Influence of coal structure and macrolithotype of coal on coal adsorption and desorption of gas
ZHAO Fangyu , DENG Ze , WANG Haichao , WANG Ze , SUN Pichen, YANG Shengbo
新疆中亚造山带大陆动力学与成矿预测自治区重点实验室新疆大学 地质与矿业工程学院新疆大学 煤层气工程技术研究中心中国石油天然气集团有限公司非常规油气重点实验室
为研究高阶煤中煤体结构和宏观煤岩类型对煤体吸附、解吸的影响,收集了沁水盆地南部 3 号煤层 55 口煤层气井的 79 个煤岩样品的煤岩、煤质、等温吸附及解吸资料,对比研究了相同宏观 煤岩类型、不同煤体结构煤样和相同煤体结构、不同宏观煤岩类型煤样的兰氏体积(VL)、兰氏压力 (PL)、解吸率和解吸速率等的变化规律,探讨了煤体结构和宏观煤岩类型对煤体吸附、解吸的影响 机理。研究结果表明:研究区煤样的 VL 平均为 37.00 m3 /t,其中 86.61% 煤样 VL 分布在 33.00~41.00 m3 /t, PL 平均为 2.82 MPa,其中 82.28% 煤样 PL 分布在 2.30~3.30 MPa;碎裂煤的吸附、解吸能力均优于原 生结构煤,由构造破坏引起的孔隙连通性的差异是导致原生结构煤和碎裂煤解吸、吸附特征差异的 根本原因;原生结构煤与碎裂煤的孔裂隙发育程度不同,碎裂煤因孔隙更发育导致其破碎后的甲烷 放散效果好于原生结构煤;煤吸附甲烷时表面自由能降低值规律为糜棱煤>碎粒煤>碎裂煤>原生结构 煤,反映了不同煤体结构煤吸附甲烷能力的差异;3 种宏观煤岩类型煤的吸附能力和解吸能力均表现 为光亮煤>半亮煤>半暗煤,一方面是由煤的比表面积大致按照光亮煤、半亮煤和半暗煤的顺序逐渐 减小反映的煤基质表面吸附点位差异所致,另一方面是由于镜煤与暗煤中镜质组和惰质组含量的差 异所引起。研究旨在进一步揭示高阶煤储层煤层气赋存、产出机理,为煤层气有利区及目标层位优 选提供依据。
In order to study the influence of coal body structure and macrolithotype of coal in high rank coal on coal body adsorption and desorption, The data of coal petrography, coal quality, isothermal adsorption and desorption of 79 coal rock samples from 55 coal-bed methane wells in No.3 Coal Seam in the south of Qinshui Basin were collected, and the change laws in the Langmuir volume (VL), Langmuir pressure (PL), desorption rate of coal samples with the same macrolithotype of coal, different coal body structures and the same coal body structure, different macrolithotype of coal of coal samples, were discussed in the influential mechanisms of coal body structure and macrolithotype of coal on coal body adsorption and desorption. The results show that the average VL of coal samples in the study area is 37.00 m3 /t, of which 86.61% is distributed in 33.00—41.00 m3 /t, and the average PL is 2.82 MPa, of which 82.28% is distributed in 2.30~3.30 MPa. The adsorption and desorption capacities of fractured coal are better than those of primary structure coal and the difference of pore connectivity caused by structural destruction is the fundamental reason for the difference of desorption and adsorption characteristics between primary structural coal and fractured coal; The development degree of pores and fissures of primary structure coal is different from that of fractured coal. The methane emission effect of fractured coal is better than that of primary structure coal because of more developed pores. The decreasing rule of surface free energy of coal for methane adsorption is the mylonitic coal > granulitic coal > fractured coal > primary structure coal, which reflects the difference of methane adsorption capacity of coal with different coal structure; the adsorption and desorption capabilities of the three types of macro coals are bright coal > semibright coal > semidull coal. On the one hand, the specific surface area of coal decreases roughly in the order of bright coal, semibright coal, and semidull coal, which reflects the difference in adsorption sites on the surface of the coal matrix. On the other hand, it is caused by the difference of vitrinite and inertinite content between vitrain and durain. The purpose of this study is to further reveal the occurrence and production mechanism of CBM in high-rank coal reservoirs, and to provide a basis for the optimization of CBM favorable areas and target horizons
coalbed methane; coal body structure; macrolithotype of coal; adsorption; desorption
主办单位:煤炭科学研究总院有限公司 中国煤炭学会学术期刊工作委员会