a decription
of the underground traps.

9. Own the land
The petroleum company often don’t own the block especially if the area is in
economic zone (200 miles from one country), therefore in this case, the petroleum
company has to obtain a government lease for the block and also for the mineral
either to begin drilling legally, unless the block and the mineral is no one’s.

10. Spud-in
After we leased the mineral right and the block, knew the success rates for drilling an
offshore oil well, and have decided on what type of oil rig to use to drill our well, the
first thing we do then is to spud in.
When drilling oil wells in deep water (>1000′), this involves forcing 300-400 feet of 36″
diameter metal tubing called “casing” into the ground. This 36″ diameter casing will
form the backbone of the well and provide the support we’ll need for the remaining
phases in our well construction plan.
The 36″ casing is lowered to the seafloor by “drill pipe”. Each section of drill pipe is
anywhere from 30-45 feet long and about 6″ in diameter. The drill pipe is connected
end to end and gradually lowered down into the well and back up to the surface as
needed.
To help speed up the time connecting hundreds of sections of drill pipe together every
time you want to lower a drill bit, casing, or other piece of equipment into the well, the
drill pipe is stored in the derrick three or for sections at a time. This saves the drilling
companies time and money.
Each section of drill pipe is called a “joint“, and when two or more “joints” connected
and “racked back” in the derrick they are then called a “stand“

11. Spud-in
But when your seafloor is covered in a deep layer of loose sediment (like what
happened in the Gulf of Mexico), you don’t really need to “drill” the 36″ casing into
the ground. In most cases, pumping sea-water through the end of the casing using
the ships massive pumps is all you need to do to get the pipe to settle into the
ground.
As the casing gets deeper and deeper into the ground, some rigs use giant
“hammers” to pound the casing into the ground to the desired depth.
When the 36″ casing is set to the correct depth, we unlatch the drill pipe from it and
pull the drill pipe back to the surface so that we can get the next section of
casing and proceed to step 2 of our well drilling program.

12. Spud-in

13. Drilling a hole for second string of casing
The next step in our well drilling plan is to lower a drill bit down inside the 36″
casing we just set into the seafloor. Once the drill bit enters inside the 36″ casing
we’ll drill 2000-3000′ into the ground. We need to make sure the bit we are using is
large enough so that we can run our next section of “casing” into the ground
(running the casing inside the 36″ casing).

14. Drilling a hole for second string of casing

15. Cementing the first two casing sections in place
Once the 22″ casing is set inside the 36″ casing, the two different sized casings are
cemented in place. This is accomplished by pumping cement down the drill pipe
(represented in yellow in the picture below) and out through a special nozzle on the end
of the pipe.

16. Connecting the BOP and marine riser on top of the wellhead

17. Drilling the remaining section of the well
The remaining sections of the well are drilled the same way as the 22″ casing was
drilled in the earlier step only now the cuttings and mud are circulated back up to
the drillship to be processed.
The drill crews will drill deeper into the ground so that the next section of casing
can be run and cemented into place. There is no set limit on how long each section
of casing will be, this decision is left up to the drilling engineers that have closely
analyzed the survey data and any data from nearby or “offset” wells.
As the drill bit continues to make its way towards the oil or “pay zone”, the drilling
crew closely monitors the amount of fluid in the storage tanks as well as the
pressure of the formation to ensure that the well is now experiencing a blow-out or
kick.
If it is determine that the well is experiencing a “blow-out” or kick, the Blow Out
Preventer (BOP) control valves are closed off and the drill crew must take measure
to stabilize the well. To stabilize a well that has experienced a “kick”, the drill crew
is usually able to control it by pumping heavier drilling fluids into the well to
“force” the kicked pressure back into the formation.

18. Determining if a well has a produceable amount of petroleum
A series of test called “logs” will be conducted to determine how much oil and gas (if
any) is present in the formation. The process is called logging because the information
is “logged” into a database as it is collected.
This is accomplished by sending high tech measurement devices into the hole that can
detect various features of the formation.
Using a combination of sound wave tools, electrical wave tools, and radiation
measurement instruments, geologist are able to take readings inside the well which will
assist them in determining the presence of oil.
However, just because there is oil or gas at the bottom of the well doesn’t always mean
it is worthwhile to pump it out. Oil companies must decide whether the amount of oil
present in the formation is worth investing hundreds of millions of dollars in additional
equipment to pump it out and back to a refinery.
In some instances, an oil company may decide to “test flow” a well to help determine
how much oil is there. When test flowing a well, oil is allowed to flow up from the well
into storage tanks. The pressure is recorded and if it remains at certain levels over a
certain amount of time, the oil companies may decide that investing more money to
“produce” the well is worth the costs.

19. SESSION 1

20. Mobile drilling platforms
Mobile drilling platform is being used in the exploratory drilling, to drill and to find
out if there’s oil and then move on to the next site. Mostly, the oil company didn’t
have the mobile drilling platforms. Since it is more cost effective to hire expertise
and equipment needed than to keep it under their roof.
The expertise in here refers to the drilling contractor and the service company like
Transocean, Schlumberger, Pride, Frontier, and Sea-Drill.
There are 5 varieties of mobile drilling platforms: drilling barge, jack-up, semi-
submersible rig, submersible rig, and drill ships.