Deepwater drilling facts for kids
Deepwater drilling is a way to dig holes deep under the ocean floor to find and bring up oil and natural gas. It uses special equipment called a drilling rig. This type of drilling happens in very deep parts of the ocean, usually where the water is more than 150 meters (about 500 feet) deep. For example, there are about 3,400 deepwater wells in the Gulf of Mexico.
For a long time, drilling in such deep waters was too hard or too expensive. But as the need for energy grew, companies started investing more in this technology. Big companies like Halliburton and Transocean are involved. Even after the 2010 Deepwater Horizon accident, deepwater drilling has continued to grow because the world still needs a lot of energy.
Companies use special tools to find oil deep under the ocean. They use sound waves to map the ocean floor and find good spots to drill. Then, they use a large floating rig called a mobile offshore drilling unit (MODU) to start drilling. This unit drills down into the ocean floor. The long pipe that goes from the rig to the ocean floor is called the riser. It helps drilling liquids move between the rig and the well. Inside the riser, a drill string (a series of pipes with a drill bit) digs deep into the ground to reach the oil. Once oil is found, the MODU might be replaced by a more permanent rig to collect the oil.
Contents
How Deepwater Drilling Works
Deepwater drilling is needed because some oil and gas deposits are buried far beneath the ocean floor. These deposits cannot be reached from land or in shallow water.
Finding Oil Under the Sea
First, oil companies use special sound equipment to create maps of the ocean floor. These maps help them find the best places where oil might be hidden. They look for signs of oil and gas deep underground.
Starting the Well
After finding a good spot, a large floating rig called a mobile offshore drilling unit (MODU) moves into place. This unit is like a big floating platform with a drill. Its main job is to drill the first hole, called the initial well.
Drilling Down Deep
The MODU lowers a long pipe called a riser from its deck down to the ocean floor. This riser acts like a tunnel. Inside the riser, engineers send down a drill string. The drill string is made of many pipes connected together, with a drill bit at the end. This bit spins and digs through the rock and sediment to reach the oil deposit. The riser also helps move special drilling fluids back and forth between the rig and the well. These fluids help clean the drill bit and keep the well stable.
Collecting the Oil
Once the oil deposit is reached, the MODU might switch from drilling to collecting the oil. More often, the oil company will replace the MODU with a different, more permanent oil production rig. This new rig is designed to continuously bring the oil up from the well. The oil is then sent through pipelines or loaded onto ships to be taken to shore for processing.
History of Deep Wells
People have been digging deep wells for a very long time. Some of the earliest examples of deep wells come from China.
Ancient Chinese Wells
The ancient Chinese were very good at digging deep wells to find drinking water. They started doing this thousands of years ago. A very old Chinese book called The Book of Changes talks about how people in the Western Zhou dynasty (around 1046 to 771 BC) took care of their wells.
Archaeologists have found proof that the Chinese were digging deep water wells as early as 6,000 to 7,000 years ago. For example, a well found at the Hemedu site was built during the Stone Age. It was lined with four rows of logs to keep it strong. Also, 60 old tile wells found near Beijing are thought to be from around 600 BC. These wells were used for drinking water and for watering crops.
Types of Deepwater Drilling Rigs
Drilling in deep water requires special types of rigs. These rigs are designed to work in very challenging ocean conditions.
Mobile Drilling Rigs
There are two main types of mobile rigs that can move to different locations:
- Semi-Submersible Drilling Rigs: These rigs float on the water but have large pontoons (floating structures) that can be partly filled with water. This makes them sit lower in the water, giving them more stability in rough seas.
- Drillships: These are ships that have a drilling rig built into their center. They can move quickly between drilling sites and are very good for drilling in extremely deep waters.
Fixed and Floating Platforms
Once a well is drilled, or for long-term production, companies use different types of platforms:
- Fixed Platform: This platform has a tall steel structure that is anchored directly to the seafloor. It is very strong and stable but costly to build. Fixed platforms can be used in water up to about 500 meters (1,640 feet) deep.
- Jack-Up Rig: These are mobile units that float to a location. Once there, they lower long legs to the seafloor and lift the platform out of the water. This makes them very stable and safe because they are not affected by waves.
- Compliant Tower Platform: This is a type of fixed platform, but it is taller and narrower. It is also anchored to the seafloor. Compliant towers can work in water depths up to 1 kilometer (3,280 feet).
- Semi-Submersible Production Platform: Similar to the drilling rig, this platform floats. However, the wellhead (the top of the well) is often on the seafloor. Special care is needed to prevent leaks. These rigs can operate in water from 200 to 2,000 meters (650 to 6,500 feet) deep.
- Tension-Leg Platform: This platform floats but is held in place by strong cables (tendons) that go down to the seafloor. They are often used for smaller oil deposits and can be a cheaper way to get oil. They can drill in water from 200 to 1,200 meters (650 to 3,900 feet) deep.
- Subsea System: These are wellheads that sit directly on the seafloor. They extract oil and use pipes to send it up to the surface. The oil can go to nearby platforms, ships, or even to processing sites on land. This makes them very flexible.
- Spar Platform: This platform uses a large, hollow cylinder that extends deep underwater to support the floating deck. About 90% of its structure is underwater. Spar platforms are often used in depths up to 1 kilometer (3,280 feet), but new ones can reach depths of 3,500 meters (11,500 feet), making them one of the deepest drilling rigs used today.
The 2010 Deepwater Horizon Oil Spill
On April 20, 2010, a serious accident happened on the Deepwater Horizon oil rig, which was drilling for BP in deep waters. An explosion occurred, tragically killing 11 workers. A huge amount of oil, about 750,000 cubic meters (200 million gallons), spilled into the Gulf of Mexico. Many experts consider this one of the worst environmental disasters in U.S. history.
The oil spill caused a lot of harm to wildlife. Studies estimate that over 82,000 birds, about 6,000 sea turtles, and nearly 26,000 marine mammals died because of the explosion or the oil. Because of this disaster, making sure deepwater wells are safe and secure has become extremely important in the oil industry.
See also
- Offshore drilling
- Well drilling
- Shallow water drilling
- Extraction of petroleum
- Age of Oil
- Energy development
- 2010 United States deepwater drilling moratorium
- Submersible pump
- Deepwater Horizon
External articles
- Deepwater Drilling: How It Works | Chevron | Video. chevron.com.
- HowStuffWorks "Ultra Deep Water Oil Drilling". science.howstuffworks.com.
- Rigzone - Deepwater Gulf of Mexico Drilling Activity to Keep Rising. rigzone.com. April 24, 2013.
