The Research Of Accumulation Of Low Rand Coldbed Methane In The North-West Of China

In China, the exploration and development of coal-bed gas have been mostly focused on middle～high coal tier coal-containing area, While the exploration and development of low coal tier coal-containing is poor. Because the differences between low coal tier coal and high coal tier coal on physical and chemical characters,pore constructure, so it is quite important and significant to research the reservoir character and the mechanisms of gas accumulation and reservoiring.Based on domestic and foreign coal-bed gas research status quo and development, this lecture has analyzed the cause of low coal tier coal-bed gas in Northwest China, pointed out that low coal tier coal-bed gas in China is mostly secondary biogenic origin. The abilities to contain gas,absorb,desorb also have been analyzed. By analyzing the coal sample desorption data from the lab and production data, it has brought out different desorption patterns of high and low coal tiers. By analyzing the organic geochemical and hydrogeologic characteristics of low coal tier coal, the reservoir characters of high coal tier coal has been compared with and we have discussed the differences.By taking typical low coal tier basens—Junggar and Turpan-hami in Northwest China for example, this lecture has analyzed such basic and reservoir characters as reserves,geostress and pointed out that the most favourable strata series for coal reservoirs reservoiring in Northwest China are BaDaoWan formation and XiShanYao formation, it also has analyzed their combination type of Source-Reservoir-Cap and reservoiring pattern. The Junggar basin were basin-margin slope alluvial system tranquil flow,late stage biogenic gas reservoiring pattern while the Turpan-Hami basen being in-basin depression coal-bed gas reservoiring pattern. The reservoirng differences of low coal tier reservoir and high coal tier reservoir also has been discussed.