The matching of gas production curve characteristic and reservoir conditions in vertical coalbed methane wells

The matching of coalbed methane(CBM) production curve type and geological conditions directly affects the gas production. Based on dividing gas production curves types of vertical CBM wells in the southern block of Shizhuang in Qinshui basin over 4 years, the characteristics of gas production curve were analyzed. The matching of gas production curve with reservoir parameters was further analyzed. The paper discovered and divided the gas production curve into four types:type of fast rising of single peak, type of stable rising of single peak, bimodal type of being low later and bimodal type of being high later. The original permeability, dynamic condition, and fracturing effect control the characteristics of gas production curve. The reservoir parameters of the type of fast rising of single peak has high gas content(>12 m³/d), high permeability(>0.1×10^-3 μm²), high specific value of critical desorption pressure and reservoir pressure(>0.4). This kind of curve is easy to cause sharp drop of gas production in the peak period. The type of stable rising of single peak is applicable in a wide range of reservoir conditions. Gas production of bimodal type of being low of is usually lower than other types. The gas production curve is poorly matched to the reservoir characteristics. The bimodal type of being high later is suitable for wells with better fracturing effect and have lower requirements for reservoir parameters. Gas production growth rate of the back peak determines the gas production effect. On the basis of above analysis, the reservoir is divided into seven types, which has important guiding significance for the implementation of the "one well and one scheme" drainage system in the study area and its adjacent blocks.