沁南地区高煤阶煤储层流速敏感性及影响因素

流速敏感性评价实验结果是确定煤层气藏合理排采速度的重要依据,对煤层气开发具有重要意义。高煤阶煤储层的低孔低渗特征使煤储层速敏性评价不能仿照常规储层的液体实验方法,为此提出利用氮气评价高煤阶煤储层流速敏感性的新方法,并对沁南地区高煤阶样品进行测试。结果表明:沁南地区高煤阶煤储层速敏损害程度相对较弱,主要损害程度为无敏感、弱敏感和中等偏弱3种;高煤阶煤储层原始渗透率是控制煤储层速敏损害率的主控因素,煤储层渗透率越大,速敏损害率越高;煤岩中黏土矿物含量对煤储层速敏损害率的影响相对有限,速敏损害率主要与黏土矿物赋存方式有关,当黏土矿物主要赋存于裂隙中时,煤储层速敏损害率相对较大。 

Velocity sensitivity and its influencing factors of high-rank coal reservoirs in southern Qinshui basin

The result of sensitivity evaluation experiment for flow velocity of gas flowing through coal is used for determining a reasonable recovering rate of coal bed gas reservoir, which is of great significance for CBM development. Because of low porosity and low permeability of the high rank coal reservoir, the velocity sensitivity evaluation of the high-rank coal reservoir can not follow the liquid experimental methods of conventional reservoir. Therefore, this paper put forward a new method of sensitivity evaluation of high rank coal reservoir by using the nitrogen, and conducted the flow sensitivity test on samples of high rank coal in southern Qinshui basin. The results show that high rank coal has low velocity-sensitive damage rate in Southern Qinshui basin, the damage rate ranges mainly from non to weak and weak medium. Original permeability is the main control factors of velocity-sensitive damage for high rank coal reservoir, the higher the coal reservoir permeability, the higher the velocity-sensitive damage rate. The clay content in coal reservoir has limited influence on velocity sensitivity, the velocity-sensitive damage rate is mainly associated with the mode of occurrence of clay mineral in coal. When the clay minerals occur mainly in coal fracture, the velocity-sensitive damage rate is relatively large for high rank coal.