Successfully drilled 231 meters in water depth exceeding 2000 meters, setting a new world record.
Deep-sea drilling, "Manatee II" is a real cow (scientific and technological point of view)
Yu Sinan Tang Yahui
Deep-sea mineral resources are abundant. To discover and study them, samples need to be obtained through underwater drilling. Among various sampling methods, submarine drilling rig has become a popular high-tech equipment because of its advantages of low drilling cost, high efficiency, small sample disturbance and easy operation.
Not long ago, China’s self-developed "Manatee II" deep-hole pressure-maintaining coring rig system successfully lowered 231 meters in deep water over 2000 meters, setting a new world record for deep-sea subsea rigs, marking China’s leading level in this field.
It looks heavy, but in fact it is extraordinary.
Drilling below 200 meters means that China has the exploration ability of full coverage of marine resources in theory.
Manatee II was developed by Wan Buyan, a professor at Hunan University of Science and Technology. Wan Buyan introduced that "Manatee II" consists of a submarine drilling rig body, a submarine in-situ detector and a mobile submarine drilling rig supporting retraction system. "Among them, the drilling rig body is an orange-yellow octagonal steel structure with a height of 7.6 meters. ‘ Waist circumference ’ It is 10 meters and weighs 12 tons. It is currently the heaviest geological exploration scientific research equipment in China. "
The seemingly bulky "Manatee II" is flexible when working on the seabed. Its "weapon" is 78 drill pipes, each 3 meters long, arranged on the disk like a revolver bullet. During operation, through the rotation of the disc, the manipulator takes the rod and loads it, and drills the drill pipe into the rock stratum one by one.
The drill bit is equivalent to the horn of "Manatee II" and is made of materials such as diamond and cemented carbide. Researchers have designed different kinds of drill bits, some for hard rock strata and some for sedimentary rock soft rock strata.
Manatee II set a new world record on April 7th. Wan Buyan told reporters that on the same day, after about two and a half hours of diving, "Manatee II" reached the seabed with a water depth of 2,060 meters. After completing the attitude adjustment, Manatee II immediately started pressure-maintaining coring drilling in the target layer. About 15 hours later, the depth of the drilling hole reached 231 meters underground.
In addition to drilling deep, Manatee II also has a unique stunt — — Pressure maintaining and coring. This is the key to explore some seabed minerals such as combustible ice. According to Wan Buyan, under seawater pressure, combustible ice is "ice"-like. Once it leaves its suitable seawater depth, it will become gas volatile due to pressure reduction. Therefore, the common deep-sea drilling rig can’t sample combustible ice, and it can only do so if the pressure of the seabed formation is kept equal.
Previously, the maximum drilling depth design capacity of the global subsea drilling rig was 200m, but the actual pressure-keeping coring operation only reached 135m, and "Manatee II" greatly refreshed this record.
Through drilling sampling analysis, we can understand the mineral reserves, grade and burial form, and draw a "treasure map" for future mining. "The deeper you drill, the more resources you can explore." Wan Buyan said that the marine mineral resources with commercial exploitation potential discovered by human beings are basically within 200 meters of the seabed. Drilling below 200 meters means that China has the exploration ability of full coverage of marine resources in theory.
According to the United Nations Convention on the Law of the Sea, the resources on the high seas are shared by all mankind, and the right to exploit resources generally follows the rule that whoever explores gives priority. Experts in the industry said that "Manatee II" is a "sword" for deep-sea drilling in China, and its sheath has given China an extra technical advantage in the research and development of seabed solid mineral resources.
Overcome multiple technical problems
All key technologies are independently developed, and 125 patents have been obtained so far.
The deep sea pressure is high and the temperature is low. It is very difficult for "Manatee II" to successfully realize a series of operations such as drilling rig retraction, attitude adjustment, pressure sealing, drill pipe and core pipe unloading, automatic measurement and control, etc. in a complex environment.
According to Wan Buyan, "Manatee II" has mainly overcome the technical problems such as full-range pressure-keeping rope coring, drill pipe storage and rapid loading and unloading, intelligent and expert operation system, safe and reliable lowering and recovery of submarine drilling rig.
In the drilling process, it is not difficult to maintain pressure and core in a certain section, but it is difficult to maintain pressure in the whole process. In order to solve this problem, researchers have been tackling key problems for many years. Through remote control of full-hole pressure-maintaining rope coring with large hole depth, the original principle, technology and process of full-length direct sealing and pressure-maintaining coring of core tube have been adopted, and finally the high-efficiency and high-reliability full-hole pressure-maintaining coring with small diameter and large hole depth of submarine drilling rig has been realized.
Wan Buyan said that "Manatee II" is "smart". Researchers have tailored a lot of sensor equipment for it. These sensors combine the team’s many years of offshore field drilling experience. At the bottom of the sea, the drill bit will quickly and automatically judge and adaptively adjust the drilling mode and parameters according to the formation characteristics, which solves the adaptability problem of the submarine drilling rig and the matching coring technology to the complex seabed formation, thus greatly improving the drilling efficiency, coring rate and coring quality.
Thanks to the automatic and intelligent design, one person can complete the operation of "Manatee II" on the mother ship. At the same time of drilling and coring, "Manatee II" can also do "part-time work": in-situ detecting the resistivity and porosity of rocks, taking pictures of rocks around the hole, etc.
In the design and technology of the retractable device of the subsea drilling rig, the team solved the problem that the alignment and closeness of the subsea drilling rig and the retractable device are difficult and prone to impact and collision due to the swaying of the mother ship, and realized the functions of automatically correcting the retractable orientation of the subsea drilling rig in water and automatically holding the subsea drilling rig tightly during the vertical overturning process, thus improving the retractable efficiency of the subsea drilling rig and the safety and reliability of the retractable process.
It is worth mentioning that all key technologies of "Manatee II" are independently researched and developed, and 125 patents have been obtained at present.
The development of "Manatee II" is based on the project of "Deep Sea Key Technology and Equipment Special Project", a national key R&D plan in China. For "Manatee II", the task book has three major objectives, namely, the working water depth is not less than 2,000m, the drilling depth is not less than 200m, and the pressure holding success rate is not less than 60%. To Wan Buyan’s delight, this sea trial fully verified the design performance of "Manatee II" and achieved the mission objectives beyond expectations.
Will continue to optimize in the future.
Challenging geological drilling sampling in 10,000-meter water depth is the team’s next goal.
"Manatee II" was not born, but the result of persistent and continuous research and development for more than 20 years. In 2000, Wan Buyan’s team began to develop deep-sea drilling rigs. Three years later, the team made the first deep-sea shallow core sampling rig in China, and drilled 0.7 meters under the seabed to obtain the first core sample.
In 2010, the deep-sea deep-hole core sampling rig developed by this team pushed the seabed drilling depth to 20 meters. In 2012, the predecessor of Manatee II — — The manatee development project was officially launched. In 2015, the Manatee drilled 60 meters under 3,000 meters of sea water. As a result, China has become the fourth country in the world to have the technology to drill 60 meters in the seabed with a water depth greater than 3000 meters.
Nowadays, many marine scientific research vessels in China are equipped with patented equipment invented by Wan Buyan’s team, and more than 1,000 holes have been drilled in the deep sea.
The development of subsea drilling rig is closely related to the exploration process of seabed resources in China. Wan Buyan told reporters that before 1999, China was unable to develop large-scale deep-sea electromechanical equipment, so it had to rent equipment from abroad. Later, China decided to independently develop deep-sea drilling equipment. Wan Buyan’s team took up the task despite difficulties. They started almost from scratch, constantly groping and bravely tackling key problems.
In recent years, China has paid more and more attention to the research and development of marine technology and equipment. Deep-sea seabed drilling technology has strong radiation to other deep-sea equipment manufacturing technologies and can drive research and development in related fields. Wan Buyan said that more than 10 years ago, almost all the equipment on the scientific research ship was imported, and now the domestic equipment has reached more than 80%, and this proportion will be higher and higher in the future.
Wan Buyan said that the team will further optimize the performance of deep-sea drilling equipment and improve its environmental adaptability, operational performance and intelligence. In addition, they also plan to promote the mass production of "Manatee II" and promote its application in the fields of submarine oil and gas stopes, offshore wind farm construction and engineering geological exploration.
At present, "Manatee II" is still working at sea. The Mariana Trench, with a depth of more than 10,000 meters, has not been drilled by humans. "Challenging geological drilling sampling in 10,000-meter water depth is our team’s next goal." Wan Buyan said.