沁水盆地高煤阶煤吸附时间主要影响因素分析

摘要

为了达到更好的评价煤储层开发潜力的目的,对直接关系到煤储层流体可动性的煤层吸附时间进行了研究,通过对沁水盆地寿阳和柿庄区块3、15号煤层的煤岩进行测试,分析了高煤阶煤吸附时间的特征,讨论了镜质体最大反射率(Rmax)、煤质和气体组分等因素对吸附时间的影响.研究表明:煤阶,即Rmax是影响煤层吸附时间的主要因素,镜质组/惰质组比值、气体组分Φ(CO2)/Φ(CH4)和Φ(CH4)/Φ(N2)为次要因素,单一的显微组分(镜质组、惰质组)和灰分对吸附时间的影响不大.对高煤阶煤岩而言,当Rmax＜2.9％时,吸附时间随Rmax的增大而增大;当Rmax＞2.9％时,吸附时间随Rmax的增大而减小,主要是由于随煤岩演化程度增高,煤岩平衡水含量与比表面积综合作用引起煤岩孔隙度、微孔隙结构及比表面积下降,导致煤岩吸附能力下降.此外,受各显微组分吸附能力差异、各类气体吸附特点差异及煤层中气体浓度差等因素的影响,镜质组/惰质组、Φ(CO2)/Φ(CH4)和Φ(CH4)/Φ(N2)均与吸附时间表现为负向包络关系.%In order to reach a target to well evaluate the development potential of the coal reservoir,a study was conducted on the seam adsorption time directly related to the fluid movability of the coal reservoir.With the measurements conducted on the coal and rock of No.3 seam and No.5 seam in Shouyang Block and Shouyang Block of Qinshui Basin,the paper analyzed the features of the high rank coal adsorption time and discussed the max reflectivity (Rmax) of the vitrinite,coal quality,gas composition and other factors affected to the adsorption time.The study showed that the coal rank (based on the R as the basis) would be the major factor affected to the adsorption time of the seam,the vitrinite/inertinite ratio and the gas composition Φ(CO2)/Φ(CH4) and Φ(CH4)/Φ(N2) would be the secondary factors and the monomaceral (vitrinite and inertinite) and ash content would be less affected to the adsorption time.In the case of the high rank coal,when the Rmax was less than 2.9％,the adsorption time would be increased with the R increased.When the Rmax was higher than 2.9％,the adsorption time would be decreased with the Rmax increased and the adsorption capacity decreased of the coal and rock were caused mainly due to the coal and rock evolution degree increased,the equilibrium moisture content of the coal and rock and the comprehensive role of the specific surface area caused the reductions of the coal and rock porosity,micro pore structure and the specific surface area.In addition,affected by the adsorption capacity differences of each maceral,the adsorption feature differences of each type gas,the gas concentration difference in the seam and other factors.The vitrinite/inertinite,Φ (CO2)/Φ (CH4) and Φ (CH4)/Φ (N2) would all have the negative envelope relationship with the adsorption time.