应力敏感性条件下储层参数对煤层气井单相流段产水量影响研究

Effect of Reservoir Parameters on Water Yield of Single Phase Flow in Coalbed Methane Wells Under Condition of Stress Sensitivity

建立了考虑应力敏感性条件下煤层气井单相流段产水量模型,并依据研究区块某区块储层参数对2口煤层气井解吸前产水量数据进行拟合,在此基础上模拟了应力敏感性系数、渗透率、表皮系数和井筒半径对产水量的影响。结果表明:应力敏感性对煤层气井解吸前产水量变化具有重要影响,应力敏感性不同,产水量曲线形态不同;对特定煤层气井,存在最优井底流压值使日产水量最大;应力敏感性系数越大,产水量越少;应力敏感性系数大于1时,出现无效降压段,应力敏感性系数越大,无效降压段越长;日产水量随着渗透率、井筒半径的增加而增加,渗透率越高,井筒半径越长,压裂液返排效率越高,压降扩展范围越大;日产水量随着表皮系数增加而降低。

We established the water yield model for single-phase flow under the consideration of stress sensitivity of coalbed methane wells, then completed the history matching of water yield data of two wells on the basis of the basic physical parameters of a block, and then simulated the effects of four parameters such as stress sensitivity coefficient, permeability, skin factor and wellbore radius on water yield. The results show that the stress sensitivity has important influence on the change of the water yield before the desorption of coalbed methane well, and the water yield curve varies with the stress sensitivity. For a particular coalbed gas well, there is an optimum bottom-hole pressure value under where the water yield is maximum. The greater the stress sensitivity coefficient is, the less water yield is. When the stress sensitivity coefficient is greater than 1, there is an invalid descending pressure section, and the greater the stress sensitivity coefficient is, the longer the invalid descending pressure section is. With the increase of the permeability and the wellbore radius, the daily water yield rate increases and the higher of the permeability and the longer of the radius of the wellbore is, the higher the efficiency of fracturing fluid flowback, and the larger the pressure drop zone is. While the daily water yield decreases with the increase of skin coefficient.