准南区块煤层气井排采阶段储层伤害及其控制

    Coalbed methane reservoir damage and its control in the drainage stage of a block in southern Junggar Basin

    • 摘要: 针对准南区块煤层气低产井在排采阶段的储层伤害,结合室内实验,系统分析了区内典型煤层气井的排采情况,探讨了煤层气井排采阶段储层伤害类型及其防控方法。结果表明:研究区排采阶段储层伤害类型主要包括应力敏感、速敏和水锁伤害,而煤储层力学强度低、压裂液不当、排采强度过高是造成这些伤害的重要原因;在排采阶段,基于“连续、缓慢、稳定”的原则,增大压降漏斗,并保持流体流速在微粒启动流速之下,有助于3类储层伤害的防治;在储层改造阶段,采用低表面张力、强润湿性的低伤害压裂液,能够促使微粒快速沉降、积聚,并且显著降低孔隙毛管压力,进而抑制储层速敏与水锁伤害;同时,通过围岩改造煤储层,有助于减缓应力敏感伤害。

       

      Abstract: Aiming at the reservoir damage of low-yield coalbed methane wells in Junggar Basin block during the drainage stage, in this paper, the drainage situation of typical coalbed methane wells in the block is systematically analyzed and reservoir damage types and prevention and control methods of coalbed methane wells in the drainage stage are discussed. The results show that the main types of reservoir damage at the drainage stage in the study area include stress sensitivity, velocity sensitivity and water lock damage. The low mechanical strength of coal reservoirs, improper fracturing fluid, and high drainage intensity are the important reasons for these damages. During the drainage stage of CBM wells, drainage is carried out according to the “continuous, slow and stable” guidelines, increasing the expansion range of the pressure drop funnel and keeping the fluid flow rate below the particle start flow rate will help prevent the three types of reservoir damage. In addition, the use of low-damage fracturing fluid with low surface tension and strong wettability can promote the rapid sedimentation and aggregation of particles. The pore capillary pressure is significantly reduced in the reservoir in the reconstruction stage, thereby inhibiting reservoir velocity sensitivity and water blocking damage. Meanwhile, the coal reservoir is retrofitted by surrounding rock, which helps to reduce the impact of stress-sensitive damage on the production of coalbed methane.

       

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