褐煤储层含气量计算

Gas content calculation of lignite reservoir

因我国褐煤中煤层气赋存特征认知程度较低,影响了较低煤级煤层气的开发,褐煤中含气量的研究显得尤为关键。基于此,文中对采自内蒙古海拉尔盆地4个褐煤H1,H2,H3,H4样品进行煤岩煤质分析,25℃平衡水等温吸附实验。计算埋深在400～2 000 m吸附气含量;模拟在储层温度、压力、矿化度、密度条件进行甲烷溶解度的测定结果表明甲烷溶解度随压力、温度的同时增加而增大(低于80℃),基于实验结果,计算了不同埋深(温度、压力)下褐煤储层的水溶气含量;测定4个褐煤样品孔隙度,根据马略特定律计算游离气含量。由吸附气、水溶气及游离气含量计算褐煤含气量。结果表明,埋深小于1 000 m的褐煤含气量随埋深增加而增大;埋深大于1 000m随埋深增加而减少。H1含气量较低,H2,H3,H4含气量较高,400～2 000 m埋深的褐煤含气量介于2.57～6.99 m3/t之间,且均随埋深增加而增大。含气量中吸附气、水溶气、游离气含量比例分别为78.7%,9.3%,12.0%.

The cognitive level of coalbed methane （CBM） occurrence characteristics in lignite reservoir is relatively low in China, and gas content research of lignite become more crucial as it affects the lower CBM development of lowrank coal. For those reasons, coal quality and petrology were tested, as well as methane isothermal adsorption experiments were performed on moistureequilibrated coals （H1, H2, H3, H4 ） from Hailaer Basin under 25 ~C. Based on the temperature negative effect, the adsorbed gas content was calculated. Water samples were collected from Hailar lignite coal seam and coal bed roof/floor. Geo chemical characteristics of the water samples including salinity, gas composition in the water and water density were determined. With physical simulation, methane solubility in the coal seam water was meas ured using balance liquid sampling method and the water soluble gas content was numerically simulated. On the basis of coal porosity test results, the free gas contents were computed by Mariotte equation. The results showed that ： at the depth from 400 to 2 000 m, coalbed methane content lied between 3.56 m3/ t and 4.63 m3/t, indicating a positive relationship with the depth.