21.03.2008
PROSPECTS FOR COALBED METHANE RESERVES DEVELOPMENT OF RUSSIA
Major coal reserves as well as its associate - methane (methane can be measured alike the world’s traditional gas reserves) are concentrated in the explored and perspective coal basins. Therefore, such basins should be developed as coalbed methane basins aimed at complex stage-by-stage exploration along with advanced large-scale methane production.
Methane is the main natural gas component of coal beds not affected by the gas weathering. Methane concentration in coalbed natural gas is at 80-98 per cent.
The scientifically grounded definition for the role of coalbed formation as the largest methane concentration areas in the crust opens new prospects to increase hydrocarbon reserves. Methane, which is the most dangerous coal associate, becomes an essential mineral deposit for independent production or associated extraction in mines within the complex stage-by-stage coalbed gas field operation.
Key Elements of Coalbed Methane Field Development
It is important to notice that not all coal is suitable for methane production. Long-term brown coal fields are poor with methane. Anthracite is marked by high gas concentration but it is impossible to extract it because of the high density and quite low field openness. Coal located in the middle between brown coal and anthracite is the most perspective for methane production. This kind of coal is located in the Kuzbass basin.
There are two totally different coalbed methane production methods such as mining and borehole methods. The mining method produces methane in small amount, mainly for the needs of hydrocarbon enterprises. The usage of this method is difficult because of significant fluctuations of incoming gas and methane concentrated in it. Methane extraction through the specially drilled mines provides an opportunity to produce gas on industrial scale.
The peculiarity of coalbed methane fields is that unlike traditional fields where natural gas in free condition is concentrated in porous reservoir, methane in coal beds is occluded with coal or pinched in the smallest splits creating conditions for desorption. To this effect special technologies are applied including hydraulic fracturing of coal and stratal water pumping. From the moment of pump startup well yield starts to grow while depression increases and after a few months later reaches its maximum level and then smoothly decreases within few years. Such well behavior radically differs coalbed methane fields from traditional fields where natural gas deposits have a maximum meaning during a productive bed opening and decreases during the field exhaustion and bed pressure decrease.
Russian Coalbed Methane Reserves
Russian forecasted coalbed methane reserves are estimated at 49 tcm of gas corresponding to approximately one fifth of forecasted natural gas reserves of the country.
Among the Russian basins special attention is paid to the Kuzbass basin. The Kuzbass basin is the largest coalbed methane basin in the world with an opportunity to produce methane on a large-scale. Forecasted extracted coalbed methane reserves are estimated at 13 tcm of gas. Said coal and methane reserve estimation corresponds to 1800-2000 meters. Big coal basin depths maintain in a distant prospect large amount of methane, which is estimated at 20 tcm of gas.
The Kuzbass basin reserve base provides an opportunity for large scale methane production as an independent mineral deposit.
The Pechora basin is the second after the Kuzbass largest basin containing methane reserves. Forecasted coalbed methane reserves in the Pechora basin are estimated at nearly 2 tcm of gas.
International Coalbed Methane Production Experience
The necessity, opportunity and economic expediency for large-scale coalbed methane production is proved by the experience of coalbed methane field development in the USA, which has a leading position in the world due to the new gas industry development level. In the USA methane production rapidly increased from 5 bcm in 1990 to 27.6 bcm in 1995 and in 2005 it reached 50 bcm, which is nearly 8 per cent out of the traditional gas production in the USA.
Additionally, Australia, Canada and Columbia produce coalbed methane.
Modern Experience of Coalbed Methane Production in Russia
At present in Russia coalbed methane is extracted only as an associated mineral deposit at the existing mines by the mining decontamination systems including mines drilled from the ground. In recent years nearly 0.5 bcm of gas was annually extracted at the Pechora and Kuznetsk basins.
As apposed to coalbed fields of the San Juan basin (USA) where gas is extracted from three coal beds with total capacity up to 35 m distributed within the 100 meter interval, in the Kuzbass basin the total coal bed width in the separate areas reaches 70 m but reserves are distributed within the 600 m interval concentrating a lot of coal sheds where only 7-10 could be industrially developed. Such geological peculiarities forbid to apply worked out American technologies developed within almost 15 years (from 1977 to 1992).
In 2003 Gazprom started to execute the project on evaluating opportunities of industrial production of coalbed methane in the Kuzbass basin. In the Erunakovsky region (Kemerovo Oblast) in the Taldinskaya area (Kuzbass) 4 test wells were drilled where in 2004 first gas was received. Additionally, coalbed methane reserve calculation techniques were prepared, developed and methane production technologies were tested, regulatory basis was created, which provided coalbed methane reserves exploration and environmental security for coalbed methane fields.
At present wells are in a pilot operation, which proves an opportunity for coalbed methane production in the Kuzbass basin.
Gazprom purchase a control stake in Geologopromyslovaya Company Kuznetsk (GPK Kuznetsk) in June 2007. GPK Kuznetsk holds license for coalbed methane prospecting, exploration and production within the Yuzhno-Kuzbasskaya Group of coal fields containing methane reserves in amount of 6.1 tcm. This purchase enables Gazprom to start development of coalbed methane production as a new sector of the Russian fuel and energy complex, expand hydrocarbon reserve base and sales markets and organize large-scale gasification of the Kemerovo Oblast and Southern Siberia.
Objective Reasons for Coalbed Methane Production in Russia
Favorable geological peculiarities and terms of gas presence in the Russian coal basins is an objective condition to organize in the Kuzbass basin and other coal basins a large-scale production of methane as an associated and independent mineral deposit.
Coalbed methane production in the Kuzbass basin is stipulated by the following factors:
Among the Russian regions, which are not supplied with gas in sufficient amount, a number of hydrocarbon region could totally cover gas needs due to large-scale coalbed methane production. This is relevant to the Kemerovo Oblast where it is possible to provide annual commercial production up to 15-17 bcm.
Additionally, gas production and usage will improve the environmental situation in hydrocarbon regions, decrease gas security for coal production in future wells and create new working places in the gas industry and gas processing enterprises.
The most perspective areas for methane production in the Kuznetsky and Pechora basins are located close (75-200 km) to potential gas consumers. The closeness of methane production fields to consumers avoid costs for gas compression and construction of high-pressure gas mains making coalbed methane in coal-production regions the most perspective mineral deposit among non-traditional energy sources.