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发耳矿区煤储层敏感性对煤层气排采影响及控制对策

Influence of coal reservoir sensitivity on CBM drainage and control strategy in Faer Mining Area

  • 摘要: 为了降低煤储层敏感性对排采的影响,研究发耳矿区煤储层的敏感性特征,以期为该地区的煤层气井排采方法和控制策略提供参考,通过对发耳矿区16号煤层进行敏感性试验,测试不同流速下的渗透率、不同净应力下的渗透率及不同累计注入倍数下的渗透率,研究了煤层的流速敏感性、应力敏感性及水敏感性伤害特征,分析煤层气井的临界产水量、应力敏感临界值及煤储层敏感性伤害对排采的影响,提出发耳矿区煤层气井降低应力敏感伤害的控制策略。研究结果表明:发耳矿区16号煤层为中等偏强的速敏损害储层、强应力敏感损害储层、中等偏强的水敏损害储层;为降低煤层气井产水初期的速敏伤害,应降低煤层流体流速,试验煤层的产水量应不超过2.46 m3/d;试验煤层的应力敏感临界值为7 MPa,当净应力值小于临界值时,煤层对应力变化的敏感性较强,随净应力值的增大,煤层渗透率快速下降;煤层气井产出水的矿化度越高,产出水对煤层的水敏性伤害呈快速增大的趋势,随着矿化度的降低,对煤层水敏性伤害增大的趋势逐渐减弱,研究结果和认识,对于该地区煤层气井降低压裂、排采过程中煤储层敏感性伤害具有重要指导意义。

     

    Abstract: In order to reduce the impact of coal reservoir sensitivity on coal mining, studies were carried out to investigate the sensitivity characteristics of coal seam in Faer Mining Area, an attempt to provide guidance for controlling coal bed methane drainage in the area.Sensitivity experiments were carried out to No.16 coal seam in the Faer Mining Are, which studied the permeability under different flow rates, different net stresses and with different cumulative injection multiples,the flow velocity sensitivity,stress sensitivity and water sensitivity damage characteristics of coal reservoir were studied,and analysis was performed to assess the impact from the critical water yield,stress sensitive critical value and sensitivity damage of coal seam on drainage mining,a control strategy for reducing stress sensitive damage in coalbed methane well of Faer Mining Area was proposed at the end.The results indicate that coal reservoir of the No.16 coal seam in Faer Mining Area is subject to moderately strong speed-sensitive damage,strong stress-sensitive damage,and moderately strong water-sensitive damage.In order to reduce the speed-sensitive damage to CBM wells at the initial stage of water production,the fluid velocity of coal seam should be kept low,with the water production of experimental coal seam not exceeding 2.46 m3/d.The stress sensitive critical value of the experimental coal seam is 7 MPa, when the net stress value is lower than the critical value,the coal seam is highly sensitive to stress changes,and the permeability of the coal seam decreases rapidly as the net stress value increases;the water-sensitive harm from the produced water on the coal seam increase at an accelerating rate with higher salinity of the produced water in CBM wells,and as the sa-linity decreases, the water-sensitive harm to the coal seam tends to decrease gradually.This study would provide important guidance for reducing fracture and sensitive damages to CBM wells throughout mining process.

     

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