华北地区煤储层渗透率的外在影响因素分析

Analysis on the External Factors of Affecting Permeability of Coal Reservoir in North China

通过对华北地区 16个目标区 6 0层次的试井渗透率的统计发现 ,在我国华北地区复杂的地质背景下 ,原地应力等外在因素对于煤储层渗透率的影响是很显著的。研究表明 ,煤层渗透率的决定因素是原地应力 ,煤层埋藏深度对渗透率的影响是第二位的。渗透率随地应力增大而减小 ;渗透率与埋藏深度之间的关系受原地应力的影响。只有区别不同应力环境 ,才能分析渗透率随深度变化的趋势。通过分析煤储层渗透率的外在影响因素 ,对于评价与预测煤层气的解吸特征 ,为下一步做好压裂设计 ,达到增产效果起到了积极的作用。

Coal reservoir consists of coal matrix pore and natural fracture system so that is different with normal reservoir. Coal matrix pore is small so it can only exist as main storage space for coalbed gas, while the permeability of natural fracture system is favorable and can be main passage for seepage flow migration of fluid inside coal, including coalbed gas. Based on well testing permeability for 60 intervals in 16 target zones in North China, it is found that under the complex geological background in our country, the external factors such as the original ground stress has apparent effect on coal reservoir permeability. The research shows that original ground stress is the control factor for coal reservoir permeability, and burial depth is the second,permeability decreases as ground stress increases; the relationship between permeability and burial depth is considerably affected by original ground stress. The permeability variation with depth can only be analyzed under different stress environment. To analyze the external factors that affect permeability of coal reservoir will be significant for evaluating an estimating coalbed gas desorption features, designing future fracturing ,and improving production.