摘要
运用直接解吸法和间接法计算柳坪171井延长组长7段、长8段、长9段页岩游离气含量、吸附气含量和总气量，结合分析延长组页岩岩矿组分、有机地球化学特征、孔隙结构与孔隙体积，确定了延长组陆相页岩含气量及主控因素，并对含气量与主控因素之间关系做了定性及半定量研究。结果表明：延长组页岩含气量以吸附气量为主，其中长7段页岩含气量为3．71～6．26m^2／t，游离气百分比为22．53％～35．29％，平均为29．22％；长8段页岩含气量为3．68～5．19m^2／t，游离气占总含气量的24．43％；长9段页岩含气量最高，为5．57～7．80m^2／t，游离气含量比例为31．64％。随着有机碳含量的增加，可供天然气吸附的比表面增大，页岩吸附气量也增大，同时有机质成熟度的提高促进有机组分纳米级孔隙的产生，从而增加页岩气储集空间，因此有机碳含量、镜质体反射均与含气量呈正相关关系。与海相页岩不同，延长组陆相页岩石英主要来源于陆源碎屑，含气量与石英含量呈负相关关系。黏土矿物含量与含气量呈弱正相关，主要表现在伊蒙混层、伊利石对页岩气的吸附能力。含气量与微孔体积相关性不明显，与中孔和宏孔均具有正相关关系。
The direct desorption method and indirect method were used for calculating the free gas content, adsorbed gas content and total gas content of Chang 7 Shale,Chang 8 Shale and Chang 9 Shale in Liuping- 171 Well respectively. By analyzing the mineralogy, geochemical characteristics, pore structure and pore volume of Yanchang shale,the main controlling factors of gas content had been confirmed,which had been analyzed qualitatively or semi-quantitatively. The results show that, the gas content of Yanchang shale is dominated by adsorbed gas content. In particular, the gas content of Chang 7 shale is 3. 71-6.26m^3/t of which the free gas content is 22. 53%-35.29%,with an average of 29. 22%. The gas content of Chang 8 shale is 3.68-5.19 ma/t of which the free gas content is 24. 43%. The gas content of Chang 9 shale is 5.57- 7.80 m^3/t of which the free gas content is 31.64%. With the increase of organic carbon content,the specific surface area available for gas adsorption increases accordingly, therefore, the adsorbed gas content increases. The organic carbon content shows positive correlation with the total pore volume,moreover,high maturity promoted the development of organic nanopores which caused the increase of shale gas reservotr space. Hence, TOC and vitrinite reflectance show positive correlation with the gas content respectively. Dif- ferent from marine shale,the source of quartz in continental Yanchang shale is the detrital material of ter- rigenous origin,therefore, the quartz content is negatively correlated with gas content. The clay content has weak positive correlation with the gas content,which mainly manifested as the adsorption capacity of illite smectite mixed layer clay and illite for shale gas. The correlation between gas content and micropore volume is not obvious. While the motion state of methane molecules changed because of which the thermodynamic state changed,the macropore and mesopore with a greater pore size and pore throat are easier to be filled by methane molecules, therefore, the macropore and mesopore volume show positive correlation with the gas content.
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2014年第2期291-301,共11页
Natural Gas Geoscience
基金
国家科技重大专项专题(编号:2011ZX05018-001-002、2011ZX05009-002-205)
国家自然科学基金面上项目(编号:41272167、41002072、41372139、41072098)联合资助
关键词
陆相页岩
延长组
鄂尔多斯盆地
柳坪171井
含气量
主控因素
Continental shale
Yanchang Formation
Ordos Basin
Liuping-171 well
Gas content
Controlling factors
