沁水盆地南部高阶煤储层气水产出过程分析

Analysis on gas and water output process of high rank coal reservoir in Southern Qinshui Basin

为了探讨煤层气井排采控制指标,以沁水盆地南部高阶煤为研究对象,基于气-水相对渗透率试验和渗流物理仿真模拟,探讨了宏观与微观渗流网络中气-水相对渗透率变化机制,并进一步阐述了煤储层气、水产出过程。结果表明,宏观裂隙气-水相渗曲线分为气-水同流区和纯气流动区;微观孔裂隙气-水相渗曲线分为单相水流区、气-水同流区和纯气流动区。煤储层流体产出过程可归纳为开发初期宏观裂隙中水带气的过程,微观孔裂隙中水的单相流动阶段,气相饱和度上升阶段,气驱水的过程,气的单相流动阶段,以及宏观裂隙中气的单相流动阶段。其中,微观孔裂隙中气驱水的过程是高产气井稳定产液的关键,而游离气产出则是煤层压力整体下降的基础。

In order to study the control indicators for coalbed methane（ CBM） production,take the high rank coal at Southern Qinshui Basin as the study object,based on the gas and water relative permeability test and the seepage physical similar simulation,the paper discussed the variation mechanism of the gas and water relative permeability in the micro-macro seepage network and further stated the gas and water output process of the seam. The results showed that the macro crack gas and water relative permeability curve could be divided into a gas and water co-flow area and a pure gas flow area. The gas and water seepage curve of the micro cracks could be divided into a single phase water flow area,a gas and water co-flow area and a pure gas flow area. The liquid output process of the coal servitor could be concluded as a water with gas process in the initial macro cracking development,single phase flow stage in the micro pore fissure,rising stage of the gas phase saturation,gas drive water process,single phase flow stage of the gas and the single phase flow stage of the gas in the macro cracks. Among them,the gas drive water process in the micro pore fissure would be the key to the stable liquid production in the high gas production well and the output of the free gas would be the base to reduce the pressure of the seam wholly.