Analysis on Production of Coal Bed Methane Considering the Change in Permeability of Coal Rock

Abstract

Based on the mechanism of migration of the coal bed methane (CBM), and taking into account the deformation of the coal rock during the process of CBM production was also taken into account, a coupled mathematical model considering the interaction of solid and fluid for methane extraction was built. The coal gas extraction of JINcheng coal mine was taken as an example, some typical coal sample was chosen to test the permeability under different confining pressure. The curve for permeability of coal rock versus effective stress under different confining pressure was obtained, a numerical model considering the variation of permeability for methane extraction was set up. The influence of deformation of coal rock on the gas production was simulated and analyzed. The simulation results indicate that the productivity curve considering deformation of rock is closer to the actual production data, at the initial stage of production, the gas rate is less than the case without considering deformation of rock, but the time of stable yield will last longer, and this matches the actual methane extraction, therefore, we recommend that the deformation of coal seam should be considered during the prediction of methane production for JINcheng coal mine.

Selection of Compatible Coal Seam for Methane Drainage Operation Based on Uncertain Geological Conditions: A Hybrid Fuzzy Approach

“…After calculating the fuzzy weights of each criterion using the FCM method, all fuzzy weights are transformed into a nonfuzzy (11) [63]:…”

“…A few studies have been done on the evaluation, classification, and ranking of the coal seam for the MDA during the coal mining operation. Earlier research has focused on the problems such as the effect of factors on the methane drainage efficiency [10], production rate of the CBM [11], optimization of boreholes drilling pattern [12,13], and environmental problems of the methane drainage operations [14,15].…”

Study of Cyclic Fracturing in Vertical CBM Wells

“…The increase of production for CBM wells depends on stimulated reservoir volume (SRV) and desorption rate of methane gas. In comparison with sand reservoirs, fractures are shorter and wider in CBM reservoirs, thus, the conventional fracturing technique should be improved to attain large SRV [6,7]. Natural fractures and bedding planes are plenty in CBM, so how to take advantage of them is an important consideration in CBM fracturing.…”