OFFSHORE OPERATION introduction to :

delivered by : Arif Fajar Utomo L2C008118 in sharing knowledge class Semarang, April 17th 2012

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.

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 cant just rely on the onshore exploitation of petroleum. And since oceans cover nearly three-quarters of Earths surface, so logically there were bigger chance of having reservoirs on the offshore.

The reason why we need 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.

Historical review towards 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)

Steps in Offshore Drilling

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.

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.

Exploration

The petroleum company often dont 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 ones.

Own the land

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 well 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

Spud-in

But when your seafloor is covered in a deep layer of loose sediment (like what happened in the Gulf of Mexico), you dont 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.

Spud-in

Spud-in

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 well 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).

Drilling a hole for second string of casing

Drilling a hole for second string of casing

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.

Cementing the first two casing sections in place

Connecting the BOP and marine riser on top of the wellhead

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.

Drilling the remaining section of the well

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 doesnt 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.

Determining if a well has a produceable amount of petroleum

SESSION 1

Mobile drilling platform is being used in the exploratory drilling, to drill and to find out if theres oil and then move on to the next site. Mostly, the oil company didnt 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.

Mobile drilling platforms

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