Method and application of diagnosis of low productivity damage of CBM wells

Coal reservoirs differ from conventional reservoirs, are easily damaged and the damage factors are complex. Massive papers focus on CBM damage mechanism, but fewer studies on pollution types and stimulating measures. This paper studied various factors influencing CBM and water production in a block of Qinshui basin from angle of geology, engineering and drainage, and established the typical production curve model to determine reservoir judgement method of damage types of low production wells, layer and well selection standards for reservoir with big yield-increasing potential to carry out second reconstruction. The results proved that factors influencing CBM wells productivity such as geology, engineering and drainage can't be ignored because their damages are huge, factors such as collapse column, fracturing fluid soaking time, abnormal fracturing operation, drainage time interval, production efficiency and liquid drop speed have big damage to coal reservoirs. Determination of major factors of reservoir damage and establishment of typical curves offer references for reservoir diagnosis, and have important guiding significance for reconstruction of selected wells and layers with low productivity and low efficiency.