高煤阶煤储层敏感性对煤层气井排采的影响
Influence of High-rank Coal Reservoir Sensitivity on Coalbed Methane Wells Production
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摘要: 为实现高煤阶煤储层煤层气井的高效开采,对高煤阶煤储层寺河3号煤层进行了流速敏感性和应力敏感性试验分析,并且结合现场工程,研究了高煤阶煤储层敏感性对煤层气井排采的影响。试验结果表明,高煤阶煤储层具有流速敏感性,流速敏感性损害最严重时渗透率降为初始值的50%,换向驱替时渗透率也降低,最小降低为初始值的62.1%;黏土含量越高的储层,渗透率的降低幅度也越大。高煤阶煤储层具有强应力敏感性,而且存在明显不可逆性;净围压从2 MPa升高到5 MPa,渗透率降低为初始渗透率的20%~50%,升压后再降压,渗透率不能恢复到初始水平,不可逆损害率最大超过50%;渗透率越低的储层,应力敏感性越强。煤层气井的排采,尤其在排采初期,应遵循连续、缓慢、稳定的原则。Abstract: In order to realize the efficient exploitation of coalbed methane in high- rank coal reservoir, the velocity sensitivity and stress sensitivity of Sihe No. 3 co al seam were experimented and analyzed. Based on the engineering, the influence of high- rank coal reservoir sensitivity on coalbed methane wells production was ana lyzed. The experimental results showed that, high- rank coal reservoir had the feature of velocity sensitivity, the permeability could reduce to 50% of initial value to the maximum extent, directional flooding would also reduce permeabilit, the minimum reduce to 62. 1% of initial value, the higher the clay content of the reservoir was, the lower the permeability decreasing amplitude would be. The high- rank coal reservoir had a strong stress sensitivity and existed apparent irreversibility; when the net con fining pressure increased from 2 MPa to 5 MPa, the permeability decreased as 20% ~ 50% of the initial permeability, after the buck boost, the permeability could not res ume to the initial level, the maximum of irreversible damage rate was more than 50%,the lower the reservoir permeability was, the stronger the stress sensitivity would be. The coalbed methane wells production process should follow continuous, slow and stable principle, especially in initial stage.
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