采矿专业毕业设计外文翻译--关于煤层沼气的一些经常出现的问题-采矿工程(编辑修改稿)

采矿专业毕业设计外文翻译--关于煤层沼气的一些经常出现的问题-采矿工程(编辑修改稿)内容摘要：

top of the seam. However, sometimes the water level drops into the coal seam. Water moving from the coal seam to the well bore encourages gas migration toward the well. As this water pressure is released, the gas will rise and is separated from the water and be piped away. How much methane gas do they estimate will be extracted from the Powder River Basin? Estimates on the amount of methane gas in the Powder River Basin vary and the estimates are often recalculated. There are several methods to estimate the amount of recoverable gas from a coal seam。 all have varying degrees of accuracy and inaccuracy. According to the U. S. Geological Survey the amount of recoverable CBM from the Powder River Basin ranges from 168。 C trillion cubic feet of gas. The Wyoming Oil and Gas Conservation Commission estimates trillion cubic feet of recoverable CBM in the Powder River Basin of Wyoming alone. The Montana Bureau of Mines and Geology and the . Department of Energy have separately estimated between 168。 C trillion cubic feet of recoverable CBM in the Powder River Basin ofMontana. The Environmental Impact Statement for coal bed methane development in the Powder River Basin of Montana reports trillion cubic feet of recoverable gas. How do they estimate the amount of methane gas which will e from a region underlain by coal? There are two popular methods for estimating recoverable methane gas from a coal method requires estimating methane reserves by boring to the top of the coal seam, then extracting a core from the coal. The amount of methane recovered from the coal core is used to estimate gas content per unit volume of coal. If a number of cores are drilled and methane gas release is observed, one can estimate the amount of gas available in a region. The limitations to this method are: 1) there is much disturbance to the coal seam core before gas release is measured。 2) it is expensive and 3) not every region of potential CBM development has been drilled and explored. Another method of estimating the amount of methane in a region underlain by coal is through a series of calculations based on information we already know about the coal in the region and the feasibility of CBM development. What are the current management practices for disposal of the CBM product water? Currently, CBM product water in the Powder River Basin is managed by the following methods:  Discharged into a stream channel Although direct stream discharge is no longer permitted on new wells, existing operations were !176。 grandathered!177。 and are still discharging directly into streams. Also, proposals are being advanced to allow regulated discharges during certain flow conditions.  Impounded 168。 C This ethod involves constructing a pond in which CBM product water is stored or allowed to infiltrate to the subsurface. There are several terms fo。