Promising coal basins and those under development contain a significant part of the global coal resources accompanied by methane. Coalbed methane (CBM) resources are commensurate with the world’s conventional gas resources. Therefore, such basins shall be considered as the CBM basins that are subject to comprehensive phased development with preliminary large-scale methane production.
Methane is the basic component of natural gases contained in coal beds, which are not influenced by demethanization processes. Methane concentration in the mixture of coalbed natural gases reaches 80–98 per cent.
Scientifically proven assessment of the coal-bearing formations’ role as the major sources of methane and locations for its accumulation in the Earth’s crust opens up new and wide horizons in building up the resources of hydrocarbon gases. Methane, being a most hazardous by-product of coal, is becoming a valuable natural resource to be produced from coal mines as an independent commercial product or as a by-product, in the process of comprehensive phased development of gas-bearing coal fields.
Peculiarities of CBM fields development
It should be noted that not every type of coal is suitable for methane production. Thus, long-flaming brown coal fields are featured with low methane content. Anthracite coal is characterized with high gas content; however, it can not be recovered due to high density and very low permeability of the deposit. The coals that fall somewhere in between the brown coals and the anthracite coals are attributable to the most favorable ones for methane production. This kind of coal is deposited in Kuzbass.
There are two essentially different ways of CBM recovery: from coal mines (existing mine take areas) and from CBM wells. CBM recovery from coal mines is an integral part of the deep mining technique intended for methane emissions lowering and its explosion prevention. When produced from coal mines, the amount of CBM is small and is mainly used for technological purposes of coal producers. This technique is impeded by considerable fluctuations in the volume of the gas-air mixture received and methane concentration in it.
Commercial CBM development is associated with specific technologies of gas recovery intensification.
Russian forecasted CBM resources
Forecasted methane resources of the major coal basins in Russia are estimated to contain 83.7 trillion cubic meters making up approximately one-third of the country’s forecasted natural gas resources.
Kuzbass is distinguished from the rest of Russia’s coal basins and may reasonably be considered as the world’s largest among the explored CBM basins providing tangible and great opportunities for large-scale methane production. The basin’s forecasted methane resources are estimated at 13.1 trillion cubic meters.
These estimates are given for the coal and methane resources deposited at a depth of 1,800–2,000 meters. Deeper coal deposits of the basin keep the immense amount of methane estimated at 20 trillion cubic meters that seems to be sufficient in the long run.
The resource base of Kuzbass ensures large-scale production of methane (beyond the mine fields) as a separate natural resource.
International practice of CBM production
Necessity, possibility and feasibility of large-scale commercial CBM production is confirmed with the practice of CBM fields development in the USA, the world’s leader in terms of the ‘new gas industry’ advancement. Methane production in the USA has upraised from 5 billion cubic meters in 1990 to 27.6 billion cubic meters in 1995 reaching 56 billion cubic meters in 2009 which makes some 10 per cent of the conventional gas produced domestically.
CBM is commercially produced in Australia, Canada and China.
Current status of CBM production in Russia
Until recently, CBM was extracted in Russia as a by-product from the existing mine take areas only through the mine degassing systems incorporating the wells drilled from surface. In the recent years, these systems yielded some 0.5 billion cubic meters of methane per annum in the Pechorsky and Kuznetsky basins.
In 2003 Gazprom launched a project to estimate the possibility of commercial CBM production in Kuzbass. 4 pilot wells were drilled in the Yerunakovsky District, Kemerovo Oblast in the Taldinskaya area of Kuzbass and a test site was established where the first gas inflow was detected in 2005–2008. In addition, methane production technologies were elaborated and approbated, a CBM reserves estimation method was developed, and a regulatory basis was shaped providing for CBM resources development and for environmental safety of CBM fields. Over 30 Russian patents were obtained for the entire technological cycle – from CBM exploration to utilization. Two-thirds of the equipment items used during the pilot project execution were made in Russia. The Taldinskoye field forecasted resources are estimated at 95.3 billion cubic meters.
Acquisition of a controlling stake in Prospecting Company Kuznetsk (holds the license for CBM prospecting, exploration and production within the Southern Kuzbass group of coal fields containing 6.1 trillion cubic meters of gas) in June 2007 and raising it to 100 per cent in May 2008 enables Gazprom to start shaping a new CBM production sector of Russia’s fuel and energy complex, to enhance the Company’s own hydrocarbon feedstock base and sales markets, as well as to arrange large-scale gasification of the Kemerovo Oblast and southern regions of Siberia.
In 2008–2009 eight wells (one parametric well and seven exploratory wells) were drilled in the eastern part of the Taldinskoye field. At present, pilot operation of the exploratory wells is underway and the produced gas is supplied to gas filling stations. Pilot operation will result in obtaining the parameters required to make CBM reserves commercial; as well as in approbating the well completion, gas extraction and treatment technologies needed for top-priority areas and prospects development in Kuzbass. Exploration and appraisal activities have been initiated in another prospect – the Naryksko-Ostashkinskaya area.
It is planned to maintain steady CBM production in the amount of 4 billion cubic meters per year in Kuzbass.
Objective reasons for CBM production in Russia
Favorable geological features and CBM occurrence in Russia create reasonable preconditions for launching, primarily in Kuzbass, and subsequently in other coal basins, large-scale production of methane as a separate natural resource.
CBM production in Kuzbass is feasible due to the following factors:
- availability of large-scale CBM deposits in Russia;
- availability of state-of-the-art technologies for commercial CBM production that have been widely used internationally in the recent years;
- Russia’s sci-tech potential and capability to coordinate and perform scientific research on the matter.
Among Russia’s regions insufficiently supplied with gas fuel, a number of coal producing regions could fully satisfy their gas demand owing to large-scale CBM production. In addition, gas production and utilization will improve the environmental situation in the coal-mining regions, reduce the gas explosion hazard associated with coal production from future mines and create new jobs at gas production and processing facilities.