渝东南渝页1井页岩气吸附能力及其主控因素

Adsorption Capacity of Shale Gas and Controlling Factors from the Well Yuye 1 at the Southeast of Chongqing

页岩气是一种重要的非常规天然气,其中大部分的天然气以吸附态存在。为了探讨渝东南地区下志留统龙马溪组黑色页岩的天然气吸附能力和主控因素,对渝页1井的岩芯进行了系统地采样,并做了孔隙结构和体积、矿物组成、有机质含量、成熟度测定和等温吸附实验。实验测试结果显示,饱和吸附量VL在1.25～3.90 m3/t,平均为2.17 m3/t;Langmuir压力常数pL在1.90～9.48 MPa,平均为3.69 MPa。饱和吸附量与微孔体积具有负相关,与中孔体积和宏孔体积具有正相关。粘土矿物通过对微孔和中孔体积的控制来影响页岩的吸附能力,石英含量通过对宏孔体积的控制来影响页岩吸附能力。有机碳含量对页岩的吸附能力主要由其较发育的宏孔隙控制,另外,还可能有其他方面的影响因素,比如有机碳表面的亲油性对气态烃较强的吸附能力以及气态烃在无定形和无结构基质沥青体中的溶解作用等。当Ro>2.0%时,饱和吸附量与Ro呈正相关,这可能与高成熟有机质中纳米级显微裂缝的发育导致宏孔体积的增加有关。

Gas shales is important unconventional gas reservoirs in which much of the gas is stored in the adsorbed state. In order to study adsorption capacity of natural gas and controlling factors of Longmaxi Formation in Lower Silurian from Well Yuye 1 at the southeast of Chongqing, a series of measurements including pore structure and volume, mineral composition, total organic carbon （TOC）, vitrinite reflectivity（R0） and adsorption isotherms are made. The results show that saturated adsorption VL are 1.25-3.90 m^3/t with an average of 2.17 m^3/t; Langmuir pressure constant PL are 1.90-9.48 MPa with an average of 3.69 MPa. Saturation adsorption capacity has a negative correlation with micropores volume, and a positive correlation with mesopores volume and maeropores volume. The clay mineral influence adsorption capacity of the shale through controlling micropore and mesopore volume, while quartz through controlling macropore volumes. Organic carbon content on the adsorption capacity of shale may be mainly due to its control over development of the macropores. In addition, the strong adsorption for gaseous hydrocarbons due to characteristics of the surface hydrophobicity and dissolution of gaseous hydrocarbons in the amorphous structure of asphalt have a certain impact. When R0〉 2.0%, there is a positive correlation between saturation adsorption capacity and R0, which may be related with the development of microfractures in the organic matter with high maturity resulting in the increase of macropore volume.