高煤级煤储层煤层气产能“瓶颈”问题研究

基于山西沁水盆地高煤级煤储层宏观裂隙、显微裂隙的连续观测,孔隙的系统测量,结合应力渗透率、气-水相对渗透率、吸附膨胀等实验成果,分析了高煤级煤储层三级渗流特征,探讨了有效应力和煤基质收缩对高煤级煤储层渗透率的耦合作用,系统揭示了在地面排水降压开发煤层气的过程中,高煤级煤储层初期产气量高,数月后急剧衰减之“瓶颈”现象,找出了造成高煤级煤储层产气缺陷的根本原因。鉴于高煤级煤储层物性的特殊性,指出了高煤级煤储层煤层气开发的技术和措施。

Study on the "Bottle-Neck" Problem of Coalbed Methane Productivity ofHigh-rank Coal Reservoirs

Based on continuous observations of the macrofractures and microfractures and systemic measurements of pores in coal reservoirs, combined with experimental results of stress permeability, methane - water relativepermeability and adsorption-swelling on high-rank coal reservoirs, this paper has analyzed the tertiary seepage characteristics of high-rank coal reservoirs, discussed the coupling effect of effective stress and coal matrix shrinkage on permeability of high-rank coal reservoirs, revealed the " bottle-neck" phenomenon that the productivity of coalbed methane (CBM)is high in the initial stages and attenuates rapidly after a few months in the course of development using the water drainage and pressure reduction methods, and found out the radical reason that leads to the reduction of methane recovery in high -rank coal reservoirs. Techniques and measures are suggested for developing CBM in high-rank coal reservoirs aiming at the particularity of physical properties of high-rank coal reservoirs.