Feature Articles—December 2009 Issue
MIR Submersibles Explore The Bottom of Russia’s Lake BaikalMIR Submersibles Discover Oil, Gas, Hard Gas Hydrates On the Bottom of Lake Baikal
By Dr. Anatoly M. Sagalevitch
Head
Deep Manned Submersibles Laboratory
and
Dr. Nikolai A. Rimski-Korsakov
Head
Marine Engineering Department
P.P. Shirshov Institute of Oceanology Russian Academy of Sciences
Moscow, Russia
In August, the MIR-1 submersible reached the deepest point of Russia’s Lake Baikal in an expedition that aimed to build on earlier submersible mission data and uncover areas with possible hydrothermal activity or oil and gas resources.
Lake Baikal is the deepest lake in the world with a maximum depth of 1,640 meters, and it contains 23,000 cubic meters of freshwater—about 20 percent of all freshwater on the Earth’s surface. More than 25 million years old, it is also thought to be the world’s oldest lake, with unique geological characteristics.
There is an approximately 7.5-kilometer-thick layer of sediment at the bottom of the lake. Such thick sediments provide favorable conditions for the formation of oil and natural gas. Since water in the lake is quite cold—from the depth of 300 meters to the bottom, the temperature is between 3— and 3.5— Celsius—the thick sediment at more than 350 meters’ depth provides thermobaric conditions for the stability of gas hydrates. These conditions exist on 70 percent of Baikal’s bottom.
Submersibles in Lake Baikal
An expedition to study Lake Baikal using the MIR submersibles, organized by the Russian Academy of Sciences’ (RAS) P.P. Shirshov Institute of Oceanology and the financial company Metropol, began in June 2008 and was completed this September. During these two summers, the MIR submersibles completed 122 dives. The expedition mainly focused on scientific research but also searched for sunken objects mentioned in historical texts.
This expedition was not the first to explore Lake Baikal with submersibles, however. The Pisces VII and Pisces XI submersibles studied the lake in 1977 and 1990 to 1991, collecting a large volume of scientific data, and the recent expedition using the MIRs was intended to build on this information and develop further knowledge about the lake.
Preparing the Expedition
Before the expedition could begin, two problems had to be solved: how to find and equip a support vessel or platform for carrying and launching the MIRs and how to provide proper buoyancy for the submersibles, since they lose buoyancy in freshwater compared with salt water (which they were originally designed for).
A river barge that normally carries coal was chosen as the platform for launching the submersibles. It was ballasted to allow it to safely carry the MIRs and a 100-ton-lifting-capacity crane, and cabins were added to provide living space, laboratories and machine shops. Diesel generators were also added to provide electric power. Within two months, the barge had been converted into a platform called Metropolia and was ready for operations.
Calculations showed that the submersibles would need about 180 kilograms of additional buoyancy in freshwater. Buoyancy was added by removing some heavy parts and substituting lighter equipment, as well as installing additional syntactic foam.
Operations
The MIRs were launched and recovered from the Metropolia platform by the crane, and they were serviced on the surface by motorboats. Underwater communication with the MIRs was provided either from a motorboat or the Metropolia platform, depending on sea state conditions.
Ultrashort baseline systems were used for everyday operations. If operations were performed over several days at one site and required high accuracy, long baseline (LBL) systems were used to navigate the vehicles. During LBL system operations, the geographical coordinates of all samplings, measurements, video images, etc., were fixed with high accuracy on the computer. This was very important for exact mapping of the areas explored by the MIRs.
Geological Research
Visual observations from the MIRs allowed the team to obtain new data about tectonic faults on the western and eastern slopes of the lake. They have similar constructions, looking like vertical fault breaches alternated with horizontal terraces, and they are covered by sediment. These constructions are very similar to the slopes in rift valleys in the ocean. The deepest area in the middle of the lake is practically flat and covered by a thick layer of sediment.
Oil and Gas Research
The most interesting and important result of the mission was the discovery of oil and gas discharges on the bottom and quite large deposits of hard gas hydrates that looked like ice hills covered by thin layers of sediment.
Bitumen Hills. Oil and gas seeps were discovered in the middle part of the lake at the Mys Gorevoy Utes site. At a depth of 900 meters, the MIRs discovered a sunken portion of the seafloor that had a rise 10 meters high and 50 meters in diameter at its center. Small conical hills 1.5 to two meters high with a light brown coloring were found on the top of this rise.
The lower parts of these hills were made of a dark brown boggy matter that looked like bitumen. On the top of the hills, the MIRs discovered vertical pipes that looked like droppers. Small, separate drops of oil seep through the droppers every 20 to 30 seconds.
The MIRs took samples of the pieces of bitumen on the small hills, and analysis showed that the organic matter was made of paraffin oil bitumen consisting of 80 to 85 percent carbon, 10 to 12 percent hydrogen and about two percent mineral matter.
On the bitumen hills and droppers, a very high density of marine life was observed—the MIR operators saw as many as 100 animals within one square meter. It was established that most of these species were known to live in the deepwater zone of Baikal, but the density of biomass in the areas with oil and gas discharges was much higher than usual in the deep zones of the lake. It was hypothesized that the animals there feed on methanol-oxidizing bacteria and therefore do not depend on organic matter from the surface.
Oil Balls. Separate accumulations of liquid oil in the form of balls one to 1.5 centimeters in diameter were observed on the flat bottom several hundred meters from the droppers. They are the result of the oil seeping through the sediment.
The oil balls appeared on the bottom without any periodicity and immediately rose upward. Many of them joined together in the water column and appeared on the surface of the lake as large spots of oil.
Gas Hydrate Hills. Other hills were discovered with dimensions of about 20 by 15 by 20 centimeters. One of the submersibles tried to bring a sample of one of these to the surface, but during the ascent from 360 meters, the gas began to discharge from the sample and the vehicle went up in a cloud of gas bubbles.
Analyses of the sample showed that the hard contents disappeared and only liquid matter—oil and water—was left. It was concluded that the small, sharp hills were made of hard gas hydrates.
Then in July, a surprising discovery of hard gas hydrate deposits was made. In the middle of Lake Baikal at the St. Petersburg site, the MIRs discovered a chain of hard gas hydrate hills six to eight meters high and 40 to 50 meters in diameter.
These hills were covered by a thin layer of sediment and, at first glance, looked like most of the hills at the bottom of the lake. But when the MIR attempted to take a sample from them, the material was found to be incredibly strong. The submersible pilot had to use not only the full strength of the MIR’s manipulator arm (up to 100 kilograms), but the mass of the vehicle as well to break off a piece of the hill. This time, a special hermetically sealed container was constructed to lift the gas hydrate sample to the surface for study.
Conclusions
The use of the MIR submersibles for scientific research on Lake Baikal confirmed that manned submersibles are irreplaceable tools for detailed oceanographic research.
The finding of large deposits of gas hydrates in a freshwater lake is one of the greatest discoveries of modern underwater research. Gas hydrates had previously been found only in small quantities in freshwater sediment. These monoliths on the bottom of Lake Baikal are the first of their kind to be uncovered.
Acknowledgments
The author would like to recognize the Limnological Institute, Siberian Branch, of RAS; the Baikal Institute of Nature Management, Siberian Branch, of RAS; and other organizations that took part in the scientific research conducted on this MIR expedition.
One of the principle designers of the MIR submersibles, Dr. Anatoly M. Sagal-evitch is the head of the Deep Manned Submersibles Laboratory at the Russian Academy of Sciences’ P.P. Shirshov Institute of Oceanology. He directs the deep-dive submersibles program and has led more than 30 worldwide expeditions, logging more than 3,000 hours as a submersible pilot.
Dr. Nikolai A. Rimski-Korsakov is the head of the marine engineering department and the Sonar Observation Labora-tory at the Russian Academy of Sciences’ P.P. Shirshov Institute of Oceanology. He leads numerous projects concerning scientific research and search operations in the ocean.
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