Main Factors Influencing High Yield of High-Rank CBM in Chengzhuang Block, Southern Qinshui Basin
杨克兵 王海潮 王君 陈辉娜 符康
中文关键字：沁南盆地 高煤阶煤层气 高产井 主控因素 排烃期 封堵条件
英文关键字：Southern Qishui Basin, high-rank CBM, high-productivity well, main influencing factor, duration of hydrocarbon discharge, plugging condition
In China, most coal-accumulating basins went through complex evolution history and some structures formed in the late period were severely damaged. And lots of high-rank coal reservoirs also underwent multiple-stage tectonic evolution and obvious metamorphism, resulting in strong heterogeneity, and low yield of coalbed methane (CBM) or difficulty in its exploitation. Even though previous research focused on the analysis on such factors as structure, deposition, and hydrodynamics, many problems including low proven rate and low utilization rate of production capacity have not been solved very effectively. So, according to some dynamic and static data from high-productivity wells in Chengzhuang block, Southern Qinshui Basin, combining with development characteristics of surrounding blocks, we analyzed common features of these kinds of wells. Results show that (1) the main factors influencing high yield are developed microfractures and high permeability in coal reservoirs; (2) another important factor is rich free gas in these reservoirs; and (3) there are other factors including reservoir thickness, gas content, tectonic movement, and hydrodynamics. Our study also demonstrates that CBM in Chengzhuang block is controlled by sedimentation, and plugging condition during hydrocarbon discharge is the key factor influencing high productivity. Good plugging condition is conducive to improving petrophysical property and generating more free gas, which can provide material foundation for high yield. This viewpoint presented gives geologic evidence for optimizing high-yield blocks, and is significant for evaluating sweetspot of tight reservoirs.