Chikyū: World Record Drillship
Chikyū is a drillship built for scientific research, drilling holes as deep as 7,000 meters into the sea floor. The mission is to drill into tectonic plates and the earth’s mantle to get information on understanding how plates move and better predict earthquakes like the one that devastated the Fukushima nuclear power plant. In Japanese, Chikyū means “Earth”, a nod to the work the vessel is doing to deepen our understanding of the planet. It was delivered in 2005 for the Japanese Agency for Marine Earth Science and Technology (JAMSTEC) by Mitsubishi Heavy Industries. According to Ship Technology, full operations started in 2007 after system integration tests, including drilling off the Shimokita Peninsula. Chikyū is registered in Yokosuka, Japan, where JAMSTEC is headquartered, and does not have a home port since it travels all over the world.
Chikyū on the water. Image from JAMSTEC.
Earthquakes and the mantle
When tectonic plates push on each other, they build frictional strain, or distortion that can be suddenly released, causing an earthquake. The point of strain is called an “Asperity” or bulge, and when the asperity overcomes friction, the plates slip. This movement can be small, just a fraction of the subduction zone, or large. Chikyū works with scientists all over the world who focus on the best places to drill, and have not yet drilled through an asperity. The mantle is solid rock that is believed to be moved by the outer core, very slowly. Deeper down, with additional temperature and lower pressure, these rocks become magma. This magma can rise up through the mantle and crust, cooling on the ocean floor as basalt or coming through the ground as lava. No one has ever taken a sample of magma directly from the mantle, which is one of the goals of Chikyū.
"Chikyū’s specifications compared with typical landmarks.” Image from JAMSTEC.
For drilling, the ship contains a 12 by 22 meter moonpool for the drillstring to pass into the water. A crown-mounted heave compensator allows for some vertical and horizontal ship movement during operations. An automated pipe transfer system moves pipes into place to connect them to the drillstring that can be thousands of meters long. There is a blowout preventer system to prevent pressure forcing its way back up the drill pipe that can handle 103MPa, or approximately 14,939 psi. It can drill with a riser or perform riserless drilling. An electric hydraulic knuckle boom crane helps to load and unload supplies like drill pipes and casings from other supporting vessels. According to JAMSTEC, Chikyū has 10 km, or 10,000 meters of pipe onboard consisting of:
Riser pipe that connects the ship to the seabed, which the drill pipe passes through
Drill pipe that drills the hole - the bit is attached to this pipe
Casing pipe that protects the interior borehole wall during drilling
Since the riser can be 2,500 meters, the maximum hole that can be drilled is 10,000 - 2,500, or 7,500 meters. Soft sediments like mud can be drilled at a rate of about 300 meters per day, while firmer materials like rock can be as slow as 50 meters per day. Drilling with risers can take 6 months or longer during which Chikyū is stationary on the water.
Riser pipe on the Chikyū. Image from JAMSTEC.
Chikyū is dynamically positioned with six 4,100kW azimuth thrusters (three forward and three aft) and one 2,550kW side thruster. These thrusters work together with a global positioning system (GPS) to keep the vessel on station for precise deepwater drilling. Maximum speed is 12 knots, or about 14 mph and it usually carries about 100 operating crew and 50 scientists. Six generators with 5,000kW each power the Chikyū with two auxiliary generators rated for 2,500kW each.
Azimuth thruster. Image from JAMSTEC.
Chikyū has state of the art laboratories on board for analyzing core samples quickly before changes in the materials occur. The core is fed onto the ship and then cut into smaller sections for processing in multiple labs that allow for the study of materials as soon as they are retrieved. According to Smithsonian, onboard tools and labs include:
CT x-ray scanner to see inside the cores
Microbiology lab to document microorganisms
Paleomagnetism lab that is mostly shielded from outside magnetic forces, including the Earth’s magnetic field
Geochemistry lab that can analyze water in the samples
Paleontology lab where fossilized animals and plants are examined
Petrology lab where the history of rocks are studied
The labs on board promote knowledge exchange among scientists around the world. Check out more information on these labs and Chikyū’s functions in the video on Smithsonian.
X-ray CT scanner on board Chikyū. Image from JAMSTEC.
In May 2009, Chikyū started a two-month expedition to start boreholes and at two different sites that will eventually receive long-term borehole monitoring systems. 1,600m and 555m boreholes were drilled.
In October 2009, the vessel completed coring, logging, and downhole measurements at a depth of 1,200 meters under the seafloor, with another site cored at 600m below 4,000m of ocean, according to Ship Technology.
In March 2011, a 9.0 earthquake started a tsunami in Japan, prompting Japanese officials to send the Chikyū to the undersea fault zone. The “Japan Trench Fast Drilling Project” will hopefully glean more information on the forces involved in earthquakes.
In 2019, Chikyū drilled the deepest hole that has ever been drilled in the ocean at 3,250 meters. The goal was to drill to 5,200 meters to investigate where two tectonic plates come together and cause large earthquakes, but the drill hole kept collapsing. The engineers used every trick in the book, lining the hole with steel as they drilled, even drilling multiple branches off the original hole, called sidetracking. This technique is commonly used in oil and gas, but those holes collapsed as well and the team finally had to abandon the project. After six months of drilling, the goal is now to figure out what the problem was and correct it. The issue is being worked on by researchers and the Japan Agency for Marine-Earth Science and Technology, including MarE3.
Check out the video below about the process of drilling extremely deep holes under the ocean with Chikyū.
Off Japan’s southeast coast is the Nankai Trough where the Philippine Sea plate is driven beneath the Eurasian plate, causing huge earthquakes every 100 to 150 years, according to Nature. Two earthquakes over magnitude 8 happened in 1944 and 1946. Chikyū is the only vessel that can drill deep enough to reach the location. Even though drilling to the mantle is the ultimate goal, many of Chikyū’s projects have borne fruit. It has investigated sites of smaller earthquakes, learned more of the geology of the fault that caused the 2011 Tohoku earthquake, and found how much heat life can withstand under the sea bed. The 5,200 meter goal is still on the horizon as many hope to drill to that depth elsewhere. The expeditions teach us about geology, life, our planet, and how to improve drilling techniques for future projects.
Olivine rock from the Earth’s mantle. Image from JAMSTEC.
If you’d like to learn more about research ships, check out FLIP and Nuyina:
If you’d like to know more about dynamic positioning and the vessels that use it, check out:
Happy Fun Fact Friday!