CBM development in China
|Location||International Geological Congress,oslo 2008|
|Holding Date||27 September 2008|
There are 50 major coal-bearing basins in China and their total resources at < 2,000 m in depth are estimated to be 5.57 TMT; whereas, the associated coal-bed methane (CBM) in-place resources are in excess of 36 TCM. Permo-Carboniferous coals are mainly found in the south and north China marine-related basins and are 3 - 10 m thick, high rank, high gas content, but normally deformed and low permeability. Jurassic and Cretaceous coals are either born in large lacustrine basins in NW China or faulted settings in NE China. Their sequences normally include multiple coals with large thickness, medium to low rank and various gas contents. Tertiary coals are only distributed in small basins of Yunnan and NE China and they are mainly lignite varying in thickness and qualities, as well as gas content.
CBM development in China underwent three stages. Prior to late 1980s, although no surface CBM exploitation occurred underground degassing activities in some coal mines including Fushun, Chongqing and Songzao mines took place for coal-mine safety, with a total country annual volume of underground gas drainage from 100 to 300 million m3 . The period between late 1980s and 2006 is CBM development stage, mainly for resources evaluation, exploration and well testing. During its first ten years, only a few CBM test wells were drilled without significant results. In 1996 the Chinese government formed a monopoly CBM company (CUCBM) to develop CBM with foreign companies, which enhanced exploration activities. By 2006, about 1,000 CBM test and pilot wells were completed within more than 30 basins by domestic and foreign companies; most of these wells are targeted at the gassy, high rank but thin Paleozoic coals in the Qinshui basin of Shanxi Province. However, no commercial gas was produced. The unsuccessful development of CBM in China may be caused by:
(1) poor understanding of local geology and coal reservoir characteristics, (2) inadequate techniques of well completion, stimulation and production, (3) improper application of equipment, and (4) lack of commercial operation experiences.
Driven by coal-mine safety and environment protection, the Chinese government since the latter part of 2006 has started to encourage CBM development in coal-mining areas and to allow coal mines to cooperate directly with international CBM players. Consequently, up to 2,000 CBM wells were drilled since then, which propelled the CBM development and enabled the commencement of a commercial CBM project in Jincheng mining area of the Qinshui basin.
The author believes that China would make great progress in CBM development if more attention could be paid strategically to investigate biogenic methane-dominated lignite and sub-bituminous coal basins and mining areas, and more efforts made on studies of the local geology and on using of more effective drilling, stimulating and draining techniques specialized for the unique characteristics of the target areas.