Shale rock, composed mostly of mineral (calcite, dolomite, hydromicas, montmorillonite, kaolinite, fieldspar, quartz, pyrite, etc.) and organic substances, was formed 450 mln years ago on a sea bottom from plant and animal remains, and does not belong to the group of valuable mineral resources. It is characterized by relatively low heat transfer--twice lower than coil and four times lower as compared with oil--and high slag production. However, shale has long been used as a fuel, especially in places where high-quality fuel was lacking. Today shale gas is strengthening its position as a competitor to customary hydrocarbons.

This problem was also a focus point at the field meeting of the RAS SB United Academic Council for Power Engineering, Machine-Building, Mechanics and Management, held in mid-July of 2013 at the recreation center "Sosnovy Bor" of the Institute of Thermal Physics named after S. Kutateladze (Novosibirsk) to discuss resource, technological and economic aspects of shale revolution and determine the position and role of our country in it. Acad. Vasily Fomin, Chairman of the Council, and Vitaly Zinovyev, Academic Secretary and Cand. Sc. (Phys. & Math.), in detail reviewed the delivered reports in the Science in Siberia newspaper.

As the authors stated, according to some forecasts, global reserves of shale gas are exceeding 700 trln m³ and are larger than the reserves of traditional natural gas. They are mostly (50 percent) located in China, USA, Argentina and Mexico. As for the European countries, commercial basins are located in France, Poland, Germany, Ukraine, and in the southern part of the North Sea. In the USA, after introduction of efficient production technologies, the share of shale gas in the overall natural gas production increased from 2 percent in 2000 to 37 percent in 2011. If this dynamics keeps developing, after 2020 the US will be able to stop importing natural gas and by 2030 start exporting it. According to experts, these factors have already caused a global cutdown of prices on blue fuel.

Sergei Senderov, Dr. Sc. (Tech.), (RAS SB Institute of Power Systems named after L. Melentyev, Irkutsk) believes that economic indicators of shale gas production depend on geological specifics of deposits, cost of the equipment, availability and quality of infrastructure, and dynamics of changes of daily production volumes during operation of wells. According to Senderov, factors that have a positive effect on future development of shale gas deposits include proximity to target markets,

Types of natural gas: conventional (A), shale (C), from hard sand (D), casing-head (F), coal bed methane (G). (B--insulating layer, E--oil, H--land surface).

capacity of fields, the eagerness of authorities to curtail dependence on imported fuel and energy reserves; as for the negative factors, the most significant are high production costs, impossibility to transport shale gas to long distances, quick depletion of deposits, and high environmental risks caused by a specific production technology known as fracturing or hydraulic fracture of a stratum.

According to the review, the fundamentals of theoretical justification of fracturing were developed in 1955 by the outstanding engineer and mathematician Acad. Sergei Khristianovich and Yuri Zheltov, Dr. Sc. (Tech.), who substantiated the technology of hydraulic fracture of an oil-bearing formation. It consists in the following: injection of water-based gel into a well builds an excess pressure that is greater than that of the formation. As a result, the rock breaks down forming fractures that get bigger due to the continued injection of the liquid as well as proppane and other chemicals to fix the fractures open after pressure relief. Ecologists believe that injection of chemical agents to extract natural gas from shale rocks may lead to contamination and an essential change of composition of soil waters. Besides, water will carry dangerous substances--benzene, arsenic and radioactive materials--to the surface. In this respect, EC countries-France, Romania, Bulgaria, etc.--have already prohibited surveying of mineral resources using fracture technology.

However, as the authors say, partial replacement of coal by gas and increased import volumes to the European countries may weaken the position of our country in the competition in the power markets of Europe and the Asia-Pacific Region. The problem of shale gas production has been put in the center of attention in China possessing significant reserves of shale hydrocarbons (up to 20 percent of the global reserves), which can call in question the expediency of construction of gas pipelines from Eastern Siberia to China and drastically change the present-day structure of markets in South-Eastern Asia. According to the scientists, in this context

48 shale fields (colored brown) in 38 countries (colored white), included in the report of the U.S. Energy Information Administration.

it is highly necessary to restructure national economy, which is intended to reduce the share of power-consuming technologies and increase outputs of advanced technologies.

The resource potential of shale gas and oil reserves in our country was evaluated by the RAS Corresponding Member Vladimir Kashirtsev (RAS SB Institute of Oil and Gas Geology and Geophysics named after T. Trofimuk, Novosibirsk). According to him, substantial deposits are located in the East European Craton, in Olenyoksky, Baltic and Volga basins. In Western Siberia shale oil is concentrated mostly in Bazhenovskaya suite*--in almost impermeable rocks lying in between traditional oil-bearing horizons. Basically, it is a national analog of the famous deposit Bakken in North and South Dakota (USA). Some experts believe that oil reserves in Bazhenovskaya suite, comparable to oil and gas potential of traditional fields in Western Siberia but not yet put on balance, should be treated as highly promising raw materials. To improve shale production technologies and prove the existing model of geological structure, it is planned to drill 3-5 specially designed horizontal wells and make numerous hydraulic fractures of the formation.

* Bazhenovskaya suite--a series of rocks identified in Western Siberia at a depth of 2 km and covering over 1 mln m³. besides, it has relatively small thickness--20-30 m.--Ed.

Vladimir Kuznetsov, Dr. Sc. (Phys. & Math.), (RAS SB Institute of Thermal Physics named after S. Kutateladze, Novosibirsk) believes that one of the main current problems of production of shale gas and oil is absence of new breakthrough technologies enabling to significantly reduce production costs. In this context, injection of water into fractured oil-saturated layers can be one of them, even though it is quite difficult taking into account possible flooding of production wells. But, as Kuznetsov stated, this problem can be solved by way of reducing water consumption and accelerated capillary impregnation of rock blocks. Moreover, the RAS SB scientists have a vast experience in this field.

The report also proposed a solution to the problem of a low-tonnage production of liquid fuel by way of conversion of shale gas to synthesis-gas in microreactor units, provided drawings of such facilities and methods of production of highly-active catalysts with optimal structural and dimensional characteristics. Engineers of the Institute of Thermal Physics developed basic design principles for converters--devices for casing-head and shale gas processing based on micro- and nanotechnologies, multicomponent nanostructures showing high efficiency of conversion of methane to synthesis-gas and hydrogen. These structures were used to create prototypes of energy-saving

Shale gas mining technology: 1--drilling of a vertical well; 2--drill deviating from the vertical; 3--drilling of horizontal well; 4-under pressure a mixture of sand, water and chemicals get into the well; 5--hydraulic fracture of the layer; 6--gas collected in the pipe.

processors used to produce liquid fuel from casing-head and shale gas.

Vladimir Likholobov, RAS Corresponding Member (RAS SB Institute of Problems of Hydrocarbon Processing, Omsk), reviewed in detail conventional technologies of chemical processing of methane as the main component of shale gas based on the primary Fischer-- Tropsch process* to produce synthetic hydrocarbons used as a lubricant oil or fuel.

Likholobov focused on the aspects of a complex natural gas pyrolysis technology resulting in production of light alkenes (ethylene hydrocarbons) and components of motor fuels. Together with his colleagues he studied phases of pyrolysis of methane to acetylene and ethylene, synthesis of propylene from ethylene, oligomerization (chemical conversion) of olefins to polymer-gasoline. According to the speaker, this technology makes it possible to produce 680 kg of propylene, 75 kg of aromatic hydrocarbons, 36 kg of liquid fuel and 88 kg of hydrogen from 1 t of methane. However, additional studies are required to carry out pyrolysis of natural gas.

* Fischer--Tropsch process--a multistage chemical reaction allowing to produce the so-called synthesis-gas (CO+H₂) from hydrocarbons; then it is converted to methanol or synthetic hydrocarbons used to produce motor fuels. This technology was actively developed in the middle of the last century for coal processing, today it is widely used for gas processing.--Ed.

Likholobov pointed out that one-stage synthesis of propylene from ethylene is of high practical interest. Thus, the institute has developed catalysts based on the oxides of nickel and rhenium and proved the possibility of production of a combustible gas with 80 percent efficiency out of theoretical potential. The final part of the report was dedicated to prospects of a low-tonnage technology of natural gas processing to carbon materials, in particular, production of high-dispersed technical carbon widely used as a reinforcing agent to produce resins and other plastic materials.

Acad. Mikhail Epov from the RAS SB Institute of Oil and Gas Geology and Geophysics (Novosibirsk) drew attention of the participants of the session to the probability of occurrence of new global unconventional resources, like shale fuel, that can change the world situation. First of all, he meant water-dissolved gases and gas hydrates, reserves of which, according to the estimates, exceed reserves of shale gases by an order of magnitude or by a factor of 10². As Epov pointed out, water-dissolved gases are localized not in a mineral-organic rock complex, but in interstitial waters. Hydrogen "catching" mechanisms typical of such formations drastically differ from the process of accumulation of gases in conventional deposits.

The idea of practical application of water-dissolved gases was formulated in our country as early as 1974. Then scientists proposed to transfer high-pressure gas-saturated waters to upper relatively low-pressure horizons. They also considered other opportunities: salinization of extremely gas-saturated underground waters by way of bypass of brine to lower horizons and breakdown of phase balance to accelerate degassing of waters resulting from superpowerful in-depth blasts.

According to Epov, the main problem of development of water-dissolved gas deposits lies in transportation of underground waters to the ground surface, where they can be degassed by atmospheric pressure, and in disposal of brine. These issues need much money to be solved, but it is worth the effort. For example, pressure decrease in edge waters at Gubkinskoye OGC field (Purovsky District, Yamalo-Nenets Autonomous Area) by 2-3 MPa will result in gas release in the volume of 150-200 bin m³, which means that, according to the Acad. Epov, we can and must consider the opportunity of industrial use of water-dissolved gases located in geopressured zones.

Acad. Vasily Fomin who closed the session of the RAS SB Academic Council for Power Engineering, Machine -Building, Mechanics and Management Processes pointed out: in the near future the power balance and spheres of influence will depend on science-driven technologies of production and processing of natural power resources, not on absolute reserves of natural wealth. In this situation, our task is to develop fundamental studies as an applied base for the development of such technologies and their practical implementation.

V. Fomin, V. Zinovyev, Shale Gas, Water-Dissolved Gas-Possible Prospects of Use, "Science in Siberia" newspaper, No. 32-33, 2013

Illustrations from Internet sources

Prepared by Marina MALYGINA