沁水盆地柿庄地区煤粉发育特征及其对产出的影响

    Development characteristics of coal fines and its influence on output in Shizhuang Coalbed Methane Block of Qinshui Basin

    • 摘要: 煤粉发育和产出特征对指导煤层气勘探开发具有重要的意义。以沁水盆地柿庄地区为研究对象,收集了钻井取心、测井信息、排采数据和煤层气井产煤粉样品等,基于测井解释、激光粒度测试和煤粉质量分数监测等方法,系统分析了煤粉发育特征及其对产出的影响。研究结果表明:研究区原生煤粉可划分为煤粉发育复杂区、煤层底部发育煤粉区、煤粉不发育区、煤粉较少发育区和煤层顶底发育煤粉区5类地区,产出煤粉粒径分布在0.4~3300 μm,质量分数集中在0~0.5;煤粉发育特征影响着煤层气井初次产粉时间,其中原生煤粉发育复杂区一般在见气之前初次产煤粉,原生煤粉底部发育区和原生煤粉顶底发育区初次产粉时间规律性较差,原生煤粉不发育区和原生煤粉较少发育区一般在见气之后初次产煤粉;排水降压阶段受井筒附近煤粉发育特征的影响,产出煤粉以中、粗颗粒煤粉为主,煤粉颗粒大,质量分数不高;提产放气阶段受排采强度和煤粉发育特征的影响,以中、细颗粒煤粉为主,煤粉颗粒较小,煤粉质量分数高且波动较大;稳定产气阶段主要产出远端裂缝中的原生煤粉或压裂工程产生的次生煤粉,煤粉颗粒更小,质量分数相对较小且波动小;产气衰减阶段的煤粉颗粒最小,煤粉产出量少。

       

      Abstract: Identifying the characteristics of coal fine development and production can guide the exploration and development of coalbed methane (CBM). In this paper, drilling coring, logging information, drainage and production data, and coal fine samples from CBM wells were collected in Shizhuang area, Qinshui Basin, China. Based on logging interpretation, laser particle size analysis and mass fraction testing, the development characteristics of coal fine and its impact on production were systematically analyzed. The results show that the primary coal fine in the study area can be divided into five areas: complex coal fine development, coal fine at the bottom of the coal seam, no coal fine, less coal fine, and coal fine at the top and bottom of the coal seam. The output coal fine particle size distribution ranges from 0.4 μm to 3 300 μm, and the concentrated coal fine mass fraction ranges from 0 to 0.5. The development characteristics of coal fine affect the initial pulverized production time of CBM wells. The complex area generally produces coal fine for the first time before the occurrence of gas. The undeveloped areas and less developed areas generally produce coal fine for the first time after the occurrence of gas. Affected by the development of coal fine near the wellbore, the coal fine produced in the drainage and depressurization stage is mainly composed of medium and coarse particles, and the coal fine mass fraction is not high. Affected by the drainage intensity and the development characteristics of coal fine, the coal fine produced in the production and deflation stage is dominated by medium and fine particles, and the coal fine mass fraction is high and fluctuates greatly. In the stable gas production stage, CBM wells mainly produce primary coal fine and secondary coal fine produced by fracturing engineering in distal fractures. The coal fine particles and the mass fraction fluctuation are small. The output of coal fine in the gas production decay stage is small.

       

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